Sex-related differences in patients undergoing surgery for shoulder instability: a Multicenter Orthopaedic Outcomes Network (MOON) Shoulder Instability cohort study

Abstract

Hypothesis and background: Male sex has been identified as a risk factor for both primary shoulder dislocation and recurrent instability, and male patients more often undergo surgery for instability. Despite published discrepancies between sexes regarding the incidence and surgical rates of shoulder instability, there is little detail on the differences in presentation, mechanism of injury, and intraoperative findings. The purpose of this study was to explore these differences.

Methods: Prospective baseline data from 1010 patients in the Multicenter Orthopaedic Outcomes Network (MOON) Shoulder Instability cohort were analyzed for sex-related differences using demographic characteristics, patient-reported outcomes, radiographic findings, intraoperative findings, and surgical procedures performed. Two-tailed t tests and χ² tests were used to compare the continuous and categorical data, respectively. Patients were categorized using the Frequency, Etiology, Direction, Severity (FEDS) classification system.

Results: Male patients comprised 81.3% of the cohort. Male patients had a significantly higher rate of traumatic instability and rate of initial instability while playing sports, as well as significantly higher activity scores. Female patients had significantly lower preoperative American Shoulder and Elbow Surgeons, Western Ontario Shoulder Instability Index, 36-Item Health Survey, and Single Assessment Numeric Evaluation scores. No difference in the number of dislocations was found between male and female patients. Intraoperatively, male patients had higher rates of labral pathology and bone loss whereas female patients had higher rates of capsular laxity. These differences resulted in more Latarjet procedures for male patients and more soft-tissue procedures for female patients.

Conclusion: There are differences between male and female patients in the etiology of their instability, baseline patient-reported outcomes, and associated shoulder pathology, likely reflecting intrinsic and activity-related variation. These differences may influence clinical decision making and patient outcomes.

Keywords: FEDS classification; MOON shoulder; Shoulder instability; patient-reported outcomes; sex-based analysis; shoulder instability surgery.