The Control of Anteromedial Rotatory Instability Is Improved With Combined Flat sMCL and Anteromedial Reconstruction.

Behrendt, Peter; Herbst, Elmar; Robinson, James R.; von Negenborn, Leslie; Raschke, Michael J.; Wermers, Jens; Glasbrenner, Johannes; Fink, Christian; Herbort, Mirco; Kittl, Christoph

Abstract

In patients evaluated with a combined valgus and AM rotatory instability, a flat sMCL and an additional AM reconstruction may be superior to an isolated SB sMCL reconstruction.; In a cadaveric model, AMRI resulting from an injured sMCL and dMCL complex could not be restored by an isolated SB sMCL reconstruction. A flat MCL reconstruction or an additional AM procedure, however, better restored medial knee stability.; Both the superficial medial collateral ligament (sMCL) and the deep MCL (dMCL) contribute to the restraint of anteromedial (AM) rotatory instability (AMRI). Previous studies have not investigated how MCL reconstructions control AMRI.; The purpose was to establish the optimal medial reconstruction for restoring normal knee kinematics in an sMCL- and dMCL-deficient knee. It was hypothesized that AMRI would be better controlled with the addition of an anatomically shaped (flat) sMCL reconstruction and with the addition of an AM reconstruction replicating the function of the dMCL.; Controlled laboratory study.; A 6 degrees of freedom robotic system equipped with a force-torque sensor was used to test 8 unpaired knees in the intact, sMCL/dMCL sectioned, and reconstructed states. Four different reconstructions were assessed. The sMCL was reconstructed with either a single-bundle (SB) or a flattened hamstring graft aimed at better replicating the appearance of the native ligament. These reconstructions were tested with and without an additional AM reconstruction. Simulated laxity tests were performed at 0°, 30°, 60°, and 90° of flexion: 10 N·m valgus rotation, 5 N·m internal and external rotation (ER), and an AM drawer test (combined 134-N anterior tibial drawer in 5 N·m ER). The primary outcome measures of this force-controlled setup were anterior tibial translation (ATT; in mm) and axial tibial rotation (in degrees).; > .05). Combined flat MCL and AM reconstruction restored knee kinematics closest to the intact state. - CLINICAL RELEVANCE - CONCLUSION - BACKGROUND - PURPOSE/HYPOTHESIS - STUDY DESIGN - METHODS - RESULTS