Biomechanical study on human knee cadavers to compare results after non-augmented ACL suture repair and static and dynamic joint bridging augmentation across the arc of flexion, and after cyclic loading.
Suture repair of the acute ruptured anterior cruciate ligament (ACL) regained interest in the last decade. Previous non-augmented suture repair techniques did not restore anterior tibial translation (ATT), while approximation of the ruptured ends is an important condition to promote healing of the ruptured ACL. In contrast, suture repair with static or dynamic joint bridging augmentation techniques are performed on patients today. However, there is lack of objective evidence investigating how contemporary augmented suture repair techniques affect ATT across the full arc of flexion, and after cyclic loading of the knee (simulating postoperative rehabilitation).
(1) Non-augmented suture repair and (2) static joint bridging augmentation do not restore ATT compared to ACL-intact values across the arc of flexion of the knee, after cyclic loading. (3) Dynamic joint bridging augmentation restores ATT compared to ACL-intact values and significantly reduces ATT compared to ACL-deficient values across the arc of flexion of the knee, and maintains these values after cyclic loading.
Controlled laboratory study
Twelve human cadaveric knees were mounted in a test rig, and knee kinematics from 0° to 90° of flexion were recorded by use of an optical tracking system. Measurements were recorded without load and with 89-N anterior force. The knees were tested in the following states: ACL-intact, ACL-deficient, non-augmented suture repair (Marshall) after 10, 150 and 300 loading cycles, static joint bridging augmentation (Internal BraceTM) after 10, 150 and 300 loading cycles, and dynamic joint bridging augmentation (LigamysTM) after 10, 150 and 300 loading cycles.
Statistical analysis used mixed-model analysis comparing the effects of states for ATT across the arc of flexion. Post hoc SIDAK tests were applied in order to investigate differences across conditions while controlling for multiple comparisons. Level of significance was set at p<0.05.
After non-augmented suture repair and cyclic loading, ATT was significantly increased compared to the ACL-intact state (p=0.000), and ATT was not significantly decreased compared to the ACL-deficient state (p=1.000).
After both static and dynamic joint bridging augmentation directly postoperative, ATT was restored to normal values compared to the ACL-intact state (p=0.982) and this was maintained after cyclic loading (p=0.364).
However, after cyclic loading and compared to the ACL-deficient state, ATT was only significantly decreased after dynamic joint bridging augmentation (p=0.000), and not after static joint bridging augmentation (p=0.075),
Furthermore, after cyclic loading, dynamic joint bridging augmentation significantly decreased ATT compared to static joint bridging augmentation (p=0.028).
In contrast to non-augmented ACL suture repair and static joint bridging augmentation, dynamic joint bridging augmentation resulted in restoration of normal ATT values when compared to the ACL-intact knee, and significantly decreased ATT values when compared to the ACL-deficient knee, after cyclic loading of the knee, across the full arc of flexion.
Clinical Relevance: This study suggests that dynamic joint bridging augmentation can approximate the ruptured ends of the ACL directly postoperative and can maintain this after cyclic loading, which is an important condition to promote healing of the ruptured ACL.