Biomechanical Effect on Joint Stability of Including Deltoid Ligament Repair in an Ankle Fracture Soft Tissue Injury Model With Deltoid and Syndesmotic Disruption
Pablo Mococain MD
Department of Orthopaedic Surgery
When I was thinking of a project to do during my stay with Duke’s Foot and Ankle team back in 2017, one of my first ideas was to try to understand the role of the deltoid ligament better. I have always wondered why we left the medial side of the ankle unattended when dealing with ankle fractures. We know that the deltoid ligament is the primary ankle stabilizer, but we rarely repaired it. In other joints, such as the knee or the elbow, when a primary ligamentous stabilizer is injured, surgeons perform a primary repair to try to restore joint biomechanics, provide native stability, allow safe early range of motion and avoid later instability which can lead to joint degeneration or malalignment.
An article by Dr. Nunley (Jones, C. R., & Nunley, J. A. Journal of Orthopaedic Trauma. 2015; 29(5), 245–249.) caught my attention, as he described a case series of bimalleolar equivalent ankle fractures in which they used a syndesmotic screw in one group and a deltoid ligament repair in the second group. They reported no difference in functional scores at five years. This article finally stimulated us to design our project.
We tried to analyze if a single syndesmotic screw versus a deltoid repair alone could restore ankle joint native stability. One of the first difficulties we had to deal with was that there is no standardized deltoid repair technique. Where to insert the anchors? How many should we use? Moreover, could we recreate similar conditions in our lab compared to the real clinical situation? We chose to use one anchor for the deep portion of the ligament and one for the superficial layer.
Our outcomes showed that deltoid repair was at least as stable as a syndesmotic screw, and even more efficient when testing anterior stability. Nevertheless, neither deltoid repair nor syndesmotic fixation on their own could restore normal ankle stability. When performing both interventions, all parameters went back to normal, except for external rotation stability.
Based on our findings, we think that there is room to improve when treating unstable ankle fractures. Deltoid ligament repair offers measurable additional stability to the ankle, even after the syndesmosis is fixed.
We still need to solve several issues regarding the deltoid ligament, as how much damage creates sufficient instability, identify when a patient will benefit from a repair, and how to repair it in a standardized way.
Additional laboratory and clinical studies need to be performed to help us better understand the importance of the medial side of the ankle joint.