The Journal of Bone and Joint Surgery, Vol 74, Issue 8 1201-1206, Copyright © 1992 by Journal of Bone and Joint Surgery, Inc
Assessment of the posterior malleolus as a restraint to posterior subluxation of the ankle
WG Raasch, JJ Larkin and LF Draganich
Section of Orthopaedic Surgery and Rehabilitation Medicine, University of Chicago, Illinois 60637.
We assessed the function of the posterior malleolus, the anterior
tibiofibular ligament, and the fibula with regard to posterior stability of
the talus in ten ankles of cadavera. Posteriorly directed loads of as much
as 200 newtons were applied. Two groups of ankles were tested; in the first
group, three ankles in which the ligamentous and osseous structures were
intact were tested after transection of the posterior capsule and after
removal of 10, 20, 30, and 40 per cent of the articular surface of the
distal end of the tibia from the posterolateral corner. In the second
group, seven ankles were tested in the same sequence, but the anterior
tibiofibular ligament and the fibula were transected before sectioning of
the articular surface. Compared with the results for the intact ankle, the
experiments on the first group demonstrated less than one millimeter of
additional posterior translation of the talus after removal of as much as
40 per cent of the articular surface. In the second group, in which the
anterior tibiofibular ligament and the fibula had been transected,
significant posterior translation of the talus (more than three
millimeters) occurred after removal of 30 per cent of the articular surface
(p < 0.01). This represented a 160 per cent increase in translation
compared with that in the intact ankle.