The standard grafts used for ACL reconstruction are tendon, either patellar tendon, hamstring, or quadriceps. However, the microstructure and composition of tendon differs from ligament. Ideally, the ACL would be replaced with the same tissue.
To evaluate the incorporation of a bone-ACL-bone graft (B-ACL-B) graft for ACL reconstruction, we performed a controlled laboratory study in a rabbit model with micro-computed tomography (μCT).
46 New Zealand white rabbits were used, with 17 donor rabbits to harvest bilateral B-ACL-B allografts and 29 rabbits undergoing unilateral ACL reconstruction with B-ACL-B allograft. Knee specimens were collected for biomechanical testing (n = 14) at 4 and 8 weeks and for μCT analysis (n= 15) at 2, 4 and 8 weeks after surgery. Gross inspection and μCT examination confirmed bone blocks in the appropriate anatomic position. Biomechanical tests revealed no difference in mean load-to-failure force for B-ACL-B allografts between 4 and 8 weeks.
Progressive healing occurred between the bone block and the tunnel as demonstrated by a gradual increase in average bone-volume fraction and total mineral density in both femoral and tibial tunnels. Remodeling of the bone block was evidenced by a significant decrease in TMD (total mineral density) of both tibial and femoral bone blocks.
This is a report of a novel rabbit B-ACL-B allograft reconstruction model demonstrating early signs of graft remodeling and incorporation. Clinical Relevance: This study demonstrates ACL reconstruction using an anatomically matched ACL allograft, rather than a tendon graft, may be possible based on early findings in this lapine model.