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.
