The immediate postoperative kinematic state after anterior cruciate ligament reconstruction with increasing peroperative tension

The last steps in anterior cruciate ligament (ACL) reconstruction are tensioning and fixation of the ligament. However, how much tension should be applied to the ligament in general or in each individual and in which position the ligament should be fixed remain unanswered questions. The purpose of this study was to investigate the effect of increasing ligament tension on the immediate postoperative kinematic state of the ACL-reconstructed knee. Nine cadaver knees were mounted in a mechanical measuring device based on a redesign of the Genucom knee testing system, so that the femur was fixed to a force plate and the moving tibia to a goniometer arm for registration of movement. The ligament was attached on the tibial side to a Kistler load cell and a turn-buckle for adjustment of ligament tension. The ligament was tensioned at 30° of flexion with 5, 33, 66, 99 and 132 N. The cadaver knees were tested with an intact ACL, after sacrifice of the ACL and after reconstruction of the ACL with an ABC ligament. Results showed that there was a significant decrease in knee motion when the tension was higher than 33 N. This resulted in an over-constrained knee with less anteroposterior translation, internal-external rotation and varus-valgus movement compared with the uninjured knee.