Replantation

Background

Replantation of completely amputated digits has been a medical reality since 1968, when Komatsu and Tamai first reported successful replantation of a completely amputated thumb. [1Amputation of digits is common. Approximately 100,000 digital amputations occur per year in the United States. Of those, an estimated 30% are suitable for replantation. The exact number of replantations performed yearly is unknown. However, the number appears to be decreasing, secondary to more rigid selection criteria, improved workplace safety procedures, and better-designed protection devices on power tools.

An image depicting digital amputation can be seen below.

Complete amputation of two digits. Complete amputation of two digits.

 

History of the Procedure

Carrel performed experimental replantation of a canine hind limb in 1906. [2Malt successfully replanted a completely amputated arm in 1964, [3and Meredith performed replantation after a distal radius/wrist injury in 1965. [4Chinese surgeons at the Sixth People's Hospital performed successful replantations in the 1960s. However, the first digital replantation occurred in 1968, with Komatsu and Tamai's report of a successful thumb reattachment.

Problem

A complete amputation occurs when the injured part is no longer attached to the patient. If any portion of the digit remains attached, a partial or near amputation has occurred, and the repair process is a revascularization, not a replantation. [5Although it is technically feasible to revascularize damaged digits, restoration of function and appearance is crucial and a patient-centric approach optimal.

Epidemiology

Frequency

As stated above, approximately 100,000 digital amputations occur per year in the US, and about 30% of these are suitable for replantation. A review of three national databases by Reavey et al found that the overall finger amputation incidence did not change significantly from 2001 to 2011 (26,668 versus 24,215, respectively; P = 0.097), although workplace finger amputation rates decreased 40% (P < 0.0001). The number of replantations fell from 930 in 2001 to 445 in 2011, a decrease of more than 50% (P < 0.001). [6The decrease in replantations may be the result of more rigid selection criteria. [7]

Etiology

Amputations of digits occur secondary to laceration, crush, avulsion, and combination injuries. They may occur at any location but frequently occur at work or at home. Amputations have been reported in children secondary to injuries from exercise equipment, car doors, and home doors. In adults, injuries occur from saws, knives, hydraulic wood splitters, and a variety of industrial machines.

Home injuries frequently involve table or circular saws. Work injuries are multifactorial, and demographics are changing constantly because safety equipment is added and equipment is adapted following mishaps to prevent similar occurrences.

Pathophysiology

Following amputation, cell death is irreversible if ischemia produces critical cell lysis. Prior to irreversible cell death, reperfusion is possible. Time from injury to reperfusion and salvage depends upon the type of tissue involved and the temperature of the injured part. [8Muscle at room temperature is irreversibly damaged in 6-8 hours; if cooled, it can withstand a maximum of 8-12 hours of ischemia. However, if digits are cooled without freezing, they may survive longer than 100 hours.

Presentation

The clinical presentation of a completely amputated digit is obvious. The important considerations are the level of the injury, the mechanism of the trauma, and the general health of the patient. In general, diagnostic testing is not indicated, with the exception of plain radiographs to evaluate bony integrity. Routine preoperative evaluation of the patient is critical. It may not be possible to determine replantation potential without exploration in the operating room.

Indications

Indications for surgical replantation have evolved over the last 20 years. The major indications for replantation in the absence of prolonged ischemia, segmental damage, and diffuse crush or severe avulsion injuries are amputations of the thumb, multiple digits, a digit in a child, and a digit distal to the flexor digitorum superficialis insertion.

Relevant Anatomy

The important anatomic consideration is the size of the injured vessel. In children older than 2 years, vessels proximal to the middle portion of the middle phalanx are more than 0.4 mm. In adults, digital arteries are more than 0.4 mm proximal to the lunula of the nail. The radial digital arteries to the thumb and the index finger, and the ulnar digital artery to the little finger are, in general, significantly smaller than the parallel vessels.

Contraindications

Relative contraindications to surgery are complete amputation of a digit proximal to the flexor digitorum superficialis insertion, severe crush or avulsion injuries, segmented injuries, and/or severe bony comminution with loss of bone and joint integrity.

Major contraindications to surgery are prolonged warm ischemia, crush or avulsion injuries with diffuse arterial damage, and/or inability to obtain reconstruction that would allow a functional digit.

A systematic evaluation of survival and function after replanted and revascularized avulsion injuries refutes the practice of routine revision amputation and supports careful consideration and the utilization of reconstructive options.

Replantation Workup


Laboratory Studies

No specific laboratory studies are generally necessary.

Imaging Studies

Plain anteroposterior and lateral radiographs of the digit and hand are important.


Replantation Treatment & Management


Medical Therapy

Appropriate antibiotics and wound care are indicated to prevent infection.

Preoperative Details

Amputated parts should be stored dampened with isotonic sodium chloride solution or Ringer's lactate in a cooled environment (on ice within a cooler or in a refrigerator). Contact with a saline ice bath may produce frostbite and should be avoided.

If possible, bleeding from proximal vessels should be controlled with pressure, and ligature control should be avoided.

Intraoperative Details

The normal sequence of the operative procedure is as follows [10:

  1. Debridement

  2. Identification and/or tagging of vital structures

  3. Skeletal stabilization

  4. Extensor tenorrhaphy

  5. Placing sutures within flexor tendon ends

  6. Digital artery repair [11]

  7. Neurorrhaphy of digital nerve

  8. Repair of flexor digitorum profundus

  9. Venous repair [1213]

  10. Skin closure

  11. Dressing

Debridement and exposure is a crucial aspect of the procedure and should be performed through an extensile midlateral incision when possible. This allows the wound to heal by secondary intention if excessive swelling is present, provides fasciotomies of the digits, and facilitates optimal exposure.

Following debridement, exposure and identification of nerves, arteries, veins, and tendons is helpful. This is performed under magnification using operating telescopes or the operating microscope.

The amount of bone shortening necessary is dictated by the extent of comminution and should be predicated on the ability to obtain adequate nerve, tendon, and skin approximation. Shortening to facilitate vascular repairs is not necessary because vein grafting is adequate. However, poor skin coverage, nerve grafts, and the inability to primarily repair tendons have a negative impact on long-term outcome.

Following appropriate shortening, the bone may be stabilized with longitudinal or crossed interosseous wires, interosseous wire and pin, or miniplates and/or miniscrews. [14Joint damage may be managed with prosthetic joints, resection arthroplasty, or fusion.

Following bone and/or joint stabilization, the extensor tendon mechanism is repaired. This improves stability. Flexor tendons may be repaired prior to or following arterial and nerve anastomosis. If the flexor tendons are to be repaired following arterial repair and neurorrhaphy, the placement of sutures prior to microprocedures will simplify the process and minimize iatrogenic injury. In general, arteries are repaired first using an operating microscope and appropriate microneedles and microsutures. The most common needle is 50-100 microns in diameter and controls a 10-0 or 11-0 suture. At the surgeon's discretion, a bolus of heparin may be given prior to clamp release or tourniquet release.

For logistical reasons, the digital nerve adjacent to the artery is repaired next. If not repaired previously, the tendon is approximated. The hand is then turned, and the veins are mobilized, trimmed to normal, and repaired under the operating microscope.

The skin is closed if it can be approximated without tension. If concern about skin tension exists, the midlateral incisions are left open or skin grafts are applied.

Postoperative Details

The involved extremity is placed in a bulky dressing; compression of the dorsal veins is avoided. Avoid constricting circular dressings because both flexor and extensor tendons have been repaired. Immobilization generally is with the wrist in a neutral position.

The timing of rehabilitation depends on the stability of the bone fixation, the adequacy of the tendon repair, and the tension on repaired neurovascular structures. Prior to wound closure, make an intraoperative assessment of the amount of safe active or passive motion so that it may be incorporated at the appropriate time during rehabilitation. Monitoring is clinical and often includes temperature probes or laser Doppler probes. [15]

In the perioperative period, tobacco and smoking products are avoided, [16caffeine and other stimulants are withheld, and the patient is asked not to use over-the-counter drugs. Thorazine often is used for its calming effect and because it maximizes subdermal plexus recovery. In addition, anticoagulants such as aspirin, Dextran 40, low-molecular-weight heparin, or heparin may be used. In general, Dextran 40, aspirin, and ibuprofen are used for clean cuts in which repairs were achieved without difficulty. If a significant crush or avulsion component is present and concern exists regarding vessel integrity distal or proximal to the anastomosis, heparinization may be considered.

Patients generally are kept in a warm, quiet room for 3-7 days and then are sent home on oral medications (eg, 1 aspirin a day or ibuprofen 200 mg tid).

Follow-up

Rehabilitation is performed under the supervision of a hand therapist and depends, in part, on the factors listed above.

Complications

The major complications of replantation include venous or arterial rethrombosis and infection. Infection frequently is the precipitating event in thrombosis.

In the first 24-36 hours, acute arterial injuries generally are handled by reexploration and additional arterial reconstruction. Similarly, early venous insufficiency may be handled with surgical exploration, heparinization, the use of leeches, or removal of the nail bed and the use of heparin-soaked pledgets to allow controlled bleeding.

Late complications include loss of motion from joint stiffness and tendon adhesions. Fusions, tenolysis, or both may be required. In addition, nonunions are common because distal fragments may be avascular.

Outcome and Prognosis

The outcome and prognosis are variable. [1718Thumbs have the best prognosis, [19as do digits amputated distal to the insertion of the flexor digitorum superficialis. [20212223]

Survival of digits was 80-90% for clean or sharp lacerations in the 1980s and 1990s; however, the rate of success of digit replantation was 57%, significantly lower than previous rates, at 2 academic level-I trauma hospitals from 1997-2010. [24Survivorship after avulsion injury may drop to 50-60%. Sensitivity, except in children, rarely is normal, but 2-point discrimination often is present. Cold sensitivity is a common problem, although it generally decreases over time. [2526The function of replanted digits is never normal. Sensation is protective in more than 90% of patients, but measurable 2-point discrimination is present in only 50% of patients.

In crush or avulsion injuries, protective sensation may drop to 80%, with 2-point discrimination in only 30% of patients. Pain persists after 3% of sharp injuries and 5% of crush avulsions. Occasionally, late amputations are required. Replantation distal to the insertion of the flexor digitorum superficialis results in an average of 85° of proximal interphalangeal (PIP) joint motion and excellent metacarpophalangeal (MP) joint motion. However, proximal to the flexor digitorum superficialis, PIP motion averages only 35°.

Historically, the prognosis for ring avulsion injuries is poor. [27Urbaniak divided ring injuries into the following 3 types, as follows [28:

  • Class 1 injuries have adequate circulation and are treated by standard bone and soft-tissue methods.

  • Class 2 avulsions have incomplete revascularization and are treated depending on the clinical circumstances.

  • Class 3 injuries are complete amputations with extensive degloving and are best treated with revision of the residual digit.

However, a systematic review by Davis Sears and Chung suggests that functional outcomes after replantation of avulsion injuries are better than historically cited and the routine practice of revision amputation should be reconsidered. These authors recommend attempting replantation of complete finger avulsion injuries with a preserved PIP joint and flexor digitorum superficialis tendon insertion.  [29]

Kay identified the following 4 classes of ring avulsion injury: [30]

  • Class 1 is similar to Urbaniak's.

  • Class 2 ring avulsions show inadequate circulation without skeletal injuries and are divided into arterial or venous. In general, these are reconstructed.

  • Class 3 injuries have inadequate circulation, either arterial or venous, and skeletal injury. They are managed after obtaining bony stability.

  • Class 4 ring injuries are complete and generally treated with revision of the residual digit.

The Davis Sears and Chung review suggests that the above criteria may be too rigid.

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