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

Abstract

Background: 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. Purpose/Hypothesis: 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. Study Design: Controlled laboratory study. Methods: 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). Results: Sectioning the sMCL/dMCL increased valgus rotation, ER, and ATT with the simulated AM draw test at all flexion angles. SB sMCL reconstruction was unable to restore ATT, valgus rotation, and ER at 30°, 60°, and 90° of flexion to the intact state ( P < .05). Flat MCL reconstruction restored valgus rotation at all flexion angles to the intact state ( P > .05). ER was restored at all angles except at 90°, but ATT laxity in response to the AM drawer persisted. Addition of an AM reconstruction improved control of ATT relative to the intact state at all flexion angles ( P > .05). Combined flat MCL and AM reconstruction restored knee kinematics closest to the intact state. Conclusion: 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. Clinical Relevance: 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.

Single-Strand “Short Isometric Construct” Medial Collateral Ligament Reconstruction Restores Valgus and Rotational Stability While Isolated Deep MCL and Superficial MCL Reconstruction Do Not

“…When combined with an sMCL limb, stability was restored to the intact state. This was followed by Behrendt et al, 5 who tested 5 different constructs. They determined that it was possible to restore stability when an anteromedial reconstruction, placed in similar position to the dMCLR used in Miyaji et al 26 and the present study, was combined with a flat sMCL limb.…”

“…The lack of attention to rotatory stability is reflected in the multitude of surgical reconstruction techniques that have been developed to restore valgus stability, 10,18,21,24,46 usually with a superficial medial collateral ligament (sMCL) limb, while only recently have reconstructions included a deep MCL (dMCL) limb to restore rotatory stability. 5,20,26,40 While the MCL is the most injured ligament of the knee, surgical techniques for its repair and reconstruction have received less attention than the cruciate ligaments and the posterolateral corner, likely as a result of its excellent healing potential in the isolated setting. 8,12,13,25,29,31,38 This has begun to change, as multiple recent studies have highlighted the increased anterior cruciate ligament (ACL) rerupture rate if medial-sided instability is not addressed at the time of ACL reconstruction (ACLR), likely due to increased forces on the ACL graft.…”

“…In response, 2 novel techniques have been described, including an sMCL limb combined with a dMCL or ''anteromedial'' limb, which have successfully restored valgus and rotational stability. 5,26 While these constructs represent significant advances in the treatment of medial-sided knee injuries, the authors of this study wished to assess whether the same results could be accomplished using a single-strand construct in an effort to decrease the costs, the chances of tunnel convergence, and the complexity of surgical technique. 6,11 The decision was made to focus on the most common injury pattern noted in the clinical setting: an injury to the dMCL and sMCL with the POL remaining intact.…”

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

“…This behavior of the different fiber bundles of the sMCL suggests that a single-strand reconstruction cannot imitate the broader, flatter native ligament. Indeed, Behrendt et al 4 have shown that a flat sMCL reconstruction was more effective in restraining valgus tibial rotation and ER. However, only the addition of an anteromedial reconstruction fully restored medial knee kinematics in an sMCL/dMCL-deficient knee.…”

A New Algorithm to Treat Chronic Combined ACL/MCL Injuries: Let's Come Back to the “Rotatory Instability Test”

“…For isolated dMCL reconstruction associated with an ACLR, a gracilis can be used percutaneously to reconstruct the dMCL. 3 For dMCL + sMCL reconstruction, an anteromedial reconstruction using gracilis can be performed to control external rotation and can be combined with a flat sMCL reconstruction 2 to biomechanically best restore medial knee stability. In all MCL surgeries, the position of femoral insertion of the graft is critical.…”