Local Subcutaneous Fat Depth Is Associated With Increased Complications After Total Shoulder Arthroplasty.

Background: Increased body mass index (BMI) is a well-documented risk factor for complications after lower extremity arthroplasty. The literature in total shoulder arthroplasty (TSA) displays notable variation. The utility of BMI in predicting complications in TSA may be limited because of differences in weight distribution. Prior studies in spine surgery have demonstrated increased complications based on subcutaneous fat depth at the incision site. The purpose of this study was to determine whether tissue depth may be associated with an increased risk of complication after primary TSA.

Methods: A retrospective study was done on all patients undergoing primary TSA between January 2018 and December of 2021. Postoperative complications of superficial surgical site infection, prosthetic joint infection stress fracture, and implant instability were recorded. Preoperative advanced imaging was used to measure total tissue depth and subcutaneous fat depth at the level of the coracoid and bicipital groove. A combination of univariate and multivariate statistics was used to determine association between tissue depth and postoperative complication.

Results: A total of 219 patients were included in the study. Twenty-nine patients experienced a total of 31 complications. The complication group had a higher percentage of reverse TSA to anatomic. The complication group had a markedly higher depth of subcutaneous fat tissue at the coracoid and bicipital groove (18.82 and 17.53 mm, respectively) compared with the control group (15.05 mm and 11.77; P = 0.046 and P = 0.005). On multivariate analysis, these differences remained statistically significant.

Conclusion: Local subcutaneous fat depth at the coracoid process and bicipital groove was associated with increased rates of complications. In addition, BMI did not demonstrate an association with complications. It is possible that different weight distributions within the upper extremity limit the utility of BMI in risk stratification.

Level of evidence: III.