Body mass index and the impact on hospital resource use in patients undergoing total knee arthroplasty.

We identified all total knee arthroplasty patients between 1996 and 2004 and classified them by preoperative body mass index (BMI) as normal (BMI, 18.5-24.9 kg/m(2)), overweight (BMI, 25.0-29.9 kg/m(2)), obese (30-34.9 kg/m(2)), or morbidly obese (≥ 35.0 kg/m(2)). Of 5521 patients, 769 had a normal BMI, 1938 were overweight, 1539 were obese, and 1275 were morbidly obese. Adjusted length of stay was no different between normal (4.85 days), overweight (4.84 days), obese (4.86 days), or morbidly obese patients (4.93 days) (P = .30). Overall costs were similar among normal ($15,386), overweight ($15,430), obese ($15,646), or morbidly obese patients ($15,752) (P = .24). Postsurgical costs were no different among normal ($9860), overweight ($9889), obese ($10,063), or morbidly obese patients ($10,136) (P = .44). Our results suggest that increased BMI does not lead to increased hospital resource use for total knee arthroplasty.