Introduction

We investigated predictors of poor outcomes following metal-on-metal hip arthroplasty (MoMHA) revision surgery performed for adverse reactions to metal debris (ARMD), to help inform the revision threshold and type of reconstruction.

Introduction

Smoking, a modifiable factor, may adversely affect post-operative outcomes. Healthcare providers are increasingly denying smokers access to total hip arthroplasty (THA) until they stop smoking. Evidence supporting this is unclear. We assessed the effect of smoking on outcomes following THA.

Pseudotumours have recently been reported in non-metal-on-metal total hip replacements (non-MoM THRs), however the magnitude and risk factors for this complication are unknown, as is the outcome of its treatment.

3340 primary THR undergoing revision for pseudotumour between 2008 and 2015 were identified in the National Joint Registry for England and Wales. 7.5% (n=249) of these pseudotumour revisions, had non-MoM bearing surfaces. The risk of revision for pseudotumour in non-MoM hips was 0.032% (249/789,397; 95% CI 0.028%–0.036%). The risk of pseudotumour revision was 2.35 times (95% CI 1.76–3.11) higher in ceramic-on-ceramic compared with hard-on-soft bearings, and 2.80 times (95% CI 1.74–4.36) higher in 36mm metal-on-polyethylene bearings compared to 28mm and 32mm metal-on-polyethylene bearings.

The outcome of revision for pseudotumour non-MoM hips was studied in 185 hips. 13.5% (n=25) had re-revisions at a mean of 1.2 years (range 0.1–3.1 years). Infection (32%), dislocation/subluxation (24%), and aseptic loosening (24%) were the commonest indications for re-revision. The 4-year survival rate was 83.8% (95% CI=76.7%–88.9%). Multiple revision indications (Hazard Ratio (HR)=2.78; 95% CI=1.03–7.49) and incomplete revision procedures (HR=5.76; 95% CI=1.28–25.9) increased the risk of re-revision

Although the overall risk of revision for pseudotumour in non-MoM THRs is low, the risk is increasing and is significantly higher in ceramic-on-ceramic and large head metal-on-polyethylene THR. These revisions have a high early failure rate.

Outcomes following metal-on-metal hip replacement (MoMHR) revision surgery for adverse reactions to metal debris (ARMD) have been poor, and inferior compared with non-ARMD revisions. Subsequently, surgeons and worldwide authorities widely recommended early revision for ARMD, with a lower surgical threshold adopted. However, the impact of early surgery for ARMD is unknown. We compared the rates of adverse outcomes following MoMHR revision surgery in matched ARMD and non-ARMD patients.

We performed a retrospective observational study using data from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. All MoMHR patients subsequently undergoing revision surgery for any indication between August 2008 and August 2014 were eligible. ARMD and non-ARMD revisions were matched one-to-one for multiple potential confounding factors using propensity scores. Adverse outcomes following revision surgery (intra-operative complications, mortality, re-revision surgery) were compared between matched groups using regression analysis.

In 2,576 matched MoMHR revisions (ARMD=1,288 and non-ARMD=1,288), intra-operative complications were similar between ARMD (2.4%) and non-ARMD (2.5%) revisions (odds ratio=0.97, 95% CI=0.59–1.60; p=0.899). All-cause mortality rates were lower following ARMD revision compared with non-ARMD revision (hazard ratio (HR)=0.43, 95% CI=0.22–0.86; p=0.018). All-cause re-revision rates were lower following ARMD revision compared with non-ARMD revision (HR=0.52, 95% CI=0.36–0.75; p<0.001). Compared with ARMD revision (5-years=94.3%), MoMHR revisions for infection (5-years=81.2%) and dislocation/subluxation (5-years=81.9%) had the lowest implant survival rates.

Contrary to previous observations, MoMHRs revised for ARMD have approximately half the risk of re-revision and death compared to non-ARMD revisions. We suspect worldwide regulatory authorities have positively influenced outcomes following ARMD revision by widely recommending that surgeons exercise a lower revision threshold.

Our findings suggest the threshold for ARMD revision surgery need not be lowered further. The high risk of failure following MoMHR revision for infection and dislocation is concerning.

Recent studies have demonstrated that implant-specific blood metal ion thresholds exist in unilateral and bilateral metal-on-metal (MoM) hip arthroplasty patients, with these thresholds being most effective for identifying patients at low-risk of adverse reactions to metal debris (ARMD). We investigated whether these new blood metal ion thresholds could effectively identify patients at risk of ARMD in an external cohort of MoM hip arthroplasty patients.

We performed a validation study involving 803 MoM hip arthroplasties implanted in 710 patients at three European centres (323=unilateral Birmingham Hip Resurfacing (BHR); 93=bilateral BHR; 294=unilateral Corail-Pinnacle). All patients underwent whole blood metal ion sampling. Patients were divided into those with ARMD (revised for ARMD or ARMD on imaging; n=75), and those without ARMD (n=635). Previously devised implant-specific blood metal ion thresholds (cobalt=2.15μg/l for unilateral BHR; maximum cobalt or chromium=5.5μg/l for bilateral BHR; cobalt=3.57μg/l for unilateral Corail-Pinnacle) were applied to the validation cohort, with receiver operating characteristic curve analysis used to establish the discriminatory characteristics for each respective threshold.

The area under the curve, sensitivity, specificity, positive predictive value and negative predictive value for distinguishing between patients with and without ARMD for each implant-specific threshold were respectively: unilateral BHR=89.4% (95% CI=82.8%-96.0%), 78.9%, 86.7%, 44.1%, 96.9%; bilateral BHR=89.2% (95% CI=81.3%-97.1%), 70.6%, 86.8%, 54.5%, 93.0%; unilateral Corail-Pinnacle=76.9% (95% CI=63.9%-90.0%), 65.0%, 85.4%, 24.5%, 97.1%. The 7μg/l UK MHRA threshold missed significantly more patients with ARMD compared with the implant-specific thresholds (4.9% vs. 2.8%; p=0.0003).

This external multi-centre validation study has confirmed that MoM hip arthroplasty patients with blood metal ion levels below newly devised implant-specific thresholds have a low-risk of ARMD. Compared to implant-specific thresholds, the currently proposed fixed MHRA threshold missed more patients with ARMD.

We recommend using implant-specific thresholds over fixed thresholds when managing MoM hip arthroplasty patients.

Recent studies have reported on non-metal-on-metal hip arthroplasty (non-MoMHA) patients requiring revision surgery for adverse reactions to metal debris (ARMD). Although the outcomes following revision surgery for ARMD in MoMHA patients are known to generally be poor, little evidence exists regarding outcomes following non-MoMHA revision surgery performed for ARMD. We determined the outcomes following non-MoMHA revision surgery performed for ARMD, and identified predictors of re-revision.

We performed a retrospective observational study using data from the National Joint Registry for England, Wales, Northern Ireland and the Isle of Man. All primary non-MoMHA patients who subsequently underwent revision surgery for ARMD between 2008–2014 were included (n=185). Outcome measures following ARMD revision were intraoperative complications, mortality, and re-revision surgery. Predictors of re-revision surgery were identified using Cox regression analysis.

Intra-operative complications occurred in 6.0% (n=11) of ARMD revisions. The cumulative 4-year patient survival rate was 98.2% (95% CI=92.9–99.5%). Re-revision surgery was performed in 13.5% (n=25) of hips at a mean time of 1.2 years (range 0.1–3.1 years) following ARMD revision. Infection (32%), dislocation/subluxation (24%), and aseptic loosening (24%) were the commonest re-revision indications. The cumulative 4-year implant survival rate was 83.8% (95% CI=76.7%-88.9%). Significant predictors of re-revision were: multiple revision indications (Hazard Ratio (HR)=2.78; 95% CI=1.03–7.49; p=0.043), incomplete revision procedures (including modular component exchange only) (HR=5.76; 95% CI=1.28–25.9; p=0.022), and ceramic-on-polyethylene revision bearings (HR=3.08; 95% CI=1.01–9.36; p=0.047).

Non-MoMHA patients undergoing ARMD revision have a high short-term risk of re-revision. Infection, dislocation/subluxation, and aseptic loosening were the commonest re-revision indications. Furthermore, important and potentially modifiable predictors of future re-revision were identified.

Although the poor prognostic factors identified require validation in future studies, our findings may be used to counsel patients about the risks associated with ARMD revision surgery, and guide decisions about the reconstructive procedure.

Introduction

The impact of pseudotumours associated with metal-on-metal hip resurfacings (MoMHRs) within the second decade is unknown. We investigated: (1) the incidence and risk factors for all-cause and pseudotumour revision following MoMHR at 15-years follow-up, and (2) whether risk factors were gender specific.

Introduction

Joint preserving procedures have gained popularity in an attempt to delay arthroplasty in young, dysplastic hips. Excellent results can be achieved with peri-acetabular osteotomy (PAO) in congruent non-arthritic hips. The role of salvage procedures such as the Shelf acetabuloplasty remains undefined. This study aims to determine the long-term survival and functional outcome following Shelf acetabuloplasty and to identify factors that influence outcome.

Introduction

This study aimed to: (1) compare published follow-up guidelines for metal-on-metal (MoM) hip patients and analyse protocols in relation to current evidence, and (2) assess the financial implications of these guidelines.

We followed up 76 consecutive hips with symptomatic acetabular dysplasia treated by acetabular shelf augmentation for a mean period of 11 years. Survival analysis using conversion to hip replacement as an end-point was 86% at five years and 46% at ten years. Forty-four hips with slight or no narrowing of the joint space pre-operatively had a survival of 97% at five and 75% at ten years. This was significantly higher (p = 0.0007) than that of the 32 hips with moderate or severe narrowing of the joint-space, which was 76% at five and 22% at ten years. There was no significant relationship between survival and age (p = 0.37) or the pre- and post-operative centre-edge (p = 0.39) and acetabular angles (p = 0.85).

Shelf acetabuloplasty is a reliable, safe procedure offering medium-term symptomatic relief for adults with acetabular dysplasia. The best results were achieved in patients with mild and moderate dysplasia of the hip with little arthritis.

The Oxford hip score (OHS) is a patient-based instrument for assessment of outcome which is often used after total hip replacement, and the EuroQol 5D (EQ5D) is a patient-based generic questionnaire for health assessment. In an analysis of the outcome at one year of 609 revision hip replacements (RHRs), we compared the OHS and EQ5D scores, postoperative patient satisfaction and change in pain. About 25% of the operations were repeat RHRs. At one year, 57% of patients were very pleased with their operation. The correlation between preoperative and postoperative scores and change scores for the OHS and EQ5D was high. For both instruments the effect sizes were large, but the greater effect size of the OHS suggests that it is particularly sensitive to improvements after RHR. The effect scores of the OHS declined with the number of previous RHRs, while those for the EQ5D seemed less sensitive. Our results confirm the value of the OHS in assessing outcome after RHR.

We have developed a 12-item questionnaire for patients having a total knee replacement (TKR). We made a prospective study of 117 patients before operation and at follow-up six months later, asking them to complete the new questionnaire and the form SF36. Some also filled in the Stanford Health Assessment Questionnaire (HAQ). An orthopaedic surgeon completed the American Knee Society (AKS) clinical score.

The single score derived from the new questionnaire had high internal consistency, and its reproducibility, examined by test-retest reliability, was found to be satisfactory. Its validity was established by obtaining significant correlations in the expected direction with the AKS scores and the relevant parts of the SF36 and HAQ. Sensitivity to change was assessed by analysing the differences between the preoperative scores and those at follow-up.

We also compared change in scores with the patients’ retrospective judgement of change in their condition. The effect size for the new questionnaire compared favourably with those for the relevant parts of the SF36. The change scores for the new knee questionnaire were significantly greater (p < 0.0001) for patients who reported the most improvement in their condition.

The new questionnaire provides a measure of outcome for TKR that is short, practical, reliable, valid and sensitive to clinically important changes over time.

We developed a 12-item questionnaire for completion by patients having total hip replacement (THR). A prospective study of 220 patients was undertaken before operation and at follow-up six months later. Each completed the new questionnaire as well as the SF36, and some the Arthritis Impact Measurement Scales (AIMS). An orthopaedic surgeon assessed the Charnley hip score.

The single score derived from the questionnaire had a high internal consistency. Reproducibility was examined by test-retest reliability and was found to be satisfactory. The validity of the questionnaire was established by obtaining significant correlation in the expected direction with the Charnley scores and relevant scales of the SF36 and the AIMS. Sensitivity to change was assessed by analysing the differences between the preoperative scores and those at the follow-up. The standardised effect size for the new questionnaire compared favourably with that for the SF36 and the AIMS.

The new questionnaire provides a measure of outcome for THR which is short, practical, reliable, valid and sensitive to clinically important changes.