Incidence of and Risk Factors for Glenohumeral Osteoarthritis After Anterior Shoulder Instability: A US Population-Based Study With Average 15-Year Follow-up

Background: The rate of osteoarthritis (OA) in patients with a history of previous anterior shoulder instability (ASI) varies within the literature, with the majority of studies investigating rates after surgical stabilization. ASI appears to lead to increased rates of OA, although risk factors for developing OA in cohorts treated nonoperatively and operatively are not well-defined. Purpose: To determine the incidence of clinically symptomatic OA and identify potential risk factors for the development of OA in patients younger than 40 years with a known history of ASI. Study Design: Case-control study; Level of evidence, 3. Methods: An established, geographically based database was used to identify patients in the United States who were younger than 40 years and were diagnosed with ASI between 1994 and 2014. Patient information, including demographic, imaging, and surgical details, was collected. Comparative analysis was performed between groups with and without OA at final follow-up as well as between patients who underwent surgical and nonsurgical management. Results: The study population consisted of 154 patients with a mean follow-up of 15.2 years (range, 5.1-29.8 years). The mean age at initial instability event was 20.9 years (95% CI, 19.9-22.0 years). Overall, 22.7% of patients developed clinically symptomatic glenohumeral OA. Multivariate analysis revealed that current or former smokers (odds ratio [OR], 4.3; 95% CI, 1.1-16.5; P = .030), hyperlaxity (OR, 10.1; 95% CI, 1.4-72.4; P = .020), laborer occupation (OR, 6.1; 95% CI, 1.02-36.1; P = .043), body mass index (BMI) (OR, 1.2; 95% CI, 1.03-1.3; P = .012), and age at initial instability (OR, 1.1; 95% CI, 1.02-1.2; P = .013) as potential independent risk factors when accounting for other demographic and clinical variables. Conclusion: In a US geographic population of patients younger than 40 years with ASI, approximately one-fourth of patients developed symptomatic OA at a mean follow-up of 15 years from their first instability event. When accounting for differences in patient demographic and clinical data, we noted a potentially increased risk for the development of OA in patients who are current or former smokers, have hyperlaxity, are laborers, have higher BMI, and have increased age at initial instability event. Smoking status, occupation, and BMI are modifiable factors that could potentially decrease risk for the development of symptomatic OA in these patients.