Consider Surgery for Obese ACL Patients

Mary Ann Porucznik

Although anterior cruciate ligament (ACL) tears are normally considered high-energy injuries sustained during sporting events, a retrospective cohort analysis found that a low-energy mechanism of injury is common among obese patients. In addition, the study found that nonsurgical management of ACL injuries in obese patients may result in episodes of instability and predispose the patients to the earlier onset of degenerative joint disease.

According to coauthor Michael J. Chambers, MD, “Although these individuals do not match the typical activity level profile, surgical consideration is necessary.”

The researchers identified 166 patients at a single institution who underwent ACL reconstruction between November 2007 and March 2011. Patients younger than age 10 or older than age 70 were excluded, as were those with multiligamentous knee injury, associated fracture, or revision ACL reconstruction. Only patients whose height and weight at the time of injury were recorded in the electronic medical record were included.

Of the 131 patients who met the inclusion criteria, 32 were obese (defined as body mass index [BMI] of 30 or higher). The remaining patients served as the control group. The mean BMI for the obese group (Group 1) was 35 (range, 30–50); for the control group (Group 2), it was 24 (range, 16–29).

Researchers found no statistically significant differences between the two groups regarding sex or tobacco use, but patients in Group 1 were significantly younger than those in Group 2 (mean age, 24.2 and 31.5 years, respectively; P = 0.0004).

Of the 26 patients with low-energy mechanisms of injury, 12 were in Group 1 and 14 in Group 2. More than half of the patients in Group 1 (56 percent) experienced at least two episodes of symptomatic instability prior to ACL reconstruction, compared with slightly less than one third of those in Group 2 (32 percent). Patients in Group 1 were more likely to have instability at low activity levels compared with those in Group 2.

In addition, most of the patients (52 percent) who were identified as having osteochondral injuries belonged in Group 1. Nearly three out of four patients in Group 1 also had meniscal injuries at the time of arthroscopic examination.

“These findings highlight the importance of the ACL in maintaining knee stability during low-demand activities of daily living in obese patients,” noted Dr. Chambers. “This finding is in stark contrast to the established literature on nonobese patients with ACL injury and suggests that the bias toward nonsurgical treatment in the ‘ACL-dependent’ obese population may be misguided.”

The authors point to several reasons for this increased dependence on the ACL in obese patients, including the larger stresses across the knee, the general deconditioning of the lower extremity and core due to a more sedentary lifestyle, and the difficulty in managing instability with bracing in this population. “Poorly fitting braces often lead to poor compliance with usage or are ineffective, leaving the obese patient susceptible to instability,” they note.

Limitations of this study include missing and possibly inaccurate information in the medical charts, potential inaccuracies in classifying injury energy levels, and a focus on patients who were treated surgically. However, the authors note that it is the first to investigate the mechanism of injury and pattern of instability after ACL injury in an obese patient population. They call for an additional study comparing early reconstruction with nonsurgical treatment in the obese population to determine whether early reconstruction can prevent the osteochondral and meniscal injuries they found.

“Our findings suggest that knee stability during low-demand activities of daily living in obese patients is much more reliant on a functional ACL,” they write. “Delayed reconstruction may contribute to the accumulation of high-grade osteochondral injuries, potentially predisposing the patient to the earlier onset of degenerative joint disease. Additional research is needed to establish the principles of best practice in this population.”

Dr. Chambers’ coauthors of Scientific Presentation 050, “Anterior Cruciate Ligament (ACL) Reconstruction in Obese Patients,” include Tigran Garabekyan, MD; Stephanie F. Zimmeck, MS-III; John J. Jasko, MD; and Charles E. Giangarra, MD.

Disclosure information: Drs. Chambers, Garabekyan, and Giangarra and Ms. Zimmeck—no conflicts; Dr. Jasko—Arthrex.

2013 Annual Meeting News
Tuesday through Friday, February 19 – 23, 2013.
http://www.aaos.org/news/acadnews/2013/AAOS9_3_20.asp