Abstract
Background: It has been unclear when a hamstring tendon graft becomes biologically fixed in the bone tunnel after anterior cruciate ligament reconstruction.
Hypothesis: Postoperative biomechanical testing and magnetic resonance images can indicate biologic fixation of the graft in the femoral bone tunnel.
Study Design: Prospective cohort study.
Methods: 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.
Results: 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.
Conclusion: Postoperative low stiffness and high signal intensity might indicate late biologic graft fixation, predicting a possibility of postoperative anterior knee instability.
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