Dr. Murray and her colleagues have created an elegant, in vitro, animal study that helps to clarify some of the key questions regarding the effect of age and specific technique on repair of the anterior cruciate ligament. The porcine animal model, while not directly translatable to humans, allows us a more effective opportunity to evaluate histological and clinical healing of the ligament repair tissue.
Historically, surgeons have all but discarded the use of primary repair in addressing anterior cruciate ligament injuries unless the ligament is avulsed from its origin or insertion. The outcomes have been substantially better with reconstruction than with repair in adults. The juvenile and adolescent population introduces the unique challenges of reconstructing cruciate ligaments across open physes, with the risk of premature physeal closure. Therefore, many clinicians have elected to accept the risk of additional meniscal injury and wait until the patient achieves skeletal maturity before proceeding with reconstruction. If there were a better way to repair a torn anterior cruciate ligament in the juvenile and adolescent population, it could change the current treatment algorithm.
The authors of this paper transected the anterior cruciate ligaments of both knees in the porcine model, leaving one to heal on its own as the control and repairing the other with an enhanced suture repair technique, combined with the use of collagen platelet composite. I would have liked to have seen a third group to compare the results of suture repair alone without the collagen matrix added, but this was not done in the study. Nonetheless, the authors report some very important findings. In this study, the younger the animal, the better the result with use of suture repair with their augmented suture technique. At the time of follow-up, the tissue is stronger and histologically more viable. In the adult animals, there was a poorer quality of repair and secondary global capsular thickening that provided a pseudostability of the knee by increasing the overall stiffness.
As is the case with all animal studies, it is not clear how these findings will extrapolate to humans. Nonetheless, the findings in this porcine model give a reason for excitement as we look toward the future in addressing anterior cruciate ligament instability, particularly in the skeletally immature individual.