TKA No Way to Lose Weight

Researchers at Singapore General Hospital, in a study reported at the recent meeting of American Academy of Orthopaedic Surgeons (AAOS) in Las Vegas, found that most patients do not lose weight following a total knee arthroplasty (TKA).

The researchers analyzed 7, 733 patients with tricompartmental osteoarthritis of the knee who underwent primary TKAs. The researchers followed the patients for up to two years. They considered a change of at least 5% from the patient’s preoperative BMI to be clinically significant for the study. Researcher Jerry Chen, M.D., of Singapore General Hospital, said, “This is the minimum reduction in BMI required to induce metabolic and cardiovascular health benefits.”

Unlike other investigators of this topic, the Singapore researchers took into consideration the natural weight gain of adults over time. They corrected the post-operative BMI scores by subtracting this yearly increase for a given age.

After TKA surgery, 1, 067 patients, about 14%, had a reduction in their BMI. Five patients maintained their pre-surgery BMI and 1, 621 patients, 21%, had a gain in their BMI. Most patients either gained weight or stayed the same.

Researchers found that patients with a higher preoperative BMI were more likely to reduce their BMIs following surgery. There was no association between the patient’s age at time of surgery or gender. The authors speculate that the reason patients gained weight following surgery was because they gained increased muscle mass from increased physical activity.

Conversely, they reasoned that the reduction in BMI, instead of resulting from improved metabolic health, may have been the result of decreased lean body mass because of failing health and the onset of comorbidities.