Notes.—(1.) If commenced further forward, as in Pirogoff's modification, it will be found difficult to turn the corner of the heel; if further back, the nutrition of the flap is endangered.
(2.) This is very important. In several well-known text-books, even in the last edition of Gross's Surgery, the incision is figured passing obliquely forwards. This is a fatal error, for besides making a flap far too long, it forces the operator to cut fairly into the hollow of the sole, quite off the prominence of the os calcis, and he finds that it is utterly impossible to free his flap without using great force, and inevitably scoring it in all directions. Sloughing is almost inevitably the result.
(3.) The incision is to stop at least half-an-inch below the internal malleolus. Most surgical manuals, even when they profess to describe Mr. Syme's own method of operating, say that the incision should extend from malleolus to malleolus. If this is done, the flap becomes unsymmetrical, too long, and also the posterior tibial artery, on which much of the vascular supply of the flap depends, is cut. When the incision is properly made, the vessel is not cut till after its division into the plantar arteries.
(4.) Scoring the flap. Some may ask, Why do you object to a little scoring, the tissues are thick enough, and besides, don't you advise a slit in the flap yourself? Yes. One look at an injected preparation will show that the vessels supplying this thick flap come to it from its inner surface, and are inevitably cut across in any scoring of it, and also, that scoring cuts across the vessels, and must divide dozens of them; the slit we make is parallel with their course, and may not divide one.
(5.) Across the instep. Some authors recommend a semilunar anterior flap; this is quite unnecessary, increases bagging and delays union. It can be required only in cases where the heel flap has been destroyed or lessened by disease, or by operators in whose hands the heel flaps occasionally slough.
(6.) It is not impossible that a careless operator may (by cutting a little too low) miss the joint and get into the hollow of the neck of the astragalus, where he may cut away for a long time without making much progress.
Advantages.—1. It is wonderfully free of danger to life. It is very hard to obtain exact statistical information, but my experience is that the mortality is certainly not more than about 10 per cent., a very remarkable result when compared with that of amputations through the leg, the operation which used to be required for those cases which now require only amputation at the ankle-joint.
In the Statistical Report by the Surgeon-General of the United States, 9705 cases of amputation resulted in death, the proportions being as follows:—
| Amputation of | hip, | 85 | per cent. died. |
| " | thigh, | 64 | " |
| " | knee, | 55 | " |
| " | leg, | 26 | " |
| Amputation of | ankle-joint, | 13 | per cent. died. |
| " | shoulder, | 39 | " |
| " | arm, | 21 | " |
| " | fore-arm, | 16 | " |