Glenosphere Size Does Not Matter in Reverse Total Shoulder Arthroplasty

Objective  There are few studies to date reporting on outcomes following reverse total shoulder arthroplasty with cohorts stratified by glenosphere size. The purpose of this study is to investigate the role that glenosphere size has on postoperative outcomes. Methods  Patients who underwent reverse TSA between 1987 with minimum of 2.0 years of follow-up were included. Patients were stratified into two cohorts based on glenosphere size of 36mm or 40mm. Patients' range of motion, patient-reported outcomes, and radiographic variables (glenoid preoperative morphology, scapular notching, humeral loosening) were evaluated. Results  All measurements of range of motion measurements with the exception of internal rotation saw significant preoperative to postoperative improvements within each cohort. There were no significant differences in postoperative range of motion, ASES, or VAS pain scores across the two cohorts. Overall, forward elevation improved to 134° ± 16° in the 36mm cohort and 133° ± 14° in the 40mm cohort ( p  = 0.47). External rotation improved to 37° ± 13° for 36mm patients and 35° ± 19° for 40mm patients ( p  = 0.58). In the 36mm group, internal rotation increased by 1.3 vertebral levels and 2.3 vertebral levels in the 40mm cohort. At final follow-up, the 36mm cohort had a VAS score of 2 ± 2, ASES score of 66 ± 19, and SST score of 6 ± 3. Similarly, the 40mm cohort had a VAS score of 2 ± 3, ASES score of 77 ± 28, and SST score of 9 ± 3. Conclusions  Reverse TSA provides sustained improvements in range of motion and shoulder function irrespective of glenosphere size. Level of Evidence  III.