In the March 18 2015 edition of The Journal, Brophy et al. and investigators from the MOON Knee Group focus on that very rare complication of ACL reconstruction surgery: infection. They prospectively followed a large cohort of more than 2,100 patients treated at multiple sites from 2000 to 2005.
The overall infection rate was less than 1%, which is in line with rates found in other studies. What was most notable is that the infection rate among patients with diabetes was 8.7% but only 0.7% in patients without diabetes. Statistically, having diabetes increased the odds of a post-ACL infection by nearly 19 times. Patients with diabetes should be counseled preoperatively so that they can be extra vigilant about detecting early signs of infection. Screening for diabetes prior to ACL surgery is not currently a standard of care, but it might be considered a reasonable approach in light of these findings. Surprisingly age and BMI were not associated with increased infection risk, and there was only a trend toward smokers being at higher risk.
Brophy et al. also found that patients receiving hamstring autografts were more than four times as likely to experience infection as those who received bone-tendon-bone (BTB) autografts. The authors’ hypothesis that the deep dissection required for hamstring harvest might increase infection risk seems plausible. It may also be that younger, healthier, more active patients (with presumably stronger immune systems) were more often offered BTB grafts.
What I like most about this study is that the MOON registry has very accurate clinical data because the investigators are clinicians who are highly invested in data quality. This is in distinction to studies that rely on administrative databases, where the coding of events is done by non-clinicians who may have less interest in entering highly accurate data. Still, as clinically accurate as MOON data are, they are from more than a decade ago. Although the risk of post-ACL infection may be even lower in this decade, with these already-low rates, it would be difficult to statistically prove that progress.
Marc Swiontkowski, MD