The Anterior Fibers of the Superficial MCL and the ACL Restrain Anteromedial Rotatory Instability

Abstract

Background: There is limited knowledge about how the anterior cruciate ligament (ACL) and capsuloligamentous structures on the medial side of the knee act to control anteromedial rotatory knee instability. Purpose: To investigate the contribution of the medial retinaculum, capsular structures (anteromedial capsule, deep medial collateral ligament [MCL], and posterior oblique ligament), and different fiber regions of the superficial MCL to restraining knee laxity, including anteromedial rotatory instability. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen human cadaveric knees were tested using a 6 degrees of freedom robotic testing system in a position-controlled mode. Loads of 10 N·m valgus rotation, 5 N·m tibial external rotation, 5 N·m tibial internal rotation, and 134 N anterior tibial translation in 5 N·m external rotation were applied at different flexion angles. The motion of the intact knee at 0° to 120° of flexion was replicated after sequential excision of the sartorial fascia; anteromedial retinaculum; anteromedial capsule; anterior, middle, and posterior fibers of the superficial MCL; the deep MCL; the posterior oblique ligament; and the ACL. The reduction in force/torque indicated the contribution of each resected structure to resisting laxity. A repeated-measures analysis of variance with a post hoc Bonferroni test was used to analyze the relative force and torque changes from the intact state. Results: The superficial MCL was the most important restraint to valgus rotation from 0° to 120° and provided the largest contribution to resisting external rotation between 30° and 120° of knee flexion, gradually increasing from 25.2% ± 7.4% at 30° to 36.9% ± 15.4% at 90°. The posterior oblique ligament contributed significantly to resisting valgus rotation only in extension (17.2% ± 12.1%) but was the major restraint to internal rotation at 0° (46.7% ± 13.1%) and 30° (30.4% ± 17.7%) of flexion. The sartorial fascia and anteromedial retinaculum resisted ER at all knee flexion angles ( P < .05) and was the single most important restraint in the extended knee (19.5% ± 11%). The capsular structures (anteromedial capsule and deep MCL) had a combined contribution of 20% ± 11.5% at 0° and 23.4% ± 10.5% at 120° of knee flexion but were less important from 30° to 90°. The ACL was the primary restraint to anterior tibial translation in external rotation between 0° and 60° of flexion (50.2% ± 16.9% at 30°), but the superficial MCL was more important at 90° to 120° of knee flexion (36.8% ± 16.4% at 90°). The anterior, middle, and posterior regions of the superficial MCL contributed differently to the simulated laxity tests. The anterior fibers were the most important part of the superficial MCL in resisting external rotation and combined anterior tibial translation in external rotation. Conclusion: The superficial MCL not only was the primary restraint to valgus rotation throughout the range of knee flexion but also importantly contributed to resisting anterior tibial translation in external rotation, particularly in deeper flexion in the cadaveric model. The anterior fibers of the superficial MCL are the most important superficial MCL fibers in resisting anterior tibial translation in external rotation. This study suggests that a medial reconstruction that reproduces the function of the posterior MCL fibers and posterior oblique ligament may not best control anteromedial rotatory instability. Clinical Relevance: Based on these data, there is a need for an individualized medial reconstruction to address different types of medial injury patterns and instabilities.

Noninvasive and Reliable Quantification of Anteromedial Rotatory Knee Laxity: A Pilot Study on Healthy Individuals

“… 33 , 37 Those injuries can lead to both valgus and anteromedial rotatory instability depending on the injury pattern. 21 , 22 The deep MCL and the anterior portion of the superficial MCL are the major restraints for AMRI, 4 , 9 , 27 and injuries of these structures result in a significant increase in anterior laxity of the medial tibial plateau when anterior force or external rotation is applied. 34 Clinical reports about patients who have AMRI are sparse, as are reports on outcomes after nonsurgical or surgical treatment.…”

Verletzungen des medialen Bandapparats des Kniegelenks

“…Die biomechanische Rolle des AMR ist noch nicht final geklärt, allerdings konnte in einer robotischen Studie gezeigt werden, dass extensionsnah die anteromediale Rotationsinstabilität (AMRI) neben dem VKB durch das AMR und die anteromediale Kapsel gehemmt wird, wohingegen erst ab 60°-Flexion das sMCL diese Rolle übernimmt [ 19 ].…”

“…Hierbei war die Ruptur des POL eine Grundvoraussetzung für eine AMRI. Neuere radiologische und biomechanische Studien [ 5 , 19 , 40 , 42 ] zeigen jedoch, dass eine POL-Ruptur selten ist und die AMRI hauptsächlich durch die medialen (sMCL, dMCL) und anteromedialen Strukturen gehemmt wird. Basierend auf diesen Daten haben Wierer et al.…”

“…Biomechanische Studien demonstrieren, dass die einzelnen Fasern des sMCL verschiedene Arten von Instabilitäten hemmen [ 19 ]. Es konnte z.…”

All the menisco‐ligamentary structures of the medial plane play a significant role in controlling anterior tibial translation and tibial rotation of the knee. Cadaveric study of 29 knees with the Dyneelax® laximeter

“…The PMC includes fibres that cross the joint posteromedially, and the posterior oblique ligament (POL) may be identified amongst them [ 13 ]. The functions of each of these structures have been described over time [ 12 , 19 , 29 ]. The superficial MCL is the primary passive restraint to the valgus and an important medial restraint to external tibial rotation.…”