BMI predicted infection after TKA better than adipose tissue
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DALLAS — Results presented at the American Association of Hip and Knee Surgeons Annual Meeting showed BMI was a better predictor of periprosthetic joint infection after total knee arthroplasty compared with measures of adipose tissue.
Simon W. Young, MD, MBChB, FRACS, and colleagues recorded demographics, comorbidities, surgical duration and postoperative infection status within 1 year for 4,700 patients who underwent TKA between January 2013 and December 2016. Researchers analyzed preoperative weight-bearing anteroposterior and lateral X-rays to determine pre-patellar adipose thickness, bony width of the tibial plateau and total soft-tissue knee width, and calculated knee adipose index from the ratio of bone to total knee width.
In his presentation, Young noted researchers identified 31 periprosthetic joint infections. Knee adipose index had no statistical association with periprosthetic joint infection, according to Young.
“When we looked at pre-patella fat thickness, there was perhaps a slightly more favorable trend, but still no statistically significant association,” Young said.
However, he noted a correlation between BMI and periprosthetic joint infection, with an increased risk of periprosthetic joint infection among patients with a BMI greater than 35 kg/m2.
“When we put [BMI] through a multivariable model, it held up well with an increased odds ratio of 2.9 for a BMI greater than 35 [kg/m2],” Young said. – by Casey Tingle
Reference:
Young SW, et al. Paper 22. Presented at: American Association of Hip and Knee Surgeons Annual Meeting; Nov. 7-10, 2019; Dallas.
Disclosure: Young reports he is a board or committee member for American Association of Hip and Knee Surgeons; is a paid presenter or speaker for Arthrex Inc., Smith & Nephew and Stryker; is a paid consultant for Stryker; receives research support from Stryker and Vidacare; and has stock or stock options from Surgical Solutions.
Perspective
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Adolph J. Yates Jr., MD, FAAOS, FAOA
There has been recent literature that argues for more surgical site-specific issues, such as excess local adipose tissue being more predictive of wound complications than BMI, per se. In their well-done study presented at the American Association of Hip and Knee Surgeons Annual Meeting last month, Simon W. Young, MD, MBChB, FRACS, and colleagues clearly demonstrate that the depth of the soft tissue envelope at the time of TKA does not correlate with risk of infection, but BMI does. One of the corollary findings was that local tissue thickness measured by the lateral pre-patellar soft tissue shadow and the ratio of skin shadow to the knee on the anteroposterior preoperative films were highly variable in terms of relationship to BMI. Although operative time did increase with both higher BMI and thicker envelopes, the infection risk was only elevated in the BMI patients leading to an argument for the systemic effects of the BMI being more critical. The multicenter nature of the study and relatively large cohort add credence to the findings. The paper will hopefully be added to the peer-reviewed literature in the near future.
Department of orthopedic surgery
Chief of orthopedic surgery
Pittsburgh
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