Digital Amputation – Indications, Contraindication

In the traumatic setting, the primary objective of management is to salvage the amputated finger to restore function, especially if the dominant hand is affected. However, this is not always possible, as there are many factors to consider.  These factors include the time from injury, mechanism of injury, and degree of contamination [1]. In the elective setting, determinants for the level of amputation include various factors, such as oncological clearance, symptom relief, and function preservation; however, for the purpose of this paper, the primary focus will be on traumatic finger amputation.

Causes of Digital Amputation

In traumatic injuries, one should assess the patient in accordance with the Advanced Trauma Life Support approach (Airway, Breathing, Circulation, etc.) for a systematic assessment of the patient and to rule out any life-threatening injuries before referring or transferring patients for further specialist management of their finger injuries. Determining the mechanism of injury is crucial, as it could affect decisions regarding management and outcome for the patient.  Sharp injuries may provide a clear amputation level, whereas blunt trauma may correlate with crush injuries at the level of the amputation, and avulsion injuries can cause distant trauma away from the level of visible injury.

Pathophysiology

Typically, once a finger amputation has occurred, ischemic tolerance times are 12 hours if warm and up to 24 hours if cold. For more proximal amputations, these times are halved. The amputated part should be covered in a normal saline soaked gauze, sealed in a plastic bag and submerged in icy water with no direct contact with ice. If there is direct contact with ice, it could result in tissue damage and render the amputated part non-viable. More proximal amputations are less tolerant of ischemia? due to the presence of muscle tissue, which can undergo irreversible changes after 6 hours of ischemia.[rx][rx]

Diagnosis? of Digital Amputation

History

• Hand dominance, occupation, time of injury, mechanism of injury, other associated injuries, comorbidities and NPO status.

Physical Exam

• Level of amputation, structures involved, neurovascular status, function, and degree of contamination (if relevant).  It is vital to assess the amputated part and ultimately determine its suitability for replanting respective to the mechanism of injury (e.g., crush, guillotine-style, avulsion).

Finger amputations classification is generally according to the level of amputation.  The Sebastian and Chung classification is outlined below[rx]:

• Zone 1 distal amputations

  • Zone 1A – distal to lunula, through the sterile matrix
  • Zone 1B – between lunula and nailbed
• Zone 1 proximal amputations

  • Zone 1C – between flexor digitorum profundus insertion and neck of the middle phalanx
  • Zone 1D – between the neck of the middle phalanx and insertion of the flexor digitorum superficialis

Evaluation

Laboratory:(optional depending on clinical scenario)

• CBC (complete blood count) to assess for blood loss
• Coagulation studies (only if the patient is known to be on anticoagulants)

Imaging

• Plain radiograph of the affected finger/hand and amputated part; this allows assessment of bony injuries, bone quality and guide decisions regarding bony fixation methods. Angiograms are normally not requested unless it forms part of investigations for other injuries.

Treatment of Digital Amputation

Initial management – first aid, ATLS approach to the patient, preserve amputated part, tetanus vaccination, and antibiotics as per local hospital guidelines.

In the traumatic setting, the ideal candidate for replantation should be young, healthy, sharp mechanism of injury (giving a clear amputation level), minimal tissue destruction and contamination.[rx]

Indications for replantation

• Thumb amputation – loss of thumb represent approximately 40 to 50% loss of hand function
• Multiple finger amputations
• Amputations at or proximal to palm
• Pediatric patients with finger amputation(s) at any level
• Single finger amputation distal to insertion of the flexor digitorum superficialis (zone I) (studies have shown that replantation distal to this insertion point had better outcomes than those proximal)
• Patient consideration – specialist requirement, e.g., occupation or pre-morbid compromised hand function[rx][rx]

Contraindications and relative contraindications

• Single digit injury through flexor tendon? zone II[rx]
• Smoking
• Severe crush
• Mangled limb
• Heavy contamination
• Segmental injuries
• Prolonged warm ischaemic time
• Medically unfit
• Improperly preserved amputated part
• Avulsion injuries
• Other life-threatening injuries
• Mentally unstable
• Previous surgery to affected finger
• ‘Red line’ or ‘red ribbon’ sign (seen in vessels during surgery), which predicts the level of intimal damage in the vessel

Once the patient arrives in the operating theater, the amputated part should undergo a careful assessment for suitability for replanting. All structures should be dissected and identified, especially the neurovascular bundle. If no suitable vessels are identified, then replantation should not proceed. Usually, there is an order for repair of structures:

• Bone fixation with or without bone shortening to allow repair of soft tissue
• Tendon? repair – extensor and flexor tendons
• Nerve repair
• Arterial anastomosis
• Venous anastomosis (if suitable veins are present)

Bone fixation should be simple and quick to perform, but it also depends on the configuration of bony injuries. Usually, two Kirschner wires are an option, but other fixation methods may also be used (i.e., plate fixation). Occasionally, bone shortening is required before fixation to allow for soft tissue closure and repair of neurovascular structures without excessive tension.

Complications

Complications classify according to the time of onset[rx]

• Early complications

  • Arterial insufficiency

    • Arterial thrombosis? presents typically as a pale, cool and pulseless digit
    • It is vital during the post-operative period to maximize blood flow through the anastomoses and prevent thrombosis?
  • Venous insufficiency

    • Venous congestion typically presents as a purple digit with brisk capillary refill and swelling?
    • Concerns of possible anastomosis failure or thrombosis? should prompt urgent return to theatre for salvage – in cases of venous congestion, leech therapy or anticoagulation may be considered to improve venous return
  • Infection?
• Late complications

  • Cold intolerance
  • Tendon? adhesions
  • Stiffness?
  • Bony malunion
  • Altered sensation

Postoperative and Rehabilitation? Care

Post-operative management:

• Maintain adequate hydration and circulation volume
• Analgesia
• Keep the affected limb elevated and warm
• Frequent monitoring of the replant capillary refill, color, and temperature
• Avoid dressings changes in the first 48 to 72 hours to minimize manipulation of the repair
• Consider anticoagulation
• In cases of artery-only replants, consider stab incision to the distal amputated tip and apply heparin soaked gauze to allow venous drainage or use leeches instead. This treatment can end once the finger becomes pink with normal capillary refill thus indicating adequate venous drainage

Some patients require further surgery to improve their function, such as tenolysis, bone grafting, tendon? transfer, etc.[rx] On average, following upper limb amputations, patients return to work within 2 to 3 months after injury.[rx] Studies show that functional recovery is better in more distal injuries than proximal, both in terms of movement and power.[rx]

References