There is a consensus that impingement, subluxation, and dislocation are major risks that can lead to failure in total hip arthroplasty (1). As well as producing edge-wear, such clinical events also may create additional loads of particulate debris (2). It has been suggested that the release of metal debris with collateral damage on metal-on-metal (MOM) bearings creates a particularly severe abrasive wear, hitherto not understood, and recently termed ‘micro-grooving’ (3,4). Perhaps related to this micro-grooving, large surface depressions have also been observed. These we labeled ‘Dongas’, from the South African term for a steep-sided gully created by erosion. The goal of this study was to examine Dongas found on retrieved MOM bearings and to correlate factors such as cause of revision, MOM diameter and Donga locations with respect to regions of normal and stripe wear. Our hypotheses were: (1) Dongas will be most visible in non-wear zones (NWZ) adjacent to the main-wear zone boundary (MWZ), (2) the 28 mm MOM, being inherently less stable compared to large-diameter MOM, will show a higher Donga frequency and (3) patients with subluxation or dislocation complaints will reveal a higher Donga frequency.

Five cases with 28 mm MOM, five of 34–38 mm, and five of 50–56 mm diameter were studied (N = 15). The MWZ was measured in each MOM head and the number of NWZ and MWZ Dongas recorded. Bearing damage was examined using a white-light interferometer (Zygo; 5x lens).

Dongas were mainly elliptical in shape, but sometimes highly irregular. They were commonly circumscribed by raised lips (Fig. 1). Donga “trails” were also found, appearing as a linear series of similar-sized Dongas (Fig. 2). Donga trails exhibited some variability with raised lips either lining only the opposite sides or circumscribing most of the perimeter. The Dongas were commonly found in NWZ, with less than 20% found in MWZ. For this set of 15 MOM bearings, large-diameter bearings showed the largest number of Dongas and the greatest frequency of Dongas resulted from either loose or migrating cups.

The high occurrence of dongas in the non-wear zone (supporting hypothesis-1) may be a result of particles swept into the bearing interface (2,5). The size of the Dongas and their frequent association to local micro-grooves indicated that these were the impact sites of circulating particles. Such large surface depressions (40–200 μm) have not been described previously and may be unique to MOM bearings (3,4). The observation that Dongas were most prevalent in cases with loose or migrating cups left hypothesis-2 unsatisfied. The much higher incidence of Dongas in the large-diameter MOM was surprising and negated hypothesis-3. Overall these new data relating Dongas and micro-grooves gives new credence to a hitherto unsuspected 3^rd-body abrasive wear mechanism due to repetitive subluxation or impingement.

The MOM controversy continues with many prevailing opinions as to the causes of failure in contemporary designs. There has been a great deal of focus on breakdown in fluid-film lubrication with respect to cup positioning and edge wear at its rim. However there has been very little discussion on the problems of 3^rd body abrasion. In only one study was there a description of unusually large abrasive marks on retrieved femoral heads (McKee Farrar MOM), revealing 100 μm wide scratches, attributed to circulating particles fractured during impingement episodes. With contemporary MOM devices, there is the potential for abrasion by particulates of CoCr, PMMA and Ti6Al4V. However it has been difficult to formulate a coherent simulator model for 3^rd-body abrasive wear, given the unpredictable nature of impingement damage releasing abrasive particles into the patient's hip joint. Thus this study sought to identify if metal or cement particulates were capable of creating 100 μm wide scratches as seen on retrieved MOM and develop a simulator model for 3^rd body abrasive testing on MOM bearings.

Six 38 mm CoCrMo bearings (DJO Inc., Texas) were run in a12-station hip simulator (SWM, Monrovia, CA) with cups mounted both anatomically and inverted (3 MOM each). The tests were run in standard simulator mode (Paul gait load cycle: 0.2–2 kN, frequency 1 Hz) with the addition of 5 mg of debris particles. Commercially available CoCr (ASTM F75) and titanium alloy (ASTM F136) particles and broken polymerized bone cement particles were used in the size range 50–200 μm. The simulator was run for only 10 cycles and the MOM parts removed for study. All bearings were ultrasonically cleaned and heads were examined using white light interferometry (WLI, Zygo Corp). Grooves were characterized using surface profiles to measure width, depth, and rim height. SEM imaging (EVO MA15, Zeiss) and EDS imaging (X flash detector 4010, Bruker AXS) was performed in areas of grooving and suspected transfer layers.

CoCr debris produced broad, curvilinear grooves with widths ranging from 20–170 μm, depths from 0.3–1.5 μm, raised rims, longitudinal striations and chatter marks. Titanium alloy debris produced arrays of very shallow scratches accompanying larger grooves. These larger grooves measured 20–110 μm wide and 0.4–1.9 μm deep.

EDS imaging showed the smears and islands contained the elements Ti, Al and V representative of the Ti6Al4V alloy. WLI imaging showed these metal deposits (250–900 um wide) were raised >10 um above the surface. Particularly conspicuous was evidence of considerable smearing on CoCr surfaces, with linear streaks ranging 150–300 μm wide. Bone cement debris proved incapable of grooving the CoCr surface, the only scratches observed were those comparable to normal carbide scratches.

Introduction

Femoral stem anteversion after total hip arthroplasty (THA) has always been assessed using CT scan in supine position. In this study, we evaluated the anteversion of the femoral prosthesis neck in functional standing position using EOS® technology with repeatability and reproducibility of the measurements. The data obtained were compared with conventional anatomic measurements.

In an effort to understand the role of metal ion analysis and how it relates to revision surgery and implant wear, four revised MOM cases were reviewed. The first case was revised for acute infection and is representative of the low bearing wear predicted by MOM simulator studies. Two of the four cases had apparent anterior subluxation as a result of hip hyperextension occurring with long stride gaits. The last case is a true hypersensitivity response to CoCr ions.

All four MOM prostheses were implanted by one surgeon and revised by the same surgeon approximately 6–8 years postoperatively. The implants had been positioned satisfactorily with inclination angles 45°–55° and anteversion angles 28°–42°.

Patient A (76 y/o female) with bilateral MOM hip replacements, was revised at approximately 8 years due to infection and had moderately elevated ions at the time of revision surgery (Co = 5, Cr = 2.3, Ti = 4). Only the femoral head was retrieved in this case. Retrieval analysis identified a well defined main-wear zone and one polar stripe. The CMM indicated there was minimal wear overall (form factor = 11 μm).

Patient B (33 y/o male) with bilateral MOM hip replacements, was revised at approximately 8 years due to pain, popping/catching sensations, and elevated ions (Co = 33, Cr = 17, Ti = 90). Intraoperatively, the implant was observed subluxing superiorly from the acetabular cup with anterior rotation of the leg. Both the femoral head and acetabular cup were retrieved. Retrieval analysis identified a well defined main-wear zone and multi-directional polar stripe formations similar to those reported on dislocated implants (Figure 1)[McPherson 2012, 2013]. The CMM indicated that overall wear was significant (form factor > 100 μm).

Patient C (77 y/o female) was revised at approximately 6 years due to pain, suspected implant loosening, osteolytic cysts determined by CT, and highly elevated ions (co = 164, Cr = 45, Ti = 33). Intraoperatively, there was evidence of wear including darkly stained tissue and osteolytic cysts. Both the femoral head and acetabular cup were retrieved. Retrieval analysis identified a well defined main-wear zone and one polar stripe. CMM indicated considerable wear (head form factor > 200, cup form factor >300).

Patient D (45 y/o female) was revised at approximately 6 years due to pain, apparent reactive response joint effusion, and moderately elevated ions (Co = 5, Cr = 6, Ti = 71). Only the femoral head was retrieved. Retrieval analysis identified a well defined main-wear zone and one polar stripe. Minimal wear was indicated by CMM (form factor = 21).

These four cases demonstrate distinct failure models of MOM hips and their respective metal ion results. Due to the diversity of patient location, a variety of clinical labs were utilized for this patient population. Caution should be used in interpreting metal ion analysis, as there are still no standards.

Figure 1: Retrieval analysis of stripe wear identified on femoral head from patient B.

Figure 2: Femoral head from patient C showing broader polar stripe associated with anterior subluxation in comparison to narrow polar stripe found on femoral head from patient A.

In recent years there has been growing interest in enhanced recovery regimes in lower limb arthroplasty due to potential clinical benefits of early mobilisation along with cost-savings. Following adoption of this regime in a district general hospital, it was observed that traditional dressings were a potential barrier to its success with ongoing wound problems in patients otherwise fit for discharge. The aim of this audit was to assess current wound care practice, implement a potentially improved regime and re-evaluate practice.

A prospective clinical audit was performed over a three month period involving 100 patients undergoing hip or knee arthroplasty. Fifty patients with traditional dressings were evaluated prior to change in practice to a modern dressing (Aquacel™ Surgical). Fifty patients were then evaluated with the new dressing to complete the audit cycle. Clinical outcome measures included wear time, number of changes, blister rate and length of stay. Statistical comparisons were performed using Mann Whitney or Fisher's Exact test (statistical significance, p<0.05).

Wear time for the traditional dressing (2 days) was significantly shorter than the modern dressing (7 days), p<0.001, and required more changes (0 vs. 3 days), p<0.001. 20% of patients developed blisters with the traditional dressing compared with 4% with the modern dressing (p=0.028). Length of stay was the same for the modern dressing (4 days) compared with the traditional dressing (4 days). However, in the modern group 75% of patients were discharged by day 4 whereas in the traditional group this took until day 6.

This audit highlights the problems associated with traditional dressings with frequent early dressing changes, blistering and delayed discharge. These adverse outcomes can be minimised with a modern dressing specifically designed for the demands of lower limb arthroplasty. Units planning to implement enhanced recovery regimes should consider adopting this dressing to avoid compromising patient discharge.

This study aimed to overcome the subjective nature of routine assessment of knee laxity and develop a repeatable, objective method using a hand-held force application device (FAD).

Eighteen clinicians (physiotherapists, consultants, trainees) volunteered to measure the coronal angular deviation of the right knee of a healthy volunteer using a validated non-invasive infrared measuring system. Effort was taken to ensure the knee flexion angle (∼2°) and hand positions were constant during testing. Three varus and valgus stress tests were conducted, in which maximum angular deviation was determined and subsequently averaged, in the following order of conditions: manual stress without the FAD up to a perceived end-point (before); with the FAD to apply a moment of 18 Nm; and again without the FAD (after). A repeated measures ANOVA was used to analyse the results.

All three groups of clinicians produced measurements of valgus laxity with consistent mean values and standard deviations (<1°) for each condition. For varus mean values were consistent but standard deviations were larger.

Valgus deviations varied significantly between conditions (p < 0.01), with deviations achieved using the FAD greater than both before (p < 0.01) and after (p < 0.05) indicating that the perceived endpoints were less than that achieved at 18 Nm. However varus perceived endpoints were no different to that achieved at 18 Nm, suggesting that clinicians usually apply a greater valgus moment than varus. Furthermore, the non-significant increase in valgus deviation between before and after (p = 0.123) is suggestive of a training trend, especially for trainees.

Our standardised knee laxity assessment may have a role in improving the balancing techniques of TKA and the diagnosis of collateral ligament injuries. Also, by quantifying the technique of senior clinicians, and with use of the FAD, the perceptive skills of more junior trainees may be enhanced.

Aim

With the link between obesity and Slipped Upper Femoral Epiphysis (SUFE) well established and a rising number of paediatric orthopaedic patients presenting with vitamin D deficiency, the aim of our study was to establish the incidence of vitamin D deficiency in SUFE patients and whether low vitamin D levels increases the time to proximal femoral physeal fusion post surgical fixation.

Aim

Shelf acetabuloplasty is part of the armamentarium for the treatment of Legg-Perthes-Calve disease. Surgeons have used it to increase the anterolateral cover of the deformed head in advanced stages of the disease. However, others, including the senior author, advocate its use for containment of the diseased femoral head earlier in the disease, for both the prevention of further femoral head extrusion and as an aid in the remodelling process. The current study presents the results of this procedure performed from August 1999 to February 2010.

Introduction

CT based systems that are used to create custom components and custom cutting guides in total knee arthroplasty (TKA) have variable methods for accounting for the thickness of remaining cartilage that may influence component sizing and bone resection. Little information has been published about the thickness of this cartilage, especially on the posterior femoral condyles. Failure to account for this cartilage may lead to under-sizing of the femoral component, or a reduction in the posterior condylar offset that may adversely affect flexion after TKA.

Introduction

While prosthesis survival in Total Knee Arthroplasty (TKA) exceeds 90% at 10 year, failures do occur. One area of concern has been the potential for metal allergy or metal sensitivity causing persistent pain, swelling or early failure of the implant in some patients. Definitive tests for diagnosing metal allergy and metal sensitivity have not been developed and this field remains controversial. In most cases where metal sensitivity is a concern, metals such as Chromium and Nickel are implicated. Despite the lack of good diagnostic tests for identifying these patients, several orthopedic prosthesis manufacturers have developed implants made of Titanium or ceramic designed for use in patients where concerns exist regarding metal allergy. In the absence of good diagnostic tests, use of these devices in patients that self identify is one option. To date, little information has been presented about the incidence of self reported metal sensitivity in patients undergoing joint replacement. This study was undertaken to determine the incidence of self reported metal allergy or sensitivity in patients undergoing total knee arthroplasty.

Introduction

Patellar resurfacing during Total Knee Arthroplasty (TKA) is controversial. Problems unique to patellar resurfacing may be influenced by available patellar component design. These issues include; over-stuffing (the creation of a composite patellar-prosthesis thickness greater than the native patella) that may contribute to reduced range of motion; and over-resection of the native patellar bone that may contribute to post-operative fracture. Prosthesis design may play a role in contributing to these problems. Component diameter and thickness are quite variable from one manufacturer to another and little information has been previously published about optimal component dimensions. This anatomic study was performed to define the native patellar anatomy of patients undergoing TKA, in order to guide future component design.

Aim

This study presents the early results of a novel procedure, both in timing and surgical technique, aimed to treat those cases of congenital hip dysplasia that present late or fail conservative treatment.

Background

Steroid injections can be used safely to treat trigger fingers. We aimed to determine the accuracy of referring General Practitioner (GP) diagnoses of trigger finger made to an upper limb surgeon. We also aimed to determine the efficacy of a serial two steroid injection then surgery technique in the management of trigger fingers.

Range of motion (ROM) is a well recognised outcome measure following total knee arthroplasty (TKA). Reduced knee flexion can lead to poor outcome after TKA and therefore identification at an early stage is important as it may provide a window for intervention with targeted physiotherapy, closer follow-up and in resistant cases possible manipulation or arthrolysis. ROM combines both flexion and extension and in contrast to flexion, fewer studies have recognised the importance of a lack of full extension or fixed flexion deformity (FFD) following TKA. A residual FFD can increase energy cost, decrease velocity during ambulation and result in pain with knee scores more likely to be diminished than if knee extension was normal. Recognition and early detection of FFD is therefore important. Methods of assessment include by visual estimation or goniometric measurement of knee flexion angle. While goniometers are inexpensive, easy to use and provide more accurate than visual estimates of angles, they have been shown to exhibit poor inter-observer reliability. Therefore they may not be sensitive enough to consistently identify FFD and therefore distinguish between grading systems based on absolute angular limits. The aim of this study was to investigate the accuracy of standard clinical ROM measurement techniques following TKA and determine their reliability for recognising FFD.

Ethical approval was obtained for this study. Thirty patients who were six weeks following TKA had their knee ROM measured. An infrared (IR) tracking system (±1°accuracy) that had been validated against an electro-goniometer was used to give a “true” measurement of the lower limb sagittal alignment with the knee fully extended and maximally flexed while the patient was supine. The patients were also assessed independently by experienced arthroplasty practitioners using a standardised goniometric measurement technique. For goniometric clinically-measured flexion (Clin_flex) and extension (Clin_ext) linear models were generated using IR-measured flexion and extension (IR_flex and IR_ext), BMI and gender as covariables. Data for extension were categorised in none, moderate and severe postoperative FFD as per Ritter et al. 2007 and agreement in classification between the two methods was assessed using the Kappa statistic.

For the linear models for Clin_flex and Clin_ext neither BMI nor gender were significant variables. Therefore the final models were:

Clin_flex = 0.54 + 0.66∗IR_flex (r²_adj = 0.521)

Clin_ext = 0.23 + 0.50∗IR_ext (r²_adj = 0.247)

The model for Clin_flex showed that the IR and clinical measurements coincided at approximately 90° so that for every 10° increase in flexion above 90° clinical measurement only increased by 7° but for every 10° decrease in flexion below 90° clinical measurement only decreased by 7°. The model for Clin_ext showed that the IR and clinical measurements coincided at approximately 0° so that for every 10° increase in FFD angle, clinical measurement only increased by 5° but if the knee went into hyperextension this would be underestimated by the clinical measure. In identifying FFD there was moderate agreement between the two measurements (κ = 0.44). Clinically nine patients were assessed as having FFD but the IR measurements showed 18 patients having FFD, of which nine patients were not identified clinically.

When assessing knee ROM following joint arthroplasty manual goniometric measurements provided a poor estimate of the range when compared to the “true” angle as measured with a validated IR measurement tool. When the knee was held in maximum flexion there was a tendency to both underestimate and overestimate the true angle. However when the knee was held in extension there was a tendency to underestimate which we believe is important as it would underreport both the frequency and magnitude of FFD. In our study, 18 patients had a moderate FFD as identified by the IR system, only half of which were identified by goniometer measurement alone. Studies of comparisons of both visual and manual goniometry measurements of the knee in maximum flexion with lateral radiographs have shown most errors involved an underestimate of true flexion. It has been concluded that it was safer to underestimate knee flexion angle as it would result in higher pick up rate of cases being performing less well. In contrast however, underestimation while in extension is less desirable as it fails to pick-up FFD which may have benefited from intervention had they been identified. It is known that residual FFD can increase energy cost and decrease velocity during ambulation with pain and functional knee scores more likely to be reduced. Recognition and early detection is therefore important. With the use of more accurate systems to identify and measure FFD, such as the one used for this study may in turn allow more timely treatment and therefore hopefully improved outcomes.

Clinical laxity tests are frequently used for assessing knee ligament injuries and for soft tissue balancing in total knee arthroplasty (TKA). Current routine methods are highly subjective with respect to examination technique, magnitude of clinician-applied load and assessment of joint displacement. Alignment measurements generated by computer-assisted technology have led to the development of quantitative TKA soft tissue balancing algorithms. However to make the algorithms applicable in practice requires the standardisation of several parameters: knee flexion angle should be maintained to minimise the potential positional variation in ligament restraining properties; hand positioning of the examining clinician should correspond to a measured lever arm, defined as the perpendicular distance of the applied force from the rotational knee centre; accurate measurement of force applied is required to calculate the moment applied to the knee joint; resultant displacement of the knee should be quantified.

The primary aim of this study was to determine whether different clinicians could reliably assess coronal knee laxity with a standardised protocol that controlled these variables. Furthermore, a secondary question was to examine if the experience of the clinician makes a difference. We hypothesised that standardisation would result in a narrow range of laxity measurements obtained by different clinicians.

Six consultant orthopaedic surgeons, six orthopaedic trainees and six physiotherapists were instructed to assess the coronal laxity of the right knee of a healthy volunteer. Points were marked over the femoral epicondyles and the malleoli to indicate hand positioning and give a constant moment arm. The non-invasive adaptation of a commercially available image-free navigation system enabled real-time measurement of coronal and sagittal mechanical femorotibial (MFT) angles. This has been previously validated to an accuracy of ±1°. Collateral knee laxity was defined as the amount of angular displacement during a stress manoeuvre. Participants were instructed to maintain the knee joint in 2° of flexion whilst performing a varus-valgus stress test using what they perceived as an acceptable load. They were blinded to the coronal MFT angle measurements. A hand-held force application device (FAD) was then employed to allow the clinicians to apply a moment of 18Nm. This level was based on previous work to determine a suitable subject tolerance limit. They were instructed to repeat the test using the device in the palm of their right hand and to apply the force until the visual display and an auditory alarm indicated that the target had been reached. The FAD was then removed and participants were asked to repeat the clinical varus-valgus stress test, but to try and apply the same amount of force as they had been doing with the device.

Maximum MFT angular deviation was automatically recorded for each stress test and the maximum moment applied was recorded for each of the tests using the FAD. Means and standard deviations (SD) were used to compare different clinicians under the same conditions. Paired t-tests were used to measure the change in practice of groups of clinicians before, during and after use of the FAD for both varus and valgus stress tests.

All three groups of clinicians initially produced measurements of valgus laxity with consistent mean values (1.5° for physiotherapists, 1.8° for consultants and 1.6° for trainees) and standard deviations (<1°). For varus, mean values were consistent (5.9° for physiotherapists, 5.0° for consultants and 5.4° for trainees) but standard deviations were larger (0.9° to 1.6°). When using the FAD, the standard deviations remained low for all groups for both varus and valgus laxity. Introducing the FAD overall produced a significantly greater angulation in valgus (2.4° compared to 1.6°, p<0.001) but not varus (p = 0.67) when compared to the initial examination. In attempting to reach the target moment of 18Nm, the mean ‘overshoot’ was 0.9Nm for both varus and valgus tests. Standard deviations for varus laxity were lower for all groups following use of the FAD. The consultants' performance remained consistent and valgus assessment remained consistent for all groups. The only statistically significant change in practice for a group before and after use of the FAD was for the trainees testing valgus, who may have been trained to push harder (p = 0.01). Standardising the applied moment indicated that usually a lower force is applied during valgus stress testing than varus. This was re-enforced by clinicians, one third of whom commented that they felt they had to push harder for valgus than varus, despite the FAD target being the same.

We have successfully standardised the manual technique of coronal knee laxity assessment by controlling the subjective variables. The results support the hypothesis of producing a narrow range of laxity measurements but with valgus laxity appearing more consistent than varus. The incorporation of a FAD into assessment of coronal knee laxity did not affect the clinicians' ability to produce reliable and repeatable measurements, despite removing the manual perception of laxity. The FAD also provided additional information about the actual moment applied. This information may have a role in improving the balancing techniques of TKA and the management of collateral ligament injuries with regard initial diagnosis and grading as well as rehabilitation.

Finally, the results suggest that following use of the FAD, more experienced clinicians returned to applying their usual manual force, while trainees appeared to use this augmented feedback to adapt their technique. Therefore this technique could be a way to harness the experience of senior clinicians and use it to enhance the perceptive skills of more junior trainees who do not have the benefit of this knowledge.

Knee alignment is a fundamental measurement in the assessment, monitoring and surgical management of patients with osteoarthritis [OA]. In spite of extensive research into the consequences of malalignment, our understanding of static tibiofemoral alignment remains poor with discrepancies in the reported weight-bearing characteristics of the knee joint and there is a lack of data regarding the potential variation between supine and standing (functional) conditions. In total knee arthroplasty [TKA] the lower limb alignment is usually measured in a supine condition and decisions on prosthesis placement made on this. An improved understanding of the relationship between supine and weight-bearing conditions may lead to a reassessment of current surgical goals.

The purpose of this study was to explore the relationship between supine and standing lower limb alignment in asymptomatic, osteoarthritic and prosthetic knees. Our hypothesis was that the change in alignment of these three groups would be different.

A non-invasive infrared position capture system (accuracy ±1° in both coronal and sagittal plane) was used to assess the knee alignment for 30 asymptomatic controls and 31 patients with OA, both before and after TKA. Coronal and sagittal mechanical femorotibial (MFT) angles in extension (negative values indicating varus in the coronal plane and hyperextension in the sagittal plane) were measured with each subject supine and in bi-pedal stance. For the supine test, the lower limb was supported at the heel and the subject told to relax. For the standing position subjects were asked to assume their normal stance. The change in alignment between these two conditions was analysed using a paired t-test for both coronal and sagittal planes. To quantify the change in 3D, vector plots of ankle centre displacement relative to the knee centre from the supine to standing condition were produced.

Alignment in both planes changed significantly from supine to standing for all three groups. For the coronal plane the supine and standing measurements (in degrees, mean(SD)) were 0.1(2.5) and −1.1(3.7) in the asymptomatic group, −2.5(5.7) and −3.6(6) in the OA group and −0.7(1.4) and −2.5(2) in the TKA group. For the sagittal plane the numbers were −1.7(3.3) and −5.5(4.9); 7.7(7.1) and 1.8(7.7); 6.8(5.1) and 1.4((7.6) respectively. This change was most frequently towards relative varus and extension. Vector plots showed that the trend of relative varus and extension in stance was similar in overall magnitude and direction between the three groups.

Knee alignment can change from supine to standing for asymptomatic and osteoarthritic knees, most frequently towards relative varus and hyperextension. The similarities between each group did not support our hypothesis. The consistent kinematic pattern for different knee types suggests that soft tissue restraints rather than underlying joint deformity may be more influential in dynamic control of alignment from lying to standing. In spite of some evidence suggesting a difference between supine and standing knee alignment a mechanical femorotibial (MFT) angle of 0° is a common intra-operative target as well as the desired post-operative weight-bearing alignment. These results indicated that arthroplasties positioned in varus intra-operatively could potentially become ‘outliers’ (>3° varus) when measured weight-bearing. Mild flexion contractures may correct when standing, reducing the need for intra-operative posterior release. These potential changes should be considered when positioning TKA components on supine limbs as post-operative functional alignment may be different.

We compared lower limb coronal alignment measurements obtained pre- and post-operatively with long-leg radiographs and computer navigation in patients undergoing primary total knee replacement (TKR). A series of 185 patients had their pre- and post-implant radiological and computer-navigation system measurements of coronal alignment compared using the Bland-Altman method. The study included 81 men and 104 women with a mean age of 68.5 years (32 to 87) and a mean body mass index of 31.7 kg/m² (19 to 49). Pre-implant Bland–Altman limits of agreement were -9.4° to 8.6° with a repeatability coefficient of 9.0°. The Bland–Altman plot showed a tendency for the radiological measurement to indicate a higher level of pre-operative deformity than the corresponding navigation measurement. Post-implant limits of agreement were -5.0° to 5.4° with a repeatability coefficient of 5.2°. The tendency for valgus knees to have greater deformity on the radiograph was still seen, but was weaker for varus knees.

The alignment seen or measured intra-operatively during TKR is not necessarily the same as the deformity seen on a standing long-leg radiograph either pre- or post-operatively. Further investigation into the effect of weight-bearing and surgical exposure of the joint on the mechanical femorotibial angle is required to enable the most appropriate intra-operative alignment to be selected.

Background

Vitamin D deficiency may increase predisposition to a number of paediatric orthopaedic conditions and the prevalence of vitamin D deficiency is increasing in children in developed countries. The aim of this study was to determine the epidemiology of vitamin D deficiency and insufficiency in children presenting to a regional paediatric orthopaedic service. We also examined the relationships between vitamin D status, social deprivation and ethnicity

Introduction

Opponents of patellar resurfacing during Total Knee Arthroplasty (TKA) note unique complications associated with resurfacing. Problems include over-stuffing (the creation of a composite patellar-prosthesis thickness greater than the native patella) that may contribute to reduced range of motion; and creation of a patellar remnant that is too thin (in order to avoid over-stuffing) that may contribute to post-operative fracture. Factors including surgical technique, prosthesis design and patient anatomy may contribute to these problems. This study was performed to define the native patellar anatomy, and to compare the effect of differences in component thickness between manufacturers.

Patients most at risk of osteoporosis are post-menopausal women. However, for many such women, presentation of osteoporosis is only made following their first fragility fracture. Often in the UK, osteoporosis investigation occurs following discharge, and any subsequent secondary prevention starts in the community. This may result in patients with osteoporosis not being investigated or not receiving correct prophylactic treatment.

143 post-menopausal women (av. age 77.7 years) starting secondary osteoporosis prophylaxis following fragility fractures requiring operative intervention were included in this retrospective study. Osteoporosis was defined by DEXA scan using the WHO criteria (122 hip fractures and 21 wrist fractures), following the UK's national guidelines for osteoporosis prophylaxis. Treatment was started following discussion and explanation of treatment with each patient, and either commenced by the surgical team during the acute hospital admission with the fracture, or in an out-patient setting within 6 weeks of the fracture by an orthopaedic specialist nurse. To check compliance, either the patient themselves or the patients' family physician was contacted.

Results showed that 120 of the women (83.9%, 102 hip fractures, and 18 wrist fractures) were still compliant with secondary osteoporosis prophylaxis at an average follow-up of 200 days (5 hip fractures lost to follow-up, 0 wrist fractures). 12 women with hip fractures died (0 wrist fractures), and 6 women stopped taking their prophylaxis (3 hip fractures, 3 wrist fractures): 4 for medical reasons, and 2 for unknown reasons. No women sustained further fractures.

Few studies have previously investigated compliance of osteoporosis secondary prevention, and our results compare favorably. We therefore recommend the prompt commencement of secondary prevention treatment by the orthopaedic surgical team following osteoporotic fractures.

Background

Malnutrition has been suggested to increase the risk of falls in frail elderly. It has been hypothesised that elderly, orthopaedic trauma patients may be malnourished. We conducted an observational study to identify if this was the case.

Metal on metal press-fit acetabular cups are the worst performing acetabular cup type with severe failure consequences compared to cups made from more inert materials such as polyethylene or ceramic. The cause of failure of these cup types is widely acknowledged to be multi-factorial, therefore creating a complex scenario for analysis through clinical studies. A factorial analysis has been carried out using an experimentally validated finite element analysis to investigate the relative influence of four input factors associated with acetabular cup implantation on output parameters indicating potential failure of the implantation. These input factors were: cup material stiffness; cup inclination; cup version; cup seating; and level of press-fit. The output parameter failure indicators were: wear; tensile strains in the underlying bone; bone remodelling; and cup-bone micromotions.

The factorial analysis concluded that the most significant influence was that of cup inclination on wear, and the second most significant was the influence of the level of press-fit on bone remodelling at the acetabular rim. Significant influence was also observed between version angle and wear, and cup-seating and micro-motion.

The results demonstrated the clear multi-factorial nature of implant failure and highlighted the importance of correct implant positioning and fit.

Knee alignment is a fundamental measurement in the assessment, monitoring and surgical management of patients with OA. In spite of extensive research into the consequences of malalignment, there is a lack of data regarding the potential variation between supine and standing (functional) conditions. The purpose of this study was to explore this relationship in asymptomatic, osteoarthritic and prosthetic knees. Our hypothesis was that the change in alignment of these three groups would be different.

Infrared position capture was used to assess knee alignment for 30 asymptomatic controls and 31 patients with OA, before and after TKA. Coronal and sagittal mechanical femorotibial (MFT) angles in extension (negative values varus/hyperextension) were measured supine and in bi-pedal stance and changes analysed using a paired t-test. To quantify this change in 3D, vector plots of ankle centre displacement relative to the knee centre were produced.

Alignment in both planes changed significantly from supine to standing for all three groups, most frequently towards relative varus and extension. In the coronal plane, the mean±SD(°) of the supine/standing MFT angles was 0.1±2.5/−1.1±3.7 for asymptomatic (p=0.001), −2.5±5.7/−3.6±6.0 for osteoarthritic (p=0.009) and −0.7±1.4/ −2.5±2.0 for prosthetic knees (p<0.001). In the sagittal plane, the mean±SD(°) of the supine/standing MFT angles was −1.7±3.3/−5.5±4.9 for asymptomatic (p<0.001), 7.7±7.1/1.8±7.7 for osteoarthritic (p<0.001) and 6.8±5.1/1.4±7.6 for prosthetic knees (p<0.001). The vector plots showed that the trend of relative varus and extension in stance was similar in overall magnitude and direction between the groups.

The similarities between each group did not support our hypothesis. The consistent kinematic pattern for different knee types suggests that soft tissue restraints rather than underlying joint deformity may be more influential in dynamic control of alignment from lying to standing. This potential change should be considered when positioning TKA components on supine limbs as post-operative functional alignment may be different.

Range of motion (ROM) is a well recognised outcome measure following TKA and combines both knee flexion and extension. In contrast to achieved flexion, fewer studies have recognised the importance of fixed flexion deformity (FFD). A post-operative FFD can adversely affect pain and functional knee scores and so its detection is important. The aim of this study was to investigate the accuracy of standard clinical ROM measurement techniques following TKA and determine their reliability for recognising FFD.

Thirty patients six weeks post-TKA had knee ROM measurements performed with an infrared (IR) tracking system of ±1 accuracy. The patients were also assessed independently by experienced arthroplasty practitioners using a standardised goniometric measurement technique. For goniometric clinically-measured flexion (Clin_flex) and extension (Clin_ext) linear models were generated using IR-measured flexion and extension (IR_flex and IR_ext), BMI and gender as covariables. Data for extension was categorised as FFD present or absent based on Ritter's criteria and agreement was assessed using Kappa.

For both models neither BMI nor gender were significant variables. Models were Clin_flex = 0.54 + 0.66∗IR_flex (r²_adj=0.521) and Clin_ext = 0.23 + 0.50∗IR_ext (r²_adj=0.247), showing that for every 10° increase in flexion, clinical measurement only increased by 7° and for every 10° increase in FFD angle, clinical measurement only increased by 5°. In identifying FFD there was moderate agreement between the two measurements (κ=0.44) with disagreement for nine patients all being patients with FFD that were not identified clinically.

For both flexion and extension there was a greater tendency for the goniometric clinical measurements to underestimate the actual angle. In the context of TKA outcome for maximum flexion this may be preferable to overestimating. In contrast, underestimating the degree of flexion when the knee is in the extended position is not desirable as it will potentially underreport the frequency and magnitude of FFD.

Purposes of the study

The most common fracture of the cervical spine in the elderly population is a fracture of the odontoid peg. Such fractures are usually not displaced and these are commonly treated non-operatively. Rarely though, peg fractures are displaced and then their management is less straightforward. This is in part because the group of patients who sustain them frequently have complex and pre-existing medical co-morbidities and in part because a new neurological injury may have been sustained as a result of the peg fracture itself.

Many options for the management of displaced peg fractures, both operative and non-operative have been described in the literature and discussion continues as to which technique is superior and in which patient population. The purpose of this study was to follow-up those patients who were managed operatively in our unit between 2007 and 2009.

Purpose of the study

To take a snapshot opinion of General Practitioner understanding of the prevalence, diagnosis and management of coccydynia.

Assessment of coronal knee laxity via manual stress testing is commonly performed during joint examination. While it is generally accepted that the knee should be flexed slightly to assess its collateral restraints, the importance of the exact degree of flexion at time of testing has not been documented. The aim of this study therefore was to assess the effect of differing degrees of knee flexion on the magnitude of coronal deflection observed during collateral stress testing.

Using non-invasive infrared technology, the real-time coronal and sagittal mechanical femorotibial (MFT) angles of three asymptomatic volunteers were measured. A single examiner, blinded to the real-time display of coronal but not sagittal alignment, held the knee in maximum extension and performed manual varus and valgus stress manoeuvres to a perceived end-point. This sequence was repeated at 5° increments up to 30° of flexion. This provided unstressed, varus and valgus coronal alignment measurements as well as overall envelope of laxity (valgus angle – varus angle) which were subsequently regressed against knee flexion.

Regression analysis indicated that all regression coefficients were significantly different to zero (p < 0.001). With increasing knee flexion, valgus MFT angles became more valgus and varus MFT angles became more. The overall laxity of the knee in the coronal plane increased approximately fourfold with 30° of knee flexion.

The results demonstrated that small changes in knee flexion could result in significant changes in coronal knee laxity, an observation which has important clinical relevance and applications. For example the assessment of medial collateral ligament (MCL) injuries can be based on the perceived amount of joint opening with no reference made to knee flexion at time of assessment. Therefore, close attention should be paid to the flexion angle of the knee during stress testing in order to achieve a reliable and reproducible assessment.

Introduction

Problematic bone defects are encountered regularly in orthopaedic practice particularly in fracture non-union, revision hip and knee arthroplasty, following bone tumour excision and in spinal fusion surgery. At present the optimal source of graft to ‘fill’ these defects is autologous bone but this has significant drawbacks including harvest site morbidity and limited quantities.

Bone marrow has been proposed as the main source of osteogenic stem cells for the tissue-engineered cell therapy approach to bone defect management. Such cells constitute a minute proportion of the total marrow cell population and their isolation and expansion is a time consuming and expensive strategy.

In this study we investigated human bone marrow stem cells as a potential treatment of bone defect by looking at variability in patient osteogenic cell populations as a function of patient differences. We produced a model to predict which patients would be more suited to cell based therapies and propose possible methods for improving the quality of grafts.

AIMS

We present a retrospective study of bilateral CDH. We analysed the correlation of complications to the confounding factors.

Estrogen fluctuations have been implicated in the soft tissue injury gender-bias due to the hormones effect on the viscoelastic properties. The isolated effect of estrogen on the mechanical behaviour of human tendon is unknown. The purpose of this study was to elucidate the effect of circulating levels of estrogen on the strain properties of the human Achilles tendon.

Twenty females (18–35 years) who were using the pill together with 20 matched, non-pill users, participated in this study. Non-pill users were tested at the time of lowest (menstruation) and highest (ovulation) estrogen whilst pill users, who exhibited constant and attenuated estrogen levels, were tested at menstruation and two weeks later. At each test session, maximal isometric plantarflexion efforts were performed on a calf-raise apparatus whilst synchronous real-time ultrasonography of the triceps surae aponeurosis was recorded. Connective tissue length (Lo) of the triceps surae complex was measured and tendon strain was calculated by dividing aponeurosis displacement during plantarflexion by Lo.

Repeated measures ANOVA revealed a significant (p < 0.05) main effect of subject group with significantly higher Achilles strain rates (16.1%) in the non-pill users compared to the pill users. Augmented Achilles tendon strain was associated with higher average estrogen levels in non-pill users.

Those results suggest that higher estrogen levels diminish the joint stabilising capacity of the triceps surae musculotendinous unit and may alter the energy storage capacity of the Achilles tendon during stretch-shorten cycle activities. This may result in a higher incidence of injuries during periods of high estrogen concentration.

Purpose

We describe two recent cases of intraosseous (IO) access resulting in amputation in critically ill infants and make contemporary recommendations on the safe practice of this technique.

Hip simulator studies on MOM bearings have historically involved ‘custom’ cetabular cups. I.e. having neither beaded layers nor biological coatings.

The aim of this study was to investigate wear using such MOM bearings and evaluate the potential wear and evaluate the potential for error in the gravimetric assessment.

Six x 38 mm HC Co-Cr bearings were supplied (Global and IO International Orthopaedics). The cups were received in ‘off-the-shelf’ condition with a cast Co-Cr beaded/HA-coated backing. To remove the HA-coating, the cups were pre-soaked in lemon juice for 4 days (articular surfaces shielded). Custom plastic fixtures were machined to fit the beaded contours of the cups. Test duration was 5Mc inorbital hip simulator (Shore-Western). MOM wear was estimated from serum ion contamination. Serum samples were digested and assessed using ICP/MS (Weck Labs Inc, CA).

The majority of the HA-coating was removed from the cups after four days of soaking inlemon juice after 21 days of soaking all cup weights appeared atable (within 1 mg). Reflected-light microscopy (RLM) showed no descernible signs of HA and the total weight loss due to HA remval averaged∼400mg.

During hip simulator there was no visual evidence of lost or broken beads, 3rd body abrasion etc (Sa<30nm). Both gravimetric and metal ion analysis showed consistent wear trends for all MOM cups. The MOM with the highest wear (predicted by ion analysis) demonstrated 1.2 mm (3)/Mc)OWR) at 5Mc. In comparsion, gravimetric analysis predicted an OWR of 1.3 mm (3)Mc for the same MOM, a difference of only 8%. Soaking beaded-HA cups in lemon juice and BCS proved effective in removing the coating.

The beaded cups remained stable in weight during the wear study and caused little discrepancy in gravimetric analysis (8%).

The method described did not lead to breaking of beads, elevated 3rd-body abrasion, cup damage or distorted wear scars.

Spinal cord injury following trauma is initially dealt with by acute hospitals. The early management including stabilization is usually performed by these centres. This is followed by onward referral to one of the Regional Spinal Injury Units.

There is concern of both sides of the fence regarding mobilization following spinal cord injury. The acute hospitals want to avoid the problems of prolonged recumbency and the Regional Spinal Injury Units wish to avoid the problems of early aggressive mobilization.

Therefore, we set out to discover if there was a standard approach to mobilising these patients following surgical stabilization, because of the oversubscribed resources of the spinal injury units and the wish to start mobilizing the injured as soon as possible.

A comparative audit of the Regional Spinal Injury Units in the UK and North American Units.

Regional Spinal Injury Units in United Kingdom and North America

Clear Management Plan

Mobilisation Schedule

We had replies from all Regional Spinal Injury Units in the UK and from seven in North America.

The Regional Spinal Injury Units all had differing approaches. Only a few were able to convey a clear management plan and mobilization schedule. Whereas the North American Units provided a ‘mobilize as able’ plan in all cases.

The North American Units had a ‘mobilize as able’ policy, whereas the UK units had a mixed approach. A coherent collaboration between the spinal surgeons stabilizing these injuries and the spinal injury units providing rehabilitation would improve patient management.

Peninsula Spinal Unit, Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Foundation NHS Trust, Exeter, UK.

A retrospective audit in 2000 of cases presenting with metastatic cord compression (MSCC) was conducted. In June 2009 we introduced the role of MSCC coordinator. We present the preliminary results from a 6 month comparative audit and discuss whether implementation of the NICE Guidelines have improved the care pathway.

Prospective cohort study with retrospective controlled group.

Adults with suspected MSCC

Length of time to MR imaging

% referred for surgical opinion

Length of time on bed rest.

% undergoing surgery

Retrospective audit 2000

38 cases confirmed MSCC.

11 did not have MRI and were treated on the basis of clinical symptoms.

Average time from admission to MRI 42 hours.

8 patients (21%) referred for surgical opinion.

None had surgery

38 had radiotherapy.

Spinal stability documented on 1 patient.

5.5 days average bed rest

Prospective audit 2009

54 patients referred to co-ordinator as suspected MSCC.

52 had MRI and 2 had CT.

Average time from referral to MRI 41 hours.

Average time for patients with neurological deficit 7.6 hours.

54 patients (100%) referred for surgical opinion.

12 patients had surgery (22%).

100% patients had spinal stability documented.

Average length of time on bed rest 2 days.

It is uncertain whether these results are attributed to the introduction of the NICE guidelines or improved awareness of condition. However we feel that NICE guidelines have improved the care pathway of patients with MSCC.

Statement of ethics and interests: Study was approved and registered with audit department.

Patients with solitary spinal metastases from Renal Cell Carcinoma (RCC) have better prognosis and survival rates compared to other spinal metastatic disease. Adjuvant therapy has been proven ineffective. Selected patients can be treated with Total En bloc Spondylectomy (TES) for solitary intra-osseous metastasis in the thoracolumbar spine secondary to renal cell carcinoma.

Five patients with solitary vertebral metastasis secondary to RCC underwent TES for radical resection of the spinal pathology after pre-operative embolisation. The procedure involves en bloc laminectomy and corpectomy with posterior instrumented fusion and anterior instrumentation with cage reconstruction following the spondylectomy. All patients were fully staged pre-operatively and assessed according to the Tokuhashi scoring system.

Recurrence of spinal metastasis and radiological failure of reconstruction

All patients demonstrated full neurological recovery and reported significant pain relief. One patient died at 11 months post-op due to a recurrence of the primary. The other four are well at 24, 45, 52 and 66 months post-op without evidence of recurrence in the spine. There were no major surgical complications.

Careful patient selection is required to justify this procedure. The indication is limited to solitary intra-osseous lesions where complete resection of the tumour is possible. The main advantage of this treatment is that it affords significant pain relief and restores spinal stability whilst minimizing local recurrence.

The assessment of knee laxity by application of varus and valgus stress is a subjective clinical manoeuvre often used for soft tissue balancing in arthroplasty or for diagnosis of collateral ligament injuries. Quantitative adjuncts such as stress radiographs have enabled a more objective measurement of angular deviation but may be limited by variations in examination technique. The aim of this study was to quantify clinical knee laxity assessment by measurement of applied forces and resultant angulations.

A novel system for measuring the manually-applied forces and moments was developed. Both hardware and software components underwent laboratory validation prior to volunteer testing. Two clinicians performed multiple blinded examinations on two volunteers and the corresponding angular deviations were measured using a validated non-invasive system with a repeatability of ±1° for coronal alignment. The distance between the kinematically-determined knee and ankle centres was used as the moment arm.

Comparison of single measurements of laxity showed a wide intra- and inter-observer variation (up to 3°). However, when the median value of repeated measurements was used there was good repeatability for both a single surgeon on different days and between the two clinicians with angular measurements agreeing within 1°. In spite of this agreement, the magnitudes of the tangential forces and moments applied varied between clinicians and did not correlate with the corresponding angular deviations.

It was not possible to standardise clinical examination using the current system. Orientation of the applied force with respect to the leg was not quantified and during force measurement it became apparent that the assumed tangential direction of application was not true. This may explain the lack of correlation between the force and angulation data. However, for quantitative measurement of coronal knee laxity using non-invasive laxity measurements, the use of a repeated measures protocol may be accurate enough for clinical application.

Aim

To evaluate the costs of performing revision hip and knee surgery at a District General Hospital.

Purpose This was an observational study to determine the prevalence of 25-hydroxyvitamin D (25[OH]D deficiency in our paediatric orthopaedic patient population.

Methods We have measured serum 25(OH)D levels in 44 paediatric patients who presented with bone pain. None of these patients had a pre-existing diagnosis of 25(OH)D deficiency. The age of patients ranged from 11 months to 16.5 years. There were 23 female and 21 male patients. The range of diagnoses included hip pain/irritable hip (4), Blount's disease (4), developmental hip dysplasia (7), genu valgum (3), Legg Calve Perthes’ disease (6), slipped capital femoral epiphysis (11), knee pain (3), other (6).

Those found to be 25(OH)D deficient underwent further biochemical investigation and were referred for paediatric endocrinology review with a view to vitamin D supplementation.

Results We found 9 patients (20%) with serum 25(OH)D levels of <20ng/mL indicating 25(OH)D deficiency. 17 patients (39%) had serum 25(OH)D levels in the range 20-30ng/mL indicating possible deficiency. The remaining 18 patients (41%) had a normal level of 25(OH)D. There was no association between low serum 25(OH)D level and any specific diagnosis, nor with gender or age of patient. There was, however, a statistically significant difference between the serum 25(OH)D level in those patients with unexplained joint pain (mean 22.5ng/mL) and those with other diagnoses (mean 30.7ng/ml) (P<0.05).

Conclusion Our results are consistent with other recent prevalence studies showing a concerning level of 25(OH)D deficiency among the paediatric population, and may suggest an increasing burden of disease in the coming years arising from the problem.

Purpose of Study

To assess the radiological outcomes of medial screw epiphyseodesis of the proximal femoral physis in the management of lateral growth arrest following treatment of developmental dysplasia of the hip.

Purpose of study

To determine whether hemiplegia causes abnormal torsion of the radius of the affected compared with the unaffected limb as demonstrated by MRI measurements, and to assess whether this correlates with the passive range of movement as measured clinically.

Purpose

Clinical coding is used to record information from patient admissions in the form of coded data used for monitoring the provision of health services and trends, research, audit and NHS financial planning.

The purpose of this study was to determine the normal angle of rotation of the axis of each finger using digital image analysis, whether the rotation of the digits is symmetrical in the two hands of an individual, and the reliability of this method.

Standardised digital photographic images were taken of thirty healthy volunteers. The palm of each hand was placed on a flat bench top with their fingers held in extension and adducted, to give an end-on image of all four fingers. Three independent observers analysed the images using Adobe Photoshop software. The rotational angle of each finger was defined as the angle created by a straight line connecting the radial and ulnar border of the nail plate and the bench top horizon.

The three observers showed Inter-Rater Reliability of 92%. The mean angles of rotation were: Index 13°, Middle 10°, Ring 5°, Little 12°. The differences in angle of rotation of the index and middle finger between the left and right hand were statistically significant (p=0.003, and p=0.002 respectively), demonstrating asymmetry between the two sides. The differences in angle of rotation of the ring and little finger of the left and right hand were not significantly significant (p= 0.312 and p=0.716 respectively).

In conclusion, symmetry was seen in the little and ring but not in the index and middle fingers. Digital image analysis provides a non-invasive and reproducible method of quantifying the rotation of normal fingers and may be of use as a diagnostic tool in the assessment and management of hand injuries.

Ceramic-on-ceramic alumina bearings (ALX) have demonstrated low wear with minimal biological consequences for almost four decades. An alumina-zirconia composite (BIOLOX-DELTATM) was introduced in 2000 as an alternative ceramic. This contains well-distributed zirconia grains that can undergo some surface phase transformations from tetragonal to monoclinic. We analyzed 5 cases revised at 1–7 years to compare to our simulator wear studies. For the retrieved DELTA bearings, two important questions were

how much tetragonal to monoclinic transformation was there in the zirconia phase and

The retrieval cases were photographed and logged with respect to clinical and revision details. The DELTA balls varied from 22mm to 36mm diameters. These had been mated with liner inserts varying by UHMWPE, BIOLOX-FORTE and BIOLOX-DELTA materials. Bearing features were analyzed for roughness by white-light interferometry, for wear by SEM, for dimensions by CMM and for transfer layers by EDS technique. Surface transformations on DELTA retrievals were mapped by XRD. The four combinations of 36mm diameter BIOLOX-FORTE and BIOLOX-DELTA were studied in a hip simulator, which was run in ‘severe’ micro-separation test mode to 5 million cycles. Wear rates, wear stripes, bearing roughness and wear debris were compared to the retrieval data.

In two DELTA ball cases, there were conspicuous impingement signs, stripe wear and black metallic smears. It is to be noted that the metal transfer sites (EDS) appeared to be from the revision procedures. The retrieved balls run with alumina liners showed monoclinic phase peaking at 32% on the particular surface and internal bore. On the fracture surface of case 1, the monoclinic content had increased to 40%. Various surface roughness indices were assessed on the bearings. The polished articular surfaces averaged roughness (Sa) of the order 3 nm, representing extremely smooth surfaces. The main wear zone was only marginally rougher (5 nm). In contrast the stripe wear zones had roughness of the order 55–140 nm.

In the laboratory, the DELTA bearings provided a 3–6 fold wear reduction compared to FORTE controls. Roughness of stripes increased to maximum 113nm on controls. Roughness of wear stripes showed FORTE with the highest and DELTA with the lowest values. DELTA bearings also revealed much milder wear by SEM imaging. Phase transformations showed peaks at < 30% for both main wear zone and stripe wear sites. It is hypothesized that the concentration of monoclinic phase reached a certain level due to compression contraint imposed by the alumina matrix. With implant wear, additional tetragonal grains of zirconia are exposed and these will also transform to tetragonal. This consistency between laboratory and retrieval studies confirmed the stable nature of the bearings. The BIOLOX-DELTA combination provides optimal potential for a clinically relevant reduction in stripe wear.

Computer-assisted technology has provided surgeons with intra-operative quantitative measurement tools that have led to the development of soft-tissue balancing algorithms based on surgeon-applied varus-valgus stress. Unfortunately these forces tend not to be standardised and the resultant algorithms may at best be surgeon-specific. Furthermore, these techniques are only available intra-operatively and rely on the rigid fixation of trackers to bone. The aim of this study was to develop a non-invasive computer-assisted measurement technique and assess the variation in collateral knee laxity measurements between different clinicians.

An image-free navigation system was adapted for non-invasive use by developing external mountings for active infrared trackers. A leg model with rigid tracker mountings was designed and manufactured for comparison. Multiple kinematic registrations of alignment were made for both the model and the right leg of a volunteer to quantify the soft tissue artefacts. Repeatability of the system was assessed by performing two registration processes on eight volunteers. Collateral knee laxity was assessed on a single volunteer by 16 participants of varying experience each applying a maximum varus and valgus knee stress. Two surgeons performed repeated examinations to assess intra-observer variation.

For repeated registrations of alignment, the SD of the non-invasive mounting (0.8°) was only a third higher than the leg model (0.6°) and the actual range was only 1° larger. The repeated alignment measurements on the volunteers showed a high level of agreement with an intraclass correlation coefficient of 0.93. Varus-valgus stress values showed poor inter-observer variation with a wide range of angles for both varus (1° to 7°) and valgus stress (0.5° to 5°). A Mann-Whitney test between the two sets of repeated tests showed that both varus stress and overall laxity were significantly different (p< 0.0001) but that valgus stress was marginal (p=0.052). Intra-observer measurements overall appeared more consistent.

Soft tissue artefacts did not significantly reduce the repeatability of the assessment of coronal knee alignment using a navigation system and this provided a non-invasive technique for assessing coronal knee laxity. The perception of an ‘end-point’ varied significantly between different clinicians and although there may be a role for surgeon-specific algorithms, to use this quantitative data more widely there is a need to standardise the forces and moments applied.

Computer-assisted surgical techniques in knee replacement procedures have been shown to increase the accuracy of implant positioning and reduce the incidence of alignment and soft-tissue balancing “outliers”. The use of this technology as a training tool is less widely reported. However, the recent implementation of the EWTD 48-hour working week for junior doctors has focussed attention on the issues of surgical training and experience. Recent evidence from trainee logbooks has shown a significant downward trend in operative exposure and this is forcing changes in the principles of how training should be delivered. Trainees are actively required to demonstrate operative competence in order to progress but are increasingly faced with limited opportunities to acquire these skills. On the other hand, trainers also face difficulties with the prospect of supervising less accomplished trainees which raises ethical issues of patient protection. We present a trainee’s perspective of experience gained in a unit routinely using computer-assisted technology and highlight the potential to enhance the learning process.

Navigation systems provide constant visual and numerical feedback via a computer simulated interpretation. Initially this displays relevant functional anatomy, helps in the identification of anatomical landmarks and demonstrates sagittal and coronal plane deformities which can be difficult to accurately assess “by eye”. Computer-assisted systems have the benefit of displaying only bony anatomy which improves visualisation. This can then be compared to the palpable, clinical deformity on the table. The geometry of the native knee is also made clear with the navigation system leading to a better understand of the objectives of TKR. There are some aspects of the biomechanics of the knee which are difficult to appreciate, such as the changes in varus-valgus alignment during flexion and extension. This may be very subtle and difficult to pick up manually but can look quite dramatic on the computer.

The position of cutting jigs which are held to the bone by pins can be altered by inadvertently lifting or hanging on them with the saw, when making the bone cuts. Additionally the cut can be altered by advancing the cutting block closer to the bone, for example if cutting the tibia with a posterior slope. Both these effects can be quantified by using the navigation tools to confirm the cut that has been made. Trainers can have the benefit of seeing the alignment and confirming the cuts made by a trainee without having to get closely involved with the operation. Cementation technique is also open to scrutiny with the ability to compare pre and post cementation alignment.

The positive feedback obtained from computer assisted surgery is educational to the trainee, by giving an undisputable computer generated graphic of what they are doing during the different stages of total knee arthroplasty. It also shows what has been achieved at the end of the procedure. This can give both the trainer and trainee more confidence in the procedure and ensures patient safety.

Effective utilisation of blood products is fundamental. The introduction of Maximum Surgical Blood Ordering Schedules (MSBOS) for operations provides guidance for effective cross-matching. A retrospective analysis of blood ordering practices was undertaken to establish an evidence-based MSBOS for revision THR and TKR. The impact of the use of intraoperative cell-salvage devices was also assessed.

Methods: The patient database was searched for cases of revision THR and TKR undertaken over 58 months. These records were then cross-referenced with the transfusion database. The cross-match to transfusion ratios (CTR) and transfusion indexes (TI) were calculated using this data.

The gold standard for the CTR is 2:1 or less. The TI establishes the likelihood of blood being transfused for a certain procedure. If the TI is less than 0.5, then cross-matching blood is considered unnecessary.

Results: For revisions of non-infected THR (n=269), the CTR=2.24 and TI=1.67. In infected cases (n=69), CTR=2.16 and TI=1.68.

In revisions of non-infected TKR (n=95), the CTR=4.33 and TI=0.48. In infected cases (n=54) the CTR=2.16 and TI=1.35.

There was considerable change in the practice of ordering cross-matched blood following the introduction of intraoperative cell-salvage devices (Revision THR: CTR=1.93, TI=0.84; Revision TKR: CTR=1.20, TI=0.16)

Discussion: The analysis confirmed that more blood was requested than was actually required. Overall the results suggest that cross-matching is still necessary for both the non-infected and infected revision THR but the number of units requested could be reduced to 2 units. In revision TKR, transfusions were more likely in infected cases and, a ‘group & save’ may be sufficient for non-infected cases.

The introduction of this MSBOS in conjunction with intraoperative cell-salvage, could promote blood conservation and financial savings.

The aim of this study was two-fold; firstly, to investigate the construct validity of the Disability of the Arm, Shoulder and Hand (DASH) score in patients following injuries to the upper and lower limbs, and to confirm that DASH score does not measure disability solely attributed to the upper limb. Secondly, to create a modified DASH questionnaire (M2 DASH) with fewer questions that can discriminate clearly between disabilities due to problems at the upper limb, and is more specific to the upper limb.

Patients were asked to fill in the DASH questionnaire in a fracture clinic following ethical approval. This included upper limb injuries (79), lower limb injuries (61) and control subjects (52). The median DASH scores for the three groups were 57, 16 and one respectively. The DASH scores varied significantly between the three groups (Kruskal-Wallis: p< 0.001); the scores for the upper limb group were higher than the lower limb group, and the scores for the lower limb group was higher than the control group (Mann-Whitney: p< 0.001). The M2 DASH questionnaire was developed using questions specific to the upper limb and included questions 1–4, 6, 13–17, 21–23 and 26–30. The median M2 DASH scores for the three groups were 50, 7 and 0 respectively. The revised questionnaire score was then calculated for the upper limb group and a correlation study showed good correlation between the two questionnaires.

Our study shows that the original DASH questionnaire is not specific for the upper limb. This has important implications in measuring response in injuries and disease that involve both upper and lower limbs. We have devised a revised questionnaire that we suggest is referred to as M2 DASH questionnaire. The M2 DASH questionnaire has the advantage of being more specific for the upper limb than the DASH questionnaire.

A large proportion of our patients are not salaried and many had expressed concerns about the amount of time taken off work following carpal tunnel surgery. Impressions were formed from information given by other health professionals or by friends and relatives who had previously undergone surgery. Some patients declined surgery because of their concerns over this particular issue. We therefore set out to challenge these traditional beliefs. This prompted us to adopt a more aggressive postoperative approach by encouraging immediate and unrestricted hand use following surgery. We found that patients were able to tolerate early activity and were able to return to work sooner than they had expected. For the purposes of this study, our aim was to identify when a return to any form of meaningful employment occurred, such that the individual was earning a salary. Consequently, we did not differentiate between the individual returning to either light or full duties. Subsequently, in a cohort of 494 patients prospectively studied, we have seen 93.1% patients return to work by two weeks and 99.4% by four weeks.

This has obvious benefits in terms of reducing loss of income. Individuals undergoing surgery now do not have to be concerned with taking lengthy periods of time off work with the financial implications for them and their families.

There are obvious economic implications to our findings. An individual back at work should not be claiming related sickness benefit. The Confederation of British Industry (May 2007) report a cost of £76.70 for each day an employee is off work due to sickness. An individual who is able to return to work even one week earlier than previously would have been expected following carpal tunnel surgery could theoretically produce a saving to the economy of £383. In this series there were 318 (64.4%) patients in employment indicating a potential economic saving of £121,794. Given that nationally there are about 50 000 carpal tunnel procedures carried out each year then the potential savings are significant.

There may be a number of reasons for our observations. The absence of a bulky restrictive dressing and sling following surgery clearly allows immediate mobilization to occur. Our service allows the development of a close professional relationship based on trust between the operator and the patient. This ultimately reassures patients who, we believe, feeling more involved in decisions about their post-operative care, are consequently well-motivated and have the confidence to use their hand immediately following surgery. We have seen a low postoperative complication rate in this group of patients, in particular, a low incidence of swelling, stiffness and scar sensitivity. Reasons for these low complication rates are unclear, but we would suggest that early mobilisation protects patients against these particular problems.

Fractures of the odontoid peg are relatively common in elderly people. Often they are minimally displaced and can be treated with a collar. However, a fracture which is displaced significantly may be difficult to manage. We describe the case of an 80-year-old man with a fracture of the odontoid peg which was completely displaced and caused respiratory distress. After initial closed reduction and application of a halo jacket, open and internal fixation was undertaken and relieved his symptoms. It is a safe and effective way to manage this injury.

Introduction: Methicillin-sensitive staphylococcus aureus (MSSA) has been the predominant aetiological agent in acute osteomyelitis (AHO) in children. Recent studies from the United States have demonstrated an increase in community-acquired Methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, which have been linked to increased morbidity.

Aim: a) to compare the patterns of AHO including the incidence of CA-MRSA in two tertiary children’s hospitals in Canada (The Hospital for Sick Children) and the United Kingdom (Southampton General Hospital) respectively, b) to compare the clinical course of MSSA versus CA-MRSA AHO in children in these two institutions.

Method: A retrospective review was carried out of all children up to 16 years, who were diagnosed with AHO at both centres over a five-year period. Demographic information, diagnostics, aetiology, treatment and outcomes was collected for comparison across both institutions and between MSSA and CA-MRSA identified patients.

Results: 99 cases of AHO were identified in Toronto (HSC) and 82 cases in Southampton (SGH) over the given time frames. The male: female ratios were 1.5:1 at HSC and 1.7:1 at SGH. The most commonly identified organism at both sites was MSSA, representing 42% of cultures at HSC and 22% at SGH. 2 Cases of CA-MRSA were identified at HSC, while 1 case was identified in Southampton, confirmed to be PVL-positive. No cases of Haemophilus influenzae were identified at either site. There were no significant differences in the median lengths of stay, rates of operative intervention, or complications between the two institutions. CA-MRSA cases were on average younger (7.5 yrs vs 9 yrs) and were all girls, compared with 32% girls in the MSSA group. CA-MRSA patients had similar initial laboratory profiles with the MSSA patients, except for significantly higher C-Reactive Proteins (200 vs 64) (p < 0.05). CA-MRSA patients experienced a significantly longer hospital stay (23 vs 8 days); were more likely to undergo surgical intervention (2/3 vs 34/59); were treated with longer duration of IV antibiotics (34 days vs 10.5 days); and longer total duration of antibiotics (61 days vs 46 days). 1/3 CA-MRSA patients required admission to the ICU for sepsis

Conclusions: MSSA remains the predominant aetiological agent in AHO at two large children’s hospitals in Canada and the UK. The patterns of infection are similar at both sites. CA-MRSA AHO infections have been identified at both centres, and although these remain uncommon, they are associated with a more severe clinical course. One can expect the incidence of CA-MRSA strains to rise, necessitating increased vigilance.

Aim: To investigate the magnitude of revenue lost by the Department of Trauma and Orthopaedics at Ports-mouth Hospitals NHS Trust in 2007 as a result of providing outpatient viscosupplementation joint injections.

Methods: Data was collated on all outpatient intra-articular hyaluronic acid viscosupplementation performed by our department in 2007. Information on existing HRG tariffs for orthopaedic outpatient attendances as well as clinical coding of joint injections by our department was also gathered.

Results: The 2007/2008 tariffs for orthopaedic outpatient first and follow-up appointments were £147 and £73 respectively for adults, and £157 and £85 respectively for children (under 17 years of age). No additional mandatory tariff currently exists for joint injections performed in the outpatient setting. During our study period, the cost of a dose of viscosuplementation (Hyaluronic acid 60mg/ 3 ml) varied between £213 and £248. A total of 812 doses of viscosupplementation were administered to outpatients by our department resulting in pharmaceutical costs of £175,126. Only 751 cases of outpatient appointment with joint injection (all types) were recorded and coded by the department.

Conclusions:

As long as no mandatory DoH tariff exists for out-patient joint injections, outpatient viscosupplementation remains an expensive service for trusts to provide and may warrant rationalisation.

Suggestions for improved wear performance of total knee replacements have included replacement of standard CoCr femoral components with ceramic. Yttria-stabilized zirconia (y-TZP) was introduced as high-strength and high toughness ceramic as an alternative to alumina ceramic. Since the introduction of zirconia in 1985, the clinical outcomes and successes for hip joint have been controversial. Y-TZP ceramics have been studied both experimentally and clinically. Magnesia-stabilized zirconia (Mg-PSZ) also appears promising for total knee replacements (TKR).

Mg-ZrO2 and CoCr femoral condyles were compared in the VanguardTM knee configuration (Biomet Inc, IN). Molded tibial inserts (GUR1050) were gamma-irradiation sterilization to 3.2-Mrad under argon. Knee simulation was conducted on a 6 station simulator (Shore Western Manufacturing, Monrovia, CA). Motion included 20 degrees of flexion/extension, 5 degrees of internal/external rotation and 5 mm of AP-translation. All knee components were subjected to 6 million cycles of normal walking (2.9 kN max, freq 1.4 Hz). Lubricant was 50% alfa-calf serum diluted to 20 mg/ml protein and using EDTA additive. Test duration was 6 million cycles (6-Mc), and wear was measured by weight-loss techniques.

For wear trending of CoCr/PE and MGZ/PE, linear wear trends were apparent from 1 to 6 Mc test duration. The control implants (CoCr/PE) showed excellent linear trending (regression coeff r> 0.99) with wears rate averaging 6.3 mm3/Mc. These data showed good control of experimental variance (< 10%). The ZrO2/PE combination showed good linear trending (r > 0.86) with wear rate averaging only 0.8 mm3/Mc. This set also showed good control of experimental variance (< 15%. The MGZ/PE wear was 8-fold reduced from that of CoCr/PE.

The laboratory knee wear simulation appeared very supportive of femoral condyles of Mg-stabilized zirconia. Such implants may provide excellent performance for active patients who may risk high wear rates over many years of use.

While there are many variation laboratory and clinical studies using metal-on-metal (MOM) bearings after introduction of the 28mm MOM THR in 1988, the mapping of wear phenomena in such retrieval cases has been mimimal. In laboratory study, 28mm MOM bearing’s wear-rate was low with “run-in” and “steady-state” than large diameter MOM without theory of fluid-filum lubrication. In clinical results were not superior to the same way of laboratory study. We present a detailed analysis of 33 retrieved MOM hip bearings with 1–11 years follow-up,

We compiled 33 retrieval cases (MetasulTM: Zimmer/CenterPulse Inc., Austin, TX) including clinical information, ion concentrations from ball diameters, cup designs and stripe wear damage. The bearing surfaces were mapped using reflected light microscope (RLM), white light interferometer (Zygo Newview 600, Zygo.) and SEM(XL-30 FEG). Wear maps were constructed according to types of surface wear identified.

Patients ranged from 36 to 76 years of age (Means: 56.9 years); 54% were males. Main causes for revision were progressive radiographic lines around the cups, osteolysis and pain. The 28mm ball diameter was used in 86% of cases (largest = 52mm ball). The CoCr liner incorporated a polyethylene adaptor in 75% of cases. Cup diameter > 50mm was present in 75% of cases. Eight femoral stems were recovered and all showed major impingement marks around the neck and five also had a metallosis (Mode-4A). Stripe wear was evident on 71% of CoCr balls with medial stripes twice as common as lateral. Stripe wear was identified in 25% of CoCr liners and extended 25–160° circumference around the liners. Clear liner rim damage was present in 10 (30%) and 3 demostrated severe damage of polyethelene adaptors.

There are many limitations to such retrieval studies. These data are biased to cases that failed due to hip pain, radiographic signs of progressive osteolysis and some with high levels of metal ions. There was also the bias of having predominantly a CoCr sandwich design (polyethylene adaptor in 75% of cases). In early 1980s, the thin walled UHMWPE cup was introduced and used larger diameter balls for decreased risk of dislocation. However, unfortunally these big-ball cups produced significant PE wear debris, and diameter trends were returned to the Chanley’s small-ball paradigm again. In the same time (late of 1980’s), these second-generation MOM (28,32mm) was introduced for low wear characteristics alternate THR bearings, with sacrificing of joint stability and motion range. However, use of the small ball added well-known risks of impingement, subluxation and dislocation with rigid cups. In this study, using the ‘damage modes’ from McKellop, normal mode-1 wear occurred in only 14% of cases whereas modes 2–4 had an incidence approaching 30% each and signs of cup impingement were evident in 64% of cases. Thus summarizing MOM wear phenomena in “small” 28mm sandwich cup designs, there was retrieval evidence showing that damage modes 2–4 likely placed these patients at risk for adverse wear effects.

Wear in polyethylene liners appears to be exacerbated by 3rd-body abrasion effects with the CoCr ball combinations used for total hip replacements. This has implications for various wear modes encountered in patients. Yet clinical and laboratory studies have offered weak and sometimes contradictory wear relationships with respect to crosslinking, ball diameter and roughness, and 3rd-body wear effects. Our hip simulator model investigated the effect of severe wear challenges by 3rd-body cement particles, using large diameter CoCr and alumina balls, with highly-crosslinked polyethylene liners (HXPE) irradiated to 75kGy compared to contemporary controls (CXPE 35kGy).

The polyethylene liners were gamma-irradiated to 35/75kGy under N2 (CXPE/HXPE). We used 32 and 44mm CoCr balls (ENCORE, Austin, TX) and 44mm alumina-ceramic (Biolox-forte, CeramTecAG) as ‘scratch-resistant’ standard of comparison. We compared 5 bearings pairs with different roughness characteristics using both new and pre-worn polyethylene liners. A 12-station orbital hip simulator with a physiological load profile (0.2kN–3kN load, frequency 1Hz) with cups mounted in “Inverted- position”. Diluted bovine serum (Hyclone Inc., Logan, UT) was used as lubricant (20mg/ml protein, 400ml volume). In phase I, all cups were run in standard (‘clean’) lubricant for 1.5 million cycles (1.5Mc). In phase II, the liners were run in a PMMA slurry of serum (5mg/ml) for 2Mc. In phase III, implants were run ‘clean’ for 1.5Mc. Wear-rate was measured each 0.25Mc event, and surface roughness measured by SEM (XL-30FEG) and white light interferometry (Newview600, Zygo) every 0.5Mc.

In phase I, Wear withnew CXPE and HXPE liners averaged 182mm3/Mc and 30mm3/Mc. Thus the HXPE liners averaged a 6.0-fold wear reduction compared to controls. Compared to new liners, the pre-worn CXPE and HXPE liners showed 10% and 25%, greater wear respectively. Here it was noted that CoCr balls maintained similar roughness (Sa:8–12nm). And alumina balls showed small, gradual increase (Sa: 2 to 2.5nm). The HXPE maintained a superior finish to CXPE controls. Roughness revealed a gradual decrease with time, pre-worn CXPE from 0.28 to 0.15um and pre-worn HXPE from 0.18 to 0.04um (Sa). In contrast, new HXPE showed a dramatic smoothing (0.8 to 0.1um) 92.8% decreased in first 0.5Mc. These effects have not been previously quantified. In phase II with abrasive mode, the liner wear-rates increased dramatically by 6 and 80-fold for CXPE and HXPE, respectively. These data confirmed that HXPE was sensitive to ‘severe’ wear against CoCr and alumina balls. In phase III, the polyethylene roughness dropped by > 90% and wear decreased to phase-I values. The wear-ratio was now 2:1 for CXPE:HXPE as predicted by the ‘diameter’ and ‘crosslinking’ algorithms.

It was clear that surface roughness was not a confounding factorfor either the CoCr or alumina balls. It was the polyethylene surface roughness that appeared to influence wear rates. Our analysis showed that there was a transient due to patches of abrasive cement transferring onto CoCr ball surfaces. Overall the actual roughness of the CoCr balls did not change and was therefore not a factor in increased polyethylene wear.

FDA approval of metal-on-metal (MOM: 28, 32mm) bearings has provided 10 years of clinical experiences in USA. However there has been no detailed mapping of wear phenomena in retrieval cases. We present an analysis of 28 cases, MOM retrievals with 1 to 10 years follow-up, radiographic reviews and metal ion studies. Ball diameters ranged from 28mm to 42mm. Two balls were the early design with skirts. Main indicators for revision were the progressive radiographic changes indicative of osteolysis, with associated hip pain. Approximately 54% of patients were males and ages ranged from 36 to 76 years of age. Only 7 femoral stems were recovered but all had impingement marks. Only three cases lacked any evidence of stripe wear and these were in very elderly patients. Approximately 85% of these cases showed some evidence of stripe wear and multiple stripes were clearly visible on 50% of the femoral balls. The medial ball stripes were twice as common as lateral. Stripe wear was identified in 25% of CoCr liners.

In the hip simulator studies generally show ‘run-in’ wear rates of 1–7mm3 per million cycles (Mc). We noted that above the 5mm3/Mc threshold, the serum generally appeared black. In contrast, the ‘steady-state’ wear rates of 0.1–1.6 mm3/Mc showed the true potential of MOM bearings. However there were often examples of higher wear (7–20 mm3/Mc), which gave confounding trends in published studies. Our studies of metal ions in the simulator lubricant provided a very accurate representation of MOM wear.

There are many limitations in comparing in-vitro to in-vivo wear performance. Our retrieval data are biased to cases that failed due to hip pain, had radiographic signs of progressive osteolysis and some showed high levels of metal ions. There was also the bias of having predominantly a CoCr sandwich design (polyethylene adaptor). Use of the small ball added the well-known risks of impingement, subluxation and dislocation with rigid cups. Using the ‘damage modes’ from McKellop, we found only normal Mode-1 wear to be rare in these cases, whereas Modes# 2–4 had an incidence approaching 30% each. Signs of impingement were evident in 85% of our cases. Thus summarizing these MOM wear phenomena in retrieved 28mm sandwich cups, the evidence implicated impingement and 3rd-body wear modes (#2–4) as the clinical risk for adverse wear effects at 10 years follow-up. The in-vitro wear studies have not yet simulated such adverse clinical effects.

Introduction: Patients with solitary spinal metastases from Renal Cell Carcinoma (RCC) have better prognosis and show longer survival rates compared to other spinal metastatic disease. Adjuvant control by chemotherapy and hormonal therapy has been proven ineffective to treat this relatively radio resistant tumour, which can often present with both back pain and neurological deficit. Selected patients can be treated with Total En bloc Spondylectomy (TES) for solitary intra-osseous metastasis in the thoracolumbar spine secondary to renal cell carcinoma.

Methods: Four patients with solitary vertebral metastasis secondary to RCC underwent TES for radical resection of the spinal pathology after pre-operative embolisation. The procedure involves en bloc laminectomy and corpectomy with posterior instrumented fusion and anterior instrumentation with cage reconstruction following the spondylectomy. All patients were fully staged pre-operatively and assessed according to the Tokuhashi scoring system to determine predictive life expectancy.

Results: All patients demonstrated full neurological recovery and reported significant pain relief. One patient died at 11 months post-op due to a recurrence of the primary in the nephrectomy bed. The other three are alive and well at 33, 40 and 54 months post-op with no radiological evidence of tumour recurrence in the spine. There were no major surgical complications.

Discussion: Careful patient selection is required to justify this procedure. The indication is best limited to solitary intra-osseous lesions where complete resection of the tumour is possible. The main advantage of this treatment is that it affords significant pain relief and restores spinal stability whilst minimizing local recurrence.

Conclusion: TES can improve symptomatic control of isolated solitary spinal metastases of the thoracolumbar spine in Renal Cell Carcinoma.

From 1985 metal-on-metal (MOM) designs of resurfacing (RSA) and total hip arthroplasties (THR) have been available over a large diameter range (28–60mm). In-vitro studies indicated satisfactory low wear performance for all designs and diameters tested (wear = 0.1 to 7 mm3). While reports from many centers have been encouraging, some have reported adverse effects. We reviewed clinical and metal ion studies in large diameter retrievals and compared these to 28mm MOM cases. Patients with the latter THR ranged 36–76 years of age and were followed 9–11 years. Main finding in our revisions was osteolysis and pain. The 28mm ball was represented 86% of cases; 71% balls had stripe wear. For liners, 25% had circumferential stripe wear and impingement was evident in 64% cases. Seven cemented stems were recovered with impingement marks; 26 stems were undamaged and therefore not revised. Using the concept of ‘damage modes’ from McKellop, normal wear mode #1 was evident in only 14% of 28mm retrievals whereas incidence of ‘abnormal’ modes #2-4 approached 30% each. Thus the 28mm MOM appeared susceptible to impingement risks with CoCr liners. Summarizing MOM retrievals, damage modes 2–4 were most likely implicated in revisions. The performance of such ‘small diameter’ THRs will be contrasted to our large diameter THR and RSA experience. The questions to be reviewed include, how much of the reported MOM adversity was predictable and how much risk was due to

wear of small diameter MOM,

Ceramic-on-ceramic bearings (ALX: pure alumina) have been used for human hip joints for almost 40 years. However an alumina matrix composite with zirconia (AMC) was introduced in year 2000 as a high-strength ceramic with almost double the fatigue resistance (AMC = 80.5%ALZ and 18vol% ZrO2). However we have not found any retrieval studies reported for this new ceramic bearing.

Wear maps were generated on three retrieved AMC femoral heads (28 and 36mm diameters) using x-ray diffraction, roughness and SEM imaging techniques. The wear study ran a physiologically appropriate, micro-separation test on 36mm ceramic balls and liners (AMC/ALZ). Wear rates were determined for the four combinations of balls and cups (ALX:AMC) with mapping of main-wear and stripe-wear zones, surface-roughness and analysis of debris morphology. In addition, the zirconia transformation to monoclinic phase was studied in AMC bearings

The retrieval study showed for the first time the wear phenomena occurring on three retrieved AMC femoral heads (at 1, 3, 6 years). Two had been paired with alumina liners and one with a polyethylene liner. Case-1 featured a 36mm ball in an UHMWPE socket, case-2 was an intact 28mm AMC ball and case-3 had a fractured ball from an IDE study. Laser interferometry and SEM were used to image ceramic wear and x-ray diffraction for analysis of transformation in the zirconia phase. Main-wear zones, stripe-wear zones, metal contamination and sites of implant impingement were also characterized. Surface roughness and in-vivo aging were quantified for both non-worn and worn areas. The SEM studies showed well-preserved articular surfaces, some with faint parallel scratches still evident. The latter likely represented the manufacturer’s original polishing marks. Multiple stripe-wear sites were identified with roughness 25–65nm (Sa) whereas polished main-wear zones averaged very low at 2–3nm. Metal impingements sites stained black with transfer of titanium increased roughness up to 140nm. Mildly worn areas of case-2 AMC ball averaged 10% transformation in the zirconia phase (tetragonal to monoclinic). In the stripe-wear zones, the monoclinic phase increased to 30%. The taper-bore and fracture surfaces in case-3 averaged 30% to 40% monoclinic, respectively. The stripe-wear zones and black metal contamination on these retrieved 28mm balls were correlated to multiple impingement sites on the rim of the alumina liners and titanium shells.

The laboratory model produced stripe wear on the ceramic balls and liners. The AlX/AlX controls produced the highest run-in and steady-state wear rates at 6.3 and 2mm3/Mc respectively). In contrast, the AMC/AMC combination produced the lowest wear rates at 0.5 and 0.1 mm3/Mc, respectively). With hybrid ball:cup combinations (AlX:AMC; AMC:AlX) the wear rates were similar and showed a 3-fold reduction compared to controls. In hybrid pairings, the AMC ceramic wore preferentially more than its AlX counterpart, regardless if present as a ball or cup implant. Thus the AMC ball contributed 66% to AMC/AlX total wear whereas the ALZ ball contributed only 33% of the total AlZ/AMC wear.

This study appears to be the first documentation of wear in retrieved AMC bearing surfaces. In general, the AMC surfaces worn in-vivo corresponded well to our in-vitro wear model. The stripe-wear zones in AMC femoral heads had rougher surfaces and higher monoclinic transformation than the main-wear zone. Overall the AMC ceramic appeared more resistant to stripe-wear effects created by the micro-separation and impingement phenomena.

The humerus is a common site for skeletal metastases in the adult. Surgical stabilisation of such lesions is often necessary to relieve pain and restore function. These procedures are essentially palliative and should therefore provide effective relief from pain for the remainder of the patient’s life without the need for further surgical intervention.

We report a retrospective analysis of 35 patients (37 nails) with symptomatic metastases in the shaft of the humerus which were treated by locked, antegrade nailing. There were 27 true fractures (73.0%) and ten painful deposits (27.0%). Relief from pain was excellent in four (11.4%), good in 29 (82.9%) and fair in two (5.7%) on discharge. Function was improved in all but one patient. One case of palsy of the radial nerve was noted. The mean postoperative survival was 7.1 months (0.2 to 45.5) which emphasises the poor prognosis in this group of patients. There were no failures of fixation and no case in which further surgery was required.

Antegrade intramedullary nailing is an effective means of stabilising the humerus for the palliative treatment of metastases. It relieves pain and restores function to the upper limb with low attendant morbidity.

Introduction: Effective utilisation of blood products is fundamental. The introduction of Maximum Surgical Blood Ordering Schedules (MSBOS) for operations provides guidance for effective cross-matching. A retrospective analysis of blood ordering practices was undertaken to establish an evidence-based MSBOS for revision THR and TKR. The impact of the use of intraoperative cell-salvage devices was also assessed.

Methods: The patient database was searched for cases of revision THR and TKR undertaken over 58months. These records were then cross-referenced with the transfusion database. The cross-match to transfusion ratios (CTR) and transfusion indexes (TI) were calculated using this data.

The gold standard for the CTR is 2:1 or less. Procedures with ratios greater than 3:1 should substitute for a ‘group and save’. The TI establishes the likelihood of blood being transfused for a certain procedure, i.e., the number of units transfused divided by the number of patients having the procedure. If the TI is less than 0.5, then cross-matching blood is considered unnecessary.

Results: For revisions of non-infected THR (n=269), the CTR=2.24 and TI=1.67. In infected cases (n=69), CTR=2.16 and TI=1.68.

In revisions of non-infected TKR (n=95), the CTR=4.33 and TI=0.48. In infected cases (n=54) the CTR=2.16 and TI=1.35.

There was considerable change in the practice of ordering cross-matched blood following the introduction of intraoperative cell-salvage devices (Revision THR: CTR=1.93, TI=0.84; Revision TKR: CTR=1.20, TI=0.16)

Discussion: The analysis confirmed that more blood was requested than was actually required. Overall the results suggest that cross-matching is still necessary for both the non-infected and infected revision THR but the number of units requested could be reduced to 2units. In revision TKR, transfusions were more likely in infected cases and, a ‘group & save’ may be sufficient for non-infected cases.

The introduction of this MSBOS in conjunction with intraoperative cell-salvage, could promote blood conservation and financial savings.

The role of CAOS systems is now well established in several areas of orthopaedic surgery. The increasing use of these systems, particularly in knee arthroplasty, has been supported by clinical trials that demonstrate a more accurate final position of implanted devices compared with conventional instrumentation. CAOS technology is constantly evolving along with its expanding list of potential indications. This requires the adaptation of both software and hardware components. It is therefore essential that potential users have confidence in the accuracy of these systems. The aim of this project was to design and manufacture a standardised measurement object (phantom) to independently evaluate CAOS system performance.

The American Society for Testing and Materials (ASTM) International along with CAOS International recently drafted a standard for measuring technical accuracy of navigation systems. This proposed standard was obtained and its recommendations used to design a phantom model. This consisted of a 150×150×20mm base plate and two additional levels including a single 30° slope. This created a 3D surface on which points could be placed. Co-ordinates for 21 points were given to establish the x, y and z axes of a Cartesian system and then to have points at a variety of known locations in this 3D space. The final model was machined from a billet of marine grade aluminium alloy 6082-T6 (chosen for its dimensional stability) using a vertical computer numerical controlled (CNC) milling machine with the co-ordinate points drilled with a Ø0.8mm 60° BSO centre drill to a depth of 1.2mm. The drill holes, with chamfers of Ø1.0mm, were designed to accommodate a ball-nosed pointer tip of a known diameter. A Perspex base unit with three different sites of rigid tracker attachment was made to hold the phantom and provide its reference frame. This avoided the need to directly modify the phantom itself.

The final design has been used to measure the positional accuracy of a novel portable navigation system and demonstrate that it is not yet suitable for clinical evaluation due to errors of 1 – 6 mm in point location. It has also allowed independent technical validation of current pre-existing navigation systems.

Osteoarthrosis (OA) is often considered to be due to “wear and tear”, aggravated by obesity. However, if developmental dysplasia of the hip (DDH) is treated incorrectly, osteoarthrosis can also occur at a very young age. We obtained cartilage from the femoral head a 23 year-old female after arthroplasty for DDH; from a 14 year-old male, resected for paralytic dislocation, and from OA and control patients. This provided a unique opportunity to compare the cellular and epigenetic features of OA in older patients with those in a young control as well as a DDH patient. We have recently defined the cellular and epigenetic features of idiopathic OA, in particular the association between induction of proteases and loss of DNA methylation in the respective promoter regions (Arthritis Rheum2005; 52: 3110–3124). We had shown that these proteases were silenced in normal articular chondrocytes, but “unsilenced” in OA chondrocytes. The present study determined whether the phenotypic changes of idiopathic OA also take place in juvenile OA and whether loss of DNA demethylation is also associated with the abnormal expression of proteases in juvenile OA. Paraffin sections were immunostained with antibodies to MMP-3, -9, and ADAMTS-4. DNA was extracted from freezer milled cartilage. The methylation status of specific CpG sites (at which methylation occurs) was established using methylation-sensitive restriction enzymes followed by PCR. From the 23 year old female, we only obtained a 1cm thick transverse slice of femur, taken near the femoral neck. However, this contained sufficient reasonably thick cartilage in the perimeter for histology and DNA extraction.

The cartilage of the 14-year old showed high cellularity and absence of immunostaining for all proteases investigated. Apart from the higher cellularity, this was similar to the ‘control’ cartilage obtained from patients with a fracture of the femoral neck. We had previously shown that, as OA progresses, more chondrocytes become immunopositive for the degradative enzymes and these cells divide so that in the typical clones of OA all cells synthesize the proteases. The cartilage from the 23-year old DDH patient showed extensive loss of proteoglycans from the superficial zone and fibrous repair tissue covered some areas. Nearly all chondrocytes produced the proteases and clones had formed, as in idiopathic OA. Since these sample were from the base of the femoral neck, where in idiopathic OA good cartilage often remains even in severe OA, the disease process must have reached an early end-stage in this young patient. The findings indicate that severe OA, as defined by the presence of clones that produce degradative enzymes, can develop very quickly. Interestingly, the expression and synthesis of degradative enzymes by OA chondrocytes was the same in juvenile and old-age OA. and their abnormal expression was associated with “unsilencing” via DNA demethylation in both juvenile and old-age OA. The results thus suggest that age per se is not a major determinant of OA progression.

Aim: To compare the rate of relapse of Ponseti treatment method with a historical cohort who underwent conventional surgery.

Method and Results: From June 2002 to December 2004, 70 patients presented with 107 clubfeet and started the Ponseti treatment method. 15 feet in 9 patients were excluded due to teratologic deformity. 50 patients with 75 clubfeet were studied (41 boys and 9 girls). There was at least a two-year follow up period, or failure of the Ponseti method within this time frame. Data was compiled from clinic assessment forms and patient notes. All cases resulting in recasting or further surgical procedures were regarded as failure of conservative treatment. This was compared to published data from the same centre, regarding relapse for the two-stage surgical method. From 1988 to 1995, 86 patients presented with 120 clubfeet and had surgical treatment. 68 patients with 91 clubfeet (48 boys 20 girls) had the two-stage surgical procedure and were followed up at a mean age of 5.7 years (2.2 to 9.6). The mean age for surgery was 8.9 months.

Relapse rate of both treatment methods was compared for all feet in all Dimeglio grades. Relapse rates for Ponseti and surgery respectively were: grade 2, 18.2% vs 0%; grade 3, 36.2% vs 20.4%; grade 4, 35.3% vs 65.4%. The differences were not statistically significant

Conclusions: The Ponseti method is as valid as the two-stage surgical method for the treatment of clubfoot. Functional outcomes of the two treatment methods need to be compared.

Introduction: A successful total knee replacement (TKR) relies upon effective soft tissue management. Historically, soft tissue balancing has been difficult to assess and quantify intraoperatively. Computer navigation permits us to accurately assess kinematics during surgery. In a previous study we performed a series of varus and valgus stress measurements in extension to devise an algorithm for soft tissue management. In this study we evaluate the effectiveness of this algorithm.

Methods: This prospective study used the Orthopilot® CT-free navigation system during TKR for 57 patients with end-stage arthritis. We collected intraoperative kinematic data for 42 varus knees. Pre- and post-operatively, a varus and valgus stress was applied at maximum extension, recording the mechanical femorotibial (MFT) angle. There were no patellar resurfacings. The following medial releases were performed based upon the kinematics and the algorithm below:

No release–MFT angle not less than −12° with varus stress, greater than 2° with valgus stress, and/or if extension deficit was not greater than 5°.

Results: Pre-operatively, the mean MFT angle was −9.6°varus (−3° to −22°) with varus stress and −0.8°varus (4° to −11°) with valgus stress. Post-operatively, the mean MFT angle was −3.5° varus (0° to −5°) with varus stress, and 2.1° valgus (4° to −1°) with valgus stress.

Using regressional analysis, there was a strong linear correlation between both varus (r=0.871, p< 0.0001) and valgus (r=0.894, p< 0.0001) stresses and the MFT angle.

Post-operatively, the mean MFT angle was maintained within a narrow range (0° to −5° with varus stress, 4° to −1° with valgus stress), with no outliers. There were no extension deficits.

Conclusions: Using computer navigation a quantifiable soft tissue management system was introduced. We evaluated this algorithm, and obtained reproducible results within a narrow range and no outliers. This algorithm may provide an effective soft tissue management plan in TKR.

Aims: To investigate the effect of age and occupation on the outcome of carpal tunnel decompression.

Patients and Methods: A total of 271 patients undergoing primary carpal tunnel decompression by a single surgeon were studied. Patients with inflammatory joint disease, thyroid disease and diabetes mellitus were excluded. Outcome was assessed using the Levine-Katz carpal tunnel questionnaire at two weeks preoperatively and six months postoperatively. Cases were divided into six age groups (less than 40 years of age, 40 to 49, 50 to 59, 60 to 69, 70 to 79, and over 80 years of age) and 12 occupational groups according to the International Standard Classification of Occupations (ISCO-88). Statistical analysis was performed using one-way analysis of variance (ANOVA) and post ad-hoc analyses.

Results: Overall there was an improvement in total Levine scores in 269 (99.3%) patients (mean change 33.1, 95%CI: 31.5 to 34.7). This change was greatest in those over 80 years of age (mean 35.8, 95%CI: 29.0 to 42.6) and in those who were service or sales workers (mean 39.6, 95%CI: 34.9 to 44.2), and least in the 70–79 age group (mean 30.7, 95%CI 25.7 to 35.8) and craft and trade workers (mean 29.8, 95%CI: 21.8 to 37.9). Patients reported a greater improvement in symptoms (mean score change 21.4, 95%CI: 20.2 to 22.2), than function (mean 12, 95%CI: 11.1 to 12.7). We found no significant difference in the total, functional or symptomatic Levine score changes between the six age groups (p=0.05) and the 12 occupation groups (p=0.05) following carpal tunnel decompression.

Conclusion: Almost all patients improved after carpal tunnel decompression. However, we found no influence of age and occupation on the outcome of carpal tunnel decompression in our series of patients.

Introduction: Computer navigation systems allow real time evaluation of knee behaviour intraoperatively. Measurements made by navigation reflect soft tissue balance throughout surgery. We studied three different populations of patients undergoing total knee replacement (TKR) with a CT-free navigation system where the goal was to achieve normal alignment. We compared the initial pathological kinematics in each group with the resultant kinematics after correction.

Method: The Orthopilot® was used during TKR for three groups of patients A (n=71), B(n=60) and C(n=43) all with endstage osteoarthritis. Patients in groups A and B had TKR performed by surgeon 1, and group C by surgeon 2.

Results: Pre-operatively, the mean mechanical femoral axis and the mean mechanical femoro-tibial (MFT) angle were calculated. The mean mechanical femoral axis for group A was −0.5° varus (−6° to 9°), group B was −0.68° varus(−6° to 6°), and for group C was 2.67° valgus (−12° to 10°). P< 0.0001, using Kruskal-Wallis test. Pre-operatively, the mean MFT angle for group A was −3.75° varus(−15° to 17°), group B was −2.98° varus(−17° to 13°), and for group C was 0.16° valgus(−17° to 25°). P=0.003 using Kruskal-Wallis test. These results show that the initial preoperative kinematics are different for the three different populations.

Post-operatively we measured the mean MFT angle in groups A, B and C. In group A, the mean MFT angle was −0.38° varus (−4° to 2°), group B was −0.41° varus(−5° to 2°), and group C was −0.02° varus(−3° to 5°). P=0.7 using the Kruskal-Wallis test. These results show that the post-operative kinematics are similar between the three different populations.

Discussion: Populations A and B preoperatively exhibited a mean varus MFT angle (−0.5° and −0.68° respectively), compared with a mean valgus MFT angle for group C(2.67°), which were statistically significantly different. Although different surgeons operated on the 3 groups (surgeon 1 operated on groups A and B, and surgeon 2 operated on group C), post-operative kinematics were within a narrow range (−0.02° to −0.41°) and not statistically different (p=0.7).

Conclusion: The Orthopilot® results showed that these populations had different initial pathological kinematics. Despite this, and using different operators we obtained similar post-op results within a narrow range. Computer navigation produces reliable, reproducible results independent of population or operator variables.

Introduction: Accurate soft tissue balancing is an essential part of total knee replacement (TKR), but has been difficult to quantify using traditional instrumentation methods. Computer navigation systems allow us to accurately assess intra-operative kinematics, which are affected by soft tissue management. The aims of this study were to evaluate the role of varus and valgus stress measurements and subsequently devise an algorithm for soft tissue management during TKR.

Methods: We used the Orthopilot® CT-free navigation system during TKR for patients with primary end-stage arthritis. This was a prospective study with 71 patients collecting intra-operative kinematic data. 57 knees were varus, 13 valgus, and 1 well aligned.

Pre- and post-operatively, the surgeon applied a varus and valgus stress at maximum extension, recording the mechanical femorotibial (MFT) angle. There were no patellar resurfacings. We compared the kinematics of each varus knee. Based upon the kinematics and the surgeon’s experience the following medial releases were performed as usual and divided into three categories:

No release (limited medial approach).

Results: Pre-operatively, the mean MFT angle was −9.6° (−3° to −22°) with varus stress and −0.8° (4° to −11°) with valgus stress. Post-operatively, the mean MFT angle was −3.7° (−1° to −7°) with varus stress, and 1.1° (4° to −3°) with valgus stress. Using regressional analysis, there was a strong linear correlation between both varus (r=0.742, p< 0.0001) and valgus (r=0.771, p< 0.0001) stresses and the MFT angle.

With the following medial releases, these kinematics were found:

No release – MFT angle not less than −12° with varus stress, greater than 2° with valgus stress, and/or if extension deficit was not greater than 5°.

The results show that post-operatively, the mean MFT angle is maintained within a narrow range (−1° to −7° with varus stress, 4° to −3° with valgus stress). 5/57(9%) patients had a mean MFT angle of 6.4°(0° to 7°) with valgus stress, and were considered to have been over-corrected. There were no extension deficits.

Conclusions: Navigation allows us to quantify soft tissue balancing based upon the initial kinematics with varus and valgus stress testing. From these measurements, an algorithm was developed, which showed that an appropriate release was made in 52/57 (91%) patients, but this may require some adjustment to reduce the number of outlying results.

The purpose of the study was to evaluate if 2 week Levine score can provide an adequately responsive outcome measure in Carpal Tunnel Decompression by comparing it with 6 month score.

The treatment outcome of 300 patients with Carpal Tunnel Decompression was determined by using Levine score at 2 weeks and 6 months after surgery. The mean age of patients was 55 years and 6 months, 71.3% (214) were female with 55.33% (167) operations being performed on right hand. All patients were scored through Levine questionnaire pre operatively and at 2 weeks and 6 months from date of surgery. The correlation between the scores was evaluated.

Although statistical significance was found between the pre operative score and the scores at both 2 weeks and 6 months, no statistical difference was found between the scores at 2 weeks and 6 months post surgery. Multiple regression analysis with the 2 week–6 month score difference as the dependable variable shows a predictable outcome at 2 weeks.

We conclude that the Levine score at 2 weeks is a reliable, responsive and practical instrument for outcome measure in Carpal Tunnel Surgery. It coincides with suture removal and provides a convenient and predictive assessment of the medium term results in a high percentage of treated patients.

The accuracy of measurement in computer-assisted total knee arthroplasty is dependent on the quality of data acquisition at the start of the procedure; errors in landmark identification could lead to misalignment and therefore poorer longterm outcomes.

Some navigation systems require the surgeon to explicitly identify the femoral epicondyles in order to calculate the trans-epicondylar axis, whereas other systems are able to interpolate the epicondylar location based on a number of points acquired from the distal femoral surface. Significant inter-observer variability in landmark identification has been previously reported in dry bone studies. The purpose of this study was to test the accuracy of identification of the epicondyles during a simulated total knee replacement on a fresh cadaveric specimen.

An unfixed fresh cadaveric left lower limb was used to perform a navigated total knee replacement using the Orthopilot® (B|Braun-Aesculap, Tuttlingen, Germany) image-free navigation system.

Sixteen surgeons attending an advanced navigation training course were invited to take part. A single consultant surgeon performed initial dissection and pin placement, up to the point of landmark acquisition. Each subject was then asked to use a pointer tool to identify the medial and lateral epicondyles, as they would in an operative situation. Data were recorded by the Orthopilot® system, and exported as a 3D array for further analysis.

Initial visualisation with a 3D scatter plot showed that points were evenly distributed within a circular pattern around each epicondyle. The length of a vector between each point on each epicondyle was calculated in turn. The maximum distances between points were 15.6mm for the medial epicondyle, and 19.9mm for the lateral epicondyle.

We then calculated the length and angulation of the trans-epicondylar axis (TEA) for each observer, equivalent to the vector between each pair of points (medial and lateral epicondyle). An average TEA was calculated, and the range and standard deviation of angulation were determined. In the x axis the range was 16.3° (–8.3° to 7.9°, SD 5.1°), in the y axis the range was 18.7° (–8.7° to 10°, SD 5.2°) and in the z axis the range was 20.5° (–10.1° to 10.4°, SD 6.5°). Range of recorded TEA length was 64.5 to 74.9mm (mean 70.6mm, SD 3.3mm).

We conclude that in this simulated operative scenario, surgeons exhibited considerable variability when locating the epicondyles. Range of angulation of the TEA exceeded 16° (SD > 5.1°) in all 3 planes. We cannot recommend the use of a trans-epicondylar axis determined from 2 single points, as a reliable landmark in navigated total knee replacement.

Total knee replacement (TKR) has become the standard procedure in management of degenerative joint disease with its success depending mainly on two factors: three dimensional alignment and soft tissue balancing. The aim of this work was to develop and validate an algorithm to indicate appropriate medial soft tissue release during TKR for varus knees using initial kinematics quantified via navigation techniques.

Kinematic data was collected intra-operatively for 46 patients with primary end-stage osteoarthritis undergoing TKR surgery using a CT-free navigation system. All patients had preoperative varus knees and medial release was made using the surgeon’s experience. From this data an algorithm was developed to define the medial release based on the pre-operative mechanical femoral-tibial angle with valgus stress;

No release (tibial cut only) when valgus stress > −2/3°. Moderate release (medial aspect of tibia +/− semimembranosous tendon) when valgus stress > −5° and < −2°. Extensive release (proximal) when valgus stress < −5°. If there was a fixed flexion deformity > 5° then a posterior release was performed.

This algorithm was validated on a further set of 35 patients where it was used to determine the medial release based only on the kinematic data. The post-operative varus and valgus stress angles for the two groups were compared and showed good outcomes in terms of distribution and outliers.

The results showed that the algorithm was a suitable tool to indicate the type of release required based on intra-operatively measured pre-implant valgus stress and extension deficit angles. It reduced the percentage of releases made and the results were more appropriate than the decisions made by an experienced surgeon.

Introduction: A departmental audit meeting identified a problem with mis-seating of the ceramic liner for the Trident Acetabular System.

Methods: We reviewed the initial postoperative radiographs of all patients who had undergone primary THR using the Trident Acetabulum. Independent review was performed by 3 experienced hip surgeons.

Results: One hundred and seventeen hips (113 patients) were identified. Nineteen had incomplete seating of the liner as judged by plain anteroposterior and lateral radiographs, (prevalence 16.3%). Pre-operative diagnosis was not a risk factor for mis-seating of the liner. One case of complete liner dissociation necessitating revision was identified; another mis-seated liner was also revised in the early postoperative period and two that were initially incompletely seated were noted on follow up radiograph to have spontaneously re-seated. Out of 15 surgeons who had used this system, 10 had at least one case where the liner was incompletely seated.

Discussion: There may be technical issues with regard to implanting this prosthesis of which surgeons should be aware. The Trident Ceramic Acetabular System has a unique design that features a titanium sleeve encapsulating the ceramic that is elevated at the periphery. This sleeve may prevent complete circumferential inspection of the liner when attempting to assess intra-operative seating. We also believe that the Trident shell can deform upon implantation, preventing complete seating of the liner. This theory is supported by the observation that two originally mis-seated liners were noted to have spontaneously re-seated on subsequent radiographs. This phenomenon can be explained by the viscoelasticity of bone and elastic recoil of the shell. The cases of persistent liner mis-seating may be explained if the hoop stresses upon implantation are large enough for plastic deformation to occur. Potential problems include metallosis, implant loosening and fatigue fracture of either the shell or liner as a result of fretting.

Introduction: Intra-articular injection of steroid to the hip prior to joint arthroplasty has been suggested in some studies to carry a risk of infection up to 30% and subsequent revision surgery required in up to 12.5%.

Methods: We undertook a review of all intra-articular hip injections performed at the Queen Alexandra Hospital, Portsmouth and the Royal Haslar Hospital, Ports-mouth between January 2000 and April 2006. Hospital notes including operation notes, anaesthetic preoperative assessments and clinic letters were used to collect the following data. Name, age, sex, and premorbid conditions in particular diabetes, medication, date of injection, substance injected, date of arthroplasty and post operative complications.

Results: 370 intra-articular hip injections were performed of which 55 subsequently had total hip arthroplasty. 1 required washout post operatively but components remained and to date have not required revision. 1 required excision arthroplasty to eradicate deep infection and is still awaiting revision arthroplasty. This shows an infection risk of 3.6% and revision rate of 1.8%.

Discussion: Our review does not show a high rate of infection following intra-articular injection. We conclude that the therapeutic and diagnostic benefits of intra-articular injection may be considered prior to total joint arthroplasty without the increased risk of subsequent infection

Performing Total Knee Replacement (TKR) surgery using computer assisted navigation systems results in more reproducibly accurate component alignment. Navigation allows real time evaluation of passive knee behaviour throughout flexion. These kinematic measurements reflect tibial rotation about the femoral condyles, patellar tracking and soft tissue balance throughout surgery. In this study, we aim to study dynamic knee function in navigated and standard instrumentation TKR patients performing a range of everyday activities using gait analysis.

A prospective randomised controlled trial evaluated the functional outcome using gait analysis with 20 patients in each of three groups – Standard, Navigated and Control. The same implant (Scorpio) and navigation system (Strykervision) was used for each patient. The control group were subjects with no history of knee pathology or gait abnormality. Using an 8-camera Vicon motion analysis system set at 120Hz (real-time motion), we assessed the following functional activies: walking, rising from/sitting in chair, ascending/descending stairs. One functional outcome measure we have analysed so far is the maximum flexion angle.

The maximum flexion angle was recorded for each activity in standard, navigated and control groups respectively. ANOVA was performed, with significance set at p< 0.05. Maximum flexion angle during gait was 65.6°, 72.6° (p=0.009) and 73.5° (p=0.74), chair rising/sitting was 82.5°, 92.8° (p=0.01), and 93.5° (p=0.64), stairs ascent/descent was 81.8°, 99° (p< 0.0001), and 113.4° (p< 0.0001).

In terms of dynamic functional outcome, we found that the average maximum flexion angle for the navigated group was greater than for the standard group; moreover, this was similar to the maximum flexion angle for the control group when performing a variety of normal daily activities.

Background & Objectives: Osteoporosis is one of the most prevalent bone diseases worldwide with fractures its major clinical consequence. Studies on the effect of osteoporosis on fracture repair are contradictory and although it might be expected for fracture repair to be delayed in osteoporotic individuals, a definitive answer still eludes us. Subsequently, the aim of this study was to attempt to clarify any such effect.

Methods: Osteoporosis was induced in 53 female Sprague-Dawley rats by ovariectomy (OVX) at 3 months. A femoral fracture was produced in these animals 12 weeks later {OVX+Fracture group (OVX+F)}. A control group received the fracture only group (F) at 6 months. The fracture consisted of an open osteotomy held with a unilateral external fixator. Outcome measures include histology, motion detector analysis, pQCT, biomechanical strength testing (BST) and digital radiography. Digital radiographs were taken at time of OVX, fracture (confirming satisfactory reduction) and sacrifice from which relative bone density (BMD) measurements were calculated.

Results: OVX+F animals were significantly heavier than F animals at fracture and sacrifice (p< 0.001 for both) and moved significantly less in days 1-4 (p=0.032) and 5-9 (p=0.020) post-fracture. Relative BMD measured in distal femur at fracture and sacrifice was significantly greater in F group (p< 0.001 for both). Furthermore, there was a significant decrease in relative BMD from fracture to sacrifice in OVX+F group (p< 0.001). pQCT showed a significantly greater total BMD {contralateral (p=0.021) and fractured femora (p< 0.001)} and trabecular BMD (p< 0.001 both limbs) in the distal femur of the F group. Histologically, no statistical differences were found, however, the F group generally displayed the most advanced repair. In the contralateral limb, the F group had significantly greater load to failure at 6 (p=0.026) and 8 (p=0.042) weeks and was significantly stiffer at 8 weeks (p=0.050). In the fractured leg, stiffness was significantly greater in the F group at 8 weeks (p=0.001).

Conclusion: OVX was linked to increased body weight, decreased motion, decreased BMD (with particular loss in trabecular BMD), and reduced mechanical properties. OVX did not have a significant effect on fracture healing and although there was no reduction in BMD at the fracture site, histology and reduced stiffness suggest it was delayed.

We prospectively studied 15 proximal tibial and 30 distal femoral fractures treated with the Less Invasive Stabilisation System for periarticular fractures about the knee.

Of these 45 fractures, one patient returned to Russia and was thus lost to follow up. The mean age of the remaining patients was 64.4 years (range 15–94 years). There were 26 females and 13 males. All fractures were classified according to the AO classification.

We found the use of temporary external fixation and mobile radiolucent wedge leg supports very helpful during surgery for these cases. We developed an increasingly aggressive postoperative mobilisation regime with increased experience of using this fixation technique.

Functional assessment was performed using the Schatzker and Lambert scores. The average time to union was 14.78 weeks (range 10– 28 weeks). 43 fractures have united with one fracture showing signs of delayed union. There were two implant failures, two deep vein thrombosis and two compartment syndromes. Five patients died of unrelated causes and without problems relating to their fracture.

We conclude that the Less Invasive Stabilisation System is a satisfactory method of treating these complex and difficult fractures about the knee with a high rate of union and good functional outcome.

Introduction: It is said that God gave us paired bilateral anatomical structures so that the trauma surgeon can compare the injured side with its uninjured counterpart. The axial rotational alignment of fingers, when disrupted by injury, may lead to scissoring. During examination, comparison is made between the rotational alignment of injured and uninjured fingers. This assumes that the rotational alignment of the fingers is symmetrical. A study was performed to ascertain normal rotational alignment, and establish whether this assumption is valid.

Materials and Methods: Standardised digital images were taken with fingers in extension. These were analysed using the angle-measuring tool on Adobe Photoshop software. The rotational angle used was that between a line joining the radial and ulnar borders of the nail plate, and the horizontal.

Results: Mean angles of rotation were 13° for the index finger, 10° for the middle, 5° for the ring and 12° for the little. Differences in the angle for ring and little fingers between the sides were not significant; these fingers are symmetrical. Index and middle fingers demonstrated statistically significant asymmetry of 2.6° (SD +/− 4.2°).

Discussion: Previous work has sought to quantify rotational alignment in cadavers or using wire markers and fluoroscopy. A new method, using digital photography and image analysis is described. We determined mean angles, showing symmetry of the ring and little but asymmetry of index and middle. Previous work has suggested that up to 10° of rotation can be tolerated. With only 2.6° of difference, clinical comparison of sides remains appropriate.

Introduction: Despite clinical history, examination and plain radiography it is occasionally difficult to locate the origin of hip pain. This is particularly relevant where the management will be a total hip arthroplasty. Local anaesthetic arthrogram of the hip may provide a simple, safe and reliable test to determine if the hip is the source of the patient’s symptoms. The aim of this study was to establish the use of this investigation in the management of hip pain.

Methods: All local anaesthetic hip arthrograms were reviewed from 1999 to 2005. All patients had completed a pain questionnaire following the arthrogram. Patients were classified into 3 groups; 1) Mild osteoarthritic changes on plain radiographs with possible referred pathology; 2) Minimal radiological changes but no obvious other pathology to refer pain; 3) Previous hip arthroplasty with unexplained pain. Those who subsequently had a primary or revision hip arthroplasty were assessed post-operatively by means of the Oxford hip score.

Results: Fifty-seven patients in total underwent a local anaesthetic hip arthrogram. From all the groups 34 patients obtained pain relief and 24 proceeded to primary or revision hip arthroplasty. Twenty three (96%) had a satisfactory post-operative outcome at an average follow-up of 2 years (average Oxford score 28). The remaining 10 patients with positive arthrograms are still waiting for surgery. All negative arthrogram patients were successfully discharged.

Discussion: A positive response to local anaesthetic hip arthrogram predicts a successful response to surgery. This permits accurate information of the results of hip surgery to be given to patients and aids in a management plan for a group of patients that can be otherwise challenging.

Background & Objectives: Statins have been shown to stimulate bone formation in vivo and in vitro in rodent models1 generating interest in the possibility that they may be useful therapeutic agents for osteoporosis. The major clinical consequence of osteoporosis are fractures that occur and although there is no firm evidence, there is a perceived associated delay in fracture repair. We examined the influence of atorvastatin on fracture repair in an ovariectomised rat fracture model.

Methods: 126 Sprague-Dawley rats had an ovariectomy (OVX) at three months and a femoral fracture (F) at six months. The fracture consisted of an open osteotomy held with an external fixator. All animals were randomly assigned into groups 1. OVX+F and early atorvastatin; 2. OVX+F and late atorvastatin; 3. OVX+F. Atorvas-tatin (5mg/kg) was given daily by oral gavage for three months in-group 1 between OVX and fracture and from time of fracture to sacrifice in-group 2. Outcome measures were histology, peripheral quantitative computed tomography (pQCT), biomechanical strength testing (BST) and digital radiography. Digital radiographs were taken at time of OVX, fracture (confirming satisfactory reduction) and sacrifice from which relative bone density (BMD) measurements were calculated.

Results: Non-statin treated animals moved significantly more in 4 days post-fracture (p=0.015), had signifi-cantly more relative (p=0.037) and total BMD (distal femur) than statin treated (p=0.040, early and p=0.036, late treatment). Total BMD at the fracture site was also significantly greater in the OVX+F than the late statin group (p=0.047) while in the adjacent site of the con-tralateral limb, the early statin group had significantly more (p=0.018) than the late statin group. However no differences were found between the early statin and OVX+F groups. Histologically, the rate of repair increased significantly in early statin (p=0.013) and OVX+F (p=0.011) groups. BST data showed no signifi-cant difference in stiffness at six or eight weeks.

Conclusion: Fractures healed in all three groups. Statins did not prevent OVX induced bone loss. Initial evidence suggests that early statin treatment may have a positive effect on early fracture, as shown by x-ray analysis and histology, however this effect was lost by week 8. Overall the evidence suggests that atorvastatin may have impaired fracture repair, particularly with late administration (relative BMD and pQCT results).

Elevated serum cobalt and chromium ion levels associated with carcinogenesis and chromosomal damage in animals have raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum cobalt and chromium ion levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

All patients having THR at our institution were prospectively registered on a computerised database. From our database, we identified 108 patients with Ultima (Johnson and Johnson, Leeds) MOM THR with 28 mm bearing made of cobalt-chromium alloy. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery at blood sampling, activity level and body mass. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry.

The serum cobalt ion level after unilateral MOM THR was 4.4 times normal (median 22 nmol/L, range 15 to 37 nmol/L) compared to 8.4 times normal (median 42 nmol/L, range 19 to 221 nmol/L) for bilateral MOM THR (p=0.001). The serum chromium ion level after unilateral MOM THR was 3.8 times normal (median 19 nmol/L, range 2 to 35 nmol/L) compared to 10.4 times normal (median 52 nmol/L, range 19 to 287 nmol/ L) for bilateral MOM THR (p=0.04).

This study has shown that the serum cobalt and chromium ion levels in patients with bilateral MOM THR are significantly higher than those in patients with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this finding may be of relevance for the potential development of long-term side effects.

The majority of diaphyseal forearm fractures in children are treated by closed reduction and plaster immobilisation. There is a small subset of patients where operative treatment is indicated. Recent reports indicate that elastic intramedullary nailing (EIN) is gaining popularity over plate fixation. We report the results of EIN for diaphyseal fractures of the forearm in 44 children aged between 5 and 15 years during a three-year period. The indications were instability (26), redisplacement (14), and open fractures (4). Closed reduction and nailing was carried out in 18 cases. A single bone had to be opened in 16 cases and in 10 cases both bones were opened for achieving reduction. Out of the 39 both bone forearm fractures, 35 patients had stabilisation of both radius and ulna and in 4 cases only a single bone was nailed (Radius 3, Ulna 1).

Union was achieved in all the 44 cases at an average time of 7 weeks with one delayed union. All patients regained full flexion and extension of the elbow and wrist. Pronation was restricted by an average of 20° in 30% patients.

Complications were seen in 10 patients (20%). 4 patients had prominent metal work which required early removal. There was refracture in one case, which was treated by nail removal and re-fixation. Two patients developed post operative compartment syndrome requiring fasciotomy. EIN of the radius alone in a patient with fractures of both the bones of forearm, led to secondary displacement of the ulna. This resulted in ulnar malunion and a symptomatic distal radio-ulnar joint subluxation. This was successfully treated by ulnar osteotomy.

Compared to forearm plating EIN involves minimal scarring, easier removal and less risk of nerve damage. We therefore recommend EIN for the treatment of unstable middle and proximal third forearm fractures.

The experimental determination of residual stress fields on the surface of retrieved femoral heads represents a fundamental step in understanding their wear degradation behavior and the tribological mechanisms, which are operative on the femoral joint during its working life time. In this work, the surface of retrieved alumina and zirconia (Al2O3 and ZrO2) femoral heads were investigated by piezo-spectroscopic tecniques based both on photoluminescence and Raman effects. The high spatial resolution of the laser, impinging on the investigated surface (typically about 1 micron of lateral resolution), enabled us estimating patterns and magnitude of residual stress in extremely narrow zones, comparable with the grain size of the material.

Four retrieved ceramic femoral heads were analyzed. Two balls were made of alumina with a typical grain size of from 4 to 10 microns. Both alumina balls were retrieved after only few years from implantation, due to septic and aspetic loosening. The remaining two femoral heads were made of zirconia with a typical grain size of 1 micron. These latter balls were retrieved after 2 and 13 years, respectively (both for loosening problems). With a systematic collection of a large number of data on a microscopic level it was possible to assess the retrieved femoral heads in to to, thus extending the microscopic analysis to the entire joint.

In allumina balls retrieved after short time implantation, a macroscopic stress field was found, which arose from manufacturing, loading history, and the displacements acting on the femoral head during its lifetime. This stress field was completely overcome by a microscopic residual stress field due to local contacts (e.g., local shocks owing to microseparation, impinging and wear contacts). On the other hand, in zirconia femural heads, the major amount of surface deterioration after long-term exposure arose from tetragonal-to-monoclinic transformation in biological environment. These data allowed us to draw interesting considerations about the role of the material microstructure and the peculiar kinematic mechanisms involved with the use of femoral heads made of different materials.

Spectroscopic techniques, which are complementary to in vitro testing procedures and stress analyses based on finite-element methods, can be very useful for improving the design of the femoral head and for optimizing the microstructural characteristics of the ceramic materials employed. Based on this and previous fluorescence and Raman spectroscopic studies, we also propose that a systematic screening of the ceramic implants before implantation can strongly reduce the probability of failure of the implant.

Alumina ceramic has been used in total hip arthoplasty since the 70’s and, in the last 30 years, a considerable evolution has occurred in designing the microstructural features of this material, taking advantage of improved processing techniques, as the hot isostatic pressing. As a result, a high degree of densification (> 99.5) has been achieved in materials with a high degree of purity and, especially, with a fine grain size ( 2 microns). The surface stress field acting on a femoral head inoperation is not only due to working conditions, but also to unexpected factors, as local impacts on the surface as a result of partial dislocations, formation of debris, etc. These additional factors greatly contribute to activate degradation mechanisms which, unfortunately, may lead to failure of the implant.

In this study, five alumina femoral heads were investigated, which were retrieved from patients after different periods of time. Among those investigated femoral heads, two belonged to a first-generation type of alumina material with a relatively coarse grainsize (average value 8 microns) and were retrieved due to surface degradation after long periods of implantation (19 and 17 years, respectively); the remaining three implants analyzed were instead recently manufactured implants with a fine grain size; they were retrieved after relatively short periods because of different causes as, for example, cup or stem loosening.

Surface stress analysis using the luminescence of Cr3+impurity in alumina was performed on the retrieved femoral heads and a statistical comparison was attempted among implants with different microstructural characteristics. The investigation led to estimate average residual stress and statistical stress distributions as a function of the location on the femoral head.

The analysis was performed both on the very surface and in the sub-surface of the head, using the confocal and the through-focus configurations of the optical spectrometer, respectively. Different statistical distributions of residual stress were observed in alumina femoral heads with different grain sizes and models were created to understand their dependence on processing and surface loading.

Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long-term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/ L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Conclusion: Large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential effects of long-term exposure to elevated these metal ions is considered.

Prior studies have compared the bacterial load observed in laminar flow operating theatres (LFOTs) and standard operating theatres (STOTs) by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the poly-merase chain reaction (PCR). This study assessed the wound contamination rate during THRs and compared the results in STOT with that in LFOTs using PCR.

We recruited patients undergoing primary THR for osteoarthritis. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture. Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs, of which 3 were taken at the start of surgery and 9 at the end of the surgery, giving a 45% wound contamination rate (9 of 20). Two specimens (5%), both taken at the end of surgery, were positive on enriched culture. In LFOTs, bacterial DNA was identified by PCR on 8 of 40 specimens (20%), of which 2 were taken at the start of surgery and 6 at the end of surgery, giving a 30% wound contamination rate (6 of 20). No specimens were positive on enriched culture.

Wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data remind us the importance of aseptic surgical technique as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Zirconia (ZrO2) on Polyethylene (PE) has been used for18 years. However, a majority of clinical results expressed caution, citing surprisingly high wear and osteolysis. The most recent clinical study (Walters 2004) reports 20% higher wear with ZrO2/PE compared to CoCr/PE The PE wear may be the result of increased surface roughness of the ball, due to zirconia transformation from tetragonal to monoclinic phase. Impingement of metal cup backing on zirconia may result in high stress that drives the transformation. Our objective was to simulate the conditions most likely to transform the zirconia ball surface.

In phase one, the rim of a titanium cup was loaded against a zirconia ball with a static load range of 0.01kN to 10kN to simulate impingement-dislocation stress. The ball was cleaned with acid, ultrasonic cleaning, and then observed under SEM. Ball sections were made for XRD study. In phase two, the zirconia balls were pressure stressed in a hip simulator (static load range of 1kN to 4kN) for 600 cycles. Wear studies follow.

In phase one, the rim of a titanium cup was loaded against a zirconia ball with a static load range of 0.01kN to 10kN to simulate impingement-dislocation stress. The ball was cleaned with acid, ultrasonic cleaning, and then observed under SEM. Ball sections were made for XRD study. In phase two, the zirconia balls were pressure stressed in a hip simulator (static load range of 1kN to 4kN) for 600 cycles. Wear studies follow.

Pressure alone does not appear to transform zirconia in the articular surface. The phase two simulator studies include combinations of mechanical stress, environmental aging (autoclave) and lubricants (air, water, serum). The role of the heavy metal transfer may actually protect the zirconia surface from transformation phenomena.

Distal tibial fractures may be satisfactorily held in reduction by fine-wire external fixation techniques, avoiding the need for open reduction and internal fixation. However, as the use of external fixation is associated with pin-site infection, extra-articular placement of the wires is recommended. This study assesses the proximal extension of the capsule of the ankle joint in order to provide information on the safety of wire placement for distal tibia fractures.

We recruited 7 patients who were electively scheduled for an MRI ankle investigation with the suspicion of osteochondral defect and/or meniscoid lesion. Patients with a history of ankle fracture or ankle surgery were excluded from the study. Just prior to MRI, the ankle joint was injected with 5 to 15 ml of contrast solution (1 mM dimeglumine gadopentetate). Selected fat-saturated T1-weighted MRI scans with sagittal, coronal and axial views were obtained. The site and proximal extent of the capsular reflection with reference to the anterior joint line were measured.

All contrast-enhanced MRIs of the ankle joint space were well defined and unambiguous. Proximal capsular extensions above the plane of the anterior joint line were noted at the antero-medial and antero-lateral aspect of the joint (mean 8.9 mm, range 4.9 to 13.4 mm) and at the tibia-fibular recess (mean 18.7 mm, range 13.3 to 23.6 mm), areas that are frequently traversed by wire insertion.

Conclusion: This in vivo contrast-enhanced MRI ankle study demonstrates an appreciable capsular extension above the joint line of the ankle. The proximal capsular extensions at the antero-medial and antero-lateral aspect of the joint and at the tibio-fibular recess run the risk of being traversed during fine-wire placement for distal tibia fractures. Surgeons using these techniques should be aware of this anatomy.

The role of vacuum mixing on the reduction of porosity and on the clinical performance of cemented total hip replacements remains uncertain. We have used paired femoral constructs prepared with either hand-mixed or vacuum-mixed cement in a cadaver model which simulated intra-operative conditions during cementing of the femoral component. After the cement had cured, the distribution of its porosity was determined, as was the strength of the cement-stem and cement-bone interfaces.

The overall fraction of the pore area was similar for both hand-mixed and vacuum-mixed cement (hand 6%; vacuum 5.7%; paired t-test, p = 0.187). The linear pore fractions at the interfaces were also similar for the two techniques. The pore number-density was much higher for the hand-mixed cement (paired t-test, p = 0.0013). The strength of the cement-stem interface was greater with the hand-mixed cement (paired t-test, p = 0.0005), while the strength of the cement-bone interface was not affected by the conditions of mixing (paired t-test, p = 0.275). The reduction in porosity with vacuum mixing did not affect the porosity of the mantle, but the distribution of the porosity can be affected by the technique of mixing used.

We reviewed the initial post-operative radiographs of the Trident acetabulum and identified a problem with seating of the metal-backed ceramic liner. We identified 117 hips in 113 patients who had undergone primary total hip replacement using the Trident shell with a metal-backed alumina liner. Of these, 19 (16.4%) were noted to have incomplete seating of the liner, as judged by plain anteroposterior and lateral radiographs. One case of complete liner dissociation necessitating early revision was not included in the prevalence figures. One mis-seated liner was revised in the early post-operative period and two that were initially incompletely seated were found on follow-up radiographs to have become correctly seated. There may be technical issues with regard to the implanting of this prosthesis of which surgeons should be aware. However, there is the distinct possibility that the Trident shell deforms upon implantation, thereby preventing complete seating of the liner.

Idiopathic osteoarthritis (OA) is a complex, late-onset disease whose causes are still unknown. In spite of tremendous efforts, the search for the genes pre-disposing towards osteoarthritis has so far met with little success. We hypothesize that epigenetic changes play a major role in the pathology of OA. Epigenetics refers to stable, heritable, but potentially reversible modifications of gene expression that do not involve mutations in the DNA sequence, for example DNA methylation or histone modification. Epigenetic changes are gene and cell-type specific, may arise sporadically with increasing age or be provoked by environmental factors. To investigate whether epigenetic changes are significant factors in OA, we examined the DNA methylation status of the promoter regions of three genes that are expressed by OA, but not by normal, articular chondrocytes, namely MMP-3 (stromelysin-1), MMP-9 (gelatinase B) and MMP-13 (collagenase3). We hypothesized that these genes are silenced in normal chondrocytes by methylation of the cytosines of CpG dinucleotides in the respective promoter regions, but that abnormal expression is associated with a de-methylation, leading to eunsilencing f of gene expression. Cartilage was obtained from the femoral heads of 16 OA and 10 femoral neck fracture (#NOF) patients, which served as controls due to the inverse relationship between osteoporosis and OA. The cartilage was milled in a freezer mill with liquid nitrogen, DNA was extracted with a Qiagen kit, digested with methylation sensitive restriction enzymes, followed by PCR amplification. These enzymes will cut at their specific cleavage sites only if the CpGs is not methylated and thus allow us to determine methylation status of specific CpG sites.

Results. Less than 5% of the chondrocytes in superficial layer from #NOF cartilage expressed degradative enzymes, whereas all cloned chondrocytes from advanced-stage OA cartilage were immunopositive. The overall % of CpG demethylation in the promoters of control patients (whose chondrocytes did not express the enzymes) was 20.1%, whereas 48.6% of CpG sites were demethylated in degradative chondrocytes of OA patients (p< 0.001). For MMP-13, the increase in demethylation between control and OA was from 4 ^..20%; for MMP-9 from 47 ^..81% and for MMP-3 from 30 ^..57%. However, not all available CpG sites were equally demethylated. Some sites were uniformly methylated in both OA and controls, others were demethylated even in controls. However, there was at least one crucial site for each degradative enzyme, where the differences in the degree of methylation were greatest and statistically different. These sites were at −110 for MMP-13; −36 for MMP-9; −635 for MMP-3. There was no relation between the % demethylation and the patient fs age and no apparent difference between males and females.

Conclusions: We have demonstrated an association between abnormal gene expression of MMP-3, MMP-9 and MMP-13 and promoter DNA demethylation. This epigenetic dysregulation of genes appeared to be clonally inherited by daughter cells and may be typical for osteoarthritis and other complex, late-onset diseases.

In osteoarthritis (OA) there is a loss of matrix components, especially aggrecan, which is a major structural component important for the integrity and function of articular cartilage. The breakdown of aggrecan is mediated by enzymes from the ADAM-TS (a disintegrin and metalloproteinase with thrombospondin motifs) family and recent studies have suggested that, in humans, ADAM-TS4 (aggrecanase-1) plays a major role. Articular chondrocytes do not express ADAM-TS4 in contrast to clonal OA chondrocytes. Since in any somatic cell non-expressed genes are thought to be silenced by DNA methylation in the promoter region, the aims of the project were twofold:

to localize enzyme expression for ADAM-TS4 by immunocytochemistry and

Using immunocytochemistry, we confirmed that there is an increased expression of ADAM-TS4 in OA chondrocytes, which initially occurs in chondrocytes of the superficial zone. As the Mankin score increases, ADAM-TS4 positive chondrocytes were found in duplets, then quadruplets until, at Mankin score > 10, all the cells in a typical OA clone were immunopositive for ADAM-TS4, suggesting that abnormal enzyme expression was inherited by daughter cells. DNA was extracted from femoral head cartilage of 24 patients, who had undergone hip replacement surgery for either symptomatic OA or following a fracture of neck of femur (#NOF). The latter was used as control due to the inverse relationship between OA and osteoporosis. For OA samples, it was important to sample only those regions for which immunocytochemistry had shown the presence of ADAM-TS4 synthesizing cells, i.e. the superficial zones near the weight-bearing region. DNA methylation only occurs at cytosines of the sequence 5′...CG...3′, the so-called CpG sites. To determine methylation status of specific CpG sites, methylation sensitive restriction enzymes were used, which will only cut DNA in the absence of methylation. By designing PCR primers that bracketed these sites, presence or absence of PCR bands could distinguish between methylated and non-methylated CpGs respectively. The ADAM-TS4 promoter contains a total of 13 CpG sites. Using restriction enzyme/primers combinations, it was possible to analyze 7 of these sites for methylation status. In the control group, all 7 CpG sites were methylated, while there was an overall 49% decrease of methylation in the OA group (p=< 0.0001). Some of the CpG sites were more consistently demethylated then others, one site at −753bp upstream from the transcription start site, showed a 86% decrease in methylation in OA compared to the control group (p=0.0005), while at other sites the decrease in methylation ranged from 36–50%. Conclusions. This study confirmed by immunocytochemistry that ADAM-TS4 is produced by OA chondrocytes, contributing to the degradation of their matrix. This abnormal enzyme expression is associated with DNA methylation. If a causal relationship could be proven in the future, then DNA de-methylation might play an important role in the pathogenesis of osteoarthritis and future therapies might be directed at influencing the methylation status.

Introduction: There is some debate about the pros and cons of selective screening of DDH in neonates as opposed to general screening. General screening puts a lot of stress on the resources available, especially in the modern day NHS, but the advocates state that this minimises the cost incurred in treating a missed DDH (by selective screening) with surgery later on.

Aim: The aim of this retrospective study was to find out the effectiveness of the Southampton selective screening of babies with risk factors for DDH by finding out the number of patients presenting late with an established DDH.

Materials And Methods: 6116 babies out of 26,932 live births (22.7%) in Southampton were screened between 1998 and 2003. The details of the individual outcomes and the reasons for the late presentation were obtained from the patient notes and the records of the screening program which are maintained in the clinics and by the senior author.

Results: 248 new patients had Pavlik’s harness fitted for the treatment of DDH which presents a treatment rate of 0.92%. 8 patients (0.03%) presented late because they did not undergo ultrasound scanning as they did not have the risk factors as required by this selective program. 10 (0.036%) failed Pavlik’s and needed late surgery to have their DDH treated. The total operation rate was 0.066%.

Discussion: The late presentation of patients in this screening program is very low and comparable to the other papers from this department and from around the world. The cost implications of treating these 8 late presenting patients was found to be a lot cheaper than carrying out a general screening program which would mean, in this case 4 times more than the cost of the present screening program.

Clonal chondrocytes of osteoarthritic (OA) cartilage express an aberrant set of genes. We hypothesize that this aberrant gene expression may be due to clonally inherited epigenetic changes, defined as altered gene expression without changes in genetic sequence. The major epigenetic changes are due to altered DNA methylations in crucial parts of the promoter region. If the cytosines of CpG dinucleotides are methylated, the gene will be silenced, even if the right transcription factors are present. Similarly, de-methylations may activate previously silenced genes. Our aims were to provide ‘proof-of-concept’ data by examining the methylation status of genes in OA vs non-OA chondrocytes. Articular cartilage was obtained a) from the cartilage of fracture-neck-of-femur (#NOF) patients and b) from or around the eroded regions of OA samples. The former was full thickness cartilage, the latter was partially degraded cartilage, which contained mostly clonal chondrocytes as confirmed by histology. The cartilage samples were ground in a freezer mill (Glen Creston, UK) and DNA was extracted with a Qiagen DNeasy maxi kit. To assess DNA methylation status, the genomic DNA was treated overnight with methylation-sensitive restriction enzymes. Cleavage of selected sites was detected by PCR amplifications with primer pairs designed to bracket selected promoter regions. Loss of the PCR band after digestion with the enzymes indicated absence of methylations, whereas presence of the band indicated methylated cytosine. We selected MMP-9 as one of genes that is activated in OA. Transcription of mmp-9 is regulated by a 670 bp sequence at the 5′-end flanking region, which contains 6 CpGs and a further 21 CpGs within the 1.5 kb region further upstream. A PCR primer pair was designed to bracket a 350bp sequence upstream from the transcription start site of mmp-9, which contained four of the six potential methylation sites, cleaved by the methylation-sensitive enzymes AciI and HhaI. DNA from 9 OA patients, 5 #NOF patients and 1 rheumatoid arthritic (RA) patient were digested with HhaI or AciI and examined for the presence or absence of PCR bands. In all patients, digestion with HhaI abolished the PCR band, indicating that the HhaI site was never methylated in either #NOF or OA patients. However, a remarkable difference was found after digestion with AciI: in 8/9 OA patients, the PCR band was no longer detectable, while in 4/5 #NOF patients the PCR band was still present. This suggested that all three AciI cleavage sites were methylated in the majority of chondrocytes from #NOF patients, while at least one of the three AciI cleavage sites was unmethylated in OA patients. Interestingly, the PCR band was present in the RA patient, suggesting methylation of the AciI cleavage sites. The present study provides the first ‘proof-of-concept’ data that suggest epigenetic changes may play a role in the etiology of osteoarthritis. Clearly further work is required to establish the generality of the present findings and whether de-methylations are also found in the promoter regions of other genes that are aberrantly expressed in OA.

Introduction Surgeons request cross-match based on habit not evidence. The spinal unit requested 686 units of blood during 2002–2003 and transfused only 42 for elective lumbar spine surgery. This wastes money, time and blood.

Aim Optimise the transfusion requests in elective lumbar spinal surgery by creating evidence based guidelines.

Methods The data on elective operations performed on the lumbar spine during the period June 2002 to June 2003 was collected from the spinal unit database and cross-referenced with the records of blood transfusion. Cross-match: Transfusion ratios (C:T Ratio) and Transfusion Index (TI) for common procedures were calculated. Based on these results, a Maximum Surgical Blood Ordering Schedule (MSBOS) was created and prospectively audited for six months.

Conclusion Eighty units were cross-matched during the prospective audit. Therefore, in one year one hundred and sixty units would be requested. This represents a reduction of over five hundred units.

Introduction: Chondro-epiphyseal cartilage is generally resistant to vascular invasion. At the time of formation of the secondary ossification center in skeletal ‘long’ bones, the anti-angiogenic nature of cartilage is altered in favor of angiogenesis and vascular invasion takes place. We studied the control of this angiogenic ‘switch’ by experimentally investigating two factors which might influence vascular invasion. MMP 9 is a 92Kda gelatinase which degrades collagen types IV, V and X and gelatin (denatured collagen). It has been implicated in the control of endochondral ossification at the growth plate and has been shown to modulate endothelial cell morphogenesis. Basic Fibro-blast Growth Factor (b-FGF) is a cytokine with well established angiogenic capability and has also been implicated in the development of the growth plate. We investigated whether MMP-9 caused an effect on the development of the vasculature of the chondro-epiphysis of neo-natal rabbits and compared this to the effects of b-FGF.

Materials and Methods: The CAM Culture consists of placing a small tissue explant onto the the chorioallantoic membrane of 10 day-old chick embryos and continuing culture for a further 10 days. CAM derived vessels will invade the tissue, unless anti-angiogenic factors are present. Hence, CAM culture is used as an assay system for angiogenesis and factors that will influence it. We utilized the CAM culture model to investigate vascular in-growth into explants of femoral and humeral heads from 4 day old postnatal rabbits to test the influence of MMP-9 and b-FGF. A small nylon membrane, pre-soaked in a solution containing the factor, was placed on to a tangential cut across the perichondrium. The explant was then cultured on the CAM for 3–10 days.

Results: In control epiphyses, the in-growth of CAM derived blood vessels was rare and invasion of cartilage canals through the perichondrium seldom occurred, thus confirming the anti-angiogenic nature of epiphyseal cartilage. The initial presence of MMP 9 caused a tremendous increase in the de novo vascular invasion. MMP 9 treated epiphyses contained numerous large cartilage canals. In b-FGF treated epiphyses, a greater level of vascular in-growth was seen compared with controls, but this was not as marked as with MMP 9.

Our findings indicate that b-FGF and perhaps, more interestingly, MMP-9 are implicated in the activation of the angiogenic ‘switch’ at the chondroepiphysis leading to vascular invasion. The fact that MMP-9 can act as a stimulator to angiogenesis is a novel finding. The mechanism of action remains unclear although it is possible that it is involved in the deactivation of inhibitors of vasculogenesis or the activation of angiogenic factors, or both.

Study Design: Prospective cohort study

Summary of Background data: A definite link between Modic end plate changes and discogenic low back pain has yet to be established. However, current prospective data indicates that Modic changes strongly correlate with the pain provocation of lumbar discography and improved clinical outcome following instrumented posterolateral fusion. Consequently, there is recent heightened awareness using this radiological entity in the selection of patients for interbody fusion or total disc replacement.

Objective: To prospectively evaluate whether Modic changes can predict improved clinical outcome following antero-posterior lumbar interbody fusion using femoral ring allograft.

Methods: A cohort of chronic low back pain patients were investigated with MRI and lumbar discography. Twenty-six patients with disco-graphically-proven concordant pain reproduction were prospectively entered into the study. Clinical results were collected using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and Short Form 36 Health Questionnaire (SF-36) at the pre-operative and two-year follow up. The minimal clinically important difference (MCID) was taken as 10 points for ODI, 2 points for VPAS, and 7 points for the physical function and bodily pain subset of the SF-36 questionnaire.

Results: MRI scans evaluated for the level fused revealed 13 patients with no end-plate changes (Type 0), whilst 2 patients had Modic Type I and 11 had Modic Type II changes. MCID in ODI were achieved in Type 0, Type 1 and Type 2, but improvement in VAS only was achieved in the Type 0 and Type 1. For SF-36, the MCID of 7 points was reached in most domains for all types of Modic change. There was no statistical difference in clinical outcome between those patients with Modic Type 0 and those with Modic type I or II.

Conclusion: This prospective study shows that Modic changes do not predict improved clinical outcome following antero-posterior interbody fusion using the femoral ring allograft.

Introduction: In the 1970’s, ‘viscosupplementation’ with hyaluronan was proposed as a potential treatment for OA with the idea that it would improve joint lubrication. However, despite studies showing its ability to reduce pain, the fact that the resident time within a joint (48 hours) is much less than its clinical effect (several months) along with pharmacological effects on chondroctyes and synoviocytes has confirmed that injected hyaluronan acts as a pharmaceutical rather than as a lubricant as originally thought. In this regard, the effects of inert synthetic lubricants on arthritic joints have not previously been adequately investigated.

This study examines the effect of injecting an inert synthetic lubricant, perfluoroalkylether (PFAE16350), as a mechanical joint lubricant to prevent the development of osteoarthritis in a surgically induced model of osteoarthritis in the adult guinea pig.

Materials & Methods: Osteoarthritic changes were initiated in the hind knee joint of 12 adult male Dunkin-Hartley guinea-pigs by excision of the medial meniscus and anterior cruciate ligament.

After wound closure, the animals were randomly assigned to 1 of 2 groups: (1) Single intra-articular injection of 1ml synthetic, sterile lubricant (PFAE16350) or (2) Control group with single intra-articular injection of 1ml 0.9% sterile saline.

At 9 weeks after surgery, after sacrifice, knee arthrotomy was performed, the presence of synthetic lubricant noted and the articular cartilages examined for macroscopic evidence of osteoarthritis. These cartilages were then fixed, embedded, sectioned, stained and graded histologically for osteoarthritis according to a modified Mankin scoring system.

Immunohistochemical studies were performed to assess for any inflammatory or cytotoxic effect by the lubricant.

Results: All guinea-pigs remained healthy and mobile throughout the study.

Subjective macroscopic assessment of the medial tibial plateau osteophyte was noted to be larger and the articular surface more roughened in the control cases compared to the lubricated cases. Synthetic lubricant was noted at arthrotomy in all cases where it was injected.

Guinea-pig joints treated with the synthetic lubricant showed a mean modified Mankin score of 3.0 points compared with the guinea-pig joints treated with saline where the median modified Mankin score was 8.5 points (p< 0.001). There was no evidence of an inflammatory or cytotoxic response by immunohistochemical studies.

Discussion: This study has confirmed that inert synthetic perfluoroalkylether lubricants can remain in the articular space for prolonged periods and inhibit the development of osteoarthritis without initiating an inflammatory response. Synthetic lubricants such as PFAE16350 warrant further investigation for potential use in osteoarthritis.

A 12 year old girl presented with a history of intermittent pain in her left knee since she started walking. She was seen in the vascular clinic due to engorged veins in her left leg and was diagnosis of Klippel-Trenaunay syndrome was made. Her knee pain worsened and an orthopaedic opinion was obtained. A history of repeated knee effusion and swelling was noted.

Examination revealed partial gigantism of the left leg and reduced range of motion of the knee. There was soft tissue swelling of the knee with no effusion. Blood investigations were normal. X-rays showed an arthritic joint. MRI scans revealed synovial thickening and a vascular malformation suggesting a synovial haemangioma. She underwent Radical Open Synovectomy and excision of the haemangioma. Blood loss was minimal. Extensive haemosiderin deposition was noted along with Grade IV arthritic changes. Postoperative recovery was uneventful. Surgeons have been reluctant to excise synovial hemangiomas due to the risk of haemorrhage.

A recent paper from Switzerland suggested excision was possible with minimal blood loss. Haemosiderin deposition due to recurrent haemarthrosis may predispose to articular damage. We recommend early excision of synovial haemangiomas to minimise articular damage.

Introduction: The National Bone Bank of Ireland was established in June 1996 at Cappagh National Orthopaedic Hospital, Dublin in response to the increased demand of allogenic bone grafts in Ireland. We reviewed the Bone Bank performance since it started with special emphasis on Microbiological monitoring of bone allograft as infection is the main complication of bone allograft (Chapman and Villar 1992).

Material and Methods: The femoral head allograft is harvested from living volunteer donors who are undergoing primary total hip replacement at Cappagh Hospital and have been assessed by the Bone Bank Co-Ordinator.

Harvesting: The bone is retrieved and harvested at the time of total hip replacement according to a strict protocol.

Storage: The bone is stored in the “Quarantine” freezer at −80 degrees C for a minimum period of 180 days. Each specimen is subjected to a full technical review by the Bone Bank Co-Ordinator and Medical Director and only when results of screening confirmed negative, the bone designated suitable for “Issue Stock” freezer.

Issue of Allografts: Bone is supplied for use, only after receiving full details of recipient to allow tracking. The results of the culture swab taken at the time of implantation and details of any post operative infection in recipients are forwarded to the bone bank.

Results: From June 1996 to December 2003, 5089 Primary Total Hip Replacements done at Cappagh Hospital and 1921 (38%) femoral heads were harvested. 109 (5.7%) of grafts had initial positive swabs/chips and 22 of these were discarded because of second positive chips. 1457 femoral head grafts supplied to 876 recipients and were used in Revision Total Hip Replacement (60%), Spine Surgeries (15%), Revision Total Knee (12%), Fractures, Tumours, Foot and Ankle (12%). 6 swabs at the time of grafting in recipients grew Staphylococcus Epidermidis but no clinical infection reported in our follow-up system. To double check, we posted a questioner to all consultants with list and details of their recipient patients and only 2 cases of suspected grafts related infection reported.

Discussion and Conclusion: Microbiological surveillance of bone grafts protect recipients from infection and is useful as a quality control of the process of bone banking (Farrington et al 1998). Our study showed contamination rate of 5.7%. Minimum infection rate post Revision Hip Replacement has been reported by Tomford in 1990, but after massive femoral allograft, infection has been reported 4% – 5% (Tomford 1990) and over 11% by Lord et al in 1988. Our experience showed only 2 cases in spite of strict follow-up protocol. We follow the policy of discarding the heavily contaminated grafts (Chapman 1992).

The quality performance of a Bone Bank depend on a full time bone bank co-ordinator, identification of donors, retrieval and harvesting of grafts, blood and microbiological assessment, medical supervision for decisions about contaminated grafts, a strict follow-up protocol and a regular audit of bone bank (Ivory and Thomas 1993). We also suggest that regular correspondence to the consultant using the bone grafts will improve the accuracy of follow-up.