lar below, is a
comparatively common injury, and results from a violent wrench of the
foot. It may be incomplete or complete. When the foot is plantar
flexed at the moment of injury, the displacement is generally
_forward_ with a tendency outward. The talus comes to rest on the
third cuneiform and cuboid bones, the foot being abducted, inverted,
and displaced medially. In a large proportion of cases the
dislocation is compound, more or less of the talus being forced
through the skin (Fig. 100).

[Illustration: FIG. 100.--Compound Dislocation of the Talus.]

When the foot is dorsiflexed at the moment of injury the displacement
is _backward_, but this is rare, as is also _dislocation to one or
other side_, and _dislocation by rotation_, in which the talus is
rotated in its socket. In all these injuries the body of the talus
loses its normal relationship with the malleoli.

An attempt should be made to reduce the dislocation under anaesthesia,
the limb being placed in the same position as for reduction of
dislocation of the ankle. While traction is made upon the foot, an
assistant presses directly on the displaced bone and endeavours to
manipulate it into position. In incomplete dislocations this usually
succeeds, but it not infrequently fails in those which are complete,
and under these circumstances it may be necessary to chisel through
the lateral malleolus to admit of reduction, or to excise the talus.
In most cases of compound dislocation also, this bone should be
removed.

#Sub-taloid Dislocation.#--In this dislocation, which results from the
same kinds of violence as the last, the talus retains its position in
the tibio-fibular socket, and the calcaneus and navicular, with the
rest of the foot, are carried away from it. The body of the talus,
therefore, maintains its normal relationship with the malleoli--a
point of importance in the differential diagnosis between this injury
and dislocation of the talus. The displacement is usually incomplete,
and the foot may either pass backward and medially, or backward and
laterally. When the foot passes _backward and medially_, the head of
the talus projects on the outer part of the dorsum, resting on the
cuboid. The dorsum of the foot is shortened, the heel lengthened, the
toes adducted, and the medial border of the foot raised. The lateral
malleolus is unduly prominent, and reaches nearly to the sole.

[Illustration: FIG. 101.--Radiogram of Fracture-Dislocation of Talu