Attachment of autogenous tendon graft to cortical bone is better than to cancellous bone: a mechanical and histological study of MCL reconstruction in rabbits.

We analyzed the mechanical and histological variables after the attachment of an autogenous tendon graft to cortical or cancellous bone. We reconstructed the medial collateral ligament of the knee in 33 Japanese white rabbits, using a bone socket procedure. The floor of the bone socket was cortical bone in group A and cancellous bone in group B. Mechanically, the pull-out test showed a tendency towards an increase in maximum failure load, with 10.9 N, 35 N and 37 N in group A, and 11 N, 18 N and 36 N in group B at 2, 4 (statistically significant difference) and 8 weeks after surgery, respectively. Histologically, the attachments were immature at 2 weeks. At 4 weeks, granulations had matured and Sharpey's fiber-like structures were seen. These fibers were more abundant in group A than in group B. At 8 weeks, the attachments in both groups were rather like the normal 4-zone structure. With time, tendon attachments matured in both groups. Our study showed that reattachment of tendons to cortical bone may be bettter than to cancellous bone.