HSS Research Supports Routine Imaging Before and After ACL Surgery in Growing Children

At this year's Pediatric Orthopedic Society of North America (POSNA) annual meeting, researchers at Hospital for Special Surgery (HSS) presented two studies evaluating outcomes for three of the most common anterior cruciate ligament (ACL) reconstruction techniques designed to protect open growth plates in young patients who are still growing. The findings highlight the importance of using imaging before and after surgery to accurately identify and monitor alignment issues and capitalize on opportunities for early intervention.

What follows are highlights from these studies:

Use of Imaging to Identify Alignment Issues in Pre-Pubertal Children After ACL Reconstruction

A new multi-center prospective study from researchers at HSS evaluated two specialized surgical reconstruction techniques commonly used to treat ACL injuries by restoring knee stability while minimizing risks of growth disturbances in children with open growth plates (skeletally immature) and more than two years of growth remaining.

Researchers compared changes in lower extremity alignment among 112 pre-pubescent patients (girls younger than 12 and boys younger than 14) who had either a physeal-sparing combined intra/extra-articular reconstruction with iliotibial band (ITB) autograft (77 patients) or an all-epiphyseal reconstruction (35 patients). All patients had x-rays taken before surgery and again one year after surgery to measure and compare growth changes in both legs.

They found that approximately 25% of children in the study developed subtle postoperative changes such as differences in leg length and angular deformity that could raise their risk of reinjury in the future. However, there were fewer growth disturbances among older patients who had less than two years of growth remaining.

"It's important to make people aware that even though these procedures are safe overall and designed to respect the growth plates, there is still a risk of kids experiencing alignment issues afterward," says Peter D. Fabricant, MD, MPH, pediatric orthopedic surgeon at HSS and senior author of the study.

An ACL injury is a painful tear or sprain of the ligament connecting the femur (thighbone) to the tibia (shinbone). These injuries have become common among physically active children, especially with year-round participation in sports and an increased level of competition.

In adult patients, the standard ACL reconstruction technique involves drilling tunnels in the femur and tibia to secure a new ligament. For children who are still growing, the growth plates-where the bones grow and gain length-are exactly where the surgeon would need to drill those tunnels. That is why alternative surgical techniques have been developed that reconstruct the ACL and minimize damage to the growth plate in young patients.

"If you injure the growth plate in a younger child who has many years to grow, there's a lot of time during which that growth plate can grow abnormally," explains Dr. Fabricant. "Prepubertal patients are the most vulnerable population for growth plate injury, so this study focused on that subset of patients to determine the incidence of developing deformity after surgery."

This is the first multicenter study to rigorously assess leg alignment before and after surgery and compare the surgical leg to the uninjured leg to identify and monitor postoperative growth disturbances. Such changes may not be reliably measured with clinical examination alone.

"This study gives evidence to support the use of imaging to routinely check a patient's alignment before surgery, check it after surgery, and monitor these kids for growth disturbances so that we can intervene in minimally invasive ways while they are still growing," explains Dr. Fabricant. "This is important because only checking alignment when there is a concern is very subjective and there may be missed opportunities for early intervention."

One minimally invasive surgical technique used to correct alignment issues is called implant-mediated guided growth. This involves placing implants around the growth plate that guide it to grow in a way that encourages realignment. The technique avoids the need for a much bigger operation (osteotomy) to realign the bone and a lengthy recovery, as would be the case for an adult.

"You can only do guided growth surgery when the growth plate is still actively growing, which for some of these kids is only a year or two after their surgery," explains Dr. Fabricant. "If you aren't routinely imaging to monitor alignment and you don't realize it in time, then you're beyond that window of being able to do that minimally invasive surgery."

Use of Imaging to Identify Alignment Issues in Adolescent Children With Open Growth Plates After ACL Reconstruction

A second study led by researchers at HSS found that 15% to 30% of adolescent patients who had ACL reconstruction with soft-tissue autograft developed changes in leg alignment, but no patients developed growth-related complications requiring intervention.

For adolescent patients who still have open growth plates and less than two years of growth remaining, ACL reconstruction with soft-tissue autograft is often the technique of choice. This procedure involves drilling tunnels in the bone that would be similar to an adult ACL reconstruction, but the surgeon uses a graft and implants that don't typically affect the growth plate.

"Even though this procedure is largely safe for adolescents, there is still a possibility of alignment changes after surgery," notes Peter D. Fabricant, MD, MPH, pediatric orthopedic surgeon at HSS and senior author of the study. "This study adds more evidence to support the need to take x-rays before and after surgery and monitor this population until they reach skeletal maturity."

The prospective multicenter study included 99 patients (50 boys and 49 girls with a median age of about 14 years) who had less than two years of growth remaining and underwent a primary transphyseal ACL reconstruction with soft-tissue autograft. Researchers used x-ray imaging before surgery and one year after surgery to measure and compare differences in leg alignment.

"We know that leg alignment is a vital factor in predicting injury, reinjury, and surgical failure, so measuring alignment preoperatively is extremely important because you gain the opportunity to address alignment issues at the same time as the ACL surgery with no additional risk," explains Dr. Fabricant.

For example, if a patient is found to have a borderline alignment issue before surgery, some surgeons may be encouraged to perform an implant-mediated guided growth surgery at the same time as the ACL reconstruction because they know that there is a risk of potentially worsening post-operative alignment if they don't.

"The logical next step is to strongly consider intervening on alignment problems when necessary in order to prevent reinjury," says Dr. Fabricant.