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Background: Total hip arthroplasty (THA) in patients younger than 50 years poses significant challenges including postoperative limitations of activity and higher failure rates. Sub-par outcomes of hip resurfacing arthroplasty (HRA) in registries remain controversial due to multiple confounders. Favourable HRA results in some studies are often regarded as irreproducible. The aim of this study is to analyse HRA outcomes in a large international cohort. Patients and methods: We compiled a database of 11,382 HRA patients ⩽50 years from an international group of 27 experienced HRA centres from 13 countries. 18 different metal-on-metal (MoM) HRA designs were included with a mean follow-up of 7.6 years. Outcomes were implant survivorship, revision rates, causes for revision, clinical scores and metal ion levels. Outcomes were compared between genders, sizes, implant types and pre-operative diagnoses. Results: Overall cumulative Kaplan-Meier survivorship was 88.9% at 22 years (95% CI: 88.3–89.5%). 2 HRA designs (DePuy Articular Surface Replacement (ASR), and Corin Cormet Hip Resurfacing System (CORMET)) led to inferior results while all others yielded similar survivorships. Excluding ASR and CORMET, implant survivorship in 11,063 cases was 95% at 10 years and 90% at 22 years. In men, implant survivorship was excellent: 99% at 10 years and 92.5% at 21 years. In females, implant survivorship was 90% at 10 years and 81.3% at 22 years. The overall revision rate was 3.6% with most common reasons for revision being implant loosening and adverse local tissue reactions. The best survivorship was found in patients with osteoarthritis (95% CI, 92.1–93.3% at 22 years), the poorest was among dysplastic hips (78.3%; 95% CI, 76.5–80.1% at 20 years, p < 0.001). Conclusions: Comparable revision rates demonstrated here may mitigate some concerns for safety and longevity of MoM HRA implants. Higher demands for activity and functionality in younger patients make HRA a potential alternative to THA. [ABSTRACT FROM AUTHOR]

Background: A new version of The Knee Society Knee Scoring System (KSS) has recently been developed. Before this scale can be used in non-English-speaking populations, it has to be translated and validated for a particular population. Questions/purposes: We evaluated the construct and content validity, the test-retest reliability, and the internal consistency of the Dutch version of the New Knee Society KSS. Methods: A Dutch translation was performed using a forward-backward translation protocol. We tested the construct validity of the Dutch New KSS by comparing it with the Dutch versions of the WOMAC, Knee Injury and Osteoarthritis Outcome Score (KOOS), and SF-12 scores in 137 patients undergoing total knee arthroplasty (TKA). Content validity was assessed by comparing pre- and postoperative scores and by checking floor and ceiling effects. To evaluate test-retest reliability and consistency, 47 patients completed the questionnaire a second time with a mean of 8 days interval (range, 2-20 days) between tests. Results: Construct validity was demonstrated because the Dutch New KSS correlated well with the Dutch WOMAC (r = −0.751; p < 0.001), Dutch KOOS (r = −0.723; p < 0.001), and Dutch SF-12 (r = 0.569; p < 0.001). There was a significant difference between pre- and postoperative scores (p < 0.001) in line with the other scores. Test-retest reliability proved excellent with an intraclass correlation coefficient between 0.73 and 0.92 depending on the domain tested. Consistency as indicated by Cronbach's alpha ranging from 0.84 to 0.96 was good to excellent. Conclusions: As demonstrated by the validation procedure, the Dutch New KSS is an excellent instrument to evaluate TKA outcome in Dutch-speaking patients. Level of Evidence: Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence. [ABSTRACT FROM AUTHOR]