Tibiocalcaneal Augmentation of Deltoid Ligament Repair Improves Ankle Stability: A Robotic Investigation of Ankle Biomechanics.

BACKGROUND

The deltoid ligament can tear in association with an ankle fracture or a syndesmotic injury or independently. Previous biomechanical research has shown that the optimal surgical treatment method for an anterior deltoid tear is repair with tibiocalcaneal augmentation. However, tibiocalcaneal augmentation is technically challenging to perform, as there is a risk of damage to neurovascular structures in the medial ankle.

PURPOSE

To determine if tibiotalar augmentation is sufficient to stabilize the ankle in the setting of a deltoid tear.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 10 cadaveric ankles were mounted to a 6 degrees of freedom robotic arm. Each specimen underwent biomechanical testing in 9 states: (1) intact, (2) anterior deltoid cut, (3) anterior deltoid repair, (4) anterior deltoid repair + tibiotalar augmentation, (5) anterior deltoid repair + tibiotalar augmentation + tibiocalcaneal augmentation, (6) posterior deltoid cut, (7) removal of tibiocalcaneal augmentation, (8) removal of tibiotalar augmentation, and (9) removal of anterior deltoid repair. Additionally, 6 tests were run under a 5-N·m load: (1) eversion at neutral, (2) eversion at 25° of plantarflexion, (3) external rotation at neutral, (4) external rotation at 25° of plantarflexion, (5) plantarflexion, and (6) dorsiflexion.

RESULTS

Anterior and complete tears significantly increased ankle laxity compared with the intact state on all tests (+5.6° and +12.0° in eversion at 25° of plantarflexion, respectively; < .0001). Anterior repair restored external rotation to the intact state for both anterior and complete tears, but it remained significantly more lax in eversion at 25° of plantarflexion (+2.9° [ = .0007] and +5.0° [ < .001], respectively). Tibiotalar augmentation showed no significant improvement, while tibiocalcaneal augmentation restored eversion stability to the intact state. No significant reductions in range of motion were found for any surgical state compared with the intact state.

CONCLUSION

Tibiotalar augmentation did not restore eversion stability to the intact state, but tibiocalcaneal augmentation restored eversion stability to the intact state for both anterior and complete tears. While this surgical technique may be technically challenging, it has a strong stabilizing effect on the ankle joint. Future research is necessary to further improve the safety and simplicity of this technique.

CLINICAL RELEVANCE

Clinicians may consider adding tibiocalcaneal suture tape augmentation to deltoid ligament repair to improve eversion stability.