Diagnosis. The whole foot appears to be lengthened. The prominence due to the heel has disappeared; the upper articular surface of the astragalus can be felt, the tibia and the malleoli being nearer to the heel.
The condition can be differentiated from a fracture of both bones of the leg above the malleoli by the fact that in a forward dislocation the malleoli are further back than normal, while in a supramalleolar fracture they have moved forward with the foot.
Treatment. Reduction is readily effected by marked dorsal flexion of the foot, pressure being made in a forward direction upon the lower end of the tibia, and the foot pushed backward. Plantar flexion now completes the reduction. The after treatment is the same as in the backward form.
Lateral Dislocations. The other forms of dislocations seen in the ankle are those in a lateral direction, either inward or outward. The diagnosis is usually easy. The upper convex surface of the astragalus is directed toward the external malleolus and can be felt there. The inner border of the foot is raised; the outer rests upon the bed.
This form of dislocation is very frequently a compound one, or it is accompanied by fractures of the bones of the leg or of the astragalus; but it may occur without these injuries.
Treatment. The treatment of these lateral dislocations differs but little from that of fractures of the lower end of the tibia and fibula. Reduction is effected by adduction or abduction of the foot. The chief danger is from infection on account of the extensive injury of the skin and soft parts. If reduction is impossible, perform an arthrotomy.
Subastragaloid Dislocation. Two forms of dislocation can occur in the joint between the astragalus and the two tarsal bones (os calcis and scaphoid) with which it articulates. In the true subastragaloid form, the astragalus continues to articulate with the tibia and fibula, but it is displaced from its articulation with the os calcis and scaphoid. In the second form of subastragaloid dislocation, the astragalus is completely separated from its articulation with the bones of the leg as well as with the calcaneus and scaphoid. To this form the name total dislocation of the astragalus is given.
True Subastragaloid Dislocations. These dislocations may occur in four directions, inward, outward, forward, and backward.
Dislocation inward. The most frequent cause is a forcible adduction of the foot combined with violence acting in the direction of the long axis of the foot. The diagnosis can be made from the position of the foot. The foot is adducted and rotated inward, as in a case of clubfoot. The sole of the foot is directed inward. The inner edge of the foot is concave and shortened while the outer edge appears lengthened. The external malleolus and head of the astragalus are very prominent on the outer side of the foot. Below and behind the inner malleolus the scaphoid projects beneath the skin.
Dislocation Outward. This occurs after forced adduction of the foot. The symptoms are the opposite of those of the inward variety. The foot is in the position of a flat foot, its inner edge depressed and outer edge raised. The inner malleolus is close to the sole of the foot, and in front of it the head of the astragalus forms a prominence. The injury is not infrequently compound, so that the astragalus presents into the wound.