Risk Factors for Posterior Shoulder Instability in Young Athletes

Background:While posterior glenohumeral instability is becoming increasingly common among young athletes, little is known of the risk factors for injury.Purpose:To determine the modifiable and nonmodifiable risk factors for posterior shoulder instability in a high-risk cohort.Study Design:Case-control study (prognosis); Level of evidence, 2.Methods:A prospective cohort study in which 714 young athletes were followed from June 2006 through May 2010 was conducted. Baseline testing included a subjective history of instability, instability testing by a sports medicine fellowship–trained orthopaedic surgeon, range of motion, strength measurement with a handheld dynamometer, and bilateral noncontrast magnetic resonance imaging of the shoulder. A musculoskeletal radiologist measured glenoid version, height, depth, rotator interval (RI) height, RI width, RI area, and RI index. Participants were followed to document all acute posterior shoulder instability events during the 4-year follow-up period. The time to the...