AMPUTATION IN THE HAND
Amputations in the hand are almost always traumatic in origin; only rarely is amputation required to treat gangrene, infection, or tumor. Traumatic injuries to the hand are quite common, particularly in persons who use power tools in the workplace or the home. The general principles of amputation apply to procedures in the hand, and preservation of length is especially critical. Every effort should be made to salvage as much of each digit as possible.
The most important digit is the thumb, and it is absolutely essential to try to preserve both its length and function after injury. Often, severe injury or amputation of one of the other four fingers is best treated with primary amputation, because the remaining fingers can readily assume most functions. If the other digits are healthy, then prolonged or repeated attempts to reimplant a single finger or restore function to a finger (as distinguished from the thumb) may be time consuming, costly, and frustrating for the patient. Immediate amputation, combined with an aggressive and immediate rehabilitation program, may often be best for the patient. When multiple fingers are injured, however, the decision to amputate any injured finger must be considered very carefully.
After injury to the hand, amputation should be considered only when three or more of the five tissue areas (skin, tendon, nerve, bone, and joint) require special procedures for salvage. Age is also a factor in the decision to amputate. Amputation is rarely indicated in a child, even after a severe injury. In patients older than 50 years of age, however, removal of a single finger, except the thumb, is often the preferred option, particularly when both the digital nerves and the flexor tendons have been transected.
Amputation Of Fingertip
With fingertip amputations, it is also important to preserve as much length as possible. The primary factor influencing the ability to preserve length is the integrity of the volar skin. In fingertip injuries, the volar skin should be preserved, if possible, for use as a flap; this area comprises the best tissue for digital function. If the volar skin has been amputated or destroyed, the finger must be shortened to ensure that the volar surface of the residual digit is covered with full-thickness, sensate skin that will be durable and functional. The digital nerves should be assessed carefully. Each nerve should be transected under gentle traction and allowed to retract deep into the soft tissues to avoid painful neuromas at the end of the finger. The end of the bone should be contoured to eliminate bony prominences and a club-shaped stump. The flap should cover the end of the stump securely, but a redundant skin flap should be avoided. Excessive tension on the skin edges must also be avoided to prevent further necrosis of the skin flaps. It is not advisable to trim corners significantly because scar contraction and stump molding in therapy will provide adequate contouring.
When the very tip of the finger has been amputated, the roughened end of the distal phalanx should be smoothed and any protruding bony spikes removed. The volar skin can be mobilized distally by careful dissection along deep tissue planes just superficial to the flexor tendon sheath. The flap is brought up to and sutured to the fingernail, allowing wound closure and the resultant scar to be positioned on the dorsal aspect of the finger, away from the area that will be exposed to repetitive trauma.
When it is essential to preserve length, larger defects that cannot be closed primarily are treated with a thick split-thickness skin graft. The amputation bed is debrided of all necrotic and potentially infected tissue. A thick split-thickness skin graft can be harvested from the volar aspect of the forearm or the medial aspect of the arm just below the axilla. The donor site is closed primarily and the free graft sutured securely over the raw amputation stump. Thin split-thickness skin grafts should be avoided because they are not durable and will break down with repeated use, necessitating later revision of the amputation to a higher level.
Amputation Of Distal Phalanx
If the injury damages the distal phalanx-particularly when the damage extends into the nail matrix-the nail will probably be irregular and painful when it grows back. Therefore, in traumatic amputations through the distal phalanx that involve most of the fingernail, the entire nail matrix should be removed. Because the nail matrix extends considerably proximal to the skin fold, extensive dissection may be necessary to remove it completely. The distal portion of the phalanx should be removed as well, but the insertions of the extensor and flexor tendons on the most proximal portion of the distal phalanx should be left intact. The entire nail matrix is identified and sharply excised, and the periosteum overlying the distal phalanx is resected to avoid creating a bone spur. As in fingertip amputations, a volar skin flap is created and the wound closure positioned dorsally. Enough skin should be left to allow closure without tension but also without redundant tissue.
Amputation Through Middle Phalanx
A crushing injury that destroys the distal phalanx and a portion of the middle phalanx necessitates amputation through the middle phalanx. If the insertion of the flexor digitorum superficialis into the base of the middle phalanx can be preserved, some function of the proximal interphalangeal joint may be preserved as well. If the insertion of the tendon has been avulsed, it can be repaired with a grasping stitch in each slip and then sutured to the bone stump through a drill hole. If the sublimis cannot be repaired, there is little reason to preserve the middle phalanx, and disarticulation through the proximal interphalangeal joint should be considered. The nerves are carefully transected under tension and allowed to retract into the soft tissues. Bony spikes are removed, and the bone ends are smoothed to maximize function of the amputation stump. At this level, circulation to the residual skin flaps is usually quite good, and if there is any chance of preserving some function of the proximal interphalangeal joint, irregularly shaped flaps may be used to cover the stump to preserve length.
Amputation Of Finger And Ray
Occasionally, an entire finger must be amputated because of severe injury, aggressive infection, or malignant tumor. Generally, the distal half of the respective metacarpal is resected as well-a procedure called a ray amputation. When the finger is amputated at the metacarpophalangeal level, leaving the metacarpal intact, a prominent stump persists in the palm. When the patient makes a fist, a hole is created through which objects can fall. The residual metacarpal is a significant problem following injuries of the index finger. If the index meta- carpal is left in place, opposition of the thumb to the remaining long finger is difficult. Removal of most of the index metacarpal allows the thumb to lie closer to the middle finger, improving grip and overall function of the hand. Thus, when amputation is necessary at the metacarpophalangeal level, ray resection is often the treatment of choice. Central (long, ring) ray resection is accompanied by reconstruction of the intermetacarpal ligaments and bringing together the adjacent metacarpal heads to close the gap between the remaining fingers.
Deepening Of Thenar Web Cleft
The most important digit of the hand is the thumb, and all efforts should be made to preserve it and as much of its length as possible. Sometimes, it is even preferable to leave an insensate, motionless stump if the only alter- native is complete amputation of the thumb. When all the fingers have been amputated, gross gripping and prehension can be restored to some degree by deepening the thenar web space. Deepening of the web space between the thumb and index metacarpals is accomplished by resecting a portion of the adductor pollicis muscle and the thenar half of the first dorsal inter-osseous muscle. A Z-plasty technique is used, and the skin is incised to provide access to the muscles for resection. Then, closure of the Z-plasty flaps creates a cleft in the web space. The residual adductor muscle is used to power the thumb metacarpal for gross prehension.