TKA short-lived in overweight patients - Academy News at the 2007 AAOS Annual Meeting

TKA short-lived in overweight patients

By Carolyn Rogers

As patient weight and body mass index (BMI) increase, longevity of total knee arthroplasty (TKA) decreases, according to poster exhibit P163. Higher BMI and weight are also predictive of worse physical functional outcomes in TKA revision.

Although conventional thinking has implicated weight and BMI in premature failure of TKA, scant evidence of this belief exists in the literature. To assess the effect of weight on the longevity and outcomes following TKA revision, researchers conducted a 17-center prospective study of 186 patients undergoing TKA revision.

For each patient, data was collected on weight, BMI, and time elapsed between primary and revision surgery. The Physical Component Score (PCS) of the Short Form-36 (SF-36), the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index, and the Knee Society Score (KSS) were collected preoperatively and at six-month follow-up. Univariate, bivariate and multivariate statistical methods were used in the analysis.

Patients had a mean BMI of 31.8 (54 percent of patients had a BMI less than 30); the mean weight was 200 pounds (range: 107 pounds to 350 pounds). The distribution of both measures of excessive weight was close to normal. Average time between primary and revision procedures was 7.3 years, and ranged from 6 months to 27 years.

Using linear regression, researchers found that the time between primary TKA and revision TKA significantly decreased as weight and BMI increased. Mean SF-36 PCS, WOMAC and KSS-Function scores were significantly improved six months after revision surgery. However, BMI and weight were predictive of worse physical functional outcomes.

Although further prospective data regarding this population is indicated, the current findings should direct orthopaedic surgeons toward more accurate outcomes prediction for overweight patients.

The lead researcher for poster exhibit P163 is Khaled J Saleh, MD, of Charlottesville, Va. Additional researchers on the team include Kevin James Mulhall, MD, of Dublin, Ireland; Quanjun Cui, MD, and William Michael Mihalko, MD—both of Charlottesville, Va. Dr. Saleh received research support and serves as a consultant to Styker and Smith+Nephew; he has also receives royalties from Smith+Nephew; Dr. Mihalko has received research support and is a consultant to Styker.


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