Optimization of Graft Fixation at the Time of Anterior Cruciate Ligament Reconstruction. Part II: Effect of Knee Flexion Angle

Background: There is no consensus about flexion angle of the knee at the time of graft fixation in anterior cruciate ligament reconstruction.

Purpose: To evaluate the effect of flexion angle at the final graft fixation on the positional relationship as well as the load between femur and tibia.

Study Design: Controlled laboratory study.

Methods: Six intact cadaveric knees were passively flexed and extended under 6 degrees of freedom with the robotic system developed in our laboratory, while their 3-dimensional paths were recorded. Anterior cruciate ligament reconstruction was performed with a single-socket technique using autogenous quadrupled hamstring tendons, while the graft was fixed at 0 degrees (group A), 20 degrees (group B), or 90 degrees (group C) with a constant initial tension of 44 N. The knees then repeated the same movement as before while the relative position between femur and tibia was recorded. The load in the femorotibial joint was also calculated based on the principle of superposition.

Results: Posterior displacement of the tibia compared with the normal knee was the smallest in group B at all flexion angles, while the load between tibia and femur in group B was also the smallest and the closest to the normal knee.

Conclusion: As the positional relationship as well as the load between femur and tibia in group B was the closest to that in the normal knee, 20 degrees of flexion is the most desirable of the positions tested for graft tensioning and fixation at the time of anterior cruciate ligament reconstruction.

Clinical Relevance: The tibia-femur position is well retained when the graft was fixed at 20 degrees of flexion in anterior cruciate ligament reconstruction.