Graft healing in anterior cruciate ligament reconstruction

Graft healing within the bone tunnel after anterior cruciate ligament (ACL) reconstruction is still a complex, poorly understood biological process that is influenced by multiple surgical and postoperative variables. However, remarkable advances in knowledge of this process have been made based primarly on animal models. According to the findings of this review, some surgical and postoperative variables are known to directly affect time-course and quality of graft-tunnel healing. The type of graft, graft motion, and fixation methods have shown to directly affect time-course and quality of graft-tunnel healing. Therefore, the application of early and aggressive rehabilitation protocols should be cautious when using soft-tissue graft, allografts, and direct or aperture type of fixation for ACL reconstruction. With regard to graft placement, several cadaveric models showed biomechanical advantages of a more anatomical graft location; however, there are no studies that explore the relationship between graft placement and healing process. The precise effect of graft tensioning, graft/tunnel diameter disparity, and graft length within the bone tunnel in the graft healing process remains unclear and requires more research. To enhance graft-tunnel healing, tissue-engineering approaches, including the use of growth factors, mesenchymal stem cells, and periosteum graft augmentation, have been tested on animal models. These have shown promising results in terms of enhancement of bone-graft healing rate.