#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 Talus.]
In the _backward and lateral_ variety, the medial malleolus and head of the talus project unduly towards the medial side of the foot, which is abducted and everted.
In neither variety is there any mechanical obstacle to movement at the ankle-joint.
The _treatment_ is carried out on the same lines as for dislocation of the talus, reduction being effected without difficulty in most cases. If this fails, as it occasionally does, it may be necessary to excise the talus.
#Mid-tarsal or transverse tarsal dislocation#--that is, at the talo-navicular and calcaneo-cuboid articulations--is extremely rare. The distal segment of the foot is usually displaced towards the sole; the foot is foreshortened, the malleoli raised from the sole, the arch of the foot is lost, and the first row of tarsal bones projects on the dorsum. The treatment consists in reducing the displacement by manipulation, after which massage and movement are employed.
#Tarso-metatarsal Dislocations.#--One, several, or all of the metatarsals may be separated from the distal row of tarsal bones--the usual cause being a fall from a horse, the foot being fixed in the stirrup. The bases of the metatarsal bones are displaced laterally and towards the dorsum. The base of the second metatarsal and the first cuneiform are sometimes fractured. Reduction by manipulation is generally easy in dorsal dislocations, but may be difficult when the bones are displaced laterally. This may be due to fragments of bone or soft parts getting between the bones, and may necessitate operative interference. In old-standing dislocations, operation is to be advised only when locomotion is seriously interfered with.