BMI cited as poor predictor of early complications after TJA

DALLAS — Results of a database review study presented here indicated a correlation between increased body mass index and 30-day complications for total joint arthroplasty; however, body mass index was not a strong predictor of this risk, according to the presenter.

“An increase in BMI confers an increased risk of early postoperative complications for primary arthroplasty patients, but the absolute risk difference is low until BMI gets over 50,” Derek T. Ward, MD, said during his presentation at the American Association for Hip and Knee Surgeons Annual Meeting. “BMI is a relatively poor predictor of risk.”

The review comprised 22,808 patients from the Veterans Affairs Surgical Quality Improvement Program database who underwent primary total joint arthroplasty (TJA) from 2006 to 2009. Ward noted 5,000 patients had a body mass index (BMI) greater than 40 and of those, 400 had a BMI greater than 50.

The researchers found that as BMI increased, age trended down and operative time increased. Increased BMI was also linked with a trend for increased intraoperative transfusion with total hip but not total knee arthroplasty, and there was also a trend toward discharge to a facility. There was no difference in length of stay, according to Ward.

In addition, Ward and colleagues discovered a statistically significant association between increasing BMI and combined 30-day complications.

“It is important to note that the actual incidence increase is no greater than 3% for any of these [complications] until BMI gets over 50,” Ward said. “For individual complications, we found a significant increase in trend for acute kidney injury, cardiac arrest, reintubation, reoperation, superficial infection and death within 1 year.”

Univariate and multivariate analyses showed BMI greater than 40 was linked with a statistically significant increase in complications. Whereas multivariable regression analysis indicated that having a BMI greater than 40 showed a 1.18 odds ratio for an increased risk of combined complications, other comorbidities studied were linked with higher odds ratios.

A receiver operating characteristic curve indicated BMI is “a poor predictor of risk. It was even worse than age or the Charlson Comorbidity Index, although all these were low. And this is worse than whether or not a cough predicts that you have strep throat,” Ward said. — by Gina Brockenbrough, MA

Reference:

Ward DT. Paper #46. Presented at: American Association for Hip and Knee Surgeons Annual Meeting. Nov. 7-9, 2014; Dallas.

Disclosure: Ward has no relevant financial disclosures.