Obesity Major Risk Factor for TKA

James J. Nicholson, M.D., director of the Joint Replacement Center at SUNY Stony Brook Medical Center, in an article for Musculoskeletal Network, points out that obese patients fare worse after surgery both because of excess weight on the joint and because adipose cells contribute biochemically to inflammation and pain.

It is well documented, Nicholson notes, that obesity is an independent risk factor for increased post-operative pain, slower recovery and a lower rate of survival of the implant after total knee arthroplasty (TKA) surgery. Half of the patients in the U.S. who undergo TKA surgery have a body mass index higher than 30, making this a major health issue. The hypothesis held by Nicholson and his colleagues is that adipose tissue plays a role as an active endocrine organ causing obese patients who are undergoing total knee surgery to do so in a pro-inflammatory state.

Nicholson reports that his ongoing study has demonstrated that obesity contributes to subclinical systemic inflammation in his TKA population. In a prospective analysis of 38 patients to date, he and his co-researchers found that obese patients scheduled for elective unilateral TKA have significantly higher levels of IL-6 and leptin within the serum than do non-obese patients. These levels, he says, are higher than those observed in ‘normal’ obese patients so he believes it is possible that other inflammatory cytokines promote additional release of leptin from adipocytes. He suggests that if a true causal relationship can be established between the elevation of leptin and pain/function, then preoperative interventions to lower serum leptin levels would be appropriate.

Nicholson is candid to state that that the obese patient considering undergoing a total knee arthroplasty is not the optimal candidate for a physician. He says that doctors should make certain that their obese patients with knee arthritis understand several facts before they undergo TKA.

They need to realize that surgery will not change their obesity. They will continue to gain weight after surgery if they don’t do anything different from what they are presently doing. It is important to set realistic expectations. The surgery will improve the patient’s pain, but it will not solve all their discomfort. They will likely still feel some level of pain on getting out of chairs or climbing stairs and during daily activities. Obese patients must understand that they are at an increased risk for complications. Young obese patients must also realize that their excess weight will likely decrease the lifespan of their implants and that future surgery will probably be needed.