Poster 297: Deep medial collateral ligament reconstruction of the knee restores rotational stability throughout full range of motion while contemporary MCL reconstruction only does in extension
Authors: Han Shuyang , Gold John , Sij Ethan , Laughlin Mitzi , Amis Andrew , Williams Andy , Lowe Walter , Borque Kyle 
Published: August 2023

Objectives:

The past decade has taught the importance of identifying and treating the concomitant injuries that frequently occur at the time of ACL rupture. Failure to do so can result in increased stresses on the ACL graft and subsequently increased risk of failure. While the focus has largely been on the menisci and the anterolateral soft tissues, recent studies have highlighted high frequency at which injuries to the medial structures occur in previously presumed isolated ACL tears and the increased risk of poor outcomes when they are not addressed. Injuries to the medial ligament complex result in valgus and anteromedial rotatory instability (AMRI). Historic MCL reconstruction techniques have focused on the superficial MCL in an effort to restore valgus stability while frequently ignoring the importance of the deep MCL in controlling tibial external rotation. The recent recognition of the importance of the medial ligament complex has led to multiple studies revisiting medial sided anatomy and questioning contemporary MCL reconstruction techniques. The objective of this study is to assess and compare the ability of a contemporary medial collateral ligament (MCL) reconstruction and a deep MCL (dMCL) reconstruction to restore rotational and valgus stability to the knee.

Methods:

Six pairs fresh-frozen cadaveric knee specimens were included and with intact soft tissue, the distal femur and tibia were potted in PVC pipes to facilitate biomechanical testing using a customized multi-axial knee activity simulator. Four states were tested: 1) intact 2) after sectioning of the sMCL and dMCL, 3) contemporary MCL reconstruction as described by LaPrade et al, and 4) dMCL reconstruction. In each state, the knees were tested under four loading conditions at varying flexion angles (0°, 20°, 40°, 60° and 90°): 8 Nm valgus torque, 5 Nm tibial external rotation torque, 90N anterior drawer, and combined 90 N anterior drawer plus 5 Nm tibial external rotation torque.

Results:

Transection of the sMCL and dMCL resulted in increased laxity with the application of the valgus torque, external rotation torque, and combined anterior drawer plus external rotation at all flexion angles. dMCL reconstruction restored external rotation stability to intact levels (all p<0.05) throughout all degrees of flexion (Figure 1), yet dMCL reconstruction did not restore valgus stability at any flexion angle (Figure 2). Contemporary MCL reconstruction restored valgus and external rotation stability at 0° and 20° and valgus stability at 40° (p<0.01). In response to a combined anterior drawer plus tibial external rotation, the dMCL restored stability back to the intact level at 20° and improved stability between 40° and 90° flexion (Figures 3 and 4). In contrast, the contemporary MCL reconstruction did not restore stability at any degree of flexion (p>0.05).

Conclusions:

Deep MCL reconstruction restored rotational stability to the knee throughout range of motion but did not restore valgus stability. The contemporary MCL reconstruction restore stability only near full extension.