International variation in shoulder arthroplasty.

Background and purpose - The number of shoulder registries increases. We assessed international trends in use of shoulder arthroplasty, and described the current state of procedure selection and outcome presentation as documented in national and regional joint registries. Methods - Published reports from 9 population-based shoulder arthroplasty registries (country/region: Norway, Sweden, New Zealand, Denmark, California, Australia, Emilia-Romagna, Germany, and United Kingdom) were analyzed. Data were extracted on age, sex, disease indication, type of surgical procedure, surgical volume, and outcomes. Results - Shoulder arthroplasty incidence rate in 2012 was 20 procedures/105 population with a 6-fold variation between the highest (Germany) and lowest (United Kingdom) country. The annual incidence rate increased 2.8-fold in the past decade. Within the indications osteoarthritis, fracture, and cuff-tear arthropathy variations in procedure choice between registries were large. Outcomes evaluation focused on revision in all registries, but different measures and strata were used. Only Australia provided revision rates for prosthesis brands stratified by both indication and procedure. Finally, in 2 registries with available data surgeons performed on average 10-11 procedures yearly. Interpretation - Annual incidence rates of shoulder arthroplasty have almost tripled over the past decade. There is wide variation in procedure selection for the major indications, a low average surgeon volume, a substantial number of brands with small annual volume, and large variation in outcome presentation. The internationally increasing registry activity is an excellent basis for improving the so far weak evidence in shoulder arthroplasty.