Background and purpose — Pooling data on the performance of total knee (TK) implants across registries is only possible if the same TK implant is used across multiple registries and if used in patients with similar characteristics. We assessed to what extent specific TK implants: (i) are used across multiple registries or only in a single registry; and (ii) differ in patient characteristics between registries. Methods — All primary TK implants implanted between January 2020 and December 2021 in the Danish, Dutch, German, and Italian registries were included. We determined the number of registries using a specific TK implant (based on combined femoral-tibial component brand name and fixation/congruency/mobile bearing insert/patella usage). Patient characteristics (age/body mass index [BMI]/sex/ diagnosis osteoarthritis) were compared across registries for TK implants used in ≥ 2 registries ≥ 100 times. Results — 813 different TK implants (577,351 procedures) were used across the 4 registries, of which 53 TK implants (7%) were used in 1 registry (8,000 procedures). 760 different TK implants (569,351 procedures; 99%) were used in ≥ 2 registries of which 47 different TK implants (393,954 procedures; 68%) were used in ≥ 2 registries and ≥ 100 times. Statistically and clinically significant differences in age for the same TK implant across registries were observed for 29 TK implants (62%) and 3 TK implants (6%), respectively; for other characteristics these were for BMI 30 (64%) and 0 (0%) TK implants; for male proportion 23 (49%) and 17 (36%) TK implants; and for diagnosis of osteoarthritis 42 (89%) and 34 (72%) TK implants, respectively. Conclusion — Most specific TK implants and TK procedures were used across multiple registries, but they were often used in patients with different characteristics. This has an impact on comparing implant performances between registries.

Background and purpose — The amount of information publicly available from arthroplasty registries is large but could be used more effectively. This project aims to improve the knowledge concerning existing registries to facilitate access, transparency, harmonization, and reporting. Methods — Within the International Society of Arthroplasty Registries (ISAR) we aimed at developing, testing, adopting, and making publicly available a short, standardized registry description with items considered relevant for stakeholders using a cross-sectional study survey. Items were chosen based on a literature review and expert advice, selected by 9 ISAR working group members, tested iteratively in 3 registries, and commented upon by 4 external experts. All 29 ISAR member registries as of July 2023 were invited to participate in the project. Results — Included items covered general descriptive information regarding registries, information related to governance, outcomes, data quality, data access, and registry production. The template was adopted, completed, and made publicly available by 25 of the 29 registries. Of those, 2/3 were national registries. 23 captured both hip and knee arthroplasties and 10 captured shoulder arthroplasties. Most registries had public reporting of data quality, methods, and results. Data was accessible in all but 2 registries, mainly as aggregated data. Important items relevant to registry quality for researchers to consistently indicate in scientific papers include scope, inclusion criteria, outcomes definitions, coverage/completeness, and validation processes. Conclusion — This ISAR initiative implemented a short, standardized description to facilitate appropriate use of orthopedic registry data worldwide relevant for a diverse group of stakeholders including researchers, industry, public health and regulatory agencies.