The medial ligaments and the ACL restrain anteromedial laxity of the knee

Purpose The purpose of this study was to determine the contribution of each of the ACL and medial ligament structures in resisting anteromedial rotatory instability (AMRI) loads applied in vitro. Methods Twelve knees were tested using a robotic system. It imposed loads simulating clinical laxity tests at 0° to 90° flexion: ±90 N anterior–posterior force, ±8 Nm varus–valgus moment, and ±5 Nm internal–external rotation, and the tibial displacements were measured in the intact knee. The ACL and individual medial structures—retinaculum, superficial and deep medial collateral ligament (sMCL and dMCL), and posteromedial capsule with oblique ligament (POL + PMC)—were sectioned sequentially. The tibial displacements were reapplied after each cut and the reduced loads required allowed the contribution of each structure to be calculated. Results For anterior translation, the ACL was the primary restraint, resisting 63–77% of the drawer force across 0° to 90°, the sMCL contributing 4–7%. For posterior translation, the POL + PMC contributed 10% of the restraint in extension; other structures were not significant. For valgus load, the sMCL was the primary restraint (40–54%) across 0° to 90°, the dMCL 12%, and POL + PMC 16% in extension. For external rotation, the dMCL resisted 23–13% across 0° to 90°, the sMCL 13–22%, and the ACL 6–9%. Conclusion The dMCL is the largest medial restraint to tibial external rotation in extension. Therefore, following a combined ACL + MCL injury, AMRI may persist if there is inadequate healing of both the sMCL and dMCL, and MCL deficiency increases the risk of ACL graft failure.

“Ramp lesions” of the posterior segment of the medial meniscus: what is repaired? An anatomical and histological study

Background: Lesions of the posterior segment of the medial meniscus are the most common intra-articular lesions associated with anterior cruciate ligament injury. “Ramp lesions” have been defined as a tear in the peripheral attachment of the posterior horn of the medial meniscus (PHMM). These injuries are difficult to detect on preoperative MRI, whereas their prevalence with arthroscopy can be as high as 24%. The management of “Ramp lesions” isn’t collegiale. There are only two publications in PUBMED concerning anatomic and histological description posterior menisco-tibial ligament ( PMTL). The objective of this histological study was to analyze the posterior segment of the medial meniscus and its meniscosynovial junction, in order to identify the PMTL. Methods: We dissected ten cadaveric knees. A posterior approach to the posteromedial capsule was used. Therefore, we were able to access the posterior segment of the medial meniscus and its meniscosynovial junction. The proximal capsule, the posterior segment of the medial meniscus, the entire meniscal capsular-tibial junction, and a fragment of the tibia were removed together. For each part, three section slices were prepared for the histological study. Results: Macroscopically, the meniscotibial attachments was pellucid, homogeneous. The meniscocapsular attachments was pellucid, homogeneous but appeared to be strengthened at both the anterior and posterior portions of the capsule. The microscopic study of meniscosynovial jonction revealed loose collagen fibers, oriented but not organized parallel, network with rare fibroblasts and and adipocytes, several capillaries were seen. No histological differences were observed, and the 2 attachments merged at a common attachment site on PHMM. Conclusion: For us, “Ramp lesion” is a tear of common attachment of menicocapsular and meniscotibial junctions of PHMM. This attachment is vascularized, an outfit is possible and biomechanical role is increasingly identified.