The advent of modular implants aims to minimise morbidity associated with revision of hemiarthroplasty or total shoulder arthroplasty (TSA) to reverse shoulder arthroplasty (RSR) by allowing retention of the humeral stem. This systematic review aimed to summarise outcomes following its use and reasons why modular humeral stems may be revised.

A systematic review of Pubmed, Medline and EMBASE was performed according to PRISMA guidelines of all patients undergoing revision of a modular hemiarthroplasty or TSA to RSR. Primary implants, glenoid revisions, surgical technique and opinion based reports were excluded. Collected data included demographics, outcomes and incidence of complications.

277 patients were included, with a mean age of 69.8 years (44-91) and 119 being female. Revisions were performed an average of 30 months (6-147) after the index procedure, with the most common reason for revision being cuff failure in 57 patients. 165 patients underwent modular conversion and 112 underwent stem revision. Of those that underwent humeral stem revision, 18 had the stem too proximal, in 15 the stem was loose, 10 was due to infection and 1 stem had significant retroversion. After a mean follow up of 37.6 months (12-91), the Constant score improved from a mean of 21.8 to 48.7. Stem revision was associated with a higher complication rate (OR 3.13, 95% CI 1.82-5.39).

The increased use of modular stems has reduced stem revision, however 40% of these implants still require revision due to intra-operative findings. Further large volume comparative studies between revised and maintained humeral stems post revision of modular implants can adequately inform implant innovation to further improve the stem revision rate.

Patellofemoral instability (PFI) is a common cause of knee pain and disability in the paediatric population. Patella alta, lateralised tibial tubercle, medial patellofemoral ligament (MPFL) deficiency, genu valgum and trochlear dysplasia are well known risk factors.

A prospective database was created including patients referred through our physiotherapy pathway following first-time patella dislocation. Patella alta and lateralisation of the tibial tuberosity was treated with a Fulkerson-type tibial tubercle osteotomy(TTO). Medial patellofemoral ligament was reconstructed using quads tendon autograft pull-down technique. A modified Sheffield protocol was used postoperatively allowing weightbearing in a hinged knee brace.

Forty patients were identified with 8 patients having bilateral presentations. Male to female ratio was 12:28 with an age range of 4–17 years. Eight patients had congenital PFI, five patients acquired PFI through traumatic patella dislocation and twenty-seven patients developed PFI from recurrent dislocations. Structural abnormalities were found in 38(95%) of patients. Patella alta (Caton-Deschamps index >1.2) was identified in 19(47%) patients, genu valgum in 12(30%) patients, increased tibial tubercle-trochlear groove distance(TT-TG>20mm) was present in 9(22.5%) patients and persistent femoral anteversion(> 20 deg) in 7(17%) patients.

Eight patients were treated with TTO and MPFL reconstruction, three patients with MPFL reconstruction alone and five patients had guided growth for genu valgum correction. Ten patients are awaiting surgery. No postoperative patients had recurrence of PFI at their latest follow up.

PFI is a common problem in the adolescent paediatric population with identifiable structural abnormalities. Correcting structural pathology with surgery leads to predictable and safe outcomes.

Traditionally, sports Injuries have been sub-optimally managed through Emergency Departments (ED) in the public health system due to a lack of adequate referral processes. Fractures are ruled out through plain radiographs followed by a reactive process involving patient initiated further follow up and investigation. Consequently, significant soft tissue and chondral injuries can go undiagnosed during periods in which early intervention can significantly affect natural progression. The purpose of this quality improvement project was to assess the efficacy of an innovative Sports Injury Pathway introduced to detect and treat significant soft tissue injuries.

A Sports Injury Pathway was introduced at Fiona Stanley Hospital (WA, Australia) in April 2019 as a collaboration between the ED, Physiotherapy and Orthopaedic Departments. ED practitioners were advised to have a low threshold for referral, especially in the presence of a history of a twisting knee injury, shoulder dislocation or any suggestion of a hip tendon injury. All referrals were triaged by the Perth Sports Surgery Fellow with early follow-up in our Sports Trauma Clinics with additional investigations if required. A detailed database of all referrals was maintained, and relevant data was extracted for analysis over the first 3 years of this pathway.

570 patients were included in the final analysis. 54% of injuries occurred while playing sport, with AFL injuries constituting the most common contact-sports injury (13%). Advanced Scope Physiotherapists were the largest source of referrals (60%). A total of 460 MRI scans were eventually ordered comprising 81% of total referrals. Regarding Knee MRIs, 86% identified a significant structural injury with ACL injuries being the most common (33%) followed by isolated meniscal tears (16%) and multi-ligament knee injuries (11%). 95% of Shoulder MRI scans showed significant pathology. 39% of patients required surgical management, and of these 50% were performed within 3 months from injury.

The Fiona Stanley Hospital Sports Injury Pathway has demonstrated its clear value in successfully diagnosing and treating an important cohort of patients who present to our Emergency Department. This low threshold/streamlined referral pathway has found that the vast majority of these patients suffer significant structural injuries that may have been otherwise missed, while providing referring practitioners and patients access to prompt imaging and high-quality Orthopaedic sports trauma services. We recommend the implementation of a similar Sports Injury Pathway at all secondary and tertiary Orthopaedic Centres.

Hamstring grafts have been associated with reduced strength, donor site pain and muscle strains following Anterior Cruciate Ligament Reconstruction (ACLR). Traditional graft fixation methods required both semitendinosus and gracilis tendons to achieve a graft of sufficient length and diameter, but newer techniques allow for shorter, broad single tendon grafts.

This study seeks to compare the outcomes between Single Tendon (ST) and Dual Tendon (DT) ACLR, given there is no prospective randomised controlled trial (RCT) in the literature comparing outcomes between these options.

In this ongoing RCT: (ANZ Clinical Trials Registry ACTRN126200000927921) patients were recruited and randomised into either ST or DT groups. All anaesthetic and surgical techniques were uniform aside from graft technique and tibial fixation. 13 patients were excluded at surgery as their ST graft did not achieve a minimum 8mm diameter. 70 patients (34 ST, 36DT) have been assessed at 6 months, using PROMS including IKDC2000, Lysholm and Modified Cincinnati Knee, visual analog scale for pain frequency (VAS-F) and severity (VAS-S), dedicated donor site morbidity score, KT-1000 assessment, and isokinetic strength.

Graft diameters were significantly lesser in the ST group compared to the DT group (8.44mm/9.11mm mean difference [MD],-0.67mm; P<0.001). There was a significant and moderate effect in lower donor site morbidity in the ST group compared to the DT group (effect size [ES], 0.649; P = .01). No differences between groups were observed for knee laxity in the ACLR limb (P=0.362) or any of the patient-reported outcome measures (P>0.05). Between-group differences were observed for hamstrings strength LSI favouring the ST group, though these were small-to-moderate and non-significant (ES, 0.351; P = .147).

ST (versus DT) harvest results in significantly less donor site morbidity and this is the first prospective RCT to determine this. There were no differences between ST and DT hamstring ACLR were observed in PROMs, knee laxity and hamstring strength. Younger female patients tend to have inadequate single tendon size to produce a graft of sufficient diameter, and alternative techniques should be considered. Further endpoints include radiological analysis, longer term donor site morbidity, revision rates and return to sport and will continue to be presented in the future.

Aims

A number of anti-retroviral therapies (ART) have been implicated in potentially contributing to HIV-associated bone disease. The aim of this study was to evaluate the effect of combination ART on the fracture healing process.

This study aims to determine the lifetime risk of revision surgery after primary knee arthroplasty (KA).

The Scottish Arthroplasty Project dataset was utilised to identify all patients undergoing primary KA during the period 1998–2019. The cumulative incidence function for revision and death was calculated and adjusted analyses utilised cause-specific Cox regression modelling to determine the influence of patient-factors. The lifetime risk was calculated for patients aged between 45–99 years using multiple decrement lifetable methodology.

The lifetime risk of revision ranged between 32.7% (95% Confidence Interval (CI) 22.62–47.31) for patients aged 45–49 years and 0.63% (95%CI 0.1–4.5) for patients aged over 90 years. Adjusted analyses demonstrated the converse effect of age on revision (Hazard Ratio (HR) 0.5, 95%CI 0.5–0.6) and death (HR 3.5, 95%CI 3.4–3.7). Male sex was associated with increased risks of revision (HR 1.1, 95%CI 1.1–1.2) and death (HR 1.4, 95%CI 1.3–1.4). Patients with inflammatory arthropathy had a higher risk of death (HR 1.7, 95%CI 1.7–1.8), but were less likely to be revised (HR 0.85, 95%CI 0.74–0.98) than those treated for osteoarthritis. Patients with greater number of comorbidities and greater levels of socio-economic deprivation were at increased risk of death, but neither increased the risk of revision.

The lifetime risk of revision knee arthroplasty varies depending on patient sex, age at surgery and underlying diagnosis. Patients aged between 45 and 49 years have a one in three probability of revision surgery within their lifetime. Conversely, patients aged 90 years or over were very unlikely to experience revision.

Staphylococcus aureus is responsible for 60–70% infections of surgical implants and prostheses in Orthopaedic surgery, costing the NHS £120–200 million per annum. Its ability to develop resistance or tolerance to a diverse range of antimicrobial compounds, threatens to halt routine elective implant surgery. One strategy to overcome this problem is to look beyond traditional antimicrobial drug therapies and investigate other treatment modalities. Biophysical modalities, such as ultrasound, are poorly explored, but preliminary work has shown potential benefit, especially when combined with existing antibiotics.

Using a methicillin-sensitive S. aureus reference strain and the dissolvable bead assay, biofilms were challenged by a low-intensity ultrasound (1.5MHz, 30mW/cm2, pulse duration 200µs/1KHz) for 20 minutes and gentamicin. The outcome measures were colony-forming units/mL (CFU/mL) and the minimum biofilm eradication concentration (MBEC) of gentamicin. The mean number of S. aureus within control biofilms was 1.04 × 109 CFU/mL. There was no clinically or statistically significant (p=0.531) reduction in viable S. aureus following ultrasound therapy alone. The MBEC of gentamicin for this S. aureus strain was 256 mg/L. The MBEC of gentamicin with the addition of ultrasound was 64mg/L. Further studies confirmed that the mechanism of action was due to incomplete disruption of the extracellular matrix with subsequent metabolic stimulation of the dormant biofilm-associated bacteria due to increased nutrient availability and oxygen tension.

Low intensity pulsed ultrasound was associated with a 4-fold reduction in the effective biofilm eradication concentration of gentamicin; bringing the MBEC of gentamicin to within clinically achievable concentrations.

The first three months following Total Knee Arthroplasty (TKA) provide an early window into a patient's functional outcomes, with the change of function in this time yielding valuable insight.

20 patients due to undergo primary TKA were recruited to the study. Data were recorded at three time points; pre-assessment clinic (PAC) before the operation, 6-weeks-post-operation (6WKs), at 12-weeks-post-operation (12WKs). Functional activity levels were monitored during early post-operative recovery for changes in early functional outcome, and allowed a comparison of metrics at each time point. This included direct functional testing of power output, timed functional performance in clinic, patient reported outcome measures, and multiday activity monitoring devices. Maximal power output symmetry (Power) was similar at 6WKs vs PAC (p = 0.37). At 12WKs, it had increased (p < 0.05). Timed functional performance (Performance) remained similar across all three time points (p = 0.27). Patient reported activities of daily living (ADL) performance significantly increased at 6WKs vs PAC (p < 0.05). At 12WKs, it remained similar (p = 0.10). Patient daily step count significantly decreased at 6WKs vs PAC (p < 0.05). By 12WKs, this had increased to similar levels to PAC (p = 0.30). Within the functional outcome measures, strong post-operative correlations were observed between Power and Performance (r = 0.62), Power and ADL (r = 0.49), and Performance and ADL (r = 0.61). Despite reduced measured step count and similar functional performance, patients report improved ADL at 6WKs. When symmetrical power output and measured step count have improved at 12WKs, patients report similar ADL to that at 6WKs. Multiple measures are required to get a full picture, however this highlights the different aspects measured by different tools.

Aim

The aim of this study was to determine whether the absence of periosteal reaction on plain radiographs was predictive of exchange nail failure in lower limb diaphyseal fracture non-unions.

Nasal carriers of methicillin sensitive Staphylococcus aureus (MSSA) have an increased risk for health-care associated infections. There is currently no national screening policy for the detection of MSSA in the UK. This study aimed to: evaluate the diagnostic performance of molecular and culture techniques in MSSA screening, determine the cause of any discrepancy between the diagnostic techniques, and model the potential effect of different diagnostic techniques on MSSA detection in orthopaedic patients. Paired nasal swabs for PCR assay and culture of S. aureus were collected from a study population of 273 orthopaedic outpatients due to undergo joint replacement surgery.

The prevalence of MSSA nasal colonisation was found to be between 22.4–35.6%. The current standard direct culturing methods for detecting S. aureus significantly underestimated the prevalence (p=0.005), failing to identify its presence in ∼1/3 of patients undergoing joint replacement surgery.

Modelling these results to national surveillance data, it was estimated that 800–1200 MSSA surgical site infections could be prevented annually in the UK by using alternative diagnostic methods to direct culture in pre-operative MSSA screening and eradication programmes.

Kirschner wires are commonly used in paediatric fractures, however, the requirement for removal and the possibility of pin site infection provides opportunity for the development of new techniques that eliminate these drawbacks. Bioabsorbable pins that remain in situ and allow definitive closure of skin at the time of insertion could provide such advantages.

Three concurrent studies were performed to assess the viability of bioabsorbable pins across the growth plate. (1) An epidemiological study to identify Kirschner wire infection rates. (2) A mechanical assessment of a bioabsorbable pin compared to Kirschner wires in a simulated supracondylar fracture. (3) The insertion of the implants across the physis of sheep to assess effects of the bioabsorbable implant on the growth plate via macroscopic, pathohistological and micro-CT analysis.

An infection rate of 8.4% was found, with a deep infection rate of 0.4%. Mechanically the pins demonstrated comparable resistance to extension forces (p=) but slightly inferior resistance to rotation (p=). The in vivo component showed that at 6 months: there was no leg length discrepancy (p=0.6), with micro-CT evidence of normal physeal growth without tethering, and comparable physeal width (p=0.3).

These studies combine to suggest that bioabsorbable pins do not represent a threat to the growth plate and may be considered for physeal fracture fixation.

The aims of the study were primarily to establish the overall success of debridement, antibiotics and implant retention (DAIR) in the management of infected total hip replacements (THRs) and secondarily to identify risk factors for failure.

Using a standardised and recognised study protocol (“Meta-analysis of observational studies in epidemiology (MOOSE) guidelines) a systematic review and meta-analysis of the literature was performed. The primary outcome measure of interest was treatment success. The search strategy and inclusion criteria plus quality assessment yielded 39 articles eligible for analysis.

The proportion of success from the literature following DAIR in the management of infected THRs is improving over time – the pooled mean proportion of success is 84.5% in studies from 2011–15. There was improved success with early debridement (75.7%) compared with delayed debridement (48.1%) (p=0.006).

The reported outcomes following DAIR appear to be improving with time. One of the most influential determinants of outcome is timing of debridement from onset of symptoms.

Surgeons should have a low threshold for investigating deep infection when presented with an acutely symptomatic THR and be aware of the updated reported outcomes associated with DAIR when considering management options.

Background

Radiological and clinical results of total shoulder arthroplasty are dependent upon ability to accurately measure and correct glenoid version. There are a variety of imaging modalities and computer-assisted reconstruction programmes that are employed with varying degrees of success. We have compared three freely available modalities: unformatted 2D CT; formatted 2D CT; and 3D CT reconstructions.

Obese patients undergoing total knee arthroplasty (TKA) face increased risks of complications such as joint infection and early revision. However, the influence of obesity on measures of patient function following TKA is poorly defined.

Knee arthroplasty outcome data for procedures carried out over an eight month period was extracted from a regional database in the UK. We analysed the impact of weight categories (BMI<30, BMI=30–34.9, and BMI≥35) on the Forgotten Joint Score – 12 (FJS-12) and Oxford Knee Score (OKS). Data was available preoperatively and 12 months postoperatively. Physical and mental health was assessed with the SF-12 one year after surgery.

Data from 256 patients were available. 49.6% had a BMI<30, 27.4% had a BMI 30–34.9 and 23.1% had a BMI≥35. Mean FJS-12 results at 1-year were 48.7 points for patients with a BMI<30, 40.7 points for patients with a BMI=30–34.9 and 34.0 points for patients with a BMI≥35. Effect sizes for change from baseline to 12-month post-op were 3.0 (Cohen's d) in patients with BMI<30 and d=2.2 in patients with BMI≥35. Mean OKS results at 1 year were 36.9 (BMI<30), 33.7 (BMI=30–34.9) and 32.0 (BMI≥35) respectively. Effect sizes for change from baseline to 12-month was d=2.1 (BMI<30) and d=1.9 (BMI≥35). Differences between BMI groups with regard to post-operative change were statistically significant for the FJS-12 (p=0.038) but not for the OKS (p=0.229).

This study highlights that outcome scores may differ in their ability to capture the impact of obesity on patient function following TKA. The FJS-12 showed significant differences in outcome based on patient obesity category, whereas the OKS did not detect between group differences.

Physical outcome following total knee arthroplasty is variable. Satellite cells are undifferentiated myogenic precursors considered to be muscle stem cells. We hypothesised that; the recovery of muscle strength and physical function following knee arthroplasty would be influenced by the underlying number of muscle satellite cells.

16 patients provided a distal quadriceps muscle biopsy at time of surgery. Satellite cells were identified with a primary mouse antibody for Pax7 – a cytoplasmic protein marker, and the myonuclei with DAPI. Positive cells were identified on the basis of immunofluorescent staining in association with nuclear material, and confirmed by position under the basal lamina. Patient function was assessed using a validated physical assessment protocol, the Aggregated Locomotor Function (ALF) score, muscle strength assessed using the leg extensor power-rig, and clinical outcome assessed with the Oxford Knee Score (OKS) pre-operatively and at 1 year post operatively.

Muscle satellite cell content varied amongst the patient group (Positive Staining Index 3.1 to 11.4). Satellite cell content at time of surgery correlated with change in outcomes between pre-operative and 1 year assessments in all assessed parameters (ALF, r = 0.31; muscle power, r = 49; OKS, r = 0.33). Regression analysis employing a forward stepwise selection technique employed satellite cell volume in models of pre-operative to 1 year change for all outcome parameters. Physical function (satellite cell content, patient age and pre-operative ALF score) adjusted R2 = 0.92; Muscle power (pre-operative power and satellite cell content) adjusted R2 = 0.38; Clinical outcome (pre-operative OKS and satellite cell content) adjusted R2 = 0.28.

Muscle satellite cell content influences recovery of muscle power and physical function following total knee arthroplasty. Importantly it is also associated with change in clinical scores; suggesting it to be a biomarker for patient outcomes.

3D imaging is commonly employed in the surgical planning and management of bony deformity. The advent of desktop 3D printing now allows rapid in-house production of specific anatomical models to facilitate surgical planning. The aim of this pilot study was to evaluate the feasibility of creating 3D printed models in a university hospital setting.

For requested cases of interest, CT DICOM images on the local NHS Picture Archive System were anonymised and transferred. Images were then segmented into 3D models of the bones, cleaned to remove artefacts, and orientated for printing with preservation of the regions of interest. The models were printed in polylactic acid (PLA), a biodegradable thermoplastic, on the CubeX Duo 3D printer.

PLA models were produced for 4 clinical cases; a complex forearm deformity as a result of malunited childhood fracture, a pelvic discontinuity with severe acetabular deficiency following explantation of an infected total hip replacement, a chronically dislocated radial head causing complex elbow deformity as a result of a severe skeletal dysplasia, and a preoperative model of a deficient proximal tibia as a result of a severe tibia fracture. The models materially influenced clinical decision making, surgical intervention planning and required equipment. In the case of forearm an articulating model was constructed allowing the site of impingement between radius and ulnar to be identified, an osteotomy was practiced on multiple models allowing elimination of the block to supination. This has not previously been described in literature. The acetabulum model allowed pre-contouring of a posterior column plate which was then sterilised and eliminated a time consuming intraoperative step.

While once specialist and expensive, in house 3D printing is now economically viable and a helpful tool in the management of complex patients.

Mesenchymal stem cells (MSCs) reside around blood vessels in all organs. This reservoir of progenitors can be ‘recruited’ in response to injury. The ability to manipulate stem cells therapeutically within injured tissue provides an attractive alternative to transplantation. Stem cells are regulated by neighbouring cells. We hypothesized that endothelial cells (ECs) influence MSC differentiation into bone and fat.

MSCs were sorted from fat using fluorescent activated sorting. Their capacity to differentiate into bone, fat and cartilage was used to confirm MSC phenotype. MSCs and ECs were cultured in two-dimensions (standard culture dishes) and three-dimensions (vascular networks suspended in gel). Cocultures were exposed to osteogenic and adipogenic media. The role of EC-released factors on MSC differentiation was determined using a system in which cells share media but do not contact. Wnt pathway modulators were used to investigate the role of Wnt signalling.

MSCs differentiated into bone, fat and cartilage. MSCs and ECs integrated in two- and three-dimensions. MSCs and ECs formed vessel-like structures in three-dimensions. When cultured with ECs, MSC differentiation to bone was accelerated while differentiation to fat was inhibited. This effect on osteogenesis was maintained when cells shared media but did not contact. Coculture with Wnt modulators confirmed that this effect is in part, mediated through Wnt signalling.

Our data suggest that ECs influence MSC differentiation. Therapeutic targeting of EC-MSCs signalling may enable manipulation of MSCs in vivo avoiding the need for cell transplantation. This could enable trauma and orthopaedic patients who have healthy resident stem cells to self-repair.

This study assessed whether patient satisfaction with their hospital stay influences the early outcome of total knee replacement (TKR).

During a five year period patients undergoing primary TKR at the study centre had prospectively outcome data recorded (n=2264). Patients with depression (p=0.04) and worse mental wellbeing (p<0.001), according to the short form (SF)-12, were more likely to be dissatisfied with their hospital stay. Decreasing level of satisfaction with their hospital stay was associated with a significantly worse post-operative OKS (p<0.001) and SF-12 score (p<0.001). Multivariable regression analysis confirmed that the patients perceived level of satisfaction with their hospital stay was an independent predictor of change in the OKS (p<0.001) and SF-12 score (p<0.001) after adjusting for confounding variables. Patient satisfaction with their TKR was significantly influenced by their hospital experience, decreasing from 96% in those with an excellent experience to 42% in those with a poor experience. Food, staff/care, and the hospital environment were the most frequent reasons of why patients rated their hospital experience as fair or poor.

A patient's perception of their inpatient hospital experience after surgery is an important modifiable predictor of early functional outcome and satisfaction with TKR.

The aim of this study was to identify risk factors for failure of exchange nailing for femoral diaphyseal fracture non-unions. The study cohort comprised 40 patients with femoral diaphyseal non-unions treated by exchange nailing. The main outcome measures were union, number of secondary fixation procedures required to achieve union and time to union. Univariate analysis and multiple regression were used to identify risk factors for failure to achieve union.

The mean age of the patients at exchange nail surgery was 37 years. The median time to exchange nailing from primary fixation was 8.4 months. Multiple causes for non-union were found in 14 (35.0%) cases, with infection present in 12 (30.0%) patients. Further exchange procedures were required in nine (22.5%) cases, one patient (2.5%) required the use of another fixation modality, to achieve union. Union was ultimately achieved in 35 (94.5%) patients. The median time to union was 9.4 months after the exchange nail procedure. Univariate analysis confirmed that cigarette smoking and infection were predictive of failure (p<0.05). Multi-regression analysis found that Gustilo-Anderson grade, presence of dead bone or a gap and infection were predictive of exchange nail failure (p <0.05).

Exchange nailing is an effective treatment for aseptic femoral diaphyseal fracture non-union. Patients with infection required more than one procedure. Smoking, infection and the presence of dead-bone or a gap at the fracture site were associated with an increased risk of further fixation surgery.

We conducted a multicentre two arm double blind randomised controlled trial to assess efficacy of pulsed ultrasound for accelerating the rate of bone healing. Sixty-two skeletally mature adults undergoing limb lengthening, of between 2.5cm to 10cm by distraction osteogenesis, at the proximal tibia using an Ilizarov frame were randomised to either an active or a placebo (control) ultrasound device.

Primary outcome measure was time ready for removal of frame after adjusting for distraction length (days/cm) for both intension to treat (ITT) and per protocol (PP) patients. The time at which the frame was removed was determined by the maturation of the regenerate bone. Secondary outcomes were return to weight bearing and covariates affecting time to frame removal.

The baseline characteristics of the two groups were well balanced, and 90% of patients were managed and followed up as PP. There was no difference in the time to frame removal between the two groups for the ITT (5.0days/cm, p=0.23) or the PP (10.1days/cm, p=0.054). There was no difference in return to weight bearing between the two groups, after adjusting for distraction length, for the ITT or PP patients (p>0.5). Smoking was the only covariate identified to increase the frame removal time (hazard ratio 0.46, 95% confidence interval 0.22 to 0.96; p=0.04).

This trial demonstrated no difference in bone healing between those who underwent pulsed ultrasound and those who did not. Smoking was observed to have a significant inhibitory effect on bone healing.

Adipose tissue is an attractive source of mesenchymal stem cells (MSCs) as it is largely dispensable and readily accessible through minimally invasive procedures such as lipoaspiration. Until recently MSCs could only be isolated in a process involving ex-vivo culture. Pericytes (CD45−, CD146+, and CD34−) and adventitial cells (CD45−, CD146−, CD34+) represent two populations of MSCs (collectively termed perivascular stem cells or PSCs) that can be prospectively purified using fluorescence activated cell sorting (FACS). We performed FACS on lipoaspirate samples from n=129 donors to determine the frequency and yield of PSCs and to establish patient and processing factors that influence yield.

The mean number of stromal vascular fraction (SVF) cells from 100ml of lipoaspirate was 37.8×106. Within the SVF, mean cell viability was 82%, with 31.6% of cells being heamatopoietic (CD45+). Adventitial cells and pericytes represented 31.6% and 7.9% of SVF cells respectively. As such, 200ml of lipoaspirate would theoretically yield 24.5 million MSCs –a sufficient number to enable point-of-care delivery for use in several orthopaedic applications. The yield and prevalence of PSCs were minimally affected by donor age, sex and BMI. Storing lipoaspirate samples for up to 72 hours prior to processing had no significant deleterious effects on MSC yield or viability.

Our study confirms that pure populations of MSC-precursors (PSCs) can be prospectively isolated from adipose tissue, in sufficient quantities to negate the necessity for culture expansion while widening possible applications to include trauma, where a time delay between extraction and implantation excludes their use.

Objective:

To assess efficacy of pulsed ultrasound for accelerating regenerate consolidation.

The aim of this study was to identify risk factors for failure of exchange nailing in tibial diaphyseal fracture non-unions. The cohort comprised 99 tibial diaphyseal fracture non-unions treated by exchange nailing. The mean age of the patients at exchange nail surgery was 36 years. The median time from primary fixation to exchange nailing was 6.4 months. The main outcome measures were union, number of secondary fixation procedures required to achieve union and time to union. Univariate analysis and multiple regression were used to identify risk factors for failure to achieve union.

Multiple causes for non-union were found in 31.3% cases, with infection present in 32.3%. Further exchange procedures were required in 35.4%, 7.1% required the use of other fixation modalities. Union was ultimately achieved in 97.8%. The median time to union was 8.7 months. Univariate analysis revealed that cigarette smoking, an atrophic pattern of non-union and infection were predictive for failure of exchange nailing (p<0.05). Multi-regression analysis found that only infection was statistically significantly predictive (p<0.05) of exchange nail failure.

Exchange nailing is an effective treatment for tibial diaphyseal non-unions even in the presence of infection. Smoking, atrophic pattern of non-union and infection are associated with an increased risk of further fixation surgery.

The purpose of this study was to identify the prevalence of common mental disorders in patients undergoing complex limb reconstruction.

Patients undergoing limb reconstruction are vulnerable to mental health problem as they must adapt to significant and prolonged physical disability. Treatment emphasis has been on restoration and rehabilitation of physical health with little or no attention given to spectrum of psychological consequences. IMPARTS (Integrating Mental and Physical healthcare: Research, Training and Services) is a King's Health Partners initiative aiming to develop informatics to improve detection and management of common mental disorders in medical settings. IMPARTS screening in the King's College Hospital limb reconstruction clinic commenced in April 2012.

Outpatients attending between April 2012 and November 2013 were screened prior to their appointment. Patients were screened for symptoms of depression, anxiety, post-traumatic stress disorder (PTSD), alcohol dependence and drug use.

In total, 298 individual patients were screened. The prevalence of depression was found to be 21.8%, with 6.4% experiencing suicidal thoughts. Probable anxiety disorder was identified in 20.7% of patients. Symptoms of PTSD were reported by 29.2%, with 9.0% reporting severe symptoms. Probable alcohol dependence was identified in 2.7% of patients, and 3.0% screened positive for drug misuse.

The consequences of undergoing limb reconstruction stretch beyond the physical problem to mental well-being, rendering patients vulnerable to mental health problems and substance misuse. Early detection and management of such problems may have a significant effect on physical treatment outcome and rehabilitation to productive social life. There is urgent need to integrate mental health care as part of early management of severely injured patients.

Bone cutting produces heat which macroscopically leads to charring and the formation of bone dust. As part of a project to design a novel bone cutting device, we studied the extent of histological thermal damage from bone cutting with different cutting blades.

Three blades were used: a bone hacksaw made in the nineteenth century which was used for amputation, a sagittal saw blade made by Ortho Solutions, and a sagittal saw blade made by Stryker. Sheep femurs were harvested from recently euthanised animals and cuts were made with these three devices, producing ring-shaped bone specimens. Specimens were immediately stored in formaldehyde, decalcified, and stained with hematoxylin and eosin. The edge of the specimens was then photographed microscopically, and the images examined with the computer programme Axiovision (Carl Zeiss AG, Oberkochen, Germany). Visual examination allowed identification of live and dead osteocytes, and also to measure their depth from the surface.

A minimal of 7 images was obtained per blade. The hacksaw specimens had the highest percentage of live osteocytes (n=214, 59.8%), and with the shortest average depth where live osteocytes were located (169μm, SD 78.15). In comparison, the percentage of live osteocytes for the Ortho Solutions (n=156, 17.4%) and Stryker (n=168, 29.5%) blades were much lower. The difference in average depths where live osteocytes were located was statistically significant between the three groups (p < 0.001). The average depths of dead osteocytes were shallowest for the Stryker (115μm, SD 67.56) and hacksaw (118.28 μm, SD 75.16) groups with no statistical difference between them.

In conclusion the hacksaw appeared to produce the least thermal damage histologically during cutting. The results reflect a relationship between certain features in cutting blade designs and the extent of thermal damage. Future experiments to directly measure heat produced during cutting are planned.

Bone cutting produces heat which macroscopically leads to charring and the formation of bone dust. As part of a project to design a novel bone-cutting device, we studied the extent of histological thermal damage from different cutting blades. Three blades were used: a nineteenth century bone hacksaw, and modern sagittal saw blades manufactured by Ortho Solutions and Stryker. Sheep femurs were harvested from recently euthanised animals and cuts were made with these blades. Specimens were immediately stored in formaldehyde, decalcified, and stained with hematoxylin and eosin. The edge of the specimens was then photographed microscopically, and the images examined with Axiovision software (Carl Zeiss AG, Oberkochen, Germany). Visual examination allowed identification of live and dead osteocytes, and also to measure their depth from the surface. A minimal of 7 images was obtained per blade. The hacksaw specimens had the highest percentage of live osteocytes (n=214, 59.8%), and the shortest average depth where live osteocytes were located (169 μm, SD 78.15). In comparison, the percentage of live osteocytes for the Ortho Solutions (n=156, 17.4%) and Stryker (n=168, 29.5%) blades were much lower. The difference in average depths where live osteocytes were located was statistically significant between the three groups (p<0.001). In conclusion the hacksaw appeared to produce the least thermal damage histologically during cutting. The results reflect a relationship between certain features in cutting blade designs and the extent of thermal damage. Future experiments to monitor heat produced during cutting are planned.

Aim

To investigate the effects of strain rate and mineral level on the stress at failure, stiffness and toughness of whole bones.

Staphylococcus aureus is a highly virulent pathogen and implicated in approximately 50% of cases of septic arthritis. Studies investigating other S. aureus-related infections suggest that alpha-(Hla), beta-(Hlb) and gamma-(Hlg) toxins are key virulence factors, with the ‘pore-forming’ alpha-toxin considered the most potent. Here, we have assessed the influence of alpha-toxin alone on in situ chondrocyte viability. Osteochondral explants were harvested from the metacarpophalangeal joints of 3-year-old cows and cultured in Dulbecco's Modified Eagle's Medium. The flasks were then inoculated with isogenic ‘knockout’ strains of S. aureus: DU5946 (Hla+Hlb-Hlg-: alpha-toxin only strain) or DU1090 (Hla-Hlb+Hlg+: beta- and gamma-toxin only strain). Explants were incubated (37°C) and stained after 18, 24 and 40hrs with chloromethylfluorescein-di-acetate and propidium iodide, labelling living chondrocytes green and dead cells red, respectively. Axial sections were imaged by confocal microscopy and the percentage cell death determined. Alpha-toxin-producing S. aureus caused 24.8+/−3.7% chondrocyte death at 18hrs and 44.6+/−7.2% death at 24hrs. At 40hrs, there was significantly more chondrocyte death (87.4+/−3.6%;p<0.001) compared to the alpha-toxin knockout strain, which was negligible (4.1+/−1.7%; means+/−SEM; N=4 independent experiments). In this in vitro bovine cartilage explant model, whereby the effects of defined toxins were determined in isolation of a complex host immune response, in situ chondrocyte viability was dramatically and exclusively reduced by alpha-toxin. This work forms the basis for developing a rational treatment to reduce the extent of cartilage destruction during an episode of septic arthritis. IDMS was supported by Orthopaedic Research UK and The Royal College of Surgeons of Edinburgh.

We have demonstrated that toxins produced by Staphylococcus aureus, a common infective agent in septic arthritis (SA), cause rapid in situ chondrocyte death. Here, we have compared the sensitivity of chondrocytes within the superficial and deep zones (SZ, DZ) of cartilage to the same toxins. Culture medium containing the toxins produced by S. aureus strain 8325-4, which include alpha-, beta-, and gamma-toxin, was prepared. Cartilage explants free of subchondral bone were taken from the metacarpophalangeal joints of 3-year-old cows, and incubated (37°C) with the toxins. Explants were stained after 6hrs with chloromethylfluorescein-di-acetate and propidium iodide, labelling living chondrocytes green and dead cells red, respectively. Full-thickness coronal sections were imaged by confocal microscopy and the percentage cell death within the SZ (100μm from articular surface) and DZ (100μm from subchondral bone interface) determined. Both zones were incubated with the same toxin culture medium for the same time period. At 0hrs, chondrocytes within all zones were >98% viable. However, after incubation with toxin-containing culture medium for 6hrs, 71.9+/−11.2% of the SZ cells were dead compared to only 47.4+/−6.7% in the DZ (p=0.03;data are means+/−SEM;N=4). These results suggest that SZ chondrocytes are considerably more sensitive to S. aureus toxins than those within deeper zones. As SZ chondrocytes are close to the synovial fluid harbouring bacterial toxins, these data emphasise the need to remove bacteria and their products aggressively as part of the treatment of SA. IDMS was supported by Orthopaedic Research UK and The Royal College of Surgeons of Edinburgh.

The type, duration and intensity of exercise required to induce mechanical hypoalgesia is poorly defined. We are interested in identifying the exercise parameters required to induce raised pressure pain thresholds. This pilot study investigates the effect of indoor rowing on pressure pain threshold (PPT) in high performance rowers. Our ultimate aim is to investigate the potential of utilising exercise in the treatment of chronic pain and specifically in relation to the management of knee osteoarthritis. 20 high performance rowers (13M:7F; Mean Age 20.8 years; SD 1.74) were recruited from the University of Nottingham and Nottingham Boat Club high performance rowing teams under a research protocol approved by the University of Nottingham Ethics Committee. PPT measurements were made in triplicate using an algometer (SOMEDIC, Sweden) at the medial knee joint line, anterior tibia and sternum, pre- and post-exercise. Anthropomorphic and rowing ergometer power output data were also recorded. There was significant increase in PPT values at all sites following exercise (Medial joint line: 127.6Nm-2, 26%, p=0.001; Tibia: 110.8Nm-2, 24.7%, p<0.001; Sternum: 48.9Nm-2, 11.7%, p=0.005 – Wilcoxon Signed Rank) statistical power was 97.1%, 100% and 88.1%, respectively. PPT was greater at baseline at the medial joint line compared to other sites, reaching highly significant relative to the sternum (p<0.001). We determined that ten minutes of high intensity indoor rowing induced hypoalgesia in high performance rowers. Further research is required to investigate the detailed interplay between exercise and hypoalgesia, including its duration post exercise, to identify suitability for use in pain management strategies.

INTRODUCTION

This study investigates the relationship between direct measurement of outcome and patient report of that outcome via the OKS. The stability of this relationship over time following surgery is also assessed.

Introduction

Bending tests are commonly used to evaluate the mechanical behaviour of small animal bones. To test whole bones, it is normal that soft tissue should be removed before testing. However, cleaning the specimens might disturb the callus, interfering with the mechanical properties. This study compares mechanical properties of rat tibia between specimen with and without muscle cleaning

Aim

Although non-union is a devastating and costly consequence of trauma for the child, family and society it is felt to be a rare complication in children. Currently there is no data available in the literature regarding its incidence either per fracture or per head of population. Should we be taking paediatric fracture non-union more seriously regarding research, resource allocation and informed consent? Our aim was to determine the incidence of non-union per child and per fracture.

Staphylococcus aureus is a highly virulent pathogen and is implicated in approximately 50% of cases of septic arthritis. Studies investigating other S. aureus-related infections have suggested that alpha (Hla), beta (Hlb) and gamma (Hlg) toxins are key virulence factors. In particular, the ‘pore-forming’ alpha toxin is believed to be most potent. In this study, we have assessed the influence of alpha toxin on in situ chondrocyte viability.

Osteochondral explants were harvested from the metacarpophalangeal joints of 3-year-old cows and placed into flasks containing Dulbecco's Modified Eagle's Medium. The flasks were then inoculated with the following isogenic ‘knockout’ strains of S. aureus: DU5946 (Hla+Hlb-Hlg-) or DU1090 (Hla-Hlb+Hlg+).

The explants were incubated (37°C) and stained after 18, 24 and 40hrs with chloromethylfluorescein di-acetate and propidium iodide, labelling living chondrocytes green and dead cells red, respectively. Axial sections were imaged by confocal microscopy and the percentage cell death obtained using Volocity 4 software.

The alpha toxin-producing S. aureus caused rapid cell death, with 24.8+/−3.7% at 18hrs and 44.6+/−7.2% at 24hrs. At 40hrs, there was significantly more chondrocyte death (87.4+/−3.6%; p<0.001) compared to the alpha toxin knockout strain (4.1+/−1.7%; means +/− SEM; n=4).

In situ chondrocyte viability was significantly compromised by alpha toxin, with beta and gamma toxins having minimal effect. Further work will clarify the exact mechanism through which this important toxin induces chondrocyte death. Thereafter, it is hoped that targeted treatments can be developed to reduce the extent of cartilage destruction during, and after, an episode of septic arthritis.

The treatment of chronic osteomyelitis requires both appropriate surgical and antibiotic management. Prolonged intravenous antibiotic therapy followed by oral therapy is widely utilised. Despite this, the long-term recurrence rate is approximately 25%. The aim of this cohort study was to examine the effectiveness of marginal surgical resection in combination with local application of antibiotics (Collatamp G - gentamicin in a collagen fleece). Post-operatively this was followed by a short course of intravenous antibiotics, then oral antibiotics, to 6 weeks in total. A cohort of 50 patients from a 10-year period, 2000 to 2010, with chronic osteomyelitis was identified. Most were male (n= 35, 70%) and the average age is 40.9 years (SD 15.9). The mean follow-up duration was 3.2 years (SD 1.8). The average length of admission was 9.8 days (SD 11.4). 6 patients (12%) suffered recurrence of infection requiring further treatment. We used the Cierny and Mader classification to stratify the patients further. There were 24 (48%) ‘A’ hosts and 26 (52%) ‘B’ hosts. ‘A’ hosts had a shorter duration of admission (7.1 days) than ‘B’ hosts (12.3 days). There was no significant difference between recurrence rates of ‘A’ and ‘B’ hosts. The available pre-operative C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels did not predict disease recurrence. Overall, the disease-free probability for this cohort was 0.80. A similar cohort treated with prolonged systemic and oral antibiotics reported by Simpson and colleagues (JBJS Br 2001) had a disease-free probability at 0.68. Local administration of gentamicin in a collagen fleece leads to improved disease-free probability when compared with prolonged systemic antibiotic treatment. We believe this is a useful component in the management of chronic osteomyelitis.

Aims

The aim of this study was to compare biomechanical properties of pre-contoured plate fixation using different screw fixation modes in a mid-shaft clavicle fracture model.

Staphylococcus aureus is the most common bacterial isolate in septic arthritis. From studies on isolated cartilage cells, the ‘pore-forming’ alpha and gamma toxins are considered the most virulent factors. However, understanding the response of in situ chondrocytes is important in order to identify new treatments to reduce the extent of cartilage damage during, and following, episodes of septic arthritis. Animal models can give useful information; however the interpretation of data can be complex because of the strong immune response. Thus, to clarify the role of S. aureus toxins on in situ chondrocytes we have developed a bovine cartilage explant model.

Metacarpophalangeal joints, from 3-year-old cows, were opened under sterile conditions within 6hrs of slaughter and cartilage explants harvested. Explants were placed into flasks containing Dulbecco's Modified Eagle Medium (DMEM). Aspirates from a patient with septic arthritis of the hip, containing S. aureus, were compared to negative aspirates (no bacterial growth) from a patient with an inflamed knee joint (controls).

The explants were incubated at 37 degrees Celsius and stained after 18, 24 and 40hrs with the fluorescent probes chloromethylfluorescein di-acetate and propidium iodide (10 micromolar each) to label living chondrocytes green and dead cells red respectively. Following imaging of cartilage by confocal laser scanning microscopy, the percentage cell death at each time point was obtained using Volocity 4 software.

There was no detectable change in chondrocyte viability (<1% cell death) over 40hrs incubation with the negative aspirate. However, for the aspirate from a patient positive for S. aureus, there was a rapid increase in cell death between 18 and 24hrs (0.2 +/− 0.3% to 23 +/− 5% cell death respectively) and almost complete cell death at 40hrs (80 +/− 12%; data are means +/− s.d; n=4).

These results show that a strain of S. aureus capable of manifesting clinical disease exerts a potent effect on in situ chondrocytes. In the absence of an immune response, chondrocyte death was purely the result of the bacteria and their products. This bovine cartilage explant model could therefore be useful for studying the effects of S. aureus on chondrocyte behaviour and, ultimately, cartilage integrity.

There is an established link between bone quality and fracture risk. It has been suggested that reduced bone quality will also reduce the toughening mechanisms displayed during loading at a high strain rate. We hypothesised that partially decalcified bone will not demonstrate an increase in force required to cause failure when comparing low and high strain rate loading.

Mechanical properties were defined by the maximum force at failure. Bone quality was defined by the mineral content. This was altered by subjecting the bones to ultrasonically assisted decalcification in 10M EDTA to achieve an average 18% mineral reduction (A 70 yr old woman has approx 18% of her peak bone mass). 20 pairs of sheep femurs were harvested and split into four equal groups: normal bone quality, fast strain rate (NF); normal bone quality, slow strain rate (NS); low bone quality, fast strain rate (LF) and low bone quality, slow strain rate (LS). All mechanical testing was carried out by means of 3-point bending. Load representing the slow strain rate was applied by a mechanical testing machine (Zwick) at a rate resulting in a deflection of 1mm/s. The dynamic loading was applied by a custom designed pneumatic ram at a mean rate of deflection between the specimens of 2983 mm/s (±SD 1155), this equates to strain rates experienced in a road traffic accident.

The following results for force at failure were found (mean ± SD). NF: Force 5503N (± 1012); NS: Force 3969N (± 572); LF: Force 3485N (± 772); LS: Force 3165N (± 605). Groups were compared using a Mann-Whitney U test. Significant results were found between the following groups: Normal bone quality, strain rate compared (NF-NS) p<0.002; Fast strain rate, bone quality compared (NF-LF) p=0.008; Slow strain rate, bone quality compared (NS-LS) p=0.02. No statistical significance was found when comparing low bone quality, strain rate compared (LF-LS) p=0.47.

These results show that normal healthy bone has an ability to withstand higher strain rates which protects it against fracture. This ability to withstand high strain rates is lost in decalcified bone making it more susceptible to fracture. The results of this study indicate the importance of strain rate reduction as well as energy absorption in the design of hip protectors and in environmental modifications.

End-stage osteoarthritis is characterised by pain and reduced physical function, for which total knee arthroplasty (TKA) is recognised to be a highly effective treatment. Most implants are multi radius in design, though modern kinematic theory suggests a single flexion/extension axis is located in the femur. A recently launched TKA implant (Triathlon, Stryker US), is based on this theory, adopting a single radius of curvature femoral component. It is hypothesised that this design allows better function, and specifically, that it results in enhanced efficiency of the quadriceps group through a longer patello-femoral moment arm.

Change in power output was compared between single and multi radius implants as part of a larger ongoing randomised controlled trial to benchmark the new implant. Power output was assessed using a Leg Extensor Power Rig, well validated for use with this population, pre-operatively and at 6, 26 and 52 weeks post-operatively in 101 Triathlon and 82 Kinemax implants. All patients were diagnosed with osteoarthritis, and drawn from a single centre. Output was reported as maximal wattage (W) generated in a single leg extension, and expressed as a proportion of the contralateral limb power output to act as an internal control.

The results are shown in the table below. Two-way repeated measures ANOVA demonstrated a significant effect of TKA on the quadriceps power output, F = 249.09, p = <0.001 and also a significant interaction of the implant group on the output F = 11.33, p = 0.001. Independent samples t-tests of between group differences at the four assessment periods highlighted greater improvement in the single radius TKA group at all post-operative assessments (p <0.03), see table.

The theoretical enhanced quadriceps efficiency conferred by single radius design was found in this study. Power output was significantly greater at all post-operative assessments in the single radius compared to the multi radius group. This difference was particularly relevant at early 6 week and 1 year assessment. Lower limb power output is known to link positively to functional ability. The results support the hypothesis that TKAs with a single radius design have enhanced recovery and better function.

In some centres, serial bedside aspirations, in association with intravenous antibiotics, are still an accepted treatment for septic arthritis (Mathews, Postgraduate Medical Journal, 2008). However, there is a risk that bacterial products remain in the joint, even when the bacteria have been destroyed. We have conducted a study to ascertain whether bacterial products alone have an effect on in situ chondrocyte viability.

A hip aspirate (25μl), containing Staphylococcus aureus, from a patient with septic arthritis was added to 5ml culture medium and incubated (37°C) for 48hrs. The solution was then centrifuged (3400g for 10mins) and the supernatant removed.

Cartilage explants were harvested from a bovine metacarpophalangeal joint, placed into the bacterial supernatant and incubated at 37°C. Explants were removed at hourly intervals over a 6-hour period and stained with the fluorescent probes chloromethylfluorescein di-acetate (10μM) and propidium iodide (10μM) to label living chondrocytes green and dead cells red respectively. Following imaging of cartilage by confocal microscopy, the percentage cell death at each time point was obtained using Volocity 4 software.

Chondrocyte death increased markedly with time: 0.04% at 2hrs, 28% at 4hrs and 39% at 6hrs.

This study shows that bacterial products rapidly penetrate the cartilage matrix and have a damaging effect on in situ chondrocyte viability. Further work will clarify the contributions made by the various toxic components in the culture supernatant, but these data support the need to remove the bacteria and their products aggressively as part of the treatment of septic arthritis.

The treatment of chronic osteomyelitis requires both appropriate surgical and antibiotic management. Prolonged intravenous antibiotic therapy followed by oral therapy is widely adopted. Despite this, the long-term recurrence rate is around 20% to 30%.

The aim of this cohort study was to examine the effectiveness of surgical marginal resection in combination with local application of antibiotics (Collatamp G - gentamicin in a collagen fleece). Post-operatively this was followed by a short course of intravenous antibiotics, then oral antibiotics, to 6 weeks in total.

A cohort of 50 patients from a 10-year period, 2000 to 2010, with chronic osteomyelitis was identified. Most were male (n= 35, 70%) and the average age is 40.9 years (SD 15.9). The mean follow-up duration was 3.2 years (SD 1.8). The average length of admission was 9.8 days (SD 11.4). 6 patients (12%) suffered recurrence of infection requiring further treatment. We used the Cierny and Mader classification to further stratify the patients. ‘A’ hosts had a shorter duration of admission (7.1 days) than ‘B’ hosts (12.3 days). There was no significant difference between recurrence rates of ‘A’ and ‘B’ hosts. Where available, we found pre-operative C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) levels had no correlation with disease recurrence. Disease-free probability for this cohort compared favourably with a cohort treated with prolonged systemic and oral antibiotics (Simpson and colleagues, JBJS Br 2001).

We believe local administration of gentamicin in a collagen fleece is a useful component in the management of chronic osteomyelitis.

Introduction

Recovery of muscle strength following Total Knee Replacement (TKR) is variable, and can affect the resultant function of the patient. Satellite cells are undifferentiated myogenic precursors considered to be muscle stem cells that lie quiescently around the muscle fibre. These cells repair damaged fibres and have the potential to generate new muscle fibres. Therefore, theoretically, they could be associated with the variation in muscle recovery following surgery. We hypothesised that the recovery of muscle strength following knee replacement in a given patient would be influenced by the underlying number of satellite cells in that patient.

A significant source of failure for external fixation devices is loosening of the fixation implant. As bone competence drops with ageing or disease such as osteoporosis, the risk of loosening is likely to increase. However it is not clear how fixator configuration should be adapted to minimise loosening in weaker bone. The aim of this study was to assess the effect of bone competence on the yielding of bone tissue surrounding fixation implants, and thereby inform the selection of fixator configuration to minimise loosening. External fixation of the tibial midshaft using half-pins and Illizarov wires was modelled using finite-element analysis. Half-pin configurations of two and three stainless steel and titanium pins pins were assessed. Illizarov wire configurations of two and four wires were studied, over a range of wire tensions. Bone competence was varied by changing the cortical thickness and elastic properties of the bone fragments to approximate: a) young, high-density bone, b) middle-aged, mid-porosity bone and c) old-aged, severely porous bone. Bone elastic properties were taken from a recent study of cortical bone conducted by the authors. The interaction between implants and bone was modelled with contact analysis, enabling realistic separation. Implant loosening was included using a bone-specific, strain-based yield criterion. Regions where bone tissue yielded were identified as likely sites of loosening. In all cases loading was applied to simulate a one-legged stance.

Fractures repair by two mechanisms; direct fracture healing and indirect fracture healing via callus formation. Research concerning the effects of bisphosphonate on fracture repair has solely assessed indirect fracture healing. Patients with osteoporosis on bisphosphonates continue to sustain fragility fractures. A proportion of osteoporotic fractures require plate fixation. Bisphosphonates impair osteoclast activity and therefore, may adversely affect direct fracture healing that predominates with plate fixation.

Five skeletally mature Sprague-Dawley rats received daily subcutaneous injections of 1mg/kg Ibandronate (IBAN). Similarly, five control rats received saline (CONTROL). Three weeks following commencement of injections a tibial osteotomy was rigidly fixed with compression plating similar to that seen in routine clinical practice. Fracture healing was monitored with radiographs. Six weeks post plate fixation, animals were sacrificed. Radiographs were performed of the extricated tibiae following plate removal. The visibility of the osteotomy site was scored as totally visible, partially visible or absent as previously described. Mechanical testing was conducted on the healing osteotomies via 4-point bending.

Fractures healed without visible external callus. In the IBAN group three animals had totally visible osteotomy lines and two had partially visible osteotomy lines. The CONTROL group had three animals with absent osteotomy lines and two with partially visible osteotomy lines. The mean (±SD) stress at failure for the healing tibial osteotomies at 6 weeks was 28.8 (±23.97)MPa in the IBAN group and 37.4(±29.20) MPa in the CONTROL group (p=0.62)

Our results indicate that Ibandronate adversely affected direct fracture repair as demonstrated by the radiographic density of the fracture line. The strength of the repair was reduced but this did not reach statistical significance. Our results suggest that a sample size of 220 animals is required to detect a 15% difference (alpha 0.05, beta 0.2) which suggests the effect of bisphosphonates on direct fracture repair may be small.

The effect of bisphosphonates on the mechanical properties of the uninjured contra-lateral cortical bone during fracture healing is poorly reported. There remains conflicting evidence with regards the effect of bisphosphonate therapy on cortical bone strength. We assessed the effect of nine weeks of Ibandronate therapy, in a dose known to preserve cancellous bone BMD and strength, on the mechanical properties of the uninjured rat tibial diaphyses using a standardised model of tibial osteotomy and plate fixation. Skeletally mature ex-breeder rats were used. Stress at failure of the tibial diaphyses was measured by a four-point bending test using a custom made jig for rat tibiae. The mechanical strength was compared with radiographic measurements of bone density. Animals received daily subcutaneous injections. 11 rats received 1μg/kg Ibandronate (IBAN) daily and 17 rats received 1ml 0.9% Sodium Chloride (CONTROL) daily.

The IBAN group had a statistically significant, p=0.024, higher stress at failure 212.7 (±42.04) MPa compared to the CONTROL group 171.7 (±46.13)MPa. There was a positive correlation between the mechanical strength of bone and the radiological measure of bone density.

Osteopenia is known to occur following a fracture even in the contra-lateral limb. This study demonstrates that ibandronate therapy has no detrimental effect and may even increase the strength of uninjured cortical bone during the fracture healing process. The longer term effect of ibandronate on cortical bone especially in relation to the accumulation of mico-damage requires further study. Bisphosphonate effect on the uninjured limb needs to be considered when reporting proportional strength of fracture repair compared to the uninjured limb.

Few studies have investigated the direct effect of bacteria and their products on articular cartilage chondrocytes ex vivo. An ex vivo model that allows the analysis of chondrocytes in situ would therefore be an important and exciting area of future research. It was hypothesised that a bovine cartilage explant model of septic arthritis would be an ideal model for providing fundamental information on the basic cellular mechanisms of cartilage destruction and chondrocyte death induced by bacterial infection uncomplicated by the immune response.

A fresh metacarpophalangeal joint from an abattoir slaughtered 3-year-old cow was skinned, rinsed in water and opened under sterile conditions. The cartilage explants were harvested using surgical scalpels and placed into a total of three tissue culture bottles (2 explants per bottle) containing 10ml Dulbecco's Modified Eagle Medium (DMEM). 50ml of a knee aspirate from a patient with septic arthritis, containing Group B streptococci (GBS), was added to bottle 1, 50ml of a negative knee aspirate was added to bottle 2 and 50ml DMEM to bottle 3.

The explants were incubated at 37°C for 24 hours. They were then stained with the fluorescent probes Chloromethylfluorescein Di-acetate (CMFDA) and Propidium Iodide and analysed using a Confocal Scanning Laser Microscope. Cell counts to assess percentage cell death were performed using Velocity 4 software.

There was strikingly more cell death observed at 24 hours in the cartilage explant exposed to bacteria in comparison to the non-infected controls. The percentage chondrocyte death was 43% in the presence of GBS, 0.8% in the presence of the negative aspirate and 0.2% in the presence of the DMEM control.

Although this is a very preliminary pilot study, it demonstrates an extremely rapid effect on the cartilage. Future bovine explant studies of septic arthritis will therefore be feasible and achievable.

Clostridium difficile is associated with a range of gastrointestinal disorders ranging from diarrhoea to toxic megacolon. Alteration of the normal gut flora by antibiotics is a key predisposing factor. Although antibiotic prophylaxis is routinely administered during joint replacement surgery, there has been controversy about both type and duration of prophylaxis. The primary aim of this study was to determine the incidence of C. diff associated disease (CDAD) following hip and knee replacement and to investigate potential risk factors.

A laboratory database was interrogated to identify patients developing CDAD after hip or knee replacement from January 2006 to December 2008. A database of arthroplasty patients was used to identify a control group of patients without CDAD to compare the effects of prescription of antibiotics for reasons other prophylaxis of deep infection, comorbidity and the use of gastroprotective agents.

Eight patients developed CDAD. There were 1.7 cases of CDAD per 1000 joint replacements. Patients developing CDAD were more likely to have been prescribed additional antibiotics (p=0.047). There were no differences in the use of gastroprotective agents (p=0.703). A trial of a new prophylaxis regime would require 43,198 patients in each arm to show a reduction to 1 case per 1000 procedures.

Cefuroxime based antibiotic prophylaxis is safe in patients undergoing elective joint replacement. Extremely large studies would be required to show marginal clinical benefits of new regimes. One prophylaxis policy will not suit all orthopaedic patient groups or procedures.

Background and Aims: Plate fixation of acute mid-shaft clavicle fractures is becoming increasingly popular. However limb and life threatening complications such as injury to the subclavian vessels have been reported. One possible solution to reduce the risk of this complication is the use of unicortical screw fixation.

The aim of this study was to compare biomechanical properties of pre-contoured plate fixation using different screw fixation modes in a mid-shaft clavicle fracture model.

Methods: Fourth generation biomechanical clavicle sawbones with a mid-shaft osteotomy were plated in one of three modes: nonlocking bicortical, locking bicortical and locking unicortical mode. The specimens were then tested to failure in four-point bending and pull-off tests.

Results: Failure due to fracture through the sawbone was more common in nonlocking bicortical mode while plate bending was more common in the locking bicortical group. The ultimate load at failure was significantly lower in the locking bicortical group compared to the nonlocking bicortical group, however there was no significant difference between the locking unicortical group and nonlocking bicortical group.

In the pull-off tests 100% of nonlocking bicortical and locking bicortical plates failed by fracture of the sawbone. 100% of the locking unicortical plates failed by plate and screw pull-off from the sawbone. The load at failure was highest for the locking unicortical plate but this was not significantly different to the other groups.

Conclusion: This study shows that specimens fixed with locking unicortical screw fixation withstood comparable or superior loads in four-point bending and pull-off test when compared to nonlocking bicortical and locking bicortical screw fixation. In addition both locking screws and unicortical screws appear to provide a protective effect against periprosthetic sawbone fracture. Locking unicortical screw fixation of pre-contoured plates may be a viable alternative in the fixation of mid-shaft clavicle fractures.

Background: Muscle tears and injuries are a huge problem throughout the world. Ways of reducing these injuries are welcome, with warm-up and stretching of muscles prior to use established methodologies. Forces associated with muscles can be thought of as active (stimulated muscle: actin-myosin) and passive (relaxed muscle: elastic proteins and connective tissue). In muscle tears, the connective tissue component is damaged, but there is very little information in the literature on this component of the muscle.

Objective: To examine passive (elastic) components in muscle during impact loading at differing temperatures. In particular to test the hypothesis that the connective tissue component fails at different loads according to the temperature.

Methods: Gastrocnemius and Soleus were isolated from 36 male rat limbs, clamped and exposed to increasing impact loads, by dropping a known weight from increasing heights. Muscle was given one minute to recover before an increased force was applied. Temperature was varied from 17 C to 42 C (to encompass the physiological range) in 5 C increments. The height of drop causing non-recoverable deformation, and the maximum deceleration of the weight (measured using an accelerometer attached to a picoscope) at a constant height was recorded for each temperature.

Results: The energy to failure, i.e. the point at which non-recoverable deformation occurred was found to increase above 32 C (p < 0.01) and the maximum deceleration at impact found to have a downward trend with increasing temperatures. At 17 C, the energy to failure was 317.7 ± 20 mJ, At 22 C, the energy to failure was 301.8 ± 29 mJ, At 27 C, the energy to failure was 317.7 ± 40 mJ, At 32 C, the energy to failure was 333.5 ± 21.2 mJ, At 37 C, the energy to failure was 460.2 ± 15.8 mJ, At 42 C, the energy to failure was 619.5 ± 21.2 mJ,

Conclusions: Muscle was shown to act in an increasingly elastic nature with temperature. At higher temperatures a larger energy is required to deform the muscle permanently, and the muscle decelerates more slowly, both in keeping with elastic properties. The same energy at a lower temperature causes significant deformation within the muscle. This has numerous clinical implications, as the temperature at which this change occurs is encountered during surgery and also by sportsmen on outdoor pitches. More research is required to look at the passive components within muscles in humans.

Introduction: Limb lengthening with external fixators has been associated with many complications including pin tract infections, damage to neurovascular structures, joint stiffness, delayed consolidation, and pain. These can lead to a detrimental functional outcome and psychological upset with a consequent negative impact on patients’ quality of life. The Intramedullary Skeletal Kinetic Distractor (ISKD) is a fully implantable device that may offer a better functional and psychological outcome. The aim of this study therefore was to evaluate the functional and psychological outcome in a series of patients undergoing femoral lengthening with the ISKD.

Methods: Twenty patients underwent intramedullary lengthening via ISKD. Eighteen of these had lost femoral bone length secondary to trauma, and two were affected by congenital limb shortening (one had both femora lengthened at different time intervals). Patients completed Toronto Extremity Salvation Score (TESS) (to evaluate subjective physical disability), and Short Form 36 (SF36) questionnaires pre and post-operatively.

Results: Patients’ post operative TESS scores demonstrated a significant improvement in patient perception of their physical disability. SF36 responses after surgery improved in several areas including physical functioning, role limitation due to emotional problems, social functioning, mental health, pain experienced and change in health; the greatest improvements seen in role limitation due to emotional problem, social functioning, mental health, pain, and change in health.

Discussion: These results indicate that limb lengthening with the ISKD improves patients’ overall quality of life decreasing post operative pain, improving their social functioning and mental health, overall ISKD lengthening improves how the patients perceive their health and physical disability.

The diagnosis of musculoskeletal infection is an ongoing problem. Multiple specimens and histology peri-operatively have been used to increase the accuracy of the diagnosis. However, to determine antibiotic resistance profiling it is essential to grow bacteria from the patient. The aim of this prospective study was to evaluate whether there is an increase in the rate of isolation of micro-organisms from musculoskeletal tissue samples sent directly in broth culture or whether there is an over-diagnosis due to false positive contaminants.

Samples were taken from patients undergoing planned orthopaedic surgery (some with and some without suspected infection). Each specimen was harvested with separate instruments. The specimens were placed into universal containers without broth according to our standard protocol and also into containers with broth. These samples were cultured and the results analysed for any difference in culture growth. A total of 72 specimens were taken in the operating theatre (36 in broth, 36 without broth). The results of culture were compared to a diagnosis of infection from clinical and histological data.

Overall there were 24 true positive samples in the study (sensitivity of 66.7%) and 32 true negative samples (specificity of 88.9%). The isolation of bacteria from the culture of samples sent in broth had a sensitivity of 77.8% and a specificity of 83.3%. Whereas, the sensitivity and specificity of musculoskeletal specimens sent without broth were 55.6% and 94.4%, respectively.

The results of the study show that there is an increase in the rate of isolation of micro-organisms from musculoskeletal tissue samples sent directly in broth culture, compared to specimens sent without broth. However, the broth samples resulted in a higher rate of false positives. This study concludes that placing musculoskeletal specimens directly in broth in the operating theatre for culture improves the rate of microbiologial diagnosis. However, a larger study with more patients would be of use to confirm this.

Articular cartilage is attached to subchondral bone but little is known regarding bone-cartilage interactions important for chondrocyte survival. In this study, bovine articular cartilage has been evaluated in vitro to determine if the presence of subchondral bone influences chondrocyte survival. We hypothesised that

Excision of subchondral bone from articular cartilage would increase in situ chondrocyte death in explant culture and,

Articular cartilage explants (n=132) harvested from the metacarpophalangeal joints of three-year old cows (N=12) were placed into three groups:

subchondral bone excised from articular cartilage (Group A)

Explants were cultured in serum-free media over 7 days with or without media changes to assess the effect of potential soluble mediators. Using confocal laser scanning microscopy to image in situ chondrocytes, fluorescent probes to determine cell viability and biochemical assays to detect alterations in the culture media, differences in the chondrocyte responses (cell density, spatial distribution, percentage cell death) and culture medium composition between Groups A, B and C were quantified over time (2.5 hours versus 7 days).

There was no significant change in cell density for Groups A, B and C over 7 days (t-test, p> 0.05). With excision of subchondral bone from articular cartilage (Group A), there was a marked increase in chondrocyte death over 7 days primarily within the superficial zone involving an extensive area of the articular surface (p< 0.05). There was no significant increase in chondrocyte death over the same time period for Groups B and C (p> 0.05). Corresponding increases in the protein content of the culture media for Groups B and C but not for Group A, suggested that the release of soluble factors from subchondral bone may have influenced chondrocyte survival in the superficial zone.

Subchondral bone interacts with articular cartilage in vitro and promotes chondrocyte survival in the superficial zone. These data support the concept of a functional bone-cartilage system in vivo.

0.9% Saline and Hartmann’s are commonly used joint irrigating solutions during articular surgery. The objective of the study was to determine whether the osmolarity of these solutions affects chondrocyte death in mechanically injured articular cartilage.

The osmolarity of 0.9% Saline (285 mOsm) and Hartmann’s (255 mOsm) solutions was varied from 100–600 mOsm by the addition of distilled water or sucrose. Osteochondral explants (rectangular blocks, n=72) harvested from the metacarpophalangeal joints of six different three-year old cows were exposed to prepared solutions of different osmolarity for 2 minutes to allow in situ chondrocytes (cells embedded within their native extracellular matrix) to respond to the altered osmotic environment. Explants were then mechanically injured through the full thickness of articular cartilage with a fresh scalpel and incubated in the same solution for 2.5 hours. Using confocal laser scanning microscopy (CLSM) and fluorescent probes to determine cell viability, percentage cell death (PCD, 100 × number of dead cells/number of dead and live cells) was quantified within the full thickness of mechanically injured articular cartilage as a function of solution osmolarity.

Cell death was localised to the superficial zone (first 100 microns from the articular surface) of injured cartilage for explants exposed to the control 0.9% Saline (285 mOsm) and Hartmann’s (255 mOsm) solutions, with relative sparing of the middle and deep zones (analysis of variance (ANOVA), p< 0.05). Compared to the control explants exposed to 0.9% Saline, PCD in the superficial zone was greatest for the low osmolarity (100 mOsm) saline solution and least for the high osmolarity (600 mOsm) saline solution (ANOVA, p=0.04). PCD in the superficial zone significantly decreased for explants exposed to 600 mOsm solutions of 0.9% Saline and Hartmann’s, compared to their respective control solutions (p< 0.05 for paired comparisons). There was no significant difference in the PCD between 600 mOsm solutions of 0.9% Saline and Hartmann’s (p=0.5).

Increasing the osmolarity of 0.9% Saline and Hartmann’s solutions is chondroprotective in a surgically relevant model of mechanical cartilage injury. These experiments have important clinical relevance for the design of irrigation solutions during arthroscopic and open articular surgery.

X-ray is the standard method for monitoring fracture healing however it is not ideal; signs of healing are not normally visible on X-ray until around 6–8 weeks post fracture. Ultrasonography allows the detection of both the initial haematoma, usually formed immediately after fracture, and the small calcium deposits laid down between broken bone ends in the first stages of fracture healing. It has been reported that these early indicators of the healing process are visible as early as 1–2 weeks after fracture. We use Freehand 3D Ultrasound to monitor the early stages of fracture healing as both the bone surface and surrounding soft tissues can be imaged simultaneously.

The Freehand 3D Ultrasound system consists of a standard Ultrasound machine, a PC running STRAD-WIN (Medical Imaging Group, Cambridge University) 3D software, and an optical tracking devise (NDI Polaris) to record the position and orientation of the Ultrasound probe during scanning. Images are transferred from the Ultrasound machine to the PC using RF capture through out a scan. Calibrating the system matches up the correct image with the correct probe position to produce a 3D dataset.

We segment features of interest on the sequence of 2D images to construct a 3D model. These models are rotatable and provide views of the scanned anatomy that are not otherwise achievable using conventional Ultrasound or X-ray. The 3D data set can also be resliced through any plane to provide further views.

To conduct a 3D Ultrasound scan takes the same amount of time as a conventional 2D scan. The production of the 3D model takes between 15–60 minutes depending on the level of detail required. Distances are measurable to within ±0.4mm meaning fracture gaps of sub-millimeter width can be resolved. The system has already been evaluated on healthy volunteers and a clinical study currently underway.

An uncomplicated, quantitative method of determining density from X-rays would be of extreme value to clinicians. In this study we perform a thorough assessment of applying a step wedge to grey level calibration method to X-rays obtained using Computed Radiography (CR).

An Aluminium step wedge of ten, 5mm-thick steps was X-rayed with a Fuji CR system together with a knee phantom (3M) at various energy and Fuji processing settings. Automatic detection of the steps by means of the Hough transform was used to assess optimum CR settings. Background variation due to the anode Heel effect was evaluated by acquiring an “empty field” X-ray at different energy settings and with copper filtering. The effects of beam hardening were considered with a custom-made phantom which was also used to assess correcting for soft tissue and bone thickness.

X-rays taken at higher energy settings and with wider windowing imaged the widest number of steps (nine) and gave the best accuracy in modelling the step thickness to grey level relationship. Fitting a straight line to the log of the net grey levels gives an excellent model of the data (R2 = 0.99). X-rays of copper sheeting show that automatic histogram analysis is performed by the Fuji CR system, which can have unpredictable effects on aluminium thickness to grey level relationship. Background variation in the anode-cathode direction due to the Heel effect was corrected with a 1D exponential model (R2 = 0.99), allowing position-independent measurements to be obtained. Correcting for bone thickness, soft tissue and beam hardening further improves measurement quality.

Use of step wedge calibration to provide quantitative information on plain X-rays without altering their clinical quality is possible using digital radiography. However, a thorough assessment of the entire X-ray process is necessary to achieve accurate and comparable information.

The dynamic association between the immune system and the skeletal system has recently been appreciated. It has been suggested that cells involved in the inflammatory cascade might modulate the bone fracture repair process. Interestingly a number of studies have demonstrated that ability of the T lymphocyte to affect bone remodelling and health profoundly. For example the presence of T lymphocytes has been shown to increase bone resorption during experimental induced arthritis. We wanted to investigate the role of specific T lymphocytes in fracture repair and required an in vivo model to deplete CD4 and CD8 T lymphocytes selectively.

Method The cell lines of Anti-L3T4 (CD4), Anti-Lyt-2 (CD8) and Anti-phytochrome were obtained from ECACC and produced by Edinburgh University group, Immunosolv. Anti-phytochrome (AFRC MAC 51) antibody was used as the control. To each group of 5 murine models 50ìL of CD4 or CD8 or control antibody was injected ip on days 0, 1, 2, 7, 8, and 9. The body weight and behaviour were measured. On day 20 the spleens were sampled and a single cell suspension was created for each murine model. PE CD8 antibody and FITC CD4 antibody were then added to each sample. Each spleen sample was then cell sorted using the FACS machine.

Results Compared to the control group the murine model injected with CD4 antibody had only 1.14 % of CD4 T cells remaining (mean 2.462 % +/− 0.270). Similarly, the murine models injected with CD8 antibody had only 1.8% of CD8 T cells remaining (mean 1.723 % +/− 1.036).

Conclusion Our results suggest that to investigate the role of T lymphocytes in fracture repair, specific T lymphocytes can be successfully depleted with the repeated use of antibodies.

Physical activity is a key determinant of bone mass and health, however during adulthood and ageing there appears to be a decrease in the ability to respond positively to exercise which is variable between individuals. While exercise is known to protect against the osteopo-rotic process with modest increases in BMD the exact cellular and molecular responses are poorly understood.

We have studied the effect of mechanical stimulation on bone histomorphometric parameters, osteocyte viability and gene expression in human trabecular bone maintained in a 3D bioreactor.

Trabecular bone cores were prepared from femoral head tissue removed from patients undergoing total hip arthroplasty and maintained in the bioreactor system for 3 (n= 4 patients), 7 (n=5 patients) or 28 days (n=1 patient). Cores (n=3 per patient) were either frozen directly on preparation (T0), placed in the bioreactor system and subjected to Mechanical stimulation (3000 μstrain in jumping exercise waveform repeated at 1Hz for 5 minutes daily) or maintained in the bioreactor system with no mechanical stimulation as control. After the experimental period total cell numbers, cell viability and apoptosis were determined in un-decalcified cryosections at specific distances throughout the bone cores by nuclear staining (DAPI), lactate dehydrogenase activity (LDH) and Nick Translation Assay respectively. Consecutive sections were collected and RNA extracted for gene expression analysis.

Mechanical stimulation was shown to increase Bone Formation Rate (BFR) as determined by Calcein label/ distance to bone surface in the 28 day experiment (BFR mcm/day Control 0.01 ± 0.0035 vs Load 0.055 ± 0.0036 p=0.0022). Expression of bone formation markers such as Alkaline Phosphatase and Collagen Type I was shown to increase in all patients however there was an individual variation in the response of Osteopontin to mechanical stimulation as determined by quantitative real time PCR expression analysis. Numbers of viable osteocytes at T0 varied between individual patients however viability was significantly increased and apoptosis decreased in association with mechanical stimulation compared to control in all patient samples examined (p to 0.021). Our data tend to support animal model findings relating to the osteocyte saving effects of exercise and provide an insight into the molecular detail of the exercise response in human bone.

We have used human Embryonic Stem cells (hESC) and human Mesenchymal Stem Cells (hMSC) in rat models of bone repair in order to assess the efficacy of these cells for treatments of trauma and skeletal diseases. Graft survival is considered to be of key importance to efficacy of these treatments. Therefore the aim of this study was to develop a technique for identifying implanted cells in histological preparations without the need for genetic engineering of the implanted cells.

Methods: In our experiments hES and hMSC were pre-differentiated during cell culture towards the osteoblast lineage, and then implanted in a Demineralised Bone Matrix (DBM) carrier into an experimentally created full thickness calvarial bone lesion. The animals were sampled seven days and fourteen days after implantation into either immune deficient (RNU-Foxn1rnu) or immune competent (wild type) Sprague Dawley rats. Fluorescent In Situ Hybridisation (FISH) using whole human genome probes identified the human cells within the host lesion site.

Results: Our results have demonstrated that hESC and hMSC derived cells survive in both immune competent (wild type) and immune compromised (nude) animals for the initial seven days post implantation. On the other hand while both the hESC and hMSC derived cells are capable of surviving for at least 14 days in immune compromised animals they do not survive for this period of time in immune competent animals.

Discussion: It appears that the cell/DBM graft is not rejected within seven days even when exposed to the wild type hosts T cell response. However longer term survival required an immune deficient model that is lacking in a T cell response. This data points to interesting future studies regarding which components of the host response are responsible for xenogenic stem cell implant rejection.

The use of stem cells in tissue engineering has emerged as a promising therapy for the repair of bone and cartilage defects. Targeted delivery of stem cells requires a substrate to maintain the cells at the repair site, as well as to provide the physical cues, such as mechanical strain, for encouraging differentiation and expression of the mature cell phenotype. The strains that will be generated in cells residing on the scaffold is dependent on the scaffold material, as well as both the fibre thickness and the fibre orientation in the scaffold. To encourage uniform bone matrix generation throughout the scaffold, it is desirable that the strain be uniformly distributed and that the internal pore architecture be precisely controlled to maximise media diffusion. This requires an optimised scaffold design and a manufacturing technique that allows for precise control over the scaffold’s internal architecture.

Scaffold architecture was optimised by performing a series of finite element analyses (FEA) on computer aided design (CAD) models of Polycaprolactone (PCL) scaffolds. The mechanical properties of PCL were used to yield an accurate strain profile of scaffolds with different fibre orientations. Having determined the optimal scaffold geometry, PCL scaffolds were manufactured using a fibre deposition technique that yielded three-dimensional objects with this geometry. During manufacture, a PCL solution was extruded into a non-miscible solvent which precipitated out PCL fibres in repetitive layers. Of the geometries tested with FEA, a 90 degree rotation of adjacent layers with a 50% offset of parallel strands was found to provide the optimal strain distribution (60% increase in surface exposed to strain). Histomorphometry was used to assess the exact dimensions of the scaffold produced. Fibre spacing was found to be precisely controlled to 380 +/- 10 microns within the layers and the fibre thickness was controlled to 270 +/- 10 microns.

This demonstrates that FEA can be used to predict the strain distribution of different CAD models and that the fibre deposition solvent extrusion technique can be used to accurately manufacture PCL scaffolds that match the desired architecture.

Aim: To investigate the directed chondrogenic differentiation of human embryonic and adult stem cells in 3D alginate bead culture.

Introduction: Cartilage possesses limited self-renewal potential and current repair of damage due to trauma or disease involves removal of non-load bearing chon-drocytes from a healthy part of the joint, expansion of chondrocytes and subsequent surgery to replace damaged, load-bearing cartilage. We investigated the potential of human embryonic and adult stem cells as an alternative cell source for cartilage repair.

Experimental design: Human embryonic stem cells (hESC) and human adult marrow stromal cells (hMSCs) cells were cultured in alginate in a 3D bead format in control or chondrogenic media over a 21day period. Cells were subsequently released from their matrix for gene expression analysis or fixed within alginate beads and crytostat sections prepared for immunostaining and histology.

Cell types used: H9 human embryonic stem cells, bone-marrow derived hMSCs and HEK293 (human embryonic kidney epithelium cell line, used as a negative control).

Data: H9 and hMSC cells cultured in alginate beads bathed in control media have a denser matrix with no lacunae-like structures compared to those cultured in the presence of chondrogenic media. The presence of chondrogenic media results in a matrix containing cells within lacunae-like structures very similar to those seen in human cartilage. In contrast, HEK293 cells formed large highly cellular clusters which had clearly undergone significant proliferation. As both H9 and HEK293 cells are highly proliferative the reduction in the proliferative potential of the chondrogenic H9 derived cells is consistent with entry into a stable terminally differentiated state.

Immunostaining demonstrated that hMSCs and H9 cells express cartilage specific Collagen II and Collagen X.

Conclusion: 3D culture of adult hMSCs and hESC (H9) in alginate beads has resulted in stable directed differentiation down the chondrogenic lineage. These data point towards the future use of these human cell sources in cartilage repair.

Following hip arthroplasty carried out using the Slooff-Ling impaction grafting technique micro-motion of the acetabular cup is frequently seen within the bone graft bed. In some cases this can lead to gross migration and rotation of the acetabular cup, resulting in failure of the arthroplasty. The movement of the cup is thought to be due to the irrecoverable deformation of bone graft under shear and compressive forces. Previous experimental studies have addressed ways in which the behaviour of the bone graft material may be improved, for example through washing and the use of improved particle size distribution. However there has been a limited amount of research carried out into assessing the behaviour of the acetabular construct in-vivo.

This study presents a 3D finite element model of the acetabular construct and hemi-pelvis following impaction grafting of a cavitory defect. A sophisticated elasto-plastic material model was developed based on research carried out by the group to describe the bone graft bed. The material model includes the non-linear stiffness response, as well as the shear and consolidation yield response of the graft. Loading associated with walking, sitting down, and standing up is applied to the model. Distinct patterns of migration and rotation are observed for the different activities. When compared in a pseudo-quantitative manner with clinical observations results were found to be similar. Walking is found to account for superior migration, and rotation in abduction of the acetabular cup, while sitting down and standing up are found to account for posterior migration, and lateral rotation. The developed 3D model can be used in the assessment of cup designs and fixation devices to reduce the rate of aseptic failure in the acetabular region.

Introduction: Cement pressurisation is key to achieving good cement-bone interdigitation in THR. To obtain adequate pressurisation the medullary canal must be sealed distally using a cement restrictor. The cement restrictor must remain stable in the femoral canal.

Methods: Five different cement restrictors were evaluated, namely the Exeter Cement Plug, Biostop G, Hardinge, Rex CementStop and a preinjected cement plug. The restrictor was deployed in a sawbone that had been reamed to produce a distal flare, based on radiographic measurements. Low viscosity bone cement pressurised using a cement ram connected to a 10bar air supply. An electronic pressure valve increased the pressure in the cement. Cement pressure and cement restrictor displacement were continuously measured. The pressure valve and recording of measurements was controlled by a customised computer package.

Results: The Rex CementStop withstood the greatest pressures (mean 565.8kPa). This was a significantly greater pressure than any of the other cement restrictors (p< 0.001). Pre-injected cement plugs were able to resist the next highest pressures (mean 350.4kPa). They did not displace but leaked cement and were technically difficult to deliver in the distal femur. Cement restrictors that function well above the isthmus were ineffective (Biostop mean 118.7kPa) or could not be deployed below the isthmus (Exeter). The Hardinge recorded a mean 162.3kPa.

Discussion: During pre-operative templating it is important to consider where the cement restrictor will sit in the femur. When the cement restrictor is going to be deployed beyond the femoral isthmus, an alternate method of cement restriction may need to be used. Universal sized plugs (e.g. Hardinge) function poorly in this situation. Press-fit plugs such as Biostop and Exeter are severely compromised when inserted past the femoral isthmus. Pre-injected cement plugs are variable in efficacy. The expandable Rex CementStop reliably occluded the femur, allowing the highest pressures to be generated.

Previous experimental studies of the pelvis have been carried out on cadaveric samples stripped of soft tissue. Investigations of the stress concentrations present in the pelvis due to the application of force through the hip joint have been conducted with the superior iliac crests cast in resin or cement. Thus stress concentrations are observed towards the superior iliac crests, and to some extent the pubic symphysis (these being the areas in which force transfer can occur). Due to the rigid fixing of the pelvis in these experiments, the pelvic bone has become viewed as a ‘sandwich beam’ acting between the sacro-iliac and the pubic joints. Numerical models employing similar fixed conditions have shown good agreement with the experimental studies.

However it is clear that these experiments, and the accompanying computational models are not representative of the in-vivo situation, in which the muscles and ligaments of the pelvis and hip joint provide resistance to movement, and in the case of muscles place additional forces on the pelvis, not addressed in the experimental studies. This study presents a finite element model of the pelvis in which novel techniques have been used to include the pelvic ligaments, and hip joint muscles using realistic attachment areas on the cortex, providing a more realistic comparison to the in-vivo environment. Joint interactions at the pubic symphysis and sacro-iliac joints are also simulated. A fixed boundary condition model is also presented for comparison.

The resulting stress concentrations in the pelvis for single leg stance observed in the in-vivo boundary condition model are dramatically different to those presented in studies in which the pelvis is rigidly fixed in place. The abductor muscles are seen to play a significant role in reducing stress concentrations towards the sacro-iliac joints and superior to the acetabulum, in comparison to fixed boundary condition analyses. Stress reductions away from the acetabulum are also observed in the underlying trabecular bone for the in-vivo boundary condition model. Similar stresses are observed within the acetabular region for the fixed, and in-vivo boundary condition models.

An estimated 10% of patients have problems with fracture healing. Initial studies have revealed that it is likely that both the innate and specific immune systems play a role in fracture repair, but this has not been attributed to particular components, cells or their products. It is known that the functionality of the immune system is impaired with age and this may account for the higher rate of delayed union in elderly patients.

We used a validated mouse model of a reproducible closed tibial fracture. In order to prevent any foreign body inflammatory/immune response no artificial internal fracture fixation was used and instead external support was provided using a Plaster of Paris cast. The role of the specific immune system was studied using an immunodeficient Balb/c SCID (Severe Combined Immuno Deficient) mutant mouse. The SCID mice were matched for age, sex (all males) and weight to the control, wild type Balb/c mice. Mechanical (4 point bending) and radiographic (Radiographs scanned and calculations of callus area, index and density made with image analysis software) measures were used to assess fracture repair at 21 days.

Mechanical measurements revealed an enhancement of fracture healing in the SCID mouse strain compared to the control strain, with stress at yield and Young’s modulus higher in SCID mice than controls. (Stress at yield: 4.2 +/− 0.23MPa in Controls, 7.1 =/− 0.6MPa in SCIDs, P< 0.01; Young’ Modulus: 22.1 +/− 2.99MPa in Controls, 60+/− 9.9MPa in SCIDs P< 0.01). There were no significant differences seen in mechanical properties of unfractured bone between the two strains. Radiographic analysis revealed no significant differences in callus area or index (both measurements of callus size) but callus density was significantly higher (P< 0.01) in the SCID subjects compared to controls (2.6 +/− 0.06E5 Greyscale in SCIDs vs. 2.2 +/− 0.09E5 in controls).

We conclude that an abnormality of the immune system due to either lack of the specific immune system (T and B cells) or an enhancement of the innate system results in increased mineralization, stiffness and strength of fracture healing, and that further investigation might result in novel therapies directed toward avoidance of non/delayed-union.

Bone substitutes have emerged as a promising alternative in surgeries requiring bone grafting, with a large array of materials available for today’s surgeon. Unfortunately, there is currently no definitive method for comparing the potential bone-healing potential of these different materials. We have developed a novel technique for assessing the osteogenic capacity of different bone substitutes in a mechanically-stimulating perfusion bioreactor.

The Zetos(TM) bioreactor system consists of individual flow chambers connected to a low-flow perfusion pump, which recirculates media through samples. The Zetos can be programmed to apply a controlled stress or a controlled strain to each individual sample inside the flow chamber. Since bone formation has been shown to be optimal with short doses of high amplitude strains, test samples were subjected to daily loading corresponding to physiological strain experienced during a jumping exercise (maximum 3000 microStrain).

Three substitute materials representing the range of materials available clinically were tested in the Zetos system; these included collagen, calcium phosphate, and a synthetic polymer. Primary human osteoblasts were seeded onto the substitutes, which were then placed inside the Zetos system and maintained under load or non-load conditions for 14 days. No supplementary osteogenic factors were provided to the cells. The degree of bone formation in the samples was assessed using Von Kossa staining and quantified in terms of the area of new mineral relative to the surface area of the substitute.

No mineralisation was detected in the non-loaded samples. However, in the loaded samples, mineralisa-tion was detected in some of the substitutes. The degree of mineralisation depended on the material: in collagen, an average of 0.22 mm2/mm2 was mineralised; in calcium phosphate, mineralisation averaged 0.0013 mm2/ mm2; but in the loaded polymer samples, no mineralisation was detected.

This indicates that mechanical loading is a sufficient stimulus for bone formation in some materials, even in the absence of other known osteogenic factors. Further, commercial substitutes differ in their ability to support bone formation under conditions of physiological loading. Further development of this technique could allow it to be used as a screening tool for predicting the efficacy of commercial products.

Micro level finite element models of bone have been extensively used in the literature to examine its mechanical behaviour and response to loads. Techniques used previously to create these models involved CT attenuations or images (e.g. micro-CT, MRI) of real bone samples. The computational models created using these methods could only represent the samples used in their construction and any possible variations due to factors such as anatomical site, sex, age or degree of osteopo-rosity cannot be included without additional sample collection and processing. This study considers the creation of virtual finite element models of trabecular bone, i.e. models that look like and mechanically behave like real trabecular bone, but are generated computationally.

The trabecular bone is anisotropic both in terms of its micro-architecture and its mechanical properties. Considerable research shows that the key determinants of the mechanical properties of bone are related to its micro-architecture. Previous studies have correlated the apparent level mechanical properties with bone mineral density (BMD), which has also been the principal means of diagnosis of osteoporosis. However, BMD alone is not sufficient to describe bone micro-architecture or its mechanical behaviour. This study uses a novel approach that employs BMD in conjunction with micro-architectural indices such as trabecular thickness, trabecular spacing and degree of anisotropy, to generate virtual micro-architectural finite element models. The approach permits generation of several models, with suitable porous structure, for the same or different levels of osteoporosity. A series of compression and shear tests are conducted, numerically, to evaluate the apparent level orthotropic elastic properties. These tests show that models generated using identical micro-architectural parameters have similar apparent level properties, thus validating this initial bone modelling algorithm. Numerical tests also clearly illustrate that poor trabecular connectivity leads to inferior mechanical behaviour even in cases where the BMD values are relatively high. The generated virtual models have a range of applications such as understanding the fracture behaviour of osteoporotic bone and examining the interaction between bone and implants.

Morsellised cortico-cancellous bone (MCB) is used extensively in impaction grafting procedures, such as the filling of cavitory defects on the femoral and acetabular sides during hip arthroplasty. Several experimental studies have attempted to describe the mechanical behaviour of MCB in compression and shear, and it has been found that it’s properties can be improved by washing and rigorous impaction at the time of surgery. However their focus has not been on the development of constitutive models that can be used in computational simulation.

The results of serial confined compaction tests are presented and used to develop constitutive models describing the non-linear elasto-plastic behaviour of MCB, as well as its time dependent visco-elastic behaviour. It is found that the elastic modulus, E of MCB increases linearly with applied pressure, p, with E achieving a value of around 30 MPa at a pressure of around 1 MPa. The plastic behaviour of MCB can be described using a Drucker Prager Cap yield criterion, capable of describing yielding of the graft in shear and compression. The time dependent visco-elastic behaviour of MCB can be accurately modelled using a spring and dashpot model that can be numerically expressed using a fourth order Prony series. The role of impaction in reducing subsequent plastic deformation was also investigated. The developed relationships allow the constitutive modelling of MCB in finite element simulations, for example of the acetabular construct following impaction grafting. The relationships also act as a gold standard against which to compare synthetic graft and graft extender materials.

Introduction: In hereditary multiple exostosis (HME) the synthesis of the polysaccharide heparan sulphate (HS) is disrupted. HS-proteoglycans are low affinity receptors involved in fibroblast growth factor signaling. Activation of FGF receptor 3 (FGFr3) on mature chondrocytes leads to growth attenuation rather than stimulation. We tested the hypothesis that in HME chondrocytes with absent or reduced HS-PG synthesis there is impaired response to the FGFr3 ligand and loss of control of chondrocyte proliferation.

Materials and methods: Chondrocytes were harvested from normal growth plate (epiphyseodesis) or HME osteochondroma cartilage cap obtained as surgical discard and cultured to 70% confluence in growth media. Cells were re-plated for experimentation. Growth curves were obtained for cells over a period of 5 days. In addition proliferative responses of healthy and HME chondrocytes were determined after low serum synchronization followed by challenge with FGF 9 (10 and 100ng/ml) and incorporation of BrdU for 2hours every two hours over a twenty eight hour period. Using these techniques it is possible to describe in detail the time dependent entry of cells into S-phase of the cell cycle and compare cell lines and treatment.

Results: Significant differences were observed in the growth characteristics over a five-day period (p< 0.05). Under baseline growing conditions the chondrocytes derived from osteochondroma had a more rapid doubling time when compared with the normal growth plate chondrocyte (2.6+/− 0.6 vs 4.9+/−1.0, p< 0.05). In response to incubation with FGF-9 cells from normal growth plate have a lower peak proportion of cells entering the s-phase than with media alone (7% vs 25%). This inhibition is not observed in chondrocytes from osteochondroma.

Conclusions: It would appear that osteochondroma chondrocytes are resistant to the normal regulatory effect of FGF-9 on cell proliferation. The differential response to FGF may be responsible for the growth differences observed both in-vitro and in-vivo.

A descriptive study of osteoporotic fractures and the evaluation of the relative risk of hip fracture following a minor fracture were done on 2.5 million individuals from 1980 to 1997. People aged forty-five years old and older have a risk for hip fracture after a minor fracture of 2.3–17.3 time the risk of people without previous fracture. Given the availability of pharmaceuticals that decrease the fracture risk dramatically within the first 18 months of therapy, the average four to six years time between minor and hip fracture represents a perfect window of opportunity for preventive treatment.

Osteoporotic fractures, especially hip fractures, represent a major health problem in terms of morbidity, mortality and cost. Since the availability of new treatments for osteoporosis, a better understanding of the disease is needed to define the indications for treatment.

A descriptive study of osteoporotic fractures and the evaluation of the relative risk of hip fracture following a minor fracture were done on a population aged fortyfive years old and older from 1980 to 1997 (2.5 million individuals).

During the follow-up period, 220,120 fractures (hip, wrist, proximal humerus and ankle) were recorded. Wrist fractures were the most frequent (42.2%) followed by hip fractures (32.5%). Although the proportions of fracture sites were similar for both sexes, 75% of the fractures occurred in females. The mortality rate 1 year after a hip fracture is increased by 14–27% for men and 9–13% for women. Men and women aged fortyfive years old and older have a risk for hip fracture after a humerus or a wrist fracture of 2.3–17.3 time the risk of people without previous fracture. The average time between a wrist or humerus fracture and a hip fracture was four to six years.

Wrist and humerus fractures represent a major risk for future hip fracture. Given the availability of pharmaceuticals that decrease the risk of hip fracture dramatically within the first eighteen months of therapy, the interval between minor and hip fracture represents a perfect window of opportunity for preventive treatment to decrease the risk of future hip fracture.

Autologous osteochondral cylinder transfer is a treatment option for small articular defects, especially those arising from trauma or osteochondritis dissecans. There are concerns about graft integration and the nature of tissue forming the cartilage-cartilage bridge. Chondrocyte viability at graft and recipient edges is thought to be an important determinant of quality of repair. The aim was to evaluate cell viability at the graft edge from ex vivo human femoral condyles, after harvest using conventional technique. With ethical approval and patient consent, fresh human tissue was obtained at total knee arthroplasty. Osteochondral plugs were harvested using the commercially available Acufex 4.5mm diameter mosaicplasty osteotome from regions of the lateral femoral condyle (anterior cut) that were macroscopically non-degenerate and microscopically non-fibrillated. Plugs were assessed for chondrocyte viability at the graft edge using confocal laser scanning microscopy (CLSM), fluorescent indicators and image analysis. The central portions of the plugs remained healthy, with > 99% cell viability (n=5). However, there was substantial marginal cell death, of thickness 382 ± 68.2 microm in the superficial zone (SZ). Demi-plugs were created by splitting the mosaicplasty explants with a fresh No. 11 scalpel blade. The margin of SZ cell death was 390.3 ± 18.8 microm at the curved edge of the Acufex, significantly (Mann-Whitney; P= 0.0286; n =4) greater than that at the scalpel cut (34.8 ± 3.2 microm). Findings were similar when the cartilage was breached but the bone left intact. In time-course experiments, the SZ marginal zone of cell death after Acufex harvest showed no increase over the time period 15 minutes to 2 hours. Mathematical modelling of the mosaicplasty surface shows that cell death of this magnitude results in a disturbing 33% of the superficial graft area being non-viable. In conclusion, mosaicplasty, though capable of transposing viable hyaline cartilage, is associated with an extensive margin of cell death that is likely to compromise lateral integration. There would appear to be considerable scope for improvement of osteochondral transplant techniques which may improve graft-recipient healing and clinical outcomes.

Measuring strain in biological specimens has always been inherently difficult due to their shape and surface properties. Traditional methods such as strain gauges require contact and therefore have reinforcing effects, also the surface preparation can be time consuming and if proper fixation is not achieved the results will be inaccurate. Using a non contact method to measure strain such as photogrammetry has several advantages. The strain over the whole surface of a specimen can be mapped, depending on the field of view of the camera used. It has a large dynamic range, from microns to millimetres which can be decided upon at the post processing stage. Specimens can be tested to destruction without damaging any measurement equipment. Also there is considerably less set up time involved between testing different specimens once the system is in place. We aimed to test speckle photogrammetry, a method used in industry and fluid dynamics as a tool for assessing proximal femur fracture stability and repair techniques. A Zwick Roell materials testing machine was used to axially apply a staircase loading pattern to sawbones femora, simulating the load experienced by the femur when standing. Firstly an intact bone was tested then a set of three identical fractures of each of three common fracture configurations were produced by osteotomy. The first femur of each configuration was loaded un-repaired to failure; the remaining two were repaired using common techniques for that particular fracture type then also loaded to failure. The bone and fixation device were covered with stochastic, high contrast paint speckle prior to testing. This speckle pattern was recorded at regular load intervals by a digital camera which was attached to the materials testing machine via a rigid frame to eliminate any camera movement. These images were then transferred to a computer where they were converted to 8 bit bitmap images. Matlab was used to process the data from subsequent images to produce vector and colour maps of the displacements and strains over the entire visible surface of the proximal femur and to show the comparative displacements and strains experienced by the individual bone fragment and the fixation devices. Non contact optical strain measurement has proved itself to be a useful tool in assessing the stability of fractures and the repair techniques of these fractures. Additionally it can also be used to validate finite element models to compare theoretical and experimental results due to the similar data and graphic visualisation outputs which are produced by both techniques.

Introduction: It has been suggested that statins may influence bone turnover via an effect on bone morphogenic protein 2 (BMP-2). While the effect on statins in the prevention of osteoporosis remains controversial there is some evidence that they may exert a significant effect on fracture healing.

Using a newly developed fracture model of the proximal tibia of the rat, the effect of simvastatin on osteoporotic and non-osteoporotic fracture healing was investigated. The fracture model was used as it provided a useful model of metaphyseal fracture healing which is particularly relevant to osteoporotic fracture.

Methods: Four groups of 20 3-month-old female Wistar rats were used. Half underwent ovariectomy (ovx) while the remainder had a sham procedure. 8 weeks later a fracture was created in the proximal tibia of each animal by three point bending. The fractures were supported by a narrow intramedullary k-wire. 20 sham and 20 ovx animals were then fed 20mg/kg simvastatin by gavage for 14 days while the rest received placebo. 10 animals from each group were sacrificed at 2 weeks post surgery while the rest were sacrificed at 4 weeks.

X-rays of the healing fractures were taken. Both the intact and fractures tibiae were then taken for mechanical testing by four point bending.

Results: Six animals (7.5%) were excluded because of fracture comminution (5) or loss of stabilisation (1). There was a similar radiological appearance in all 4 groups at each time point. At two weeks: there was no difference in the mechanical properties of the healing bone between the groups. At 4 weeks the fractured and intact tibiae from the sham animals had an equal ultimate load at failure to their intact tibiae. However, the fractured tibiae from the ovx animals remained weaker (ovx & placebo 68%, ovx & statin 60.5% of ultimate load at failure compared with intact tibia). The difference between the fractures ultimate load in ovx and sham animals was statistically significant (p=0.0105). No difference was seen between the statin and placebo group.

Discussion: This work provides evidence that a metaphyseal fracture in the osteoporotic rat model is able to withstand significantly less load at 4 weeks than a fracture from a sham ovx animal suggesting fracture healing is slower in osteoporotic individuals. Simvastatin at 20mg/kg had no effect on the mechanical properties of normal or osteoporotic fracture healing in this study.

Introduction: Emerging therapies for regenerating skeletal tissues are focused on the repair of pathologically altered tissue by the transplantation of functionally competent cells and supportive matrices. Stem cells have the potential to differentiate into musculoskeletal tissue and may be the optimal cell source for such therapies. In vitro studies have demonstrated the ability of adult bone marrow stromal cells (MSC) and human embryonic stem cells (hES) to generate bone, but little is known regarding their potential to repair bone in vivo. Preclinical studies in animal models will allow investigation into the extent that regenerated tissue resembles functional and healthy tissue, and its potential clinical application.

Aim: To assess whether adult and embryonic stem cells maintained their ability to form musculoskeletal tissues in vivo using diffusion chambers implanted into the peritoneal cavity of nude mice. Currently, ongoing experiments are assessing the use of MSCs and hES cells to regenerate bone in a rodent preclinical model.

Methods: MSC cells and embryoid body-derived H9 hES cells were prepared as previously described (Haynesworth et al Bone 1992; Sottile et al Cloning Stem Cells 2003). Groups of cells were left untreated or pre-treated with osteogenic (OS) media for 5 days. Study 1: Single cell suspensions of untreated or pre-treated cells were injected into diffusion chambers which were implanted intraperitonealy into nude mice and left for 79 days. Study 2: OS pre-treated cells were implanted into an experimentally created full thickness calvarial defect in adult male Wistar rats. The defect area was left empty or filled with demineralised bone matrix (DBM: Allosource®) alone or with DBM/MSCs or DBM/hES composite. Tissues were collected 4 weeks after surgery.

Analysis: Histological and immunochemical techniques were used to evaluate cell phenotypes and the contribution of transplanted cells to tissue repair.

Results: Study 1: Both hES (in 2/3 chambers) and MSC (3/3) cells pre-treated with OS media formed only mineralised bone. No cartilage was detected in these OS pre-treated cells. Untreated hES cells formed both mineralised bone and cartilage within the chambers (2/3). In contrast, untreated MSC cells (3/3) produced no mineralised bone or cartilage. Preliminary analysis demonstrated the absence of any other tissue type in the diffusion chambers. Study 2: Active bone regeneration was observed at the edges of the calvarial defect after 4 weeks, with a high density of cells present within the MSC or hES/DBM composite. No signs of local cellular immunological response were seen.

Summary: OS pre-treatment restricted differentiation towards the osteoblast lineage in both hES and MSC cells indicating successful directed differentiation in vivo. Untreated hES and MSC cells produce a different range of cell phenotypes suggesting that the two cell sources represent cells at a different stage of commitment in a common cell lineage or cells derived from two distinct cell lineages. New bone formation was seen at the site of the calvarial defect in the presence OS pre-treated MSC and hES cells suggesting that these cells may support in vivo bone repair in a preclinical model. Funded by Geron Corporation

Introduction: The concept of cell senescence has been described as the mechanism responsible for the ageing of tissues, that is a finite ability to replicate and produce new tissue. The senescent cell population is separate and distinct from the cells which are undergoing programmed cell death (apoptosis), and those which are necrosing acutely. Cells reaching the senescent state have an increase in β-galactosidase activity, which is detectable using an established technique for soft tissues including fibroblasts and epithelial tissues. Senescence has not previously been investigated in bone. We have investigated this and hypothesise that new bone formed by distraction osteogenesis will have fewer senescent cells than the adult cortical “old” bone.

Methods: Eight New Zealand white rabbits underwent application of a M100 Orthofix external fixator to the tibia and creation of a mid-diaphyseal osteotomy, using a hand saw. After a seven day latency period, distraction was commenced (0.5mm twice daily) to twenty percent lengthening. After 3 weeks consolidation, the tibae were harvested for histological analysis.Senescent Staining:The sections were stained using a technique described by Faragher, using an X-gal based stain. Sections were incubated for 16 hours at 37 degrees centigrade before counter staining with DAPI. Sections underwent histological analysis and total cell and senescent cell counts performed.

Results: Surprisingly, large numbers of cells within the bone regenerate stained for cell senescence. A mixture of multinucleate and mononucleate cells were present. The location and appearance of the multinucleate cells prompted the use of TRAP staining. This provided support for these cells being osteoclasts.

Discussion: Previously, a high percentage of apoptotic cells and a high rate of cell division has been reported in bone regenerate. The surprisingly high numbers of cells within the newly formed bone staining positively for senescence suggest that there may also be a high senescent cell population. Alternatively, the positive TRAP staining may indicate that the stain is less specific than reported and may be staining osteoclasts and mature macrophages within the bone regenerate.

Introduction: Tibial component loosening is a common mode of failure in modern total knee arthroplasty and is thus a common cause for revision knee surgery. Direct bone ingrowth of press fit knee prosthesis has been deemed an important prerequisite for long-lasting implant fixation and thus clinical success in both primary and revision TKA whether for cemented or uncemented stems. To achieve good long term biological stabilization, initial secure mechanical stability, (i.e. minimising tibial tray and stem motion with respect to the tibia,) is vital. A lack of initial stability can lead to resorption of bone at the implant-tissue interface and can consequently result in loosening and failure of the prosthesis. Obtaining adequate tibial fixation is difficult in revision patients as often there is insufficient bone stock in the proximal tibia. A longer stem is often recommended with revision surgery as a central stem should guide the migration of the tibial component so that it occurs predominantly along the vertical axis, thus minimising the risk of recurrent malalignment and loosening due to tilting of the tibial tray. It is also thought that the presence of a third rigid peg helps to reduce inducible displacements by anchoring the new implant in robust cancellous bone. However there is no consensus on the length of central stem should be to achieve the best load transfer and fixation and although the use of long stems on the tibial component is advocated, in revision TKA involving bone grafting and augmentation. The effect of the tibial stem length in other cases has received contradictory evaluations. This research deals with an experimentally evaluate the effect that central stem lengths on the initial micromotion of the tibial tray in two revision tibial defects. This is being investigated by measurement of the bone-implant interface motion of the tibial stem.

Method: Composite bones were resected with an extramedullary jig. Three common revision defects were compared 1) no defect requiring no repair(primary); 2) T1 defect requiring bone impaction grafting; 3) T2A requiring augmentation. Three stem configurations were analysed in conjunction with these defects 1) no stem; 2) short 40mm stem; 3) long 80mm stem. Four LVDTs were positioned anteriorly, posteriorly, medially and laterally around the tray and were used to measure the movement of the tibial tray with respect to the tibia. The bones were potted and subjected to axial loading simulating 1– 6 times body weight for 3500 cycles at 1 Hz.

Results: The longer stemmed press fit implants were associated with slightly higher levels of micromotion compared to the “no stem press fit” trays in the primary and T2A defects. This could be due to the fact that cutting errors are accentuated by a longer stem and can cause increased levels of posterior lift off. For bone impaction grafting it seems that a stem sufficiently long to by-pass the defect should be used. The proximal surface cemented trays presented more stable fixation with the inducible displacement between the no stem and stemmed groups being negligible. Subsidence of the tibial tray was reduced marginally by using a longer stem.

If an arthroplasty patient presents with wound breakdown, sinus formation or a hot, red joint the diagnosis of infection is straightforward. However, most total joint replacement (TJR) infections are difficult to distinguish from aseptic loosening. It is imperative to know if a painful TJR is infected to plan appropriate management.

In this prospective study of 204 patients we analysed the diagnostic accuracy of various tests for infection: Inflammatory Markers (CRP/ESR); Aspiration Microbiology; and the Polymerase Chain Reaction (PCR) – a novel technique in this situation. We used international criteria as the gold standard for infection, applied at the time of revision surgery. Any of – a sinus; frank pus in the wound; positive intra-operative microbiology; positive histology – classified the patient as infected. The sensitivity (Sens), specificity (Spec), positive predictive value (PPV) and negative predictive value (NPV) of each test were calculated.

52 patients with an original diagnosis of inflammatory arthritis were excluded, as histology may be inaccurate. The results for the remaining 152 patients are: CRP > 20mg/l: Sens 77%; Spec 76%; PPV 49%; NPV 92%. ESR > 30 mm/hr: Sens 61%; Spec 86%; PPV 57%; NPV 87%. Aspiration Microbiology: Sens 80%; Spec 83%; PPV 71%; NPV 88%. PCR: Sens 71%; Spec 78%; PPV 43%; NPV 89%.

Few patients with negative CRP/ESR were found to be infected; if positive, there was a 50/50 chance that the joint was infected. Positive aspiration microbiology was associated with underlying infection 3 times out of every 4, and negative results were correct 9 times out of 10. PCR was no more accurate than existing tests.

All patients with painful TJR’s should have inflammatory markers checked – if negative the clinician can be relatively reassured that the implant is not infected. If positive or suspicion remains, further investigation should be undertaken. Joint aspiration for microbiology is currently the best available second line investigation.

Introduction If an arthroplasty patient presents with wound breakdown, sinus formation or a hot, red, painful joint replacement the diagnosis of infection is relatively straightforward. However, most total joint replacement (TJR) infections present in an indolent fashion and are impossible to distinguish from aseptic loosening. It is imperative to know if pain in a TJR is due to infection to plan appropriate further management.

Methods In this prospective study of 204 patients we analysed the diagnostic accuracy of various tests for infection in the setting of TJR: Inflammatory Markers (CRP/ESR); Aspiration Microbiology; and the Polymerase Chain Reaction (PCR) – a novel technique in this situation. We used internationally agreed criteria as the gold standard for infection. The patient was deemed to be infected if any of the following were found at the time of revision surgery: a sinus; frank pus in the wound; positive microbiology or positive histology on intra-operative specimens. The sensitivity (Sens), specificity (Spec), positive predictive value (PPV) and negative predictive value (NPV) of each test were calculated.

Results 52 patients with an original diagnosis of inflammatory arthritis were excluded, as histology may be inaccurate. Their results have been presented elsewhere. The results for the remaining 152 patients are: CRP > 20mg/l: Sens 77%; Spec 76%; PPV 49%; NPV 92%. ESR > 30 mm/hr: Sens 61%; Spec 86%; PPV 57%; NPV 87%. Aspiration Microbiology: Sens 80%; Spec 83%; PPV 71%; NPV 88%. PCR: Sens 71%; Spec 78%; PPV 43%; NPV 89%.

Findings and Conclusions Only a few of the patients with negative inflammatory markers later turned out to be infected. If the inflammatory markers were positive, there was roughly a 50/50 chance that the joint was infected. Positive aspiration microbiology was associated with underlying infection approximately 3 times out of every 4, and negative results were correct 9 times out of 10. PCR was no more accurate than existing tests.

We recommend that all patients with painful TJRs have inflammatory markers checked as a screening test – if negative then the clinician can be relatively reassured that the implant is not infected. If positive, further investigation should be undertaken. Joint aspiration for microbiology is currently the best available second line investigation.

Introduction: Diminished adult stature is a key feature of Hereditary Multiple Exostoses (HME). Current debate on the pathogenesis of skeletal abnormalities in HME centres on whether there are ‘field-change’ effects which might retard bone-growth, or whether exostoses themselves distort normal bone development locally. The latter theory allows for surgical excision of exostoses to improve prospects for local normal bone development whereas the former does not. No study has previously investigated patterns of height disturbance in HME. Such an analysis in a cohort of children and adults with HME may provide evidence for or against either pathogenesis theory, and throw light on the chance of success of lower limb surgery in improving final height.

Methods: Between 1996 and 2000, 172 individuals from 78 families with HME had clinical measurement of standing height and leg length (anterior superior iliac spine to medial malleolus. 71 were skeletally immature (1st and 2nd decades). Surgical intervention in anatomical areas affecting stature (lower limb, pelvis and spine) were recorded. Centile heights were calculated from Tanner Whitehouse charts.

Results: 25/172 (15%) exhibited severe short stature (< 3rd centile height). Overall, Statural retardation was not apparent up to age 10; thereafter progressive diminution in centile height was recorded (figure 1). Before age 10, 25/37 (68%) were over the 50th centile. Beyond this age, 98/35 (73%) were less than the 50th centile (X2=22.42, p< 0.001). 101 patients who had surgery did not achieve a greater stature than those who had not. In the normal population lower limb contribution to height increases with age, whereas in HME it remains static suggesting that the retardation of stature seen between ages 10 and 20 in HME is mainly due to lower limb, not spinal growth retardation. Leg length discrepancy of > 1% of centile height was seen in 35/167 (21%), encompassing all age groups without significant difference.

Discussion: The pattern of height retardation observed in this study is consistent with a progressive linear disturbance which is not apparent in early childhood, but progresses significantly in the second decade. Overt spinal exostoses are rare; and the spine’s contribution to growth retardation in HME appears be far less than that due to the lower limb. Although the genetics of HME allow for a field-change effect as well as a local osteo-chondroma effect, these results reinforce the possibility that solutions to severe short stature in HME may be achieved through lower limb surgery.

We investigated the use of PCR (the Polymerase Chain Reaction) to detect the presence of infection in a group of patients undergoing revision arthroplasty for loose TJR (total joint replacement), compared to internationally agreed criteria used as the ‘gold standard’ for infection.

We prospectively tested samples taken from 108 patients undergoing revision arthroplasty (76 hips, 32 knees). Antibiotics were omitted prior to obtaining samples. DNA was extracted by 2 methods – a previously published technique (reference) and a commercial extraction kit (Qiagen^®). PCR involved amplification of an 882 base pair segment of the universal bacterial 16S RNA gene. During revision arthroplasty multiple specimens were taken from around the joint for microbiological and histological examination and the presence or absence of pus was noted. The patient was deemed to be infected if one of the following criteria was found: presence of a sinus pre-operatively; 2 or more intra-operative cultures positive for the same organism; an acute inflammatory response on histology; pus in the joint at revision.

Using the published DNA extraction technique PCR had a sensitivity of 50%, specificity of 93%, positive predictive value of 67% and negative predictive value of 88%. Using commercial extraction the sensitivity improved to 60%, specificity to 98%, positive predictive value to 90% and negative predictive value to 90%.

The previous report stated that PCR had a high sensitivity but a low specificity for detecting low grade infection. However, when using the published technique we found the opposite results – a moderate sensitivity and a high specificity. Introduction of a new DNA extraction technique improved the sensitivity. The refined PCR technique had a high accuracy, but further work is needed to improve sensitivity before we would recommend this method for routine clinical use.

Detection of infection in total joint replacements (TJR) is notoriously difficult. Ideally the diagnosis should be known before revision arthroplasty is undertaken. The level of C-reactive protein (CRP) is one readily available test. Sanzen et al. reported sensitivity of 78% and specificity of 100% for CRP in distinguishing infection in 23 infected TJRs and 33 non-infected TJRs undergoing revision, using a cut off of 2mg/dl¹. However, they used only intra-operative cultures as the standard to compare the CRP against. We have analysed the reliability of CRP to diagnose infection pre-operatively in a group of patients undergoing revision arthroplasty, using the following criteria as the reference standard for infection: 2 or more intra-operative cultures positive for the same organism; presence of acute inflammatory response on histology; presence of pus in the joint at revision (1/3 positive indicates true infection), as described by Hanssen et al.²

The results of CRP and the operative investigations of 26 patients undergoing revision arthroplasty (15 hips and 11 knees) were studied prospectively. In our unit CRP is assayed in mg/dl serum by an automated machine. During revision arthroplasty, multiple specimens were taken from around the joint for microbiological and histological examination. Microbiological cultures were carried out on solid media and broth in aerobic and anaerobic conditions. Histological analysis assessed the level of neutrophils present in the tissue. The presence or absence of pus was noted. The results were analysed graphically and a cut off level of CRP was then chosen for analysis of reliability.

Thirteen patients were infected and 13 were not. Eleven of the 13 infected patients had a CRP greater than 2 mg/dl, and 10 of the 13 non-infected patients had a CRP less than 2 mg/dl. Using 2 mg/dl as a cut off, CRP had a sensitivity of 85% and a specificity of 77%. If 4mg/dl is taken as the threshold for infection, then CRP is 100% specific but only 61% sensitive.

CRP is a useful investigation in the diagnosis of infection in joint replacements. However we have shown that a cut off of 2mg/dl is not 100% specific for non-infected patients. Increasing the threshold improves the specificity, but reduces the sensitivity. Unfortunately there is no single investigation that is 100% accurate in this setting. CRP results must be interpreted in the light of the clinical picture and other investigations. These patients are part of an ongoing study to identify the most reliable criteria for diagnosing the presence of infection in total joint replacement.

Pre-revision detection of infection in failed total joint replacements (TJR) is essential to allow appropriate management planning. Unfortunately, low-grade infection is often difficult to detect. The use of molecular biology may offer increased sensitivity in this setting. We have analysed the use of the Polymerase Chain Reaction (PCR) to diagnose infection in pre-operative aspirates in a group of patients undergoing revision arthroplasty. We prospectively tested 50 aspirates in 50 patients with failed TJR (34 hips and 16 knees). Antibiotics were omitted for 2 weeks prior to aspiration. The aspirate was sent for microbiological culture in aerobic and anaerobic conditions. An aliquot was retained for PCR analysis which involved DNA extraction then amplification of an 882 base pair segment of the Universal 16S RNA gene. In 33 patients who subsequently underwent revision arthroplasty multiple specimens were taken from around the joint for microbiological and histological examination and the presence or absence of pus was noted. The patient was deemed to be infected if one of these criteria was found: 2 or more intra-operative cultures positive for the same organism; an acute inflammatory response on histology; pus in the joint at revision ¹.

PCR was positive in 29 cases. Aspiration microbiology was positive in 13 cases. Of the 33 cases revised, 15 patients were deemed to be infected using the previously established criteria, described above. Compared to preoperative aspiration microbiology PCR had a sensitivity of 92% and specificity of 54%. Compared to the published criteria for infection, PCR was 93% sensitive and 61% specific. If rheumatoid cases are excluded the specificity improves to 71%.

It was concluded that PCR has the ability to amplify very small amounts of target DNA. The apparently high false positive rate compared to aspiration microbiology may indicate that PCR is picking up DNA from contaminating or non-viable organisms (treated or phagocytosed), giving poor specificity. However, microbiology is known to have poor sensitivity on pre-operative aspiration samples, and some of the microbiology results may be false negative. Compared to the criteria for infection after revision our results for PCR are more encouraging, especially for non-rheumatoid patients. These patients are part of an ongoing study to identify the most reliable criteria for pre-operative diagnosis of infection in total joint replacement.

Atrophic non-unions are usually attributed to impaired blood supply but the events that lead to atrophic non-union remain poorly understood. Recent studies^1,2 have shown that vascularity is not reduced in established non-unions but these studies have not examined vascularity at an early stage. The aims of this study were to: 1) develop and validate a clinically relevant small animal model of atrophic non-union and 2) test the hypothesis that the vessel density of atrophic non-unions reaches that of normal healing bones but at a later time point.

Twenty eight adult female Wistar rats underwent application of a novel circular frame external fixator to the right tibia under general anaesthesia. The fixator construct was standardised, with eight needles that were drilled through the skin into the proximal and distal metaphyses of the tibia. An osteotomy was performed with a 1mm burr under irrigation. The periosteum was removed on 14 of the 28 animals using a scalpel and the intramedullary canal was curetted. Both insults were performed proximally and distally for a distance equivalent to 1 diameter of the tibia. A 1mm gap was introduced at the osteotomy site and the wound was closed. Once the animal had recovered it was allowed unrestricted weight bearing. Anteroposterior X rays were performed every 2 weeks. Animals were killed at 1, 3, 8 and 16 weeks. Callus areas were measured from X rays using an image analysis system. The average callus area was calculated for each rat every 2 weeks as an indicator of callus production. Specimens were fixed, decalcified, embedded in paraffin wax and 6 ìm sections were stained with H& E. Vascularity was assessed immunohistochemically with monoclonal antibody against smooth muscle actin. The total number of blood vessels in the interfragmentary gap was counted.

At 8 and 16 weeks post-osteotomy all animals where stripping and curetting had been performed went on to an atrophic non-union. All animals where this was not performed went on to unite successfully. Histological observations support these radiological findings. Significantly less callus formed in the non-unions than in those that united. There were significantly fewer vessels in the non-unions at week 1 compared to the controls but, by 8 weeks the blood vessel density in the established atrophic non-unions had reached the same level as the vessel density during normal healing.

An atrophic non-union model that closely resembles the clinical situation has been developed and validated in rats. The results support the hypothesis that the number of vessels in atrophic non-unions reaches the same level as in those that unite but at a later time point. It is concluded that diminished vessel density within the first 3 weeks may prevent fractures from uniting.

To identify if disease severity and cancer-risk might depend on genotype in Hereditary Multiple Exostoses (HME).

The discovery that the EXT family of tumour suppressor genes is responsible for Hereditary Multiple Exostoses (HME) now enables correlation of clinical features with genetic defects. Genetic epidemiological studies, such as this, may provide additional data of use to the clinician. In most population-based HME cohorts, the incidence of sarcomatous degeneration has been estimated as 1–5%. This is not high, but occurs at a younger age (on average 2–3 decades younger) than chondrosarcoma in the general population. Genetic stratification might allow a very high-risk subgroup to be identified, within which surveillance for neoplastic change in osteochondromas could be concentrated.

In a pilot study, 29 affected individuals from 17 families with HME were screened for EXT mutation, with mutations identified in 12 families. Pedigrees were obtained and a complete assessment of disease severity made. We have since expanded this cohort; a further 71 affected individuals from 34 families with HME have provided detailed pedigree data and undergone a simple clinical examination to assess number of palpable osteo-chondromas. EXT mutation was assessed by means of fluorescent single-strand conformational polymorphism (f-SSCP) screening, followed by sequencing analysis.

Validation of clinical examination : In those who underwent radiographic examination for clinical purposes, number of palpable osteochondromas correlated strongly with number seen on radiographs at 146 anatomical sites (r= 0.814, p< 0.001), validating the usefulness of clinical examination in a population analysis, and negating the need for a radiographic skeletal survey in individuals at risk from malignant change.

The observation that osteochondromas are more frequent in patients with EXT1 than EXT2 mutations is an important message in genetic counselling. If disease severity and cancer risk is greater in individuals with EXT1 mutation, screening for neoplastic change might be targeted on this group, in which lifetime risk of malignant change in osteochondromas could be increased to between 5% and 10%.

It has been shown that the bone, nerve, tendon, and muscle can generate new tissue when a leg is lengthened. In this study we have examined the muscles to see whether the proliferative response occurs uniformly along the fibres or whether it is a disproportionate occurrence, and also to see whether the muscles of animals of different age responded differently.

In five adult (more than 25 weeks) and five young (8 to 9 weeks) New Zealand White rabbits, a mid-diaphyseal tibial osteotomy was created and stabilised with an Orthofix (M-100) external fixator. After seven days, lengthening was carried out at a rate of 1.6 mm/day until a 20% increase in the tibial length had occurred. One hour prior to sacrifice, all of the animals were injected with bromodeoxyridine (BrdUrd, 40mg/kg).

Proliferative response of muscle tissue was assessed by measuring the positive staining index (PSI) of BrdUrd in a two-step indirect immunohistochemistry using the monoclonal antibody Bu20a. We accomplished this staining in transverse sections (between the proximal and middle third, and between the middle and distal third of the muscle belly) and in longitudinal sections along the proximal, middle and distal third of the myotendinous junction (MTJ) of the lengthened flexor digitorum longus muscle belly. The opposite limb was used as a control for each animal.

All of the muscles showed a proliferative response that was significantly higher on the experimental side. There was no difference between the PSI of the proximal transverse sections and the distal transverse sections. The young animals demonstrated significantly increased PSI in all sections compared with the adult animals (immature distal transverse section PSI: 4.91%; mature distal transverse section PSI: 1.67%). The PSI of the longitudinal sections of MTJ showed significantly higher values than in the muscle belly (PSI at the MTJ in adults: 5.23%; PSI at the MTJ in the young: 13.2 %). The PSI result was increased at the distal third of the MTJ in mature and immature rabbits (p0.05).

The muscles show a proliferative response to elongation forming new muscle tissue. The proliferative reaction to lengthening is far greater in the muscles of growing animals compared to adults. The myotendinous junction demonstrates much more intensive proliferative activity than the muscle belly. The distal third of the myotendinous junction shows the highest PSI results. The results of this study help to interpret the results of the animal model for clinical studies and also indicate an advantage in carrying out lengthening on young individuals.

During fracture repair, a number of growth factors and cytokines are present at elevated levels at the fracture site such as Transforming Growth Factor Beta (TGF-), Fibroblast Growth Factor (FGF) and Platelet Derived Growth Factor (PDGF). The aim of the study was to investigate the presence of these growth factors in healing fractures and fracture non-unions, in order to test the hypothesis that atrophic non-unions express a lower level of growth factors than hypertrophic non-unions and healing fractures.

Biopsies were taken from the fracture site of 23 patients (mean age 46) with uninfected non-unions, 12 patients with hypertrophic (mean 13.8 months after fracture) and 11 patients with atrophic (mean 16.5 months after fracture). A comparison group of biopsies from early fracture callus (one to four weeks after fracture) in five patients with healing fractures was also included. Five-micron paraffin sections were immunohistochemically stained for TGF-, FGF-II and PDGF. Growth factors were then assessed in six different cell types.

Fibroblasts, endothelial cells and macrophages were found to express TGF-, FGF-II and PDGF in all three-fracture groups. Osteoblasts, osteoclasts and chondrocytes were not present in the healing fracture group. The growth factor expression in osteoblasts, osteoclasts and chondrocytes in the non-union groups were found to be variable, however, the expression of these growth factors appeared to be less in the atrophic non-unions than hypertrophic non-unions.

The expression of these growth factors was found to be less in the atrophic non-union group than the hypertrophic non-union group in osteoblasts, osteoclasts and chondrocytes. These results may have relevance for new therapies that can be aimed at delivering growth factors to treat fracture non-unions. By further investigation of the differential expression of these growth factors it may be possible to determine which factors are likely to stimulate fracture healing.

We used an experimental rabbit model of leg lengthening to study the morphology and function of muscle after different distraction rates. Lengthening was in twice-daily increments from 0.4 to 4 mm per day. New contractile tissue formed during lengthening, but some damage to the muscle fibres was seen even at rates of less than 1 mm per day; abnormalities increased with larger rates of lengthening. There was proliferation of fibrous tissue between the muscle fibres at distraction rates of over 1 mm per day. Active muscle function showed adaptation when the rate was 1.0 mm per day or less, but muscle compliance was normal only after rates of 0.4 mm per day. Muscle responded more favourably at rates of distraction slower than those shown to lead to the most prolific bone formation. At present the rate of distraction in clinical practice is determined mainly by factors which enhance osteogenesis. Our study suggests that it may be advisable to use a slower rate of elongation in patients with poor muscle compliance associated with the underlying pathology; this will allow better accommodation by the contractile and connective tissues of the muscles.

Of 1197 renal transplant recipients on the Oxford Transplant Programme, 25 (2%) needed arthroplasties for painful osteonecrosis of the hip. Nine of them had bilateral operations, giving a total of 34 primary total hip replacements (THR). The mean time from onset of symptoms to THR was 2.4 years and from transplantation to THR 5.1 years. The mean follow-up was 5.1 (1 to 14) years. THR relieved the pain in all the patients, but survival analysis indicated a lower survival rate than is usual for primary THR. There were eight major complications. One graft-related problem, early acute tubular necrosis, resolved rapidly after immediate treatment. One patient developed deep infection at 3.5 years after THR which settled with conservative treatment. Five hips developed aseptic loosening requiring revision arthroplasty at a mean of 8.8 years' follow-up. One patient had a non-fatal pulmonary embolism. THR is the treatment of choice for patients with painful osteonecrosis of the hip after renal transplant, but has higher rates of both early and late complications. Surgery should be performed in close association with a renal transplant unit.

We measured the driver reaction times of 40 patients before total knee replacement (TKR) and 4, 6, 8 and 10 weeks after operation. The ability to perform an emergency stop was assessed as the time taken to achieve a brake pressure of 100 N after a visual stimulus. There were 18 drivers and 11 non-drivers; the latter had longer reaction times. In drivers, the ability to transfer the right foot from accelerator to brake pedal did not recover to preoperative levels for eight weeks after right TKR and was unchanged after left TKR. Patients should be advised that they should not drive for at least eight weeks after right TKR.

Osteotomy has been used in the treatment of unstable intertrochanteric hip fractures in an attempt to increase the stability of the fracture fragments. We have assessed this stability in a randomised prospective trial on 100 consecutive patients, all having fixation by an AO dynamic hip screw, comparing anatomical reduction with two types of osteotomy. The groups were similar in terms of age, gender, mental test score, and fracture configuration. There were more failures of fixation in the osteotomy groups, and the operations took longer. We found no clear benefit from osteotomy and therefore recommend anatomical reduction and fixation by a sliding hip screw in most cases. Rarely, a fracture configuration which does not allow load-sharing between the fracture fragments and the device may benefit from an osteotomy or the use of an alternative implant.

We performed a prospective, double-blind, randomised, clinical trial to investigate the efficacy of two regimes of rehabilitation for knees with anterior cruciate ligament deficiency (ACLD). Fifty ACLD patients were randomly allocated to one of two treatment groups: a programme of muscle strengthening (T) or a programme designed to enhance proprioception and improve hamstring contraction reflexes (P). An indirect measure of proprioception, the reflex hamstring contraction latency (RHCL), and a functional scoring system were used to record the status of the knee before and after the 12-week course of physiotherapy. Sagittal knee laxity was also measured. There was improvement in mean RHCL and in the mean functional score in both groups after treatment. The improvement in group P was significantly greater than that in group T. There was no significant change in joint laxity after treatment in either group. In both groups there was a positive correlation between improvement in RHCL and functional gain.

The modified Schollner costoplasty is a cosmetic procedure for the correction of rib prominence deformity in scoliosis. We present the results of the procedure in 21 patients who had previously undergone spinal fusion for scoliosis. We found the procedure to be well tolerated without major complications. Objective cosmetic improvement was achieved in all but one case. All but one patient considered the procedure to have been of cosmetic benefit.

We report three cases of thoracic spine translocation without neurological deficit. In each case bilateral pedicular fractures, demonstrated by computed tomography, produced 'floating arches' which account for the sparing of the cord. If computed tomography demonstrates adequate canal dimensions, these patients may be treated conservatively, but the treatment of choice at specialist spinal centres is operative stabilisation.

An area of fibrous dysplasia of bone may undergo rapid enlargement which may be due to either cystic degeneration or malignant transformation. These complications may be clinically and radiologically indistinguishable and, unless both are borne in mind, incorrect management may follow. Magnetic resonance imaging was used in one of our cases and was the only imaging modality to demonstrate the true nature of the condition.