What are patients' preferences for revision surgery after periprosthetic joint infection? A discrete choice experiment

Survivorship of the dual-mobility construct in elective primary total hip replacement: a systematic review and meta-analysis including registry data

INTRODUCTION

Dislocation is a common complication associated with total hip replacement (THR). Dual-mobility constructs (DMC-THR) may be used in high-risk patients and have design features that may reduce the risk of dislocation. We aimed to report overall pooled estimates of all-cause construct survival for elective primary DMC-THR. Secondary outcomes included unadjusted dislocation rate, revision for instability, infection and fracture.

METHODS

MEDLINE, EMBASE, Web of Science, Cochrane Library and National Joint Registry reports were systematically searched (CRD42020189664). Studies reporting revision (all-cause) survival estimates and confidence intervals by brand and construct including DMC bearings were included. A meta-analysis was performed weighting series by the standard error.

RESULTS

Thirty-seven studies reporting 39 case series were identified; nine (10,494 DMC-THR) were included. Fourteen series (23,020 DMC-THR) from five national registries were included. Pooled case series data for all-cause construct survival was 99.7% (95% CI 99.5-100) at 5 years, 95.7% (95% CI 94.9-96.5) at 10 years, 96.1% (95% CI 91.8-100) at 15 years and 77% (95% CI 74.4-82.0) at 20 years. Pooled joint registry data showed an all-cause construct survivorship of 97.8% (95% CI 97.3-98.4) at 5 years and 96.3% (95% CI 95.6-96.9) at 10 years.

CONCLUSIONS

Survivorship of DMC-THR in primary THR is acceptable according to the national revision benchmark published by National Institute for Clinical Excellence (NICE).

Development of evidence-based guidelines for the treatment and management of periprosthetic hip infection

Aims

Periprosthetic hip-joint infection is a multifaceted and highly detrimental outcome for patients and clinicians. The incidence of prosthetic joint infection reported within two years of primary hip arthroplasty ranges from 0.8% to 2.1%. Costs of treatment are over five-times greater in people with periprosthetic hip joint infection than in those with no infection. Currently, there are no national evidence-based guidelines for treatment and management of this condition to guide clinical practice or to inform clinical study design. The aim of this study is to develop guidelines based on evidence from the six-year INFection and ORthopaedic Management (INFORM) research programme.

Methods

We used a consensus process consisting of an evidence review to generate items for the guidelines and online consensus questionnaire and virtual face-to-face consensus meeting to draft the guidelines.

Results

The consensus panel comprised 21 clinical experts in orthopaedics, primary care, rehabilitation, and healthcare commissioning. The final output from the consensus process was a 14-item guideline. The guidelines make recommendations regarding increased vigilance and monitoring of those at increased risk of infection; diagnosis including strategies to ensure the early recognition of prosthetic infection and referral to orthopaedic teams; treatment, including early use of DAIR and revision strategies; and postoperative management including appropriate physical and psychological support and antibiotic strategies.

Conclusion

We believe the implementation of the INFORM guidelines will inform treatment protocols and clinical pathways to improve the treatment and management of periprosthetic hip infection.

Cite this article: Bone Jt Open 2023;4(4):226–233.

Which Factors Are Considered by Patients When Considering Total Joint Arthroplasty? A Discrete-choice Experiment

BACKGROUND

TKA and THA are major surgical procedures, and they are associated with the potential for serious, even life-threatening complications. Patients must weigh the risks of these complications against the benefits of surgery. However, little is known about the relative importance patients place on the potential complications of surgery compared with any potential benefit the procedures may achieve. Furthermore, patient preferences may often be discordant with surgeon preferences regarding the treatment decision-making process. A discrete-choice experiment (DCE) is a quantitative survey technique designed to elicit patient preferences by presenting patients with two or more hypothetical scenarios. Each scenario is composed of several attributes or factors, and the relative extent to which respondents prioritize these attributes can be quantified to assess preferences when making a decision, such as whether to pursue lower extremity arthroplasty.

QUESTIONS/PURPOSES

In this DCE, we asked: (1) Which patient-related factors (such as pain and functional level) and surgery-related factors (such as the risk of infection, revision, or death) are influential in patients' decisions about whether to undergo lower extremity arthroplasty? (2) Which of these factors do patients emphasize the most when making this decision?

METHODS

A DCE was designed with the following attributes: pain; physical function; return to work; and infection risks, reoperation, implant failure leading to premature revision, deep vein thrombosis, and mortality. From October 2021 to March 2022, we recruited all new patients to two arthroplasty surgeons' clinics who were older than 18 years and scheduled for a consultation for knee- or hip-related complaints who had no previous history of a primary TKA or THA. A total of 56% (292 of 517) of new patients met the inclusion criteria and were approached with the opportunity to complete the DCE. Among the cohort, 51% (150 of 292) of patients completed the DCE. Patients were administered the DCE, which consisted of 10 hypothetical scenarios that had the patient decide between a surgical and nonsurgical outcome, each consisting of varying levels of eight attributes (such as infection, reoperation, and ability to return to work). A subsequent demographic questionnaire followed this assessment. To answer our first research question about the patient-related and surgery-related factors that most influence patients' decisions to undergo lower extremity arthroplasty, we used a conditional logit regression to control for potentially confounding attributes from within the DCE and determine which variables shifted a patient's determination to pursue surgery. To answer our second question, about which of these factors received the greatest priority by patients, we compared the relevant importance of each factor, as determined by each factor's beta coefficient, against each other influential factor. A larger absolute value of beta coefficient reflects a relatively higher degree of importance placed on a variable compared with other variables within our study. Of the respondents, 57% (85 of 150) were women, and the mean age at the time of participation was 64 ± 10 years. Most respondents (95% [143 of 150]) were White. Regarding surgery, 38% (57 of 150) were considering THA, 59% (88 of 150) were considering TKA, and 3% (5 of 150) were considering both. Among the cohort, 49% (74 of 150) of patients reported their average pain level as severe, or 7 to 10 on a scale from 0 to 10, and 47% (71 of 150) reported having 50% of full physical function.

RESULTS

Variables that were influential to respondents when deciding on lower extremity total joint arthroplasty were improvement from severe pain to minimal pain (β coefficient: -0.59 [95% CI -0.72 to -0.46]; p < 0.01), improvement in physical function level from 50% to 100% (β: -0.80 [95% CI -0.9 to -0.7]; p < 0.01), ability to return to work versus inability to return (β: -0.38 [95% CI -0.48 to -0.28]; p < 0.01), and the surgery-related factor of risk of infection (β: -0.22 [95% CI -0.30 to -0.14]; p < 0.01). Improvement in physical function from 50% to 100% was the most important for patients making this decision because it had the largest absolute coefficient value of -0.80. To improve physical function from 50% to 100% and reduce pain from severe to minimal because of total joint arthroplasty, patients were willing to accept a hypothetical absolute (and not merely an incrementally increased) 37% and 27% risk of infection, respectively. When we stratified our analysis by respondents' preoperative pain levels, we identified that only patients with severe pain at the time of their appointment found the risk of infection influential in their decision-making process (β: -0.27 [95% CI -0.37 to -0.17]; p = 0.01) and were willing to accept a 24% risk of infection to improve their physical functioning from 50% to 100%.

CONCLUSION

Our study revealed that patients consider pain alleviation, physical function improvement, and infection risk to be the most important attributes when considering total joint arthroplasty. Patients with severe baseline pain demonstrated a willingness to take on a hypothetically high infection risk as a tradeoff for improved physical function or pain relief. Because patients seemed to prioritize postoperative physical function so highly in our study, it is especially important that surgeons customize their presentations about the likelihood an individual patient will achieve a substantial functional improvement as part of any office visit where arthroplasty is discussed. Future studies should focus on quantitatively assessing patients' understanding of surgical risks after a surgical consultation, especially in patients who may be the most risk tolerant.

CLINICAL RELEVANCE

Surgeons should be aware that patients with the most limited physical function and the highest baseline pain levels are more willing to accept the more potentially life-threatening and devastating risks that accompany total joint arthroplasty, specifically infection. The degree to which patients seemed to undervalue the harms of infection (based on our knowledge and perception of those harms) suggests that surgeons need to take particular care in explaining the degree to which a prosthetic joint infection can harm or kill patients who develop one.

Infection after total joint replacement of the hip and knee: research programme including the INFORM RCT

Background

People with severe osteoarthritis, other joint conditions or injury may have joint replacement to reduce pain and disability. In the UK in 2019, over 200,000 hip and knee replacements were performed. About 1 in 100 replacements becomes infected, and most people with infected replacements require further surgery.

Objectives

To investigate why some patients are predisposed to joint infections and how this affects patients and the NHS, and to evaluate treatments.

Design

Systematic reviews, joint registry analyses, qualitative interviews, a randomised controlled trial, health economic analyses and a discrete choice questionnaire.

Setting

Our studies are relevant to the NHS, to the Swedish health system and internationally.

Participants

People with prosthetic joint infection after hip or knee replacement and surgeons.

Interventions

Revision of hip prosthetic joint infection with a single- or two-stage procedure.

Main outcome measures

Long-term patient-reported outcomes and reinfection. Cost-effectiveness of revision strategies over 18 months from two perspectives: health-care provider and Personal Social Services, and societal.

Data sources

National Joint Registry; literature databases; published cohort studies; interviews with 67 patients and 35 surgeons; a patient discrete choice questionnaire; and the INFORM (INFection ORthopaedic Management) randomised trial.

Review methods

Systematic reviews of studies reporting risk factors, diagnosis, treatment outcomes and cost comparisons. Individual patient data meta-analysis.

Results

In registry analyses, about 0.62% and 0.75% of patients with hip and knee replacement, respectively, had joint infection requiring surgery. Rates were four times greater after aseptic revision. The costs of inpatient and day-case admissions in people with hip prosthetic joint infection were about five times higher than those in people with no infection, an additional cost of > £30,000. People described devastating effects of hip and knee prosthetic joint infection and treatment. In the treatment of hip prosthetic joint infection, a two-stage procedure with or without a cement spacer had a greater negative impact on patient well-being than a single- or two-stage procedure with a custom-made articulating spacer. Surgeons described the significant emotional impact of hip and knee prosthetic joint infection and the importance of a supportive multidisciplinary team. In systematic reviews and registry analyses, the risk factors for hip and knee prosthetic joint infection included male sex, diagnoses other than osteoarthritis, high body mass index, poor physical status, diabetes, dementia and liver disease. Evidence linking health-care setting and surgeon experience with prosthetic joint infection was inconsistent. Uncemented fixation, posterior approach and ceramic bearings were associated with lower infection risk after hip replacement. In our systematic review, synovial fluid alpha-defensin and leucocyte esterase showed high diagnostic accuracy for prosthetic joint infection. Systematic reviews and individual patient data meta-analysis showed similar reinfection outcomes in patients with hip or knee prosthetic joint infection treated with single- and two-stage revision. In registry analysis, there was a higher rate of early rerevision after single-stage revision for hip prosthetic joint infection, but, overall, 40% fewer operations are required as part of a single-stage procedure than as part of a two-stage procedure. The treatment of hip or knee prosthetic joint infection with early debridement and implant retention may be effective in > 60% of cases. In the INFORM randomised controlled trial, 140 patients with hip prosthetic joint infection were randomised to single- or two-stage revision. Eighteen months after randomisation, pain, function and stiffness were similar between the randomised groups (p = 0.98), and there were no differences in reinfection rates. Patient outcomes improved earlier in the single-stage than in the two-stage group. Participants randomised to a single-stage procedure had lower costs (mean difference –£10,055, 95% confidence interval –£19,568 to –£542) and higher quality-adjusted life-years (mean difference 0.06, 95% confidence interval –0.07 to 0.18) than those randomised to a two-stage procedure. Single-stage was the more cost-effective option, with an incremental net monetary benefit at a threshold of £20,000 per quality-adjusted life-year of £11,167 (95% confidence interval £638 to £21,696). In a discrete choice questionnaire completed by 57 patients 18 months after surgery to treat hip prosthetic joint infection, the most valued characteristics in decisions about revision were the ability to engage in valued activities and a quick return to normal activity.

Limitations

Some research was specific to people with hip prosthetic joint infection. Study populations in meta-analyses and registry analyses may have been selected for joint replacement and specific treatments. The INFORM trial was not powered to study reinfection and was limited to 18 months’ follow-up. The qualitative study subgroups were small.

Conclusions

We identified risk factors, diagnostic biomarkers, effective treatments and patient preferences for the treatment of hip and knee prosthetic joint infection. The risk factors include male sex, diagnoses other than osteoarthritis, specific comorbidities and surgical factors. Synovial fluid alpha-defensin and leucocyte esterase showed high diagnostic accuracy. Infection is devastating for patients and surgeons, both of whom describe the need for support during treatment. Debridement and implant retention is effective, particularly if performed early. For infected hip replacements, single- and two-stage revision appear equally efficacious, but single-stage has better early results, is cost-effective at 18-month follow-up and is increasingly used. Patients prefer treatments that allow full functional return within 3–9 months.

Future work

For people with infection, develop information, counselling, peer support and care pathways. Develop supportive care and information for patients and health-care professionals to enable the early recognition of infections. Compare alternative and new treatment strategies in hip and knee prosthetic joint infection. Assess diagnostic methods and establish NHS diagnostic criteria.

Study registration

The INFORM randomised controlled trial is registered as ISRCTN10956306. All systematic reviews were registered in PROSPERO (as CRD42017069526, CRD42015023485, CRD42018106503, CRD42018114592, CRD42015023704, CRD42017057513, CRD42015016559, CRD42015017327 and CRD42015016664).

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 10, No. 10. See the NIHR Journals Library website for further project information.

Clinical and cost effectiveness of single stage compared with two stage revision for hip prosthetic joint infection (INFORM): pragmatic, parallel group, open label, randomised controlled trial

OBJECTIVES

To determine whether patient reported outcomes improve after single stage versus two stage revision surgery for prosthetic joint infection of the hip, and to determine the cost effectiveness of these procedures.

DESIGN

Pragmatic, parallel group, open label, randomised controlled trial.

SETTING

High volume tertiary referral centres or orthopaedic units in the UK (n=12) and in Sweden (n=3), recruiting from 1 March 2015 to 19 December 2018.

PARTICIPANTS

140 adults (aged ≥18 years) with a prosthetic joint infection of the hip who required revision (65 randomly assigned to single stage and 75 to two stage revision).

INTERVENTIONS

A computer generated 1:1 randomisation list stratified by hospital was used to allocate participants with prosthetic joint infection of the hip to a single stage or a two stage revision procedure.

MAIN OUTCOME MEASURES

The primary intention-to-treat outcome was pain, stiffness, and functional limitations 18 months after randomisation, measured by the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) score. Secondary outcomes included surgical complications and joint infection. The economic evaluation (only assessed in UK participants) compared quality adjusted life years and costs between the randomised groups.

RESULTS

The mean age of participants was 71 years (standard deviation 9) and 51 (36%) were women. WOMAC scores did not differ between groups at 18 months (mean difference 0.13 (95% confidence interval -8.20 to 8.46), P=0.98); however, the single stage procedure was better at three months (11.53 (3.89 to 19.17), P=0.003), but not from six months onwards. Intraoperative events occurred in five (8%) participants in the single stage group and 20 (27%) in the two stage group (P=0.01). At 18 months, nine (14%) participants in the single stage group and eight (11%) in the two stage group had at least one marker of possible ongoing infection (P=0.62). From the perspective of healthcare providers and personal social services, single stage revision was cost effective with an incremental net monetary benefit of £11 167 (95% confidence interval £638 to £21 696) at a £20 000 per quality adjusted life years threshold (£1.0; $1.1; €1.4).

CONCLUSIONS

At 18 months, single stage revision compared with two stage revision for prosthetic joint infection of the hip showed no superiority by patient reported outcome. Single stage revision had a better outcome at three months, fewer intraoperative complications, and was cost effective. Patients prefer early restoration of function, therefore, when deciding treatment, surgeons should consider patient preferences and the cost effectiveness of single stage surgery.

TRIAL REGISTRATION

ISRCTN registry ISRCTN10956306.

Managing periprosthetic joint infection-a qualitative analysis of nursing staffs' experiences

Background

Periprosthetic joint infection represents a major complication in orthopaedics and trauma surgery. For an ideal management approach, it is important to understand the distinct challenges for all persons involved in the treatment. Therefore, it was aimed at investigating (1) the impact of periprosthetic joint infection (PJI) on the well-being of nursing staff to (2) identify challenges, which could be improved facilitating the management of PJI.

Methods

This is a qualitative interview study. In total, 20 nurses of a German university orthopedic trauma center specialized on infectious complications were recruited using a purposive sampling strategy. Content analysis was performed on transcripts of individual in-person interviews conducted between March 2021 and June 2021.

Results

Three major themes could be extracted including (i) feelings associated with the management of PJI and the need for emotional support, illustrating the negative emotional impact on nurses, whereby receiving collegial support was perceived as an important coping strategy, (ii) patients’ psychological burden, highlighting the nurses’ lack of time to address mental issues adequately and, (iii) realization of the severity of PJI and compliance problems.

Conclusion

Identified facilitating factors for PJI management include strengthening of mental care in the treatment of PJI, providing opportunities for exchange among multidisciplinary team members and implementing compliance-enhancing strategies. The findings of this study can be beneficial for improving professionals’ satisfaction, optimising the work environment, creating organizational structures which enhance opportunities for exchange and preventing mental health issues among the nursing team.

How long do revised and multiply revised hip replacements last? A retrospective observational study of the National Joint Registry

Background

Hip replacements are common and effective operations but patients that undergo this intervention are at risk of the replacements failing, requiring costly and often complex revision surgery with poorer outcomes than primary surgery. There is paucity of reliable data examining the treatment pathway for hip replacements over the life of the patient in terms of risk of revision and re-revisions. We aim to provide detailed information on the longevity of hip revision surgery.

Methods

We did a retrospective observational registry-based study of the National Joint Registry, using data on hip replacements from all participating hospitals in England and Wales, UK. We included data on all first revisions, with an identifiable primary procedure, with osteoarthritis as the sole indication for the original primary procedure. Kaplan-Meier estimates were used to determine the cumulative probability of revision and subsequent re-revision after primary hip replacement. Analyses were stratified by age and gender, and the influence of time from first to second revision on the risk of further revision was explored.

Findings

Between April 1, 2003, and Dec 31, 2019, there were 29 010 revision hip replacements with a linked primary episode. Revision rates of revision hip replacements were higher in patients younger than 55 years than in older age groups. After revision of primary total hip replacement, 21·3% (95% CI 18·6-24·4) of first revisions were revised again within 15 years, 22·3% (20·3-24·4) of second revisions were revised again within 7 years, and 22·3% (18·3-27·0) of third revisions were revised again within 3 years. After revision of hip resurfacing, 23·7% (95% CI 19·6-28·5) of these revisions were revised again within 15 years, 21·0% (17·0-25·8) of second revisions were revised again within 7 years, and 19·3% (11·9-30·4) of third revisions were revised again within 3 years. A shorter time between revision episodes was associated with earlier subsequent revision.

Interpretation

Younger patients are at an increased risk of multiple revisions. Patients who undergo a revision have a steadily increasing risk of further revision the more procedures they undergo, and each subsequent revision lasts for approximately half the time of the previous one. Although hip replacements are effective for improving pain and function and usually last a remarkably long time, if they are revised, successive revisions are progressively and markedly less successful.

Funding

NIHR Biomedical Research Centre at the University Hospitals Bristol and Weston NHS Foundation Trust and the University of Bristol, Healthcare Quality Improvement Partnership; and the National Joint Registry.

Depression Is Transiently Increased in Patients Undergoing Two-Stage Revision Arthroplasty

BACKGROUND

The implications of two-stage revision on mental health are poorly understood. The purpose of this study is to determine (1) whether patients undergoing two-stage revision total hip and knee arthroplasty for prosthetic joint infection were more likely to get Patient-Reported Outcomes Measurement Information System (PROMIS) Depression scores consistent with major depressive disorder (MDD) than those undergoing aseptic revision and (2) whether these symptoms resolved after the procedure.

METHODS

Records of all 366 patients that underwent revision total hip or knee arthroplasty from January 1, 2015, - June 20, 2019, were reviewed. Forty-two patients were excluded for missing PROMIS Depression scores or incomplete treatment. Preoperative (<3 months), early postoperative (2-8 weeks), and final postoperative (6-18 months) Depression scores were collected. Patients crossing the PROMIS Depression threshold equivalent to a Patient Health Questionnaire-9 score ≥10, indicative of MDD, were evaluated.

RESULTS

More two-stage revision patients developed Depression scores indicative of MDD perioperatively than the aseptic cohort (20.0% vs 6.5%, P = .01). Two-stage revision patients had higher (worse) median Depression scores preoperatively (54.8 vs 51.3, P = .04) and at early follow-up (54.3 vs 49.9, P = .01), but not at final follow-up (50.4 vs 49.1, P = .39). Across all patients, Depression scores improved by 2.4 points at early follow-up (95% confidence interval:1.1-3.7; P < .001) and 3 points at final follow-up (95% confidence interval:1.5-4.5; P < .001; minimal clinically important difference 3.0).

CONCLUSIONS

Twenty percent of two-stage revision arthroplasty patients, compared to <7% of aseptic revision patients, developed PROMIS Depression scores consistent with MDD during treatment. At final follow-up, a clinically significant improvement in Depression scores from baseline was evident in both cohorts.

What are healthcare workers' preferences for hand hygiene interventions? A discrete choice experiment

OBJECTIVES

To understand the key attributes in designing effective interventions for improving healthcare workers' (HCWs') hand hygiene compliance and HCWs' preference for these attributes.

DESIGN

A discrete choice experiment (DCE) was conducted with five attributes extracted from the framework of Total Quality Management that can be applied in the design of hand hygiene interventions. They were hand hygiene monitoring, open discussion, message framing, resources accessibility and top management involvement. An addition attribute, peer hand hygiene performance, was considered as a contextual factor. Data were analysed by a conditional logit model to evaluate how these attributes impact HCWs' hand hygiene compliance.

SETTING

The DCE was conducted with participants from a university hospital in Taichung.

PARTICIPANTS

HCWs involved in daily patient-care activities (N=387).

RESULTS

To enhance their compliance, HCWs had strong and consistent preferences in having open discussion of hand hygiene problems ([Formula: see text], [Formula: see text]), easy access to hand hygiene resources ([Formula: see text], [Formula: see text]) and top management involvement ([Formula: see text], [Formula: see text]). For hand hygiene monitoring ([Formula: see text], [Formula: see text]), HCWs preferred to be monitored by infection control staff over their department head if their peer hand hygiene performance was low. On the other hand, when the peer performance was high, monitoring by their department head could improve their hand hygiene compliance. Similarly, how educational messages were framed impacted compliance and also depended on the peer hand hygiene performance. When the peer performance was low, HCWs were more likely to increase their compliance in reaction to loss-framed educational messages ([Formula: see text],[Formula: see text]). When the peer performance was high, gain-framed messages that focus on the benefit of compliance were more effective in inducing compliance.

CONCLUSIONS

Each intervention design has its unique impact on HCWs' hand hygiene compliant behaviour. The proposed approach can be used to evaluate HCWs' preference and compliance of an intervention before it is implemented.

How long do revised and multiply revised knee replacements last? An analysis of the National Joint Registry

BACKGROUND

Knee replacements are common and effective operations but patients that undergo this intervention are at risk of needing subsequent costly and often complex revision surgery with poorer outcomes than primary surgery. The treatment pathway over the life of the patient in terms of risk of revision and re-revision(s) is poorly described. We aim to provide detailed information on the longevity of revision surgery.

METHODS

This was a retrospective observational registry-based study of the National Joint Registry. Kaplan-Meier estimates were used to determine the cumulative probability of revision and subsequent re-revision(s) following primary knee replacement. Analyses were stratified by age and gender and the influence of time from first to second revision on the risk of further revision was explored.

FINDINGS

There were 33,292 revision knee replacements with a linked primary episode. Revision rates of revision knee replacements were higher in males and younger patients. 19·9% of revisions were revised again within 13 years, 20·7% of second revisions were revised again within 5 years and 20·7% of third revisions were revised again within 3 years. A shorter time between revision episodes was associated with earlier subsequent revision.

INTERPRETATION

Males and younger patients are at higher risk of multiple revisions. Patients who undergo a revision have steadily increasing risk of further revision the more procedures they undergo, and each subsequent revision lasts for approximately half the time of the previous one.

FUNDING

This study was supported by the NIHR Biomedical Research Centre at University Hospitals Bristol and Weston National Health Service Foundation Trust and the University of Bristol. The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care. This study was also supported by funding from Healthcare Quality Improvement Partnership and the National Joint Registry. Posts of authors of this work are part funded by a grant from the National Joint Registry to conduct statistical analysis for the National Joint Registry. AS was funded by a Medical Research Council Strategic Skills Fellowship MR/L01226X/1.