20-lb Weight Loss Improves TKA Outcomes in Obese

A new study has found that morbidly obese patients who dropped at least 20 pounds before total knee arthroplasty (TKA) had a shorter length of stay in the hospital and a reduced chance of having to go to a nursing facility—even if they remained morbidly or severely obese.

The study, “How Much Preoperative Weight Do Morbidly Obese Patients Undergoing Total Knee Arthroplasty Need to Lose to Meaningfully Improve Outcomes?” was recently presented at the 2019 Annual Meeting of the American Academy of Orthopaedic Surgeons.

David S. Jevsevar, M.D., M.B.A., senior author and chair of Orthopaedics at Dartmouth-Hitchcock Medical Center and the Geisel School of Medicine, explained the rationale for the study to OTW, “Every orthopaedic surgeon who performs hip and knee arthroplasty struggles with the appropriate course of treatment for morbidly obese patients with hip and knee arthritis. We all recognize that obesity is a modifiable risk factor. We also have heard our obese or morbidly obese patients tell us that they will lose weight before surgery in an attempt to improve their outcomes.”

The authors described their methodology, “…we identified 203 patients who were morbidly obese at least 90 days before surgery and had their BMI measured again at the immediate preoperative visit. All heights and weights were clinically measured. Of these 203, 41% lost at least 5 pounds before surgery, 29% lost at least 10 pounds, and 14% lost at least 20 pounds. Twenty-seven patients (13%) were no longer morbidly obese, although 23 of those still remained severely obese (BMI between 35 and 40)…”

They found that individuals who were morbidly obesity and lost 20 pounds before TKA had lower odds of being discharged to a nursing facility, lower odds of an extended length of stay of at least four days and an absolute shorter length of stay compared to patients who did not lose 20 pounds. There was no difference in the length of surgery or improvements in physical function.

Dr. Jevsevar noted, “Our work may also reflect weight loss as being a surrogate for patient activation and engagement, which have been shown to have significant impact on outcomes in this patient population.”

He told OTW that certain results from the study surprised him. “We were surprised at the number of arthroplasties that were performed in morbidly obese patients during the time-frame of our review. We were also surprised that a relatively small amount of weight loss could impact the outcomes of interest.”

Asked about challenges in conducting this study, Dr. Jevsevar said, “At Dartmouth-Hitchcock, we have a robust outcomes database for hip and knee arthroplasty that started in 2011. We also have never implemented a strict BMI [body mass index] cut-off for these procedures, which made this retrospective review possible.”

“Our study shows that even a relatively small amount of weight loss improved outcomes. While our study demonstrates this correlation between weight loss and improved outcomes, it does not provide evidence for the source of this improvement. It would intuitively seem that the small amount of weight loss seen in our study participants would not cause significant physiological improvement. Rather, our results may be reflective of the effect of patient activation and engagement on outcome. Further prospective study is needed to define the causation for the improved outcomes that we observed.”