Abstract
Purpose
The purpose of this study was to compare the outcomes and complications of normal weight, class one obese (BMI=30-34.9 kg/m2) and superobese (BMI≥50 kg/m2) primary total knee replacement (TKR) patients.
Method
Between January 1995 and December 2005, 4104 primary TKR were performed in our centre. Patients were stratified for their obesity level according the World Health Organisation (WHO) and current surgical literature classification. Sixty-seven superobese patients (group one) were identified. They were matched with normal weight (group two) and class one obese (group three) primary TKR patients for sex, age, side, preoperative diagnosis, implants used, time since surgery and preoperative SF-12 mental component summary score (MCS). Patient clinical outcomes (WOMAC, SF-12 and Knee Society scores), radiographs, complications, readmissions, and revisions rates were compared for normal BMI, class one obese and superobese patients.
Results
The mean BMI of our primary TKR patients was 32,6. Using the WHO BMI classification, 0.3% were underweight, 10.4% normal weight, 30.1 % overweight, 31.0 % class 1 obesity, 16.5 % class 2 obesity, 9.8 % class 3 obesity and 1.9 % superobese. Superobese population (n=67) was 61.59.2 yo, with sex ratio at 5.1 (F=56;M=11), preoperative SF-12 MCS at 52.610.6. Their preoperative diagnosis was osteoarthritis (n=62) or inflammatory arthritis (n=5). All groups were equal (n=67) and were similar for these characteristics. Mean clinical and radiographic follow-up was 7.33.2 yrs. Superobese patients presented lower preoperative SF-12 physical component summary (PCS; gp 1=26.05.6; gp 2=29.68.4; gp 3=30.57.8; p<0.05), Knee Society score (gp 1=73.626.4; gp 2=84.926.5; gp 3=88.517.4; p<0.05) and WOMAC scores (gp 1=35.814.5; gp 2=44.116.7; gp 3=41.315.7; p<0.05). However the three groups presented a similar improvement of the SF-12 PCS (gp1=10.512.0; gp2= 6.810.9; gp3=6.812.1; p= 0.22) and Knee Society score (gp1=81.930.8; gp 2= 74.220.9; gp 3=78.729.9; p= 0.21). The superobese patients group had a significantly longer hospital stay, higher complication rate, and were more frequently re-admitted to hospital and submitted to revision surgery.
Conclusion
Superobese patients can enjoy comparable clinical outcomes when compared to patients with lower BMIs, but do run increased risks in terms of a complication and a greater hospital re-admission rate.
