Objectives

We evaluated the accuracy of augmented reality (AR)-based navigation assistance through simulation of bone tumours in a pig femur model.

This aim of this study was to identify common factors in patients with the shortest length of hospital stay following total hip arthroplasty (THA). This would then allow a means of targeting suitable patients to reduce their length of stay.

This was a retrospective cohort study of all patients undergoing primary THA at our institution between September 2013 and August 2014. Demographic data were collected from the patient record. The cohort was divided into those discharged to home within two days of operation and the rest of the THA population. The demographics (age, gender, ASA grade, body mass index (BMI), primary diagnosis, socioeconomic status (Scottish Index of Multiple Deprivation, SIMD and SIMD health domain) were compared between groups. In addition for the early discharge group information on comorbidities, family support at home and independent transport were collected.

The study cohort was 1292 patients. 119 patients were discharged home on the first post-operative day. Those discharged earlier were on average younger (p<0.0001), more likely to be male (p<0.0001) and had a lower ASA grade (p<0.00001). Other demographics did not differ between groups. Patients who were discharged early also appeared to have few comorbidities (Diabetes 5.9%, Cardiac disease 7.6%, Respiratory disease 9%), high levels of family support at home (95%) and high levels of independent transport arrangements (97%).

Factors associated with those patients with the shortest lengths of stay were identified. Such factors could be used to target patients who are suitable for streamlined recovery programmes aimed at early discharge after THA and assist with service planning.

Biological reconstruction techniques after diaphyseal tumour resection have increased in popularity in recent years. High complication and failure rates have been reported with intercalary allografts, with recent studies questioning their role in limb-salvage surgery. We developed a technique in which large segment allografts are augmented with intramedullary cement and fixed using compression plating. The goal of this study was to evaluate the survivorship, complications and functional outcomes of these intercalary reconstructions.

Forty-two patients who had reconstruction with an intercalary allograft following tumour resection between 1989 and 2010 were identified from our prospectively collected database. Allograft survival, local recurrence-free, disease-free and overall survival were assessed using the Kaplan-Meier method. Patient function was assessed using the Musculoskeletal Tumour Society (MSTS) scoring system and the Toronto Extremity Salvage Score (TESS).

The 23 women and 19 men had a mean age of 33 years (14–77). The most common diagnoses were osteosarcoma (n=16) and chondrosarcoma (n=9). There were 9 humerus, 18 femur and 15 tibia reconstructions. At a mean follow-up of 95 months (5–288), 31 patients were alive without disease, 10 were dead of disease and 1 was deceased of other causes. There were 4 local recurrences and 11 patients developed metastatic disease. 5-year local recurrence free survival was 92%, 5-year disease-free survival was 70% and overall survival was 75%. Fourteen of 42 patients (33%) experienced complications: 5 wound healing complications, 4 infections, 2 non-unions, 2 fractures and 1 nerve palsy. Four allografts (9.5%) were revised for complications and 2 (5%) for local recurrence. Mean allograft survival was 85 months (4–288). Mean time to union was 8.2 (3–36) months for the proximal osteotomy site and 8.1 (3–23) months for the distal osteotomy site. The mean score for MSTS 87 was 29.4 (+/− 4.4), MSTS 93 was 83.7 (+/−14.8) and TESS was 81.6 (+/−16.9).

An intercalary allograft augmented with intramedullary cement and compression plate fixation provides a reliable and durable method of reconstruction after tumour resection. Complication rates are comparable to the literature and are associated with high levels of patient function and satisfaction.

Long-term biological fixation and stability of uncemented acetabular implant are influenced by peri-prosthetic bone ingrowth which is known to follow the principle of mechanoregulatory tissue differentiation algorithm. A tissue differentiation is a complex set of cellular events which are largely influenced by various mechanical stimuli. Over the last decade, a number of cell-phenotype specific algorithms have been developed in order to simulate these complex cellular events during bone ingrowth. Higher bone ingrowth results in better implant fixation. It is hypothesized that these cellular events might influence the peri-prosthetic bone ingrowth and thereby implant fixation. Using a three-dimensional (3D) microscale FE model representing an implant-bone interface and a cell-phenotype specific algorithm, the objective of the study is to evaluate the influences of various cellular activities on peri-prosthetic tissue differentiation. Consequently the study aims at identifying those cellular activities that may enhance implant fixation.

The 3D microscale implant-bone interface model, comprising of Porocast Bead of BHR implant, granulation tissue and bone, was developed and meshed in ANSYS (Fig. 1b). Frictional contact (µ=0.5) was simulated at all interfaces. The displacement fields were transferred and prescribed at the top and bottom boundaries of the microscale model from a previously investigated macroscale implanted pelvis model (Fig. 1a) [4]. Periodic boundary conditions were imposed on the lateral surfaces. Linear elastic, isotropic material properties were assumed for all materials. Young's modulus and Poisson's ratios of bone and implant were mapped from the macroscale implanted pelvis [4]. A cell-phenotype specific mechanoregulatory algorithm was developed where various cellular activities and tissue formation were modeled with seven coupled differential equations [1, 2]. In order to evaluate the influence of various cellular activities, a Plackett-Burman DOE scheme was adopted. In the present study each of the cellular activity was assumed to be an independent factor. A total of 20 independent two-level factors were considered in this study which resulted in altogether 24 different combinations to be investigated. All these cellular activities were in turn assumed to be regulated by local mechanical stimulus [3]. The mechano-biological simulation was run until a convergence in tissue formation was attained.

The cell-phenotype specific algorithm predicted a progressive transformation of granulation tissue into bone, cartilage and fibrous tissue (Fig. 1c). Various cellular activities were found to influence the time to reach equilibrium in tissue differentiation and, thereby, attainment of sufficient implant fixation (Fig. 2, Table 1). Negative regression coefficients were predicted for the significant factors, differentiation rate of MSCs and bone matrix formation rate, indicating that these cellular activities favor peri-prosthetic bone ingrowth by facilitating rapid peri-prosthetic bone ingrowth. Osteoblast differentiation rate, on the contrary, was found to have the highest positive regression coefficient among the other cellular activities, indicating that an increase in this cellular activity delays the attainment of equilibrium in bone ingrowth prohibiting rapid implant fixation.

To view tables/figures, please contact authors directly.

The success of a cementless Total Hip Arthroplasty (THA) depends not only on initial micromotion, but also on long-term failure mechanisms, e.g., implant-bone interface stresses and stress shielding. Any preclinical investigation aimed at designing femoral implant needs to account for temporal evolution of interfacial condition, while dealing with these failure mechanisms. The goal of the present multi-criteria optimization study was to search for optimum implant geometry by implementing a novel machine learning framework comprised of a neural network (NN), genetic algorithm (GA) and finite element (FE) analysis. The optimum implant model was subsequently evaluated based on evolutionary interface conditions.

The optimization scheme of our earlier study [1] has been used here with an additional inclusion of an NN to predict the initial fixation of an implant model. The entire CAD based parameterization technique for the implant was described previously [1]. Three objective functions, the first two based on proximal resorbed Bone Mass Fraction (BMF) [1] and implant-bone interface failure index [1], respectively, and the other based on initial micromotion, were formulated to model the multi-criteria optimization problem. The first two objective functions, e.g., objectives f1 and f2, were calculated from the FE analysis (Ansys), whereas the third objective (f3) involved an NN developed for the purpose of predicting the post-operative micromotion based on the stem design parameters. Bonded interfacial condition was used to account for the effects of stress shielding and interface stresses, whereas a set of contact models were used to develop the NN for faster prediction of post-operative micromotion. A multi-criteria GA was executed up to a desired number of generations for optimization (Fig. 1). The final trade-off model was further evaluated using a combined remodelling and bone ingrowth simulation based on an evolutionary interface condition [2], and subsequently compared with a generic TriLock implant.

The non-dominated solutions obtained from the GA execution were interpolated to determine the 3D nature of the Pareto-optimal surface (Fig. 2). The effects of all failure mechanisms were found to be minimized in these optimized solutions (Fig. 2). However, the most compromised solution, i.e., the trade-off stem geometry (TSG), was chosen for further assessment based on evolutionary interfacial condition. The simulation-based combined remodelling and bone ingrowth study predicted a faster ingrowth for TSG as compared to the generic design. The surface area with post-operative (i.e., iteration 1) ingrowth was found to be ∼50% for the TSG, while that for the TriLock model was ∼38% (Fig. 3). However, both designs predicted similar long-term ingrowth (∼89% surface area). The long-term proximal bone resorption (upto lesser trochanter) was found to be ∼30% for the TSG, as compared to ∼37% for the TriLock model. The TSG was found to be bone-preserving with prominent frontal wedge and rectangular proximal section for better rotational stability; features present in some recent designs. The optimization scheme, therefore, appears to be a quick and robust preclinical assessment tool for cementless femoral implant design.

To view tables/figures, please contact authors directly.

Introduction

There is a growing recognition that evaluation should use patient-reported outcome tools and assessments of satisfaction in procedures like total knee replacement. These ensure that the patient's perception of outcome is included in the evaluation. Considering the increasing demands on physical function from the aging population, it is important to evaluate demanding physical activities for the population with end stage arthritis assigned for TKR.

Extracorporeal irradiation of an excised tumour-bearing segment of bone followed by its re-implantation is a technique used in bone sarcoma surgery for limb salvage when the bone is of reasonable quality. There is no agreement among previous studies about the dose of irradiation to be given: up to 300 Gy have been used.

We investigated the influence of extracorporeal irradiation on the elastic and viscoelastic properties of bone. Bone was harvested from mature cattle and subdivided into 13 groups: 12 were exposed to increasing levels of irradiation: one was not and was used as a control. The specimens, once irradiated, underwent mechanical testing in saline at 37°C.

The mechanical properties of each group, including Young’s modulus, storage modulus and loss modulus, were determined experimentally and compared with the control group.

There were insignificant changes in all of these mechanical properties with an increasing level of irradiation.

We conclude that the overall mechanical effect of high levels of extracorporeal irradiation (300 Gy) on bone is negligible. Consequently the dose can be maximised to reduce the risk of local tumour recurrence.

Cite this article: Bone Joint J 2015;97-B:1152–6.

Extracorporeal irradiation and re-implantation of a bone segment is a technique employed in bone sarcoma surgery for limb salvage in the setting of reasonable bone stock. There is neither consensus nor rationale given for the dosage of irradiation used in previous studies, with values of up to 300Gy applied. We investigated the influence of extracorporeal irradiation on the elastic and viscoelastic properties of bone. Bone specimens were extracted from mature cattle and subdivided into thirteen groups; twelve groups exposed to increasing levels of irradiation and a control group. The specimens, once irradiated, underwent mechanical testing in saline at 37°C.

Mechanical properties were calculated by experimental means which included Young's Modulus, Poisson's Ratio, Dissipation Factor, Storage Modulus, Loss Modulus and Dynamic Modulus. These were all obtained for comparison of the irradiated specimens to the control group.

We found there to be a statistically significant increase in Poisson's ratio after increasing irradiation doses up to 300Gy were applied. However, there was negligible change in all other mechanical properties of bone that were assessed. Therefore, we conclude that the overall mechanical effect of high levels of extracorporeal irradiation (300Gy) is minute, and can be administered to reduce the risk of malignancy recurrence.

Extracorporeal irradiation and re-implantation of a bone segment is a technique employed in bone sarcoma surgery for limb salvage in the setting of reasonable bone stock. There is neither consensus nor rationale given for the dosage of irradiation used in previous studies, with values of up to 300Gy applied. We investigated the influence of extracorporeal irradiation on the elastic and viscoelastic properties of bone. Bone specimens were extracted from mature cattle and subdivided into thirteen groups; twelve groups exposed to increasing levels of irradiation and a control group. The specimens, once irradiated, underwent mechanical testing in saline at 37°C.

Mechanical properties were calculated by experimental means which included Young's Modulus, Storage Modulus and Loss Modulus. These were all obtained for comparison of the irradiated specimens to the control group.

There were non-significant negligible changes in all of the mechanical properties of bone that were assessed with increasing dosage of irradiation. Therefore, we conclude that the overall mechanical effect of high levels of extracorporeal irradiation (300Gy) is minute, and can be administered to reduce the risk of malignancy recurrence.

We evaluated an operative technique, described by the Exeter Hip Unit, to assist accurate introduction of the femoral component. We assessed whether it led to a reduction in the rate of leg-length discrepancy after total hip arthroplasty (THA).

A total of 100 patients undergoing THA were studied retrospectively; 50 were undertaken using the test method and 50 using conventional methods as a control group. The groups were matched with respect to patient demographics and the grade of surgeon. Three observers measured the depth of placement of the femoral component on post-operative radiographs and measured the length of the legs.

There was a strong correlation between the depth of insertion of the femoral component and the templated depth in the test group (R = 0.92), suggesting accuracy of the technique. The mean leg-length discrepancy was 5.1 mm (0.6 to 21.4) pre-operatively and 1.3 mm (0.2 to 9.3) post-operatively. There was no difference between Consultants and Registrars as primary surgeons. Agreement between the templated and post-operative depth of insertion was associated with reduced post-operative leg-length discrepancy. The intra-class coefficient was R ≥ 0.88 for all measurements, indicating high observer agreement. The post-operative leg-length discrepancy was significantly lower in the test group (1.3 mm) compared with the control group (6.3 mm, p < 0.001).

The Exeter technique is reproducible and leads to a lower incidence of leg-length discrepancy after THA.

Cite this article: Bone Joint J 2015;97-B:154–9.

High-intensity narrow-spectrum (HINS) light is a novel violet-blue light inactivation technology which kills bacteria through a photodynamic process, and has been shown to have bactericidal activity against a wide range of species. Specimens from patients with infected hip and knee arthroplasties were collected over a one-year period (1 May 2009 to 30 April 2010). A range of these microbial isolates were tested for sensitivity to HINS-light. During testing, suspensions of the pathogens were exposed to increasing doses of HINS-light (of 123mW/cm² irradiance). Non-light exposed control samples were also used. The samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration. Complete inactivation (greater than 4-log₁₀ reduction) was achieved for all of the isolates. The typical inactivation curve showed a slow initial reaction followed by a rapid period of inactivation. The doses of HINS-light required ranged between 118 and 2214 J/cm². Gram-positive bacteria were generally found to be more susceptible than Gram-negative.

As HINS-light uses visible wavelengths, it can be safely used in the presence of patients and staff. This unique feature could lead to its possible use in the prevention of infection during surgery and post-operative dressing changes.

Cite this article: Bone Joint J 2015;97-B:283–8.

Current Department of Health guidelines state that medical personnel should be ‘bare below the elbows’. Critics of this policy have raised concerns over the impact of these dress regulations on the portrayed image and professionalism of doctors. However, the importance of the doctor's appearance in relation to other professional attributes is largely unknown. The purpose of this study was to determine the opinion of patients and their relatives on the importance of appearance and the style of clothing worn by orthopaedic doctors. The secondary aim was to establish how patients would prefer orthopaedic doctors to be dressed.

The study consisted of the administration of a survey questionnaire to 427 subjects attending the orthopaedic outpatient clinics in four hospitals across Scotland. Subjects were asked about the importance or otherwise of various aspects of the doctors’ appearance and responded using a modified Likert 5-point scale. Subjects’ rank preferences for four different styles of doctors’ clothing were also determined. The study was appropriately powered to identify a 0.5 difference in mean rank values with 0.90 power at a = 0.05.

The majority of respondents felt doctors’ appearance was important but not as important as compassion, politeness and knowledge. Only 50% felt that the style of doctors clothing mattered; what proved more important was an impression of cleanliness and good personal hygiene. In terms of how patients would prefer doctors to dress in clinic, the most popular choice proved to be the smart casual style of dress, which conforms with the ‘bare below the elbows’ dress code policy. Indeed, the smart casual clothing style was the highest ranked choice irrespective of patient age, gender, regional or socioeconomic background.

Primary bony tumours of the elbow account for approximately 1% of all osseous tumours. The delayed diagnosis is commonly reported in the literature as a result of lack of clinician familiarity. We present the largest series of primary bone tumours of the elbow in the English literature.

We sought to identify characteristics specific to primary elbow tumours and compare these to the current literature. We discuss cases of misdiagnosis and reasons for any delay in diagnosis. The authors also recommend a collaborative protocol for the diagnosis and management of these rare tumours.

A prospectively collected national database of all bone tumours is maintained by an independent clerk. The registry and case notes were retrospectively reviewed from January 1954 until June 2013. Eighty cases of primary osseous elbow tumours were studied. Tumours were classified as benign or malignant and then graded according to the Enneking spectrum.

There were no benign latent cases in this series. All cases in this series required surgical intervention. These cases presented with persistent rest pain, with or without swelling. The distal humerus was responsible for the majority and most aggressive of cases. The multidisciplinary approach at a specialist centre is integral to management. Misdiagnosis was evident in 12.5 % of all cases. Malignant tumours carried a 5-year mortality of 61%. Benign tumours exhibited a 19% recurrence rate and in particular, giant cell tumour was very aggressive. The evolution in treatment modalities has clearly benefited patients.

Clinicians should be aware that elbow tumours can be initially misdiagnosed as soft tissue injuries or cysts. The suspicion of a tumour should be raised in the patient with unremitting, unexplained non-mechanical bony elbow pain. We suggest an investigatory and treatment protocol to avoid a delay to diagnosis. With high rates of local recurrence, we recommend regular postoperative reviews.

Leg length discrepancy (LLD) can adversely affect functional outcome and patient satisfaction after total hip arthroplasty. We describe a novel intraoperative technique for femoral component insertion.

We aimed to determine if this technique resulted in the desired femoral placement, as templated, and if this was associated with a reduced LLD.

A series of fifty consecutive primary total hip replacements were studied. Preoperative digital templating was performed on standardised PA radiographs of the hips by the senior surgeon. The preoperative LLD was calculated and the distance from the superior tip of the greater trochanter to the predicted shoulder of the stem was calculated (GT-S). Intraoperatively, this length was marked on the rasp handle and the stem inserted to the predetermined level by the surgeon. This level corresponded to the tip of the greater trochanter and formed a continuous line to the mark on the rasp handle. Three independent blinded observers measured the GT-S on the postoperative radiographs. We assessed the relationship between the senior author's GT-S (preoperative) and the observers' GT-S (postoperative) using a Person correlation. The observers also measured the preoperative and postoperative LLD, and the inter-observer variability was calculated as the intra-class correlation coefficient.

There was a strong correlation of preoperative and postoperative GT-S (R=0.87), suggesting that the stem was inserted as planned. The mean preoperative and postoperative LLD were −4.3 mm (−21.4–4) and −0.9 mm (−9.8–8.6), respectively (p<0.001).

This technique consistently minimised LLD in this series. This technique is quick, non-invasive and does not require supplementary equipment.

Purpose

To validate accuracy of transepicondylar axis as a reference for femoral component rotation in primary total knee arthroplasty.

Purpose:

To compare accuracy of transepicondylar axis as a reference for femoral component rotation in primary navigated versus non navigated total knee arthroplasty in severely deformed knees.

Purpose

To assesment of geometric center of knee as a reference for femoral component rotation in primary total knee arthroplasty.

The cement used for hemiarthroplasties by the authors and many other surgeons in the UK is Palacos® (containing 0.5g Gentamicin). Similar cement, Copal® (containing 1g Gentamicin and 1g Clindamycin) has been used in revision arthroplasties. We aim to investigate the effect on SSI rates of doubling the gentamicin dose and adding a second antibiotic (clindamycin) to the bone cement in hip hemiarthroplasty.

We randomised 848 consecutive patients undergoing cemented hip hemiarthroplasty for fractured NOF into two groups: Group I, 464 patients, received standard cement (Palacos®) and Group II, 384 patients, received high dose, double antibiotic-impregnated cement (Copal®). We calculated the SSI rate for each group at 30 days post-surgery. The patients, reviewers and statistician were blinded as to treatment group.

The demographics and co-morbid conditions were statistically similar between the groups. The combined superficial and deep SSI rates were 5 % (20/394) and 1.7% (6/344) for groups I and II respectively (p=0.01). Group I had a deep infection rate 3.3 %(13/394) compared to 1.16% (4/344) in group II (p=0.082). Group I had a superficial infection rate 1.7 % (7/394) compared to 0.58% (2/344) in group II (p=0.1861). 33(4%) patients were lost to follow up, and 77 (9%) patients were deceased at the 30 day end point.

Using high dose double antibiotic-impregnated cement rather than standard low dose antibiotic-impregnated cement significantly reduced the SSI rate (1.7% vs 5%; p=0.01) after hip hemiarthroplasty for fractured neck of femur in this prospective randomised controlled trial.

Infection rates following arthroplasty surgery are between 1–4%, with higher rates in revision surgery. The associated costs of treating infected arthroplasty cases are considerable, with significantly worse functional outcomes reported. New methods of infection prevention are required. HINS-light is a novel blue light inactivation technology which kills bacteria through a photodynamic process. The aim of this study was to investigate the efficacy of HINS-light for the inactivation of bacteria isolated from infected arthoplasty cases.

Specimens from hip and knee arthroplasty infections are routinely collected to identify causative organisms. This study tested a range of these isolates for sensitivity to HINS-light. During testing, bacterial suspensions were exposed to increasing doses of HINS-light of (123mW/cm² irradiance). Non-light exposed control samples were also set-up. Bacterial samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration.

Complete inactivation was achieved for all Gram positive and negative microorganisms

More than a 4-log reduction in Staphylococcus epidermidis and Staphylococcus aureus populations were achieved after exposure to HINS-light for doses of 48 and 55 J/cm², respectively. Current investigations using Escherichia coli and Klebsiella pneumoniae show that gram-negative organisms are also susceptible, though higher doses are required.

This study has demonstrated that HINS-light successfully inactivated all clinical isolates from infected arthroplasty cases. As HINS-light utilises visible-light wavelengths it can be safely used in the presence of patients and staff. This unique feature could lead to possible applications such as use as an infection prevention tool during surgery and post-operative dressing changes.

Infection rates following arthroplasty surgery are between 1–4%, with higher rates in revision surgery. The associated costs of treating infected arthroplasty cases are considerable, with significantly worse functional outcomes reported. New methods of infection prevention are required. HINS-light is a novel blue light inactivation technology which kills bacteria through a photodynamic process. The aim of this study was to investigate the efficacy of HINS-light for the inactivation of bacteria isolated from infected arthroplasty cases.

Specimens from hip and knee arthroplasty infections are routinely collected to identify causative organisms. This study tested a range of these isolates for sensitivity to HINS-light. During testing, bacterial suspensions were exposed to increasing doses of HINS-light of (123 mW/cm² irradiance). Non-light exposed control samples were also set-up. Bacterial samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration.

Complete inactivation (greater than a 4-log reduction) was achieved for all of the clinical isolates from infected arthroplasty cases. The typical inactivation curve showed a slow initial reaction followed by a period of rapid inactivation. The doses of HINS-light exposure required ranged from 118–2214 J/cm² respectively. Gram-positive bacteria were generally found to be more susceptible than Gram-negative.

This study has demonstrated that HINS-light successfully inactivated all clinical isolates from infected arthroplasty cases. As HINS-light utilises visible-light wavelengths it can be safely used in the presence of patients and staff. This unique feature could lead to possible applications such as use as an infection prevention tool during surgery and post-operative dressing changes.