Biomechanical evaluation of augmented and nonaugmented primary repair of the anterior cruciate ligament: an in vivo animal study

Abstract

The purpose of this study was to evaluate in a sheep model the biomechanical performance of augmented and nonaugmented primary repair of the anterior cruciate ligament (ACL) following transection at the femoral end during a 12-month postoperative observation. Forty sheep were randomly assigned to nonaugmented or augmented primary ACL repair using a polyethylene terephthalate (PET) band. At two, six, 16, 26 and 52 weeks postoperatively four sheep in each group were sacrificed and biomechanical testing performed. Compared with nonaugmented primary ACL repair, the PET-augmented repair demonstrated superior biomechanical results from 16 weeks postoperatively onwards in terms of anterioposterior (AP) laxity, tensile strength and ligament stiffness. The augmentation device works as a stress shield during the ligament healing process. The nonaugmented ACL repair also resulted in ligament healing, but the biomechanical properties were at a significantly lower level. These results support the previously reported histological findings following augmented primary ACL repair. This animal study on the healing capacity of the ACL may provide some important contributions to how primary healing in certain types of ruptures can be achieved. I.