Obesity Has Minimal Impact on Short-Term Functional Scores After Reverse Shoulder Arthroplasty for Rotator Cuff Tear Arthropathy
The potential adverse effect of body mass index (BMI) on shoulder function scores after reverse shoulder arthroplasty (RSA) has not been investigated.
We conducted a study to examine outcomes of RSA performed for rotator cuff tear arthropathy (RCTA) across BMI categories (normal weight, overweight, obese). We hypothesized that, compared with normal-weight patients, obese patients would have worse shoulder function scores, worse mobility, and more complications.
Using a prospective shoulder arthroplasty registry, we identified 77 primary RSAs performed for RCTA with minimum 2-year follow-up. 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). Shoulder function scores, mobility, and satisfaction were evaluated before surgery and at final follow-up.
The 3 BMI groups were not significantly different on demographic factors, preoperative shoulder function scores, or preoperative mobility (P > .05). For each group, shoulder function scores and mobility significantly improved between the preoperative and final follow-up assessments (P < .001). Patient satisfaction was similar between groups (P = .967).
Improved shoulder function scores, mobility, and patient satisfaction can be expected after RSA for RCTA in patients regardless of BMI.
Statistical Analysis
Independent-samples t tests assuming unequal variances were used to compare the 3 BMI groups on age, follow-up duration, preoperative shoulder function scores, and mobility. Chi-square tests were used to identify any significant group differences in comorbidities (eg, complications, arm dominance, prevalence of depression, prevalence of diabetes) and patient satisfaction. Repeated-measures analysis of variance was used to evaluate main effects, changes from before surgery to final follow-up, and BMI group differences, as well as differences in changes from before surgery to final follow-up among the 3 BMI groups.
Results
Among BMI groups (<25 kg/m2, 25-30 kg/m2, >30 kg/m2), there were no statistically significant preoperative differences in age, sex, follow-up duration, complications, arm dominance, prevalence of depression, or prevalence of diabetes (P >. 05) (Table 3). Table 4 lists the groups’ preoperative and final follow-up data (Constant score, ASES score, WOOS index, SANE, mobility). There were no statistically significant preoperative group differences in Constant score, ASES score, WOOS index, SANE, mobility, or patient satisfaction (P > .05) (Tables 5, 6).
All groups’ shoulder function scores and mobility improved significantly from before surgery to final follow-up (P < .001) (Table 5). The groups’ magnitudes of change (improvement) from before surgery to final follow-up were almost identical, with no significant differences in shoulder function scores or mobility (Table 5). The only significant difference was in Constant–Strength, which was higher in the obese group (P = .017) (Table 5). Patient satisfaction ratings improved after surgery, with 79% of the normal-weight group reporting being satisfied or very satisfied with their shoulders (Table 6). The overweight and obese groups gave similar satisfied (81%) and very satisfied (82%) ratings. The small differences between group satisfaction scores were nonsignificant (P = .967).
Complications
The normal-weight group had 4 complications: periprosthetic infection (2 cases), intraoperative humeral fracture (1), and scapular spine stress fracture (1). The overweight group had 1 complication, an acromial stress fracture that was successfully treated with conservative measures. The obese group had 1 patient with 2 postoperative dislocations. The first dislocation was treated with closed reduction and bracing, and the second required revision surgery. There was no statistical difference in complications among the groups (P = .680).
Discussion
To our knowledge, this is the first study of the effects of varying BMI on functional outcomes of RSA with minimum 2-year follow-up. There appears to be minimal impact on shoulder function scores, complications, and patient satisfaction among normal-weight, overweight, and obese patients with RCTA treated by the same surgeon using similar techniques.
The relationship between obesity and increased perioperative risks or poorer surgical outcomes has been well established in orthopedic surgery. In a systematic review, Falagas and Kompoti22 found increased risk for perioperative and nosocomial infections in obese patients. Schoenfeld and colleagues23 and Jiang and colleagues24 reported increased risk for complications in spinal surgery. The total joint arthroplasty literature is rife with evidence suggesting higher BMI leads to increased risk for complications, including infection and deep venous thrombosis, as well as decreased functional outcome scores.25-29 Recent studies on shoulder surgery have shown worse outcomes in rotator cuff repair30 and a higher revision rate in hemiarthroplasy.31
Other RSA studies have examined short-term complications or perioperative risk factors associated with BMI. In a study using slightly different BMI groupings, Gupta and colleagues12 reported significantly higher complication rates for RSA patients with BMI higher than 35 kg/m2 compared to patients with BMI of 25 to 35 kg/m2 and compared to patients with BMI lower than 25 kg/m2. Their study highlighted medical and surgical complications and used a short follow-up period (minimum, 90 days). It did not assess shoulder function scores, and included multiple indications for RSA (eg, RCTA, proximal humerus fracture, inflammatory arthropathy). In another study, higher BMI was reported as a risk factor for early dislocation after RSA, but only 11 patients with a history of dislocation were assessed, and minimum follow-up was 6 months.32 We know of only one study that addressed RSA outcomes in obese patients and used minimum 2-year follow-up, but its primary endpoint was rate of complications, and it did not report shoulder function scores.11 Li and colleagues33 conducted a study similar to ours, but with primary total shoulder arthroplasty (TSA) patients, and reported similar results. Relative to normal BMI, higher BMI did not have a detrimental effect on short-term improvement in shoulder function after TSA.
Given the US obesity epidemic, our study results are encouraging. Depending on many factors, obesity remains a risk factor for poor outcomes in patients who undergo orthopedic surgery. As our results show, however, patients with higher BMI can obtain functional outcomes similar to those experienced by patients with normal-weight BMI after RSA for RCTA.
