Epidemiology of Glenohumeral Instability Related to Sporting Activities Using the FEDS (Frequency, Etiology, Direction, and Severity) Classification System: A Multicenter Analysis

BACKGROUND: Glenohumeral instability is common in athletes. There are an estimated 0.12 episodes of instability per 1000 sporting exposures. Instability can lead to time away from sport and an increased risk of shoulder arthritis. PURPOSE: To determine the prevalence, demographic data, anatomic features, and likelihood of surgery for the different types of instability as defined by the FEDS (frequency, etiology, direction, and severity) classification system for different sports. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Databases at 3 institutions (University of Iowa, Vanderbilt University, and University of Pennsylvania) were searched for International Classification of Diseases--Ninth Revision codes related to shoulder instability in 2010. Demographic data, symptoms, causes, imaging findings, and operative reports were obtained. Data were entered into a custom-designed REDCap online survey. Patients with subjective instability related to sporting activities were included for analysis. RESULTS: A total of 184 athletes had glenohumeral instability; 20.1% were female. The mean age at the time of the first instability episode was 19.0 years for both male and female patients. The most common sports were football (29.3%), basketball (19.0%), and wrestling (9.8%). The most common type of instability based on the FEDS system was occasional, traumatic, anterior dislocation. Surgery was performed on 69.6% of athletes, and 14.1% had a recurrence of instability after surgery overall. Football had the highest rate of recurrence postoperatively at 23.8%. There was no difference in surgery rates between athletes with subluxations versus dislocations (P = .8458). Surgery was significantly more likely in those with frequent dislocations (P < .0001) and posterior instability (P = .027). There was a 10.7% recurrence rate overall with conservative treatment. CONCLUSION: Glenohumeral instability most commonly occurs in contact sports, affects male more than female patients, and is most frequently in the anterior direction. Recurrent instability is most common in football players. Attention should be turned to the specific characteristics of each type of instability to determine the best treatment for each athlete.