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Surgical management options for bilateral knee osteoarthritis comprise staged or single-anaesthetic bilateral total knee replacements (SABTKRs). We examined the New Zealand Joint Registry hypothesizing there would be no difference between these practices compared to unilateral total knee replacement (TKR) examining 30-day mortality, all-cause revision rate and function.For this study, 84 946 primary TKRs were identified. We compared three groups: unilateral TKRs, all SABTKRs and all staged bilateral TKRs with intervals of 1 to 90 days, 91 days to 1 year and1 year. Cumulative revision rates were calculated (Kaplan-Meier method). Mortality risks were compared to unilateral TKR and hazard ratios (HRs) calculated. Six-month Oxford scores were compared using analysis of variance.Thirty-day mortality for SABTKR was 0.219%: unilateral TKR 0.236% (HR 0.43; 95% confidence interval (CI) 0.38-0.48; P 001). Staged TKR had lower mortality than unilateral TKR at three time interval groups unless performed within 90 days (adjusting for age and American Society of Anesthesiologists grade) TKR (90 days HR 0.92; 95% CI 0.703-1.371; P = 0.915; 91-365 days HR 0.783; 95% CI 0.687-0.891; P 0.001;365 days HR 0.394; 95% CI 0.344-0.451; P 0.001). Revision risk with SABTKR was lower at 0.43/100 component years (95% CI 0.37-0.49/100 component years) compared to unilateral 0.56/100 component years (95% CI 0.53-0.59; P 0.05). Six-month Oxford scores were superior in SABTKR versus unilateral TKR (38.6 (95% CI 38.2-39) versus 36.9 (95% CI 36.8-37.1); P 0.001).SABTKR is at least as safe as unilateral TKR or staged bilateral TKR in appropriately selected cases. Surgeons should wait at least 90 days before the second procedure.

BACKGROUND The surgical management options for bilateral hip osteoarthritis comprise staged or single-anaesthetic bilateral total hip replacements (THRs). The key issue of contention in performing the latter remains safety. We compared unilateral, staged bilateral and single-anaesthetic bilateral THR with the hypothesis that there would be no difference between these three practices using mortality risk, functional outcome and revision rate as the primary outcome measures. METHODS We performed a retrospective cohort analysis of the New Zealand Joint Registry identifying all primary THRs performed between 1 January 1999 and 31 December 2015. We report this study in accordance with STROBE and RECORD guidelines. We identified all unilateral THRs, all single-anaesthetic bilateral THRs and all staged bilateral THRs and compared the mortality risk, all-cause revision risk with Kaplan-Meier survival analysis and reasons for revision and functional outcome using the Oxford 12 scores. Analysis was adjusted for age, gender, American Society of Anesthesiologists rating score and body mass index. RESULTS The mortality risk for single-anaesthetic bilateral THR within 3 months was 0.26% and for unilateral THR 0.75% (hazard ratio 0.35 (95% confidence interval (CI) 0.30-0.41, P

The surgical management options for bilateral hip osteoarthritis comprise staged or single-anaesthetic bilateral total hip replacements (THRs). The key issue of contention in performing the latter remains safety. We compared unilateral, staged bilateral and single-anaesthetic bilateral THR with the hypothesis that there would be no difference between these three practices using mortality risk, functional outcome and revision rate as the primary outcome measures.We performed a retrospective cohort analysis of the New Zealand Joint Registry identifying all primary THRs performed between 1 January 1999 and 31 December 2015. We report this study in accordance with STROBE and RECORD guidelines. We identified all unilateral THRs, all single-anaesthetic bilateral THRs and all staged bilateral THRs and compared the mortality risk, all-cause revision risk with Kaplan-Meier survival analysis and reasons for revision and functional outcome using the Oxford 12 scores. Analysis was adjusted for age, gender, American Society of Anesthesiologists rating score and body mass index.The mortality risk for single-anaesthetic bilateral THR within 3 months was 0.26% and for unilateral THR 0.75% (hazard ratio 0.35 (95% confidence interval (CI) 0.30-0.41, P 0.001). The risk of revision in the single-anaesthetic bilateral THR group was 0.69/100 component years (95% CI 0.59-0.79/100 component years) versus 0.74/100 component years (95% CI 0.72-0.77/100 component years) in unilateral THR. Mean Oxford 12 scores at 6 months post-arthroplasty was 41.7 (95% CI 41.2-42.2) in the single-anaesthetic bilateral THR group. The best results in the staged bilateral THR group were obtained if the second procedure was delayed by at least 90 days from the first THR.Single anaesthetic bilateral THR is at least as safe as unilateral THR or staged bilateral THR in appropriately selected cases. Experienced surgeons can expect predictable survival rates and functional scores.