Background-The outcome of ACL reconstruction is variable and many patients have increased joint laxity postoperatively.

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 purpose of this study was to determine if providing bony stabilization between the tibia and femur would improve the structural properties of an "enhanced" ACL repair using a collagen-platelet composite when compared to the traditional (Marshall) suture technique.Methods-Twelve pigs underwent unilateral ACL transection and were treated with sutures connecting the bony femoral ACL attachment site to the distal ACL stump (LIGAMENT group), or to the tibia via a bone tunnel (TIBIA group). A collagen-platelet composite was placed around the sutures to enhance the biologic repair in both groups. Anteroposterior (AP) knee laxity and the graft structural properties were measured after 15 weeks of healing in both the ACL-repaired and contralateral ACL-intact joints.Results-Enhanced ACL repair with bone-to-bone fixation significantly improved yield load and linear stiffness of the ACL repairs (p<0.05) after 15 weeks of healing. However, laxity values of the knees were similar in both groups of repaired knees (p>0.10).Conclusions-Using an enhanced ACL suture repair technique that includes bone-to-bone fixation to protect the repair in the initial healing stages resulted in an ACL with improved structural properties after 15 weeks in the porcine model.Clinical Relevance-The healing response of an ACL suture repair using a collagen-platelet composite can be enhanced by providing bony stabilization between the tibia and femur to protect the graft during the initial healing process in a translational model.

Magnetic Resonance Imaging (MRI) could potentially be used to non-invasively predict the strength of an ACL graft after ACL reconstruction. We hypothesized that the volume and T2 relaxation parameters of the ACL graft measured with MRI will predict the graft structural properties and anteroposterior (AP) laxity of the reconstructed knee. Nine goats underwent ACL reconstruction using a patellar tendon autograft augmented with a collagen or collagen-platelet composite. After six weeks of healing, the animals were euthanized, and the reconstructed knees were retrieved and imaged on a 3T scanner. AP laxity was measured prior to dissecting out the femur-graft-tibia constructs which were then tested to tensile failure to determine the structural properties. Regression analysis indicated a statistically significant relationship between the graft volume and the failure load (r2=0.502; p=0.049). When graft volume was normalized to the T2 relaxation time, the relationship was even greater (r2=0.687; p=0.011). There was a significant correlation between the graft volume and the linear stiffness (r2=0.847; p<0.001), which remained significant with T2 normalization (r2=0.764; p=0.002). For AP laxity at 30° flexion, there was not a significant correlation with graft volume, but there was a significant correlation with volume normalized by the T2 relaxation time (r2=0.512; p=0.046). These results suggest that MRI volumetric measures combined with graft T2 properties may be useful in predicting the structural properties of ACL grafts.