A randomised study comparing resection of acetabular bone at resurfacing and total hip replacement

Outcome of hip resurfacing revision through the Hueter-anterior approach

BACKGROUND

The Hueter-Anterior Approach (HAA) with its limited soft tissue and internervous dissection has been shown to be an effective approach for primary total hip and hip resurfacing arthroplasty (HRA). The purpose of this study is to evaluate the clinical outcome of patients requiring revision of HRA to total hip replacement using the HAA, assessing function and complications.

METHODS

We performed a retrospective review of a prospectively maintained research database. Between 2006 and 2015, 555 primary metal-on-metal (MoM) HRAs were performed via the HAA; we identified 33 hips in 30 patients that required revisions for aseptic causes to THA: aseptic loosening of acetabulum in 12 and femoral in 7, 10 for pseudotumour/ALTR, 4 for femoral neck fracture. All revision surgeries were performed through a HAA by a single surgeon who had also performed the index operation. PROMs were collected preoperatively and yearly at various timepoints postoperatively.

RESULTS

The mean age at time of revision was 48.9 years (±5.3 SD) for 22 males (67%) and 11 females (33%). The mean time to revision surgery/failure of hip resurfacing was 3.3 years (±2.4 SD). There were 5 major reoperations with 3 infections, 1 acetabular loosening and 1 trunnionosis. There were significant improvements in multiple PROMs.

CONCLUSIONS

The HAA is a viable surgical approach for revision of HRA with smaller initial HRA acetabular components generally requiring a relatively larger acetabular compoent at time of revision. Patients reported improvement in symptoms and function and a lower risk of subsequent reoperation than what has previously been reported for failed MoM bearings.

Clinical, functional and radiographic long-term follow-up (7-12 years) of Birmingham Hip Resurfacing, including metal ions evaluation: a single surgeon series

Hip resurfacing arthroplasty (HRA) has been advocated as an attractive therapy for a younger, more demanding patient population with debilitating hip osteoarthritis. Controversies surrounding metal-on-metal (MoM) hip resurfacing have, however, led to a significant decline in the popularity of the HRA. Despite this, substantial evidence supports the use of specific implants in a selected group of patients. This is a continued retrospective analysis of a single surgeon series of the Birmingham Hip Resurfacing (BHR). Initial medium-term analysis was done in 2011 and published by Van der Bracht et al.13. This analysis includes a long-term follow-up of 7 to 12 years, including functional scoring (HHS, HOOS and UCLA activity score), metal ion evaluation and survival analysis. Failure was defined as revision for any cause. A total of 267 resurfacing procedures with the BHR were included in 247 patients. We had a mean follow-up of 8.3 years. Overall survival at ten years was 94.8%(97.2% for males and 90.1% for females). There was a statistically significant increase in mean HHS score at follow-up (56.03 - IQR 47-65 to 96.07 - IQR 96-100). Elevated metal ions were correlated with a statistically significant increase in the probability of complications. This cohort study further proved that hip resurfacing arthroplasty with the Birmingham Hip Resurfacing implant provides a good alternative to conventional total hip arthroplasty in young patients. There was a significant increase in functional scores at follow-up. There is further evidence of less favorable outcomes in female patients.

Comparison of iliopsoas tendonitis after hip resurfacing arthroplasty and total hip arthroplasty: A case-controlled investigation using a validated simulation

Iliopsoas tendonitis, typically caused by impingement with the acetabular cup, occurs in up to 18% of patients after total hip arthroplasty (THA) and up to 30% of patients after hip resurfacing arthroplasty (HRA). We have developed a simulation for detecting iliopsoas impingement and validated it in a previous study of THA patients. However, due to the difference in incidence between HRA and THA, this study had two aims. First, to validate the simulation in a cohort of HRA patients and, second, to comparethe results of the HRA and THA patients to understand any differences in their etiology. We conducted a retrospective search in an experienced surgeon's database for HRA patients with iliopsoas tendonitisand control patients without iliopsoas tendonitis, resulting in two cohorts of 12 patients. Using CT scans, 3D models of the each patient's prosthetic and bony anatomy were generated, landmarked, and simulated. Regarding validation of the simulation for HRA patients, impingement significantly predicted the probability of iliopsoas tendonitis in logistic regression models and the simulation had a sensitivity of 83%, specificity of 100%, and an AUC ROC curve of 0.95. Unexpectedly, the HRA cohort exhibited less impingement than the THA cohort. Our novel simulation has now been demonstrated to detect iliopsoas impingement and differentiate between the symptomatic and asymptomatic cohorts in investigations of THA and HRA patients. This tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.

Long-Term Outcomes of Birmingham Hip Resurfacing Arthroplasty: A Systematic Review of Independent Series with At Least 10 Years of Follow-up

Background

Hip resurfacing arthroplasty (HRA) provides an attractive alternative to total hip arthroplasty (THA) for the management of osteoarthritis in younger, more active patients; however, concerns persist over complications specific to HRA. The aims of this systematic review were to assess the documented long-term survival rates of the metal-on-metal BIRMINGHAM HIP Resurfacing System at a follow-up of at least 10 years and to analyze the functional outcomes and cause of failures.

Methods

A systematic review was undertaken of all published cohort studies available in the MEDLINE, Cochrane, Embase, and PubMed research databases up to December 2021, as recommended by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data extraction was focused on survival rates, causes of failure, and functional outcomes. Survival estimates at 10 years were pooled in a meta-analysis, with each series weighted by its variance. Causes of failure were presented as a percentage of the pooled revisions.

Results

A total of 11 studies were identified, encompassing 3,129 cases. Across the 9 studies that had reported a mean follow-up, the mean follow-up was 11.7 years (range, 9.55 to 13.7 years). We found a pooled 10-year survival rate of 95.5% (95% confidence interval, 93.4% to 97.1%). There were 149 revisions among the studies (range, 4 to 38 revisions per study), a rate of 4.8% of the total procedures performed. The 2 main causes of revision were aseptic loosening (20.1% of revisions) and adverse reactions to metal debris (20.1%). There were no revisions for dislocation. Of the studies that reported preoperative functional scores, all reported significant improvement in mean scores postoperatively except for 1 study in which the mean Tegner activity score did not significantly improve.

Conclusions

When performed for appropriate indications, patients undergoing an HRA with use of the BIRMINGHAM HIP Resurfacing System can expect good implant survivorship at 10 years with acceptable functional results and low rates of dislocation and infection. This systematic review, however, confirms concerns regarding adverse reactions to metal debris as a leading cause of revision.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Birmingham hip resurfacing: a systematic review of outcomes at minimum 10-years follow-up

Although controversy surrounding the use of metal-on-metal (MoM) arthroplasty implants continues to exist, satisfactory clinical and radiological outcomes have been reported following Birmingham Hip Resurfacing (BHR) at long-term follow-up, leading to an Orthopaedic Data Evaluation Panel (ODEP) rating of 13A. The purpose of this study was to systematically review the literature to evaluate the functional outcomes, radiological outcomes and revision rates following BHR at a minimum of 10 years follow-up. Using the PRISMA guidelines, two independent reviewers performed a literature search using Pubmed, Embase and Scopus databases. Only studies reporting on outcomes of BHR with a minimum of 10 years' follow-up were considered for inclusion. A total of 12 studies including 7132 hips (64.8% males), with mean follow-up of 11.5 years (10-15.3), met our inclusion criteria. Of included patients, 94.3% of patient underwent BHR for osteoarthritis at a mean age was 52.0 years (48-52). At final follow-up, 96% of patients reported being satisfied with their BHR, with mean Harris Hip Scores of 93.6 and Oxford Hip Scores of 16.5. Rates of radiological femoral neck narrowing of greater than 10% and non-progressive radiological loosening were reported as 2.0% and 3.8% respectively. At final follow-up, the overall revision rate was 4.9% (334/7132), deep infection rate was 0.4%, metal allergy/insensitivity rate was 1.6%, metal reaction rate was 0.3%, rate of peri-prosthetic fracture was 0.9% and aseptic loosening rates were 1.6%. This systematic review demonstrates that BHR results in satisfactory clinical outcomes, acceptable implant survivorship, low complication rates and modest surgical revision rates in the long-term at minimum 10-year follow-up.

Hip Resurfacing Compared with 28-mm Metal-on-Metal Total Hip Replacement: A Randomized Study with 15 Years of Follow-up

BACKGROUND

Bone stock conservation, hip anatomy preservation, and greater stability are among the promoted advantages of hip resurfacing (HR). However, the disappointing failure of some implants nearly led to its abandonment. The aim of this study was to compare clinical scores and revision and complication rates after HR with those after total hip arthroplasty (THA).

METHODS

Two hundred and three hips were randomized to 28-mm metal-on-metal (MoM) THA (99 hips) or to HR (104 hips). Main outcome measures compared between groups were the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, the revision rate, and the complication rates. The radiographic findings were also assessed.

RESULTS

After a mean follow-up of 15 years (range, 14 to 16 years), 9 (4.4%) of the 203 patients were lost to follow-up and 15 (7.4%) had died. The Kaplan-Meier survivorship, with revision for any reason as the end point, was 89.2% (95% confidence interval [CI], 82.3% to 96.1%) for HR and 94.2% (95% CI, 89.3% to 99.1%) for THA (p = 0.292). The reasons for revision included infection (3 patients), recurrent dislocation (1 patient), and adverse reaction to metal debris (ARMD) (1 patient) in the THA group and ARMD (2 patients) and femoral head loosening (7 patients) in the HR group. With aseptic revision as the end point, the Kaplan-Meier survivorship was significantly higher in the THA group (97.4% versus 89.2%; p = 0.033). No dislocation occurred in the HR group compared with 4 in the THA group (p = 0.058). Both groups achieved a similar mean WOMAC score (10.7 in the HR group and 8.8 in the THA group; p = 0.749), Forgotten Joint Score (87.1 and 85.3, respectively; p = 0.410), University of California Los Angeles (UCLA) activity score (6.3 and 6.4, respectively; p = 0.189), and overall joint perception (p = 0.251).

CONCLUSIONS

The specific HR and MoM 28-mm THA implants used in this study showed good long-term survival and function. The overall rates of complications and revisions were similar in both groups but were of different types. As it provides better femoral bone preservation and biomechanical reconstruction, HR may continue to have a role in selected patients when performed by experienced surgeons and using validated implants.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Hip Replacement or Hip Resurfacing with a Highly Cross-Linked Polyethylene Acetabular Bearing: A Qualitative and Quantitative Preference Study

Background

Most surgeons strongly prefer total hip arthroplasty (THA) over hip resurfacing arthroplasty (HRA). However, it is unknown whether patients prefer the results of 1 procedure over the other. The purpose of this study was to answer 3 questions: (1) Do patients with an HRA on 1 side and a THA on the other notice a difference? (2) Do patients have a preference? (3) What are the reasons for their preference?

Methods

Between 1998 and 2012, 332 patients underwent staged bilateral hip arthroplasties with cementless THA on 1 side and HRA on the other, with a highly cross-linked polyethylene acetabular component used for both. Patient preferences, Harris hip scores, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were recorded by blinded examiners. Patients provided reasons for their preference in semi-structured interviews using both quantitative and qualitative measures.

Results

The mean follow-up was 11 years (range, 7 to 21 years). Of 324 patients with complete data, 279 (86%) preferred the HRA, 19 (6%) preferred the THA, and 26 (8%) had no preference. The most common reasons for preference for the HRA were better balance (n = 143), felt more normal (n = 141), better activity participation/more reliable hip during sports (n = 139), and stronger on stairs (n = 129). A fair or poor outcome was reported by the patient after 4 HRAs and 7 THAs. The remainder of the patients reported improved function and satisfactory pain relief and range of motion for both hips.

Conclusions

In conclusion, most patients in this study preferred the side on which the HRA had been done. Since essentially all current hip prostheses perform well, a paired bilateral study may be the optimal way to determine patient preferences and values of HRA compared with THA.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Hip resurfacing with a highly cross-linked polyethylene acetabular liner and a titanium nitride-coated femoral component

AIMS

This study evaluated a specific hip resurfacing system to determine the: (1) function and complications, (2) implant survivorship, (3) acetabular bone conservation and joint biomechanics and (4) osteolysis and polyethylene wear.

METHODS

I performed 234 resurfacing procedures (192 patients) using a two-piece titanium acetabular component with a 4 mm highly cross-linked polyethylene liner and a cementless titanium nitride-coated titanium femoral component. Function was assessed with Harris Hip, WOMAC, SF-12, and UCLA scores. Radiography and CT scans were used to evaluate bone retention, component position, joint biomechanics, and osteolysis. Retrieved polyethylene liners were analyzed for wear.

RESULTS

Median follow-up was 8 years and patients averaged 48 years of age at surgery. The mean Harris Hip Score was 96 and all scores improved significantly. Kaplan-Meier survivorship was 97%. The mean medial acetabular thickness was 9 mm postoperatively versus 14 mm preoperatively ( p = 0.019). Femoral bone conservation (head:neck ratio) was 1.36 postoperatively versus 1.42 preoperatively ( p = 0.02). There was no polyethylene wear through or osteolysis. Eight polyethylene retrievals had a mean wear of 0.05 mm/yr.

CONCLUSIONS

Resurfacing with a highly cross-linked polyethylene acetabular component and a titanium nitride-coated titanium cementless femoral component is a reliable and bone-conserving procedure at mid-term.

Femoral offset found not to affect metal ion levels in metal-on-metal total hip arthroplasty

BACKGROUND

Failure to restore femoral offset in metal on polyethylene total hip arthroplasty (THA) causes polyethylene wear and aseptic loosening. To our knowledge, no study to date has investigated the relationship between femoral offset and wear in metal-on-metal (MOM) THA.

AIMS

In this study, we investigated the relationship between femoral offset and wear by measuring circulating metal ion levels in MOM THA.

METHODS

In this retrospective study, we identified patients who had undergone MOM THA with the ASR XL system (DePuy International Ltd., Leeds, UK). Femoral offset was measured using anteroposterior radiographs, and circulating metal ion levels (cobalt and chromium) were recorded.

RESULTS

In total, 95 patients were included (68 males and 27 females). The mean age at the time of surgery was 64.9. Mean time from surgery to blood sampling was 15.4 months. No statistically significant relationship was found between femoral offset and cobalt (p = 0.313) or chromium (p = 0.401) ions.

CONCLUSION

It is known that failure to restore femoral offset during THA can lead to high rates of wear in metal-on-polyethylene articulations. In our study, no statistically significant relationship was found between femoral offset and serum cobalt or chromium ions. This study adds to the information available to surgeons regarding factors that increase wear in metal-on-metal total hip arthroplasty.

Comparison of hip function and quality of life of total hip arthroplasty and resurfacing arthroplasty in the treatment of young patients with arthritis of the hip joint at 5 years

OBJECTIVE

To compare the medium-term clinical effectiveness of total hip arthroplasty and resurfacing arthroplasty.

DESIGN

Single centre, two-arm, parallel group, assessor blinded, randomised controlled trial with 1:1 treatment allocation.

SETTING

A large teaching hospital in England.

PARTICIPANTS

122 patients older than 18 years with severe arthritis of the hip joint, suitable for resurfacing arthroplasty of the hip. Patients were excluded if they were considered to be unable to adhere to trial procedures or complete questionnaires.

INTERVENTIONS

Total hip arthroplasty (replacement of entire femoral head and neck); hip resurfacing arthroplasty (replacement of the articular surface of femoral head only, femoral neck remains intact). Both procedures replaced the articular surface of the acetabulum.

OUTCOMES

The outcome measures were hip function assessed using the Oxford Hip Score (OHS) and health-related quality of life assessed using the EuroQol (EQ-5D). Patients were followed up annually for a minimum of 5 years. Outcome data were modelled using the generalised estimating equation methodology to explore temporal variations during follow-up.

RESULTS

60 patients were randomly assigned to hip resurfacing arthroplasty and 62 to total hip arthroplasty. 95 (78%) of the 122 original study participants provided data at 5 years. There was a small decrease in both hip functions and quality of life in both groups of patients each year during the 5-year follow-up period. However, there was no evidence of a significant difference between treatments group in the OHS (P=0.333) or the EQ-5D (P=0.501).

CONCLUSIONS

We previously reported no difference in outcome in the first year after surgery. The current medium-term results also show no evidence of a difference in hip function or health-related quality of life in the 5 years following a total hip arthroplasty versus resurfacing arthroplasty.

TRIAL REGISTRATION NUMBER

ISRCTN33354155. UKCRN 4093.

Hip prostheses in young adults. Surface prostheses and short-stem prostheses

The poor results obtained in young patients when using a conventional prosthesis led to the resurgence of hip resurfacing to find less invasive implants for the bone. Young patients present a demand for additional activity, which makes them a serious challenge for the survival of implants. In addition, new information technologies contribute decisively to the preference for non-cemented prostheses. Maintaining quality of life, preserving the bone and soft tissues, as well as achieving a very stable implant, are the goals of every hip orthopaedic surgeon for these patients. The results in research point to the use of smaller prostheses, which use the metaphyseal zone more and less the diaphyseal zone, and hence the large number of the abovementioned short stem prostheses. Both models are principally indicated in the young adult. Their revision should be a more simple operation, but this is only true for hip resurfacing, not for short stems.

Effect of Femoral Stem Modular Neck's Material on Metal Ion Release

Background:

In recent decades, the popularity of modular necks in total hip arthroplasty (THA) has increased since modular necks offer the potential to restore the patient’s native anatomy, and thus improve stability. Unfortunately, modular necks are associated with higher complication rates, including implant fracture and modular junction corrosion with adverse local tissue reaction to metal debris.

Objective:

The objective of this study was to determine the impact of modular neck material on titanium (Ti), chrome (Cr), and cobalt (Co) metal ion levels in patients who underwent a THA with Ti femoral stem, Ti or CrCo modular neck, and ceramic-on-ceramic (CoC) bearing.

Methods:

Whole blood Ti, Cr, and Co levels were compared at a minimum 1-year follow-up in 36 patients who underwent unilateral, primary CoC large-diameter head THA with Profemur^® Preserve modular femoral stems (MicroPort, Arlington, TX, USA).

Results:

Higher Co concentrations were observed in the CrCo modular neck group (0.46 versus 0.26 µg/l in the Ti neck group, P=0.004) and higher Ti concentrations were observed in the Ti modular neck group (1.98 vs 1.59 µg/l in the CrCo neck group, P=0.007). However, these differences were not clinically meaningful since the absolute values remained within what is considered the safe range of Ti, Cr, and Co ions in whole blood. No patients were re-operated or revised.

Conclusion:

Modular neck materials had an impact on whole blood metal ion levels but the concentrations measured remained within the safe range at 1-year follow-up. There were no indirect signs of modular junction corrosion with either CrCo or Ti femoral necks.

Robotic-arm assisted total hip arthroplasty results in smaller acetabular cup size in relation to the femoral head size: a matched-pair controlled study

PURPOSE

To compare the acetabular component size relative to the patient's native femoral head size between conventional THA (CTHA) approach and robotic-arm assisted THA (RTHA) to infer which of these techniques preserved more acetabular bone.

METHODS

Patients were included if they had primary osteoarthritis (OA) and underwent total hip replacement between June 2008 and March 2014. Patients were excluded if they had missing or rotated postoperative anteroposterior radiographs. RTHA patients were matched to a control group of CTHA patients, in terms of preoperative native femoral head size, age, gender, body mass index (BMI) and approach. Acetabular cup size relative to femoral head size was used as a surrogate for amount of bone resected. We compared the groups according to 2 measures describing acetabular cup diameter (c) in relation to femoral head diameter (f): (i) c-f, the difference between cup diameter and femoral head diameter and (ii) (c-f)/f, the same difference as a fraction of femoral head diameter.

RESULTS

57 matched pairs were included in each group. There were no significant differences between groups for demographic measures, femoral head diameter, or acetabular cup diameter (p>0.05). However, measures (i) and (ii) did differ significantly between the groups, with lower values in the RTHA group (p<0.02).

CONCLUSIONS

Using acetabular cup size relative to femoral head size as an approximate surrogate measure of acetabular bone resection may suggest greater preservation of bone stock using RTHA compared to CTHA. Further studies are needed to validate the relationship between acetabular cup size and bone loss in THA.

Osteonecrosis

Younger patients are affected more often by osteonecrosis than by osteoarthritis, and osteonecrosis has significantly greater long-term morbidity.

Corticosteroids are the most common cause of nontraumatic osteonecrosis.

The femoral head is the most common site of osteonecrosis.

In rare instances, osteonecrosis of the jaw has been associated with bisphosphonate exposure. This phenomenon is more common with repeated intravenous infusions of bisphosphonates.

Case reports of osteonecrosis of the jaw in association with other medications, such as denosumab, have been reported.

The final common pathway in the pathogenesis of osteonecrosis is disruption of blood supply to a segment of bone.

Abnormalities in lipid metabolism, bone homeostasis, regulation of apoptosis, coagulopathies, innate immunity, and oxidative stress may play a role in the pathogenesis of osteonecrosis.

Epigenetics may alter the predisposition to develop osteonecrosis.

MRI is currently the optimal test for early diagnosis and identification of the extent of osteonecrosis.

Nonsurgical treatment of osteonecrosis does not change the natural history of the disease.

Although surgical treatment of femoral head osteonecrosis has many variations, most symptomatic patients eventually require total hip arthroplasty.

Knowledge of risk factors and early detection are crucial to the successful management of osteonecrosis.

Because of the lack of successful treatment options, new modes of management focus on the prevention of osteonecrosis.

Hip Resurfacing Using Highly Cross-linked Polyethylene: Prospective Study Results at 8.5 Years

BACKGROUND

Hip resurfacing is an option to consider when treating younger, more active patients. Advantages over total hip arthroplasty include a more normal gait and a lower incidence of thigh pain.

METHODS

In this prospective study, 190 hip resurfacing procedures (164 participants) were performed using a cobalt-chromium femoral component and a cementless acetabular cup with a 3.8-mm highly cross-linked polyethylene acetabular liner.

RESULTS

The mean follow-up was 8.5 (range, 7-10) years. Two participants were lost to follow-up and 2 died. One participant underwent successful revision surgery for acetabular loosening. Four participants underwent successful revision to a total hip arthroplasty because of femoral neck fracture (2), femoral loosening, or infection. The Kaplan-Meier survivorship was 97%. Acetabular bone conservation was assessed using computed tomography by measuring the medial acetabular wall. The mean thickness was 9 mm. Femoral bone was well preserved with a mean head:neck ratio of 1.37. There were 4 (2%) osteolytic defects up to 0.9 cm(3) on computed tomography and no instances of impending polyethylene wear-through. Seven polyethylene retrievals had a measured wear rate of 0.05 mm/y.

CONCLUSION

Hip resurfacing using a highly cross-linked polyethylene acetabular component is a reliable procedure. Both femoral and acetabular bones are reasonably preserved compared with prior resurfacing methods. The low incidence of osteolysis and the low rate of wear found on retrievals suggest that many years of use in highly active patients is possible.

Increased risk for extended acetabular reconstruction in failed hip resurfacing as compared to failed total hip arthroplasty

INTRODUCTION

Hip resurfacing (HR) is intended to preserve the femoral bone stock during primary arthroplasty. On the other hand, little has been reported regarding the intraoperative need of bone reconstruction for extended acetabular defects during hip resurfacing revision. Thus, the aim of the presented study was to identify whether there is an increased need for acetabular bone reconstruction in HR revision surgery.

MATERIALS AND METHODS

We analyzed the data of 38 patients who underwent 39 conversions from a HR to a total hip arthroplasty (THA). Acetabular bone defects and the respective revision technique were compared against a temporary cohort of patients undergoing revision surgery of a conventional THA.

RESULTS

In 29 HR patients revision required either autogenous or allogenous impaction bone grafting to adequately manage acetabular host bone degradation. In 10 cases additional implantation of a reinforcement device was necessary. Compared to the THA cohort revision of failed HR is associated with a significantly increased risk of higher grade bone defects (Paprosky classification) and extended acetabular reconstruction (p < 0.05).

CONCLUSIONS

This study provides evidence that revision of failed HR devices is associated with an increased risk for extensive acetabular defects. Furthermore, the preoperative radiographic assessment of HR devices often underestimates the intraoperative acetabular defect. Surgeons should be aware of this fact not to technically underestimate HR revision procedures.

Total hip replacement and surface replacement for the treatment of pain and disability resulting from end-stage arthritis of the hip (review of technology appraisal guidance 2 and 44): systematic review and economic evaluation

BACKGROUND

Total hip replacement (THR) involves the replacement of a damaged hip joint with an artificial hip prosthesis. Resurfacing arthroplasty (RS) involves replacement of the joint surface of the femoral head with a metal surface covering.

OBJECTIVES

To undertake clinical effectiveness and cost-effectiveness analysis of different types of THR and RS for the treatment of pain and disability in people with end-stage arthritis of the hip, in particular to compare the clinical effectiveness and cost-effectiveness of (1) different types of primary THR and RS for people in whom both procedures are suitable and (2) different types of primary THR for people who are not suitable for hip RS.

DATA SOURCES

Electronic databases including MEDLINE, EMBASE, The Cochrane Library, Current Controlled Trials and UK Clinical Research Network (UKCRN) Portfolio Database were searched in December 2012, with searches limited to publications from 2008 and sample sizes of ≥ 100 participants. Reference lists and websites of manufacturers and professional organisations were also screened.

REVIEW METHODS

Systematic reviews of the literature were undertaken to appraise the clinical effectiveness and cost-effectiveness of different types of THR and RS for people with end-stage arthritis of the hip. Included randomised controlled trials (RCTs) and systematic reviews were data extracted and risk of bias and methodological quality were independently assessed by two reviewers using the Cochrane Collaboration risk of bias tool and the Assessment of Multiple Systematic Reviews (AMSTAR) tool. A Markov multistate model was developed for the economic evaluation of the technologies. Sensitivity analyses stratified by sex and controlled for age were carried out to assess the robustness of the results.

RESULTS

A total of 2469 records were screened of which 37 were included, representing 16 RCTs and eight systematic reviews. The mean post-THR Harris Hip Score measured at different follow-up times (from 6 months to 10 years) did not differ between THR groups, including between cross-linked polyethylene and traditional polyethylene cup liners (pooled mean difference 2.29, 95% confidence interval -0.88 to 5.45). Five systematic reviews reported evidence on different types of THR (cemented vs. cementless cup fixation and implant articulation materials) but these reviews were inconclusive. Eleven cost-effectiveness studies were included; four provided relevant cost and utility data for the model. Thirty registry studies were included, with no studies reporting better implant survival for RS than for all types of THR. For all analyses, mean costs for RS were higher than those for THR and mean quality-adjusted life-years (QALYs) were lower. The incremental cost-effectiveness ratio for RS was dominated by THR, that is, THR was cheaper and more effective than RS (for a lifetime horizon in the base-case analysis, the incremental cost of RS was £11,284 and the incremental QALYs were -0.0879). For all age and sex groups RS remained clearly dominated by THR. Cost-effectiveness acceptability curves showed that, for all patients, THR was almost 100% cost-effective at any willingness-to-pay level. There were age and sex differences in the populations with different types of THR and variations in revision rates (from 1.6% to 3.5% at 9 years). For the base-case analysis, for all age and sex groups and a lifetime horizon, mean costs for category E (cemented components with a polyethylene-on-ceramic articulation) were slightly lower and mean QALYs for category E were slightly higher than those for all other THR categories in both deterministic and probabilistic analyses. Hence, category E dominated the other four categories. Sensitivity analysis using an age- and sex-adjusted log-normal model demonstrated that, over a lifetime horizon and at a willingness-to-pay threshold of £20,000 per QALY, categories A and E were equally likely (50%) to be cost-effective.

LIMITATIONS

A large proportion of the included studies were inconclusive because of poor reporting, missing data, inconsistent results and/or great uncertainty in the treatment effect estimates. This warrants cautious interpretation of the findings. The evidence on complications was scarce, which may be because of the absence or rarity of these events or because of under-reporting. The poor reporting meant that it was not possible to explore contextual factors that might have influenced study results and also reduced the applicability of the findings to routine clinical practice in the UK. The scope of the review was limited to evidence published in English in 2008 or later, which could be interpreted as a weakness; however, systematic reviews would provide summary evidence for studies published before 2008.

CONCLUSIONS

Compared with THR, revision rates for RS were higher, mean costs for RS were higher and mean QALYs gained were lower; RS was dominated by THR. Similar results were obtained in the deterministic and probabilistic analyses and for all age and sex groups THR was almost 100% cost-effective at any willingness-to-pay level. Revision rates for all types of THR were low. Category A THR (cemented components with a polyethylene-on-metal articulation) was more cost-effective for older age groups. However, across all age-sex groups combined, the mean cost for category E THR (cemented components with a polyethylene-on-ceramic articulation) was slightly lower and the mean QALYs gained were slightly higher. Category E therefore dominated the other four categories. Certain types of THR appeared to confer some benefit, including larger femoral head sizes, use of a cemented cup, use of a cross-linked polyethylene cup liner and a ceramic-on-ceramic as opposed to a metal-on-polyethylene articulation. Further RCTs with long-term follow-up are needed.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013003924.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Comparison of Acetabular Bone Resection, Offset, Leg Length and Post Operative Function Between Hip Resurfacing Arthroplasty and Total Hip Arthroplasty

Controversy exists regarding the amount of acetabular bone resection, biomechanics and function of patients receiving either total hip arthroplasty (THA) or hip resurfacing arthroplasty (HRA). A cohort of patients undergoing 36 mm ceramic-on-ceramic THA (89) or metal-on-metal HRA (86) were compared. No difference was observed when the ratio of native femoral head size was compared to the implanted acetabular component size (1.15 ± 0.1 HRA c.f. 1.13 ± 0.1 THA). No difference was observed in acetabular offset, vertical centre of rotation or function (OHS mean 47 in both groups) but leg length discrepancy (1.8 mm c.f. 5.5 mm) and femoral offset did differ (0.6 mm c.f. 4.1 mm). This demonstrates that 36 mm ceramic-on-ceramic THA is not associated with more bone resection than HRA and achieves equivalent function whilst avoiding the problems of metal-on-metal bearings.

Metal ion levels and functional results following resurfacing hip arthroplasty versus conventional small-diameter metal-on-metal total hip arthroplasty; a 3 to 5year follow-up of a randomized controlled trial

We present an update of a randomized controlled trial on 71 patients (<65 years) who received either a resurfacing hip arthroplasty (RHA) (n=38) or cementless 28-mm metal-on-metal (MoM) total hip arthroplasty (THA) (n=33). Metal ion levels and functional outcome scores were analyzed with a mean follow-up of 58 months (SD 8.1). No clear shifts in relatively good outcome was encountered between RHA and THA. Metal ion levels appear to equalize between groups after 3 years. Median cobalt and chromium remained below 1.3 μg/L throughout follow-up in both groups. Six revisions were performed, of which three for pseudotumor formation (one THA, two RHA). In conclusion there were no clinical differences between the two groups and metal ion levels were lower than other series remained low, however, pseudotumor formation was not eliminated.

Metal-on-metal hip resurfacing compared with total hip arthroplasty: two to five year outcomes in men younger than sixty five years

PURPOSE

There are limited studies examining the long-term survivorship for the current generation of metal-on-metal hip resurfacing (MOMHR) implants in the young male population, and fewer studies have been published on prospectively collected outcomes data for total hip resurfacing in the USA. The purpose of this study was to demonstrate the efficacy of MOMHR in comparison with total hip arthroplasty (THA) using validated outcome measures, survivorship and complication rates.

METHODS

The study prospectively followed 136 implants in 123 male patients <65 years, all with a primary diagnosis of osteoarthritis and similar comorbidities as determined by the American Society of Anesthesiologists (ASA) score. A single-surgeon cohort of 89 MOMHRs was compared with a similar cohort of 47 THAs. Outcomes were prospectively assessed with the Short-Form Health Survey of 12 questions (SF-12) and Western Ontario and McMaster Universities (WOMAC) questionnaires pre- and postoperatively at yearly intervals. Minimum follow-up was two years, and average follow-up was 3.9 years.

RESULTS

Diagnosis, body mass index (BMI), American Association of Anesthesiologists (ASA) and pre-operative pain and function scores were not significantly different between groups. There was no difference in SF-12 scores postoperatively. At one and two years postoperatively, the MOMHR group had better WOMAC scores than the THA group, but no difference was seen at three to five years postoperatively. There were no revisions in either group over the study period.

CONCLUSIONS

This study demonstrated good results for hip resurfacing in men <65 years five years postoperatively and similar function to THA patients.

The effect of acetabular inclination on metal ion levels following metal-on-metal hip arthroplasty

Acetabular inclination angles have been suggested as a principal determinant of circulating metal ion levels in metal-on-metal hip arthroplasties. We aimed to determine whether inclination angle correlates with ion levels in arthroplasties using the Articular Surface Replacement (ASR) system. Patients undergoing ASR arthroplasties had blood metal ion levels and radiograph analysis performed a mean of 3.2 years after surgery. Inclination angle showed only a weak correlation with cobalt (r=0.21) and chromium (r=0.15) levels. The correlation between inclination angle and cobalt levels was significant only with small femoral components, although it was still weak. Multiple regression showed a complex interaction of factors influencing ion levels but inclination angle accounted for little of this variation. We conclude that the acetabular inclination angle is not a meaningful determinant of metal ion levels in ASR arthroplasties.

Metal-on-metal hip resurfacing compared with 28-mm diameter metal-on-metal total hip replacement: a randomised study with six to nine years' follow-up

A total of 219 hips in 192 patients aged between 18 and 65 years were randomised to 28-mm metal-on-metal uncemented total hip replacements (THRs, 107 hips) or hybrid hip resurfacing (HR, 112 hips). At a mean follow-up of eight years (6.6 to 9.3) there was no significant difference between the THR and HR groups regarding rate of revision (4.0% (4 of 99) vs 5.8% (6 of 104), p = 0.569) or re-operation rates without revision (5.1% (5 of 99) vs 2.9% (3 of 104), p = 0.428). In the THR group one recurrent dislocation, two late deep infections and one peri-prosthetic fracture required revision, whereas in the HR group five patients underwent revision for femoral head loosening and one for adverse reaction to metal debris. The mean University of California, Los Angeles activity scores were significantly higher in HR (7.5 (sd 1.7) vs 6.9 (sd 1.7), p = 0.035), but similar mean Western Ontario and McMaster Universities Osteoarthritis Index scores were obtained (5.8 (sd 9.5) in HR vs 5.1 (sd 8.9) in THR, p = 0.615) at the last follow-up. Osteolysis was found in 30 of 81 THR patients (37.4%), mostly in the proximal femur, compared with two of 83 HR patients (2.4%) (p < 0.001). At five years the mean metal ion levels were < 2.5 μg/l for cobalt and chromium in both groups; only titanium was significantly higher in the HR group (p = 0.001). Although revision rates and functional scores were similar in both groups at mid-term, long-term survival analysis is necessary to determine whether one procedure is more advantageous than the other.

Correlation between groin pain and cup design of hip-resurfacing implants: a prospective study

PURPOSE

Cup design has been incriminated as the source of groin pain after hip resurfacing but has not been well described; thus, it was assessed in a prospective study looking at three implant types.

METHODS

A group-match was done between three groups of hip resurfacing devices according to age, sex, body mass index, activity level, osteoarthritis aetiology and pre-operative scores.

RESULTS

The global groin pain rate was 5.7 % at six months and 2.7 % at last follow-up. Groin pain rate was significantly different between the three groups (p = 0.004) and had a strong influence on the subjective results (p = 0.04). No groin pain emerged between six months and last follow-up. No clinical differences were noted in Harris hip score and Merle d'Aubigné-Postel score at last follow-up. However, the Oxford hip score and Devane activity score were significantly lower for cups with macrostructures.

CONCLUSION

The low groin pain rate in this prospective cohort was probably secondary to the specific surgical technique used and seems to be correlated with cup design. Macrostructures on the external part of the cup could be significantly harmful.

Mortality rates at 10 years after metal-on-metal hip resurfacing compared with total hip replacement in England: retrospective cohort analysis of hospital episode statistics

OBJECTIVES

To compare 10 year mortality rates among patients undergoing metal-on-metal hip resurfacing and total hip replacement in England.

DESIGN

Retrospective cohort study.

SETTING

English hospital episode statistics database linked to mortality records from the Office for National Statistics.

POPULATION

All adults who underwent primary elective hip replacement for osteoarthritis from April 1999 to March 2012. The exposure of interest was prosthesis type: cemented total hip replacement, uncemented total hip replacement, and metal-on-metal hip resurfacing. Confounding variables included age, sex, Charlson comorbidity index, rurality, area deprivation, surgical volume, and year of operation.

MAIN OUTCOME MEASURES

All cause mortality. Propensity score matching was used to minimise confounding by indication. Kaplan-Meier plots estimated the probability of survival up to 10 years after surgery. Multilevel Cox regression modelling, stratified on matched sets, described the association between prosthesis type and time to death, accounting for variation across hospital trusts.

RESULTS

7437 patients undergoing metal-on-metal hip resurfacing were matched to 22,311 undergoing cemented total hip replacement; 8101 patients undergoing metal-on-metal hip resurfacing were matched to 24,303 undergoing uncemented total hip replacement. 10 year rates of cumulative mortality were 271 (3.6%) for metal-on-metal hip resurfacing versus 1363 (6.1%) for cemented total hip replacement, and 239 (3.0%) for metal-on-metal hip resurfacing versus 999 (4.1%) for uncemented total hip replacement. Patients undergoing metal-on-metal hip resurfacing had an increased survival probability (hazard ratio 0.51 (95% confidence interval 0.45 to 0.59) for cemented hip replacement; 0.55 (0.47 to 0.65) for uncemented hip replacement). There was no evidence for an interaction with age or sex.

CONCLUSIONS

Patients with hip osteoarthritis undergoing metal-on-metal hip resurfacing have reduced mortality in the long term compared with those undergoing cemented or uncemented total hip replacement. This difference persisted after extensive adjustment for confounding factors available in our data. The study results can be applied to matched populations, which exclude patients who are very old and have had complex total hip replacements. Although residual confounding is possible, the observed effect size is large. These findings require validation in external cohorts and randomised clinical trials.

A fatigue assessment technique for modular and pre-stressed orthopaedic implants

Orthopaedic implants experience large cyclic loads, and pre-clinical analysis is conducted to ensure they can withstand millions of loading cycles. Acetabular cup developments aim to reduce wall thickness to conserve bone, and this produces high pre-stress in modular implants. As part of an implant development process, we propose a technique for preclinical fatigue strength assessment of modular implants which accounts for this mean stress, stress concentrating features and material processing. A modular cup's stress distributions were predicted computationally, under assembly and in vivo loads, and its cyclic residual stress and stress amplitude were calculated. For verification against damage initiation in low-cycle-fatigue (LCF), the peak stress was compared to the material's yield strength. For verification against failure in high-cycle-fatigue (HCF) each element's reserve factor was calculated using the conservative Soderberg infinite life criterion. Results demonstrated the importance of accounting for mean stress. The cup was predicted to experience high cyclic mean stress with low magnitude stress amplitude: a low cyclic load ratio (Rl=0.1) produced a high cyclic stress ratio (Rs=0.80). Furthermore the locations of highest cyclic mean stress and stress amplitude did not coincide. The minimum predicted reserve factor Nf was 1.96 (HCF) and 2.08 (LCF). If mean stress were neglected or if the stress ratio were assumed to equal the load ratio, the reserve factor would be considerably lower, potentially leading to over-engineering, reducing bone conservation. Fatigue strength evaluation is only one step in a broader development process, which should involve a series of verifications with the full range of normal and traumatic physiological loading scenarios, with representative boundary conditions and a representative environment. This study presents and justifies a fatigue analysis methodology which could be applied in early stage development to a variety of modular and pre-stressed prosthesis concepts, and is particularly relevant as implant development aims to maximise modularity and bone conservation.

Cost-utility of metal-on-metal hip resurfacing compared to conventional total hip replacement in young active patients with osteoarthritis

BACKGROUND

Metal-on-metal hip resurfacing arthroplasty (MoM HRA) has emerged as an alternative to total hip arthroplasty (THA) for younger active patients with osteoarthritis (OA). Birmingham hip resurfacing is the most common MoM HRA in Alberta, and is therefore compared with conventional THA.

OBJECTIVE

The objective of this study was to estimate the expected cost-utility of MoM HRA versus THA, in younger patients with OA, using a decision analytic model with a 15-year time horizon.

METHODS

A probabilistic Markov decision analytic model was constructed to estimate the expected cost per quality-adjusted life-year (QALY) of MoM HRA versus THA from a health care payer perspective. The base case considered patients with OA aged 50 years; men comprised 65.9% of the cohort. Sensitivity analyses evaluated cohort age, utility values, failure probabilities, and treatment costs. Data were derived from the Hip Improvement Project and the Hip and Knee Replacement Pilot databases in Alberta, the 2010 National Joint Replacement Registry of the Australian Orthopaedic Association, and the literature.

RESULTS

In the base case, THA was dominated by MoM HRA (incremental mean costs of -$583 and incremental mean QALYs of 0.079). In subgroup analyses, THA remained dominated when cohort age was 40 years instead of 50 years or when only men were assessed. THA dominated when the cohort age was 60 years or when only women were assessed. Results were sensitive to utilities, surgery costs, and MoM HRA revision and conversion probabilities. At a willingness-to-pay of Can $50,000/QALY, there was a 58% probability that MoM HRA is cost-effective.

CONCLUSIONS

The results show that, on average, MoM HRA was preferred to THA for younger and male patients, but THA is still a reasonable option if the patient or clinician prefers given the small absolute differences between the options and the confidence ellipses around the cost-effectiveness estimates.

An initial experience with hip resurfacing versus cementless total hip arthroplasty

BACKGROUND

Hip resurfacing is an alternative to total hip arthroplasty.

QUESTIONS/PURPOSE

We aimed to compare an experienced hip surgeon's initial clinical results of hip resurfacing with a new cementless total hip arthroplasty (THA).

METHODS

The first 55 consecutive hip resurfacing arthroplasties were compared to 100 consecutive cementless THAs using a cylindrical tapered femoral stem. The learning curve between the two procedures was compared utilizing the incidence of reoperation, complications, Harris Hip Scores (HHS), and implant survivorship.

RESULTS

The reoperation rate was significantly higher (p = 0.019) for hip resurfacing (14.5%) versus THA (4%). The overall complication rate between the two groups was not significantly different (p = 0.398). Preoperative HHS were similar between the two groups (p = 0.2). The final mean HHS was similar in both the resurfacing and THA groups (96 vs. 98.3, respectively, p < 0.65). Kaplan-Meier survival analysis with an endpoint of reoperation suggests complications occurred earlier in the resurfacing group versus the THA group (log-rank test, p = 0.007).

CONCLUSIONS

In comparison to our initial experience with a cementless THA stem, operative complications occur earlier and more often after hip resurfacing during the learning period. The clinical outcomes in both groups however are similar at 5 year follow-up.

Hip resurfacing and conventional THA: comparison of acetabular bone stock removal, leg length, and offset

The purpose of this study was to compare total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) with regard to the amount of acetabular bone stock removed and the ability to restore leg length and offset. Anteroposterior pelvis radiographs of 153 consecutive THAs and 84 consecutive HRAs were compared. Excluded patients were those with prior hip surgery, those in which a best-fit circle could not be adequately matched to the femoral head, and those with preoperative radiographic findings that precluded consideration for HRA (ie, disease severity, deformity, leg-length discrepancy). A significant difference was found between THA and HRA with regards to age and sex but not primary diagnosis. Relative differences in acetabular bone removal were compared using a ratio of acetabular implant diameter to preoperative ipsilateral femoral head diameter measured with a best-fit circle. The ratio of acetabular cup diameter to preoperative ipsilateral femoral head diameter was significantly greater following THA than following HRA, indicating relatively more acetabular bone removal in THA procedures. Mean leg-length discrepancy was significantly greater following THA than following HRA. Offset was increased to a greater extent following THA than following HRA. Overall, HRA was associated with relatively less acetabular bone stock removal and less alteration in leg length and offset than was THA.

Durom hip resurfacing system: retrospective study of 644 cases with an average follow-up of 34 months

INTRODUCTION

The performance of second-generation metal-on-metal bearings has led to the reintroduction of hip resurfacing. The goal of this multicentre study was to evaluate the short-term radiological and clinical outcomes with the Durom hip resurfacing system.

HYPOTHESIS

The Durom hip-resurfacing system will have similar results to other hip resurfacing systems and traditional hip arthroplasty implants.

MATERIALS AND METHODS

In the four participating centers, 580 patients (406 men, 174 women) and 644 hips were included. The average patient age was 48 years (range 16-77). A posterolateral surgical approach was used in 357 cases; a Hardinge-type approach was used in 182 cases and a Rottinger-type approach in 105.

RESULTS

After an average follow-up of 34 months, 31 hips (4.8%) had been revised. The reasons for revision were the following: 10 (1.6%) neck fracture (seven with Rottinger operative approach, one with Hardinge approach and one with posterolateral approach); 12 (1.9%) femoral loosening (four with lateral approach and eight with posterolateral approach); four (0.6%) acetabular cup migration; three (0.5%) unexplained pain; one (0.2%) adverse reaction to metal debris; one (0.2%) infection. Four hips (0.6%) dislocated but without recurrence - all were operated using the Hardinge approach. The 613 hips that were not operated on again had satisfactory clinical results; the Merle d'Aubigné score was 17.2 (range 12-18) and the WOMAC score was 91 (range 20-100). The five-year survival rate was 91% (95% CI: 87-94%). Based on radiographs, the average cup inclination was 44.4° (range 30 to 70°). The femoral offset was reduced by an average of 2.4mm (-31 to 23 mm) and the leg length had increased by an average of 0.8mm (-15 to 19 mm) relative to the other side, which was prosthesis-free. None of the non-revised implants showed any signs of loosening.

DISCUSSION

This multicentre evaluation revealed that the Durom revision rate was slightly higher than the rate with other hip resurfacing systems and traditional total hip arthroplasty. Although the Durom system displayed excellent tribological performance, the differences relative to other implants may be attributed to the challenges associated with impaction, related to the geometry and design of the cup, and to precarious primary fixation. The choice of surgical exposure and implantation technique was an important factor in the survival of the implant.

LEVEL OF PROOF

Level IV - Retrospective study.

Strict component positioning is necessary in hip resurfacing

BACKGROUND

Hip resurfacing arthroplasty has some advantages, including improved metal-on-metal articulation, a lower dislocation rate and preserved femoral bone. This procedure is a surgical option for younger and more active patients with osteoarthritis and osteonecrosis of the femoral head. Although there have been some reports about the efficacy of this technique, others report serious complications caused by metal debris. Additionally, femoral neck preservation adversely decreases the head-neck ratio and results in postoperative impingement.

METHODS

We evaluated the range of motion after hip resurfacing with various component orientations and optimal component orientations to avoid postoperative impingement using computer simulations in 10 male patients with osteonecrosis.

RESULTS

The mean ranges of motion in flexion, extension, abduction, adduction and internal rotation at 90° of flexion were 92.4° ± 13.8°, 25.7° ± 13.8°, 38.0° ± 11.1°, 29.1° ± 10.0° and 20.9° ± 11.5°, respectively. The oscillation angle in flexion and extension motion was 118.1° ± 10.3°. More than 100° of flexion was acquired in 79 of 240 simulations (32.9 %), and more than 20° extension was acquired in 142 simulations (59.2 %). Combined anteversion was significantly correlated with maximal flexion and extension angles. The component safe zone to fulfill the range of motion criteria varied among patients, and 4 of 10 patients had no safe zone.

CONCLUSIONS

Postoperative impingement occurs relatively frequently in hip resurfacing because of preservation of the femoral neck and component malpositioning. The safe zone of the acetabular component to avoid postoperative impingement is very narrow. Greater care should be taken regarding patient selection, rigorous preoperative planning and accurate component positioning.

Short-term functional outcome after hip resurfacing surgery

Hip resurfacing arthroplasty is a popular method for treating late stage osteoarthritis, especially in young and active patients. Most studies presenting short-term follow-up after hip resurfacing present radiographic or dual clinician-patient-related outcome. These kinds of outcomes are influenced by interpretation of the clinician and do not tell us much about functional outcome from the patients perspective. Today, functional outcome is often measured using patient-reported outcome instruments. We used the patient-reported 'Hip Disability and osteoarthritis Outcome Score' questionnaire, which has good measurement properties, to assess short-term functional outcome in 160 patients (mean follow-up of 2.6 years) after hip resurfacing surgery. Furthermore, we focused on pain, range of motion, subjective improvement and complications. The majority (86.9%) of patients was free of pain after surgery and range of motion improved significantly. Subjective improvement was indicated in 95% of the patients. Mean HOOS in 149 patients was 87.5. In total, there were 11 complications (6%), and deep infections contributed the most (3.4%). In general, short-term follow-up after hip resurfacing in this cohort showed good clinical and patient-reported functional outcome. When assessing the results of medical interventions, a good PRO instrument can give reliable and valuable information from the patients perspective.

Osteonecrosis

Osteonecrosis affects younger patients more often than osteoarthritis and has significantly greater long-term morbidity.

Corticosteroids constitute the most common cause of nontraumatic osteonecrosis.

The femoral head is the most common site of osteonecrosis.

Bisphosphonate use is associated with osteonecrosis of the jaw.

The final common pathway in the pathogenesis of osteonecrosis is disruption of blood supply to a segment of bone.

Abnormalities in lipid metabolism, bone homeostasis, regulation of apoptosis, coagulopathies, and oxidative stress may play a role in the pathogenesis of osteonecrosis.

Magnetic resonance imaging is currently the optimal test for early diagnosis and identification of the extent of osteonecrosis.

Nonsurgical treatment of osteonecrosis does not change the natural history of the disease.

Although there are many variations on surgical treatment of femoral head osteonecrosis, most patients eventually require total hip arthroplasty.

Knowledge of risk factors and early detection are crucial to the successful management of osteonecrosis.

Due to the lack of successful treatment options, new modes focus on prevention of osteonecrosis.

Failure rates of metal-on-metal hip resurfacings: analysis of data from the National Joint Registry for England and Wales

BACKGROUND

Implant survival after conventional total hip replacement (THR) is often poor in younger patients, so alternatives such as hip resurfacing, with various sizes to fit over the femoral head, have been explored. We assessed the survival of different sizes of metal-on-metal resurfacing in men and women, and compared this survival with those for conventional stemmed THRs.

METHODS

We analysed the National Joint Registry for England and Wales (NJR) for primary THRs undertaken between 2003 and 2011. Our analysis involved multivariable flexible parametric survival models to estimate the covariate-adjusted cumulative incidence of revision adjusting for the competing risk of death.

FINDINGS

The registry included 434,560 primary THRs, of which 31,932 were resurfacings. In women, resurfacing resulted in worse implant survival than did conventional THR irrespective of head size. Predicted 5-year revision rates in 55-year-old women were 8·3% (95% CI 7·2-9·7) with a 42 mm resurfacing head, 6·1% (5·3-7·0) with a 46 mm resurfacing head, and 1·5% (0·8-2·6) with a 28 mm cemented metal-on-polyethylene stemmed THR. In men with smaller femoral heads, resurfacing resulted in poor implant survival. Predicted 5-year revision rates in 55-year-old men were 4·1% (3·3-4·9) with a 46 mm resurfacing head, 2·6% (2·2-3·1) with a 54 mm resurfacing head, and 1·9% (1·5-2·4) with a 28 mm cemented metal-on-polyethylene stemmed THR. Of male resurfacing patients, only 23% (5085 of 22076) had head sizes of 54 mm or above.

INTERPRETATION

Hip resurfacing only resulted in similar implant survivorship to other surgical options in men with large femoral heads, and inferior implant survivorship in other patients, particularly women. We recommend that resurfacing is not undertaken in women and that preoperative measurement is used to assess suitability in men. Before further new implant technology is introduced we need to learn the lessons from resurfacing and metal-on-metal bearings.

FUNDING

National Joint Registry for England and Wales.

The removal of acetabular bone in hip resurfacing and cementless total hip replacement

The purpose of this study was to compare the amount of acetabular bone removed during hip resurfacing (HR) and cementless total hip replacement (THR), after controlling for the diameter of the patient’s native femoral head. Based on a power analysis, 64 consecutive patients (68 hips) undergoing HR or THR were prospectively enrolled in the study. The following data were recorded intra-operatively: the diameter of the native femoral head, the largest reamer used, the final size of the acetabular component, the size of the prosthetic femoral head and whether a decision was made to increase the size of the acetabular component in order to accommodate a larger prosthetic femoral head. Results were compared using two-sided, independent samples Student’s t-tests. A statistically significant difference was seen in the mean ratio of the size of the acetabular component to the diameter of the native femoral head (HR: 1.05 (sd 0.04) versus THR: 1.09 (sd 0.05); p <  0.001) and largest acetabular reamer used to the diameter of the native femoral head (HR: 1.03 (sd 0.04) versus THR: 1.09 (sd 0.05); p < 0.001). The ratios varied minimally when the groups were subdivided by gender, age and obesity. The decision to increase the size of the acetabular component to accommodate a larger femoral head occurred more often in the THR group (27% versus 9%). Despite the emphasis on avoiding damage to the femoral neck during HR, the ratio of the size of the acetabular component to the diameter of the native femoral head was larger in cementless THR than in HR.

Hip resurfacing: a 40-year perspective

BACKGROUND

Saving bone by resurfacing the femoral head is not a new concept and the appeal for this type of hip replacement has remained despite the difficulties to find a bearing material suitable for this procedure.

PURPOSE

In this article, the unique experience of a surgeon who has been performing hip resurfacing since its early development is presented, along with a comparative analysis of the performance of successive designs.

RESULTS

The overall 10-year Kaplan-Meier survivorship of the early designs with polyethylene bearings did not exceed 62% while that of the current Conserve®Plus metal-on-metal hybrid design implanted with second generation surgical technique is in excess of 92%. Further exceptional, in the 10-year survivorship, 99.7% has been achieved with femoral size of 46 mm and good bone quality. Cementless acetabular components provide better enduring fixation than cemented designs.

DISCUSSION

Metal-on-metal is currently and fortunately the only highly successful bearing material that can combine low wear rates and the manufacturing of a thin acetabular component to preserve bone and still accommodate the large femoral head of a hip resurfacing. The adverse local tissue reactions (ALTR) associated with metal-on-metal devices are not a bearing material issue per se but one of the device design and surgical technique. Almost all of ALTR and the rare events of systemic toxicity are due to abnormal wear patterns which can be prevented by proper acetabular component design and precise socket orientation in both the coronal and sagittal planes. Further improvements of the long-term durability with hip resurfacing can be anticipated with the use of recently developed trabecular bone-like tantalum or titanium porous coatings and with proper training of the surgeons interested in performing hip resurfacing arthroplasty.

Resurfacing arthroplasty for hip dysplasia: a prospective randomised study

In this prospective study a total of 80 consecutive Chinese patients with Crowe type I or II developmental dysplasia of the hip were randomly assigned for hip resurfacing arthroplasty (HRA) or total hip replacement (THR). Three patients assigned to HRA were converted to THR, and three HRA patients and two THR patients were lost to follow-up. This left a total of 34 patients (37 hips) who underwent HRA and 38 (39 hips) who underwent THR. The mean follow-up was 59.4 months (52 to 70) in the HRA group and 60.6 months (50 to 72) in the THR group. There was no failure of the prosthesis in either group. Flexion of the hip was significantly better after HRA, but there was no difference in the mean post-operative Harris hip scores between the groups. The mean size of the acetabular component in the HRA group was significantly larger than in the THR group (49.5 mm vs 46.1 mm, p = 0.001). There was no difference in the mean abduction angle of the acetabular component between the two groups. Although the patients in this series had risk factors for failure after HRA, such as low body weight, small femoral heads and dysplasia, the clinical results of resurfacing in those with Crowe type I or II hip dysplasia were satisfactory. Patients in the HRA group had a better range of movement, although neck-cup impingement was observed. However, more acetabular bone was sacrificed in HRA patients, and it is unclear whether this will have an adverse effect in the long term.

Hip resurfacing in patients under thirty years old: an attractive option for young and active patients

PURPOSE

Metal-on-metal hip resurfacing is offered as an alternative to traditional hip arthroplasty for young, active adults with advanced osteoarthritis. The concept of hip resurfacing is considered very attractive for this specific population (hard-on-hard bearing component with a large femoral head limiting the risk of dislocation, and allowing femoral bone stock preservation).

METHODS

A prospective clinical trial was designed to investigate the outcome of hip resurfacing in young patients (under 30 years old). We studied 24 hips in 22 patients. Mean age at operation was 24.9 years (range 17.1-29.9). No patient was lost to follow-up.

RESULTS

There was no revision at average follow-up of 50.6 months (44-59). Mean UCLA activity score improved from 5.5 (1-9) pre-operatively to 7.6 (1-10) postoperatively (p < 0.001). Mean Harris hip score increased from 43.9 (19-67) to 89.3 (55-100) (p < 0.001). Radiological analysis discerned no osteolysis and no implant migration.

CONCLUSION

The absence of short-term complications, such as mechanical failure or dislocation, is encouraging and leads us to think that mid-term results will be satisfactory. Moreover, the specific advantages of hip resurfacing (bone stock preservation, excellent stability, low risk of dislocation, large-diameter head) make the procedure a very attractive option for young subjects.

Total hip arthroplasty versus resurfacing arthroplasty in the treatment of patients with arthritis of the hip joint: single centre, parallel group, assessor blinded, randomised controlled trial

OBJECTIVES

To compare the clinical and cost effectiveness of total hip arthroplasty with resurfacing arthroplasty in patients with severe arthritis of the hip.

DESIGN

Single centre, two arm, parallel group, assessor blinded, randomised controlled trial with 1:1 treatment allocation.

SETTING

One large teaching hospital in the United Kingdom.

PARTICIPANTS

126 patients older than 18 years with severe arthritis of the hip joint, suitable for resurfacing arthroplasty of the hip. Patients were excluded if they were considered to be unable to adhere to trial procedures or complete questionnaires.

INTERVENTIONS

Total hip arthroplasty (replacement of entire femoral head and neck); hip resurfacing arthroplasty (replacement of the articular surface of femoral head only, femoral neck remains intact). Both procedures replaced the articular surface of the acetabulum.

MAIN OUTCOME MEASURES

Hip function at 12 months after surgery, assessed using the Oxford hip score and Harris hip score. Secondary outcomes were quality of life, disability rating, physical activity level, complications, and cost effectiveness.

RESULTS

60 patients were randomly assigned to hip resurfacing arthroplasty and 66 to total hip arthroplasty. Intention to treat analysis showed no evidence for a difference in hip function between treatment groups at 12 months (t test, P=0.242 and P=0.070 for Oxford hip score and Harris hip score, respectively); 95% of follow-up data was available for analysis. Mean Oxford hip score was 40.4 (95% confidence interval 37.9 to 42.9) in the resurfacing group and 38.2 (35.3 to 41.0) in the total arthroplasty group (estimated treatment effect size 2.23 (-1.52 to 5.98)). Mean Harris hip score was 88.4 (84.4 to 92.4) in the resurfacing group and 82.3 (77.2 to 87.5) in the total arthroplasty group (6.04 (-0.51 to 12.58)). Although we saw no evidence of a difference, we cannot definitively exclude clinically meaningful differences in hip function in the short term. Overall complication rates did not differ between treatment groups (P=0.291). However, we saw more wound complications in the total arthroplasty group (P=0.056) and more thromboembolic events in the resurfacing group (P=0.049).

CONCLUSIONS

No evidence of a difference in hip function was seen in patients with severe arthritis of the hip, one year after receiving a total hip arthroplasty versus resurfacing arthroplasty. The long term effects of these interventions remain uncertain.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN33354155, UKCRN 4093.

Femoral neck narrowing following hip resurfacing using posterior and Ganz approaches at two years

We report a retrospective review of femoral head/neck ratios on post-operative and two year follow-up radiographs following hip resurfacing arthroplasty. The patients were in two matched groups, having had surgery through a posterior approach or via a Ganz trochanteric flip. There was no significant difference in femoral neck narrowing at follow up between the two surgical approaches. However, we found significant narrowing of the femoral neck in both groups by the time of the two year follow-up radiograph.

Surface replacement of the hip can result in decreased acetabular bone stock

BACKGROUND

The recent interest in hip resurfacing arthroplasty is motivated by its potential advantages over THA. One advantage of hip resurfacing arthroplasty is that it conserves bone on the femoral side; however, it is unclear whether it does so on the acetabular side.

QUESTIONS/PURPOSES

We determined whether the amount of acetabular reaming and acetabular bone removal required for hip resurfacing arthroplasty is equal to, less than, or greater than that for THA.

PATIENTS AND METHODS

We prospectively evaluated the femoral neck size of 180 hips at the time of primary THA in an identical manner to when carrying out a hip resurfacing arthroplasty. Based on the femoral neck measurement, we determined the minimum cup size that would be used and reamer size required if the hip was undergoing a resurfacing. We compared this to the reamer size actually required to prepare the acetabulum for the THA cup. We calculated the difference between the predicted reaming size for resurfacing and the actual reaming size to determine the effect of resurfacing on acetabular bone stock.

RESULTS

Overall, 71%, 57%, and 41% of THAs would have had extra acetabular bone removed to implant a hip resurfacing arthroplasty cup with a line-to-line (0-mm), 1-mm, or 2-mm press fit, respectively.

CONCLUSIONS

When compared to THA, hip resurfacing arthroplasty commonly results in additional acetabular bone resection.

Femoral head to neck offset after hip resurfacing is critical for range of motion

BACKGROUND

Range of motion after hip arthroplasty may be limited by soft tissues around the hip, extra-articular contact and femoral stem-neck contact with the acetabular articular surface. Femoral head-neck diameter ratio is recognized as a major factor influencing hip range of motion. In hip resurfacing, range of motion is constrained by "cup component to femoral neck" contact. To avoid cup-to-bone contact or to increase the degree of flexion at which it occurs, anterior translation of the femoral component relative to the central femoral neck axis may improve anterior head-neck offset and hip flexion. We questioned whether low or high anterior femoral head to neck offset, cup inclination, stem anteversion, and component size influenced postoperative range of motion and hip flexion in patients who had undergone hip resurfacing.

METHODS

We prospectively followed 66 patients (68 hips) who underwent hip resurfacing at a mean age at operation of 46.4 years (range, 19-60 years). Mean follow-up was 37.5 months (range, 33-41 months). No patient was lost to follow-up. All patients were evaluated clinically and range of motion was precised. Radiological measurement evaluated the anterior femoral head-neck offset.

FINDINGS

Mean anterior neck-head offset was 7.5mm (range, 5-12 mm). We found significant linear regression correlation between anterior offset and flexion (R=0.66) and between anterior offset and global range of motion (R=0.51). One millimeter of anterior offset increased hip range of motion by 5° in flexion. No significant correlations were found between global range of motion or flexion arc of motion and component size, stem anteversion, cup inclination, gender ratio, preoperative arc of flexion or global range of motion.

INTERPRETATION

Restoring or improving deficient anterior femoral head-neck offset appears important for restoring postoperative range of motion and specifically hip flexion.

Supra acetabular bone mineral density measurements after hip resurfacing arthroplasty at short term follow up

Implantation of a cementless press-fit acetabular cup during hip arthroplasty alters stress transfer to the periacetabular bone, resulting in stress shielding of cancellous bone and enhanced load transfer to cortical bone. Theoretically, the thicker, stiffer and larger acetabular cup of a hip resurfacing may increase periacetabular bone stress shielding. We attempted to assess the matter (at a minimum of 2 years after surgery) by measuring any difference in supra acetabular bone mineral density (BMD) between the side implanted with a thick monoblock cobalt-chromium (Co-Cr) acetabular component during hip resurfacing (HR) and the opposite non-operated side. We retrospectively recruited 44 patients who had undergone metal-on-metal hybrid hip resurfacing for unilateral osteoarthritis of the hip joint . BMD of the supra acetabular bone of both hips was measured using a dual energy X-ray absorptiometry (DEXA) scan. The BMD measured in Zone 2 was not different on the operated side (1.69 g/cm2 ± 0.48) compared with the non-operated side (1.70 g/cm2 ±0.49) (p=0.904). Contrary to our expectations, implantation of a monoblock Co-Cr acetabular component during HR did not cause significant stress-shielding of supra acetabular cancellous bone.

Are leg length and hip offset comparable after hip resurfacing and cementless total hip arthroplasty?

INTRODUCTION

The purpose of this study was to determine if hip resurfacing arthroplasty (HRA) and cementless total hip arthroplasty (THA) were comparable in correcting leg length and hip offset in patients with primary osteoarthritis.

METHODS

A retrospective analysis was performed of 80 patients who underwent either HRA or cementless THA for primary osteoarthritis (40 in each group) between 2006 and 2008. Standardised anteroposterior radiographs taken pre-operatively and at one year following surgery were used to calculate the total offset and leg length in both hips.

RESULTS

At one year following surgery, no leg length discrepancy was identified in either group. A difference of 0.39 cm (p=0.046) remained between the mean total offset of the operated hip and the contralateral non-operated hip in the HRA group. No difference in offset was observed between the two hips after surgery in the THA group (p=0.875).

CONCLUSIONS

Leg length is restored by HRA and THA. A difference remains in offset after HRA although we attribute this to intentional medialisation of the acetabular cup.

Design and primary application of computer-assisted, patient-specific navigational templates in metal-on-metal hip resurfacing arthroplasty

Total hip resurfacing arthroplasty is increasingly being used. One of its goals is to closely mimic the normal anatomy and normal biomechanics of the hip joint. Prosthesis location has a large impact on implant survival and patient function; but in conventional hip resurfacing arthroplasty, precise positioning sometimes cannot be achieved. We describe a novel method for ensuring accurate prosthesis implantation in hip resurfacing arthroplasty by means of 3-dimensional reconstruction and reverse engineering.

State of the art in hard-on-hard bearings: how did we get here and what have we achieved?

Total hip arthroplasty has shown excellent results in decreasing pain and improving function in patients with degenerative disease of the hip. Improvements in prosthetic materials, designs and implant fixation have now resulted in wear of the bearing surface being the limitation of this technology, and a number of hard-on-hard couples have been introduced to address this concern. The purpose of this article is to review the origins, development, survival rates and potential advantages and disadvantages of the following hard-on-hard bearings for total hip arthroplasty: metal-on-metal standard total hip arthroplasty; metal-on-metal hip resurfacing arthroplasty, ceramic-on-ceramic total hip arthroplasty; and ceramic-on-metal bearings. Improvements in the manufacturing of metal-on-metal bearings over the past 50 years have resulted in implants that provide low wear rates and allow for the use of large femoral heads. However, concerns remain regarding elevated serum metal ion levels, potential teratogenic effects and potentially devastating adverse local tissue reactions, whose incidence and pathogenesis remains unclear. Modern total hip resurfacing has shown excellent outcomes over 10 years in the hands of experienced surgeons. Current ceramic-on-ceramic bearings have demonstrated excellent survival with exceptionally low wear rates and virtually no local adverse effects. Concerns remain for insertional chipping, in vivo fracture and the variable incidence of squeaking. Contemporary ceramic-on-metal interfaces are in the early stages of clinical use, with little data reported to date. Hard-on-hard bearings for total hip arthroplasty have improved dramatically over the past 50 years. As bearing designs continue to improve with new and modified materials and improved manufacturing techniques, it is likely that the use of hard-on-hard bearings will continue to increase, especially in young and active patients.

Incorrect use of the student t test in randomized trials of bilateral hip and knee arthroplasty patients

The statistical analysis of a study's results is critical to its interpretation. Often confused, 2 types of t tests exist for dependent or independent samples. We reviewed randomized controlled trials that included patients undergoing bilateral total hip or knee arthroplasty (dependent samples) that used the t test for analysis. Our inclusion criteria resulted in 40 studies for review, 10 of which combined both unilateral and bilateral patients. Of the 30 studies that compared a pure sample of only bilateral patients, 18 (60%) incorrectly used the independent t test. Of the 10 studies with mixed samples, 8 (80%) used the independent t test. The extent to which the incorrect use of this statistical test led to misleading conclusions is uncertain; however, our findings highlight the misuse of statistical tests in the arthroplasty literature.