Dislocation Backward. The cause is usually a plantar flexion of the foot. The signs are very pronounced; the head of the astragalus can be seen and felt lying upon the upper surface of the scaphoid and cuneiform bones. The anterior portion of the foot is shortened while the heel is lengthened and the tendo Achillis is very prominent.
Dislocation Forward. This follows forced dorsal flexion of the foot, the patient falling forward after landing with his heels upon the ground. The diagnosis can be made because of the lengthened anterior portion of the foot and the shortened heel. An important point in the diagnosis of subastragaloid dislocation is the absence of any prominence due to the projection of the body of the astragalus, in front, behind, or to either side of the malleoli, as is seen in the case of the tibiotarsal dislocations. A second diagnostic point is the abnormal position of the calcaneus and scaphoid with relation to the malleoli and astragalus. The swelling is usually so great that a diagnosis is very difficult without the use of the X-ray.
Treatment of Subastragaloid Dislocations. Reduction can usually be effected in recent cases by manipulation and traction. In the inward variety the existing adduction is at first increased. Pressure is now made over the outer side of the adduction and the inner side of the foot, and the foot is then strongly abducted. In the outward variety, the abduction is first increased. Pressure is then made over the outer side of the foot until reduction is effected. In the backward variety, the plantar flexion is first increased and the foot is then strongly flexed in the opposite direction. In the forward type, forced dorsal flexion will effect reduction. The foot should be placed upon a posterior molded splint for three weeks, after which passive motions are begun. If the reduction is impossible, an arthrotomy with excision of the astragalus may be necessary.
Total Dislocation of the Astragalus. This form of dislocation is much more frequent than those of the ankle joint proper, or of the articulation between the astragalus, calcaneus, and scaphoid. The displacement of the astragalus may occur in one of six directions: forward; outward and forward; inward and forward; inward; backward, and by rotation.
The most frequent variety is the “outward and forward.” In this variety the foot is rotated markedly inward and the external malleolus is very prominent. The foot is in a clubfoot position. The dislocated astragalus can be felt as an irregular angular bone just below the external malleolus.
Treatment is the same as in subastragaloid dislocations.
Dislocation of the Metatarsal Bones. This may be either complete or incomplete at Lisfranc’s joint. It occurs most often in an upward direction. The dorsum of the foot is more convex than normal, while the sole of the foot is flattened. One can see and feel the displaced ends (upper) of the metatarsals on the dorsum of the foot. The foot is shortened and the toes point inward.
Dislocations of the individual metatarsal bones are much rarer. The middle ones are displaced upward, and the first and fifth, inward and outward respectively.
Dislocation of the Toes. This occurs most often in the metatarsophalangeal joint of the great toe after forcible flexion. The dislocation may be complete or incomplete. In the former case, the proximal end of the first phalanx and the dorsum of the foot are prominent, and the head of the metatarsal bone projects on the sole of the foot. The reduction of toe dislocations presents no difficulties.