Digital replantation

1. After amputation of a single finger, replantation distal to the flexor digitorum superficialis insertion is generally justified, whereas replantation proximal to that insertion is seldom indicated in adults.

True

Urbaniak's 1985 series of 59 single-finger replantations showed 86% survival, but function depended on level: mean proximal interphalangeal motion was 82° for amputations distal to the flexor digitorum superficialis insertion and only 35° when proximal to it. A stiff proximal interphalangeal joint in an otherwise normal hand impairs overall hand function, so the superficialis insertion became the classical dividing line for single non-thumb digits. The rule is relative: thumb, multiple-digit and paediatric amputations are indications at any level, and recent patient-reported outcome data have begun to challenge the rule for proximal single-digit injuries.

• Urbaniak JR, Roth JH, Nunley JA, Goldner RD, Koman LA. The results of replantation after amputation of a single finger. J Bone Joint Surg Am. 1985;67(4):611-9. PMID 3980507
• Sebastin SJ, Chung KC. A systematic review of the outcomes of replantation of distal digital amputation. Plast Reconstr Surg. 2011;128(3):723-737. PMID 21572379

2. In the Urbaniak classification of ring avulsion injuries, class II denotes complete degloving or complete amputation of the digit.

False

Urbaniak's 1981 classification is based on circulation and continuity: class I, circulation adequate; class II, circulation inadequate with the digit in continuity, requiring revascularisation; class III, complete degloving or complete amputation. Nissenbaum designated the class II subgroup with arterial injury alone as IIA and called it an absolute indication for microvascular repair, and Kay and colleagues added skeletal injury to the scheme in 1989. Urbaniak originally advised completion amputation for most class III injuries, but later series show that selected complete avulsion amputations can be replanted with useful function.

• Urbaniak JR, Evans JP, Bright DS. Microvascular management of ring avulsion injuries. J Hand Surg Am. 1981;6(1):25-30. PMID 7204914
• Nissenbaum M. Class IIA ring avulsion injuries: an absolute indication for microvascular repair. J Hand Surg Am. 1984;9(6):810-5. PMID 6512189
• Tsai TM, Manstein C, DuBou R, Wolff TW, Kutz JE, Kleinert HE. Primary microsurgical repair of ring avulsion amputation injuries. J Hand Surg Am. 1984;9A(1):68-72. PMID 6693747

3. Because a digit contains no skeletal muscle it is generally accepted to tolerate about 12 hours of warm and 24 hours of cold ischaemia, and successful digital replantation has been reported after more than 90 hours of cold ischaemia.

True

Skeletal muscle is the ischaemia-limiting tissue, so muscle-free digits tolerate far longer ischaemia than a hand or forearm, for which reperfusion of necrotic muscle risks myoglobinuria, acidosis and hyperkalaemia. The conventional limits for digits are approximately 12 hours warm and 24 hours cold, with shorter intervals for proximal amputations. Wei and colleagues reported three digital replantations surviving 84, 86 and 94 hours of cold ischaemia with useful motion and no cold intolerance, so a long cold-ischaemia interval should not by itself preclude transfer for replantation of a properly cooled digit.

• Wolfe VM, Wang AA. Replantation of the upper extremity: current concepts. J Am Acad Orthop Surg. 2015;23(6):373-81. PMID 26001429
• Wei FC, Chang YL, Chen HC, Chuang CC. Three successful digital replantations in a patient after 84, 86, and 94 hours of cold ischemia time. Plast Reconstr Surg. 1988;82(2):346-50. PMID 3399566

4. The absence of a repairable vein is an absolute contraindication to fingertip replantation.

False

Artery-only replantation with a strategy to relieve venous congestion, such as controlled external bleeding from a pulp or nail-bed incision with heparin, medicinal leeches, arteriovenous anastomosis or delayed venous repair, achieved a pooled survival of 78.5% across 1,498 replantations in a 2022 systematic review, which concluded that lack of a vein should not be regarded as a contraindication. In a Chang Gung series 27 of 30 fingertips replanted without venous anastomosis survived, at the cost of an average of about a week of induced bleeding, frequent transfusion and a longer stay. Artery-only survival falls at Ishikawa subzone IV, and venous repair improves survival in both Tamai zones when a vein can be found.

• Crowe CS, Tolley PD, Mauch JT, Miller EA, Kao D. Management of Artery-Only Digit Replantation: A Systematic Review of the Literature. Plast Reconstr Surg. 2022;150(1):105-116. PMID 35536774
• Chen YC, Chan FC, Hsu CC, Lin YT, Chen CT, Lin CH. Fingertip replantation without venous anastomosis. Ann Plast Surg. 2013;70(3):284-8. PMID 22395045

5. Replantation of complete finger avulsion injuries has a lower survival rate, about 66%, than digital replantation in general, yet the pooled functional outcomes challenge routine revision amputation.

True

A systematic review of 32 studies found a mean survival of 66% for replanted complete finger and thumb avulsions, against the 80–90% usually quoted for replantation overall, with a mean total active motion of 174° and mean two-point discrimination of 10 mm in survivors; many had distal interphalangeal arthrodesis. The authors recommended attempting replantation when the proximal interphalangeal joint and superficialis insertion are preserved and revision amputation for skeletal injury at or proximal to that joint in patients unwilling to accept a poor functional result. Thumb avulsions are replanted regardless, because the functional gain is undisputed.

• Sears ED, Chung KC. Replantation of finger avulsion injuries: a systematic review of survival and functional outcomes. J Hand Surg Am. 2011;36(4):686-94. PMID 21463730