In absence of available quantitative measures, the assessment of fracture healing based on clinical examination and X-rays remains a subjective matter. Lacking reliable information on the state of healing, rehabilitation is hardly individualized and mostly follows non evidence-based protocols building on common guidelines and personal experience. Measurement of fracture stiffness has been demonstrated as a valid outcome measure for the maturity of the repair tissue but so far has not found its way to clinical application outside the research space. However, with the recent technological advancements and trends towards digital health care, this seems about to change with new generations of instrumented implants – often unfortunately termed “smart implants” – being developed as medical devices.

The AO Fracture Monitor is a novel, active, implantable sensor system designed to provide an objective measure for the assessment of fracture healing progression (1). It consists of an implantable sensor that is attached to conventional locking plates and continuously measures implant load during physiological weight bearing. Data is recorded and processed in real-time on the implant, from where it is wirelessly transmitted to a cloud application via the patient's smartphone. Thus, the system allows for timely, remote and X-ray free provision of feedback upon the mechanical competence of the repair tissue to support therapeutic decision making and individualized aftercare.

The device has been developed according to medical device standards and underwent extensive verification and validation, including an in-vivo study in an ovine tibial osteotomy model, that confirmed the device's capability to depict the course of fracture healing as well as its long-term technical performance. Currently a multi-center clinical investigation is underway to demonstrate clinical safety of the novel implant system. Rendering the progression of bone fracture healing assessable, the AO Fracture Monitor carries potential to enhance today's postoperative care of fracture patients.

Local antimicrobial therapy is an integral aspect of treating orthopaedic device related infection (ODRI), which is conventionally administered via polymethylmethacrylate (PMMA) bone cement. PMMA, however, is limited by a suboptimal antibiotic release profile and a lack of biodegradability.

In this study, we compare the efficacy of PMMA versus an antibioticloaded hydrogel in a single- stage revision for chronic methicillin-resistant Staphylococcus aureus (MRSA) ODRI in

sheep. Antibiofilm activity of the antibiotic combination (gentamicin and vancomycin) was determined in vitro. Swiss alpine sheep underwent a single-stage revision of a tibial intramedullary nail with MRSA infection. Local gentamicin and vancomycin therapy was delivered via hydrogel or PMMA (n = 5 per group), in conjunction with systemic antibiotic therapy. In vivo observations included: local antibiotic tissue concentration, renal and liver function tests, and quantitative microbiology on tissues and hardware post-mortem.

There was a nonsignificant reduction in biofilm with an increasing antibiotic concentration in vitro (p = 0.12), confirming the antibiotic tolerance of the MRSA biofilm. In the in vivo study, four out of five sheep from each treatment group were culture negative. Antibiotic delivery via hydrogel resulted in 10–100 times greater local concentrations for the first 2–3 days compared with PMMA and were comparable thereafter. Systemic concentrations of gentamicin were minimal or undetectable in both groups, while renal and liver function tests were within normal limits.

This study shows that a single-stage revision with hydrogel or PMMA is equally effective, although the hydrogel offers certain practical benefits over PMMA, which make it an attractive proposition for clinical use.

Aim

The treatment of chronic orthopedic device-related infection (ODRI) often requires multiple surgeries and prolonged antibiotic therapy. In a two-stage exchange procedure, the treatment protocol includes device removal and placement of an antibiotic-loaded bone cement spacer to achieve high local antibiotic concentrations. At the second stage, further surgery is required to remove the spacer and replace it with the definitive device. We have recently developed a thermo-responsive hyaluronan hydrogel (THH) that may be loaded with antibiotics and used as delivery system. Since the material is bio-resorbable, it does not require surgical removal and may therefore be suitable for use as treatment strategy in a single-stage exchange.

This aim of this study was to evaluate gentamicin sulphate (Genta)-loaded THH (THH-Genta) for treating a chronic Staphylococcus aureus ODRI in sheep using a single-stage procedure.

Injury to the syndesmosis occurs in 10–13% of all operative ankle fractures and there is evidence that both incomplete treatment and malreduction of the syndesmosis can lead to poor clinical outcomes. Much attention has been given to post–operative malreduction documented by computer tomography (CT), however, there is limited data about the intact positioning and relative motion of the native syndesmosis. The aim of this study is to elucidate more detailed information on the position of the fibula in the syndesmosis during simulated weight–bearing in intact state, with sequential ligament sectioning and following two reconstructive techniques.

Fourteen paired, fresh–frozen human cadaveric limbs were mounted in a weight–bearing simulation jig. CT scans were obtained under simulated foot–flat loading (75 N) and in single–legged stance (700 N), in five foot positions: neutral, 15° external rotation, 15° internal rotation, 20° dorsiflexion, and 20° plantarflexion. The elements of the syndesmosis and the deltoid ligament were sequentially sectioned. One limb of each pair was then reconstructed via one of two methods: Achilles autograft and peroneus longus ligamentoplasty. The specimens were rescanned in all 5 foot positions following each ligament resection and reconstruction. Measurements of fibular diastasis, rotation and anterior–posterior translation were performed on the axial cuts of the CT scans, 1 cm proximal to the roof of the plafond.

Multiple measurements were made to define the position of the fibula in the incisura. Clinically relevant deformity patterns were produced. The deformity at the incisura was consistent with clinical injury, and the degree of displacement in all ligament states was dependent on the foot position. The most destructive state resulted in the most deformity at the syndesmosis. Differences between the intact and reconstructed states were found with all measurements, especially when the foot was in external rotation and dorsiflexion. There was no significant difference with direct comparison of the reconstructions.

This study has detailed the motion of the fibula in the incisura and its variation with foot position. Neither reconstruction was clearly superior and both techniques had difficulty in the externally rotated and dorsiflexed foot positions. This study design can serve as a model for future ex–vivo testing of reconstructive techniques.

Introduction

Optimal orthopaedic implant placement is a major contributing factor to the long term success of all common joint arthroplasty procedures. Devices such as 3D printed bespoke guides and orthopaedic robots are extensively described in the literature and have been shown to enhance prosthesis placement accuracy. These technologies have significant drawbacks such as logistical and temporal inefficiency, high cost, cumbersome nature and difficult theatre integration. A radically new disruptive technology for the rapid intraoperative production of patient specific instrumentation that obviates all disadvantages of current technologies is presented.

One of the most challenging complications in orthopedic trauma surgery is the development of infection. Improved infection prophylaxis could be achieved by providing local delivery of antibiotics directly to the tissue-implant interface. Especially implant-associated bone infections caused by antibiotic-resistant pathogens pose significant clinical challenges to treating physicians. Prophylactic strategies that act against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), are urgently required.

The objective of this experimental study was to determine the efficacy of a biodegradable Polymer-Lipid Encapsulation MatriX (PLEX) loaded with the antibiotic doxycycline as a local prophylactic strategy against implant-associated osteomyelitis in a humeral non-fracture rabbit model.

Activity of the PLEX-doxycycline-coating was tested against both a doxycycline susceptible (doxyS) methicillin-susceptible S. aureus (MSSA) as well as a doxycycline-resistant (doxyR) MRSA. In a rabbit intramedullary (IM) nail-related infection model, twelve rabbits received an inoculum of a doxyS MSSA direct into the medullary cavity of the humerus. After inoculation, animals received either a PLEX-doxycycline-coated nail, or an uncoated nail. The animals were observed for four weeks. Upon euthanasia, quantitative bacteriology was performed to determine bacterial load in tissues and biofilm formation on the implant. A second study was performed with sixteen rabbits receiving a DoxyR MRSA inoculum, again in coated and uncoated groups.

In vitro elution studies revealed that 25% of the doxycycline was released from the PLEX-coated implants within the first day, followed by a 3% release per day up to day 28. Quantitative bacteriology revealed the presence of osteomyelitis in all animals receiving an uncoated nail in both the MSSA and the DoxyR MRSA studies (figure). All rabbits receiving a PLEX-doxycycline-coated nail were culture negative in the doxyS MSSA-group and the surrounding bone displayed a normal physiological appearance in both histological sections and radiographs. In the doxyR MRSA inoculated rabbits, a statistically significant reduction in the number of culture-positive samples was observed for the PLEX-doxycycline-coated group when compared to the animals that had received an uncoated nail, although the reduction in bacterial burden did not reach statistical significance.

Improved prophylaxis against infection in trauma and orthopedic implant surgery is clearly required today. In this study, we investigated a PLEX-doxycycline-coated IM nail in a humeral non-fracture rabbit model. The PLEX-doxycycline coating on titanium alloy implants provided complete protection against implant-associated MSSA osteomyelitis, and resulted in a significant reduction in the number of culture positive samples when challenged with a doxycycline-resistant MRSA.

Background:

Little is known about the forces carried by the Taylor Spatial Frame (TSF) hexapod fixator. Our aim was to measure the TSF resultant force and how this changed during the consolidation phase.

Summary

The two-step labeling protocol using Lysostaphin and bio-orthogonal click chemistry for staining bacteria is described. The click protocol is efficient in labeling staphylococci and is non-toxic. This protocol promises the efficient of infections that are difficult to assess by conventional imaging.

Summary Statement

Tibia plateau split fracture fixation with two cancellous screws is particularly suitable for non-osteoporotic bone, whereas four cortical lag screws provide a comparable compression in both non-osteoporotic and osteoporotic bone. Angle-stable locking plates maintain the preliminary compression applied by a reduction clamp.

Summary

Biomechanically, a 2° screw deviation from the nominal axis in the PFLCP leads to significantly earlier implant failure. Screw deviation relies on a technical error on insertion, but in our opinion cannot be controlled intraoperatively with the existing instrumentation devices.

The position of the pelvis has been shown to influence acetabular orientation. However there have been no studies quantifying that effect on the native acetabulum. Our aims were to investigate whether it is possible to quantify the relationship between pelvic tilt and acetabular orientation in native hips, and whether pelvic tilt affects acetabular cover of the femoral head.

Computerized tomography scans of 93 hips (36 normal, 31 dysplastic and 26 with acetabular retroversion) were analyzed. We used a CT technique that allows standardised three-dimensional (3D) analysis of acetabular inclination and anteversion and calculation of femoral head cover in relation to the anterior pelvic plane and at different degrees of forward and backward tilt. Acetabular anteversion, inclination and cover of the femoral head were measured at pelvic tilt angles ranging from −20° to 20° in relation to the anterior pelvic plane using 5° increments.

The effect of pelvic tilt on version was similar in the normal, dysplastic and retroverted groups, with a drop in anteversion ranging from 2.5° to 5° for every 5° of forward tilt. The effect on inclination was less marked and varied among the three groups. Pelvic tilt increased femoral head cover in both normal and dysplastic hips. The effect was less marked, and tended to be negligible at higher positive tilt angles, in the retroverted group.

This study has provided benchmark data on how pelvic tilt affects various acetabular parameters which in turn may be helpful in promoting greater understanding of acetabular abnormalities and how pelvic tilt affects the interpretation of pelvic radiographs.

We have investigated whether a system of four inertial measurement units (IMUs) attached to the segments of the lower limbs could provide useful information about the kinematics of limb segment movement in gait in a healthy population. Four IMUs were attached to participants over their clothes. Participants then walked at their self-selected speed for 10 metres along a corridor and back. IMUs were removed, data downloaded on to a computer and ranges of motion were calculated for thigh, calf and knee, in addition to stride duration. 128 participants were recruited aged 18–97. There was little variation in most angle parameters up to age of 80. The relationships between angle and age are non-linear. There was a slight increase in stride duration with age of about 0.1% per year. The study concentrated on active subjects, with no specific co-morbidities that might affect gait. Results obtained may represent what is achievable for any given age, and approximate to changes that occur due to primary ageing. We propose that, after the age 80, peak muscle power declines below a threshold, such that muscular activity required to move a limb approaches the peak power available, and that it is the decline in peak muscle power that ultimately limits gait in active older people. Walking ability is important in maintaining independence as people age. It would be more effective to encourage exercises to maintain normal gait at a much earlier age. Deviations from the normal range could be identified early, and appropriate intervention given.

Improvements in the surgical technique of total knee replacement (TKR) are continually being sought. There has recently been interest in three-dimensional (3D) pre-operative planning using magnetic resonance imaging (MRI) and CT. The 3D images are increasingly used for the production of patient-specific models, surgical guides and custom-made implants for TKR.

The users of patient-specific instrumentation (PSI) claim that they allow the optimum balance of technology and conventional surgery by reducing the complexity of conventional alignment and sizing tools. In this way the advantages of accuracy and precision claimed by computer navigation techniques are achieved without the disadvantages of additional intra-operative inventory, new skills or surgical time.

This review describes the terminology used in this area and debates the advantages and disadvantages of PSI.

Introduction: The diagnosis of acetabular retroversion has traditionally been established by the presence of a cross-over sign on a plain pelvic radiograph. This however can be greatly influenced by the radiograph’s quality and degree of pelvic tilt. The aim of this study was to look at the relationship between cross-over and true anatomical version as measured in relation to an anatomical reference plane. The secondary aim was to determine whether in true retroversion there was excess coverage of the femoral head anteriorly.

Materials and Methods: Radiographs of 33 patients (64 hips) being investigated for symptoms of femoro-acetabular impingement were analysed. The presence of a cross-over sign was documented and the extent of cross-over was measured by noting the point on the rim where the cross-over occurs. CT scans of the same hips were analysed to determine anatomical version, and to calculate total, anterior and posterior coverage of the femoral head. This was done in relation to the anterior pelvic plane after correcting for pelvic tilt.

Results: The sensitivity, specificity and positive and negative predictive values for the cross-over sign were 92%, 55%, 59% and 91% respectively. The cross-over distance was correlated with 3D version (p=0.01). There was no significant difference in total cover of the femoral head between the anteverted and retroverted subgroups (71% vs. 72% respectively; p=0.55). Anterior cover was higher in the retroverted subgroup (35% vs. 32%; p = 0.0001), and posterior cover was significantly lower in this subgroup (37% vs. 39%; p = 0.002).

Discussion: Although the cross-over sign was sensitive enough to identify 92% of the retroverted cases, its specificity was low with just under half of the anteverted cases being labelled as retroverted. The findings for femoral head cover suggest that retroversion is characterised by posterior deficiency and increased cover anteriorly.

This study examined the relationship between the cross-over sign and the true three-dimensional anatomical version of the acetabulum. We also investigated whether in true retroversion there is excessive femoral head cover anteriorly. Radiographs of 64 hips in patients being investigated for symptoms of femoro-acetabular impingement were analysed and the presence of a cross-over sign was documented. CT scans of the same hips were analysed to determine anatomical version and femoral head cover in relation to the anterior pelvic plane after correcting for pelvic tilt. The sensitivity and specificity of the cross-over sign were 92% and 55%, respectively for identifying true acetabular retroversion. There was no significant difference in total cover between normal and retroverted cases. Anterior and posterior cover were, however, significantly different (p < 0.001 and 0.002). The cross-over sign was found to be sensitive but not specific. The results for femoral head cover suggest that retroversion is characterised by posterior deficiency but increased cover anteriorly.

INTRODUCTION: Periprosthetic bone remodeling after uncemented hip replacement has always been a matter of research and debate. DEXA analysis of BMD was studied by previous groups but not the cross sectional cortical volume. We report a validated CT based algorithm for accurate measurement of cortical volume in these group of patients.

METHODS: Twenty two patients (34 hips) who have undergone Uncemented Furlong total hip replacement agreed to undergo CT scan of their hips for our study. The mean age was 74.6 yrs. The mean follow up was 5.4 yrs. 12 patients had bilateral replacement.

Using software adapted for the specific purpose, femoral cortical volume was measured at three different levels at a fixed distance from the lower border of the lesser trochanter on both sides: 6mm distal to the tip of the prosthesis (z), At the top of the cylindrical portion(x) Midway between x and z (y).

Accuracy and precision of the of the method was also assessed.

RESULTS: The mean cortical volume in the proximal cylindrical portion (x), midpoint(y) and the portion of bone distal to the prosthesis (z) were 458 mm3, 466 mm3, 504 mm3 respectively. The corresponding cortical volumes in the contralateral native femur in unilateral hip replacements were 530 mm3(x), 511 mm3(y), 522 mm3 (z) giving a ratios of 0.86(x), 0.91(y) and 0.97(z). The mean cortical volumes on the left side of bilateral hips were 490 mm3(x), 499 mm3(y) and 528 mm3 (z). The mean cortical volumes on the right side were 456 mm3(x), 463 mm3 (y) and 516 mm3 (z).

No significant trend was noted with change of volume of bone with time.

In the three cases who had cemented hips on their other side, the cemented hips exhibited substantially more stress shielding than their cementless controls (ratios of 0.82, 0.74 and 0.85).

A high correlation between the test and standard measurements was noted. The interobserver agreement between two observers was also good.

DISCUSSION & CONCLUSION: In a fully coated uncemented femoral component, with documented long term results, it is to be expected that load will be shed steadily along the length of the prosthesis. In this study we have confirmed this supposition, with volumetric data, by showing that an almost normal bone just below the tip of the stem (97% volume) reduces to a bone volume of 91% by the middle of the stem and then 86% by the shoulder of the prosthesis. This decrease in the volume of cortical bone effectively normal at the tip of the prosthesis while not optimal appears to stabilize early with no trend of continued reduction over a decade. The effect of cementation on stress shielding was only examined incidentally in this study but appears to contribute to more marked bone loss.

INTRODUCTION Assessing femoral head coverage is a crucial element in acetabular surgery for hip dysplasia. CT has proven to be more accurate, practical and informative than plain radiography at analysing hip geometry. Klaue et al first used a computer-assisted model to indirectly derive representations of femoral head coverage. Jansen et al then described a CT-based method for measuring centre edge angle of Wiberg at 10 rotational increments. Haddad et al used that method to look at dysplastic hips pre- and post-acetabular osteotomy. We present a novel CT-based method that automatically gives an image of the head with the covered area precisely represented. We used this technique to accurately measure femoral head coverage (FHC) in normal hips and in a prospective study of patients with hip dysplasia undergoing peri-acetabular osteotomy. The impact of surgery on acetabular anteversion and inclination was also assessed.

METHODS Using a custom software programme, anatomical landmarks for 25 normal and 26 dysplastic hips were acquired on the 3D reconstructed CT image and used to define the frame of reference. Points were then assigned on the femoral head surface and the superior half of the acetabular rim after aligning the pelvis in the anterior pelvic plane. The programme then automatically produced an image representing the femoral head and its covered part along with the calculated femoral head coverage. To do so, the software represents the femoral head by a best-fit sphere, and the sphere and the acetabular contour are then projected onto a plane in order to calculate the load bearing fraction and area.

RESULTS In the normal hips FHC averaged 73% (SD 4), whereas anteversion and inclination averaged 16° (SD 7°) and 44° (SD 4°) respectively. In the dysplastic group the mean FHC was 50% (SD 6), with a mean anteversion of 19° (SD 10°) and mean inclination of 53° (SD 5°). Peri-acetabular osteotomy has been performed on 16 hips so far, and the FHC for those averaged 66% (SD 5), a mean improvement of 32%. The respective anteversion and inclination post-operatively were 18° (SD 12°) and 40° (SD 8°).

DISCUSSION This is the first study to our knowledge that has used a reliable and practical measurement technique to give an indication of the percent coverage of the femoral head by the acetabulum in normal hips. When this is applied to assessing coverage in surgery to address hip dysplasia it gives a clearer understanding of where the corrected hip stands in relation to a normal hip, and this should allow for better determination of the likely outcome of this type of surgery. The versatility of the method gives it significant attraction for acetabular surgeons and makes it useful not only for studying dysplastic hips but also other hip problems such as acetabular retroversion.

We present a new CT-based method which measures cover of the femoral head in both normal and dysplastic hips and allows assessment of acetabular inclination and anteversion. A clear topographical image of the head with its covered area is generated.

We studied 36 normal and 39 dysplastic hips. In the normal hips the mean cover was 73% (66% to 81%), whereas in the dysplastic group it was 51% (38% to 64%). The significant advantage of this technique is that it allows the measurements to be standardised with reference to a specific anatomical plane. When this is applied to assessing cover in surgery for dysplasia of the hip it gives a clearer understanding of where the corrected hip stands in relation to normal and allows accurate assessment of inclination and anteversion.

Wear and loosening are the major causes for long tem failure in Total Hip Replacement (THR). Accurate three dimensional wear analysis of radiographs has its own limitations. We report the results of our clinical study of three dimensional volumetric wear measurements using our custom low radiation risk CT based algorithm and special software

Twenty four patients (32 hips) agreed to take part in our study. The male: female ratio was 1:4. The mean age was 75 years and the mean follow up was 5.4 years. All patients had 28 mm diameter ceramic heads. Of the 32 hips, 17 hips had polyethylene inserts and 15 hips had ceramic inserts. The maximum follow up for the polyethylene and ceramic groups were 12 years and 5.5 years respectively. All the patients were scanned using Somatom Sensation 4 scanner. Using custom software, 3D reconstruction of the components was done and landmark acquisition done on the femoral head, acetabular metal component and the insert. From these landmarks, a dedicated program was used to calculate the centre of the femoral head in relation to the centre of the acetabular component in all three axes and an indirect measurement of wear obtained. Using the axes measurements graphical 3D models of migration of the femoral head component into the acetabular liner were created and volume of wear measured using special software. Accuracy of the method was assessed by measuring the radius of the femoral head since all patients had 28mm diameter heads implanted in them. Assessment of precision of method was done by calculating the level of agreement between two independent observers.

In the polyethylene group, there was no significant (< 1mm) wear in x and y axis with time. However there was significant evidence of wear in relation to time in the z axis (max wear = −2.5 mm). In the ceramic group with relatively shorter follow up, there was no evidence of significant wear in all three axes. The mean volume measured in the polyethylene group was 685 mm3 (max = 1629 mm3, min = 132mm3 ). The mean volume measured in the ceramic group was 350mm3 (max = 1045 mm3, min = 139mm3 ). The mean radius of the femoral head measured in both groups was 14.02mm (range =13.8 to 14.4 mm). Accuracy was limited by artifacts particularly in bilateral hip arthroplasties and further in the ceramic group because of the restricted access to the ceramic head for placement of markers. Measurements obtained by two independent observers showed a strong correlation (0.99, p value = 0.001) for the polyethylene group. In the ceramic group the correlation (0.69, p value=0.0126) was not as strong as the polyethylene group.

This study has produced a method for three dimensional estimation of wear that can be obtained from low dose CT scans with better accuracy and repeatability (< 0.5 mm) even than to ex vivo studies particularly in polyethylene bearings(wear rate 0.14mm/yr). Noise reduction with appropriate artefact reduction software may further improve the accuracy of this simple and repeatable method.

Various frames of reference are routinely used for hip and knee arthroplasty. We hypothesised that the linea aspera is a constant anatomical feature which can be used as a frame of reference.

Twenty cadaveric femora were CT scanned with high resolution 1mm slices. Robin 3D software was used to manipulate the CT data. Three points were identified on the posterior aspect of the lesser trochanter, medial and lateral femoral condyles to position the femora in similar positions based on the posterior femoral plane (PFP). Centres of the femoral head and neck were derived by surface markers placed on the head and around the neck respectively. Joining the 2 centres gave head neck axis (HNA). The most prominent point on the linea aspera was identified at a level midway along the length of the femur. At that level the centre of the canal was derived by placing surface markers. Joining the most prominent point on the linea aspera to the centre of the canal identified our plane, linea aspera – centre plane (LCP). Angle measurements were made between PFP to HNA, PFP to LCP and LCP to HNA.

PFP to HNA is the traditional method for measuring anteversion angle which in our series had a mean of 13°, SD of 5 (range 5–24). PFP to LCP gave very similar results with mean 101°, SD 6 (range 92–112). However it was noted that there is weak correlation between PFP to HNA angle and PFP to LCP angle for each femur. LCP to HNA measurements were more variable with mean 89°, SD 8 (range 76–108).

From these data we conclude that the proximal half of the femur has more variable torsion compared to the distal half. This study shows that the linea aspera should not be used as a frame of reference for hip nor knee arthroplasties. However, further studies are needed to evaluate the linea aspera in-vivo where it is expected to be more prominent and easier to identify.

Periprosthetic bone remodeling after uncemented hip replacement has always been a matter of research and debate. DEXA analysis of bone density was studied by previous groups but not the cross sectional cortical volume. We report a validated CT based algorithm for accurate measurement of cortical volume in these group of patients.

Twenty two patients who have undergone Uncemented Furlong total hip replacement agreed to undergo CT scan of their hips for our study. The mean age was 74.6 yrs. The mean follow up was 5.4 yrs. Using software adapted for the specific purpose, femoral cortical volume was measured at three different levels at a fixed distance from the lower border of the lesser trochanter on both sides:

6mm distal to the tip of the prosthesis (z),

Accuracy of the method was assessed by measuring the volume of artificial cavities created on a polyurethane pelvis. Assessment of precision of method was done by calculating the level of agreement between two observers.

The mean cortical volume in the proximal cylindrical portion (x), midpoint(y) and the portion of bone distal to the prosthesis (z) were 458 mm3, 466 mm3, 504 mm3 respectively. The corresponding cortical volumes in the contralateral native femur in unilateral hip replacements were 530 mm3(x), 511 mm3(y), 522 mm3 (z) giving a ratios of 0.86(x), 0.91(y) and 0.97(z). The mean cortical volumes on the left side of bilateral hips were 490 mm3(x), 499 mm3(y) and 528 mm3 (z). The mean cortical volumes on the right side were 456 mm3(x), 463 mm3 (y) and 516 mm3 (z). No significant trend was noted with change of volume of bone with time. In the three cases who had cemented hips on their other side, the cemented hips exhibited substantially more stress shielding than their cementless controls (ratios of 0.82, 0.74 and 0.85). A high correlation between the test and standard measurements was noted. The interobserver agreement between two observers was also good.

In a fully coated uncemented femoral component, with documented long term results, it is to be expected that load will be shed steadily along the length of the prosthesis. In this study we have confirmed this supposition, with volumetric data, by showing that an almost normal bone just below the tip of the stem (97% volume) reduces to a bone volume of 91% by the middle of the stem and then 86% by the shoulder of the prosthesis. This decrease in the volume of cortical bone effectively normal at the tip of the prosthesis while not optimal appears to stabilize early with no trend of continued reduction over a decade. The effect of cementation on stress shielding was only examined incidentally in this study but appears to contribute to more marked bone loss.

The use of intramedullary column screws in the treatment of acetabular fractures is becoming more widely utilized. The development of percutaneous methods to insert these screws under image intensifier guidance is one of the main reasons for their increased use. Few groups are navigating insertion of these screws. The available screws are cannulated 6.5–8 mm screws. Most surgeons prefer using 3.2 mm guide wires to reduce deflection. With a shank diameter of 4.5 mm, 3.2 mm cannulation significantly weakens the screws. We postulated that both columns, specially the posterior column can accommodate larger screw diameters which will increase the stability of fixation allowing earlier full weight bearing. The currently used screws were designed for fixation of femoral neck fractures. As percutaneous fixation of acetabular fractures is a growing area of interest, this warrants designing suitable screws with larger diameters.

Eight CT scans of the adult pelvis –performed for non fracture related indications-, were studied (7 females, 1 male). We found that the anatomical cross-section of the columns is irregular but approximately triangular. The method we used to determine the largest diameter of a screw to fit each column was fitting cylinders in the columns. Robin’s 3D software was used to segment acetabula and convert the CT data into polygon mesh (stereolithography STL format) bone surfaces at an appropriate Hounsfield value. The resulting STL files were imported in Robin’s Cloud software, where polygon mesh cylinders of 10 mm diameter were fitted in each column. These cylinders were then manipulated to achieve best fit and their diameters were gradually increased to the biggest diameter which still fitted in the column.

The mean diameters of the fitted cylinders were 10.8 mm (range: 10–13mm) and 15.2 mm (range 14–16.5mm) for the anterior and posterior columns respectively.

To our knowledge, this is the first investigation to study the cross sectional dimensions of the anterior and posterior columns of the acetabulum. Our small sample shows that both columns can safely accommodate larger screws than those currently used. We plan to investigate this further using cadavers.

Periacetabular osteolysis is now considered one of the major long term complications following uncemented total hip replacement. Radiographs are inaccurate and lack sensitivity in detecting lesions even with multiple views. Very few clinical studies have shown the use of CTscan for measuring these lesions. We report our clinical experience with CT based algorithm for measuring it.

Twenty two patients (32 hips) who have undergone Uncemented Furlong total hip replacement agreed to undergo CT scan of their hips for our study. The mean follow up was 5.4 yrs. Of the 34 hips,17 were polyethylene bearings and 15 were ceramic bearings. Nine patients had bilateral replacement in this group. Using custom reconstruction software, 3D models were created and volume measurements made after identifying the lesions in the slices and painting them using appropriate tools available in the software.

Accuracy of the method was assessed by measuring the volume of artificial cavities created on polyurethane pelvis with and without the components. In our control experiments, a high correlation between the test and standard measurements was noted in the cavities above the component, while medial to the acetabular component in bilateral cases it was difficult to be accurate, with cavities less than 10mm in diameter being hard to detect reliably.

In our clinical group of 32 hips, degenerative cysts were noted in 13, secondary rheumatoid cysts in 2 and wear cysts were noted in 2, the largest having a maximum dimension of 10mm. All the degenerative cysts were in the peripheral zone and both the wear cysts were seen in the central zone communicating with the screw holes. These cysts were identified by the characteristic absence of sclerosis surrounding the cyst and obvious communication with screw holes. Both the wear cysts were found with polyethylene bearings at a minimum of 5yrs follow up.

The mean volume of the degenerative cysts was 799 mm3 (71–3500) and the mean volume of the wear cysts was 567 mm3 (550–585)

The low dose CT method we describe and the results we report show that cavities can be measured reliably, above or below the acetabular component. On the medial side, in bilateral cases in particular, although location is possible, volumetric analysis of anything less than 10mm in diameter is not.

Regarding surveillance strategy for wear cysts, we have established that in this series the incidence is 14%, with one at 5 yrs and another noted at 12 yrs, with 10mm in maximum dimension. The absence of any wear cysts at all in the ceramic group, albeit after a shorter follow up of only 5 years is encouraging.

Based on these figures, with these implants, we would recommend that there is no need to undertake surveillance more frequently than every 10 years.

Assessing femoral head coverage is a crucial element in acetabular surgery for hip dysplasia. Plain radiographic indices give rather limited information. We present a novel CT-based method that measures the fraction of the femoral head that is covered by the acetabulum. This method also produces a direct image of the femoral head with the covered part clearly represented, and it also measures acetabular inclination and anteversion. We used this method to determine normal coverage, and applied it to a prospective study of patients with hip dysplasia undergoing periacetabular osteotomy.

Twenty-five normal and 26 dysplastic hips were studied. On each CT scan points were assigned on the femoral head surface and the superior half of the acetabular rim. The anterior pelvic plane was then defined, and the pelvis was aligned in that plane. Using our custom software programme, the fraction of the head that was covered was measured, in addition to acetabular inclination and anteversion.

In the normal hips femoral head coverage averaged 73% (SD 4). In the same group, mean anteversion was 15.7° (SD 7°), whereas mean inclination was 44.4° (SD 4°). In the dysplastic group femoral head coverage averaged 50.3% (SD 6), whereas mean anteversion and inclination were 18.7° (SD 9°) and 53.2° (SD 5°) respectively.

This is the first study to our knowledge that has used a reliable measurement technique of femoral head coverage by the acetabulum in the normal hip. When this is applied to assessing coverage in surgery for hip dysplasia it allows a clearer understanding of where the corrected hip stands in relation to a normal hip. This would then allow for better determination of the likely outcome of this type of surgery. We are presently conducting a prospective study using this technique to study dysplastic hips pre- and post-periacetabular osteotomy.

Whilst computer assistance enables more accurate arthroplasty to be performed, demonstrating this is difficult. The superior results of CAOS systems have not been widely appreciated because accurate determination of the position of the implants is impossible with conventional radiographs for they give very little information outside their plane of view.

We report on the use of low dose (approximately a quarter of a conventional pelvic scan), low cost CT to robustly measure and demonstrate the efficacy of computer assisted hip resurfacing. In this study we demonstrate 3 methods of using 3D CT to measure the difference between the planned and achieved positions in both conventional and navigated hip resurfacing.

The initial part of this study was performed by imaging a standard radiological, tissue equivalent phantom pelvis. The 3D surface models extracted from the CT scan were co-registered with a further scan of the same phantom. Subsequently both the femoral and acetabular components were scanned encased in a large block of ice to simulate the equivalent Hounsfield value of human tissue. The CT images of the metal components were then co-registered with their digital images provided by the implant manufactures. The accuracy of the co-registration algorithm developed here was shown to be within 0.5mm.

This technique was subsequently used to evaluate the accuracy of component placement in our patients who were all pre-operatively CT scanned. Their surgery was digitally planned by first defining the anterior pelvic plane (APP), which is then used as the frame of reference to accurately position and size the wire frame models of the implant. This plan greatly aids the surgeon in both groups and in the computer assisted arm the Acrobot Wayfinder uses this pre-operative plan to guide the surgeon.

Following surgery all patients, in both groups were further CT scanned to evaluate the achieved accuracy. This post-operative CT scan is co-registered to the pre-operative CT based plan. The difference between the planned and achieved implant positions is accurately computed in all three planes, giving 3 angular and 3 translational numerical values for each component.

Further analysis of the CT generated results is used to measure the implant intersection volume between the pre-operatively planned and achieved positions. This gives a single numerical value of placement error for each component. These 3D CT datasets have also been used to quantify the volume of bone resected in both groups of patients comparing the simulated resection of the planned position of the implant to that measured on the post-operative CT.

This study uses 3D CT as a surrogate outcome measure to demonstrate the efficacy of CAOS systems.

Various frames of reference are routinely used for hip and knee arthroplasty. We hypothesised that the linea aspera is a constant anatomical feature which can be used as a frame of reference.

Twenty cadaveric femora were CT scanned with high resolution 1mm slices. Robin 3D software was used to manipulate the CT data. Three points were identified on the posterior aspect of the lesser trochanter, medial and lateral femoral condyles to position the femora in similar positions based on the posterior femoral plane (PFP). Centres of the femoral head and neck were derived by surface markers placed on the head and around the neck respectively. Joining the 2 centres gave head neck axis (HNA). The most prominent point on the linea aspera was identified at a level midway along the length of the femur. At that level the centre of the canal was derived by placing surface markers. Joining the most prominent point on the linea aspera to the centre of the canal identified our plane, linea aspera – centre plane (LCP). Angle measurements were made between PFP to HNA, PFP to LCP and LCP to HNA.

PFP to HNA is the traditional method for measuring anteversion angle which in our series had a mean of 13°, SD of 5 (range 5–24). PFP to LCP gave very similar results with mean 101°, SD 6 (range 92–112). However it was noted that there is weak correlation between PFP to HNA angle and PFP to LCP angle for each femur. LCP to HNA measurements were more variable with mean 89°, SD 8 (range 76–108).

From these data we conclude that the proximal half of the femur has more variable torsion compared to the distal half. This study shows that the linea aspera should not be used as a frame of reference for hip nor knee arthroplasties. However, further studies are needed to evaluate the linea aspera in-vivo where it is expected to be more prominent and easier to identify.

Introduction: Assessing coverage of the femoral head is a crucial element in acetabular surgery for hip dysplasia. Radiographic indices give rather limited information. We present a novel ct-based method that gives an image of the head with the covered area precisely represented. We used this method to measure femoral head coverage in a series of normal hips and in a prospective study of patients with hip dysplasia undergoing peri-acetabular osteotomy.

Methods: Thirteen normal and ten dysplastic hips were studied. On each CT scan anatomical landmarks were assigned on the 3d reconstructed image and used to define the frame of reference. Points were assigned on the femoral head surface and the superior half of the acetabular rim after aligning the pelvis in the anterior pelvic plane. An image was produced representing the femoral head and its covered part. The fraction of the head that was covered was calculated.

Results: The average femoral head coverage in the normal hips was 73.9% (sd 3.2). The average coverage in the dysplastic group was 50.7% (sd 7.9) and after undergoing peri-acetabular osteotomy the average was 67% (sd 6.2).

Conclusion: This is the first study to our knowledge that has used a reliable measurement technique to give an indication of the percent coverage of the femoral head by the acetabulum in the “normal hip”. When this is applied to assessing coverage in surgery to address hip dysplasia it gives a clearer understanding of where the corrected hip stands in relation to a normal hip, and this should allow for better determination of the likely outcome of this type of surgery.

This study was undertaken to assess the contribution of pulmonary fat embolism to systemic platelet activation in a rabbit model of fat embolism. Fifteen NZW rabbits were randomly assigned into one of two groups: fat embolism and control. Fat embolism was induced via intramedullary canal pressurization with a 1–1.5 ml bone cement injection. Only the animals that underwent fat embolism displayed consistent platelet activation, as demonstrated by platelet degranulation and procoagulatory surface expression. These findings suggest that fat embolism plays a role in platelet activation and in the overall activation of hemostasis following trauma.

The objective of this study was to use a recently developed rabbit model of fat embolism to assess the systemic hemostatic response to pulmonary fat embolism.

Our findings demonstrate platelet activation following forced liberation of bone marrow contents into the circulation only in the FE group, as demonstrated by CD62P elevation (a marker of platelet degranulation) and annexin V elevation (a marker of procoagulatory surface expression). Platelet activation also coincided with significantly lower platelet counts in the FE group at two and four hours post embolism, suggesting platelet aggregation.

These findings suggest that fat embolism plays a role in platelet activation and in the overall activation of hemostasis following trauma.

Platelet count decreased significantly at two and four hours post knee manipulation only in the FE group. Annexin V expression increased significantly in the FE group at two and four hours post knee manipulation. Lastly, CD62P expression only increased significantly in the FE group at two hours post knee manipulation

Fifteen New Zealand White male rabbits were randomly assigned into one of two groups: control and fat embolism (FE). In FE group (n=8), the intramedullary cavity was drilled, reamed and pressurized with a 1–1.5 ml bone cement injection. In the control group (n=7), a sham knee incision was made, exposing both femoral condyles, but was immediately closed without further manipulations. All animals were mechanically ventilated for an additional monitoring period of four hours post-surgical closure. For flow cytometric evaluation of platelet activation, blood samples were stained with fluorescence-conjugated antibodies against CD41 (FITC), CD62P (P-selectin) and annexin V (FITC). Platelet events were identified by their characteristic CD41 staining and size and were analyzed using a flow cytometer. All animals were mechanically ventilated for four hours post surgical closure.

The implications of platelet activation following fat embolism are numerous, ranging from adherence and aggregation, to secretion of key components of both the coagulation and inflammatory cascades.

The purpose of this study was to determine the effect of positioning (lateral vs. supine) on pulmonary patho-physiology following pulmonary contusion and fat embolism in a canine model of polytrauma. Platelet and neutrophil activation were assessed using flow-cytometry. There were no significant differences between groups in CD62P and CD11/18 MCF (markers of platelet and neutrophil activation, respectively) following fat embolism. However, only animals in the lateral position displayed significant increases in both measures as compared to baseline values. Lateral positioning may exert an early effect on proinflammatory and coagulation activation, and may play a role in the development of acute lung injury.

It has previously been suggested that acute lung injury can be influenced by patient positioning, be it lateral or supine. The purpose of this study was to determine the effect of positioning on pulmonary pathophysiology associated with concomitant pulmonary contusion and fat embolism in a canine model of polytrauma.

Twelve dogs were randomly assigned to one of two surgical positioning groups, lateral and supine. The dogs were subjected to pulmonary contusion by application of force between 200–250 N/m² for thirty seconds in three areas of one lung. Two hours later, fat embolism was induced via reaming of the ipsilateral femur and tibia and cemented nailing. Two hours later, the dogs were sacrificed. For flow-cytometric evaluation of platelet and neutrophil activation, venous blood samples were stained with fluorescence-conjugated antibodies against CD62P and CD11/18, respectively. There were no significant differences between the groups in CD62P and CD11/18 mean channel fluorescence (MCF) following pulmonary contusion and fat embolism. However, only animals in the lateral positioning group displayed significant increases in CD62P and CD11/18 MCF at two hours following fat embolism as compared to baseline values.

Our findings suggest that lateral positioning, autoregulation and preferential blood flow to the contused non-dependent lung may render lung tissue more susceptible to congestion and lead to activation of both platelets and neutrophils. Lateral positioning may have an early effect on activation of the inflammatory and coagulation cascades and may be significant in the development of posttraumatic acute lung injury.

This study was undertaken to assess the contribution of fat embolism (FE) to the development of acute lung injury in the presence of resuscitated hemorrhagic shock. Twenty-seven NZW rabbits were randomly assigned into four groups: resuscitated hemorrhagic shock and FE (HR/FE), resuscitated hemorrhagic shock, FE, and control. FE was induced via intramedullary femoral canal pressurization using a 1–1.5 ml bone cement injection. Only HR/FE animals displayed significant proinflammatory cytokine release as compared to controls. These findings suggest that the combination of resuscitated shock with FE initiates an inflammatory response, which may lead to the development of fat embolism syndrome.

The objective of this study was to assess the contribution of fat embolism caused by intramedullary femoral canal pressurization to the development of acute lung injury in the presence of resuscitated hemorrhagic shock.

Only the animals that underwent resuscitated shock and fat embolism displayed amplified BALF proinflammatory cytokine expression.

These findings suggest that the combination of resuscitated shock with fat embolism initiates an inflammatory response, which may play a role in the development of fat embolism syndrome.

Only HR/FE BALF IL-8 and MCP-1 levels were significantly higher than controls (0.72 ng/ml vs. 0.26ng/ ml, p=0.03; 18.3 ng/ml vs. 2.0 ng/ml, p=0.01, respectively).

Twenty-seven NZW rabbits were randomly assigned into four groups: resuscitated hemorrhagic shock + fat embolism (HR/FE), resuscitated hemorrhagic shock (HR), fat embolism (FE), and control. Shock was induced via carotid bleeding for one-hour prior to resuscitation. For FE induction, the intramedullary cavity was drilled, reamed and pressurized with a 1–1.5 ml bone cement injection. Four hours later, postmortem bronchoalveolar lavage was performed through the right mainstem bronchus. Analyses of bronchoalveolar lavage fluid (BALF) of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) were carried out in triplicate and blinded fashion using the ELISA technique.

Our findings suggest that FE by itself does not initiate inflammatory lung injury, as there were no apparent differences between the control and FE cytokine levels. Only the HR/FE animals revealed elevated levels of pro-inflammatory cytokines in BALF. These findings are in agreement with our previous results, which displayed neutrophil activation only in the HR/FE group.

This study investigated the time lost from work following a distal radius fracture and its predictors. A cohort of one hundred and sixty-eight workers who experienced a distal radius fracture were followed at two, three, six, and twelve months to determine their work status. The average number of weeks lost from work was 9.5 weeks. Significant correlates with lost-time from work were: energy of injury, occupational demand, workers compensation, initial radial inclination on x-ray, baseline PRWE and DASH scores and Mental Component-SF-36). Without self-report, 45% of the variation in lost-time was explained by workers compensation status, radial inclination, occupational demand, energy of injury, sex and age.

This study investigated the time lost from work following a distal radius fracture and its predictors.

Time lost from work after a distal radius fracture is highly variable. Patients who have higher job demands (hand use), are on workers compensation, report higher initial pain/disability and who present with more severe displacement have the highest lost-time.

This data defines average expectations of return to work and the extent to which injury, job and personal characteristics influence it.

The average number of weeks lost from work was 9.5 weeks ( median= 6; 75th percentile=12 SD=9.6; range = 0–44). Significant correlates with lost-time from work were: energy of injury, occupational demand, workers compensation, initial radial inclination on x-ray, baseline PRWE and DASH scores and Mental Component-SF-36). A stepwise multiple linear regression found that 50% of the variation in lost-time could be explained on the basis of the initial PRWE, occupational demand and radial inclination. Without self-report, 45% of the variation in lost-time was explained by workers compensation status, radial inclination, occupational demand, energy of injury, sex and age.

A cohort of one hundred and sixty-eight workers who experienced a distal radius fracture were enrolled. Age, sex, education level, smoking status, alcohol consumption, injury compensation status, occupational use of hand, energy of injury and radiographic injury severity (pre-reduction radial shortening, radial inclination, dorsal angulation) were recorded. Patients were followed at two, three, six, and twelve months to determine their work status. Multiple linear regression identified predictors of time lost from work.

The purpose of this study was to determine the effect of positioning (lateral vs. supine) on pulmonary pathophysiology following pulmonary contusion and fat embolism in a canine model of polytrauma. Platelet and neutrophil activation were assessed using flow-cytometry. There were no significant differences between groups in CD62P and CD11/18 MCF (markers of platelet and neutrophil activation, respectively) following fat embolism. However, only animals in the lateral position displayed significant increases in both measures as compared to baseline values. Lateral positioning may exert an early effect on proinflammatory and coagulation activation, and may play a role in the development of acute lung injury.

It has previously been suggested that acute lung injury can be influenced by patient positioning, be it lateral or supine. The purpose of this study was to determine the effect of positioning on pulmonary pathophysiology associated with concomitant pulmonary contusion and fat embolism in a canine model of polytrauma.

Twelve dogs were randomly assigned to one of two surgical positioning groups, lateral and supine. The dogs were subjected to pulmonary contusion by application of force between 200–250 N/m² for thirty seconds in three areas of one lung. Two hours later, fat embolism was induced via reaming of the ipsilateral femur and tibia and cemented nailing. Two hours later, the dogs were sacrificed. For flow-cytometric evaluation of platelet and neutrophil activation, venous blood samples were stained with fluorescence-conjugated antibodies against CD62P and CD11/18, respectively.

There were no significant differences between the groups in CD62P and CD11/18 mean channel fluorescence (MCF) following pulmonary contusion and fat embolism. However, only animals in the lateral positioning group displayed significant increases in CD62P and CD11/18 MCF at two hours following fat embolism as compared to baseline values.

Our findings suggest that lateral positioning, autoregulation and preferential blood flow to the contused non-dependent lung may render lung tissue more susceptible to congestion and lead to activation of both platelets and neutrophils. Lateral positioning may have an early effect on activation of the inflammatory and coagulation cascades and may be significant in the development of posttraumatic acute lung injury.

This study was undertaken to assess the contribution of pulmonary fat embolism caused by intramedullary femoral canal pressurization to the development of acute lung injury in the presence of resuscitated hemorrhagic shock. Twenty-seven NZW rabbits were randomly assigned into one of four groups: resuscitated hemorrhagic shock and fat embolism, resuscitated hemorrhagic shock, fat embolism, and control. Fat embolism was induced via intramedullary cavity with a 1–1.5 ml bone cement injection. Only the animals that underwent resuscitated shock and fat embolism displayed amplified neutrophil activation and alveolar infiltration. These findings suggest that the combination of resuscitated shock with fat embolism initiates an inflammatory response, which may play a role in the development of fat embolism syndrome.

The objective of this study was to assess the contribution of pulmonary fat embolism caused by intramedullary femoral canal pressurization to the development of acute lung injury in the presence of resuscitated hemorrhagic shock.

Only the animals that underwent resuscitated shock and fat embolism displayed amplified neutrophil activation and alveolar infiltration.

These findings suggest that the combination of resuscitated shock with fat embolism initiates an inflammatory response, which may play a role in the development of fat embolism syndrome.

CD11b mean channel florescence was only significantly elevated in the HR/FE group at two and four hours post knee manipulation. Moreover, greater infiltration of alveoli by leukocytes was only significantly higher in the HR/FE group as compared to controls.

Twenty-seven NZW rabbits were randomly assigned into one of four groups: resuscitated hemorrhagic shock + fat embolism (HR/FE), resuscitated hemorrhagic shock (HR), fat embolism (FE), and control. Hypovolemic shock was induced via carotid bleeding for one-hour prior to resuscitation. For fat embolism induction, the intramedullary cavity was drilled, reamed and pressurized with a 1–1.5 ml bone cement injection. For evaluation of neutrophil activation, blood was stained with antibodies against CD45 and CD11b and analyzed with a flow cytometer. Animals were mechanically ventilated for four hours post surgical closure. Postmortem thoracotomy was performed, and three stratified random blocks of each lung were processed for histological examination.

Our findings suggest that FE by itself does not cause lung injury, as there were no apparent differences between the control and FE animals. Only the HR/FE animals revealed a higher number of infiltrating neutrophils into alveolar spaces and greater neutrophil activation.

This study determined the validity of three patient self-report scales (PRWE, DASH and AUSCAN) to assess outcomes of CMC arthroplasty. Factor analyses did not support the described structure of the three scales. There was a strong relationship between pain or function subscales across different instruments (r> 0.80). Known construct testing regarding WSIB status and arthritis severity supported the discriminative validity of all scales (p< 0.05) except for the function (PRWE) and stiffness (AUSCAN) subscales (p=0.08). Separation of pain/function concepts may be difficult when evaluating outcomes in hand arthritis. The DASH is not unidimensional in this population

This study determined the concurrent validity of patient self-report scales to assess outcomes of CMC (carpometacarpal) arthroplasty.

The subscale structure of the PRWE, DASH and AUSCAN is not valid for a patient population with hand arthritis – Pain, function and stiffness do not differentiate as separate concepts. It appears as though function can be separated into separate components addressing strength and fine motor hand function on all three scales. The DASH was not unidimensional.

Reporting of outcomes following CMC arthroplasty should utilize either the questionnaires total scores or validated factors. Use of unvalidated subscales should be avoided.

Factor analyses did not support the described structure of any of the three scales. PRWE three subscales- two factors; AUSCAN – pain and stiffness items loaded on one factor, function items separated into two factors; DASH – four factors. The largest factor on the DASH contained items relating to symptoms and participation restrictions. Items relating to hand function also separated into a separate factor. Correlational analyses indicated a strong relationship between pain or function subscales across instruments ( r> 0.80) and low correlation with hand appearance (r< 0.20). Tests of known constructs on WSIB status or arthritis severity supported the discriminative validity of all scales (p< 0.05), except for the function subscale off the PRWE or the stiffness subscale of the AUSCAN (p=0.08).

Factor analyses, inter-scale correlations and tests of known constructs were conducted on the Patient Rated Wrist Evaluation (PRWE), Disability of the Arm, Shoulder, Hand (DASH) and the AUSCAN (osteoarthritis of the hand).

Thirty-eight patients with nonunion of the humeral shaft underwent a comprehensive assessment including completion of three patient-based functional outcome surveys as well as the determination of the Constant shoulder and Mayo elbow scores. Treatment consisted of compression plating with or without bone grafting. Smokers were found to have significantly longer time to union as compared to nonsmokers (25.1 weeks vs. 16.2 weeks, p< 0.001). Our results also demonstrated that increased time to union had a significant negative effect on the patient-reported functional outcome scores.

To evaluate the functional outcome and identify prognostic factors that influence the healing time of surgically treated humeral shaft nonunions.

Time to consolidation of operatively treated humeral shaft nonunions was significantly longer in smokers versus non-smokers. Time to union was negatively associated with the patient-reported functional outcome scores.

The long-term functional outcome following surgical treatment of humeral shaft nonunions is dependent upon the time to consolidation. Smoking is a significant remediable risk factor for delayed union following surgical repair of humeral shaft nonunion.

We identified thirty-eight patients (mean age fifty-five years) treated surgically for nonunion of the humeral shaft at a mean follow-up of sixty months. All patients underwent a comprehensive assessment including the completion of the SF-36, the DASH, the SMFA and the determination of the Constant shoulder and Mayo elbow scores. Seventeen (44.7%) patients were classified as ‘smokers’ and twenty-one (55.3%) were ‘non-smokers’. All nonunions united with a mean time of 16.2 weeks for non-smokers and 25.1 weeks for smokers (p< 0.001). Time to union was negatively associated with the Physical Function portion of the SF-36 (p=0.01), the DASH (p=0.01), and the Arm and Hand Function part of the SMFA (p=0.005). The only other factor that had a significant negative effect on the functional outcome scores was the presence of one or more comorbid factors (SF-36, p< 0.001; DASH, p< 0.001; SMFA, p< 0.001). Patient-oriented and surgeon based scores were found to correlate well (range r=0.545 to r=0.916, p< 0.001 for all combinations).

The purpose of this study was to determine the effect of positioning (lateral vs. supine) on pulmonary pathophysiology following pulmonary contusion and fat embolism in a canine model of polytrauma. Platelet and neutrophil activation were assessed using flow-cytometry. There were no significant differences between groups in CD62P and CD11/18 MCF (markers of platelet and neutrophil activation, respectively) following fat embolism. However, only animals in the lateral position displayed significant increases in both measures as compared to baseline values. Lateral positioning may exert an early effect on proinflammatory and coagulation activation, and may play a role in the development of acute lung injury.

It has previously been suggested that acute lung injury can be influenced by patient positioning, be it lateral or supine. The purpose of this study was to determine the effect of positioning on pulmonary pathophysiology associated with concomitant pulmonary contusion and fat embolism in a canine model of polytrauma.

Twelve dogs were randomly assigned to one of two surgical positioning groups, lateral and supine. The dogs were subjected to pulmonary contusion by application of force between 200–250 N/m² for thirty seconds in three areas of one lung. Two hours later, fat embolism was induced via reaming of the ipsilateral femur and tibia and cemented nailing. Two hours later, the dogs were sacrificed. For flow-cytometric evaluation of platelet and neutrophil activation, venous blood samples were stained with fluorescence-conjugated antibodies against CD62P and CD11/18, respectively.

There were no significant differences between the groups in CD62P and CD11/18 mean channel fluorescence (MCF) following pulmonary contusion and fat embolism. However, only animals in the lateral positioning group displayed significant increases in CD62P and CD11/18 MCF at two hours following fat embolism as compared to baseline values.

Our findings suggest that lateral positioning, autoregulation and preferential blood flow to the contused non-dependent lung may render lung tissue more susceptible to congestion and lead to activation of both platelets and neutrophils. Lateral positioning may have an early effect on activation of the inflammatory and coagulation cascades and may be significant in the development of posttraumatic acute lung injury.

Surgeons need to be able to measure angles and distances in three dimensions in the planning and assessment of knee replacement. Computed tomography (CT) offers the accuracy needed but involves greater radiation exposure to patients than traditional long-leg standing radiographs, which give very little information outside the plane of the image.

There is considerable variation in CT radiation doses between research centres, scanning protocols and individual scanners, and ethics committees are rightly demanding more consistency in this area.

By refining the CT scanning protocol we have reduced the effective radiation dose received by the patient down to the equivalent of one long-leg standing radiograph. Because of this, it will be more acceptable to obtain the three-dimensional data set produced by CT scanning. Surgeons will be able to document the impact of implant position on outcome with greater precision.

We used computer tomography (CT) to measure the outcome of knee-arthroplasty in our prospective double-blind randomised controlled study of our active constraint robotic system ACROBOT.

All patients in our trial had pre-operative CT scan and proprietary software used to plan the size, position and orientation of the implants. Post operatively a further CT scan was performed and measurement studies performed using 3 different methods of manipulating the CT dicom data.

Method 1, a quick and simple method of implant assessment that measures the varus-valgus orientation of the implants relative to the axes of the long bones

Two landmarks each are used to define the individual mechanical axis for both the femur and tibia, for consistency these landmarks are the very ones used in the planning stage on the pre-operative CT.

Landmarks are then placed on the implants in order to measure their tilt relative to the mechanical axes. An appropriate Hounsfield threshold (2800) was used to image the metal components. The angle between the individual mechanical axis and the prosthetic component was calculated.

Method 2, detailed and accurate comparisons between the planned and achieved component positions in 3D are made. Co-registration of the precisely planned CT based models with surface models from the post-op scan gives real measurements of implant position enabling the measurement of the accuracy of component in an all six degrees of freedom giving both translation and rotation errors in all three planes.

The process of alignment was achieved by surface-to-surface registration. An implementation of the iterative closest point algorithm was used to register matching surfaces on the objects to be registered. A polygon mesh of the implant, provided by the manufacturer, defined the surface shape of each size of implant. This was used both to define the planned position and to register to the post-operative scan. Method 3, in this study we quantified post-operative error in knee arthroplasty using one value for each component whilst retaining 3D perspective.

The position of the prosthetic components in the post-op scan is calculated and individual transformation matrix computed which is matched to the transformation matrices for the planned components.

The pre-operative CT based component positions were co-registered to the post-operative CT scan and values for the intersection (volumetric) between the digitised images (both planned and achieved) were calculated. Both the co-registered femoral and tibial component’s intersection was quantified with software packages supporting Boolean volume analysis

Method 1, the sum of the two, independently measured, angles allows an estimate of the post-operative alignment of the load bearing axes in the two bones.

Method 2, 3D CT allows precise measurements of the achieved position for each component in all three planes. Six values, three angular and three translational, define the achieved component position relative to the planned position.

Method 3, the greater the percentage intersection between the planned and achieved images, the greater the accuracy of the surgery. Owing to the shape of the components (large articular surface) large intersections demonstrate more accurate reconstruction of the joint line.

In the recent past the lack of a sufficiently accurate tool to plan and measure the accuracy of component placement has resulted in an inability to detect and study radiological and functional outliers and hence the hypnotised relationship between prosthetic joint placement and outcome has been difficult to prove.

CT offers us the ability to accurately describe the actual position and deviation from plan of component placement in knee arthroplasty. Whilst X-ray has the intrinsic problems of perspective distortion magnification errors and orientation uncertainties CT can be used to define ‘true’ planes for two dimensional (2D) measurements and permits the comparison in three dimensions (3D) between the planned and achieved component positions.

Accurately planning the intervention and precisely measuring outcome in computer assisted orthopaedic surgery (CAOS) is essential for it permits robust analysis of the efficacy of these systems.

We demonstrate the use of low dose computer tomography (CT) radiation for both the planning and outcome measurement of robotic and conventionally performed knee arthroplasty.

Studies were initially performed on a human phantom pelvis and lower limb. The mAs (milliampere seconds) were varied from 120 to 75 at the pelvis and from 100 to 45 for both the knee and ankle whilst keeping the kV (kilovolt) between 120 and 140. Image quality was evaluated at the different doses.

The volumes scanned were defined on the scout film; they included the whole femoral head (0.5cm above and below the head), 20cm at the knee (10cm on either side of the joint line) and 5cm at the ankle (the distal tibia and the talus). Effective dose (mSv) was calculated using two commercially available software packages. This protocol was subsequently used to image patients in our prospective double-blind randomised controlled study of our active constraint robotic system ACRO-BOT.

With the reduction in the mA and scanned volume the effective dose was reduced to 0.761 mSv in females and 0.497 mSv in males whilst maintaining a sufficient image resolution for our purposes. We found that a mAs of 80 for the hip joint, 100 for the knee and 45 for the ankle was sufficient for imaging in both pre-op planning and pos-operative assessment in knee arthroplasty. This contributed on an average effective dose to the hip of 0.61 mSv, the knee 0.120 mSv and to the ankle 0.0046 mSv.

The results of our study show that we have considerably reduced the effective dose (0.8 mSv) to one third of the Perth Protocol (2.5mSv) by reducing the areas of the body scanned and adjusting the mA for the various parts of the body whist maintaining the x, y and z axis throughout the scan. The areas between the knee, hip and ankle that were not exposed to radiation are not strictly necessary for the planning of knee arthroplasty, but it is essential that the leg does not move during the scanning process. In order to prevent this leg was placed in a radiolucent splint. For post op three dimensional (3D) assessments only the knee component of the protocol is necessary.

We report the use of CT with 3D reconstruction to determine the accuracy of knee arthroplasty.

Method Pre- and post-operative CT scans have been performed in a cohort of 20 total and unicompartmental knee replacements in fine detail of hips, knees and ankles but with minimal dosage elsewhere.

Three different methods have been used to measure the position of the implant.

‘True’ anterior posterior views are reconstructed from the post-operative CT data and tibiofemoral angles computed.

Results Alignment can be determined within 0.5° using method 1. With the addition of method, 2 rotational malalignment can be computed. With method 3 a transformation matrix is provided, showing the position in space of the prosthesis relative to the pre-op plan, with accuracy of under 0.5 mm. Poor function is explained.

Conclusion We have used 3-D reconstructions from CT scans and digital measurements to compute the precise position of the implant in the bone. Showing where the implant lies in 3D space explains accurately why poor results have occurred. CT based planning has been used to ensure that the bone cuts are planned correctly. Postoperative CT scans confirm that if the plan is achieved, function will be good.

The accuracy of prosthesis implantation is closely related to their function and longevity; we report the development of an active constraint robot for minimally invasive unicompartmental knee arthroplasty (UKA) using CT and knee scoring.

Method: Pre and postoperative CT scans are performed. Pre-op scan CT scans were used to plan the precise position of implants on the bones. The femoral and tibial bone cuts were then generated, together with the software boundaries that constrain the surgeon. This plan was then used to define the cutting planes of the ‘Acrobot’ active constraint device that we have developed.

The Postoperative CT scan was compared with the preoperative plan. The distance of the joint line from the hip and ankle joint, and its angulation and rotation were compared to the preoperative plan. In addition, the position of the implants relative to their planned position has been computed.

Results: No significant complications have been encountered. Using the postoperative CT scans, in no case is the implant more than 2mm or 2 degrees from the planned position.

Conclusions: The Acrobot system for UKA has completed its preliminary trial satisfactorily. It provides a hands-on operation but with robotic levels of accuracy, through a minimally invasive approach. By abolishing outliers, it improves outcomes in UKA replacement.

Background: The necessity for radiographic follow up of infants with hip clicks and normal ultrasound is not clear.

Materials and methods: Infants referred to a paediatric hip clinic whose sole risk factor for DDH was a soft tissue hip click who had a normal ultrasound scan on initial assessment were identified. A follow up six month AP pelvis radiograph was assessed and acetabular index(A.I), position of femoral ossific nucleus and Shen-ton’s line measured. Infants with rotated pelvis Xrays were excluded. Inter-observer variability for acetabular index was measured and dysplasia defined according to Tonnis.

Results: 171 infants (193 clicking hips) met the criteria for inclusion. 48 male and 109 female with unilateral clicks (57 right, 64 left) and 36 bilateral clicks. 10 were excluded due to rotation of the AP pelvis Xray. Inter-observer error for A.I. was 4°. All A.I. were within normal ranges. Shenton’s line was unbroken and all hips were located.

Conclusion: In this study infants with soft tissue hip clicks and a normal ultrasound scan on initial assessment had a normal Xray at six months.

A non-invasive technique for labelling S phase osteoblasts in vitro following immunolabelling of their focal adhesions is proposed. Quantification of cell adhesion area in the S phase (where the cells are most spread) of the cell cycle is then possible with a scanning electron microscope (SEM).

Primary calvarial osteoblasts (isolated by migration) were cultured on plastic and implant quality metal discs. S-phase cells were labelled by a pulse of 3H thymidine in the culture medium for 30 min. Cells were cultured for a further 2h in normal media before being processed for immunogold labelling of vinculin. Briefly, cells were permeabilised and fixed in 4% paraformaldehyde. Non specific binding sites were blocked for 30 min. Cells were incubated with mouse anti vinculin for 1h before rinsing and blocking with 5% goat serum for 30 min. Secondary incubation was with goat anti mouse 5nm gold conjugate for 2h. After rinsing, cells were permanently fixed with 2.5% glutaraldehyde. For SEM visualisation, the gold label was enhanced with gold enhance solutions. Postfixation and staining was performed with osmium tetroxide. Samples were dehydrated and critically point dried. The discs were carbon coated and covered with a thin layer of photographic emulsion in a dark room and left in a light tight box at 4°C for 7 days before developing the emulsion.

Backscattered electron imaging with the SEM revealed silver grains on the nuclei of S-phase cells, produced by the interaction of radioactive emissions, from the labelled DNA, and the photographic emulsion. Immunolabelled focal adhesions were also observed at higher magnifications on the same cells.

This combination of autoradiography and high resolution SEM removes cell cycle variability, which has been a problem with previous in vitro adhesion studies. This method will be applied to quantify osteoblast cell adhesion to various implant materials to evaluate cell/implant interactions.

Movement between an implant surface and overlying soft tissue gives rise to fibrous capsule formation with a liquid filled void. Clinically, this situation is more prevalent with electropolished stainless steel (EPSS) implants compared to commercially pure titanium (CpTi) implants. We hypothesise this is mainly due to lack of microtopography on the EPSS.

Four experimental EPSS surfaces with varying microtopographies were selected by a combination of morphological analysis using the scanning electron microscope and quantitative roughness analysis using laser profilometry. Standard treated EPSS (ISO 5832/1) and CpTi (ISO 5832/2) surfaces were also used. The plates had only one screw hole at either end so that the interaction of the tissue with an intact surface could be evaluated. Six plates of each type were implanted on both the left and right tibia, randomly, of 18 white New Zealand rabbits under the muscle for 12 weeks.

After sacrifice samples underwent standard histological processing. Briefly, fixation, dehydration, embedding in methyl methacrylate, sectioning at 250μm slices (with implant), grinding to 50μm and staining with Giemsa. Digital images were taken with a light microscope and the size of thickening of connective tissue on the implant surface and the presence or absence of a liquid filled void was observed.

Results showed no voids present on the CpTi samples. The standard EPSS had 3/6 plates with a void. The experimental EPSS surfaces were in-between these results. There was no relationship between quantitative measurements of average roughness (Ra) and the presence or absence of a void. There was a relationship between lack of fine microroughness of a surface (as seen with the SEM) and the presence of a void. The size of capsular thickening was not related to the Ra of the surface. These results support that void formation is mainly due to lack of microtopography on the plates.

We compared, under laboratory conditions, the resistance to cutting out of the AO dynamic hip screw and the Pugh sliding nail. The mean load at cut out, adjusted for bone strength, was 70% greater for the Pugh sliding nail. The reasons for this difference are discussed.