A Retensionable Inlay/Onlay Hybrid Double-Bundle Medial Collateral Ligament Reconstruction Produces Superior Restoration of the Uninjured State When Compared to a Single-Bundle Inlay Reconstruction.

BACKGROUND: Traditional superficial medial collateral ligament (sMCL) reconstruction techniques have not consistently restored native laxity. PURPOSE/HYPOTHESIS: The purpose of this study was to develop a retensionable inlay/onlay hybrid medial collateral ligament (MCL) reconstruction through comparison to a biomechanically and clinically validated reconstruction. It was hypothesized that increasing the distal footprint on the tibia through a double-bundle construct and a retensionable construct would better restore native laxity. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 27 cadaveric knees were tested on a 6 degrees of freedom robot system. Knees were tested with valgus and external rotation (ER). Each knee was tested in a native state and an injured state after sectioning of the sMCL. One of 3 reconstructions using an anterior tibialis allograft was then performed: (1) single-bundle inlay reconstruction, (2) double-bundle inlay/onlay hybrid reconstruction with tibial fixation at both the proximal and distal (PD) tibial insertions of the sMCL footprint, or (3) double-bundle inlay/onlay hybrid reconstruction with tibial fixation at the anterior and posterior (AP) aspects of the distal sMCL tibial insertion. The constructs used retensionable variable-loop devices, allowing for retensioning after knee cycling. The constructs were tested after cycling and retensioning. RESULTS: Sectioning of the sMCL resulted in significantly increased laxity compared to the native state for both valgus and ER laxity testing (P < .001). After flexion cycling and subsequent retensioning, both AP and PD double-bundle reconstructions demonstrated significantly higher restoration of stability compared to cycled single-bundle reconstructions (P < .001). Both double-bundle reconstructions were significantly closer to the native state than the single-bundle reconstruction for valgus rotation (P < .001) and ER (P < .05). For valgus testing, there was no difference between retensioned double-bundle constructs and the native state, with a pooled valgus difference of 0.56° (95% CI, 0.05°-1.06°; P = .032). For ER testing, no differences were found between the retensioned AP double-bundle and the native state (P = .836), suggesting more complete restoration was achieved by AP double-bundle restoration. CONCLUSION: A retensionable inlay/onlay hybrid double-bundle MCL reconstruction with a larger femoral footprint and 2 distal anterior-posterior tibial footprints produced superior restoration of the uninjured state when compared to a traditional single-bundle inlay reconstruction. For double-bundle reconstructions, an anterior-posterior tibial fixation achieved mean values closer to the native state than proximal-distal fixation. CLINICAL RELEVANCE: A double-bundle retensionable inlay/onlay hybrid reconstruction is an effective alternative to a single-bundle inlay reconstruction technique. The double-bundle reconstruction may better withstand early unrestricted range of motion during postoperative phases.