Abstract
Objective: Lateral meniscal posterior root (LMPR) is an important stabilizer for knee joint, providing the stability during tibia forward shifting and internal rotating. It is still controversial that whether the LMPR tear (LMPRT) should be repaired together with ACL reconstruction. This study aims to investigate the effects of LMPR on knee stability with intact ACL. Methods: Eight cadaver knees were used and performed the biomechanical kinematics tests in orders of: Group A: the LMPR was intact; Group B: the LMPR was cut off from its tibial end; Group C: the LMPRT has been repaired. 1) An internal rotation moment (5 Nm) was given to the tibia, then the internal rotation angle of the tibia was measured; 2) An forward shifting force (134 N) was given to the tibia, then the anterior displacement of the tibia was measured; 3) An internal rotation moment (5 Nm) and a valgus moment (10 Nm) were given to the tibia, then the internal rotation angle and the anterior displacement was measured. The stability was inferred from smaller rotation angle and displacement, and all of the angles and displacements were measured at knee flexion of 0°, 30°, 60° and 90°, respectively. Results: Comparing to Group A, the internal rotation angle in Group B was increased significantly at knee flexion of 30° (p = 0.025), 60° (p = 0.041), 90° (p = 0.002); the anterior tibia displacement in Group B was increased significantly at knee flexion of 30° (p = 0.015), 60° (p = 0.024); at knee valgus, the internal rotation angle was also increased significantly at knee flexion of 60° (p = 0.011), 90° (p = 0.037). Comparing to Group B, the internal rotation angle in Group C was decreased significantly at knee flexion of 30° (p = 0.030), 60° (p = 0.019), 90° (p = 0.021); the anterior displacement in Group C was decreased significantly at knee flexion of 30° (p = 0.042), 60° (p = 0.037); at valgus, the internal rotation angle was also decreased significantly at knee flexion of 60° (p = 0.013), 90° (p = 0.045). Comparing to Group A, only the internal rotation angle (p = 0.047) and anterior displacement (p = 0.033) in Group C were increased at knee flexion of 30°. Conclusion: In simulated knee with intact ACL, LMPRT can still lead to the notable internal rotational instability at knee flexion from 30° to 90°, as well as the anterior shift instability at knee flexion from 30° to 60°. LMPRT repair help to improve the internal rotation stability at 30° and restore it at 60° to 90°, and improve the anterior shift stability at 30° and restore it at 60°.
Highlights
Meniscal posterior root (MPR) refers to the attachment site of meniscus posterior horn to the intercondylar region on tibial plateau. (Wang et al, 2021)
With the increasing of knee flexion, the LMPR will replace the anterior cruciate ligament (ACL), becoming the primary stabilizer for preventing the over-internal rotation and over-forward shift. (Pache et al, 2018). This biomechanical kinematics cadaver study found that the Lateral MPRT (LMPRT) can lead to notable internal rotational instability when knee flexion ranged from 30° to 90°, when ACL was tensioned by the valgus load in the test, the LMPRT can lead to notable internal rotational instability when knee flexion ranged from 60° to 90°
What’s more, our results found that the LMPRT repairing can completely restore the stability in most cases, and significantly improve the internal rotation and anterior shift stability at knee flexion of 30° compared with the LMPRT group
Summary
Meniscal posterior root (MPR) refers to the attachment site of meniscus posterior horn to the intercondylar region on tibial plateau. (Wang et al, 2021). Meniscal posterior root tear (MPRT) is defined as a tear or avulsion injury within 1 cm of the MPR tibia attachment point. Lateral MPRT (LMPRT) is associated with sports injury and trauma. MPR plays an extremely important role in transforming the load and maintaining knee stability. LMPRT leads to meniscus extrusion and kinematic changes during the joint motion, because of lack of the tibial anchor, which is equal to an invalid meniscus. It has been known that the lateral MPR is another essential stabilizer for knee joint (the second), following the anterior cruciate ligament (ACL). As the knee flexion angle increasing, the lateral MPR will become the primary stabilizer, providing the main stability of the internal rotation. An intact lateral MPR can prevent the tibia over-forward shift and internal rotation during motions and sports injury
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