Acute Deltoid Injury in Ankle Fractures: A Biomechanical Analysis of Different Repair Constructs

Abstract

Category: Trauma; Ankle Introduction/Purpose: The importance of the deltoid ligament in the congruency of the tibiotalar joint is well known. The current trend is to repair it in cases of acute injuries in the context of ankle fractures, however, there is no information on how it should be reconstructed. The objective of this study was to compare different deltoid ligament repair types in an ankle fracture cadaveric model. Methods: 16 cadaveric foot-ankle-distal tibia specimens were used to conduct the study. All samples were prepared as a supination external rotation ankle fracture model. An axial load and cyclic axial rotations were applied on every specimen using a specifically designed frame. This test was performed without deltoid injury, with deltoid injury and finally with the ligament reconstructed. The reconstruction was performed in 4 different ways (anterior, posterior, middle, combined) using 4 specimens per group. Medial clear space (MCS) was measured for each condition on simulated weight-bearing and gravity stress radiographs. Reflective markers were utilized in tibia and talus, registering through a motion analysis system the kinematics, to record the tibiotalar uncoupling. Statistical analysis was performed using the SPSS software. Results: In all cases, the MCS increased significantly on gravity stress radiographs after damaging the deltoid ligament. There was no increase in the MCS on load radiographs. After repair, in all cases, the MCS was normalized. Kinematically, after damage the tibiotalar uncoupling increased significantly, decreasing after repair. All repairs significantly corrected the tibiotalar uncoupling, observing a significantly increased coupling effect (increased stiffness) with the combined repair. Conclusion: Our results show that deltoid repair recovers the tibiotalar coupling mechanism in an ankle fracture model. We suggest that the ideal repair should aim to repair the middle aspect of the deltoid ligament. The combined repair may lead to postoperative stiffness. Clinical studies are needed to prove these results and show clinically improved outcomes.