October 2012

Early ACL surgery could lower risk of associated knee damage

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Patterns mirror those seen in adults

By Cary Groner

Timing of reconstruction surgery after pediatric anterior cruciate ligament (ACL) injuries seems to be related to the prevalence of meniscal and chondral injuries discovered during those surgeries, according to new research published in the September issue of The American Journal of Sports Medicine.

Researchers from the University of Texas Southwestern Medical Center in Dallas retrospectively reviewed the records of 241 pediatric patients who had undergone primary ACL reconstruction 150 days from injury or sooner and 129 patients treated more than 150 days out. In the early group, 37.8% had medial meniscal tears (MMTs) versus 53.5% in the delayed group; rates of lateral meniscal tears (LMTs) were similar (about 57%) in both groups. Patients with meniscal tears, moreover, were more likely to have a chondral injury in that compartment.

“The historical treatment algorithms, in terms of leaving these injuries alone, have been based on the hope that the children would heal. But the meniscus is not a highly vascular structure, especially as you move toward the inside, so our hopes of it healing itself may be unfounded,” said Guillaume Dumont, MD, chief resident in orthopedic surgery at the University of Texas Southwestern Medical Center in Dallas, and the paper’s lead author. “Children are more active than the rest of the population, so we may see a higher prevalence of injury down the line in younger kids with ACL-deficient knees, just because they’re the ones who are participating in sports every day and running around the schoolyard.”

That activity level may contribute to the increased prevalence of meniscal injuries associated with delayed surgery in the study, said Darin Padua, PhD, ATC, a professor in the Department of Exercise and Sports Science and director of the Sports Medicine Research Laboratory at the University of North Carolina at Chapel Hill.

“The ACL plays an important role in stabilizing the motion of the tibia on the femur,” Padua said. “In those 150 days of moving around, the patient may induce a meniscal or cartilage injury that wasn’t there initially.”

Such collateral damage increases the risk of subsequent osteoarthritis (OA), a particularly troublesome prospect in young patients, Padua noted.

“If a kid with a torn ACL decides to delay surgery, then goes on to damage their meniscus, they are at high risk for getting OA in their twenties or thirties,” he said.

Although the study suggested that delayed surgery may lead to higher rates of meniscal injury, other experts have urged caution in interpreting those results.

“The study documents the status of the meniscus at the time of surgery, but not at the time of injury,” noted Cynthia LaBella, MD, associate professor of pediatrics at Northwestern University’s Feinberg School of Medicine, and medical director for the Institute for Sports Medicine at the Ann & Robert H. Lurie Children’s Hospital of Chicago. “As a result, we don’t know whether those meniscal tears were a result of the initial trauma or accumulated during the interval between it and surgery.”

It’s an important distinction, LaBella said, because if the meniscal damage occurred concurrent to the ACL injury, elapsed time to surgery isn’t as crucial as it would be if the meniscal damage resulted later due to unstable, ACL-deficient knees.

“I don’t think you can conclude that delay led to meniscal injuries,” she said. “You can say there’s an association, but we have no way of knowing whether the patients started out with those meniscal injuries at the time of trauma.”

“It would be great to see what the rate of meniscal injury was one day after the ACL tear, then compare it as time went on,” agreed Dumont. “This was an observational study done at the time of surgery, but I think it makes sense that if you have an unstable knee, and there are structures inside it that are undergoing abnormal stresses, it’s more likely to sustain meniscal injury.”

Regarding the findings that patients had more lateral than medial meniscal tears—but that the lateral tear rate wasn’t affected by the time lag between injury and surgery—Dumont noted that this is also seen in adult populations.

“Adults with an acute ACL tear are more likely to have a lateral meniscus tear associated with it, and as time goes on the rate of medial meniscal tears increases. It’s difficult to say exactly what motion in the knee is causing that, but it indicates to me that there are abnormal stresses in the medial compartment of the ACL-deficient knee,” Dumont said.

Cary Groner is a freelance writer in the San Francisco Bay Area.

Source:

Dumont GD, Hogue GD, Padalecki JR, et al. Meniscal and chondral injuries associated with pediatric anterior cruciate ligament tears: relationship of treatment time and patient-specific factors. Am J Sports Med 2012;40(9):2128-2133.

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