Body mass index as a risk factor for dislocation of total shoulder arthroplasty in the first 30 days

BACKGROUND: Dislocation of total shoulder arthroplasty has an incidence as high as 31%. Obesity is one of many proposed risk factors, but no consensus exists on this relationship. The purpose of this study was to determine whether there is a relationship between body mass index (BMI) and dislocation of total shoulder arthroplasty. METHODS: The National Surgical Quality Improvement Program database was used to identify patients older than 50 years who underwent anatomic or reverse total shoulder arthroplasty between the years 2012 and 2016 for primary or secondary osteoarthritis, post-traumatic arthritis, or cuff tear arthropathy. Patients requiring reoperation or readmission for dislocation were identified by Current Procedural Terminology code. The relationship between World Health Organization BMI classification and dislocation was assessed. RESULTS: A total of 9382 patients were identified; 46% were male and 54% female, with an average age of 68.7 years (range 50-90) and average BMI of 31.2 (range 15.1-79.3). There were only 24 dislocation events within the first 30 days after the procedure (0.26%). Ten of 24 (42%) occurred after discharge. Seventy percent of cases (17 of 24) required an open procedure. Underweight patients (BMI < 18.5) experienced the highest dislocation rate (1/50, 2.00%), whereas overweight patients (BMI 25-29.9) experienced the lowest dislocation rate (3/3069, 0.1%). CONCLUSION: The rate of dislocation of total shoulder arthroplasty in the acute postoperative period differs across categories of BMI. However, there does not appear to be a linear association between BMI and risk of dislocation of total shoulder arthroplasty. Further studies are required to elucidate the risk factors for total shoulder dislocation.