Summary

In pediatric patients who cope without an ACL, coronal and sagittal plane biomechanical adaptations are observed that include less knee valgus and less knee flexion with an increase in ankle dorsiflexion during gait.

Abstract

Background

Pediatric anterior cruciate ligament (ACL) reconstructions are increasing in frequency attributed to various factors. Despite limited high levels of evidence, surgical management of pediatric ACL reconstruction is commonly recommended to avoid future menisco-chondral injury. However, we propose that some of these patients are able to biomechanically adapt to the ACL deficiency with no future instability. The primary aim of this study is to identify biomechanical patterns in pre-pubescent patients following an ACL injury who have no residual instability (copers) compared to those with instability (non-copers).

Methods

Pre-pubescent patients (Tanner stage 1) who sustained an isolated ACL injury were recruited to participate in this IRB approved study. Patients with a concomitant meniscal tear or with current symptoms of instability were excluded from enrollment. The study cohort underwent motion capture testing, which included gait, heel touch (HT) and overhead squat (OHS) tasks. Kinematic and kinetic variables of interest were calculated across stance phase of gait, and over ascent/descent phases for OHS and HT. EMG analysis was also performed and normalized by contralateral max signal. Patients who eventually reported instability were deemed non-copers and were offered an ACL reconstruction. Patients who did not develop instability and completed physical therapy were allowed to return to full athletic activity. A Wilcoxon signed-rank test was used to compare the ACL injured limb of copers to non-copers (α=0.05).

Results

12 patients (mean age 11.9 years old, 71%M) completed testing (average 6.6 months after injury). Seven copers were identified while five ultimately converted to ACL reconstruction (non-copers) due to instability. Overall, copers demonstrated decreased knee valgus during gait, OHS and HT and increased coronal plane moment during gait. Copers had decreased knee flexion and increased ankle dorsiflexion in SLS and minimized hip extension during gait. During a squat, copers demonstrated more hip flexion. There were no differences in EMGs between copers and non-copers.

Conclusion

Coronal and sagittal plane biomechanical adaptations are observed in pediatric patients who cope without an ACL that include less knee valgus and less knee flexion with an increase in ankle dorsiflexion during gait. This knowledge may help identify pediatric patients that may be more amenable to safely undergo non-operative treatment for a pediatric isolated ACL injury.