[Comparative study of tendon-bone healing and bone-bone healing after anterior cruciate ligament reconstruction]

To investigate and compare the difference between two implants of reconstructing anterior cruciate ligament (ACL) for the early healing of implants tunnel interface in terms of biological mechanism.

Fifty-five adult New Zealand rabbits weighing 2.0-2.8 kg were selected. Patellar ligament with tibia-bone block was obtained from the left knee joint serving as donor site, right knee joint served as the recipient site of autograft for ACL reconstruction. The bone block end of implant was bone-bone interface healing model, while the ligament end was tendon-bone interface healing model. The general condition of rabbits was observed after operation, the gross observation and histology observation were conducted at 2, 4 and 8 weeks after operation (n=5), and biomechanics examination was conducted at 4 and 8 weeks after operation (n=20).

Rabbits behaved normally after operation. The gross observation indicated that ACL had complete continuity and moderate tension during experiment. Histology observation: most part of bone-bone interface was connected by fibrous tissue, while the tendon-bone interface was mainly filled by granulation tissue 2 weeks after operation; most part of bone-bone interface was bone union, and there were osteogenesis reaction and large quantity of fibroblasts in the tendon-bone interface 4 weeks after operation; complete bone union was evident in bone-bone interface, and the appearance of Sharply fibers and the formation of indirect insertion occurred in part of tendon-bone interface 8 weeks after operation. Biomechanics observation: the pull-out rate for tendon-bone interface and bone-bone interface 4 weeks after operation was 85% and 15%, respectively; while it was 95% and 5% 8 weeks after operation, respectively; indicating there was a significant difference between two groups (P < 0.001).

In the early stage after ACL reconstruction, bone-bone interface is better than tendon-bone interface in terms of intensity and speed of healing.