Digital Amputations of the Upper Extremity

Trauma

Amputations can result from traumatic injury from multiple mechanisms. The mechanism of injury is vital to consider in managing an amputation, in that crush injuries, sharp lacerations, high-energy twisting, and avulsion injuries all create a spectrum of injury to the soft tissue. Exposure to contamination, including industrial machines and environmental contamination (eg, barnyard, aquatic), to electricity, or to temperature extremes is also important to consider. ^{[2, 3]}

One of the main goals in managing mangled digits with associated fractures and nerve or vascular injuries is to optimize function of the hand. In some clinical scenarios, the patient may have better future function with amputation than with reconstruction because of the degree of damage to the amputated segment. In the setting of amputation, many have as their goal an “acceptable hand,” understood as one with near-normal length, near-normal sensation, and a functioning thumb. ^[4]  However, each patient may have additional personal goals for hand function that are important to consider on an individual basis.  

Infection

An important specific clinical presentation to recognize is the potential for devasting consequences after human bite wounds to the hand. Often, these are deeply penetrating injuries, especially the tooth-knuckle injury, where a small wound belies a deep wound with intra-articular extension and an associated high risk of serious complications (eg, tenosynovitis, septic arthritis, osteomyelitis, and severe stiffness). Amputation may be required in as many as 18.0% of these injuries. ^[5]

Hand infection in diabetics is another limb-threatening condition that is both underappreciated and challenging to treat. Inadequate treatment can result in long-term disability, contracture, amputation, and even death. Most cases begin as a neglected minor wound that then progresses rapidly.

Digital amputation is common in the setting of diabetic finger infection because such infection, once established, can be difficult if not impossible to eradicate. Osteomyelitis, ipsilateral upper-extremity dialysis fistula, end-stage renal disease, and vascular disease each have significant independent predictive value for amputation rather than digital preservation. Amputation may be limb- and life-saving. ^{[6, 7]}  Machine learning models are being developed that may eventually prove superior to traditional models or clinical judgment in predicting the need for amputation; further research is needed. ^[8]

Vascular conditions

Raynaud phenomenon is episodic vasospasm of the peripheral vessels causing color changes in the digits, often with associated pain and paresthesias. It can occur in response to cold or stress. Raynaud phenomenon may be either primary (idiopathic) or secondary to connective-tissue diseases (eg, systemic sclerosis), extrinsic vascular obstruction (as in thoracic outlet syndrome), medications, chemicals (eg, ergotamine and vinyl chloride), vibration exposure, and hematologic hyperviscosity states.

In cases of secondary Raynaud phenomenon, there can often be ischemia of the fingers (and toes) leading to ulceration. This may progress to gangrene necessitating amputation when other treatment options to manage the vasospasm have failed. In such cases, amputation may be highly effective for pain relief. ^{[9, 10]}

Hemodialysis is a common risk factor for ischemia of the upper extremity, and amputation is a common sequela. Studies have shown that at present, the best management of dialysis-associated steal syndrome is distal revascularization with interval ligation, which involves ligating an artery distal to the fistula and subsequently forming a bypass. ^[11]

Finger ischemia in hospitalized patients can occur in many contexts, including in association with the presence of arterial lines and the use of vasopressor medications (eg, phenylephrine and norepinephrine). Despite appropriate treatment with anticoagulant or antiplatelet agents, progression to amputation can occur. Frequently associated conditions include mechanical ventilation (37%), diabetes (34%), peripheral arterial disease (32%), dialysis dependence (31%), cancer (24%), and sepsis (20%). As many as 5% of these patients with finger ischemia ultimately require finger amputation. ^[12]

Additional clinical situations that may be managed with elective amputations include tumor extirpation, vascular insufficiency, infection, and congenital malformation.

Amputation in the upper extremity is contraindicated when the patient's outcome can be improved with limb salvage.

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 has 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 has only two. To avoid confusion, each digit is referred to by name (thumb, index finger, long or middle finger, ring finger, and small or little finger) rather than by number.

Important anatomy to consider in performing digital amputations includes 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 so as to optimize resulting function. The flexor tendons are located on the volar aspect of the finger, and the extensor tendons are located dorsally. Each joint is stabilized by the radial and ulnar collateral ligaments, with secondary support from the volar plate and dorsal capsule. The digital neurovascular bundles are on the radial and ulnar borders of the digit between the Grayson and Cleland ligaments.

For more information about the relevant anatomy, see Hand Anatomy.

Charpentier et al retrospectively evaluated long-term quality of life and functional outcome in 28 patients who underwent digital replantation after amputation (minimum follow-up, 2 y; mean, 4.6). ^[13]  Total active range of motion (ROM), grip, and pinch strength were assessed; functional outcomes were evaluated; and occupational status and daily activities were reported. Mean total active ROM was 42% of the contralateral healthy side. Mean grip and pinch strength were 80% and 65%, respectively. Fusion did not significantly influence active mobility. Of the 28 patients, 77% returned to the same job, and 75% experienced cold intolerance.

Lafosse et al retrospectively studied surgical outcomes in 13 very young children (mean age, 2.9 y; range, 1.1-5.7) who underwent finger replantation (15 fingers) after traumatic amputation. ^[14]  The authors evaluated everyday life activities, pain and cold tolerance, total active ROM in patients with successful replantation, and growth disturbance. The overall success rate was 47%, with a 67% rate of major complications. Venous ischemia developed in 86%. After surgery, the hemoglobin level decreased by more than 2 g/dL in six patients, and blood transfusion was necessary in two. At the last follow-up, patients with successful replantation had a mean total active ROM of 72%.

Shaterian et al performed a quantitative review and meta-analysis of 36 studies with the aim of identifying predictors of digit survival following replantation. ^[15]  Factors found to influence replant survival included number of venous anastomoses (zero vs one vs two), number of arterial anastomoses (zero vs one vs two), and mechanism of injury (sharp cut vs blunt cut vs avulsion vs crush). Factors not found to be significantly associated with survival included age, sex, zone of injury, digit number, tobacco use, ischemia time, method of preservation, and use of vein graft.

A retrospective study by Nakanishi et al assessed the clinical outcomes of reposition flap transfer for reconstructing an amputated fingertip when replantation is not possible. ^[16]  The passive extension angle of the IP/PIP joint was reduced by an average of 19°, and the time to complete wound healing averaged 28 days (range, 18-41); the reduction in passive extension angle was significantly correlated with the wound healing period. Absorption of the grafted bone was observed in three cases. All of the patients were either highly satisfied or fairly satisfied with the results.

A retrospective study by Kuwahara et al compared the clinical and esthetic outcomes of a digital artery flap (DAF) with nail-bed graft with those of replantation for fingertip amputation. ^[17]  Although the esthetic appearance achieved by DAF was inferior, this approach was found to be equivalent to replantation with respect to postoperative functional outcomes and to be associated with a shorter operating time and a reduced duration of hospitalization.