Lower-extremity malalignment has appropriately gained traction as a risk factor for anterior cruciate ligament (ACL) tears in both adolescent and adult populations. The impact of increased posterior tibial slope (PTS) and static anterior tibial translation has been rigorously studied in recent years, and these alignment parameters have been indicated as potential risk factors for ACL tears in both adolescents and adults, notably for recurrent ACL tears after primary ACL reconstruction1,2. Given the common valgus mechanism of ACL injury, it appears logical that coronal valgus malalignment could predispose patients to an ACL injury. Coronal malalignment has been investigated in the young adult population, with static standing valgus having been shown to increase the risk of recurrent knee injury, especially in patients with a previous ACL injury3. While important, correcting malalignment of any variety with an osteotomy in the skeletally mature population often carries substantial morbidity and lowers functional outcomes and the level at which patients return to sport. As the incidence of pediatric ACL tears has increased over time, a better understanding of the risk factors for reinjury has become even more crucial in order to decrease the risk of potentially devastating chondral or meniscal injury in this young population. Also, if indicated, intervening on malalignment may be better tolerated in the pediatric population compared with the adult population, given the potential option of implant-mediated guided growth (IMGG). Bram et al. have elegantly presented coronal malalignment, particularly static knee valgus, as a risk factor for primary ACL injury in pediatric and adolescent patients. In their study, long-leg alignment radiographs of 100 pediatric and adolescent patients with a first-time ACL tear were matched with those of 100 patients without an ACL tear. They found that greater valgus alignment increased the odds of an ACL tear; specifically, for every degree of increased valgus alignment measured using the hip-knee-ankle angle (HKA), the odds of an ACL tear increased by 14%. In the group of patients with an ACL injury requiring surgery, nearly half (48%) were skeletally immature enough to be indicated for the physis-sparing, modified MacIntosh procedure. This study was not without limitations. Of the patients in the ACL tear group who had available lateral knee radiographs, a considerable number had an abnormal PTS, with nearly one-third (32.3%) having a PTS of ≥12°. The study authors were unable to compare PTS between patients with an ACL tear and those without an ACL tear, limiting their ability to suggest which parameter may be a more important risk factor. Ultimately, the most interesting question raised by this study concerns the role of IMGG in the skeletally immature patient with an ACL tear. If coronal alignment is as important as this paper suggests, there could be a role for concomitant IMGG at the time of ACL reconstruction to help correct valgus malalignment and to potentially reduce ipsilateral reinjury rates or the risk of contralateral ACL injury. A previous investigation by these authors demonstrated the maintained effect of IMGG in correcting genu valgum when performed concomitantly with ACL reconstruction, although the study did not specifically report the incidence of ACL reinjury4. There have also been case reports of anterior tibial guided growth prior to staged ACL reconstruction in pediatric patients with chronic ACL deficiency and increased PTS, although there is a lack of long-term outcome data to support a decreased reinjury rate5. While IMGG is not benign, as it requires multiple surgeries with their associated risks and costs, involves serial radiographic monitoring, and carries a risk of recurrence of malalignment following implant removal, it is certainly less morbid than larger alignment-correcting osteotomies in the skeletally mature population. In the right patient, concomitant IMGG and ACL reconstruction could be considered in order to restore more normal alignment and to possibly decrease the risk of reinjury, although further investigation is certainly warranted. We look forward to further work in this area, particularly larger clinical studies reporting the incidence of ACL reinjury after successful alignment correction with IMGG, cost analyses of these interventions, further investigation into the combined effect of increased PTS and genu valgum, and guidance on when and where to intervene in this population.
Boublik et al. (Wed,) studied this question.