Background
An amputation is the removal of an extremity or appendage from the body. Amputations in the upper extremity can occur as a result of trauma, or they can be performed in the treatment of congenital or acquired conditions. Although successful replantation represents a technical triumph to the surgeon, the patient's best interests should direct the treatment of amputations.
The goals involved in the treatment of amputations of the upper extremity include the following [1, 2] :
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Preservation of functional length
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Durable coverage
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Preservation of useful sensibility
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Prevention of symptomatic neuromas
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Prevention of adjacent joint contractures
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Early return to work
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Early prosthetic fitting
These goals apply differently to different levels of amputation.
Treatment of amputations can be challenging and rewarding. It is imperative that the surgeon treat the patient with the ultimate goal of optimizing function and rehabilitation and not become absorbed in the enthusiasm of the technical challenge of the replantation, which could result in poorer outcome and greater financial cost due to lost wages, hospitalization, and therapy.
Indications
Amputations can result from traumatic injury involving a variety of machines, they can be self-inflicted, or they may be required after traumatic events, such as electrical burns or frostbite. In addition, elective amputations may be indicated for tumor extirpation, vascular insufficiency, infection, or congenital malformation.
Technical Considerations
Anatomy
The basic skeleton of the wrist and hand comprises a total of 27 bones. The hand is innervated by three nerves—the median, ulnar, and radial nerves—each of which has sensory and motor components. The muscles of the hand are divided into intrinsic and extrinsic groups.
The hand contains five metacarpal bones. Each metacarpal is characterized as having a base, a shaft, a neck, and a head. The first metacarpal bone (thumb) is the shortest and most mobile. It articulates proximally with the trapezium. The other four metacarpals articulate with the trapezoid, capitate, and hamate at the base. Each metacarpal head articulates distally with the proximal phalanges of each digit.
The hand contains 14 phalanges. Each digit contains three phalanges (proximal, middle, and distal), except for the thumb, which only has two phalanges. To avoid confusion, each digit is referred to by its name (thumb, index, long, ring, and small) rather than by number.
Important anatomy to understand in performing digital amputations includes the various structures of the digit, such as the digital nerves, the digital arteries, the flexor digitorum profundus (FDP), the flexor digitorum superficialis (FDS), the extensor tendons, the collateral ligaments, the volar plate, the dorsal capsule, and the components of the nail. When amputations are performed at various levels, it is important to understand the critical anatomy to optimizing resultant function.
For amputations at the distal interphalangeal (DIP) level, volarly the FDP is severed and allowed to retract proximally. The digital neurovascular bundles can be found on the radial and ulnar border of the distal digit at the DIP crease to be at the level of their trifurcation. These neurovascular bundles course between the Grayson and Cleland ligaments volarly and dorsally, respectively.
The digital nerves are longitudinally retracted and severed to allow retraction (so-called traction neurectomy) to prevent neuroma formation at the tip. The digital arteries are bipolar-coagulated to minimize bleeding. These neurovascular structures can be located longitudinally along this vector throughout the digit between the Grayson and Cleland ligaments. Each joint is stabilized by the radial and ulnar collateral ligaments, and the volar plate and dorsal capsule may require severing to detach the adjacent phalanx.
For more information about the relevant anatomy, see Hand Anatomy.
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In performing an index ray amputation, a dorsal longitudinal incision over the index metacarpal is used in conjunction with a circumferential skin incision at the midproximal phalangeal level. The skin is intentionally left long distally to avoid deficiency, which could result in a web-space contracture.
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The principles of a central ray amputation include removal of the injured finger at the metacarpal base, correcting the rotational deformity, closing the space between the 2 adjacent unamputated fingers, and achieving a satisfactory appearance of the hand.This illustration depicts 1 of 2 techniques that have been described regarding central ray amputation. The procedure involves the transfer of the index finger ray onto the third metacarpal base for the middle finger and the small finger to the ring metacarpal base. The disadvantages of the ray transfer procedure are the requirement for postoperative immobilization and the risk of nonunion.
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The second central ray amputation technique involves removing the involved finger at the metacarpal base. The disadvantages of this technique are eventual widening of the web space and rotational deformity of the digit. The risk of these complications can be minimized by repairing the deep transverse intermetacarpal ligament and using a threaded Kirschner wire (K-wire) to secure the second to the fourth metacarpal.
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The technique of central ray amputation involves the use of a circumferential incision at the midproximal phalanx in conjunction with a dorsal longitudinal incision. The dorsal incision is extended through the extensor. The periosteum is scored at the level of the metacarpal base.
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In performing a central ray amputation, the dorsal incision is performed in a tennis racket configuration.
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The volar incision is completed in the shape of a wedge to facilitate closure without a dog ear.
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The dorsal incision is extended through the extensor. The periosteum is scored at the level of the metacarpal base.
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With a central ray amputation, the metacarpal is transected at its base. The hand is then supinated and the flexor is divided.
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The flexor tendon is divided and allowed to retract proximally.
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The metacarpal base is transected with a sagittal saw.
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The amputated central ray is shown here.
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The proper digital nerves and arteries to the adjacent fingers are preserved from the common digital neurovascular bundles.
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The neurovascular bundles are divided proximally to avoid neuroma formation at the skin incision.
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The deep transverse metacarpal ligaments are identified on either side of the volar plate of the involved finger at the metacarpophalangeal joint. In transecting the deep transverse metacarpal ligaments, it is essential to preserve enough ligament to attach to each other to minimize gap formation and rotational deformity.
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The deep transverse metacarpal ligaments are repaired with 2-0 Ethibond nonabsorbable sutures.
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The gap is compressed, and transverse Kirschner wires (K-wires) are placed through the metacarpals on either side of the ray amputation. Threaded K-wires can help resist the sliding of the metacarpals on the K-wires like an accordion.
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The threaded Kirschner wire can help to prevent rotational deformity.
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Active motion is begun early, and the Kirschner wires can be removed at 6 weeks. This technique can be applied to ray amputation of both the middle and ring fingers.
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In performing a central ray amputation of the ring finger, the deep transverse intermetacarpal ligament can be repaired to avoid the need for metacarpal transfer.
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The procedure of small finger ray amputation is performed through a tennis racquet incision.
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When the thumb tip has been amputated, replantation can provide the patient with the best return to function even if interphalangeal joint fusion is required.In the event that replantation cannot be performed or is unsuccessful, minimal bone shortening should be performed to provide a smooth bone end over which to close the skin. In fact, the bone should not be removed only to obtain primary skin closure. A volar rectangular advancement flap (Moberg) should be used to provide soft-tissue closure and preserve thumb length.
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The volar advancement flap is raised as a rectangle to include both neurovascular bundles to the metacarpophalangeal crease of the thumb and is advanced in the distal direction.
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The Moberg flap can be used to close 1- to 1.5-cm defects. If the amputation level is at or distal to the distal interphalangeal joint, the patient should not experience much functional loss.
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The Moberg flap can allow for length preservation and coverage of the thumb tip with sensate skin because it contains both neurovascular bundles.
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If the patient's amputation level is proximal to the interphalangeal joint, reconstruction with toe transfer should be considered. If the amputation is at the carpometacarpal level, pollicization can be considered.
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This patient had a digital nerve neuroma (outlined in marker) following revision amputation. He had point tenderness over the neuroma. The skin and neuroma were removed.
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The neuroma is dissected, and a traction neurectomy is performed.
