Outcomes of reverse shoulder arthroplasty in patients under 55 years old: Results from the New Zealand joint registry

Background: The appropriate age at which to perform reverse shoulder arthroplasty is controversial. The aim of this study was to compare the outcomes of reverse shoulder arthroplasty between younger and older patients.Methods: Patients who underwent primary reverse shoulder arthroplasty between January 2000 and December 2019 were identified from New Zealand Joint Registry records. Patients were stratified into two cohorts according to age at the time of surgery: < 55 years and >= 55 years. These two groups were then compared with regard to baseline characteristics, indications for surgery, revision rates, and patient-reported outcomes using the Oxford Shoulder Score and American Shoulder and Elbow Score (ASES).Results: A total of 5518 primary reverse shoulder arthroplasty cases were identified, with 75 patients < 55 years at the time of surgery (range: 34-54 years). The mean duration of follow-up was 2.36 years (range: 0.11-13.37 years) in the younger cohort and 3.10 years (range: 0.01-16.22 years) in the older patient cohort. Indications for surgery differed significantly between the two groups, with younger patients having higher rates of inflammatory arthritis (p < 0.001), posttraumatic arthritis (p < 0.001), and avascular necrosis (p = 0.049). The younger cohort had an inferior 6-month postoperative Oxford Shoulder Score compared to the older cohort (mean: 28.5 [younger cohort] vs. 35.7 [older cohort]; p < 0.001). There was no significant difference in revision rate between the younger and older patient cohorts during the study period (1.56 [<55 years] vs. 0.74 [>= 55 years] revisions per 100 component-years; p = 0.332).Conclusion: Our early results suggest that younger patients undergoing reverse shoulder arthroplasty demonstrate high implant retention rates, comparable to older patients. Longer-term patient-reported outcomes in younger patients are required to guide appropriate patient selection for reverse shoulder arthroplasty.