An analysis of the function of the posterior talofibular ligament.

The function of the posterior talofibular ligament was studied using an apparatus which subjected the ankle joint to a measured torque and allowed the simultaneous recording of rotatory movements in two planes. Thirty osteoligamentous preparations of ankle joints were examined, half in the sagittal and horizontal planes and the remainder in the sagittal and frontal planes. Successive section of the lateral collateral ligaments was performed, including, in particular, selective division of the short and long fibres of the posterior talofibular ligament. The function of this ligament was investigated in combination with the other two collateral lateral ligaments, with the calcaneofibular ligament alone, and finally as the only remaining intact ligament. The posterior talofibular ligament plays only a supplementary role in ankle stability when the lateral ligament complex is intact. After rupture of the anterior talofibular and the calcaneofibular ligaments, however, the short fibres of the posterior ligament restrict internal and external rotation, talar tilt, and dorsiflexion, while its long fibres inhibit only external rotation, talar tilt, and dorsiflexion. As the posterior talofibular ligament has no independent stabilizing function in the intact ankle joint, an isolated rupture of this ligament is unlikely.