The In Situ Force and Contribution of Each Ligamentous Band of the Deltoid Ligament in Ankle Joint Stability: A Cadaveric Biomechanical Study.

BACKGROUND

Each band of the deltoid ligament cooperatively contributes to stability of the medial side of the ankle joint. Investigating the function of each band of the deltoid ligament is essential to assess abnormalities and develop treatment options.

PURPOSE: To evaluate the changes in ankle kinematics when each band of the deltoid ligament is injured and to measure the in situ force of each ligamentous band in intact ankle kinematics.

STUDY

DESIGN

Descriptive laboratory study.

METHODS

A total of 8 healthy fresh-frozen cadaveric legs were examined by applying forces through eversion and external rotation of the ankle joint using a 6 degrees of freedom robotic system. The deltoid ligament was separated into 6 discrete bands: tibionavicular ligament, tibiospring ligament, tibiocalcaneal ligament (TCL), anterior tibiotalar ligament, superficial posterior tibiotalar ligament (sPTTL), and deep posterior tibiotalar ligament; the bands were then sequentially transected. A loading test was performed in each model, and the changes in ankle motion and in situ force of each ligamentous band were measured using the robotic system.

RESULTS

When an eversion force was applied to the intact ankle, the in situ force of the sPTTL was 21.6 N in dorsiflexion and that of the TCL was 19.4 N in plantarflexion, both of which were significantly greater than those of the other ligamentous bands. Additionally, the amount of eversion under eversion loading increased significantly by 3.3° with sPTTL resection in dorsiflexion and by 4.2° with TCL resection in plantarflexion.

CONCLUSION

The TCL and sPTTL play important roles among the ligamentous bands of the deltoid ligament. The sPTTL played a more significant role in ankle dorsiflexion, whereas the TCL played a more significant role in ankle plantarflexion.

CLINICAL RELEVANCE: The TCL and sPTTL should receive attention in the treatment of deltoid ligamentous injuries.