Acceleration of tendon-bone healing of anterior cruciate ligament graft using autologous ruptured tissue.

BACKGROUND It has been recently reported that human anterior cruciate ligament (ACL) ruptured tissue contains abundant vascular stem cells that contribute to tendon-bone healing in an immunodeficient rat model of ACL reconstruction. HYPOTHESIS Autologous ruptured ACL tissue has an effect on the maturation of bone-tendon integration in anterior cruciate ligament reconstruction. STUDY DESIGN Controlled laboratory study. METHODS Twenty healthy adult beagle dogs underwent bilateral ACL reconstruction using the ipsilateral flexor digitorum superficialis tendon and were divided into 2 groups: right knee (a tissue-treated group) and left knee (a control group). The tissue-treated group received autologous ruptured ACL tissue, which was obtained 2 days after resection and sutured to the tibial side of the graft. Histological, radiographic, and biomechanical assessments were performed. In addition, immunohistochemical staining was performed to assess angiogenesis and osteogenesis. RESULTS Histological assessment and staining for osteoblasts and endothelial cells at week 2 demonstrated early healing, inducing endochondral ossification-like integration with enhanced angiogenesis and osteogenesis in the tissue-treated group's grafts. Computed tomography at week 4 showed a significantly smaller tibial bone tunnel in the tissue-treated group (tissue, 19.0 ± 4.4 mm(2); control, 42.6 ± 4.7 mm(2); P = .009, n = 5). Furthermore, biomechanical testing of force during loading to ultimate failure at week 4 demonstrated a significantly higher strength in the tissue-treated group (tissue, 66.4 ± 10.1 N; control, 30.5 ± 10.3 N; P = .009, n = 5). CONCLUSION In the present study, the authors elucidated that transplantation of ACL-ruptured tissue, which was sutured to the tibial side of the graft, contributed to early tendon-bone healing in a canine model of ACL reconstruction. CLINICAL RELEVANCE Anterior cruciate ligament ruptured tissue has a therapeutic potential in promoting an appropriate environment for tendon-to-bone healing in bone tunnels of ACL reconstruction.