The Effect of Initial Graft Tension in Anterior Cruciate Ligament Reconstruction on the Mechanical Behaviors of the Femur-Graft-Tibia Complex During Cyclic Loading

Abstract

Background: Initial graft tension influences clinical results of anterior cruciate ligament reconstruction.

Hypothesis: Under repetitive loading conditions, the effect of initial graft tension on the biomechanical behavior of the femur-graft-tibia complex may depend on the graft and the fixation.

Study Design: Ex vivo biomechanical laboratory study.

Methods: After anterior cruciate ligament reconstruction, initial graft tension of 20, 80, or 140 N was applied to the complex for 2 minutes. Then, a cyclic force-relaxation test was performed for 5000 cycles so that the graft was stretched by 2 mm.

Results: In a patellar tendon graft with interference screws, the average peak load values at the 5000th cycle were 105, 157, and 205 N for the complexes with initial tension of 20, 80, and 140 N, respectively. In a flexor tendon graft with interference screws, the values were 27, 41, and 39 N. In a flexor tendon graft with Endobutton fixation, the values were 17, 40, and 77 N.

Conclusions: Considering the tension of the normal anterior cruciate ligament (16 to 87 N), an initial tension of 20 N appears to be high enough for a patellar tendon graft. For a flexor tendon graft with interference screws, an increase in initial tension above 80 N has no biomechanical advantages.