Obesity is associated with improvement in functional outcome but lower internal rotation after reverse shoulder arthroplasty.

BACKGROUND

The role of obesity as an independent risk factor for increased complications following reverse shoulder arthroplasty (RSA) continues to generate debate. While no standardized body mass index (BMI) cutoff values for shoulder arthroplasty exist, many surgeons are concerned about the potential for poor outcomes and decreased range of motion (ROM) in patients with a high BMI. The purpose of this study was to compare functional outcomes in obese and nonobese patients preoperatively and at short-term follow-up after RSA.

METHODS

A retrospective review was performed of a prospectively maintained, multicenter database of primary RSAs performed by 14 surgeons between 2015 and 2019 with minimum 2-year follow-up. A total of 245 patients met the study criteria, including 111 obese (BMI >30) and 134 nonobese (BMI <30) patients. Patient-reported outcomes (PROs) as well as ROM measurements were compared between the 2 groups.

RESULTS

At baseline, obese patients had significantly lower American Shoulder and Elbow Surgeons (36.6 vs. 42.0,  = .014), Western Ontario Osteoarthritis of the Shoulder scores (33.1 vs. 37.8,  = .043), external rotation at 90° (19° vs. 28°,  = .007), internal rotation (IR) spinal level (L5 vs. L4,  = .002), and belly press strength ( = .003) compared to the nonobese cohort. There were no statistical differences in 2-year outcomes (PROs, ROM, and strength) other than a worse IR (spinal level) in the low BMI group (L4 vs. L3,  = .002). In linear regression analyses controlling for confounding variables, increasing BMI was negatively correlated with preoperative external rotation (B = -0.591,  = .034) and preoperative IR spinal level (B = 0.089,  = .002). Increasing BMI was not correlated with postoperative external rotation at 90° (B = 0.189,  = .490) but was associated with worse postoperative IR by spinal level (B = 0.066,  = .043).

CONCLUSIONS

Obese patients have greater restrictions in external and internal rotation as well as American Shoulder and Elbow Surgeons and Western Ontario Osteoarthritis of the Shoulder scores at baseline prior to RSA. However, there are no major differences in postoperative PROs or ROM measurements between obese and nonobese patients apart from a worse active IR by spinal level in the obese group (L4 vs. L3,  = .002). This study suggests that an RSA procedure does not need to be restricted solely based on BMI.