Background: Mixing and matching components from different manufacturers in total hip arthroplasty is a frequently used off-label praxis. The clinical consequences of this procedure have not been studied in detail. Methods: 860 patients with matched and 1067 patients with mixed primary total hip replacement (THR) components carried out between 1 January 2002 and 31 December 2004, were selected from our Institution registry. The analysis endpoint was set at 1 January 2016. THRs with poorly performing components were excluded from study groups. Kaplan-Meier survival curves for both groups were calculated and compared using the Log-Rank test and the demographic data using the chi-square test. Correlations between demographic data and revisions were calculated using bivariate correlation. Results: 28 revisions were carried out in the matched group and 67 in the mixed group. The 14-year overall survival probability was significantly better in the former (96.0%) than in the mixed group (92.7%) ( p = 0.002). Survival, free of aseptic and septic failures, was statistically, significantly higher in the matched group ( p = 0.026 and p = 0.007, respectively). The survival of the mixed subgroup with heads and stems from the same manufacturer did not differ statistically from that of the matched group ( p = 0.079). Conclusions: In contrast to the results listed in the National Joint Registry and the New Zealand Joint Registry, the survival probability in our study was, statistically, significantly higher in total hip replacements using components of the same manufacturer. Importantly, mixing and matching the components of different manufacturers led to similar survival providing the head and the stem were from the same manufacturer.

Introduction The purpose of the study was to analyse the impact of the COVID-19 pandemic on the healthcare of the orthopaedic patient, i.e. numbers of hip and knee replacement surgeries, 90-day mortality, waiting times and outpatient clinic visits. Methods The Hip (HR) and Knee Replacement (KR) records from The National Arthroplasty Registry of Slovenia in the pandemic year 2020 were compared to the year 2019. To compare reasons for revision and 90-day mortality the Chi-square test was used. The median values of the number of operations and waiting times were compared with the 95% confidence intervals. The number of outpatient clinic visits was tested with the Wilcoxon Signed Ranked test. Results All operations fell by 19%, from 7825 to 6335. The number of Primary Total HR declined from 3530 to 2792 (21%) and the number of Primary KR from 3191 to 2423 (24%). The number of hip revisions declined by 10% and knee revisions by 25%. We did not find differences in 90-day mortality (p=0.408). Outpatient clinic visits fell from 228682 to 196582 (14%) per year. Waiting times increased by 15% for HR and by 12% for KR. Conclusion There was an inevitable drop in the number of surgeries and outpatient clinic visits in the spring and autumn lockdown. With the reorganisation of the orthopaedic service in Slovenia, the number of KR and HR stayed at a relatively high level despite the pandemic. An epidemiological model and mechanisms for the reduction of waiting times could overcome the impact of the epidemic.