A history of shoulder instability is more common in young patients undergoing total shoulder arthroplasty

Background: Previous studies have shown an association between shoulder instability and the development of glenohumeral arthritis leading to total shoulder arthroplasty (TSA). The primary goal of this study was to evaluate if a history of shoulder instability was more common in patients aged <50 years undergoing TSA. The secondary objective was to determine if a history of prior surgical stabilization is more common in patients aged <50 years undergoing TSA. Methods: Using the military health system data repository (MDR) and the Military Analysis and Reporting Tool (M2), we identified 489 patients undergoing primary TSA from October 1, 2013, to May 1, 2020, within the Military Health System (MHS). Patients aged <50 years were matched 1:2 with patients aged >50 years based on sex, race, and military status, with the final study population comprising 240 patients who underwent primary TSA during the study period. Electronic medical records were examined, and factors showing univariate association (P < .2) were included in a binary logistic regression analysis to determine associations between demographic or clinical factors and TSA prior to age 50 years. Results: The groups differed significantly in shoulder arthritis subtype, with the older group having significantly more primary osteoarthritis (78% vs. 51%, P < .001). The younger group had significantly more patients with a history of shoulder instability (48% vs. 12%, P < .001), prior ipsilateral shoulder surgery of any type (74% vs. 34%, P < .001), and prior ipsilateral shoulder stabilization surgery (31% vs. 5%, P < .001). In the resultant logistic regression model, a history of shoulder instability (OR 5.0, P < .001) and a history of any prior ipsilateral shoulder surgery (OR 3.5, P < .001) were associated with TSA prior to the age of 50 years. Conclusions: Shoulder instability is a risk factor for TSA before age 50 years. It is unclear how surgical stabilization influences the development of secondary glenohumeral arthritis in shoulder instability. Patients should be counseled that recurrent instability could lead to earlier TSA, regardless of whether surgical stabilization is performed. Level of evidence: Level III; Retrospective Cohort Comparison; Prognosis Study Published by Elsevier Inc. on behalf of Journal of Shoulder and Elbow Surgery Board of Trustees.