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

Purpose 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 degrees and 90 degrees of flexion (p = 0.001; p a parts per thousand currency signaEuro parts per thousand 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 degrees 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.