286 



THE ARTICULATIONS 



occurs in lateral dislocations of ginglymoid joints, but the astragalus undergoes a partial rotation 

 round an antero-posterior axis drawn through its own centre, so that the superior surface, instead 

 of being directed upward, is inclined more or less inward or outward according to the variety of 

 the displacement. 



The ankle-joint is more frequently sprained than any joint in the body, and this may lead 

 to acute synovitis. In these cases, when the synovial sac is distended with fluid, the bulging 

 appears principally in the front of the joint, beneath the anterior tendons, and on either side, 

 between the Tibialis anticus and the internal lateral ligament on the inner side, and between the 

 Peroneus tertius and the external lateral ligament on the outer side. In addition to this, bulging 

 frequently occurs posteriorly, and a fluctuating swelling may be detected on either side of the 

 tendo Achillis. 



Chronic synovitis may result from frequent sprains, and when once this joint has been 

 sprained it is more liable to a recurrence of the injury than it was before ; or it may be tuber- 



FIG. 191. Section of the right foot near its inner border, dividing the tibia, astragalus, navicular, internal 

 cuneiform, and first metatarsal bone, and the first phalanx of the great toe. (After Braune.) 



cular in its origin, the disease usually commencing in the astragalus and extending to the joint, 

 though it may commence as a synovitis the result probably of some slight strain in a tubercular 

 subject. 



Excision of the ankle-joint is not often performed for two reasons. In the first place, 

 disease of the articulation for ^yhich this operation is indicated is frequently associated with 

 disease of the tarsal bones, which prevents its performance ; and, secondly, the foot after 

 excision is frequently of very little use ; far less, in fact, than after a Symes's amputation, which 

 is often, therefore, a preferable operation in these cases. Excision may, however, be attempted 

 in cases of tubercular arthritis, in a young and otherwise healthy subject, where the disease is 

 limited to the bones forming the joint. It may also be required after injury where the vessels 

 and nerves have not been damaged and the patient is young and free from visceral disease. 

 The excision is best performed by two lateral incisions. One commencing two and a half inches 

 above the external malleolus, carried down the posterior border of the fibula, round the end of 

 the bone, and then forward and downward as far as the calcaneo-cuboid joint, midway between 

 the tip of the external malleolus and the tuberosity on the fifth metatarsal bone. Through this 

 incision the fibula is cleared, the external lateral ligament is divided, and the bone sawn through 

 about half an inch above the level of the ankle-joint and removed. A similar curved incision is 

 now made on the inner side of the foot, commencing two and a half inches above the lower end 

 ot the tibia, carried down the posterior border of the bone, round the internal malleolus. and 

 forward and downward to the tuberosity of the navicular bone. Through this incision the tibia 

 is cleared in front and behind, the internal lateral, the anterior and posterior ligaments divided, 

 and the end of the tibia protruded through the wound by displacing the foot outward, and sawn 

 off' sufficiently high to secure a healthy section of bone. The articular surface of the astragalus 

 is now to be sawn off or the whole bone removed. In cases where the operation is performed 

 for tubercular arthritis the latter course is probably preferable, as the injury done by the saw is 

 frequently the starting point of fresh caries; and after removal of the whole bone the shortening 

 is not appreciably increased, and the result as regards union appears to be as good as when two 

 sawn surfaces of bone are brought into apposition. 



