Determination of time of biologic fixation after anterior cruciate ligament reconstruction with hamstring tendons.

Abstract

It has been unclear when a hamstring tendon graft becomes biologically fixed in the bone tunnel after anterior cruciate ligament reconstruction. Postoperative biomechanical testing and magnetic resonance images can indicate biologic fixation of the graft in the femoral bone tunnel. Prospective cohort study. Sixty-four patients were evaluated by serial biomechanical testing, magnetic resonance imaging, and second-look arthroscopy 2 years after surgery. Biologic fixation of the graft was confirmed radiographically by injecting a contrast medium into the femoral bone tunnel. Forty-two stable knees with graft fixation maintained a high stiffness (120% of normal) and showed low signal intensity in an early postoperative magnetic resonance image (12 +/- 8 months). Fourteen stable knees without graft fixation had gradually increased anterior displacement with nearly normal stiffness and high signal intensity. Five unstable knees with graft fixation retained low stiffness (70%) and showed late low signal intensity at 20 +/- 9 months. Three unstable knees without biologic fixation had rapidly increased anterior displacement, with half the stiffness of a normal knee. Postoperative low stiffness and high signal intensity might indicate late biologic graft fixation, predicting a possibility of postoperative anterior knee instability.