Digital Replantation

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. ^[1] Amputation 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.

Carrel performed experimental replantation of a canine hind limb in 1906. ^[2] Malt successfully replanted a completely amputated arm in 1964, ^[3] and Meredith performed replantation after a distal radius/wrist injury in 1965. ^[4] Chinese surgeons at the Sixth People's Hospital performed successful replantations in the 1960s, but international recognition of digital replantation did not occur until 1968, with Komatsu and Tamai's report of a successful thumb reattachment.

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. ^[5] Although it is technically feasible to revascularize damaged digits, restoration of function and appearance is crucial and a patient-centric approach optimal.

Replantation of a thumb is important to maintain prehensile function and restoration of multiple digits is both cosmetically and functionally valuable. For some patients, the time and "cost" of a fingertip replantation is appropriate and surgeon bias should not prvent appropriate counseling or transfer. Delayed and suspended replantation with cooling of the digit(s)—cold ischemia of 12-15 hours—permits transfer of the patient with reasonable expectations of success. 

Frequency

Approximately 100,000 digital amputations occur per year in the US, and about 30% of those 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). ^[6] The decrease in replantations may be the result of more rigid selection criteria. ^[7] . Woo et al documented that dedicated replantation centers have higher suvival rates, with acceptable function, and that transfer after debridement and cooling of the amputated part (delayed replantation) is appropriate. ^[8]  

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.

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. ^[9] Muscle at room temperature is irreversibly damaged in 6-8 hours; if cooled, it can withstand a maximum of 8-12 hours of ischemia. However, digits contain no muscle tissue and if they are cooled without freezing, they may survive longer than 100 hours. 

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 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. Replantation of distal single or multiple digits is feasible and has good results. 

The most 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.

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. Very distal injuries may be appropriate depending on patient needs or desires and transfer to a center should be offered.

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. ^[10]

Postoperative patient education is crucial and includes the following:

• Avoidance of smoking and caffeine 
• Moderate elevation
• Antibiotics
• Hand therapy