Little Evidence of Benefit With Short-Term Weight Loss Before Knee Replacement

By Marilynn Larkin

January 25, 2021

NEW YORK (Reuters Health) - Short-term weight loss before a total knee replacement is unlikely to reduce surgical risk or improve outcomes and might contribute to development of sarcopenic obesity, a critical review suggests.

"We anticipated a gap in evidence around this topic, yet we were surprised by the extent of the gap and lack of substantive research," Dr. Kristine Godziuk of the University of Alberta told Reuters Health by email. "Practitioners should be aware of this gap, and share this current uncertainty (lack of evidence) with their patients."

"Practitioners should not make assumptions or decisions based only on a patients' body size or BMI," she said. "We encourage them to have a respectful conversation with the patient about their weight history and prior weight management. The patients' perspective, preferences, and lived-experience should be considered and discussed."

"Practitioners should also contemplate if a weight loss recommendation could contrarily cause harm - e.g., muscle loss and...sarcopenic obesity," she added. "Patients who have both advanced knee osteoarthritis and severe obesity may benefit from more integrated approaches to care, rather than simplistic recommendations to reduce their BMI."

As reported in Joint Bone Spine, Dr. Godziuk and colleagues searched the literature from 2010 to May 2020 to identify systematic reviews, meta-analyses and clinical practice guidelines in three areas: total knee arthroplasty (TKA) complication risk with severe obesity (BMI 40 kg/m2 and above) compared to obesity (BMI 39.9 kg/m2 or less); 2) weight loss recommendations for individuals with advanced knee osteoarthritis; and 3) TKA outcomes after pre-surgical weight loss.

The team identified seven systematic reviews, including five with meta-analyses, specifically examining TKA risk with severe obesity. Most (five) compared severe obesity to no obesity (BMI <30 kg/m2). One review compared BMI groups >40 kg/m2 with <40 kg/m2, reporting an increased odds ratio for infection (4.00) with severe obesity.

Just one review specifically compared TKA risk in severe obesity with obesity, reporting an increased relative risk with severe obesity for perioperative complications (2.85) and five-year implant failure (9.71).

The authors state, "The literature does not show a clear relationship between weight loss and reduction in TKA complications, and no indication that a patients' individual risk is lowered by reducing their BMI from a threshold of 40 kg/m2 (or greater) to 39.9 kg/m2 (or less)."

Studies that did find a benefit of weight loss for knee OA did not include patients with higher BMIs or more advanced knee OA.

"These are important evidence gaps, suggesting that recommendations for BMI reduction prior to TKA should be tempered by the current uncertainty in the literature," the authors conclude.

Dr. Thomas Hickernell, an orthopedic surgeon at NewYork-Presbyterian Medical Group Hudson Valley in New York, commented in an email to Reuters Health, "BMI is clearly an imperfect measure, as it does not take into account patients' varying levels of adipose versus muscle tissue contributions to weight nor their relative metabolic rates."

"However," he noted, "it is a simple measure of height and weight that is readily measurable in every clinical setting, whereas body fat composition or other measures of metabolic activity are not always accessible to the average provider in the clinic."

"Since elevated BMI, especially over 40, has been associated with dramatically increased postoperative complications like wound healing problems and infection, I still use it as a screening tool prior to elective knee replacement surgery," he said.

"However, this is just one portion of preoperative risk screening, where we are also evaluating all their other medical comorbidities and testing for other 'modifiable' risk factors like diabetes control, nutritional markers, anemia, and smoking cessation," he added.

If a patient tries but doesn't succeed in losing weight, he noted, "I will not automatically exclude (them) from surgery as long as they understand and are willing to accept the higher-than-normal risk profile."

"I agree that further research is necessary," he concluded. "In the meantime, I still use BMI above 40 as a soft cutoff for surgical eligibility in an effort to avoid patient harm."

SOURCE: Joint Bone Spine, online December 2, 2021.