Digital Amputations of the Upper Extremity Technique

In performing digital amputations, it is important to provide a mobile, stable, painless stump with the least interference from the remaining tendon and joint function so as to ensure the most useful result. The remaining viable skin is conserved because it may be needed to provide durable soft-tissue coverage for the amputation stump. When possible, volar skin should be used for the stump coverage because it provides skin that is thicker and more sensate than dorsal skin. ^[20]

There are several local options for tissue rearrangement of volar skin over the amputation stump, including the following ^{[21, 22]} :

• Fillet flaps
• Volar V-Y flaps
• Bilateral V-Y flaps
• Homodigital island flaps

In the acute traumatic amputation, "dog ears" often should be left to eliminate tension and to prevent compromising the blood flow to the remaining flaps achieving closure; these dog ears disappear over time. If the wound is small, it can be allowed to heal spontaneously by contraction and epithelialization. Wounds smaller than 1 cm can heal spontaneously within a reasonable time. Larger wounds may require a skin graft to heal quicker. ^[23] Split-thickness grafts can be used for the benefit of wound contraction to result in a smaller area on the tip, which is not normal pulp. ^[24]

Regarding the treatment of the bone in a digital amputation, the bone under the stump end must be smooth. Remaining bone chips and devitalized bone should be removed. The bone at the stump end can be smoothed by using a rongeur and a file. Bone length is not as important as a stump with mobile nonsensitive coverage. The bone of the distal phalanx must be of adequate length to support the nail bed and nail growth. ^{[25, 26, 27, 28]} With digital amputations involving the thumb, length is important for the function of the thumb.

The articular cartilage can be preserved when the amputation occurs at the level of the interphalangeal (IP) joint. This articular cartilage can provide a shock pad for trauma and potentially causes less pain under the skin than the bone edges. Whitaker et al clinically evaluated the preservation of the articular cartilage with digital amputations and found a better outcome when the cartilage was left on the stump end. ^[29] The protruding condyles and the anterior aspect of the phalanx may be trimmed to provide a less bulbous stump.

In addressing the nerve at the stump end, it is important to avoid neuroma formation in this location. The nerve end should be in a position away from the stump end or an anticipated point of contact pressure. To minimize the risk of neuroma formation at the stump end, traction neurectomy of the digital nerve should be performed bilaterally for each digital amputation. The nerve is longitudinally distracted in the distal direction and then transected to allow proximal retraction, with the nerve end left 1-1.5 cm from the fingertip.

Preservation of a tendon insertion improves the active mobility and function of an amputation stump. Therefore, when possible, tendon insertions should be preserved. However, the amputation level is often proximal to the tendon insertion. The flexor digitorum profundus (FDP) tendon should never be sutured over the bone end or to the extensor, because this can result in the quadriga effect. This effect reduces excursion of the adjacent normal fingers because of the common profundus muscle from which all the profundus tendons originate. The amputated finger, which has a tighter or shorter profundus tendon, reaches maximal excursion before the other fingers do and results in a weaker grip.

Another complication of tendon imbalance is the lumbrical plus posture, which is the paradoxic extension of the involved finger's proximal IP (PIP) joint with attempted flexion. This occurs when the profundus tendon is allowed to retract proximally, resulting in a pull on the lumbrical muscle as it originates from the profundus.

The lumbricals contribute to metacarpophalangeal (MCP) joint flexion and IP joint extension. This proximal pulling of the profundus pulls the lumbrical tighter to extend the IP joints paradoxically with attempted flexion. ^[30] However, lumbrical plus posture after amputations of the distal IP (DIP) joint is rare. Also, adhesions can result; therefore, early motion of the amputated finger is recommended.

The digital arteries should be identified and ligated with small-caliber sutures or should be cauterized. The visible veins can be cauterized as well. Then, the skin is loosely approximated to make sure there is no tension on the skin edges. If there is tension on the skin, the bone may be shortened or local flaps can be used.

Distal phalanx

When amputations are at the level of the distal phalanx, preservation of the profundus insertion is critical. An intact profundus improves functional contribution of the amputated finger and improves grip strength by providing active flexion at the DIP joints in conjunction with the other fingers. Preservation of enough bone to support normal nail growth is perhaps the most crucial predictor of functional length with amputations at this level.

Kiuchi et al studied survival (complete, partial, or none) for composite grafts in distal digital amputations with regard to injury type (clean-cut, blunt-cut, or crush-avulsion) and amputation level (Ishikawa subzones I-IV). ^[31]  They found that all injuries in subzone I and clean-cut injuries in subzone II were candidates for composite grafting, that blunt-cut and crush-avulsion injuries in subzone II were marginal candidates for this approach, and that composite grafting was contraindicated for all subzone III or IV injuries.

Murphy et al, in a retrospective review of 96 pediatric patients who underwent composite grafting of fingertip injuries after distal digital amputation, evaluated graft viability (no take, partial take, or complete take) with regard to injury type, amputation level, and time to surgery. ^[32] In all, 31 patients had no graft take (32%), 50 had partial take (52%) and 15 had complete take (16%). Secondary revision was performed in two patients (2%). Neither time to surgery nor level of amputation had a statistically significant influence on outcome.

Idone et al described the use of a homodigital fenestrated adipofascial reverse (FAR) flap for reconstruction of the amputated fingertip in five patients with amputations distal to the nail matrix. ^[33] Results were evaluated by determining the two-point discrimination (2PD) value and assessing range of motion (ROM) in the DIP joint. Complete survival was achieved in all flaps. At 1 year, the mean static 2PD value for reconstructed fingers was 4.2 mm (range, 3-5 mm), mean ROM for the DIP joint was 78º, and the mean Vancouver Scar Scale (VSS) score was 0.6 (range, 0-2). No complications were reported.

Distal interphalangeal joint

Amputations at the level of the DIP joint can be closed over the denuded articular surface of the middle phalanx. Local flaps can be used to provide soft tissue for closure over the middle phalanx, if needed. The volar V-Y flap is the standard local flap option for injuries at this level. The volar V-Y flap is fashioned with the apex of the V at the PIP crease.

Middle phalanx

When amputations are through the middle phalanx, preservation of the flexor digitorum superficialis (FDS) insertion, which inserts on the middle third of the middle phalanx, is desirable. Amputations proximal to the FDS insertion leave the amputated finger without active motion control at the PIP joint level and only with active motion at the MCP joint level.

Proximal interphalangeal joint

Amputations at the PIP joint can be closed over the articular surface of the proximal phalanx, as can those at the DIP. Amputations at this level can still actively flex at the MCP joint through the action of the intrinsic muscles.

Near metacarpophalangeal joint

If the amputation is near the MCP joint, especially in the long and ring fingers, dropping small objects because of the defect can be addressed with a finger prosthesis or ray amputation, with or without transposition.

Index-finger ray amputations

The use of a finger to pinch with the thumb is vital to the use of the hand. In a noninjured hand, the index finger is the primary digit used with the thumb for the pinch function. If length, sensation, and mobility of the index finger are inadequate, the patient may adapt by bypassing the index finger and preferentially using the middle finger for pinch. In this circumstance, a stiff residual index digit can impede pinch and worsen overall function of the hand. This is the primary indication for a ray amputation of the index finger.

The level of amputation that makes the index finger a candidate for a ray amputation is controversial. A ray amputation of the index finger should not be performed acutely for injuries distal to the MCP joint unless the spare parts are needed for salvage of other digits (eg, the thumb). The remaining index finger may be left during a trial period after the initial injury. If the residual finger impedes function, it can be electively converted to a ray amputation; however, such a conversion can narrow the palm and result in a loss of grip strength and pronation strength, justifying a trial with the shorter residual finger for laborers.

Murray et al found that power grip, key pinch, and supination strength are diminished by approximately 20% of normal with index ray amputations. ^[34] Pronation strength is diminished by 50% in the same group of patients. The cosmetic appearance of an index ray amputation is highly acceptable.

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 a deficiency that could result in a web-space contracture. (See the image below.)

The dorsal veins are ligated, and the extensor tendons are transected. The periosteum is scored, and the metacarpal base is transected. The dorsal interosseous and lumbrical muscle tendons are transected. Studies have shown no difference in pinch strength with dorsal interosseous transfer to the second dorsal interosseous muscle; therefore, this technique is not indicated. ^[34] Then, the flexor tendons are divided. The digital arteries and nerves are divided distal to the branches to the palmar skin.

Interrupted sutures are used for skin closure. The hand is dressed lightly to allow for early motion.

Middle- and ring-finger (central) ray amputations

When the middle and ring fingers are amputated at a level near the MCP level, a gap is created between the remaining fingers. Patients describe difficulty in retrieving change from their pockets as small objects become difficult to grasp. This can be corrected with a ray amputation. However, the loss in grip strength and pronation strength must be considered before ray amputations are performed for these central digits.

The principles of a central ray amputation include the following:

• Removal of the injured finger at the metacarpal base
• Correcting the rotational deformity
• Closing the space between the two adjacent unamputated fingers
• Achieving a satisfactory appearance of the hand

Two techniques of central ray amputation have been described. One is the ray transfer procedure, in which the index finger ray is transferred onto the third metacarpal base for the middle finger, and the small finger is transferred to the ring metacarpal base (see the first image below). The other involves removing the involved finger at the metacarpal base (see the second image below). The disadvantages of the ray transfer procedure are the requirement for postoperative immobilization and the risk of nonunion. Therefore, the authors' preferred technique for central ray amputation does not involve ray transfer.

The technique of central ray amputation involves the use of a circumferential incision at the midproximal phalanx in conjunction with a dorsal longitudinal incision (see the images below). The dorsal incision is extended through the extensor. The periosteum is scored at the level of the metacarpal base. The metacarpal is transected at its base. Then, the hand is supinated, and the flexor is divided. The neurovascular bundles are divided proximally to avoid neuroma formation at the skin incision. The deep transverse metacarpal ligaments are identified on either side of the volar plate of the involved finger at the MCP joint.

In transecting the deep transverse metacarpal ligaments, it is essential to preserve enough to allow attachment of the ligaments to each other so as to minimize gap formation and rotational deformity. Then, the ray is amputated. 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. The deep transverse metacarpal ligaments are then repaired with 2-0 Ethibond nonabsorbable sutures. The threaded K-wire can help prevent rotational deformity. Active motion is begun early, and the K-wires can be removed at 6 weeks.

This technique can be applied to ray amputation of both the middle and the ring finger (see the image below). Incomplete closure of the defect and scissoring must be carefully avoided with this technique.

In a retrospective study that included nine patients (six male, three female; mean age at surgery, 30.2 ± 12.2 y) with mutilating ring finger injuries, Monreal evaluated the functional and aesthetic results of delayed fourth-ray amputation with fifth-ray transposition (after 14 days of injury). ^[35] All patients were followed for a mean period of 17.1 ± 4.1 months (range, 12-24). The author found fourth-ray resection with transposition of the small finger with a wedge-shaped hamate-capitate arthrodesis secured by screw fixation to be technically easier than metacarpal osteotomy/transposition and less liable to postoperative complications, suggesting that this approach restores hand function and cosmetics.

Small-finger ray amputations

The small (little) finger plays a role in gripping and hooking objects. Small-finger injuries are the most difficult to rehabilitate, and the finger often becomes stiff and immobile, possibly hindering hand function by catching on pockets or other objects. In this circumstance, small-finger amputation can be considered. In a laborer, the amputation can be performed at the MCP joint to remove the flail segment of the proximal phalanx but preserve a broad palm.

If grip strength is not a concern, a more aesthetically satisfactory appearance can be obtained with a small-finger ray amputation. In performing a small-finger ray amputation, it is important to preserve the insertion of the extensor carpi ulnaris (ECU), which inserts on the base of the fifth metacarpal. ^[36] This procedure is performed through a tennis-racquet incision (see the image below). Moreover, the hypothenar muscles are preserved to cover the gap and provide padding to the ulnar side of the hand. ^[1]

The digit that is most critical for hand function is the thumb. Amputations of the thumb can be debilitating. The level of amputation determines the significance of the functional deficit. In general, the thumb is important as a post to which the fingers oppose. Therefore, in contradistinction to the length of the fingers, the length of the thumb is more important to hand function than active motion.

When the thumb tip has been amputated, replantation can provide the patient with the best return to function, even if IP 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 (see the images below). The volar advancement flap is raised as a rectangle to include both neurovascular bundles to the MCP crease of the thumb proximally, and then it is advanced in the distal direction.

The Moberg flap can be used to close 1- to 1.5-cm defects (see the first and second images below). If the amputation level is at or distal to the IP joint, the patient should not experience much functional loss. If the patient's amputation level is proximal to the IP joint, reconstruction with toe transfer or metacarpal lengthening and web-space deepening should be considered (see the third image below). If the amputation is at the carpometacarpal (CMC) level, pollicization can be considered if the index finger is not injured.

Transcarpal amputations

Transcarpal amputations are rare. Depending on injury mechanism, some amputations at this level can be replanted, and an acceptable return of function anticipated. When replantation is unsuccessful or cannot be performed, minimal reconstructive options exist for amputations through the carpus. In general, patients can be fitted with hand prostheses, which provide good cosmetic results. When the wrist supplies active motion, the prosthesis can be operated without an attachment to the elbow or shoulder harness.

Wrist disarticulations

Again, amputations at this level are uncommon and in some cases can be replanted. Historically, amputations at the below-elbow level have been favored over wrist disarticulations because of the difficulty in wrist prostheses. However, with advances in technology, amputations at this level can be considered. Wrist disarticulation level is preferable in children to preserve growth potential and avoid the overgrowth of bone ends that occurs in a forearm-level amputation.

The theoretical advantage of preserving the distal radioulnar joint (DRUJ) is that full active pronation and supination can improve the function of the amputated appendage. Therefore, when possible, the DRUJ should be preserved. Also, the radial styloid flare can be used to improve prosthetic suspension. If possible, the palmar skin should be used to cover the stump end to provide a thicker and more durable coverage.

Below-elbow amputations

In general, below-elbow amputations should be performed to preserve as much length as possible so as to preserve maximal pronation and supination. When traumatic amputations are more proximal, even 2 cm of ulnar bone length is sufficient to fit a below-elbow prosthesis. With more proximal forearm-level amputations, the biceps can be reattached to the ulna at a position that approximates the normal resting length of the muscle. Care must be taken to ensure that the biceps is not reattached under excess tension so as to minimize the risk of a resulting flexion contracture. A soft-tissue deficit may necessitate the use of a free flap or local flap to preserve the elbow. ^[37]

Krukenberg procedure

The Krukenberg procedure is mentioned mainly for historical purposes. This operation was first described by Krukenberg in 1917 and involves separating the ulna and radius for below-elbow amputations to provide a pincerlike grasp that is motored by the pronator teres. The indication for this operation is reserved for a blind person who is undergoing bilateral amputation because it can provide prehension and tactile gnosis.

Elbow disarticulations

Elbow disarticulations may be preferred in some clinical situations by surgeons and prosthetists to above-elbow amputations because they allow rotary force transmission over the humerus and because the epicondyles provide good support for the prosthesis. The disadvantage of an amputation at this level is that the prosthesis has outside locking hinges, which can damage clothing.

Above-elbow amputations

In traumatic above-elbow amputations, the decision for additional bone resection must be carefully planned because maintenance of the residual limb length is critical to function. Maintaining a longer humeral segment can provide better proximal muscular control and a long lever to help maneuver the prosthesis. In cases where shortening of the humeral segment would be required for primary closure, consideration can be given to soft-tissue reconstruction for maintaining length.

Split-thickness skin grafting can be considered over the residual limb end if there is adequate muscle for coverage of exposed bone, or additional reconstructive soft-tissue procedures may be considered if they can aid in maintaining limb length. In the case of a high transhumeral amputation, it is essential to have bone below the insertion of the pectoralis major. Amputations more proximal to the pectoralis functionally resemble shoulder disarticulations in that shoulder motion is lost.

Complications in the amputated residual disgit can be related to bone or to soft tissue. These include osteophyte formation and osteomyelitis. The risk for these bony complications can be minimized with appropriate bony debridement at the initial treatment.

Early postoperative complications include wound hematoma, infection, and additional tip necrosis. Hemostatic control of the amputation site can be managed initially with a tourniquet. Thorough irrigation and debridement of the amputation wounds with removal of all devitalized skin, tendon, and muscle are vital for minimizing the risk of postoperative infection. After hemostasis is achieved, closure that does not pull on or cause ischemia at the tissue edges is also crucial. 

Patients can experience symptoms of chronic pain in the amputated part. Phantom limb is the sensation of feeling in the amputated part, and it is common after amputations. Patients should be informed of this potential complication early in their treatment. The likelihood of developing phantom limb pain is highest after severely mutilating amputations, and it usually begins soon after the amputation. When patients are made aware of this potential symptom early, steps can be taken to manage this challenging clinical problem.

Pain in the distal aspect of the residual limb can be associated with the formation of a neuroma. ^[38] Sometimes, these neuromas cause persistent pain and must be surgically mangaged. Options for surgical treatment include excision, burying the distal end of the nerve into muscle, and coapting the distal nerve to another target in an effort to minimize local pain caused by the neuroma (see the images below). Interdigital direct neurorrhaphy is receiving increased attention as an option for treating painful neuromas developing after finger amputation. ^[39]

Patients can have cold intolerance and hypersensitivity at the residual digit tip. ^[40] Usually, this is a self-limited process that improves with time and in some cases with targeted therapy. Desensitization therapy may hasten the resolution of these symptoms, and a transcutaneous electrical nerve stimulation (TENS) unit may be helpful. Pharmacologic management with gabapentin may also be effective.

Contracture prevention is critical in the treatment of amputations. Local flap options for soft-tissue reconstruction that involve immobilization can result in contracture formation. Some local flap options utilize an adjacent digit as a donor site (as with crossfinger or thenar flaps) and thus run the risk of contracture in the recipient or donor fingers. In some cases, the shoulder, elbow, and wrist can also develop stiffness when a distal site is used as a donor (eg, with the groin flap). It is imperative to begin early motion when appropriate in order to minimize the risk of contracture formation.

Finger tendon imbalance after finger amputations can be associated with a weakened grasp. In some cases, where the FDP is sutured over the stump end, the patient can develop quadriga. When this occurs, the amputated finger has a shorter or tighter flexor tendon and reaches maximal excursion before the other fingers, which limits the ROM of the uninjured adjacent fingers.

In other cases, where the FDP tendon is allowed to retract proximally, the result can be a residual digit that has a lumbrical plus posture (paradoxic hyperextension of the IP joints with attempted digit flexion). When lumbrical plus posture develops, treatment can include releasing the lumbrical or radial lateral band in an effort to better balance the pull of the flexor and extensor tendons.