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

Summary 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/m2 ; overweight 25.0–29.9 kg/m2 ; obese Class 1 30.0–34.9 kg/m2 ; severe obese Class 2&3 35.0 ≥ kg/m2 ). 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.