The influence of the medial meniscus in different conditions on anterior tibial translation in the anterior cruciate deficient knee.

Objective: The purpose of this study was the evaluation of knee laxity in the ACL-deficient knee with combined meniscal tear, meniscal suture and partial medial meniscectomy.

Methods: Kinematics of the intact knee were determined in 18 human cadaver specimens in response to a 134-N anterior tibial load (aTT) as well as a combined rotatory load of 10 Nm valgus and 4 Nm internal tibial rotation using a robotic/universal force moment sensor testing system. The anterior cruciate ligament was resected. Subsequently, a vertical bucket-handle medial meniscal tear was created followed by a standard meniscus repair using horizontal inside-out stitches or a partial medial meniscectomy. Knee kinematics were calculated following every sub-step.

Results: A significant increase of anterior tibial translation was found in the ACL-deficient knee compared to the intact knee at 30° and 90° of flexion (p = 0.001; p ≤ 0.001). Additional tear of the medial meniscus significantly increased anterior tibial translation (p = 0.01). In response to a simulated pivot shift, anterior tibial translation of the intact knee did not increase significantly after ACL resection (p = 0.067). However, ACL deficiency with an additional medial meniscus tear led to a significant increase compared to the intact knee at 0° of flexion (p = 0.009).

Conclusions: Additional injury of the medial meniscus increased aTT as well as aTT under a combined rotatory load in the ACL-deficient knee whereas repair of the meniscus significantly decreased aTT. Therefore, the meniscus status does have a significant impact on knee kinematics in the ACL-deficient knee. The present biomechanical study further highlights the importance of preserving the meniscus especially in patients with additional ACL injuries.