# Deltoid Ligament Augmentation Replacing Syndesmotic Fixation for the Treatment of Ankle Fracture With Syndesmotic Instability and Deltoid Ligament Rupture: A Cadaveric Study

## TL;DR

This study shows that strengthening the deltoid ligament can stabilize ankle fractures as effectively as traditional syndesmotic fixation, avoiding the need for screws.

## Contribution

The study introduces a biomechanical alternative to syndesmotic fixation using deltoid ligament augmentation for ankle fractures.

## Key findings

- DL augmentation showed better resistance to medial malleolar space widening under external rotation and eversion forces.
- There were no significant differences in tibiofibular space widening between the two groups during rotation and eversion tests.
- DL augmentation can restore the tibiofibular space to a certain extent, making it a potential alternative to syndesmotic fixation.

## Abstract

Ankle fracture with both deltoid ligament (DL) rupture and syndesmotic diastasis is often treated by syndesmotic fixation after fibular fixation. However, a second operation may be needed to remove the internal fixation, and screw breakage/misplacement may occur. The present study aimed to explore the mechanism and feasibility of DL augmentation instead of syndesmotic fixation from the perspective of biomechanics.

The CT data (in DICOM format) of a 33‐year‐old man were used to create a finite element model. External rotation stress and eversion stress were applied to the model, and the medial clear space (MCS) and tibiofibular clear space (TCS) were evaluated. In a separate experiment, preserved lower limb specimens were fixed on a hydraulic loading frame before undergoing DL augmentation and syndesmotic fixation in random order. A mechanical testing device was used to apply external rotation stress (4 N·m) and eversion stress (2.5 N·m) to the two groups (DL augmentation or syndesmotic fixation). The MCS and TCS were measured and compared between the two groups.

In the finite element study, the MCS widening was lesser and the TCS widening was greater in the DL augmentation group than in the syndesmotic fixation group in both the external rotation and eversion tests. Nine specimens were analyzed in the biomechanical tests. There were no significant differences between the two groups in the widening of the TCS in the rotation tests (p = 0.093, Hodges–Lehmann median difference = −0.79, 95% confident interval: −1.70~0.27) and eversion tests (p = 0.237, HLD = −0.84, 95% CI: −2.57~1.09). However, the widening of the MCS was significantly lesser in the DL augmentation group than in the syndesmotic fixation group during the rotation tests (p = 0.036, HLD = 3.57, 95% CI: 0.40~6.41) and eversion tests (p = 0.018, HLD = 4.36, 95% CI: 1.84~7.35).

Compared with syndesmotic fixation, DL augmentation has better resistance to medial malleolar space widening under both external rotation and eversion forces and can restore the tibiofibular space to a certain extent. These results suggest that DL augmentation alone is a potential alternative to syndesmotic fixation for Weber‐type C ankle fractures from a biomechanical point of view.

A biomechanical study verifying that deltoid ligament augmentation can be an alternative to syndesmotic fixation for stabilizing both the medial malleolar and the syndesmosis in selective patients with Weber C ankle injuries.