Delineating the impact of obesity and its relationship on recovery after total joint arthroplasties.

OBJECTIVE: The primary aim of this study was to determine the impact of obesity in predicting short and long-term pain relief and functional recovery in total joint arthroplasty (TJA) either as an independent risk factor or a factor mediated by two chronic conditions associated with obesity-cardiac disease and diabetes mellitus.

METHOD: A prospective observational study of 520 patients with primary joint arthroplasties. Pain and functional outcomes were evaluated with the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index within a month of surgery and then 6 months and 3 years post-operatively. Obesity, cardiac disease and diabetes mellitus were examined as potential risk factors for poor recovery. Patients were classified into four groups based on body mass index (BMI): (normal<25.0 kg/m(2); overweight 25.0-29.9 kg/m(2); obese Class 1 30.0-34.9 kg/m(2); severe obese Class 2&3 35.0 ≥ kg/m(2)). Linear mixed models for each joint type (hip and knee arthroplasty) were developed to examine the pattern of recovery and the effect of obesity.

RESULTS: Ninety-nine (19%) patients were severely obese, 127 (24%) had cardiac disease and 58 (11%) had diabetes mellitus. Baseline pain and functional scores were similar regardless of BMI classification. Severe obesity was a significant risk factor for worse pain and functional recovery at 6 months but no longer at 3 years following total hip and knee arthroplasty. Cardiac disease predicted a slower recovery after hip arthroplasty. No significant interactions existed between obesity and cardiac disease or diabetes mellitus.

DISCUSSION: Severe obesity is an independent risk factor for slow recovery over 3 years for both hip and knee arthroplasties.