Replantation is the surgical reattachment of a body part that has been completely amputated. Revascularisation is the restoration of blood flow to a part that remains partially attached but is critically ischaemic. Both are managed by the same microsurgical team using the same principles of bone fixation, tendon repair, microvascular anastomosis and nerve coaptation.

The history of replantation began with the first successful thumb replantation by Komatsu and Tamai in 1968 in Japan, followed by the world's first arm replantation in 1962 (Malt and McKhann reported a 12-year-old boy with an arm replant). Modern digital replantation became clinically routine after the introduction of the operating microscope, fine monofilament nylon sutures (10-0, 11-0) and the development of structured post-operative monitoring and salvage protocols.

The decision to replant is not automatic. It is a calculated judgement based on:

• The mechanism of injury (sharp, crush, avulsion) - the most important predictor of success
• The ischaemia time (warm and cold) - dictates muscle viability and the risk of reperfusion injury
• The level of amputation (zone, digit, hand, more proximal)
• The patient (age, vocation, hand dominance, comorbidities, expectations)
• The resources (microsurgical team, theatre time, monitoring capability)

Indications (BSSH/ASSH consensus):

• Thumb amputation at any level - absolute indication; thumb is approximately 40% of hand function
• Multiple digit amputation - replant at least one or two to restore tripod pinch
• Single digit amputation in children - excellent functional recovery and nerve regeneration
• Single digit in selected adults - musicians, professionals with unique hand requirements
• Hand, wrist, forearm or arm amputation - survival and function are both reasonable in specialist units
• Bilateral digital or hand amputation - at least one side must be restored

Contraindications:

Absolute:

• Amputated part that is destroyed, severely crushed or degloved beyond surgical reconstruction
• Multiple-level amputation in the same digit
• Prolonged warm ischaemia beyond muscle tolerance (greater than 6 hours for digits, greater than 4-6 hours for hand/forearm)
• Medically unfit patient unable to tolerate 6-12 hours of anaesthesia
• Self-inflicted amputation in a psychiatrically unstable patient

Relative:

• Single finger amputation at zone II in an adult (the most debated indication)
• Avulsion injury with extensive vessel and nerve damage
• Severe contamination (farmyard, marine, sewerage)
• Prolonged ischaemia in a part containing significant muscle
• Patient unable or unwilling to commit to prolonged rehabilitation
• Surgeon or centre without microsurgical capability and no safe transfer pathway

Vascular anatomy of the digit:

• Each digit is supplied by two proper digital arteries that run on the ulnar and radial sides of the volar surface, just deep to the volar skin and superficial to the flexor tendon sheath
• The radial digital artery is usually the dominant vessel in the index, middle and ring fingers; the ulnar digital artery is dominant in the thumb and little finger (the "all-ulnar" thumb is a well-recognised variant)
• The arteries give off dorsal branches at each phalanx that supply the dorsal skin, nail bed and distal phalanx
• Venous drainage is predominantly by dorsal veins that lie in the subcutaneous tissue on the dorsum of the digit; volar veins exist but are smaller and less reliable
• The dorsal veins are the target for venous anastomosis - they are larger, more numerous, and easier to work with under the microscope

Nerve anatomy:

• The proper digital nerves run alongside the proper digital arteries on the ulnar and radial sides of the volar digit
• They are pure sensory nerves supplying the pulp, volar skin, dorsal distal skin and nail bed
• The dorsal sensory branch of the radial or ulnar nerve supplies the dorsum of the proximal and middle phalanges
• Coaptation must restore both volar and dorsal sensibility to prevent painful neuroma and to allow fine touch discrimination

Tendon anatomy:

• Flexor digitorum profundus (FDP) inserts on the volar base of the distal phalanx; flexes the DIP joint
• Flexor digitorum superficialis (FDS) inserts on the volar shaft of the middle phalanx; flexes the PIP joint
• The flexor tendon sheath (zone II of Verdan's classification) overlies the tendons from the distal palmar crease to the middle of the middle phalanx
• Extensor tendon is a single extensor digitorum communis (EDC) tendon over the proximal phalanx, with a central slip inserting on the middle phalanx base and lateral bands joining to insert on the distal phalanx base

Bone anatomy:

• The distal phalanx, middle phalanx and proximal phalanx are short tubular bones with good cortical purchase for K-wires
• The head of the phalanx flares slightly, making rigid plate fixation less common in digits; K-wire fixation (axial, crossed or longitudinal) is the workhorse
• In the hand (metacarpals) and forearm (radius, ulna), plate fixation is feasible and provides more rigid bone fixation, allowing early mobilisation

Ischaemia time and muscle tolerance:

• Digits (no muscle): warm ischaemia tolerated up to 6 hours; cold ischaemia (wrapped in saline-soaked gauze, placed in a sealed bag, then in ice water) tolerated up to 12 hours; some series report success at 24-30 hours of cold ischaemia
• Hand (small muscles of the hand): warm ischaemia less than 4-6 hours; cold ischaemia less than 10-12 hours
• Forearm and arm (large muscle bulk): warm ischaemia less than 4 hours; cold ischaemia less than 8-10 hours - the muscle is the limiting factor because of reperfusion injury, myonecrosis, myoglobinuria and renal failure

Biomechanical principle - bone shortening relaxes all repairs:

• Shortening the bone by 5-10 mm converts a high-tension vessel, nerve and tendon repair into a low-tension repair
• This is the single most important technical decision: do not try to perform a primary repair under tension - shorten the bone, then repair everything else
• A digital replant with 5 mm of bone shortening is functionally indistinguishable from one with no shortening; a digital replant with a failed arterial anastomosis from tension is functionally a dead digit

The replantation approach is not a true internervous plane - the dissection follows the wound edges and exposes the cut structures serially, identifying and tagging vessels, nerves and tendons for later repair. The relevant surgical intervals depend on the level and the digit:

For mid-digit replantation (zone I, II, III):

• Volar approach (preferred for vessel and nerve access): mid-lateral or Bruner-style zig-zag incisions on the volar aspect of the digit, identifying the flexor sheath, the proper digital neurovascular bundles, and the distal cut ends of the digital arteries and nerves
• Dorsal approach (preferred for venous access): a longitudinal or zig-zag incision on the dorsum of the digit and the hand, identifying the dorsal veins, extensor tendon and bone ends
• The two approaches (volar and dorsal) are used together - the volar for arteries and nerves, the dorsal for veins and bone fixation

For hand-level (palm, metacarpal) replantation:

• Extend the volar wound proximally into the palm using a Bruner or mid-lateral incision
• Identify the common digital arteries and nerves in the palm
• Identify the flexor tendons in the palm and tag them
• Expose the metacarpal fractures for fixation
• Use a separate dorsal incision over the metacarpals to identify the dorsal veins and extensor tendons

For wrist-level and more proximal replantation:

• Volar approach: extend the volar incision proximally to expose the median nerve, ulnar nerve, radial and ulnar arteries, and the flexor tendons
• Dorsal approach: separate dorsal incision to expose the extensor tendons, dorsal veins, and the radius/ulna for fixation
• The two approaches are linked by the circumferential skin at the level of injury, which is usually debrided and used to expose all structures

Structures to identify and tag on both sides of the cut:

• Both proper digital arteries (or the common digital arteries in the palm)
• Both proper digital nerves
• The flexor digitorum profundus and (where present) superficialis tendons
• The extensor tendon
• The dorsal veins (usually 2-4 dorsal veins per digit)
• The bone ends
• The digital skin edges (for orientation and length)

• Position: supine on a radiolucent operating table. The arm is extended on a hand table. The patient must be positioned to allow two surgical teams to work simultaneously - one preparing the amputated part on a separate instrument table, and one preparing the stump
• Anaesthesia: general anaesthesia is the standard for adults. Regional anaesthesia (axillary brachial plexus block) is used by some centres and may provide intra-operative vasodilation, post-operative analgesia and sympathetic blockade
• Tourniquet: an upper-arm or forearm tourniquet is used for the initial wound debridement and vessel identification, then released. Avoid prolonged tourniquet use once the anastomosis is being performed
• Microscope: an operating microscope (10x to 25x magnification) is mandatory for all vessel and nerve work. Some surgeons use loupes (4x-6x) for vein harvesting and nerve preparation
• Instruments: microsurgical instrument set - micro-forceps, micro-scissors, micro-needle holder, jeweller's forceps, vessel dilators, single and double micro-clamps
• Suture: 9-0, 10-0 and 11-0 monofilament nylon (Ethilon or similar) on a fine taper needle; 9-0 for larger proximal vessels, 10-0 for digital vessels, 11-0 for supermicrosurgical distal vessels
• Irrigation: heparinised saline (1000 units heparin in 100 mL normal saline) for vessel irrigation and irrigation of the cut vessel ends
• Pre-operative preparation of the amputated part: as soon as the part arrives in theatre, it is inspected, photographed, radiographed if bony injury is suspected, and the vessels, nerves and tendons are identified under the microscope and tagged. The part is kept cool (wrapped in saline-soaked gauze, sealed in a plastic bag, placed in an ice-water bath) and is only removed from cooling when the team is ready for the anastomosis
• Anticoagulation: prophylactic systemic heparin (low-dose, 5000 unit subcut or 1000 units IV per hour) is used by many centres during the anastomosis, but practice varies. Aspirin and dextran are used by some units; topical heparin irrigation of the vessel ends is universal

Replantation has a meaningful complication profile, both technical and functional. The overall survival rate in modern series is 80-90% for digits and 60-80% for hand/forearm amputations, but function and patient satisfaction are not guaranteed by survival.

Vascular complications:

• Arterial thrombosis - most common in the first 24-72 hours; presentation is sudden pallor, cool pulp, loss of Doppler signal. Managed by immediate re-exploration, thrombectomy, and revision of the anastomosis (often with a vein graft)
• Venous congestion - more common than arterial occlusion, particularly in fingertip replants; presentation is cyanosis, dark purple colour, brisk dark bleeding on pinprick. Managed by leech therapy (Hirudo medicinalis) for the first 24-48 hours, nail plate removal to allow bleeding, or re-exploration with revision venous anastomosis
• No-reflow phenomenon - despite a patent anastomosis, the microcirculation fails to reperfuse; the digit remains mottled and cool. Caused by prolonged ischaemia, reperfusion injury, and microthrombi. Difficult to manage; consider hyperbaric oxygen therapy, IV iloprost, or sympathectomy

Reperfusion injury (proximal replants):

• Compartment syndrome of the forearm/hand after prolonged ischaemia and reperfusion; managed by urgent fasciotomy
• Myoglobinuria and acute kidney injury after release of muscle ischaemia; managed by aggressive IV fluid resuscitation, urinary alkalinisation, and dialysis if needed
• Hyperkalaemia and acidosis on reperfusion; monitor and correct in real time

Nerve complications:

• Neuroma at the repair site, particularly if the nerve was repaired under tension; may require later neuroma excision and grafting
• Cold intolerance - very common, affecting 50-80% of replant patients; may persist for years; managed by warming, gloves, and reassurance
• Stiffness and dysaesthesia - particularly in zone II replants with poor flexor recovery

Tendon complications:

• Adhesions after zone II flexor tendon repair in the digital sheath; common cause of poor active flexion; managed by tenolysis at 3-6 months
• Rupture of the flexor or extensor repair; managed by re-repair or tendon grafting
• Lateral band migration and boutonniere deformity after central slip disruption

Bone complications:

• Nonunion or malunion at the osteotomy site; rare with K-wire fixation
• Pin-track infection with externalised K-wires; managed by pin care, oral antibiotics, and early K-wire removal
• Joint stiffness secondary to prolonged immobilisation; managed by hand therapy and dynamic splinting

Infection:

• Superficial wound infection - common; managed by oral antibiotics and wound care
• Deep infection / osteomyelitis - rare but devastating; may lead to loss of the replant

Systemic complications:

• VTE - uncommon in upper limb surgery, but reported
• Fat embolism - rare, but reported in major limb replants
• Drug reactions and transfusion complications - related to the long operation and blood loss

Functional complications:

• Stiffness - the commonest long-term problem; zone II replants have the worst prognosis
• Cold intolerance - 50-80% of patients
• Chronic pain - in a minority
• Failure of intrinsic muscle function after prolonged ischaemia
• Delayed tendon rupture - flexor or extensor

There is no single universal guideline for replantation, but international consensus exists through the major hand surgery societies on the core indications, sequence of repair and post-operative care.

Key guidance principles:

• American Society for Surgery of the Hand (ASSH) / American Academy of Orthopaedic Surgeons (AAOS): thumb, multiple digits, hand/wrist/forearm, and bilateral amputations are absolute indications. Single-finger amputation in an adult is a relative indication. The use of a structured hand therapy programme and routine clinical monitoring is recommended.
• British Society for Surgery of the Hand (BSSH): the BSSH endorses a similar list, with explicit emphasis on transfer of amputated parts and patients to a specialist replantation centre for any amputation that may be replantable. The standard is that the amputated part is wrapped in saline-soaked gauze, placed in a sealed bag, and the bag is placed in ice water - and the patient is transferred with the part.
• Japanese Society for Surgery of the Hand (JSSH): Japan has historically had the largest concentration of replantation expertise, with pioneering surgeons including Tamai, Komatsu, and Buncke. The Japanese experience underpins the modern understanding of the procedure.
• Federation of European Societies for Surgery of the Hand (FESSH) / EFORT: the European consensus mirrors the BSSH and ASSH, with the addition of structured outcome reporting using the Chen criteria (I-IV) and the Tamai criteria (I-IV) for functional assessment.
• International Federation of Societies for Surgery of the Hand (IFSSH): provides the global standard for training and credentialing in replantation, including the requirement for a microscope, micro-instruments, an experienced team and a post-operative monitoring protocol.

Registry evidence:

• There is no single global replantation registry comparable to the arthroplasty registries, but national audits in the UK (BSSH), US (ASSH), Japan (JSSH) and the Replantation Registry at the Kleinert-Kutz Hand Care Center (USA) have reported survival and functional outcome data.
• Large single-centre series (Tamai, Waikakul, Morrison) have shaped practice more than registries have.
• The Chen criteria classify functional outcome: I = excellent (return to work, normal range of motion, normal two-point discrimination), II = good (return to work, near-normal range of motion, slightly impaired two-point discrimination), III = fair (return to lighter work, limited range of motion, poor two-point discrimination), IV = poor (unable to return to work, severe stiffness, painful neuroma).

Global practice variation:

• East Asia (Japan, China, Korea, Taiwan): historically the highest volume of replantation in the world, with established regional and national centres of excellence. Replantation is offered more liberally than in the West; survival rates are consistently high.
• United States and Europe: the trend over the last 25 years has been more selective offering, particularly for single-finger zone II amputations in adults. Revision amputation with a tailored prosthesis is more commonly recommended than in East Asia.
• Low- and middle-income settings: replantation may be limited by the availability of a microscope, an experienced microvascular team, and the long operative and post-operative commitment. Transfer of the patient (with the part) to a regional centre is the standard.
• Distant and rural settings: the amputated part should be cooled, the patient stabilised, and transfer to a replantation centre should occur as soon as possible. Aeromedical retrieval with the part cooled in transit is well established.

Outcome reporting standards:

• Chen criteria and Tamai criteria are the most widely used functional outcome scores
• The DASH (Disabilities of the Arm, Shoulder and Hand) and MHQ (Michigan Hand Outcomes Questionnaire) are validated patient-reported outcome measures
• Cold intolerance is measured by the CISS (Cold Intolerance Symptom Severity) score
• Survival alone is no longer considered an adequate outcome; modern series report survival AND function AND patient satisfaction

Transfer protocol for the amputated part:

• Wrap the part in saline-moistened gauze
• Place in a sealed plastic bag
• Place the sealed bag in ice water (not dry ice - that freezes the tissue)
• Do not allow the part to soak in water or saline (causes maceration)
• Do not attempt to clean, debride or cannulate the part
• Transport with the patient; the part and the patient travel together
• Notify the receiving centre in advance so the team and theatre are ready