Failure of anterior cruciate ligament reconstruction: the biologic basis.

The replacement tissue used for anterior cruciate ligament reconstruction undergoes extensive biologic remodeling and incorporation after implantation. Successful biologic incorporation of the graft is dependent on a number of factors including graft placement, tensioning, and the nature of the tissue (allograft versus autograft). Failure of an anterior cruciate ligament reconstruction may occur on the basis of either technical, mechanical, or biological factors. Biologic factors include cellular repopulation, matrix remodeling, the ultimate small diameter collagen fibril orientation, the final cross sectional area of the graft, a favorable vascularization, and not overloading the graft during the remodeling process. The fully incorporated graft never duplicates the native anterior cruciate ligament but works as a check reign that makes the knee more functional.