Background:
The use of stemless total shoulder arthroplasty (TSA) for osteoarthritis increases, but there is a paucity on its safety and efficacy and how it performs in comparison with stemmed TSA. The aim was to compare the 5-year cumulative survival rate and patient-reported outcome after stemless and stemmed TSA for osteoarthritis.

Methods:
We included all stemmed (n = 1197) and stemless (n = 253) TSA for osteoarthritis reported to the Danish shoulder arthroplasty registry from January 1, 2014, to December 31, 2018.

Results:
Six (2.4%) stemless and 24 (2%) stemmed TSA were revised. The 5-year cumulative implant survival rates were 0.96 for stemless TSA and 0.97 for stemmed TSA. In the multivariate Cox regression model, the hazard ratio for revision was 1.1 (95% confidence interval, 0.5-2.6) for stemless TSA compared with stemmed TSA. The mean Western Ontario Osteoarthritis of the Shoulder (WOOS) index was 82 (standard deviation = 21) for stemmed and 86 (standard deviation = 19) for stemless TSA. The stemless TSA had a statistically significant better WOOS compared with stemmed TSA, but the difference of 6.2 (95% confidence interval, 1.4-10.4) was not regarded as clinically relevant. There was no difference in WOOS between the Nano and the Eclipse systems.

Discussion:
We found a good 5-year cumulative implant survival rate of stemless TSA, which was comparable with stemmed TSA. Although the stemless TSA had a statistically significant better patient-reported outcome compared with stemmed TSA, the difference was not clinically relevant. Sparing the humeral shaft canal for later revision could be an argument for using stemless TSA instead of stemmed TSA.





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