Abstract:Objective To observe the effect of different mechanical stress conditions on tendon-bone healing in a rabbit anterior cruciate ligament(ACL) reconstruction model. Methods Sixty-four 6-month-old New Zealand white rabbits underwent ACL reconstruction using autologous semitendinosus tendon on the right knee joint. 2 weeks after operation, according to the motion intensity, all animals were randomly divided into four groups: immobilization (IM) group, free motion (FM) group, low-intensity motion (LIM) group and high-intensity motion (HIM), HIM group, Eight weeks after surgery, all the knee joints were evaluated by histological analysis and biomechanical testing. Results Compared with FM group, the tendon-bone interface in the IM group still had obvious boundaries and fissures, more inflammatory cells and vascular tissue, and no chondrocyte was found. Histological scores (P>0.05) and ultimate load to failure (P<0.05) were lower. The tendon-bone interface of the LIM group was closest to the normal tendon-bone insertion point. Compared with other groups, LIM group had a higher histological score and ultimate load to failure(P<0.05). Early internal fixation failure occurred in 3 cases in the HIM group, the histological score and ultimate load to failure were lower than those of the LIM group(P<0.05), and higher than that of the FM group(P<0.05). Conclusion Appropriate stress stimulation after ACL reconstruction can improve the quality of tendon-bone healing. Neither of immobilization nor a high-intensity motion benefits to tendon-bone healing, which may delay tendon-bone healing process or lead to early failure of ACL reconstruction.