Excision of the Os Calcis.—In those comparatively rare cases in which the os calcis is alone affected, the rest of the tarsus and the ankle-joint being healthy, a considerable difference of opinion exists as to the proper course to be followed. By some surgeons it is considered best merely to gain free access to the diseased bone, and then remove by a gouge all the softened and altered portions, leaving a shell of bone all round, of course saving the periosteum and avoiding interference with the joint. This operation requires no special detailed instruction. We find many surgeons, among them Fergusson and Hodge, supporters of this comparatively modest operation. The author has many times performed this operation with excellent results. Even when nothing but periosteum is left, the new bone becomes strong and of full size.
Excision of the whole of the diseased bone at its joints, with or without an attempt to leave some of the periosteum, has been deemed necessary by others. Holmes, who has had considerable experience, removes the bone at once by the following incisions, without paying any reference to the periosteum:—
Operation.—An incision ([Plate III.] fig. f.) is commenced at the inner edge of the tendo Achillis, and drawn horizontally forwards along the outer side of the foot, somewhat in front of the calcaneo-cuboid joint, which lies midway between the outer malleolus and the end of the fifth metatarsal bone. This incision should go down at once upon the bone, so that the tendon should be felt to snap as the incision is commenced. It should be as nearly as possible on a level with the upper border of the os calcis, a point which the surgeon can determine, if the dorsum of the foot is in a natural state, by feeling the pit in which the extensor brevis digitorum arises. Another incision is then to be drawn vertically across the sole, commencing near the anterior end of the former incision, and terminating at the outer border of the grooved or internal surface of the os calcis, beyond which point it should not extend, for fear of wounding the posterior tibial vessels. If more room be required, this vertical incision may be prolonged a little upwards, so as to form a crucial incision. The bone being now denuded by throwing back the flaps, the first point is to find and lay open the calcaneo-cuboid joint, and then the joints with the astragalus. The close connections between these two bones constitute the principal difficulty in the operation on the dead subject; but these joints will frequently be found to have been destroyed in cases of disease. The calcaneum having been separated thus from its bony connections by the free use of the knife, aided, if necessary, by the lever, lion-forceps, etc., the soft parts are next to be cleaned off its inner side with care, in order to avoid the vessels, and the bone will then come away.[74]
Attempts may occasionally be made in such an operation to save a portion of periosteum in attachment to the soft parts, but success or failure in this seems to have very little effect on the future result.
Hancock's Method.—A single flap was formed in the sole, with the convexity looking forwards, by an incision from one malleolus to the other.
Greenhow's Method.—Incisions made from the inner and outer ankles, meeting at the apex of the heel, and then others extending along the sides of the foot, the flaps being dissected back so as to expose the bone and its connections.[75]
Excision of Astragalus.—A curved incision on the dorsum of the foot extending from one malleolus to the other, and as far forwards as the front of the scaphoid. The chief caution required is to divide all ligaments which hold the bone in place, and dissect it clean on all other parts before meddling with its posterior surface where the groove exists for the flexor longus pollicis tendon near which the posterior tibial vessels and nerve lie.[76]
Excision of Astragalus and Scaphoid.—An incision similar to the anterior one in Syme's amputation at the ankle. The flap was then turned back from the dorsum of the foot. The joint was then opened, the lateral ligaments of the ankle-joint divided, the foot dislocated so as to show the astragalo-calcanean ligaments, and allow them to be divided. The bones were then grasped with the lion-forceps and pulled forwards, while the posterior surface of the astragalus was very cautiously cleaned, so as to avoid the posterior tibial artery.[77]
Excision of Metatarso-Phalangeal Joint of Great Toe.—Butcher performs it by splitting up the sinuses leading to the carious joint, exposing it and cutting off with bone-pliers the anterior third of the metatarsal bone, and the proximal end of the first phalanx. He also cuts subcutaneously the extensor tendons to prevent them from cocking up the toe.[78] Pancoast prefers a semilunar incision. A lateral incision is usually to be preferred.