Background: after anterior cruciate ligament (ACL) reconstruction, it is necessary to integrate free tendon graft biologically to the bone. In the present study, to verify whether a structure identical to the normal ligament-bone insertion could be regenerated at the tendon-bone interface without bone tunnel, we designed ACL reconstruction model without a tibial bone tunnel. Moreover, to enhance the integration process in this model, bone marrow-derived mesenchymal stem cells (bMSCs) were transplanted, and histological changes investigated. Our first hypothesis was that the grafted tendon would be anchored at part of the tendon-bone interface even if a bone tunnel was not created. Second hypothesis was that application of bMSCs at the tendon-bone interface would yield results histologically superior to those in controls.
Methods: bilateral ACL reconstruction using our originally designed method was performed. Autologous bMSCs with the carrier were transplanted between the bottom of the grafted tendon and the bone pit of the tibia in the experimental limb, whereas the control limb received the carrier only. At 4 and 8 weeks after the operation, histological comparison between bMSCs and the control group was carried out.
Results/conclusions: even in our present ACL reconstruction model without a tibial bone tunnel, integration via chondroid tissue was seen at part of the tendon-bone interface. However, there were no appreciable differences between the groups. In ACL reconstruction, to enhance the tendon-bone integration without a bone tunnel would lead to save the graft length and prevent from bone tunnel complications (ex. Bone-tunnel enlargement after surgery).
Keywords: anterior cruciate ligament; enthesis; mesenchymal stem cell; rabbits; tendon-to-bone healing; tunnel enlargement.