Distribution of in situ forces in the anterior cruciate ligament in response to rotatory loads

Abstract

The anterior cruciate ligament (ACL) can be anatomically divided into anteromedial (AM) and posterolateral (PL) bundles. Current ACL reconstruction techniques focus primarily on reproducing the AM bundle, but are insufficient in response to rotatory loads. The objective of this study was to determine the distribution of in situ force between the two bundles when the knee is subjected to anterior tibial and rotatory loads. Ten cadaveric knees (50 k 10 years) were tested using a roboticluniversal forcemoment sensor (UFS) testing system. Two external loading conditions were applied: a 134 N anterior tibial load at full knee extension and 15", 30°, 60", and 90" of flexion and a combined rotatory load of 10 N m valgus and 5 N m internal tibial torque at 15" and 30" of flexion. The resulting 6 degrees of freedom kinematics of the knee and the in situ forces in the ACL and its two bundles were determined. Under an anterior tibial load, the in situ force in the PL bundle was the highest at full extension (67 k 30 N) and decreased with increasing flexion. The in situ force in the AM bundle was lower than in the PL bundle at full extension, but increased with increasing flexion, reaching a maximum (90 f 17 N) at 60" of flexion and then decreasing at 90". Under a combined rotatory load, the in situ force of the PL bundle was higher at 15" (21 k 11 N) and lower at 30" of flexion (14 f 6 N). The in situ force in the AM bundle was similar at 15" and 30" of knee flexion (30k 15 vs. 3 5 2 16 N, respectively). Comparing these two external loading conditions demonstrated the importance of the PL bundle, especially when the knee is near full extension. These findings provide a better understanding of the function of the two bundles of the ACL and could serve as a basis for future considerations of surgical reconstruction in the replacement of the ACL.

Pediatric ACL injuries: evaluation and management

“…Cadaveric work has found the greatest ACL tension at 0°or at 45°of flexion [41]; therefore, many authors recommend immobilization with casts at 10°-20°of flexion [42][43][44]. However, when each ACL bundle is examined independently, the AM bundle seems to tighten at about 60°of flexion, and the PL bundle tightens with extension [45]. In type II injuries with small displacements, aspiration of the hemarthosis may aid in reduction.…”

Reconstrução do ligamento cruzado anterior com a técnica de duplo feixe - avaliação no laboratório de biomecânica

“…Biomechanical studies on cadavers have already shown that the surgical technique that reconstructs both ACL bundles is able to offer better control over anterior translation of the tibia, as well as better control of knee rotation resulting, in theory, from posterolateral bundle reconstruction (9)(10)(11)(12)(13) .…”

“…This technique is very efficient in controlling tibial translation under the femur, but is not as efficient in controlling tibial rotation under the femur. Kinematic studies have demonstrated that ACL reconstruction with single--bundle technique is unable to reestablish the normal kinematics of the joint (9,13) .…”

“…Keywords -Rotation; Anterior Cruciate Ligament; Reconstruction; Biomechanics evolution in the surgical technique, fixation materials, graft sources, and rehabilitation protocols, there is still a percentage of these patients (10-30%) that do not evolve satisfactorily (6)(7)(8)(9) .…”

Application of a computerised navigation technique to assist arthroscopic anterior cruciate ligament reconstruction

“…However, large prospective series and metaanalyses conducted recently have shown that, despite correct tunnel placement, a significant number of patients experience persistent instability in the knee at follow-up especially in respect of rotational stability and also have abnormal International Knee Documentation Committee (IKDC) scores in as many as one fifth of patients who had undergone single-bundle ACL reconstruction [1]. Anatomical studies have shown that the ACL consists of two major functional bundles, namely the AM and the posterolateral (PL) bundle [2]. Several in vivo and in vitro studies have demonstrated the inability of single-bundle ACL reconstruction to restore intact knee rotational stability [3].…”