Optimization of graft fixation at the time of anterior cruciate ligament reconstruction. Part I: effect of initial tension.

BACKGROUND: Although anterior cruciate ligament (ACL) reconstructions are frequently performed, little is known about the effect of initial tension on an ACL graft at the time of its fixation.
PURPOSE: The objective of this study was to evaluate the effects of initial tension on the relative position and the load between femur and tibia during passive motion. STUDY
DESIGN: Controlled laboratory study.
METHODS: Seven cadaveric knees underwent a passive flexion-extension movement from 0 degrees to 90 degrees with a robotic system developed in the authors' laboratory under 6 degrees of freedom, while their 3-dimensional paths were recorded. A single-socket ACL reconstruction was performed with an autogenous quadrupled hamstring tendon graft, while the knees underwent the same movement as before with the initial graft tension of 22 N (group A), 44 N (group B), or 88 N (group C) at 20 degrees. The relative position between the femur and the tibia was recorded, and the load in the femorotibial joint was calculated using the principle of superposition.
RESULTS: The tibia in group C was most posteriorly positioned among the 3 groups (an average posterior translation of 0.6, 1.3, and 2.6 mm in groups A, B, and C, respectively). The tibia also moved proximally and laterally with external and valgus rotation with an increase in initial tension, and consequently the load in the femorotibial joint increased at all flexion angles.
CONCLUSION: With an increase in initial tension, the tibia moved posterolaterally with external and valgus rotation, and consequently the contact force in the femorotibial joint increased. CLINICAL RELEVANCE: Excessive initial tension at the time of ACL reconstruction may potentially bring deleterious effects to the articular surface, leading to cartilage degeneration.