March 19, 2019 / 8:01 PM / a month ago

Study finds weight loss target for morbidly obese before knee surgery

(Reuters Health) - For morbidly obese patients having knee replacement surgery, losing at least 20 pounds beforehand leads to shorter hospital stays and lower odds of being discharged to a facility, a new study has found.

Surgeons often require or strongly suggest that morbidly obese patients lose weight before total knee arthroplasty (TKA), or knee replacement. “Many people are told to lose five or 10 pounds before the surgery but we don’t actually know how much weight you have to lose for it to lead to a meaningful improvement,” Dr. Benjamin Keeney of Geisel School of Medicine, Dartmouth College, in Hanover, New Hampshire, told Reuters Health by phone.

To investigate, he and his colleagues took a look back at 203 patients who were morbidly obese. This meant either they were 100 pounds over their ideal body weight, or their body mass index (BMI), a ratio of weight to height, was 40 or more, or it was 35 or more and they had obesity-related health conditions like high blood pressure or diabetes.

In the three months leading up to TKA, 41 percent of the patients lost at least five pounds, 29 percent lost at least 10 pounds and 14 percent lost at least 20 pounds.

When they had the surgery, 27 patients were no longer morbidly obese, although 23 of those were still severely obese (BMI between 35 and 40).

This week at the annual meeting of the American Academy of Orthopaedic Surgeons in Las Vegas, the researchers reported that compared to patients who did not lose 20 pounds, those who did had 72 percent lower odds of being discharged to a rehab facility and 76 percent lower odds of staying in the hospital for at least four days.

There were no differences in operative time or physical function improvement. Losing five or 10 pounds did not make a difference for any outcome.

Twenty pounds “is the magic number based on our evidence,” Keeney said. “This is even after accounting for age, gender, and other diagnoses besides obesity, as well as baseline physical and mental function.”

It’s also important to note, he added, that people who lost 20 pounds and had improved outcomes were still very obese at the time of surgery. Most of them gained a lot of that weight back but still that weight loss led to better outcomes.

“What this study is telling us - and it’s the first study, so we have that caveat - is that morbidly obese patients who lose at least 20 pounds before knee replacement are going to come home from the hospital faster and are much less likely to go on to be discharged to a facility,” Keeney told Reuters Health.

SOURCE: bit.ly/2tZUoLC American Academy of Orthopaedic Surgeons 2019.

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