Background-The anterior cruciate ligament (ACL) fails to heal after traumatic rupture. Furthermore, large-animal models have recently shown that 1-month functional ACL healing is augmented after suture repair when a bioactive scaffold is placed in the tear site.

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Purpose The objective of this study was to compare the biomechanical outcomes of a new method of anterior cruciate ligament (ACL) treatment, bio-enhanced ACL repair, with ACL reconstruction in a large animal model. Methods Twenty-four skeletally immature pigs underwent unilateral ACL transection and were randomly allocated to receive bio-enhanced ACL repair with a collagen-platelet composite, allograft (bone–patellar tendon– bone) reconstruction, or no further treatment (n = 8 for each group). The structural properties and anteroposterior laxity of the experimental and contralateral ACL-intact knees were measured 15 weeks postoperatively. All dependent variables were normalized to those of the contralateral knee and compared by use of generalized linear mixed models. Results After 15 weeks, bio-enhanced ACL repair and ACL reconstruction produced superior biomechanical outcomes to ACL transection. However, there were no significant differences between bio-enhanced ACL repair and ACL reconstruction for maximum load (P = .4745), maximum displacement (P = .4217), or linear stiffness (P = .6327). There were no significant differences between the 2 surgical techniques in anteroposterior laxity at 30° (P = .7947), 60° (P = .6270), or 90° (P = .9008). Conclusions Bio-enhanced ACL repair produced biomechanical results that were not different from ACL reconstruction in a skeletally immature, large animal model, although the variability associated with both procedures was large. Both procedures produced significantly improved results over ACL transection, showing that both were effective in this model. Clinical Relevance Bio-enhanced ACL repair may 1 day provide an alternative treatment option for ACL injury.

There has been recent interest in the biologic stimulation of anterior cruciate ligament (ACL) healing. However, the effect of age on the ability of ligaments to heal has not yet been defined. In this study, we hypothesized that skeletal maturity would significantly affect the cellular and vascular repopulation rate of an ACL wound site. Skeletally Immature (open physes), Adolescent (closing physes), and Adult (closed physes) Yucatan minipigs underwent bilateral ACL transection and suture repair using a collagen-platelet composite. The response to repair was evaluated histologically at 1, 2, and 4 weeks. All three groups of animals had completely populated the ACL wound site with fibroblasts at 1 week. The Immature animals had a higher cellular density in the wound site than the Adult animals at weeks 2 and 4. Cells in the Immature ligament wounds were larger and more ovoid than in the Adult wounds. There were no significant differences in the vascular density in the wound site. Animal age had a significant effect on the density of cells populating the ACL wound site. Whether this observed cellular difference has an effect on the later biomechanical function of the repaired ACL requires further study. ß