In 2020 almost 90% of femoral heads for total hip implants in Germany were made of ceramic. Nevertheless, the cellular interactions and abrasion mechanisms in vivo have not been fully understood until now. Metal transfer from the head-neck taper connection, occurring as smear or large-area deposit, negatively influences the surface quality of the articulating bearing. In order to prevent metal transfer, damage patterns of 40 Biolox delta ceramic retrievals with CoC and CoPE bearings were analysed. A classification of damage type and severity for each component (n=40) was done according to an established scoring system. To investigate the physical properties, the surface quality was measured using confocal microscopy, quantitative analysis of phase composition were performed by Raman spectroscopy and qualitative analysis of metal traces was done by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The periprosthetic tissue was analysed for abrasion particles with SEM and EDX. Both bearing types show different damage patterns. Dotted/ drizzled metal smears were identified in 82 % of CoC (n=16) and 96 % of CoPE (n=24) bearings. Most traces on the ceramic heads were identified in the proximal area while they were observed predominantly in the distal area for the ceramic inlays. The identified marks are similar to those of metallic bearings. Metallic smears lead to an increase of up to 30 % in the monoclinic crystalline phase of the ceramic. The roughness increases by up to six times to Ra=48 nm. Ceramic and metallic wear particles from the articulating surfaces or head neck taper junctions were found in the periprosthetic tissue. Damage patterns on CoC hip implants seem to be similar to those of metallic implants. More detailed analysis of CoC implants are needed to understand the described damage patterns and provide advice for prevention

Introduction

Acetabular component orientation is an important determinant of outcome following total hip arthroplasty (THA). Although surgeons aim to achieve optimal cup orientation, many studies demonstrate their inability to consistently achieve this. Factors that contribute are pelvic orientation and the surgeon's ability to correctly orient the cup at implantation. The goal of this study was to determine the accuracy with which surgeons can achieve cup orientation angles.

The Hospital (Trust) guidelines generally recommend 40mg of Low molecular weight heparin (LMWH) twice daily (BD) for all patients over 100kg for those undergoing total hip (THR) and knee replacements (TKR) respectively. British National Formulary (BNF) recommends 40mg of LMWH once daily (OD) for all patients regardless of their overall weight or body mass index (BMI). We evaluated the outcome of prophylactic LMWH dosage for patients undergoing THR and TKR by monitoring surgery related venous-thromboembolic events up to a minimum of three months after surgery. A retrospective audit was carried out after obtaining institutional approval and all consecutive elective patients weighing over 100kg and undergoing THR and TKR were included. All patients were followed up for a minimum of 3 months after their operation to investigate the dose of prophylactic LMWH received, and whether they had developed any venous thromboembolic events (VTE) post operatively. This was done using a combination of electronic notes, drug charts and deep venous thrombosis (DVT) or computed tomography pulmonary angiogram (CTPA) reports on the hospital/trust database. A total of 53 patients underwent elective THR (18) and TKR (35) between the period of March 2017 and September 2017. Forty-four patients received 40 mg OD and 9 patients had 40 mg BD. None of the patients developed a confirmed DVT or pulmonary embolism in the 3 months following surgery regardless of the dose received. We demonstrate that there is no clinical benefit in having patients over 100kg on twice daily LMWH with the aim of preventing post-op thromboembolic complications. This conclusion is in line with the BNF recommendations for VTE prophylaxis

Patients with Paget's Disease of Bone (PDB) more frequently require total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, controversy remains regarding their outcome. This project aims to evaluate the current literature regarding outcomes following THA and TKA in PDB patients.

MEDLINE, EMBASE and Cochrane databases were searched on February 15th, 2022. Inclusion criteria comprised studies evaluating outcomes following THA/TKA in PDB patients. Quality of included studies was assessed using the Newcastle-Ottawa Scale.

19 articles (published between 1976–2022) were included, comprising 58,695 patients (48,766 controls and 10,018 PDB patients), from 209 potentially relevant titles. No study was of high quality. PDB patient pooled mortality was 32.5% at mean 7.8(0.1-20) years following THA and 31.0% at mean 8.5(2-20) years following TKA. PDB patient revision rate was 4.4% at mean 7.2(0-20) years following THA and 2.2% at mean 7.4(2-20) years following TKA. Renal complications, respiratory complications, heterotopic ossification, and surgical site infection were the most common medical and surgical complications.

The largest systematic review, to date, evaluating outcomes following THA and TKA in PDB patients. All functional outcome scores improved. PDB patient revision rate was comparable to UK National Joint Registry. However, there is a significant need for prospective matched case-control studies to robustly compare outcomes in PDB patients with unaffected counterparts.

Background. Frequency of primary total hip (THA) and total knee (TKA) arthroplasty procedures is increasing, with a subsequent rise in revision procedures. This study aims to describe timing and excess surgical mortality associated with revision THA and TKA compared to those on the waiting list. Methods. All patients from 2003–2013 in a single institution who underwent revision THA and TKA, or added to the waiting list for the same procedure were recorded. Mortality rates were calculated at cutoffs of 30- and 90-days post-operation or addition to the waiting list. Results. 561 and 547 patients were available for the survivorship analysis in the revision THA and TKA groups respectively. Following exclusion, 901 and 832 patients were available for the 30-day analysis and 484 and 568 patients for the 90-day analysis in the revision THA and revision TKA waiting list groups respectively. The 30- and 90-day mortality rate was significantly greater for the revision THA group compared to the waiting list group (excess surgical mortality of 0.357%, 95% confidence interval 0.098% to 0.866%; p=0.037) (odds ratio of 5.22, 95% confidence interval 0.626 to 43.524; excess surgical mortality of 0.863%, 95% confidence interval 0.455% to 1.153%; p=0.045). The 30- and 90-day mortality rate was not significantly greater for the revision TKA group compared to the waiting list group (excess surgical mortality of zero) (excess surgical mortality of 0.366%, 95% confidence interval 0.100% to 0.651%; p=0.075). Conclusions. Revision THA is associated with a significant excess surgical mortality rate at 30- and 90-days post operation when compared to the waiting list for the same procedure. However, we have been unable to quantify any increased risk after revision TKA. We would encourage other authors with access to larger samples to use our method to quantify excess mortality after revision TKA. Level of Evidence. III-Retrospective Cohort Study

Aim. To investigate the validity of threshold values for the Oxford Hip and Knee Score (OHS and OKS) for treatment success 12 months after total knee or hip replacement. Methods. Questionnaires were administered to patients undergoing total hip (THA) or knee (TKA) replacement before and 12 months after surgery alongside questions assessing key accepted aspects of treatment success (satisfaction, pain relief, functional improvement) to form a composite criterion of success and assessed using receiver operator characteristic (ROC) analysis. Thresholds providing maximum sensitivity and specificity for predicting treatment success were determined for the total sample and subgroups defined by pre-surgery scores. Results. Data was available for 3203 THA and 2742 TKA patients. Applying the composite treatment success criterion, 52.7% of the TKA and 65.6% of the THA sample reported a successful treatment outcome. Accuracy for predicting treatment success was high for the OHS and OKS (both areas under curve 0.87). For the OHS a threshold value of 37.5 points showed highest sensitivity and specificity in the total sample, while for the OKS the optimal threshold was 32.5 points. Depending on pre-surgery scores optimal thresholds varied between 32.5 and 38.5 for the OHS and 28.5 and 35.5 for the OKS. Conclusions. This is the first study to apply a comprehensive composite “success” anchor to the OHS and OKS in order to determine thresholds for successful treatment with total joint replacement. Compared to widely publicised postoperative satisfaction metrics, far fewer patients report success with our composite anchor

Abstract

Objectives. We aimed first to summarise minimal clinically important differences (MCIDs) after total hip (THR) or knee replacement (TKR) in health-related quality of life (HRQoL), measured using the Short-Form 36 (SF-36). Secondly, we aimed to improve the precision of MCID estimates by means of meta-analysis. Methods. We conducted a systematic review of English and non-English articles using MEDLINE, the Cochrane Controlled Trials Register (1960–2011), EMBASE (1991–2011), Web of Science, Academic Search Premier and Science Direct. Bibliographies of included studies were searched in order to find additional studies. Search terms included MCID or minimal clinically important change, THR or TKR and Short-Form 36. We included longitudinal studies that estimated MCID of SF-36 after THR or TKR. Results. Three studies met our inclusion criteria, describing a distinct study population: primary THR, primary TKR and revision THR. No synthesis of study results can be given. Conclusions. Although we found MCIDs in HRQoL after THR or TKR have limited precision and are not validated using external criteria, these are still the best known estimates of MCIDs in HRQoL after THR and TKR to date. We therefore advise these MCIDs to be used as absolute thresholds, but with caution

Introduction

In total hip arthroplasty, a high radiographic inclination angle (RI) of the acetabular component has been linked to short- and long-term complications. There are several factors that lead to RI outliers including cup version, pelvic orientation and angle of the cup introducer relative to the floor. The primary aim of this study was to analyse what increases the risk of having a cup with an RI outside the target zone when controlling cup orientation with a digital inclinometer.

Patient reported outcome measures (PROMs) are important for assessing the results of lower limb arthroplasty. Unrealistic or uneducated expectations may have a significant negative impact on PROMs even when surgery is technically successful. This study's aim was to quantify pre-operative expectations of Scottish patients undergoing total hip and knee replacement (THR/TKR). 100 THR and 100 TKR patients completed validated questionnaires (from the Hospital for Special Surgery) prior to their operation after receiving standard pre-operative information (booklet, DVD, consultations). Each patient rated expectations from very important to not having the expectation. A total score was calculated using a numerical scale for the grading of each expectation. Univariate regression analysis was used to investigate the relationship between demographics and expectation score. The THR cohort had mean age 66.2 (SD 10.5), 53% female, mean BMI 29.0 (SD 5.1) and mean Oxford score 44 (SD 7). The TKR cohort had mean age 67.6 (SD 8.5), 59% female, mean BMI 32.8 (SD 5.8) and mean Oxford score 44 (SD 8). 100% THR and 96% TKR patients had 10 or more expectations of their operation. All expected pain relief. Other improvements expected were: walking for 100% THA and 99% TKA patients; daily activities for 100% THAs and 96% TKAs; recreational activities for 96% THAs and 93% TKAs; sexual activity for 66% THAs and 59% TKAs; psychological well-being for 98% THAs and 91% TKAs. Regression analysis showed increasing age lowered expectations in both THR (p=0.025) and TKR (p=0.031) patients but that gender, BMI and Oxford score were not significantly related to expectations. This study highlights that patients expect far more than pain relief and improved post-operative mobility from their operation. It is important to discuss and manage these expectations with patients prior to surgery. By doing so, patient satisfaction and PROMs should further improve

Background. To aid recovery, rehabilitation is an important adjunct to surgery. Acknowledging the MRC framework for complex interventions we assessed the evidence-base for components of comprehensive rehabilitation in total hip (THR) and total knee replacement (TKR) pathways. Methods. We conducted systematic reviews and meta-analyses of randomised controlled trials (RCT) of pre-surgical exercise and education, occupational therapy and post-operative physiotherapy. In feasibility RCTs we explored acceptability of pain self-management and occupational therapy before THR, and physiotherapy after TKR. We searched trial registers for ongoing RCTs. Results. Pre-surgical interventions. Systematic review identified 38 interventions targeting physical function before THR and TKR. Interventions showed functional benefit compared with controls, standardised mean difference (SMD) 0.32 (95% CI 0.20, 0.44; p<0.00001). In 27 studies targeting in-hospital recovery, intervention patients had lower anxiety, SMD 0.38 (95% CI 0.13, 0.63; p=0.003), and earlier mobilisation by 4 hours (95% CI 0.04, 0.30; p=0.009). In 20 studies, interventions targeting long-term recovery showed no benefit for function or pain. We randomised 88 patients into a feasibility RCT of group-based pain self-management. Attendees were highly satisfied but participation was low. Pre-operatively, many patients may perceive that only surgery can treat their symptoms. Occupational therapy. Systematic review identified 7 small RCTs in THR. Function improved in patients receiving occupational therapy, SMD 0.40 (95%CI 0.09, 0.70; p=0.01) but this was not sustained post-surgery. In our feasibility study with 44 patients randomised to pre-operative provision of aids and appliances or usual care, the intervention was delivered successfully and acceptable to participants. We identified no ongoing studies. Post-discharge physiotherapy. Systematic review identified 7 small studies suggesting that physiotherapy after TKR gives functional benefit at 3–4 months, SMD 0.37 (95%CI 0.12, 0.62; p=0.004) but not at later follow up. As noted in a recent review in THR, quality of evidence was limited. Our feasibility study evaluated six weeks of group-based activity-orientated rehabilitation in 46 TKR patients. The programme was well-received and attendance good. A fully-powered RCT is underway. We identified two ongoing studies targeting patients at risk of, or with, poor recovery. Conclusion. The evidence-base for comprehensive rehabilitation in THR and TKR is growing. Pre-surgical interventions may be effective but, in isolation, not acceptable to many patients. Ongoing definitive trials in TKR physiotherapy will guide future care. Well-designed trials of physiotherapy after THR and occupational therapy are needed. Ultimately, rehabilitation interventions throughout THR and TKR pathways may provide optimal care but this will need appropriate evaluation

Background. The Arthroplasty Pain Experience (APEX) studies are two randomised controlled trials in primary total hip (THR) and knee replacement (TKR) at a large UK orthopaedics centre. APEX investigated the effect of local anaesthetic wound infiltration (LAI), administered before wound closure, in addition to standard analgesia, on pain severity at 12 months. This abstract reports results of the within-trial economic evaluations. Methods. Cost-effectiveness was assessed from the health and social care payer perspective in relation to quality adjusted life years (QALYs). Resource use was collected from hospital records and patient-completed postal questionnaires, and valued using unit cost estimates from local NHS Trust and national tariffs. Missing data were imputed using chained equations. Costs and outcomes were compared per trial arm and plotted in cost-effectiveness planes. The economic results were bootstrapped incremental net monetary benefit statistics (INMB) and cost-effectiveness acceptability curves. One-way deterministic sensitivity analyses explored any methodological uncertainty. Results. In both trials, LAI was cost-saving and more effective than standard care. Using the £20,000 per QALY threshold, in THR, the INMB was £1,125 (95%BCI, £183 to £2,067) and the probability of being cost-effective was over 98%. In TKR, the INMB was £264 (95%BCI, −£710 to £1,238), with only 62% probability of being cost-effective. Considering an NHS perspective only, LAI was no longer dominant in THR, but still highly cost-effective, with an INMB of £961 (95%BCI, £50 to £1,873). Conclusions. Administering LAI is a cost-effective treatment option in THR and TKR surgeries. The evidence is stronger for THR, because of larger QALY gain. In TKR, there is more uncertainty around the economic result, and smaller QALY gains, but results point to LAI being cheaper than standard analgesia, which includes a femoral nerve block. Trial Registration. ISRCTN96095682, 29/04/2010. Funding. NIHR Programme Grant for Applied Research RP-PG-0407-10070

SL-PLUS MIA stem (Smith & Nephew Orthopaedics AG) is a modified implant of Zweymuller type SL-PLUS standard stem (Smith & Nephew Orthopaedics AG). We constructed finite element (FE) models and analysed equivalent stresses in the femur. In addition, we measured bone mineral density (BMD) in the femur by dual-energy X-ray absorptiometry (DEXA) after THA. The purpose of this study was to investigate the equivalent stress and to compare the results of the FE analyses with changes in BMD after THA. Twenty-one patients (18 women and 3 men) who underwent primary cementless THA with SL-PLUS MIA or SL-PLUS formed the basis of this study. Eleven patients received SL-PLUS MIA and ten patients received SL-PLUS. Zones were defined according to Gruen's system (zones 1∼7). Computed-tomography (CT) images of the femur were taken before and at 1 week after THA. FE models of the femur and prosthesis were obtained from CT data by Mechanical Finder (Research Center of Computational Mechanics Inc., Tokyo, Japan), software that creates FE models showing individual bone shape and density distribution. Equivalent stresses were analysed in zones 1 to 7 and compared to the DEXA data. FE studies revealed that there was no significant difference in equivalent stress between SL-PLUS MIA and SL-PLUS. BMD was maintained after THA in zones 3, 4, and 5, whereas BMD decreased in zones 2, 6, and 7. In zone 1, BMD decreased in SL-PLUS MIA stem group by 14%, while BMD was maintained in SL-PLUS standard stem.

Total Hip Arthroplasty (THA) is a well-established, cost-effective treatment for improving function and alleviating pain in patients who have disabling hip disease with excellent long-term results. Based on the excellent results, there is an ongoing trend for THA to be performed in younger and more active patients, having higher physical demands on their new total joints.

Polyethylene (PE) wear and its biological consequences are one of the main causes of implant failure in THA. Macrophages phagocytise PE wear particles and this will result in osteolysis and loss of periprosthetic bone. The risk of these complications can be estimated in relation to the amount of volumetric wear based on two assumptions: that the number of PE particles dispersed in the peri-prosthetic tissues is controlled by the amount of PE wear; and that the development of osteolysis and the resulting aseptic loosening is triggered by these PE particles. Based on these assumptions, a model was developed to estimate the osteolysis-free life of a THA, depending on the Linear Wear Rate (LWR) and femoral head size of the PE bearing.

A review of the literature was conducted to provide an estimate of the radiologic osteolysis threshold based on the volumetric wear of the PE bearing. This review demonstrates that this radiologic osteolysis threshold is approximated 670 mm3 for conventional PE. The osteolysis-free life of the THA was estimated by simply dividing this threshold volume by the annual Volumetric Wear Rate (VWR) of the bearing. The annual VWR is basically controlled by two parameters: (1) annual LWR and (2) head size, and was calculated by using published formulae.

For 28 mm heads, following osteolysis-free life was determined in function of the annual LWR. LWR: 10 µm/y => 116.6 years / LWR: 25 µm/y => 46.6 years / LWR: 50 µm/y => 23.3 years / LWR: 100 µm/y => 11.6 years. For 40 mm heads, following osteolysis-free life was determined in function of the annual LWR. LWR: 10 µm/y => 57.1 years / LWR: 25 µm/y => 22.9 years / LWR: 50 µm/y => 11.4 years / LWR: 100 µm/y => 5.7 years.

The osteolysis-free life determined by this model is in good agreement with the clinical results of PE bearings having a 28 mm head size and demonstrates that extreme low LWRs are mandatory to assure a descent osteolysis-free life for THA (PE bearings) using large heads, such as 40 mm. For such head sizes, small variations of the LWR may have large impacts on the osteolysis-free life of the THA.

Introduction. Total hip arthroplasties (THAs) in young patients are associated with high failure rates. We always use cemented total hip implants, however, in cases with acetabular bone stock loss we perform bone impaction grafting. Our purpose was to evaluate the outcome of 69 consecutive primary cemented total hips in patients younger than 30 years followed between 2 to 18 years. Methods. Between 1988 and 2004, 69 consecutive primary cemented THAs (mainly Exeters) were performed in 48 patients (32 women, 16 men) younger than thirty years. Average age at time of operation was 25 years (range, 16 to 29 years). Twenty-nine hips (42%) underwent acetabular bone impaction grafting because of acetabular bone loss. Mean follow-up was 10 years (range, 2 to 18 years). Revisions were determined, Harris Hip Score (HHS), and Oxford Hip Questionnaire Score (OHQS) were obtained and radiographs were analyzed. Survival was calculated using the Kaplan-Meier method. Results. No patients were lost to follow-up, but 3 patients (4 hips) died during follow-up, none of whom had underwent revision. Eight revisions were performed: 3 septic loosenings (6, 7, and 8 years post-operative) and 5 aseptic cup loosenings (2, 3, 4, 5, and 9 years post-operative). No stems were loose. The average HHS and OHQS at follow-up were 89 points (range, 55 to 100 points) and 19 points (range, 12 to 42 points), respectively. Using Kaplan-Meier analysis, the cumulative survival with revision for any reason as end point was 83% (95% CI, 69 - 92%) at 10 years. Excluding the infections, the survival rate was 90% (95% CI, 77 - 96%) with revision for aseptic loosening. The outcome of the patients who underwent acetabular bone impaction grafting was comparable to the primary cemented hips with a survival of 89% (95% CI, 62 - 97%) with revision for any reason as an end point. Excluding the infections, the survival rate was 95% (95% confidence interval, 72 - 99%) at ten years with revision for aseptic loosening as the end point. Conclusion. Primary cemented total hip arthroplasties in very young patients show satisfactory medium-term results, however, in cases with acetabular bone stock loss, a reconstruction with bone impaction grafting is advisable

Introduction

There is much current debate concerning wear and corrosion at the taper junctions of large head total hip replacements, particularly metal-on-metal hips. Is such damage a modern concern or has it always occurred in total hip replacement but not previously noted. To investigate this five explanted V40 Exeter femoral stems (Stryker Howmedica) were obtained following revision surgery at a single centre. In all cases, the 24–26 mm femoral heads were still attached.

Introduction. The treatment of osteonecrosis of the femoral head (ONFH) in young and active patients remains a challenge. The purpose of this study was to determine and compare the clinical and radiographic results of the two different hip resurfacing systems; hemi-resurfacing and metal-on-metal total hip resurfacing in patients with ONFH. Methods. This study was a retrospective review of 20 patients with 30 hips who had ONFH and underwent hemi-resurfacing or total hip resurfacing between November 2002 and February 2006. We mainly performed hemi-resurfacing for early stage ONFH, and total hip resurfacing for advanced stages. Fifteen hips in 11 patients had a hemi-resurfacing component (Conserve, Wright Medical Co) with a mean age at operation of 50 years and an average follow-up of 5.5 years. Fifteen hips in 10 patients had a metal-on-metal total hip resurfacing component (Birmingham hip resurfacing, Smith & Nephew Co.) with a mean age at operation of 40 years and an average follow-up years. Results. The average postoperative Japanese Orthopaedic Association (JOA) hip scores were 86 points in hemi-resurfacing and 96 points in total hip resurfacing. The difference of pain score was a main factor to explain the difference of total JOA hip score in the two groups. Both implants were radiographically stable, but radiolucent lines around the metaphyseal stem were more frequent in total hip resurfacing. In hemi-resurfacing patients, ten of 15 hips had groin pain or groin discomfort and three hips were revised to total hip arthroplasties (THA) because of femoral neck fracture, acetabular protrusio, and osteoarthritic changes, respectively. In total hip resurfacing patients, there were no revisions and no groin pain observed. Conclusion. In the prosthetic treatment of young active patients with ONFH, it is theoretically desirable to choose an implant with a conservative design in anticipation of the future revision surgery. Hemi-resurfacing hip arthroplasty is the most conservative implant for the treatment of ONFH. However, the results of hemi-resurfacing in this study have been disappointing due to high revision rates and insufficient pain relief despite of the good implant stability. However, the pain relief and implant survivorship after total hip resurfacing were superior to the results of hemi-resurfacing, although the usages of the total hip resurfacing were for more advanced cases. These results suggest that total hip resurfacing was a more valuable treatment option for active patients with ONFH than hemi-resurfacing

GIRFT was published in the United Kingdom with the aim of streamlining primary care pathways, secondary care, creating a network of hospitals and treatment centres and to better regulate introduction of new implants. It also proposed the use of Orthopaedic Devices Evaluation Panel (ODEP) 10A* rated cemented implants in hip arthroplasty.

Aim: The purpose of this study was to assess the effects of adopting GIRFT on surgical time, length of stay, changes to the implants used and number of cases per surgical list.

Prior to adopting GIRFT, elective primary total hip replacement (THR) was predominantly uncemented THR. Age, sex, Body Mass Index (BMI), American Society of Anesthetiss (ASA), closure technique and surgical time of 50 consecutive primary uncemented THR were analysed to identify the appropriate statistical methods. Mean and standard deviation for surgical time were identified. Threshold increase in surgical time was set at 20 minutes. Based on expected difference of 20 minutes and standardised difference, minimum sample size was calculated to be 19. Prospective data on 60 consecutive uncemented THR and 30 consecutive cemented primary THR were included in this study. Inclusion criteria – primary THR for arthritis by single surgeon. Exclusion criteria – previous hip surgery, complex primary, abnormal anatomy.

No differences in age, sex, BMI, ASA and length of stay between the two groups. Surgical time was significantly increased by 28 minutes (p<0.001). Implants used changed from 7A*/5A* uncemented THR to 10A* (18/30) and 7A*(12/30) cemented THR. There was a reduction in number of THR done per surgical list due to the increase in surgical time (3 instead of 4).

GIRFT compliance improved from 0% cemented to 100% cemented. 0% 10A* rated implants to 66% 10A* rated implants. Undertaking cemented THR instead of uncemented THR is associated with significantly increased surgical time. Hence, number of THR surgeries performed in a day's list is accordingly reduced. There is potential for financial loss when the savings in the implants used is compared with the reduction in the number of surgeries performed.

We made a semiquantitative study of the comparative histology of pseudomembranes from 12 loose cemented ceramic-ceramic and 18 metal-polyethylene total hip replacements. We found no significant difference in cellular reaction between the two groups, but there was a major difference in the origin of the particulate debris. In the metal-polyethylene group, polyethylene of articular origin was predominant, while in the ceramic-ceramic group the cellular reaction appeared to be a response to zirconia ceramic particles used to opacify cement used for fixation.

Isolation and characterisation of the debris showed that the zirconia particles formed the greatest proportion (76%) in ceramic-ceramic hips, while alumina debris of articular origin formed only 12%.

Our study has indicated that aseptic loosening of ceramic cups is not due to a response to debris generated at the articular interface, but to mechanical factors which lead to fragmentation of the cement.

Summary Statement

The frictional torque of ceramic-on-ceramic bearings tended to increase with increasing the bearings size (32, 48, 56mm). However, the frictional torque was significantly lower than that measured on metal-on-metal bearings under well positioned and well lubricated conditions.