The study was designed to assess the benefits of weight loss before total knee arthroplasty in patients with morbid obesity (body mass index 40 kg/m2 or higher). "Many surgeons require or request weight loss among morbidly obese patients before total knee arthroplasty," the researchers write. That concern reflects consistent evidence showing increased rates of adverse outcomes in severely or morbidly obese patients.
Dr. Jevsevar and colleagues reviewed data on 203 morbidly obese patients who underwent total knee arthroplasty between 2011 and 2016 at one medical center. This group accounted for 13.5 percent of approximately 1,500 patients who underwent knee replacement during that time.
In the months before the procedure, 41 percent of patients lost at least five pounds, 29 percent lost at least 10 pounds, and 14 percent lost at least 20 pounds. The researchers compared the outcomes of each preoperative weight-loss group with those of patients who did not lose weight.
Several outcomes were improved in patients who lost 20 pounds or more, but not in those who lost five or 10 pounds. After adjusting for other factors, the researchers found that patients who lost at least 20 pounds spent about one fewer day in the hospital and were 76 percent less likely to have an extended hospital stay of four days or longer. Weight loss of at least 20 pounds was also associated with a 72 percent reduction in the odds of being discharged from the hospital to a facility.
Preoperative weight loss was not associated with change in operative time or with postoperative improvement in physical health and function. Length of hospital stay and operative time were significantly increased for patients who gained weight before surgery.
Most patients who lost 20 pounds or more remained in the morbidly obesity category, the researchers note, and patients displayed "general and expected" postoperative weight gain, with the mean weight almost returning to the preoperative baseline.
Although morbid obesity is associated with increased surgical risk, it remains unclear whether preoperative weight loss can improve outcomes following total knee arthroplasty. Dr. Jevsevar and coauthors note that larger, multicenter center studies are needed to confirm their findings.
Meanwhile, this study provides orthopaedic surgeons with new evidence that weight loss of 20 pounds or more - even if only temporary - can improve length-of-stay outcomes and reduce costs of total knee arthroplasty in morbidly obese patients.