Biomechanical Analysis of Ankle Stability Following Deltoid Ligament Repair and Reconstruction

Background: The deltoid ligament has been shown to contribute to the stability of the ankle mortise, preventing valgus talar tilt, external rotation (ER), and translation. Research to date assessing the appropriateness of deltoid repair to reintroduce medial stability to a fractured ankle is unclear. Deltoid ligament reconstruction using autograft or allograft has been proposed in cases of chronic deltoid insufficiency. This biomechanical study sought to assess the stability offered by deltoid repair and reconstruction compared to the native deltoid ligament in its intact and defunctioned states. Materials and Methods: Twelve (six pairs) fresh frozen cadaveric lower extremities with intact deltoid ligaments underwent biomechanical assessment in a custom-made multiaxial testing apparatus. Each specimen was tested in plantarflexion/dorsiflexion (PF/DF), inversion/eversion (IV/EV), and internal rotation (IR)/ER and analyzed for angular range of motion (ROM) and stiffness. The specimens were tested with an intact deltoid ligament and following disruption via transection. Subsequently, paired specimens were randomized to either deltoid repair or reconstruction. A single double-loaded suture anchor was used to repair the deep and superficial deltoid ligaments. The tibialis anterior tendon was used as an autograft in the reconstruction group. Results: Normalized ROM and stiffness were significantly different in deficient specimens compared to all other groups during PF/DF. During IR/ER, the deficient ankle was significantly different from the intact and repair state. For IV/EV, deficient specimen ROM was significantly greater than the intact or repair states, while the stiffness for the deficient ankles was significantly less. Conclusion: Deltoid repair and reconstruction were comparable in returning the ankles to an intact state and conferring stability. These results suggest that in cases with insufficient or unstable deltoid ligament where repair is not possible, reconstruction has the potential to be a reliable alternative, but further studies are warranted to understand all advantages/disadvantages.