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. 2025 Jul;53(8):1921-1930.
doi: 10.1177/03635465251339820. Epub 2025 May 15.

Optimizing the Control of Anteromedial Rotatory Knee Instability: A Biomechanical Validation of Different Anteromedial Reconstruction Techniques

Florian Gellhaus  1   2 , James R Robinson  3 , Martin Lind  4 , Adrian Deichsel  5 , Matthias Klimek  5 , Nina Backheuer  1 , Michael J Raschke  5 , Andreas Seekamp  1 , Peter Behrendt  1   2   6 , Christoph Kittl  5
Affiliations

Optimizing the Control of Anteromedial Rotatory Knee Instability: A Biomechanical Validation of Different Anteromedial Reconstruction Techniques

Florian Gellhaus et al. Am J Sports Med. 2025 Jul.

Abstract

Background: Anteromedial rotatory instability (AMRI) can result from combined injury to the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) complex (superficial and deep [sMCL and dMCL]).

Hypothesis: Adding an oblique anteromedial (AM) limb to an sMCL reconstruction improves the control of AMRI.

Study design: Controlled laboratory study.

Methods: A 6 degrees of freedom robotic setup simulated clinical laxity in 9 unpaired knees under the following tests: 5-N·m external rotation (ER), 8-N·m valgus rotation (VR), and AM drawer (combined 89-N anterior tibial translation and 5-N·m ER). Knees were tested intact after cutting the sMCL and dMCL and after 5 different reconstructions: modified Lind, short sMCL, and sMCL with the addition of an AM graft limb with 3 different obliquities.

Results: After short sMCL reconstruction, AM drawer and ER laxity were not significantly different from either the MCL-deficient state or the intact state. VR was reduced from the MCL-deficient state between 0° and 60° of flexion but not at 90°. For combined sMCL + AM reconstructions, VR was reduced as compared with the MCL-deficient state at all flexion angles. AM drawer laxity and ER laxity were also reduced, similar to the intact state, except at 30° where, for the more oblique T1 and T2 AM reconstructions, laxity was less than in the intact state. The modified Lind reconstruction reduced AM drawer and ER laxity from the MCL-deficient state to values similar to the intact state at all flexion angles. VR laxity was also reduced at all flexion angles, similar to the intact knee at 0° to 30°. However, it was not as good at restraining AM drawer and ER when compared with the sMCL reconstructions with more oblique AM limbs.

Conclusion: AMRI appears to be better restrained by adding an oblique AM graft limb to an sMCL reconstruction, replicating the function of the sMCL and dMCL in a cadaveric model. The tibial attachment of the AM limb should be anterior to the sMCL, but its precise attachment on the tibia is less important. This offers surgical flexibility, which may be helpful in avoiding anterior cruciate ligament tibial tunnel coalition. The femoral attachment on the posterior medial epicondyle is critical to optimize graft isometry.

Clinical relevance: Adding an AM limb to a medial reconstruction optimizes the control of AMRI at time zero. The tibial attachment site is less critical, offering surgical flexibility.

Keywords: ACL; AMRI; MCL; biomechanics; reconstruction.

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Conflict of interest statement

The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
Illustration of tested reconstructions. (A) Modified Lind technique: semitendinosus tendon left attached to the tibia and to the femur in the posterior part of the medial epicondyle, then fixed distally at the tibial attachment of the sMCL. Additional suture anchors were used to fix both limbs of the graft 1.5 cm below the joint line. (B) Single-bundle sMCL reconstruction with 3 versions of an additional AM reconstruction (sMCL + AM) using different tibial attachments: T1, the tibial attachment of the anterior fibers of the native deep medial collateral ligament; T2, a point 2 cm posterior to the anterior cortex and 2 cm distal to the joint line; T3, the distal insertion site of the semitendinosus tendon. (C) A short sMCL reconstruction: a single-bundle reconstruction from the femoral sMCL attachment to a point 1.5 cm below joint line along the course of the native sMCL. AM, anteromedial; sMCL, superficial medial collateral ligament.
Figure 2.
Figure 2.
Anteromedial drawer test. Anterior tibial translation (millimeters) with application of an 89-N anterior drawer force, with the knee in 5 N·m of external rotation. Testing was performed in the intact knee after cutting of the sMCL and dMCL and after each medial reconstruction (n = 9). Data are presented as mean ± SD. *P < .05. **P < .01. ***P < .001. AM, anteromedial; dMCL, deep medial collateral ligament; sMCL, superficial medial collateral ligament.
Figure 3.
Figure 3.
External rotation test. Tibial external rotation (degrees) with application of a 5-N·m external rotation torque in the intact knee after cutting of the sMCL and dMCL and after each medial reconstruction. Data are presented as mean ± SD. *P < .05. **P < .01. ***P < .001. AM, anteromedial; dMCL, deep medial collateral ligament; sMCL, superficial medial collateral ligament.
Figure 4.
Figure 4.
Valgus rotation test. Valgus rotation with an applied 8 N·m of valgus force in the intact knee after cutting of the sMCL and dMCL and after each medial reconstruction. Data are presented as mean ± SD. *P < .05. **P < .01. ***P < .001. AM, anteromedial; dMCL, deep medial collateral ligament; sMCL, superficial medial collateral ligament.
Figure 5.
Figure 5.
Internal rotation test. Internal rotation with an applied 5 N·m of internal rotation torque in the intact knee after cutting of the sMCL and dMCL and after each medial reconstruction. Data are presented as mean ± SD. *P < .05. **P < .01. AM, anteromedial; dMCL, deep medial collateral ligament; sMCL, superficial medial collateral ligament.
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