A comparative analysis of a central metaphyseal humeral fixation stemless shoulder arthroplasty to an anatomic shoulder arthroplasty in a national registry cohort

Background: This study aimed to determine the revision outcome between a centrally fixed stemless anatomic design and other total anatomic shoulder replacements using data from a large national arthroplasty registry. Methods: The study period was from December 2011 to December 2022 and included three cohorts; primary Affinis stemless anatomic (AFS), all other primary total stemless anatomic (sTSA) and primary total stemmed anatomic shoulder arthroplasty (aTSA). The endpoint was all-cause revision using cumulative percent revision (CPR). Hazard ratio (HR) models were adjusted for age and gender. Results: There were 2489 primary AFS, 1593 primary sTSA and 11,023 primary aTSA. There was no difference in revision rates between the AFS and the sTSA group. The aTSA group had a significantly higher rate of revision compared to both AFS (HR = 1.63, 95% confidence interval (CI) 1.30–2.05, p < 0.001) and sTSA (HR = 1.61, 95% CI 1.21–2.15, p = 0.001). However, sub-analyses stratifying for highly crosslinked polyethylene (XLPE) showed no differences between the groups. Discussion: The rates of revision between the AFS design and other stemless prostheses were similar. Stemless had lower revision rates to aTSA. When only considering XLPE cemented glenoids, there was no significant difference in revision rates.