Washington , DC (Feb. 23) - New research appears to refute the common perception that obese patients with lower extremity arthritis will lose weight after arthroplasty. The findings were presented on Wednesday during a poster session at the 72^nd Annual Meeting of the American Academy of Orthopaedic Surgeons.

In a prospective study of 100 consecutive osteoarthritis (OA) and rheumatoid arthritis (RA) patients who underwent hip or knee replacement, patients gained an average of nearly three pounds during at least 1 year of follow-up. The results suggest that obesity in these patients cannot be explained by physical inactivity due to joint disability.

"Obesity is a major problem," study author Thomas P. Schmalzried, MD, associate director of the Joint Replacement Institute at the Orthopaedic Hospital in Los Angeles, California, tells CIAOMed. He adds that it is a natural assumption among patients that they are inactive and cannot exercise because of their arthritis, and that their inactivity is the reason their body weight increases. "That rationale is incorrect. These patients do not lose weight after surgery."

Dr. Schmalzried was not surprised by his findings. "I have been taking care of arthritic patients for 15 years and have seen so many patients that had clearly rationalized their obesity as due to hip or knee arthritis...and I had watched them after surgery long enough to know that they don't lose weight," he says.

The study cohort comprised 34 males and 66 females aged 23 to 82. Of these, 91 had OA and 9 had RA. In the group, 55 were classified as obese (defined as a body mass index [BMI] of greater than or equal to 30), 31 were overweight ( BMI of 25-29.9), and 14 were in the normal range.

Both total knee replacement (TKR) and total hip replacement (THR) patients gained weight during the study. The overweight patients gained the most weight following surgery, and, in fact, 9 went from being overweight to obese during the study period.

The 19 patients who had resurfacing arthroplasty tended to gain more weight than other patients, as did patients with RA, and patients who had only one joint involved and in whom no other conditions interfered with their walking. Dr. Schmalzried points to these results as evidence that obesity in these patients is not a consequence of arthritis. "Obesity needs to be addressed as an independent disease process," he stresses.

A Catch-22

Michael A. Mont, MD, director of the Center for Joint Preservation and Reconstruction at Sinai Hospital in Baltimore tells CIAOMed that obese patients do worse after TKR - even if they are active.

"If you really want your results to be optimized, don't be obese," he says. Noting that this is easier said then done, Dr. Mont points out that "if a patient could lose weight, they could get optimal results, but a lot of these patients can't wait [for surgery], and they are not going to walk if they are in pain."

"The perfect patient would get in a pool, exercise, lose weight, and stay healthy

before and after the surgery," he says, adding that crash diets are not recommended because nutritional shortfalls can increase the rate of complications.

Reference:

Schmalzried TP, Heisel C, Silva M, DeLaRosa MA. Surgical Treatment of Hip or Knee Arthritis Does Not affect Obesity/ Poster No 053. 72^nd Annual Meeting of the American Academy of Orthopaedic Surgeons; February 23-27, 2005. Washington, DC