Differences in outcomes of obese women and men undergoing primary total hip arthroplasty

Obese patients tend to have a higher prevalence of total hip replacements due to a higher incidence of hip osteoarthritis. This is of particular concern in light of the trend in rising rates of obesity in developed countries.

A new study published in the March 2007 issue of Arthritis Care & Research evaluated the effects of obesity on complications and outcomes following total hip replacements and investigated whether the results differed in obese women and men.

Led by Anne L?bbeke, M.D., MSc, of the Geneva University Hospital in Geneva, Switzerland, researchers conducted a study of all patients who underwent total hip replacements between March 1996 and July 2005 at their hospital. Of the 2,495 hip replacements (some were bilateral), 589 were performed in obese patients, with a higher prevalence of obese males than females. Obesity was defined as a body mass index equal to or greater than 30 kg/m2. Researchers evaluated the incidence of infection, dislocation, and revision (redoing the replacement), as well as quality of life, satisfaction, and general health five years after undergoing a hip replacement.

The results showed that obesity was associated with a substantially higher risk for infection in women, led to more dislocations (with a greater increase in women), and resulted in more revisions due to septic loosening (caused by infection). After five years, outcomes for 635 hips in non-obese patients and 183 hips in obese patients were evaluated. Obese women, but not obese men, reported moderately lower functional outcomes and slightly less satisfaction, mostly due to a higher incidence of complications.

The risk factors for infection that are known to be more frequent in obese patients, such as longer operating time and diabetes, were not related to females in the study and do not explain why the women had poorer results. The researchers suggest that other reasons related to sex differences, such as body fat distribution and metabolic response, might be involved. They also note that the higher number of dislocations in obese women may be due to the lower peripheral muscle strength seen in this group of patients, while the lower functional outcomes may be due to additional factors such as a higher incidence of osteoarthritis.

"To the best of our knowledge, this is the first study analyzing sex differences as related to outcomes in obese THA [total hip replacement] patients," the authors state. They note that previous studies on the relationship between obesity, complications, and outcomes following hip replacement are contradictory, but the results are muddied by a lack of information on sex, multiple definitions of obesity, and a limited interpretation of complications. "Because our study revealed increased complications among obese women, we suggest that surgeons counsel this group of patients so that they are made aware of this fact," the authors conclude. "In addition, participating in a weight-loss program prior to surgery might be beneficial for such patients."

http://www.interscience.wiley.com/journal/arthritiscare