CHAPTER IX.

DISLOCATIONS OF THE ANKLE AND FOOT.

DISLOCATIONS OF THE ANKLE.

DISLOCATION of the ankle-joint is not infrequent, but in most cases there is also fracture of one of the bones entering into the articulation; dislocation of the ankle without fracture only occurs in a forward or backward direction, and even in these forms the tip of one or both malleoli may be broken off. The commonest form of dislocationi.e. the dislocation outwards that

Of the two forms of dislocation uncomplicated by fracture, dislocation of the foot backwards is the more common. The tarsus is carried bodily backwards behind the tibio-fibular arch, which therefore lies in front of the astragalus and rests upon the scaphoid and cuboid bones. The accident generally results from severe indirect violence applied when the toes are pointed; the internal malleolus is not infrequently fractured. Dislocation forwards also occurs from indirect violence, but generally when the foot is in a position of excessive dorsal flexion.

FIG. 39.-DISLOCATION OF THE FOOT BACKWARDS.
The entire tarsus is carried backwards.

TREATMENT.-An anæsthetic is administered and an assistant fixes the leg whilst extension is applied to the foot; as downward traction is made, the deformity is increased in order to disentangle the edge

of the astragalus from the tibio-fibular arch against which it is lodged. When sufficient traction has been made, the foot is either flexed or extended according to the nature of the displacement; when the foot is displaced backwards, the plantar flexion of the foot is increased, the foot is pulled forcibly forwards and downwards, and then rapidly dorsi-flexed. In a dislocation of the foot forwards, movements in the reverse direction are practised; traction is made and the dorsal flexion is increased; then, while traction is maintained, the foot is pushed backwards and is finally plantar-flexed.

Movements should be begun on the day following the accident; the after-treatment will be practically that for fracture of the lower end of the tibia or fibula, as the case may be.

DISLOCATIONS OF THE FOOT.

SUB-ASTRAGALAR DISLOCATION.

In this type of injury the whole of the foot undergoes dislocation. with the exception of the astragalus, which remains in position

rests upon the upper surface of the scaphoid or the internal cuneiform. The posterior articular surface of the astragalus generally lies upon the anterior articular surface of the os calcis, the dislocation at the calcaneoastragaloid joint being only partial.

The injury is generally produced by indirect violence, such as occurs when a patient alights from a height upon the toes, which are deflected to one side, while the weight of the body forces the ankle and the astragalus forwards and to the other side. The lateral displacement depends upon the particular position of the foot when the violence is applied. In the usual form the foot is extended, and there is a prominence on the instep in the neighbourhood of the scaphoid due to protrusion of the head of the astragalus. The tendo Achillis is widely separated from the back of the tibia and is very tense, whilst the heel is unduly prominent.

TREATMENT.-Reduction is often very difficult owing partly to the tension of the tendo Achillis, and partly also to hitching of the sharp posterior edge of the articular surface of the astragalus in the interosseous groove of the os calcis; in some cases also the tendon of the tibialis anticus may be caught beneath the neck of the astragalus.

Before attempting reduction the patient should be anæsthetised, and an assistant must fix the leg with the knee fully flexed. The surgeon then grasps the foot with one hand over the instep and the other over the heel, and makes firm downward traction in order to disengage the astragalus; at the same time the toes should be depressed. When full extension has been made, the whole foot is pressed forwards by the hand over the heel, when the os calcis may be forced into place, dorsal flexion being employed as the dislocation becomes reduced. These manipulations often have to be repeated several times before they succeed; they may be unsuccessful even after repeated trials.

Should manipulations fail, the dislocation cannot be left unrelieved, on account of the extreme uselessness of the foot which results and the risk of sloughing of the skin; an incision should therefore be made along the inner border of the foot, commencing about an inch above the internal malleolus, and running downwards and forwards over the neck of the astragalus. This exposes the tendon of the tibialis anticus, and allows the nature of the obstacles to reduction to be investigated. Should the main obstacle be the slipping of the tibialis anticus tendon beneath the neck of the astragalus, the head of the bone can be levered up, and the tendon hooked aside whilst the foot is forcibly pushed forwards into place.

Should it still be found impossible to reduce the dislocation, the best treatment is to proceed immediately to excision of the astragalus, which can be effected partly through the incision already made, and partly through a somewhat similar one on the outer side. This operation and the after-treatment are described fully in Vol. I. p. 332. In cases in which the dislocation has remained unreduced for some time, excision of the astragalus, with division of any adhesions which prevent the foot coming forward, is the best plan, and gives a satisfactory result.

DISLOCATION OF THE ASTRAGALUS ALONE.

The astragalus may be detached from the bones of the leg above and those of the foot below, and may thus be separated completely from all its connections. It may be displaced in various directions; most commonly it passes directly forwards, or forwards and to one side, but in some cases it may be dislocated backwards. The injury is caused by severe violence, and is frequently complicated by fracture of the bone itself; it may be compound, either as a direct result of the violence, or from sloughing of the skin which is tightly stretched over the prominent head of the bone.

It usually results from violence applied to the foot in the fully plantarflexed position, as may occur in alighting from a height upon the toes, or in machinery accidents, where the limb is violently pulled and twisted. Dislocation backwards is produced by extreme violence applied whilst the foot is fully dorsi-flexed, but this is a very rare accident.

TREATMENT.-The knee should be flexed under full anæsthesia and the leg fixed by an assistant. Traction is exerted upon the foot so as to separate the os calcis as far as possible from the tibio-fibular arch. While this is maintained at its utmost extent, attempts are made to press the astragalus back into position between the os calcis and the tibia. The separation of the bones of the foot from those of the leg may be aided by dividing the tendo Achillis. It is seldom possible to get the bone into place by these means, however, and in that case immediate operation is imperative, otherwise gangrene of the skin over the projecting bone is almost certain to follow. The best plan is to make an incision on each side of the front of the ankle-that on the inner side commencing an inch above the articular surface, just in front of the malleolus, and running downwards and forwards to the internal cuneiform bone; that on the outer, running from just above and in front of the external malleolus downwards and forwards to the cuboid. In deepening the inner incision the tendon of the tibialis anticus should be preserved, and the tissues lying over the astragalus should be separated from the bone so as to enable the condition of the parts to be investigated; it may then be possible to press the astragalus into position by making forcible traction. upon the foot. Should the surgeon fail to replace the bone it must be removed. The functional result should be excellent.

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FIG. 41.-DISLOCATION OF THE ASTRAGALUS FORWARDS AND INWARDS. The toes are pointed and the astragalus projects very markedly on the inner side.

OTHER DISLOCATIONS OF THE TARSUS AND METATARSUS.

The remaining dislocations occurring about the foot need no detailed description.

Cases of dislocation at the transverse tarsal joint have been recorded; should this form occur, it must be reduced under an anesthetic by making firm traction upon the front part of the foot.

The metatarsal bones may be dislocated from the tarsus either individually or as a whole. This accident is usually the result of extreme violence, and is generally accompanied by other injuries.

Reduction is effected under anæsthesia by making traction upon the front part of the foot and applying pressure over the prominent bases of the metatarsal bones.

Dislocation at the metatarso-phalangeal joints also occurs. These injuries are very like the corresponding dislocations occurring in the hand (see p. 48), but they are of much greater rarity; the treatment is exactly similar.