As part of a prospective RSA study into a new design of short-stem, trabecular metal, Co-Cr femoral components with modular necks and metal on polyethylene articulation, three patients presented with almost identical symptoms of pain and a large avascular mass within the operated hip. All three cases came to exploration and similar findings of a solid pseudotumour within the hip joint were found in all thee cases. Infection was not present. All cases were submitted to histology and reviewed by a pathologist with specific interest in tissue reactions to foreign materials. All three cases showed histological features classical of published descriptions of ALVAL (Aseptic Lymphocyte-dominated Vasculitis Associated Lesion). A consistent finding was fretting corrosion of the neck-stem junction. These cases demonstrate that Co and Cr ions can provoke adverse tissue reactions even in the absence of metal/metal articulations. This has design implications for all modular Co-Cr necks. The stem used in this study has been voluntarily withdrawn from the Australian market but is still being implanted in Europe. We make recommendations that modular trunnion-style Co-Cr necks not be used and alternative materials and design solutions be sought.

We previously compared component alignment in total knee replacement using a computer-navigated technique with a conventional jig based method. Improved alignment was seen in the computer-navigated group (Beaver et al. JBJS 2004 (86B); 3: 372–7.). We also reported two-year results showing no difference in clinical outcome between the two groups (Beaver et al. JBJS 2007 (89B); 4: 477–80). We now report our five-year functional results comparing navigated and conventional total knee replacement. To our knowlege this represents the first Level 1 study comparing function in navigated and conventional total knee replacement at five years.

An original cohort of 71 patients undergoing Duracon (Stryker Orthopaedics, St. Leonards, Australia) total knee replacement without patellar resurfacing were prospectively randomised to undergo operation using computer navigation (Stryker Image Free Computer Navigation System (version 1.0; Stryker Orthopaedics))(n=35) or a jig-based method (n=36). The two groups were matched for age, gender, height, weight, BMI, ASA grade and pre-operative deformity. All operations were performed by a single surgeon. All patients underwent review in our Joint Replacement Assessment Clinic at 3, 6 and 12 months and at 2 and 5 years. Reviews were undertaken by senior physiotherapist blinded to participant status using validated outcome scoring tools (Knee Society Score, WOMAC Score and Short Form SF-36 Score). All patients underwent CT scanning of the implanted prosthesis as per Perth CT Knee Protocol to assess component alignment.

After 5 years 24 patients in the navigated group and 22 patients in the conventional group were available for review. At 5 years no statistically significant difference was seen in any of the aforementioned outcome scores when comparing navigated and conventional groups. No statistically significant difference was seen between 2- and 5-year results for either group.

Due to the relatively low numbers in each group these data were compared with retrospective cohorts of navigated (n=100) and conventional (n=70) Duracon total knee replacements performed outwith this study over the same 5-year period. WITHIN the retrospective cohorts no statistically significant differences were found when comparing any of the aforementioned outcome scores. In addition, when comparing parallel scores between prospective and retrospective groups again no statistically significant differences were identified.

At 5-years post-operatively the functional outcome between computer navigated and conventional total knee replacement appears to be no different despite the better alignment achieved using navigation.

We report our five-year functional results comparing navigated and conventional total knee replacement. To our knowlege this represents the first Level 1 study comparing function in navigated and conventional total knee replacement at five years.

An origianl cohort of 71 patients undergoing Duracon (Stryker Orthopaedics, St. Leonards, Australia) total knee replacement without patellar resurfacing were prospectively randomised to undergo operation using computer navigation (Stryker Image Free Computer Navigation System (version 1.0; Stryker Orthopaedics))(n=35) or a jig-based method (n=36). The two groups were matched for age, gender, height, weight, BMI, ASA grade abd pre-operative deformity. All operations were performed by a single surgeon. Reviews were undertaken by senior physiotherpist blinded to participant status using validated outcome scoring tools (Knee Society Score, WOMAC Score and Short Form SF-36 Score). All patients underwent CT scanning of the implanted prosthesis as per Perth CT Knee Protocol to assess component alignment.

After 5 years 24 patients in the navigated group and 22 patients in the conventional group were available for review. At 5 years no statistically significant difference was seen in any of the aforementioned outcome scores when comparing navigated and conventional groups. No statistically significant differencewas seen between 2- and 5-year results for either group.

Due to the relatively low numbers in each group these data were compared with retrospective cohorts of navigated (n=100) and conventional (n=70) Duracon total knee replacements performed outwith this study over the same 5-year period. WITHIN the retrospective cohorts no statistically significant differences were found when comparing any of the aforementioned outcome scores. In addition, when comparing parallel scores between prospective and retrospective groups again no statistically significant differences were identified.

At 5-years post-operatively the functional outcome between computer navigated and conventional total knee replacement appears to be no different despite the better alignment achieved using navigation.

In order to avoid complications of hip arthroplasty such as dislocation, impingement and eccentric liner wear accurate acetabular orientation is essential. The three-dimensional assessment of acetabular cup orientation using two-dimensional plain radiographs is inaccurate. The aim of this study was to develop a CT-based protocol to accurately measure postoperative acetabular cup inclination and anteversion establishing which bony reference points facilitate the most accurate estimation of these variables.

An all-polyethylene acetabular liner was implanted into a cadaveric acetabulum. A conventional pelvic CT scan was performed and reformatted images created in both functional and anterior pelvic planes. CT images were transferred to a Freedom-Plus Graphics software package enabling an identical, virtual, three dimensional model of the cadaveric pelvis to be created. Using a computer interface this model could be ‘palpated’, bony landmarks accurately identified and definitive acetabular cup orientation established. Using original CT scans, acetabular cup inclination and anteversion were measured on five occasions by eight radiographers using differing predetermined bony landmarks as reference points. The intra- and inter-observer variation in measurement of acetabular cup orientation using varying bony reference points was assessed in comparison to the previously elucidated definitive cup position. Statistical analysis using appropriate ANOVA models was performed in order to assess the significance of the results obtained.

Virtually derived definitive acetabular cup orientation was measured showing cup inclination and anteversion as 41.0 and 22.5 degrees respectively. Mean CT-based measurement of cup inclination and anteversion by eight radiographers were 43.1 and 20.8 degrees respectively. No statistically significant difference was found in intra- and inter-observer recorded results. No statistically significant differences were found when using different bony landmarks for the measurement of inclination and anteversion (p= 0.255 and 0.324 respectively).

CT assessment of acetabular component inclination and anteversion is accurate, reliable and reproducible when measured using differing bony landmarks as reference points. We recommend measuring acetabular inclination and anteversion from the inferior acetabular wall/teardrop and posterior ischium respectively. The Perth CT hip protocol is easily reproducible in the clinical setting both in the routine assessment of hip arthroplasty patients and as research tool. In our unit its initial application will be to validate commercially available hip navigation systems.

Aim: In order to avoid complications of hip arthroplasty such as dislocation, impingement and eccentric liner wear accurate acetabular orientation is essential. The three-dimensional assessment of acetabular cup orientation using two-dimensional plain radiographs is inaccurate. The aim of this study was to develop a CT-based protocol to accurately measure postoperative acetabular cup inclination and anteversion establishing which bony reference points facilitate the most accurate estimation of these variables.

Methods: An all-polyethylene acetabular liner was implanted into a cadaveric acetabulum. A conventional pelvic CT scan was performed and reformatted images created in both functional and anterior pelvic planes. CT images were transferred to a Freedom-Plus Graphics software package enabling an identical, virtual, three dimensional model of the cadaveric pelvis to be created. Using a computer interface this model could be ‘palpated’, bony landmarks accurately identified and definitive acetabular cup orientation established. Using original CT scans, acetabular cup inclination and anteversion were measured on five occasions by eight radiographers using differing predetermined bony landmarks as reference points. The intra- and inter-observer variation in measurement of acetabular cup orientation using varying bony reference points was assessed in comparison to the previously elucidated definitive cup position. Statistical analysis using appropriate ANOVA models was performed in order to assess the significance of the results obtained.

Results: Virtually derived definitive acetabular cup orientation was measured showing cup inclination and anteversion as 41.0 and 22.5 degrees respectively. Mean CT-based measurement of cup inclination and anteversion by eight radiographers were 43.1 and 20.8 degrees respectively. No statistically significant difference was found in intra- and inter-observer recorded results. No statistically significant differences were found when using different bony landmarks for the measurement of inclination and anteversion (p= 0.255 and 0.324 respectively).

Conclusions: CT assessment of acetabular component inclination and anteversion is accurate, reliable and reproducible when measured using differing bony landmarks as reference points. We recommend measuring acetabular inclination and anteversion from the inferior acetabular wall/teardrop and posterior ischium respectively. The Perth CT hip protocol is easily reproducible in the clinical setting both in the routine assessment of hip arthroplasty patients and as research tool. In our unit its initial application will be to validate commercially available hip navigation systems.

Introduction: We previously compared component alignment in total knee replacement using a computer-navigated technique with a conventional jig based method. Improved alignment was seen in the computer-navigated group (Beaver et al. JBJS 2004 (86B); 3: 372–7.). We also reported two-year results showing no difference in clinical outcome between the two groups (Beaver et al. JBJS 2007 (89B); 4: 477–80). We now report our five-year functional results comparing navigated and conventional total knee replacement. To our knowlege this represents the first Level 1 study comparing function in navigated and conventional total knee replacement at five years.

Methods: An original cohort of 71 patients undergoing Duracon (Stryker Orthopaedics, St. Leonards, Australia) total knee replacement without patellar resurfacing were prospectively randomised to undergo operation using computer navigation (Stryker Image Free Computer Navigation System (version 1.0; Stryker Orthopaedics))(n=35) or a jig-based method (n=36). The two groups were matched for age, gender, height, weight, BMI, ASA grade and pre-operative deformity. All operations were performed by a single surgeon. All patients underwent review in our Joint Replacement Assessment Clinic at 3, 6 and 12 months and at 2 and 5 years. Reviews were undertaken by senior physiotherpist blinded to participant status using validated outcome scoring tools (Knee Society Score, WOMAC Score and Short Form SF-36 Score). All patients underwent CT scanning of the implanted prosthesis as per Perth CT Knee Protocol to assess component alignment.

Results: After 5 years 24 patients in the navigated group and 22 patients in the conventional group were available for review. At 5 years no statistically significant difference was seen in any of the aforementioned outcome scores when comparing navigated and conventional groups. No statistically significant difference was seen between 2- and 5-year results for either group.

Due to the relatively low numbers in each group these data were compared with retrospective cohorts of navigated (n=100) and conventional (n=70) Duracon total knee replacements performed outwith this study over the same 5-year period. WITHIN the retrospective cohorts no statistically significant differences were found when comparing any of the aforementioned outcome scores. In addition, when comparing parallel scores between prospective and retrospective groups again no statistically significant differences were identified.

Conclusion: At 5-years post-operatively the functional outcome between computer navigated and conventional total knee replacement appears to be no different despite the better alignment achieved using navigation.

Our ongoing aim is to assess the clinical outcome of joint replacement surgery; we wish to contrast the functional outcome of primary and revision patients, and examine what factors may influence this.

Method: Patient data was collected prospectively between Jan 1998 and April 2006. The assessment scores include, the Harris Hip Score, Knee Society Score, SF 36 Health Survey and WOMAC. We compare the pain and function parts of the Knee Society Score for Primary and Revision TKR and the Harris Hip Score for Primary and Revision THR.

Results: The Harris Hip Score improves significantly up to one-year post surgery, with the largest increase occurring at three months. Post surgery improvement then plateaus between one and two years and between two and five years. Revision hip replacement patients display a significant improvement in the Harris Hip Score at three months post surgery, but improvement plateaus after this up to two years. These results are presented graphically.

The Knee Society Score in primary total knee replacement patients improves significantly over time up to one-year post surgery for all components of the score, with the largest increase occurring at three months. Post surgery improvement then plateaus between 1 and 2 years. At 5 years post op both the total score and the function score significantly decrease while there is no change in the knee score component. All components of the Knee Society Score measured in revision knee replacement patients significantly improve at three months post surgery, after which time no further significant improvement is noted.

Discussion: Primary THR patients consistently had higher hip scores than revision patients at all time frames, indicating a better outcome for these patients. When stratified for reason for revision we postulate that a number of well functioning patients are significantly worse following revision surgery. This effect is not seen in the revision TKR group. The decrease in Knee Society Score to five years probably reflects the age of the patients at the time of surgery, which is older than hip replacement patients.

Implant alignment and rotation is important in total knee arthroplasty (TKA). If incorrect it leads to abnormal wear and premature loosening. However, little is known with regard to how these factors influences rehabilitation. Our aim was to identify which aspects of alignment affect functional outcome and Length of Stay. This is an ongoing study with 300 patients results expected by september 2008. Currently 159 patients underwent TKA between May 2003 and July 2004 at Royal Perth Hospital. A Duracon TKA (Stryker Corp) was implanted by multiple surgeons using either computer navigation or conventional jiging. A WOMAC and knee society score (KSS) were calculated on each patient by a physiotherapist at 6 months, 1 year and 2 years. Implant alignment was measured using the Perth CT protocol. A statistician used a combination of independent t-tests and one way analysis of variance to determine significance between groups.

Two groups of alignment were created to allow comparison. These were termed good alignment (< = 2 degrees of mechanical axis) and outlier group (> 2 degrees of mechanical axis). There were no difference between the two groups in terms of age, BMI and preop function. This suggest no confounding variables between the groups. Coronal femoral alignment as well as cumulative error (additive error in all planes of both components) were statistically significant. The p-values are 0.031 and 0.011 respectively. Cumulative error also had an impact on hospital stay, increasing it by 2 days when greater than 6(p=0.006). Trends towards better function at 1 year were seen with regards to sagittal alignment in both the femur and tibia, as well as coronal tibial alignment. It is expected by september 2008 that patient numbers will be double. This should provide the most comprehensive analysis of alignment versus function in the literature to date.

Functional outcome following TKA is multifactorial. However certain aspects of alignment, especially the cumulative error of alignment appear to have significant effects on function.

Femoral component malrotation is a major cause of patello-femoral complications in total knee arthroplasty. In addition, it can affect varus/valgus stability during flexion which can lead to increased tibiofemoral wear.

Debate exists on where exactly to rotate the femoral component. The three principal methods utilise different anatomical landmarks: the posterior condylar axis, the transepicondylar axis and the antero-posterior axis (Whiteside’s line).

A prospective randomised controlled trial was undertaken. Sixty consecutive patients undergoing total knee arthroplasty by a single surgeon (LML) at the Royal Perth Hospital were randomised into 3 groups based on the intra-operative method for measuring femoral rotation using the PFC sigma prosthesis (Depuy) with computer navigation (Depuy/Brainlab). All patients received the usual post-operative treatment, rehabilitation and JRAC (Joint Replacement Assessment Clinic) follow up. All underwent a CT scan according to the Perth CT protocol designed specifically to accurately measure component alignment and rotation.

No significant difference in femoral rotation was found between the three groups using a one-way analysis of variance (p=0.67). However, Whiteside’s line had a significantly greater variability than the posterior condylar or transepicondylar axis using the F Test for variances (p=0.02, p=0.03). In conclusion, whilst there was no significant difference in femoral rotation, Whiteside’s line did show greater variability (−6° to 3°), and therefore we recommend the use of either the transepicondylar or posterior condylar axis in Total Knee Replacement.

The aim of this study was to identify what aspects of implant alignment and rotation affect functional outcome after total knee arthroplasty (TKA). 159 TKAs were performed at the Royal Perth Hospital between May 2003 and July 2004. All patients underwent an objective and independent clinical and radiological assessment before and after surgery. A CT scan was performed at six months. The alignment parameters that were measured included: sagital femoral, coronal femoral, rotational femoral, sagital tibial, coronal tibial and femoro-tibial mismatch. The cumulative error score, which represents the sum of the individual errors, was calculated. Functional outcome was measured using the Knee Society Score (KSS).

Good coronal femoral alignment was associated with better function at 1 year (p=0.013). Trends were identified for better function with good sagital and rotational femoral alignment and good sagital and coronal tibial alignment. Patients with a low cumulative error score had a better functional outcome (p=0.015). These patients rehabilitated more quickly and their length of stay in hospital was 2 days shorter.

This study was to assess the accuracy of fixed posterior condylar referencing cutting blocks to the accuracy of combined epicondylar/AP axis referencing in femoral component rotation using a computer navigation system.

Seventy-five consecutive patients undergoing TKRs were randomized into two groups. The first received femoral component rotation by a computerized method that combined the epicondylar axis and Whitesides AP axis measurements to determine rotation. The second group had a zero or three-degree posterior referencing external rotation block, depending on which was closest to the epicondylar axis. All patients underwent axial CT scans of the distal femur to determine component rotation around the surgical epicondylar axis.

Femoral component alignment with the combined method as compared to fixed posterior alignment guides is statistically improved (p=0.001). In the posterior referencing group 43% were correctly rotated to the epicondylar axis but another 43% were malrotated by 3 degrees or more. The mean malrotation was 1.72 degrees (range 0–5) In the combined group 82% were correctly rotated and 11% were malrotated by 3 degrees or more. The mean malrotation was 0.51 degrees (range 0–4).

Conclusion: A combined computerized method of using the surgical epicondylar axis and Whitesides AP axis produces superior results when aiming for neutral femoral component rotation. Fixed posterior referencing blocks will produce errors in malrotation in over 50% of cases.

To compare the new technique of computer assisted knee arthroplasty (CAK) against the current gold standard conventional jig based technique (JBK), 75 consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. The CAK surgery was performed using a freehand technique that avoids violation of the medullary canal. Pre-and post-operative Knee society scores were collected. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol and pre-and post-operative Maquet views of the limb performed. Intra-operative soft tissue release together with postoperative pain scores and blood loss were also assessed.

CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032), femoral rotation (p=0.001), tibial varus/ valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoral-tibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer, a mean increase of 13 minutes (p=0.0001).

This is the first controlled study to assess all seven-alignment characteristics of knee arthroplasty in these two groups of patients.

The improvement in alignment resulted in this trial being stopped prematurely as 6 out of 7 of the initial variables had reached significance. It shows a clear improvement in component alignment with computer navigation. The reduction in blood loss in this surgery through not violating the medullary canal will also be beneficial.

The use of navigation systems to aid in the performance of total knee replacement has become an accepted method of treatment. Previous studies have shown that by using computer aided navigation the components can be implanted with more reproducible accuracy.

We present the results of a prospective randomised trial, with ethical committee approval that was performed to compare the use of a new, two-pin system with the original three-pin system to fix the tracker to bone. There were 37 patients in the two-pin group and 31 patients in the three-pin group. Pre-operative demographic data was similar. Patients were assessed pre and post operatively clinically using the Knee Society Score, WOMAC and SF36. Radiographic assessment was performed using “The Perth CT Protocol.”

At one year there was no significant difference clinically between either group. Radiographic assessment showed no significant difference in the results of all the prosthesis variables as measured by the Perth CT Protocol, except in the femoral prosthesis absolute varus/ valgus position, with the two-pin group being more accurate. The upgraded tracker fixing system in the computer navigation system allows as accurate implantation as the earlier system with less patient morbidity.

Introduction Maquet views are a well established method of determining the axial alignment of the lower limb in the coronal plane and their use in the assessment of total knee replacement is widespread. It is an awkward investigation for both patient and radiographer and we compared them to the information that can be obtained using the new generation of Helical CT scanners.

Results We prospectively studied a cohort of 60 patents undergoing TKR. As part of their routine post-operative follow-up they had a standard series of AP and Lateral radiographs (performed under fluoroscopic control) in addition to the Maquet views and a CT scan of their lower limbs. All plain films were performed at the same hospital by the same group of radiographers, while all CTs were performed on the same scanner using a predetermined protocol, and post processing performed by the same individual. Maquet views gave a good assessment of coronal alignment but were also shown to have a much high interobserver error than CT. Maquet views took on average three times longer for the radiographers to perform than CT, were often repeated as technically demanding, and patients (especially the elderly and infirm) often found it difficult and uncomfortable to comply with the required positioning. CT views on each patient (which incorporated standard slices and a scanogram) took a few minutes of time in the scanner allowing a quick throughput when patients arrived in clinic. Patients were supine, a position they all found easy to adopt, and radiographers reported that they found them less difficult to perform. The femoral and tibial axes were easily determined, and rotation easily assessed from the femoral epicondyles, negating the projection errors due to malrotation that may compromise the accuracy of Maquet views. Radiation dosage for the CT is higher than a single Maquet view, but these are often repeated due to poor exposure, increasing the dosage above that of CT.

Conclusions We have used a spiral CT protocol with much success and feel that its greater accuracy, coupled with the information gained on sagittal alignment and component rotation means that the older Maquet view has now been superceded. We also feel that the amount of information recorded by a single investigation may prove invaluable in subsequent investigation of pain or suspected loosening, and very helpful in planning any required revision.

Aim To compare the new technique of computer assisted knee arthroplasty (CAK) against the current gold standard conventional jig based technique (JBK).

Methods Seventy-Five consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. Pre and postoperative Knee society scores were collected. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol and pre and post operative Maquet views of the limb performed. Intra operative soft tissue release together with post operative pain scores and blood loss where also assessed.

Results CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032), femoral rotation (p=0.001), tibial varus/valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoraltibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer- a mean increase of 13minutes(p=0.0001).

Conclusions This is the first controlled study to assess all seven alignment characteristics of knee arthroplasty in these two groups of patients.

The improvement in alignment resulted in this trial being stopped prematurely as 6 out of 7 of the initial variables had reached significance. It shows a clear improvement in component alignment with computer navigation.

Introduction The aim of this study was to compare the new technique of computer assisted knee arthroplasty (CAK) against the conventional jig based technique (JBK).

Methods Seventy-five consecutive patients underwent knee replacement and were randomly allocated to either the CAK or JBK group. Post-operative CT scans were performed according to the Perth CT Knee Arthroplasty protocol to assess the accuracy of alignment. This measures seven parameters of alignment to an accuracy of one degree. Pre and post-operative Maquet views of the limb were also performed. Intra-operative soft tissue release together with post-operative pain scores and blood loss where also assessed.

Results CT scans performed show a statistically significant improvement in component alignment when using computer assisted surgery for femoral varus/valgus (p=0.032),femoral rotation (p=0.001),tibial varus/valgus (p=0.047) tibial posterior slope (p=0.0001), tibial rotation (p=0.011) and femoraltibial mismatch (p=0.037). Standing Maquet limb alignment was also improved (p=0.004) as was blood loss (p=0.0001). CAK surgery took longer, a mean increase of 13 minutes (p=0.0001).

Conclusions This is the first controlled study to assess all seven alignment characteristics of knee arthroplasty and use them to compare outcomes in conventional and computer assisted operations. It shows a clear improvement in component alignment with computer navigation.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source

The concept of two-stage revision of infected total hip arthroplasties is well established in the literature. What has been lacking has been a user friendly, simple, safe, cost-effective interim prosthesis which can achieve hip stability, maintain ambulatory status and still deliver antibiotics at high local concentrations. Other commercially available products are expensive, difficult to implant and prone to dislocation. We have developed a modular, antibiotic-laden spacer hemiarthroplasty of the hip which has been fully bench tested. The prosthesis consists of a head/neck module utilising antibiotic impregnated bone cement (PMMA) as the bearing surface and a stainless steel neck. This can be assembled onto a polyacetal (Delrin) stem of varying lengths and diameters. Bone defects are accommodated with hand moulded PMMA at the time of implantation.

We have inserted 47 of these implants in the period 9/97 to 5/2000. 28 of these have been retrieved and submitted for biomechanical analysis at the Royal Perth Hospital Implant Retrieval Laboratory.

This paper presents the concept of the implant, the clinical results, the results of retrieval analysis and elutional studies on antibiotic release from the implant.

We have analysed the retrieved implants and there have been no implant failures. Two implants have been fractured during extraction and one has dislocated secondary to subsidence. Wear analysis has shown polishing of the PMMA in the weightbearing area of the head.

Elution studies are ongoing but suggest that antibiotic release is continuing for up to 8 weeks post implantation providing ambulation is encouraged. Clinical results indicate success rates comparable to other published reports of infected total hip arthroplasties.

This implant in the hands of a variety of orthopaedic surgeons has proven itself simple to use and to maintain ambulatory status to patients whilst maximising antibiotic delivery to the infected hip.