1. Circular Method.
—The simple circular method is the simplest and easiest of all. It may be so performed as to furnish a solid musculotegumentary division, or skin cuffs may be made, which being turned up, permit a further circular division of the muscles and other tissues directly down to the bone. The former is preferable when possible. With an ordinarily long amputating knife the skin, down to and including the superficial fascia, is divided by one clean circular incision, made in one stroke; then by further circular cuts the muscles are divided in sections, the outer group being allowed to retract and expose the deeper layers, which are then divided at a higher plane. In this way the periosteum is reached. If sufficient time be afforded it may be circularly divided at the level of the last incision through the muscles, and then separated with a strong elevator or, as done by Kocher, with a chisel, in order that some portion of the exterior of the bone be raised with it. In this way a cuff of periosteum, or enough of it to cover the bone end, is detached upward, to the level where the bone itself is finally divided. The bone division is done with the ordinary amputating saw, or with the wire or chain saw.
The skin-cuff (Manchette) method differs in that the exterior flap is made wholly of skin, which is dissected as a cuff nearly up to the level of bone section, at which point the muscles are divided directly down to the bone. In this method the skin, fat, and superficial fascia should be raised together, and at no points separated from each other.
Modification of the cuff method, by which it is more easy to evert the circular flap, is made by one or two vertical incisions, by which the cuff is split some distance on one or both sides, thus transforming the cuff proper into two nearly square skin flaps. At other times the first method may be similarly modified, in which case we have to deal with two square flaps, including not only the skin, but all the tissues down to the bone.
Neudörfer still further modified the circular method for certain purposes by first making an incision along the outer or least vascular part of the limb, carrying the knife directly down to the bone, retracting the wound edges, and thus exposing the bone, which is then divided with a chain or Gigli saw. After the bone is divided the soft coverings are lifted to a sufficient distance below the saw line to ensure ample covering, then divided as above. The method is a slow one and is especially serviceable for amputation of the thigh, at its middle, for diabetic or senile gangrene, where it is so desirable to protect vascular supply from injury ([Fig. 677]).
The so-called elliptical method is practically a circular incision carried obliquely around the limb, the upper and lower ends of the ellipse being indicated by previous small incisions at the proper height. The skin and superficial fascia are retracted from the lower portion of the ellipse by turning them up to the level of the highest point, at which level the muscles are divided transversely by a plain circular incision. A modification of this method is the so-called ovoid or racket, which is simply an oval division with a pointed end, the margins of the flap being united in the long axis of the bone. This method is frequently applied in amputation of the fingers. (See [Fig. 683].)
2. Flap Methods.
—Flaps are either cutaneous or musculocutaneous. In every case the skin surface must be larger than the muscular. They are objectionable in that the skin flap is apt to slough, although least so about joints. The flap method is advantageous in that one flap may usually be made much longer than the other, and the longer one so doubled over at its end as to place the scar out of harm’s way. In certain injuries where the skin is much more injured on one side of the limb than on the other the operator is compelled to resort to flaps, unless he divide the limb much higher than might otherwise be demanded. Double flaps may be anteroposterior or lateral. A double flap practically results from a circular incision, carried through to the bone, with lateral division on either side, while a double flap with one long member may be similarly furnished by an oblique circular incision with the lateral prolongations.
Fig. 677
