Effect of Notchplasty in Anterior Cruciate Ligament Reconstruction: A Biomechanical Study in Porcine Knees (SS-74)

Abstract

Introduction: In anterior cruciate ligament (ACL) reconstruction, notchplasty is frequently performed by many surgeons. It is not well understood how notchplasty may effect tunnel placement and knee kinematics. The purpose of this study is to investigate the biomechanical effects of notchplasty on the ACL reconstructed knee. The hypothesis is that notchplasty will affect knee biomechanics in ACL reconstructed knee. Methods: Twelve (n 12) mature, fresh frozen porcine knees were tested using a robotic/universal force/moment sensor (UFS) testing system. All ACL reconstructions were performed via arthroscopy using a threeportal technique. Four knee states were compared: 1) intact ACL 2) ACL-Deficient 3) Anatomic single bundle (SB) ACL reconstruction and 4) Anatomic SB ACL reconstruction with a 5 mm notchplasty. The same tunnel was used for states 3 and 4. The graft was fixed at 60° of knee flexion and tensioned at 80-N with an Endobutton on the femur and a post-screw on the tibia. All knees were subjected to the following loading conditions: an 89-N anterior tibial load to test anterior tibial translation (ATT) and a 4 N-m internal rotation (IR) and external rotation (ER) tibial torque. The knee kinematics and in situ force obtained from the different knee conditions were compared. The data (mean standard deviation), was analyzed (Prism GraphPad Version 5.0a) using a two-tailed Paired t-test with the level of significance set at P 0.05. Results: There was no significant differences between pre and post notchplasty in ER at 30° (full extension in porcine knee) and 60° of flexion (p 0.05). However, a significant difference was found between pre and post notchplasty in ATT at 30° and 60° of flexion (p 0.05). In-situ force in anatomic single bundle reconstruction with notchplasty was significant lower than intact and anatomic reconstructed ACL pre-notchplasty at 30 °, 60° and 90° flexion of the knee (p 0.05). In response to an IR tibial torque, there were not significant differences between pre and post notchplasty at 30° of knee flexion (p 0.05). However, a significant difference was found between pre and post notchplasty in IR at 60° (p 0.05) of knee flexion. Conclusion: The results of this study showed that notchplasty did not result in an increase in ER at 30° and 60° degrees of knee flexion and IR at 30° degree of knee flexion; but lead to an increase in ATT at 30° and 60° degrees of knee flexion and in IR at 60° degree of knee flexion. Notchplasty had more effect on anterior stability than rotational stability. This change in knee kinematics could be detrimental to a bone healing and graft ligamentization and could lead to graft failure.