August 2015

Contributors to pediatric ACL surgery outcomes

8ACL-iStock5983968-copyBy Justin T. Newman, MD

Different factors influence outcomes after anterior cruciate ligament reconstruction in younger and older pediatric patients, but regardless of age, a delay to surgery is correlated with more severe additional injuries and the need for additional surgical procedures.

The anterior cruciate ligament (ACL) has been a focus of sports medicine and orthopedic surgery over the past decades. Entering those three words into the PubMed search engine returns nearly 15,000 peer-reviewed articles on the topic. This segment of the literature continues to expand, with several articles published in the prominent orthopedic sports journals each month.

The ACL consists of two distinct bundles that originate from deep within the lateral notch of the femur and course to the anterior aspect of the tibial plateau. The primary function of this ligament is to provide stability at the knee with regard to anterior translation and rotation of the tibia underneath the femur.

Although adult ACL injuries and their treatment are well recognized and routinely addressed, the management of pediatric ACL injuries continues to be defined. The pediatric patient with growth remaining still has growth plates, known as open physes. These physes are found in the femur and tibia just above and below the joint line. Damaging a physis could cause disturbances to the growth of the leg, resulting in a shorter limb or malalignment from a disproportionate amount of growth in the normal, uninjured part of the physis. In addition, pediatric ACL injury was historically thought to be a rare occurrence, with the tibial spine avulsion fracture thought to be the more common version of this injury in the younger population.1

The pediatric ACL reconstruction patient is not a smaller version of the adult patient, and a different approach is required to avoid a different set of complications.

Several factors have led to an increased interest in pediatric ACL injuries. ACL injury in the pediatric population has been diagnosed more frequently, likely due to an increased appreciation for this injury by younger athletes (and their parents) and increased education of the providers who treat these patients on a routine basis. There has also been a dramatic increase in the amount and intensity of the activities in which pediatric athletes participate. Children are now involved at a higher level of competition at a younger age, they participate in year-round sports leagues, and there is an increased focus on a single sport at a younger age. All of these factors have resulted in younger athletes, with a different set of muscle control and balance profiles than in the past, being exposed to more frequent opportunities for ACL injury.1,2

These factors have prompted increased interest in the diagnosis and treatment of pediatric ACL injuries. This has correlated with an uptick in the volume of peer-reviewed literature on this topic and in the development and popularization of new or modified surgical techniques. The pediatric patient is not a smaller version of the adult, and a different approach is required to avoid a different set of complications and to both prevent and rehabilitate the injury patterns seen in this cohort.

Pediatric surgical techniques

8ACL-iStock16980005-copyBroadly speaking, the surgical techniques that have been created to address the special circumstance of the pediatric ACL injury aim to decrease the possibility of damage to the growth plates while restoring the anatomical or functional role of the ACL. These techniques either do not cross the physis of the tibia or femur, cross it with a deliberately minimal footprint, or modify the type of graft fixation to minimally impact the patient’s remaining growth. Long-term studies on many of these techniques have not been performed, but the early outcomes are promising.3

Historically, patients with remaining growth were recommended to delay reconstruction of the torn ACL until little or no growth potential remained. While this treatment approach mitigates the potential for disturbance of the growth plate, the stability that is provided by an intact ACL remains absent. This raises the concerning possibility that the residual instability may allow abnormal joint motion, which can cause additional damage to the meniscus or cartilage.

Studies have shown that in adult knees, a delay to surgery for the ACL or a premature return to activities that require a functioning ACL can cause additional injuries. It is relatively common for a knee that has sufficient trauma to create an ACL rupture to also cause damage to other structures within the joint, with lateral meniscal injuries being reported in up to 50% of adult ACL injuries.4 Meniscal tears and cartilage damage associated with ACL injury can lead to a need for further surgery and can cause damage that significantly decreases the long-term health of the knee joint.5-7

Our research

To evaluate the extent to which other injuries occur in conjunction with ACL injury in pediatric patients, my colleagues and I undertook a study at The Children’s Hospital Colorado in Aurora.8 Specifically, we investigated the factors that caused further damage to the knee in pediatric patients with an ACL tear. Earlier studies had shown that a delay (typically more than three months) in ACL surgery in pediatric patients could in general increase the likelihood of additional injuries in the knee.9,10 However, we know that a pediatric patient is not just a smaller version of an adult patient, and pediatric patients vary in terms of their physical maturation. What had not been investigated in the past was the difference between older and younger groups of pediatric patients.

Specifically, our study aimed to compare the prevalence, severity, and management of such additional knee injuries among patients with remaining growth potential (younger than 14 years) versus skeletally mature patients (older than 14 years). We anticipated that concomitant injuries would be more prevalent in older patients. We also hypothesized that a delay to surgery would be a significant predictor of additional injuries that required additional surgical procedures in both groups.

We retrospectively reviewed the cases of 66 patients younger than 14 years and 165 patients aged 14 to 19 years. In addition to investigating the time from injury to surgery, we looked at the additional injuries these patients sustained. We not only reported on the injuries that were present, but went a step further and reported on the additional procedures that were required to treat these injuries.

Differences were found between the two groups. The older pediatric patients needed significantly more additional surgical procedures (65%) than the younger group (49%). This means that these patients needed procedures to fix or remove torn menisci or to treat injuries to the cartilage. Patients older than 14 years were doing more extensive damage to their knees by waiting for surgery.

Delays are detrimental

Even more interesting was that, in those younger than 14 years, we found that a delayed surgery was the strongest predictor of other ipsilateral knee injuries severe enough to need additional surgery. When looking at all factors (final multivariate analysis) for this age group, a delay in surgery was the only significant predictor of the presence of a concomitant knee injury requiring additional operative procedures. Patients who had surgery more than three months from the time of injury were 4.75 times more likely to need additional surgical procedures for injuries to cartilage or meniscus than those who had surgery within three months of the initial ACL injury. In univariate analysis, a return to activities or sport prior to surgery showed some correlation with the presence of concomitant injuries. There was no significant correlation with obesity, patient gender, or the sensation of instability prior to surgery or at any point after the initial injury.

In the older group, surgery delayed by more than three months was also significantly related to the presence of additional injuries. However, multivariate analysis revealed that obesity and a return to athletic activities before surgery were the most important and statistically significant factors in predicting additional knee joint injuries. These older patients were 3.86 times more likely to need additional surgical procedures if they returned to activity or sports before surgery. They were also 2.59 times more likely to need additional surgical procedures if they were obese, defined as a body mass index (BMI) above the 95th percentile for their age and gender.

In both groups, meniscal tear severity was worse when surgery was delayed. The longer the wait, the lower the probability that the meniscus tear could be repaired. The meniscus plays a vital role in the health of the cartilage, and if a tear is not able to be repaired, there is a much worse outlook for the knee over time.11

8ACL-iStock4213736-copyIn the younger patients, a longer wait for surgery was also associated with greater severity of cartilage injuries. We did not find any association between delayed surgery and cartilage injury severity in the older group.

These results suggest that chondral injuries in younger patients are the result of progressive damage to the articular surface of the knee. In contrast, older patients may sustain more severe damage at the time of the initial injury. Adult studies also report that increased age and a longer time from injury to ACL surgery are associated with a higher risk for more severe cartilage injuries seen at the time of surgery.7,12,13 Whether these apparent differences in injury patterns among adults and younger and older pediatric patients are due to increased patient awareness or the patient’s age-related stability, body control, or proprioceptive differences remains to be determined.

We suspect that differences in activity level and compliance with activity restrictions may explain the injury patterns in the two pediatric populations we studied. Younger patients may be less compliant with activity restrictions and more likely to engage in activities outside of organized sports that can result in subsequent knee injuries. In older patients, subsequent knee injuries were more likely to occur after a return to organized sports, sport-related activities, or both, especially among heavier individuals. However, based on the data collected in the current study, it is not possible to draw definitive conclusions regarding the differences in risk factors between the two populations.

This study demonstrated that a delay to surgery was correlated with more severe additional injuries and the need for additional surgical procedures to treat these injuries. Similar findings have also been demonstrated in other studies on pediatric patients, as mentioned previously, as well as in the adult literature. This led us to question why these patients continue to present for surgery in this delayed fashion. If the risk factors for the delay in surgery could be identified, we might be able to treat these patients in a more effective manner, which in turn would potentially improve patients’ ability to not only return to play, but to have a healthier joint for their lifetime.

Socioeconomic factors

To investigate these questions, we undertook a sister study using the same patient population to investigate if socioeconomic factors played a role.14 From our anecdotal experience, we believed that socioeconomic factors do play a role in how quickly patients are able to present for evaluation and treatment of their ACL injuries. We hypothesized that socioeconomic and demographic factors would be significantly related to ACL surgery timing.

To study this, we looked back at all 272 patients who were included in the original study. Demographic variables of interest included age at injury, race, ethnicity, sex, height, and BMI. Obesity was defined as a BMI greater than the 95th percentile for age and gender. Socioeconomic variables included household income and insurance type. Household income was estimated based on the median income associated with each patient’s home ZIP code.

We found that patients with commercial insurance underwent surgery an average of 1.5 months after injury, whereas patients who were government-assisted or uninsured had surgery after an average of three months. Patients younger than 14 years averaged 2.6 months from injury to surgery, compared to 1.7 months for patients 14 years or older. Patients whose household income was estimated to be higher than the 75th percentile averaged 1.2 months to surgery, while patients in lower-income households averaged 2.2 months to surgery.

The risk of delayed ACL surgery was significantly higher among pediatric and adolescent patients who were younger, less affluent, and covered by a noncommercial insurance plan. There was a 67% chance that a patient with commercial insurance had undergone ACL surgery sooner than a patient with a noncommercial insurance plan.

After controlling for the other factors, we still found that a lack of commercial insurance made patients twice as likely to be delayed in undergoing surgery. Also, for every one-year increase in patient age, surgery occurred 1.2 times faster. None of the other factors we looked at had a statistically significant impact.

Sources of delays

There are many steps required to get patients from the knee injury to the operating room. We probed further to see where the delays might be occurring to see if there was one area in which intervention could potentially improve these findings.

We found that, when time to ACL surgery was divided into more specific treatment-related time periods, noncommercial insurance coverage was associated with a significantly higher risk of delayed care than commercial insurance coverage during the time from initial injury to MRI evaluation, from initial injury to orthopedic evaluation, and from orthopedic evaluation to surgery. This suggests the source of the delay among patients with noncommercial insurance was not related to one specific component of the postinjury treatment process. Instead, the delay was consistent across all treatment phases.

This study was performed at a tertiary referral pediatric hospital that, to our knowledge, has no policies of discrimination, screening, or access restrictions related to insurance, age, or affluence. These delays persisted despite no block from the medical providers, who understand the findings as presented above and would like nothing more than to see these patients in a timely manner.

It is important to appreciate that navigating the diagnostic, operative, and postsurgical appointments associated with the surgical management of an ACL injury places substantial burden on the patient and his or her family. The process can be expensive and time consuming, and progressing from one step to the next, from understanding the initial injury to the postoperative rehabilitation, can be a difficult process to navigate. This may be one of many confounding reasons for a delay in care for these young athletes.

It is our hope that this study, as well as an increased understanding of the injury and increased recognition by athletic trainers, staff, primary and emergency department physicians, and the medical team as a whole, can help to improve care for these patients.

Justin T. Newman, MD, is an orthopedic surgeon whose practice focuses on sports medicine and sports related injuries. He practices in Parker and Denver, CO.  

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