Lateral location of the tibial tunnel increases lateral meniscal extrusion after anatomical single-bundle anterior cruciate ligament reconstruction

A balance between native footprint coverage and overlap of the anterolateral meniscal root in tibial tunnel positioning during anterior cruciate ligament reconstruction: A 3D MRI study

BACKGROUND

Tibial footprint of anterior cruciate ligament (ACL) is situated close to the anterior lateral meniscal root (ALMR) attachment.

PURPOSE

To investigate the impact of the size and location of the tibial tunnel for ACL reconstruction on the ACL footprint coverage and overlap to the ALMR.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty knee MRI scans from twenty healthy subjects were recruited, and three-dimensional (3D) tibia models were created to show the tibial attachment sites of ACL and ALMR. Surgical simulation of the tibial tunnel drilling was performed on each 3D model, entering the joint at an angle set at 60 degrees from the tibial plateau plane and 55 degrees from the posterior tibial condylar axis, with analysis for six different drill sizes; 7.5, 8, 8.5, 9, 9.5 and 10 mm; and nine locations; the center of the ACL attachment and eight locations 2% of the tibial width apart surrounding it. The width of the tibial plateau, the distance between ACL and ALMR attachment centers, and the size and location of the potential tibial tunnel were evaluated to determine association with the area of the ACL footprint coverage and ALMR overlap using a linear mixed effects model.

RESULTS

A large tunnel (p <.001), a central and anterior location (p <.029), and small tibial width (p =.015) were all associated with larger coverage of the ACL footprint. A large tunnel (p <.001), posteriorly and laterally located (p ≤ 0.001), and a small distance between the ACL and ALMR centers (p =.001) were significantly associated with a larger ALMR overlap. The association of the tunnel size to ALMR overlap reduced with a medial tunnel location.

CONCLUSIONS

The short distance between the centers of the ALMR attachment and native ACL footprint suggests that the ALMR will always be susceptible to overlap when the tibial tunnel is drilled in ACL reconstruction. Small alterations in tunnel location can lead to a statistically significant alteration with the amount of ALMR overlap. To minimize this overlap, whilst maintaining acceptable coverage of the ACL footprint, a tibial tunnel positioned in a medial or anteromedial location from the center of the ACL footprint is recommended.

Effect of Anterior Horn Tears of the Lateral Meniscus on Knee Stability

Background

Investigations on the biomechanical characteristics of the anterior horn of the lateral meniscus (AHLM) related to anterior cruciate ligament (ACL) tibial tunnel reaming have revealed increased contact pressure between the femur and tibia, decreased attachment area, and decreased ultimate failure strength.

Purpose/Hypothesis

The purpose of this study was to investigate the influence of a complete radial tear of the AHLM on force distribution in response to applied anterior and posterior drawer forces and internal and external rotation torques. We hypothesized that the AHLM plays an important role in knee stability, primarily at lower knee flexion angles.

Study Design

Controlled laboratory study.

Methods

A total of 9 fresh-frozen cadaveric knee specimens and a robotic testing system were used. Anterior and posterior drawer forces up to 89 N and internal and external rotation torques up to 4 N·m were applied at 0°, 30°, 60°, and 90° of knee flexion. A complete AHLM tear was then made 10 mm from the lateral border of the tibial attachment of the ACL, and the same tests performed in the intact state were repeated. Next, the recorded intact knee motion was reproduced in the AHLM-torn knee, and the change in the resultant force after an AHLM tear was determined by calculating the difference between the 2 states.

Results

In the torn AHLM, the reduction in the resultant force at 0° for external rotation torque (34.8 N) was larger than that at 60° (5.2 N; P < .01) and 90° (6.7 N; P < .01).

Conclusion

The AHLM played a role in facilitating knee stability against an applied posterior drawer force of 89 N and external rotation torque of 4 N·m, especially at lower knee flexion angles.

Clinical Relevance

This study provides information about the effects of AHLM injuries that may occur during single-bundle ACL reconstruction using a round tunnel.