Body mass index (BMI) is thought to be a predictor of body composition, with higher values indicating more adipose tissue. BMI is a measure of mass with respect to height. The World Health Organization1 has established health categories based on BMI measurements. Values from 18.5 to 24.9 kg/m2 are deemed to represent normal weight; those from 25 to 30 kg/m2, overweight; and those higher than 30 kg/m2, obesity. BMI is not a perfect tool, but it is the most widely used tool in clinical and research practice because of its relative reliability and ease of use.2 Being overweight or obese (according to BMI) is increasingly common among adults worldwide, and particularly in the United States. An estimated 39% of adults worldwide are overweight, and 13% are obese.1 An estimated 69% of US adults are overweight, including 35.1% who are obese.2
Various pathologies have been treated with reverse shoulder arthroplasty (RSA), and results have been promising,3-9 but little is known about patient demographic and clinical factors that may adversely affect outcomes. Recent work suggests younger age7 and failed prior arthroplasty may adversely affect RSA outcomes.10 Higher BMI has also been implicated as a cause of increased perioperative and immediate postoperative complications of RSA with minimum 90-day follow-up, but no one has examined shoulder function scores at minimum 2-year follow-up.11,12
We conducted a study to examine shoulder function scores, mobility, patient satisfaction, and complications at minimum 2-year follow-up in normal-weight, overweight, and obese patients who underwent RSA. We hypothesized that, compared with normal-weight patients, obese patients would have worse shoulder function scores, worse mobility, and more complications.
Materials and Methods
Inclusion Criteria and Demographics
After obtaining Institutional Review Board approval for this study, we used a prospective shoulder arthroplasty registry to identify patients (N = 77) who had rotator cuff tear arthropathy (RCTA) treated with primary RSA and then had minimum 2-year follow-up. The study period was 2004-2011. All patients had RCTA diagnosed with physical examination findings and anteroposterior, scapular Y, and axillary radiographs. RCTA was graded 1 to 5 using the classification system of Hamada and colleagues.13 Rotator cuff status was determined with preoperative computed tomography arthrogram (CTA) or magnetic resonance imaging (MRI) and confirmed at time of surgery. BMI calculations were based on height and weight measured at initial office visit. Thirty-four patients had normal weight (BMI <25 kg/m2), 21 were overweight (BMI 25-30 kg/m2), and 22 were obese (BMI >30 kg/m2). Patient demographic and clinical characteristics reviewed also included age, sex, follow-up duration, arm dominance, complications, prevalence of depression, and prevalence of diabetes. All RSAs were performed by the same surgeon (Dr. Edwards) at a single high-volume shoulder arthroplasty center.
Shoulder function scores evaluated before surgery and at final follow-up included Constant score,14 American Shoulder and Elbow Surgeons (ASES) score,15 Western Ontario Osteoarthritis Shoulder (WOOS) index,16 Single Assessment Numeric Evaluation (SANE),17 and mobility. Satisfaction was assessed by having patients describe themselves as very dissatisfied, dissatisfied, satisfied, or very satisfied. All intraoperative and postoperative complications were recorded.
Surgical Technique and Postoperative Rehabilitation
The Aequalis RSA system (Tornier) was used for all patients during the study period. The RSA technique used has been well described.18,19 A standard postoperative rehabilitation protocol was followed.19,20
Clinical and Radiographic Assessment
Patients were prospectively enrolled in a shoulder arthroplasty outcomes registry and followed clinically. Mean follow-up was 3.16 years (range, 2-8 years). Before surgery, patients were examined by the surgeon. Examinations were repeated 1 week, 6 weeks, 3 months, 6 months, and 12 months after surgery and annually thereafter. Mobility (active range of motion) was determined with a handheld goniometer. Strength of abduction was measured with a handheld digital dynamometer (Chatillon digital force gauge, 200 lbf; Ametek). Anteroposterior in plane of scapula, scapular Y, and axillary radiographs were obtained at each clinic appointment.
Before surgery, the surgeon reviewed all radiographs. Each RCTA was given a Hamada grade (1-5).13 Glenoid erosion in the coronal plane was classified (E0, E1, E2, E3) according to Sirveaux and colleagues.21 Hamada grades and glenoid erosion types are listed in Table 1. The overall trend in classification by BMI group was statistically significant for Hamada grade (P = .004) but not glenoid erosion type (P = .153).
Before surgery, the surgeon also evaluated rotator cuff status using CTA or MRI. All patients had full-thickness tears of the supraspinatus and infraspinatus. The subscapularis was variably present, and subscapularis repair was performed when the subscapularis was intact. Rotator cuff status is listed in Table 2. There were no significant differences in the distribution of intact subscapularis (P = .402) or teres minor (P = .188) among the normal-weight, overweight, and obese groups. No patient had a latissimus dorsi transfer at time of RSA.
