Effects of obesity on clinical and functional outcomes following anatomic and reverse total shoulder arthroplasty.

BACKGROUND Limited data exist regarding the clinical and functional outcomes following primary total shoulder arthroplasty in obese patients. The purpose of this study is to determine the effects of obesity on the clinical and functional outcomes following primary anatomic total shoulder arthroplasty (aTSA) and reverse total shoulder arthroplasty (rTSA) in a large patient population with mid-term follow-up. METHODS Patients in a multi-institutional shoulder registry receiving either primary aTSA (n = 1520) or rTSA (n = 2054) from 2004 to 2018 with a minimum follow-up period of 2 years were studied. All patients received the same single-platform shoulder prosthesis. Study groups were assigned based on implant type (anatomic or reverse), and further stratification was based on patient body mass index (BMI), with obese patients having a BMI ≥ 30 and non-obese patients having a BMI < 30. Patients were evaluated and scored preoperatively and at latest follow-up by use of 5 scoring metrics and range of motion (ROM). RESULTS The mean follow-up period was 5 years (range, 2-14 years). Obese patients comprised 41% of the aTSA group and 35% of the rTSA group. Significant postoperative improvements in visual analog scale pain scores, ROM, and all 5 scoring metrics occurred in both obese and non-obese patients (P < .05). Obese patients in both groups reported higher preoperative and postoperative visual analog scale pain scores and less preoperative and postoperative ROM compared with non-obese patients. Compared with non-obese patients, obese patients receiving aTSA reported significantly worse postoperative Simple Shoulder Test, Constant-Murley, American Shoulder and Elbow Surgeons, University of California, Los Angeles, and Shoulder Pain and Disability Index scores compared with non-obese patients, and those receiving rTSA reported significantly worse American Shoulder and Elbow Surgeons and Shoulder Pain and Disability Index scores (all P < .05). However, these differences did not exceed the minimal clinically important difference or substantial clinical benefit criteria. Radiographic analysis showed that in the rTSA group, obese patients had significantly less postoperative scapular notching and a lower scapular notching grade compared with non-obese patients (P < .05). DISCUSSION Both non-obese and obese patients can expect clinically significant improvements in pain, motion, and functional outcome scores following both aTSA and rTSA. Obese patients reported significantly more postoperative pain, lower outcome scores, and less ROM compared with non-obese patients after both aTSA and rTSA at a mean follow-up of 5 years. However, statistically significant differences were not found to be clinically significant with respect to established minimal clinically important difference and substantial clinical benefit criteria. Therefore, obese and non-obese patients experience similar clinical outcomes following total shoulder arthroplasty, regardless of BMI. However, obese patients have more comorbidities, greater intraoperative blood loss, and less scapular notching compared with non-obese patients.