Collagen-Platelet Composite Enhances Biomechanical and Histologic Healing of the Porcine Anterior Cruciate Ligament

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. HYPOTHESIS: At the time of suture repair, placement of a bioactive scaffold in the ACL wound site would improve the structural properties of the tissue. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-seven knees in immature pigs underwent ACL transection and suture repair. A collagen-platelet composite (CPC) was used to supplement the repair in 14 knees. Knees were harvested at 4 weeks, 6 weeks, and 3 months. Mechanical testing and histologic analysis were performed. RESULTS: The addition of a CPC to a suture repair resulted in improvements in yield load and linear stiffness of the repair tissue at 3 months, as well as a significant increase in cell density. A reduction in yield load and stiffness occurred at the 6-week time point in both groups, a phase when revascularization was noted. CONCLUSION: The addition of a CPC to a suture repair enhanced the structural properties of the ACL, and the improvement was associated with increased cellularity within the healing ligament. CLINICAL RELEVANCE: The addition of a bioactive scaffold to the wound site improved the functional healing of the ACL after suture repair. The decreased repair strength during revascularization may indicate a need to protect the repair site through this period.