The following amputation by external flap has been described (so far as I can discover, for the first time) by Dr. Dubrueil, in his work on operative Surgery:[26]—"Commencing just below the level of the articulation, while the hand is pronated, the surgeon makes a convex incision, beginning at the junction of the outer and middle thirds of the arm behind, reaching at its summit the middle of the dorsal surface of the first metacarpal, and terminating in front just below the palmar surface of the joint, again at the junction of the outer and middle thirds of the breadth of the arm. This flap being raised, the wrist is disarticulated, beginning at the radial side. A circular incision finishes the cutting of the skin." (Figs. iii. and iv.)
Amputation through the Fore-arm.—The method of operating must, in the fore-arm, depend a good deal upon the part of the arm where you require to amputate, the muscularity of the limb, and the condition of the skin and subcutaneous cellular tissue.
It must be remembered that a section of the fore-arm involves two bones, not, like the tibia and fibula, on a constant permanent relation in position to each other, but which rotate one upon another to an amount which varies with the part of the limb divided, and which rotation is a very important element in the future usefulness of the stump; again, that two sets of muscles occupy, one the back, the other the front of the limb, that these two are unequal in size, and that the outer sides or rather edges of each bone are subcutaneous; again, that these sets of muscles are comparatively fleshy in the upper two-thirds of the limb, and almost entirely tendinous in the lower third.
Remembering these points, we find that certain things require our attention, and certain difficulties are present in amputation of the fore-arm, from which amputation of the arm, with its single bone and copious muscular covering on all sides, is completely free.
Thus our flaps in the fore-arm must be antero-posterior; lateral flaps are an impossibility. Great care is requisite to cut them at all equal, from the inequality of the muscles on the two sides. In the lower third we cannot obtain available muscular flaps. Lastly, care must be taken lest, from the ever-varying relations of the two bones to each other in the varying positions of the limb, the surgeon mistake their position and pass his knife between them.
The next question that arises is, Where are we to operate? In cases where we have a choice, is there here, as in the leg, any "point of election"? No. As a rule in the fore-arm, the surgeon should endeavour to save as much as possible; especially when nearing the middle of the fore-arm, he should try to save the insertion of the pronator teres, so important in its function of pronating the radius.
Amputation in Lower Third of the Fore-arm.—By two flaps. These antero-posterior flaps must consist of skin only, as the tendons are only in the way, and thus should be made by dissection from without.[28] Making the dorsal one first, the surgeon should enter his knife at the palmar edge of the bone that is further from him, and cut a semilunar flap of skin only, finishing the incision quite on the palmar edge of the inner bone. The two ends of this incision must then be united by a similar semilunar flap of skin on the palmar side. The two flaps having been dissected back, he then clears the bones by a circular incision through tendons and muscles, not forgetting to pass the knife between the bones, and retracting all the soft parts, saws through the bones, at least half or probably three-quarters of an inch higher up. It is generally easiest to saw through both bones at once.
Long Dorsal Flap.—Where it is possible from laxity of the soft parts and the wrist not being much destroyed, to get a long flap from the back of the arm after Mr. Teale's method, a very good stump will result. This rule is, "In tracing the long flap a longitudinal line is drawn over the radius, so as to leave the radial vessels for the short flap ([Plate II.] fig. 1). At a distance equal to half the circumference of the limb, another line parallel to the former is drawn along the ulna. These are then joined at their lower ends, across the dorsal aspect of the wrist or fore-arm, by a transverse line equal in length to half the circumference of the fore-arm. The short flap is marked by a transverse line on the palmar aspect, uniting the long ones at their upper fourth.
"The operator, in forming the long flap, makes the two longitudinal incisions merely through the integuments, but the transverse one is carried directly down to the bones. In dissecting the long flap from below upwards, the tissues of which it is composed must be separated close to the periosteum and interosseous membrane. The short flap is made by a transverse incision through all the structures down to the bones, care being taken to separate the parts upwards close to the periosteum and membrane." The stump must be placed in the prone position, "to allow the long dorsal flap to be the superior when the patient is recumbent, and thus fall over the ends of the bones."[29]
The principal objection to the long dorsal rectangular flap (which makes an excellent covering) is, that unless it can be obtained from over the wrist-joint it requires the bones to be sawn so very high up. This may be avoided, to some extent, by making it shorter and rounded off, as in Carden's Amputation, q.v.