Fractured Femoral Stems in Primary and Revision Hip Arthroplasties Revisited: Wrightington Experience.

BACKGROUND: The aim of this study is to present our experience in managing fractured femoral stems over the last 10 years for both primary and revision stems at our tertiary unit focusing on modes of failure and operative techniques. METHODS: This is a retrospective consecutive study of all patients with fractured femoral stems that were operatively managed in our unit between 2008 and 2018. Detailed radiographic evaluation (Paprosky classification) was undertaken and data collected on operative techniques used to extract distal fractured stem fragments. RESULTS: Thirty-five patients (35 hips) were included (25 men/10 women) with average age at time of presentation of 68 years (range, 29-93). Average body mass index was 30 (standard deviation, 3.8; range, 22.5-39). There were variety of stems both contemporary and historical, primary and revision cases (15 hips polished tapered cemented stems, 10 hips composite beam and miscellaneous stems, and 10 revision hip stems). The predominant mechanism of failure was fatigue due to cantilever bending in distally fixed stems. Surgical techniques used to extract distal fragment were drilling technique in 2 hips, cortical window in 13 hips, extended trochanteric osteotomy (ETO) in 5 hips, and proximal extraction in 15 hips. CONCLUSION: When faced with a contemporary fractured stem, drilling techniques into the distal fragment are unlikely to succeed. If a trochanteric osteotomy had been used at time of index surgery, this could be used again to aid proximal extraction with conventional revision instrumentations. The cortical window technique is useful but surgically demanding technique that is most successful in extracting polished tapered fractured stems particularly when an ETO is not planned for femoral reconstruction. Use of trephines can be useful for removal of longer, uncemented stems. Finally, an ETO might be necessary when other techniques have failed.

Hip replacement.

Total hip replacement is a frequently done and highly successful surgical intervention. The procedure is undertaken to relieve pain and improve function in individuals with advanced arthritis of the hip joint. Symptomatic osteoarthritis is the most common indication for surgery. In paper 1 of this Series, we focus on how patient factors should inform the surgical decision-making process. Substantial demands are placed upon modern implants, because patients expect to remain active for longer. We discuss the advances made in implant performance and the developments in perioperative practice that have reduced complications. Assessment of surgery outcomes should include patient-reported outcome measures and implant survival rates that are based on data from joint replacement registries. The high-profile failure of some widely used metal-on-metal prostheses has shown the shortcomings of the existing regulatory framework. We consider how proposed changes to the regulatory framework could influence safety.

Is patient satisfaction related to patient reported sounds from ceramic on ceramic total hip arthroplasty? A study of 265 hips.

INTRODUCTION: The ideal method and implant to perform total hip arthroplasty (THA) is still a debated topic. Ceramic on ceramic (CoC) bearings have favourable wear properties, but squeaking has been reported as an unwanted side effect. We aimed to determine the rate of noise generation from CoC hips and investigate whether there is a relationship with patient satisfaction. METHODS: A total of 246 consecutive CoC bearing uncemented THA were retrospectively identified in a single institution. Post-operatively patients were sent a postal questionnaire to evaluate their reported sounds and satisfaction with their THA. Uni- and multi-variate analyses were performed to identify potential predictor variables for reported post-operative sounds. RESULTS: Questionnaires were returned by 172 patients (70% return rate). 24% reported sounds from their hips with 11% reporting a squeak. Median satisfaction levels were minimally, but significantly less for "noisy" (9/10) than "quiet" hips (10/10) (median difference = - 1, 95% CI - 2 to 0, p < 0.001). Compared to those with "noisy" hips, patients with "quiet" hips were 1.7 times (95% CI 1.3-2.5, p = 0.0002) more likely to report a "forgotten" hip. Younger age (p < 0.043) and increased anteversion (p < 0.021) were predictors for reported sounds. CONCLUSION: We have identified a high rate of "noisy" hips in this series of CoC THA with a significant inverse relationship between "noisy" hips and patient satisfaction levels. In our unit, we are moving towards the use of ceramic on cross-linked polyethylene bearings as a result of these findings and the excellent survivorship of this bearing combination.

Does oversizing an uncemented cup increase post-operative pain in primary total hip arthroplasty?

INTRODUCTION: It has been suggested that one of the factors related to persistent post-operative pain following total hip arthroplasty (THA) is to over sizing of the acetabular component. In order to investigate this potential issue, we retrospectively analysed a series of consecutive uncemented THA. We assessed the incidence of persistent post-operative pain and the size difference between the implanted acetabular component and the native femoral head. METHODS: A total of 265 consecutive THAs were retrospectively identified. Standardised pre-operative radiographs were analysed using validated techniques to determine the native femoral head diameter. Post-operative standardised radiographs were reviewed and the acetabular orientation determined. Patients were sent postal questionnaires regarding their outcome and level of pain. RESULTS: Questionnaires were returned by 169 patients (189 hips, 71% response rate). A total of 17 were excluded due to inadequate radiographs., leaving 172 THA in the study group. The mean native femoral head (NFH) size was 47 mm. The most common implanted acetabular component size was 52 mm. The mean difference in cup to NFH diameter (delta) was 5.7 mm (range - 6.1 to 15.4 mm; 95% CI 5.3-6.2 mm). A delta of > 6 mm was found to be significant for predicting persistent post-operative pain (RR = 1.81; 95% CI 1.1-3.1; P = 0.027). CONCLUSION: Our study confirms that a delta of > 6 mm is associated with an increased risk of persistent post-operative pain following THA. We recommend pre-operative templating in all uncemented THA to ensure the planned acetabular component is no more than 6 mm larger than the NFH diameter.

Have cementless and resurfacing components improved the medium-term results of hip replacement for patients under 60 years of age?

BACKGROUND AND PURPOSE: The optimal hip replacement for young patients remains unknown. We compared patient-reported outcome measures (PROMs), revision risk, and implant costs over a range of hip replacements. METHODS: We included hip replacements for osteoarthritis in patients under 60 years of age performed between 2003 and 2010 using the commonest brand of cemented, cementless, hybrid, or resurfacing prosthesis (11,622 women and 13,087 men). The reference implant comprised a cemented stem with a conventional polyethylene cemented cup and a standard-sized head (28- or 32-mm). Differences in implant survival were assessed using competing-risks models, adjusted for known prognostic influences. Analysis of covariance was used to assess improvement in PROMs (Oxford hip score (OHS) and EQ5D index) in 2014 linked procedures. RESULTS: In males, PROMs and implant survival were similar across all types of implants. In females, revision was statistically significantly higher in hard-bearing and/or small-stem cementless implants (hazard ratio (HR) = 4) and resurfacings (small head sizes (< 48 mm): HR = 6; large head sizes (≥ 48 mm): HR = 5) when compared to the reference cemented implant. In component combinations with equivalent survival, women reported significantly greater improvements in OHS with hybrid implants (22, p = 0.006) and cementless implants (21, p = 0.03) (reference, 18), but similar EQ5D index. For men and women, National Health Service (NHS) costs were lowest with the reference implant and highest with a hard-bearing cementless replacement. INTERPRETATION: In young women, hybrids offer a balance of good early functional improvement and low revision risk. Fully cementless and resurfacing components are more costly and do not provide any additional benefit for younger patients.

Failure rates of stemmed metal-on-metal hip replacements: analysis of data from the National Joint Registry of England and Wales.

BACKGROUND: Total hip replacement (THR) is extremely common. Some prostheses fail, particularly in younger patients, and need to be revised, most commonly for loosening secondary to wear or dislocation. Surgeons have tried to address these problems by implanting large diameter metal-on-metal bearing surfaces. Our aim was to assess if metal-on-metal bearing surfaces lead to increased implant survival compared with other bearing surfaces in stemmed THR and, additionally, if larger head sizes result in improved implant survival. METHODS: We analysed the National Joint Registry of England and Wales for primary hip replacements (402,051, of which 31,171 were stemmed metal-on-metal) undertaken between 2003 and 2011. Our analysis was with a multivariable flexible parametric survival model to estimate the covariate-adjusted cumulative incidence of revision adjusting for the competing risk of death. FINDINGS: Metal-on-metal THR failed at high rates. Failure was related to head size, with larger heads failing earlier (3·2% cumulative incidence of revision [95% CI 2·5-4·1] for 28 mm and 5·1% [4·2-6·2] for 52 mm head at 5 years in men aged 60 years). 5 year revision rates in younger women were 6·1% (5·2-7·2) for 46 mm metal-on-metal compared with 1·6% (1·3-2·1) for 28 mm metal-on-polyethylene. By contrast, for ceramic-on-ceramic articulations larger head sizes were associated with improved survival (5 year revision rate of 3·3% [2·6-4·1] with 28 mm and 2·0% [1·5-2·7] with 40 mm for men aged 60 years). INTERPRETATION: Metal-on-metal stemmed articulations give poor implant survival compared with other options and should not be implanted. All patients with these bearings should be carefully monitored, particularly young women implanted with large diameter heads. Since large diameter ceramic-on-ceramic bearings seem to do well we support their continued use. FUNDING: National Joint Registry of England and Wales.

Mortality and re-revision following single-stage and two-stage revision surgery for the management of infected primary hip arthroplasty in England and Wales.

We compared the risks of re-revision and mortality between two-stage and single-stage revision surgeries among patients with infected primary hip arthroplasty. Patients with a periprosthetic joint infection (PJI) of their primary arthroplasty revised with single-stage or two-stage procedure in England and Wales between 2003 and 2014 were identified from the National Joint Registry. We used Poisson regression with restricted cubic splines to compute hazard ratios (HRs) at different postoperative periods. The total number of revisions and re-revisions undergone by patients was compared between the two strategies. In total, 535 primary hip arthroplasties were revised with single-stage procedure (1,525 person-years) and 1,605 with two-stage procedure (5,885 person-years). All-cause re-revision was higher following single-stage revision, especially in the first three months (HR at 3 months = 1.98 (95% confidence interval (CI) 1.14 to 3.43), p = 0.009). The risks were comparable thereafter. Re-revision for PJI was higher in the first three postoperative months for single-stage revision and waned with time (HR at 3 months = 1.81 (95% CI 1.22 to 2.68), p = 0.003; HR at 6 months = 1.25 (95% CI 0.71 to 2.21), p = 0.441; HR at 12 months = 0.94 (95% CI 0.54 to 1.63), p = 0.819). Patients initially managed with a single-stage revision received fewer revision operations (mean 1.3 (SD 0.7) vs 2.2 (SD 0.6), p < 0.001). Mortality rates were comparable between these two procedures (29/10,000 person-years vs 33/10,000). The risk of unplanned re-revision was lower following two-stage revision, but only in the early postoperative period. The lower overall number of revision procedures associated with a single-stage revision strategy and the equivalent mortality rates to two-stage revision are reassuring. With appropriate counselling, single-stage revision is a viable option for the treatment of hip PJI.

International Registries: U.K. National Joint Registry, Nordic Registries, and Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR).

ABSTRACT: National-level joint arthroplasty registries were among the first large orthopaedic surgery databases and represent some of the longest-running and most influential big databases in our profession. Nordic registries were among the first registries and were followed by excellent registries in the United Kingdom and Australia. In this article, we describe each of these registries and highlight the data elements collected, the data points that can be obtained by linking the national arthroplasty registries to other national registries or databases, the completeness of data, and the strengths and weaknesses of each database. Each of these registries publishes an annual report that is available online, and each also can do more detailed analysis of certain aspects of its data for special studies.When evaluating and interpreting data from national joint registries, the user should be aware that, despite the power of huge numbers, there remain numerous limitations to the observational data. Strong selection biases exist with regard to which patients are chosen for which procedure. Surgeons of different skill levels may use one technique or implant differentially compared with another. The end points that registries collect differ widely: for example, some report only hip dislocations leading to revision rather than all dislocations. Registries in countries in which there are long wait times for revision surgery may report artificially low revision rates compared with countries in which revision surgery is more easily accessible. Despite these limitations, registries have the merit of reporting the actual results of huge numbers of surgical procedures performed across the spectrum of hospitals, surgeons, and patients, making the data extremely powerful for identifying trends, identifying early signs of problems related to certain implants or implant classes, and identifying associations between variables that can be further studied to determine if the effect is causal.

Proximal femoral replacement in non-neoplastic revision hip arthroplasty : five-year results.

AIMS: With increasing burden of revision hip arthroplasty (THA), one of the major challenges is the management of proximal femoral bone loss associated with previous multiple surgeries. Proximal femoral arthroplasty (PFA) has already been popularized for tumour surgeries. Our aim was to describe the outcome of using PFA in these demanding non-neoplastic cases. METHODS: A retrospective review of 25 patients who underwent PFA for non-neoplastic indications between January 2009 and December 2015 was undertaken. Their clinical and radiological outcome, complication rates, and survival were recorded. All patients had the Stanmore Implant - Modular Endo-prosthetic Tumour System (METS). RESULTS: At mean follow-up of 5.9 years, there were no periprosthetic fractures. Clearance of infection was achieved in 63.6% of cases. One hip was re-revised to pseudo arthroplasty for deep infection. Instability was noted in eight of the hips (32%), of which seven needed further surgery. Out of these eight hips with instability, five had preoperative infection. Deep infection was noted in five of the hips (20%), of which four were primarily revised for infection. One patient had aseptic loosening of the femoral component and awaits revision surgery. The Kaplan-Meier survivorship free of revision of any component for any reason was 72% (95% confidence interval (CI) 51.3% to 92.7%), and for revisions of only femoral component for any reason was 96% (95% CI 86.3% to 105.7%) at five years. CONCLUSION: Dislocation and infection remain the major cause for failure, particularly in patients with pre-existing infection. The use of dual mobility cups, silver-coated implants, and less aggressive postoperative rehabilitation regimens would possibly aid in the reduction of complications. PFA performed in patients with periprosthetic fracture seem to fair better. This study supports the judicious use of PFA in non-oncological revision hip arthroplasties, and that they be performed by experienced revision arthroplasty surgeons. Cite this article: Bone Jt Open 2022;3(3):229-235.

Metal allergy in primary and revision total knee arthroplasty : a scoping review and evidence-based practical approach.

AIMS: Metal allergy in knee arthroplasty patients is a controversial topic. We aimed to conduct a scoping review to clarify the management of metal allergy in primary and revision total knee arthroplasty (TKA). METHODS: Studies were identified by searching electronic databases: Cochrane Central Register of Controlled Trials, Ovid MEDLINE, and Embase, from their inception to November 2020, for studies evaluating TKA patients with metal hypersensitivity/allergy. All studies reporting on diagnosing or managing metal hypersensitivity in TKA were included. Data were extracted and summarized based on study design, study population, interventions and outcomes. A practical guide is then formulated based on the available evidence. RESULTS: We included 38 heterogeneous studies (two randomized controlled trials, six comparative studies, 19 case series, and 11 case reports). The evidence indicates that metal hypersensitivity is a rare complication with some histopathological features leading to pain and dissatisfaction with no reliable screening tests preoperatively. Hypoallergenic implants are viable alternatives for patients with self-reported/confirmed metal hypersensitivity if declared preoperatively; however, concerns remain over their long-term outcomes with ceramic implants outperforming titanium nitride-coated implants and informed consent is paramount. For patients presenting with painful TKA, metal hypersensitivity is a diagnosis of exclusion where patch skin testing, lymphocyte transformation test, and synovial biopsies are useful adjuncts before revision surgery is undertaken to hypoallergenic implants with shared decision-making and informed consent. CONCLUSION: Using the limited available evidence in the literature, we provide a practical approach to metal hypersensitivity in TKA patients. Future national/registry-based studies are needed to identify the scale of metal hypersensitivity, agreed diagnostic criteria, and management strategies. Cite this article: Bone Jt Open 2021;2(10):785-795.

Early results of a high friction surface coated uncemented socket in revision hip arthroplasty.

BACKGROUND: Revision hip arthroplasty with high friction trabecular metal sockets has resulted in good medium-term results. Many manufacturers have therefore introduced higher friction coatings to their implants to meet a growing demand for similar implants. The Pinnacle Gription was introduced in 2007 as an evolution of the standard Pinnacle socket. This study aimed to assess the early results of this socket in a revision setting. METHODS: Between August 2009 and December 2016, the Gription socket was used in 146 revision hip replacements. The mean age was 63 (19-88) years. Defects were classified as Paprosky Grade 2 in 71(2A [28], 2B [19], 2C [24]) and grade 3 in 20 (3A [18], 3B [2]). Bearing combinations were ceramic-on-ceramic in 23, metal-on-polyethylene in 71, ceramic-on-polyethylene in 52. Screws were used in 112 cases, impaction bone grafting in 34 and metal augments in 1 case. Radiographs were analysed for progressive radiolucent lines and migration. RESULTS: Mean follow-up was 43.5 (range 25-62) months. There were 6 re-revisions (2 for deep infection, 2 for recurrent dislocation and 2 for aseptic loosening). None of the other cases had evidence of socket migration or progressive radiolucent lines. There were no intraoperative or postoperative periprosthetic fractures. The crude survivorship for all-cause failure was 95.8% and the survivorship for aseptic loosening was 98.6%. at 43.5 months follow-up. CONCLUSIONS: This is the largest reported series of Gription socket use in revision arthroplasty and demonstrates encouraging early results. We therefore advocate the continued cautious use of this implant.

Overview of Randomized Controlled Trials in Primary Total Hip Arthroplasty (34,020 Patients): What Have We Learnt?

AIM: To provide an overview of randomized controlled trials (RCTs) in primary total hip arthroplasty summarizing the available high-quality evidence. MATERIALS AND METHODS: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA), we searched the Cochrane Central Register of Controlled Trials (2020, Issue 1), Ovid MEDLINE, and Embase. We excluded nonrandomized trials, trials on neck of femur fractures or revision surgery, systematic reviews, and meta-analyses. Trials that met our inclusion criteria were assessed using a binary outcome measure of whether they reported statistically significant findings. These were then classified according to the intervention groups (surgical approach, fixation, and component design use, among others). RESULTS: Three hundred twelve RCTs met the inclusion criteria and were included. The total number of patients in those 312 RCTs was 34,020. Sixty-one RCTs (19.5%) reported significant differences between the intervention and the control groups. The trials were grouped into surgical approach 72, fixation 7, cement 16, femoral stem 46, head sizes 5, cup design 18, polyethylene 25, bearing surfaces 30, metal-on-metal 30, resurfacing 20, navigation 15, robotics 3, surgical technique 12, and closure/drains/postoperative care 13 RCTs. DISCUSSION: The evidence reviewed indicates that for the vast majority of patients, a standard conventional total hip arthroplasty with a surgical approach familiar to the surgeon using standard well-established components and highly cross-linked polyethylene leads to satisfactory clinical outcomes. This evidence also offers arthroplasty surgeons the flexibility to use the standard and cost-effective techniques and achieve comparable outcomes.

Notes on the use and interpretation of radiostereometric analysis.

With increasing numbers of research groups carrying out radiostereometric analysis (RSA), it is important to reach a consensus on how the main aspects of the technique should be carried out and how the results should be presented in an appropriate and consistent way. In this collection of guidelines, we identify a number of methodological and reporting issues including: measurement error and precision, migration and migration direction data, and the use of RSA as a screening technique. Alternatives are proposed, and a statistical analysis is presented, from which a sample size of 50 is recommended for screening of newly introduced prostheses.

Outcomes of Cement in Cement Revision, in Revision Total Hip Arthroplasty.

BACKGROUND: The cement-in-cement femoral revision technique involves removing a femoral component from a well-fixed femoral cement mantle and cementing a new stem into the original mantle. This technique, when carried out for the correct indications, is fast, relatively inexpensive and carries a reduced short-term risk for the patient compared with conventional way of removing well-fixed cement. AIM: To analyze the effectiveness of cement in cement revision of the femoral stem while performing a revision Total Hip Arthroplasty (THA). METHODS: We analyzed a consecutive series of 79 patients who underwent a cement in cement revision THA between June-2015 to June-2018. All the patients were retrospectively analysed for operative time, complications, clinical and radiological outcomes. RESULTS: Average age was 76 years (49-86). The mean follow-up was 16.2 months (12-45). The average operative time was 184.6 (90-290) minutes. Most common indication was cup loosening in 28 patients (42.4%), dislocation in 14 patients (21.2%) and stem loosening in 12 patients (18.2%) Nine patients (11%) had one or more complications. Pre-operatively, 10 patients (13%) had lucency at the cement bone interface. Recent review has shown that 8 of these patients' radiographs have remained unchanged, and in 2 of them there is a slight progression of lucency. Common post op clinical complaintswere persistent pain and abductor weakness. Five (6.3%) patients required a re-revision. Most of the patients had a good or satisfactory outcome.No stems showed radiological loosening. CONCLUSION: The cement-in-cement technique for revision of the femoral component gave promising results and had the advantages of speed, less blood or bone stock loss, less risk of femoral perforation or fracture, decreased financial costs and reduced post op morbidity.

Orthopaedic registries - the UK view (National Joint Registry): impact on practice.

The National Joint Registry (NJR) was established in 2002 as the result of an unexpectedly high failure rate of a cemented total hip replacement.Initial compliance with the Registry was low until data entry was mandated. Current case ascertainment is approximately 95% for primary procedures and 90% for revision procedures.The NJR links to other data sources to enrich the reporting processes. The NJR provides several web-based and open-access reports to the public and detailed confidential performance reports to individual surgeons, hospitals and industry bodies.A transparency and accountability process ensures that device and surgical performance are actively monitored on a six-monthly basis, and adverse variation is dealt with in an appropriate way that underpins patient safety.The NJR also manages a comprehensive research-ready database and data protection compliant access system that enables external researchers to use the dataset and perform independent analyses for patient benefit.Moving forwards, the NJR intends to look at factors that lead to better outcomes so that good practice can be embedded into routine care. Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180084.

Assessing the non-inferiority of prosthesis constructs used in hip replacement using data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man: a benchmarking study.

OBJECTIVES: To investigate the relative performance of hip prosthesis constructs as compared with the best performing prosthesis constructs and illustrate the substantial variability in performance of currently used prostheses. DESIGN: A non-inferiority study. SETTING: The National Joint Registry for England, Wales, Northern Ireland and the Isle of Man (NJR). PARTICIPANTS: All patients with a primary total hip replacement registered in the NJR between 1 April 2003 and 31 December 2016. MAIN OUTCOME MEASURES: Kaplan-Meier failure function for hip prosthesis constructs. Failure difference between best performing construct and remaining constructs. METHODS: Using a non-inferiority analysis, the performance of hip prosthesis constructs by brand were compared with the best performing contemporary construct. Construct failure was estimated using the 1-Kaplan-Meier survival function method, that is, an estimate of net failure. The difference in failure between the contemporary benchmark and all other constructs was tested. RESULTS: Of the 4442 constructs used, only 134 had ≥500 procedures at risk at 3 years postprimary, 89 of which were not demonstrated to be inferior to the benchmark by at least 100% relative risk. By 10 years postprimary, there were 26 constructs with ≥500 at risk, 13 of which were not demonstrated to be inferior by at least 20% relative risk.Even fewer constructs were not inferior to the benchmark when analysed by age and gender. At 5 years postprimary, there were 15 constructs in males and 11 in females, aged 55-75 years, not shown to be inferior. CONCLUSIONS: There is great variability in construct performance and the majority of constructs have not been demonstrated to be non-inferior to contemporary benchmarks. These results can help to inform patients, clinicians and commissioners when considering hip replacement surgery.

Assessing the non-inferiority of prosthesis constructs used in total and unicondylar knee replacements using data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man: a benchmarking study.

OBJECTIVES: To investigate the relative performance of knee replacement constructs compared with the best performing construct and illustrate the substantial variability in performance. DESIGN: A non-inferiority study. SETTING: England and Wales. PARTICIPANTS: All primary total and unicondylar knee replacements performed and registered in the National Joint Registry between 1 April 2003 and 31 December 2016. MAIN OUTCOME MEASURES: Kaplan-Meier failure function for knee replacement constructs. Failure difference between best performing construct (the benchmark) and other constructs. METHODS: Using a non-inferiority analysis, the performance of knee replacement constructs by brand were compared with the best performing construct. Construct failure was estimated using the 1-Kaplan Meier method, that is, an estimate of net failure. The difference in failure between the contemporary benchmark construct and all other constructs were tested. RESULTS: Of the 449 different knee replacement constructs used, only 27 had ≥500 procedures at risk at 10 years postprimary, 18 of which were classified as inferior to the benchmark by at least 20% relative risk of failure. Two of these 18 were unicondylar constructs that were inferior by at least 100% relative risk. In men, aged 55-75 years, 12 of 27 (44%) constructs were inferior by at least 20% to the benchmark at 7 years postprimary. In women, aged 55-75 years, 8 of 32 (25%) constructs were inferior at 7 years postprimary. Very few constructs were classified as non-inferior to the contemporary benchmark. CONCLUSIONS: There are few knee replacement constructs that can be shown to be non-inferior to a contemporary benchmark. Unicondylar knee constructs have, almost universally, at least 100% worse revision outcomes compared with the best performing total knee replacement. These results will help to inform patients, clinicians and commissioners when considering knee replacement surgery.