An Anteromedial Reconstruction Mimicking the Deep Medial Collateral Ligament Stress-Shields the ACL In Anteromedial Rotatory Instability – Biomechanical Validation of Different Anteromedial Reconstruction Techniques

An Anteromedial Reconstruction Mimicking the Deep Medial Collateral Ligament Stress-Shields the ACL In Anteromedial Rotatory Instability – Biomechanical Validation of Different Anteromedial Reconstruction Techniques

Florian Gellhaus, MD, GERMANY Peter Behrendt, MD, GERMANY Adrian Deichsel, MD, GERMANY Martin Lind, MD, PhD, Prof., DENMARK Alina Albert, M.Sc., GERMANY Nina Backheuer, Medical student, GERMANY Michael J. Raschke, MD, Prof., GERMANY Andreas Seekamp, Prof, GERMANY Christoph Kittl, MD, MD(res), GERMANY

University Hospital Münster, Department of Trauma, Hand and Reconstructive Surgery, Münster, NRW, GERMANY


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Anatomic Location

Anatomic Structure

Diagnosis / Condition

Ligaments

Sports Medicine


Summary: Anteromedial Rotatory Instatility (AMRI) by an injury of the sMCL and dMCL does increase the forces acting on an ACL reconstruction, reconstructing the MCL complex with a DB or flat sMCL with additional flat dMCL reconstruction do reduce these forces again whilst a SB sMCL reconstruction does not.


Background

The aim of this study was to compare the stress-shielding effects of different types of anteromedial reconstructions (AMR) mimicking the deep medial collateral ligament (dMCL) in combination with a single-bundle reconstruction of the superficial medial collateral ligament (sMCL) to restrain anteromedial rotatory instability (AMRI). It was hypothesized that the resulting load within the anterior cruciate ligament in AMRI would be better controlled by an AMR in comparison to a single-bunde sMCL reconstruction.

Methods

A kinematic rig was used to test 8 unpaired knees with imposed tibial displacing loads (5 Nm external/internal rotation, and combined 89 N anterior translation plus external rotation (anteromedial drawer test, AMD). Testing was performed in the intact, sMCL/dMCL sectioned, and AM reconstructed states. Four different AMR were assessed: (1) Modified Lind reconstruction; (2) Single-bundle sMCL reconstruction (SB); (3) dMCL/sMCL combination; and (4) flat sMCL/dMCL reconstruction. The tibial part of the anterior cruciate ligament was released and fixed to sutures, which were trans-osseously connected to a load cell. Resulting load of the ACL fibers was examined by repeated measures 2-Way-ANOVA with Bonferroni post-testing.

Results

Sectioning the sMCL/dMCL significantly (p<.05) increased ACL load during the AMD across all flexion angles and during ER in 0-60° of flexion compared to the native state (79.2 N vs. 116.0 N at 30°, p < .01). Resulting ACL load was significantly (at least p<.05) reduced by all AMR (at 30° flexion: flat MCL 71.0 N, Lind 67.5 N, SBMCL+T1 56.6 N) except the SB (at 30 ° flexion: 86.12 N) during AMD without being significantly different to the intact state (p>.05). In ER, AMR restored ACL force to the native knee being significantly different to the MCL sectioned state (p<.05) at 30° and 60° of flexion (except SB). IR was not significantly (p>.05) influenced by AMR considering that the ACL and posterior oblique ligament were functionally intact.

Conclusion

In this biomechanical in vitro setting, a comparison of four anteromedial procedures revealed that the addition of an AMR restored the native ACL load profile in a combined sMCL/dMCL-deficient knee. All AMR except the SB technique achieved excellent load control. In AMRI with a simultaneous ACL reconstruction an AMR should be considered in addition to a single-bundle sMCL reconstruction. This strategy may further decrease the likelihood of ACL failure in ACL/MCL combined injuries, considering that MCL instability is a significant risk factor for recurrent ACL instability.