Abstract:

BACKGROUND: Some studies have considered the influence of body mass index (BMI) on the function following total knee replacement (TKR), but the cases were few and follow-up time is short in most of them.

OBJECTIVE: To analyze the function outcome influenced by BMI after TKR.

METHODS: A total of 320 osteoarthritis patients who were admitted in Department of Bone and Joint at Peking University People's Hospital, were involved in this study. They all received primary knee joint patellar resurfacing, including both knees replacement in 200 case of 520 knees, left 219 and right 301. The involved 320 patients underwent primary TKR performed by a single surgeon with the same type of prosthesis (Scorpio posterior stable prosthesis). The patients were divided into four groups based on obesity (overweight group, BMI 25.1-27.0 kg/m²; obese group, BMI 27.1-30.0 kg/m²; morbidly obese group, BMI > 30 kg/m²; control group, BMI < 25 kg/m²). According to the Hospital for Special Surgery (HSS) rating scale, their knee score and functional scores were recorded before replacement and at follow-ups, as well as maximal range of flexion and extension, complications. Preoperative and postoperative assessment was based on the HSS score. 

RESULTS AND CONCLUSION: A total of 320 patients received clinical recheck at 28.3 months (range 12-46 months). Compared with control group, patients in overweight, obese and morbidly obese groups had lower preoperative functional score (P < 0.05), but knee scores were not significantly different for any patient group. The postoperative mean HSS score of all the groups rose significantly at the last follow-up. These differences were not statistically significant among groups (P > 0.05). The rate of perioperative complications was significantly higher in the obese and morbidly obese patients (P < 0.05). Of the 181 knees in obese and morbidly obese patients, 14 knees (9.2%) had a wound complication, 1 knee (0.5%) had an infection, and 2 knees (1.3%) had an avulsion of the medial collateral ligament. The infected case developed within ten weeks after the operation, and was associated with a wound complication. Among 266 knees in the overweight patients, 6 knees (2.3%) had a wound complication. There was 1 knee (1%) of the 81 knees in the control group had a wound complication. No death or pulmonary embolism cases were observed in perioperative period. It is suggested that BMI has no obvious influence on the functional outcome following TKR in the short-term.