Digit Replantation

Indications for Replantation

Absolute Indications (Strongly Favoured)

• Thumb amputation at any level — the functional loss from a missing thumb is about 40-50% of hand function; even a stiff, sensate thumb provides key pinch and opposition that no prosthesis can replicate
• Multiple digit amputations — replantation preserves grip, pinch and hand function; the more digits preserved, the better the overall outcome
• Amputations through the palm, wrist or forearm — larger vessel calibre and greater vessel length favour microvascular repair; functional return is higher than for distal digital replants
• Any amputation in a child — children have superior neural plasticity, better tendon glide after repair, and lower adhesion formation; outcomes are consistently better than in adults

Relative Indications

• Single digit proximal to the FDS insertion (zone II proximal) — proximal-level replants have better functional return because the flexor mechanism is more robust
• Sharp, clean (guillotine) amputations — minimal soft tissue damage and well-defined vessel ends favour successful repair
• Patient is young and highly motivated — replantation demands prolonged rehabilitation and multiple procedures; motivation is critical
• Amputations in dominant hand for manual workers — function preservation outweighs the risks of a prolonged recovery in patients whose livelihood depends on hand use

Relative Contraindications

• Single digit distal to the FDS insertion in zone II — revision amputation and early prosthetic fitting often gives better function than a stiff, painful, insensate replanted finger; this is the most common scenario where replantation is NOT recommended
• Severe crush or avulsion injury — the zone of injury extends far beyond the visible wound; vessel ends are damaged over a long segment and extensive debridement is needed; outcomes are poor
• Prolonged warm ischaemia — greater than 12 hours for a finger or greater than 6 hours for a thumb in warm ischaemia significantly increases the risk of no-reflow and irreversible microvascular damage
• Multilevel (segmental) injury — each level requires separate repair, multiplying anastomoses and dramatically increasing failure risk
• Significant comorbidities — poorly controlled diabetes, peripheral vascular disease, advanced age, smoking, and anticoagulant therapy increase failure rates
• Self-inflicted amputation — psychiatric assessment is mandatory; replantation is technically possible but the psychological context requires careful evaluation
• Associated life-threatening injuries — damage control and patient survival always take priority over digit salvage

Tamai Classification of Digital Amputations

Mechanism of Injury and Prognosis

• Guillotine (sharp): Clean cut, minimal soft tissue damage, excellent vessel ends. Best prognosis. Survival rates up to 90% or higher.
• Limited crush: Moderate zone of injury, vessels damaged over a short segment. Trim back to healthy intima. Good prognosis. Survival 70-85%.
• Severe crush: Extensive zone of injury, comminuted bone, destroyed soft tissue envelope. Poor prognosis. Survival 40-60%. High rate of secondary procedures.
• Avulsion: Vessels torn from their beds over long segments; nerve and tendon may be pulled out proximally (ring avulsion). Worst prognosis. Survival 30-50%. Vein grafts almost always needed.

Key Evidence

Digital Neurovascular Anatomy — Replantation Perspective

Digital Arteries

• The proper digital arteries arise from the superficial palmar arch (ulnar-dominant) and the deep palmar arch (radial-dominant)
• Each finger receives a radial and an ulnar proper digital artery running alongside the digital nerves on either side of the flexor sheath
• At the mid-proximal phalanx level, the arteries are approximately 1-2 mm in diameter — suitable for microvascular anastomosis with 10-0 nylon
• The common digital arteries bifurcate in the palm at the level of the metacarpal necks — in palm-level amputations these larger vessels (2-3 mm) are available for repair
• Arterial vasa nervorum supply the digital nerves — preserving arterial flow is important for nerve recovery after repair

Digital Veins

• Dorsal digital veins are larger and more numerous than volar veins at the same level
• At the proximal phalanx level, 2-4 dorsal veins (1-2 mm diameter) are typically available for anastomosis
• Volar veins are smaller and deeper — used as supplement when dorsal veins are insufficient
• In distal replantation (zone I, distal phalanx), veins may be too small for anastomosis — an artery-only repair with heparinisation and bleed-through is acceptable
• In the thumb, the princeps pollicis artery (terminal branch of the radial artery) and 2-3 dorsal veins are the primary targets

Digital Nerves

• The median nerve supplies the volar aspect of the thumb, index, long, and radial half of the ring finger
• The ulnar nerve supplies the volar aspect of the ulnar half of the ring finger and the little finger
• Each digital nerve is approximately 1.5-2 mm in diameter at the proximal phalanx level — suitable for epineurial repair with 9-0 or 10-0 nylon
• Nerve recovery after digital nerve repair in replantation is slower and less complete than in isolated nerve repair — ischaemia time, scarring, and adhesions all impair regeneration
• Two-point discrimination of 5-10 mm is a reasonable expectation for a successful nerve repair after replantation; protective sensation returns earlier

Flexor Tendon Anatomy — Zone II Replantation Dilemma

Zone II (No-Man's Land) Considerations

• Zone II extends from the distal palmar crease to the FDS insertion at the middle phalanx
• The FDS and FDP tendons share a narrow fibro-osseous canal bounded by the A2, A3, and A4 pulleys
• In a zone II amputation, both tendons are divided and the canal is disrupted by the injury
• Bone shortening during replantation effectively shortens the canal and may reduce adhesion formation
• The dilemma: repairing both FDS and FDP in this constrained space creates a high risk of tendon adhesion and profound stiffness

Pulley System Preservation

• The A2 and A4 pulleys must be preserved or reconstructed to prevent flexor tendon bowstringing
• If bone shortening has sacrificed the A2 pulley attachment, reconstruction with a slip of the FDS tendon or an extensor retinaculum graft is required
• The A1 pulley can be released if needed for tendon glide — but avoid releasing A2 and A4

Bone and Joint Considerations

Bone Shortening

• Bone shortening serves two purposes: (1) removing comminuted, contaminated or non-viable bone segments, and (2) reducing tension on repaired vessels, tendons and nerves
• Typical shortening: 5-10 mm in clean amputations; up to 20-30 mm in crush injuries
• In transverse amputations, the cut bone ends are trimmed to create flat, parallel surfaces for stable fixation
• In oblique amputations, the oblique cut itself can be used for fixation (step-cut or oblique osteotomy) — this preserves length

Fixation Options

• K-wires: 0.9-1.2 mm K-wires are the most common — 2 crossed K-wires provide adequate stability for replantation; they are quick, cheap and easy to place but do not allow early mobilisation
• Intraosseous wiring: for oblique or transverse fractures; provides good compression but technically demanding in a small bone fragment
• Mini-fragment plates and screws: allow earlier mobilisation but require more soft tissue stripping and dissection; useful in proximal amputations where bone stock is sufficient
• External fixation: rarely used for single digit replantation; may have a role in multiple digit or proximal amputations

Preparation and Transport

Amputated Part Preservation

• Wrap the amputated part in saline-soaked gauze
• Place inside a sealed plastic bag (to prevent maceration)
• Place the bag on ice (NOT in direct contact with ice — frostbite damages the microvasculature)
• Transport with the patient to the replant centre as rapidly as possible
• Document the time of amputation and the time the part was cooled

Pre-Operative Assessment

• Assess the patient for associated injuries (polytrauma is common in industrial and machinery accidents)
• Assess the amputated part: mechanism, level (Tamai zone), contamination, vessel and nerve condition
• Assess the patient: age, occupation, dominant hand, comorbidities (diabetes, smoking, vascular disease, psychiatric history), anticoagulant use
• Warm ischaemia time: if cool ischaemia was achieved within 1-2 hours of amputation, the clock effectively resets to the cool ischaemia budget
• Obtain informed consent: explain survival rates (approximately 70-85% overall, lower for crush and avulsion), expected recovery time (6-12 months for maximal improvement), need for secondary procedures (tenolysis, capsulotomy, nerve graft, aesthetic revision), and the option of revision amputation

Operative Sequence — Step-by-Step

Step 1: Debridement and Tagging of Structures

Under tourniquet control (forearm tourniquet, 200-250 mmHg), perform thorough debridement of both the amputated part and the proximal stump.

• Debride the amputated part first: remove all non-viable skin, muscle, fat and contaminated tissue. Irrigate with copious amounts of normal saline. Identify and tag the digital arteries (2), veins (2-4), and both digital nerves (2) with 6-0 Prolene sutures.
• Debride the proximal stump similarly. Identify and tag matching structures.
• Assess the vessel ends under surgical microscope (magnification 10-25x): healthy intima appears smooth, glistening and intact. Crushed intima appears ragged, with subintimal haemorrhage and intimal flaps. Trim vessel ends back to healthy intima — this may require extending the dissection by several millimetres.

Step 2: Bone Shortening and Rigid Fixation

Shorten the bone sufficiently to: (1) remove all non-viable or contaminated bone, (2) allow vessel, nerve and tendon repairs to be performed without tension, and (3) achieve stable internal fixation.

• Trim the bone ends to create flat, parallel surfaces (transverse amputation) or use the existing oblique cut if it provides a stable configuration (oblique amputation)
• For transverse amputations: use 2 crossed 0.9-1.2 mm K-wires driven from proximal to distal (or use a single longitudinal K-wire through the medullary canal combined with an oblique K-wire for rotational control)
• Ensure K-wires do not protrude through the distal tip excessively (bend the distal ends over to prevent migration and soft tissue irritation)
• Confirm fixation stability by gentle stress testing under fluoroscopy — no movement at the osteotomy site

Step 3: Extensor Tendon Repair

Repair the extensor tendon over the dorsum of the digit before the flexor tendons.

• Use 4-0 non-absorbable suture (Prolene or Ticron) with a modified Kessler or core suture technique
• For zone V-VI (over the MCP and proximal phalanx), the extensor mechanism is broad and repair is straightforward
• For zone I-III (over the PIP, DIP and middle phalanx), the extensor tendon is thin — a meticulous running or figure-of-eight repair with 5-0 nylon may be needed
• Adjust tension so the digit rests in a functional position — not hyperextended or flexed

Step 4: Flexor Tendon Repair

The flexor tendon repair in replantation is technically demanding, particularly in zone II.

• Zone I (distal to FDS insertion): repair only the FDP tendon — no FDS in this zone. Use a core suture (4-strand Kessler or modified Tsuge) with a running epitendinous suture (6-0 nylon).
• Zone II (FDS to FDS insertion): the most controversial decision in replantation. Options: (1) repair FDP only and excise the FDS stump (preferred by many experienced replant surgeons — reduces adhesions), (2) repair both FDS and FDP and accept the risk of adhesions with a planned secondary tenolysis at 3-4 months, or (3) repair FDP and leave the FDS unstretched for staged reconstruction.
• Zone III-V (palm): repair both FDS and FDP — the broader canal in the palm accommodates both tendons with less risk of adhesion.
• In all zones, pass the core suture through the tendon stumps, tighten, and reinforce with a running epitendinous repair. Ensure the repair glides freely through the pulleys without catching.

Step 5: Deflate Tourniquet and Begin Microvascular Repair

Critical step: deflate the tourniquet before starting any microvascular anastomosis. Arteries and veins must be distended with blood so the intima is visible, the lumen is open, and the vessel ends can be properly coapted.

• Apply a proximal rubber dam (Penrose drain) or vessel loops at the base of the digit to achieve haemostasis at the anastomosis site
• Confirm haemostasis with bipolar diathermy — a bloodless field is essential for microvascular work
• Set up the operating microscope (magnification 16-25x for digital vessel anastomosis)

Step 6: Arterial Anastomosis

Repair the digital arteries before the veins — establish inflow first.

• Choose the artery with the best intima and most favourable orientation for repair (usually the ulnar digital artery for the index-long fingers; both arteries for the thumb)
• Apply microvascular clamps to both vessel ends — ensure gentle, even pressure to avoid intimal crush injury
• Perform adventitial stripping: use micro-scissors to trim adventitia 1-2 mm from each cut end — loose adventitial fibres can enter the lumen and cause thrombosis
• Irrigate the lumen with heparinised saline (100 units/mL)
• Approximate the vessel ends — if there is a gap, harvest an interpositional vein graft from the volar forearm (cephalic vein branches) or the dorsal foot, reverse it (valve orientation), and interpose
• Place the back wall first: 10-0 nylon, simple interrupted sutures, 8-12 sutures total for a 1-2 mm digital artery
• Place the front wall sutures, ensuring intima-to-intima apposition
• Release the clamps: check for inflow (bleeding from the distal cut ends of veins confirms arterial inflow through the capillary bed) and check for leaks (repair any anastomotic leaks with additional sutures)

Step 7: Venous Anastomosis

Repair veins after arterial inflow is established — outflow must follow inflow.

• Identify at least 2 dorsal veins (the dorsal veins are larger and more numerous than volar veins)
• Tag all identified veins during debridement (step 1) so they can be located efficiently
• Use the same microvascular technique as for arteries: adventitial stripping, heparinised saline irrigation, back-wall first, 10-0 or 11-0 nylon
• Aim for at least 2 patent venous anastomoses per arterial repair
• If veins are too short, use interpositional vein grafts (same donor sites as arterial grafts: volar forearm, dorsal foot)
• After releasing the venous clamps, the digit should pink up, warm, and develop capillary refill within 2-3 minutes

Step 8: Nerve Repair

Repair both digital nerves with epineurial repair under the operating microscope.

• Use 9-0 or 10-0 nylon, simple interrupted sutures, 4-6 sutures per nerve
• Approximate the epineurium without tension — if a gap exists, use an interpositional nerve graft (median or ulnar dorsal cutaneous branch donor, or a sural nerve graft for larger gaps)
• Ensure the fascicular groups are aligned — gentle approximation of the epineurium without fascicular dissection is the standard technique for digital nerves
• In zone II and III, the nerves lie alongside the arteries and are identified during vascular dissection

Step 9: Skin Coverage

Close the skin loosely over the repaired structures.

• If the skin closes without tension, use 4-0 or 5-0 nylon simple interrupted sutures
• If tension exists, do NOT close under tension — use a full-thickness skin graft from the hypothenar eminence, groin, or volar forearm
• If bone, vessel or tendon is exposed and grafting is not possible, use a local flap (cross-finger, thenar, or distant pedicle flap such as a groin flap)
• Leave the skin loosely closed to accommodate post-operative swelling — a tight skin closure will compress the venous anastomoses

Zone I (Distal Phalanx) — Special Technique

• Artery-only repair: distal to the DIP joint, veins are too small for anastomosis. Repair the single digital artery and rely on bleed-through (controlled heparinisation) for venous drainage
• No tendon repair needed: the FDP insertion at the distal phalanx is beyond the amputation level in most zone I injuries
• Bone fixation: a single longitudinal K-wire through the distal phalanx is usually sufficient
• Success: zone I replantation has very high survival rates (greater than 90%) because the tissue volume is small, metabolic demand is low, and arterial-only repair is acceptable
• Post-op: apply heparin-soaked gauze around the nail fold; check for oozing; the part will ooze blood for 3-5 days — this is the expected venous drainage pathway

Post-Operative Protocol

Immediate Post-Operative Period (First 48 Hours)

• Admission: All replant patients are admitted to a monitored bed (ideally a specialist hand unit)
• Warming: Maintain the patient and the replanted hand at above room temperature — use a warming blanket or heat lamp directed at the hand; ambient room temperature at 24-26 degrees Celsius
• Elevation: Hand elevated above heart level on a pillow or specialised arm rest to reduce venous pressure
• Monitoring: Check the replanted digit every 30 minutes for the first 48 hours, then hourly for the next 24 hours:
  • Colour: pink (normal), pale (arterial insufficiency), blue-purple (venous congestion), mottled (no-reflow)
  • Temperature: warm (normal), cool (vascular compromise)
  • Capillary refill: less than 2 seconds (normal), 2-3 seconds (concern), greater than 3 seconds (venous congestion)
  • Swelling: mild (expected), moderate (concern), severe with tense skin (urgent — venous congestion)
  • Doppler signal: triphasic signal confirms arterial patency; loss of signal requires urgent return to theatre
• Needle prick test: if colour is equivocal, prick the digit with a 25G needle — bright red bleeding confirms arterial inflow; dark bleeding suggests venous congestion; no bleeding suggests arterial thrombosis or no-reflow
• Haematocrit monitoring: leech therapy and controlled oozing (zone I) can cause significant blood loss — check haematocrit and haemoglobin every 12 hours

Anticoagulation Protocol

• Aspirin: 150-300 mg daily for 3-6 weeks (most centres use this as the baseline anticoagulation)
• Low molecular weight heparin: some centres use therapeutic LMWH (enoxaparin 1 mg/kg BD) for the first 5-7 days, particularly in high-risk replants (crush, avulsion, single vein repair)
• Dextran-40: some centres use dextran-40 infusion (500 mL over 6-8 hours) for the first 24-48 hours — less common now due to renal and bleeding risks
• Heparin-soaked gauze: applied locally around the wound and nail fold, particularly in zone I artery-only replants
• There is no high-level evidence for an optimal anticoagulation protocol — practice varies between centres

Rehabilitation Timeline

Special Case: Paediatric Digit Replantation

Why Children Are Different

• Children have superior neural plasticity — sensory recovery after digital nerve repair is consistently better than in adults
• Growing bone and soft tissue remodel and adapt to the replant over time
• Tendon adhesion rates are lower and tendon glide recovery is better
• Children tolerate prolonged procedures better than expected
• Psychological impact of an amputation in a child is profound — replantation is strongly favoured

Special Considerations

• Replantation is indicated for virtually all paediatric amputations regardless of mechanism or level
• Use smaller suture materials (11-0 nylon for vessels, 10-0 for nerves)
• K-wire diameter may need to be smaller (0.7-0.9 mm) for small paediatric phalanges
• Post-operative immobilisation is shorter — children mobilise faster
• Plan for secondary procedures (Tenolysis, epiphysiodesis monitoring for growth disturbance at the replant site)

Special Case: Ring Avulsion Injury

Urbaniak Classification

• Class I: Circumferential laceration with intact neurovascular bundles — good prognosis, standard replantation
• Class II: Degloving with arterial injury but intact veins — moderate prognosis, arterial repair with vein grafts; venous repair may be possible
• Class III: Complete degloving with arterial and venous injury — poor prognosis; the neurovascular bundles are avulsed from their beds over a long segment; multiple vein grafts needed for both arteries and veins; tendon may be avulsed proximally

Replantation Technique in Ring Avulsion

• Identify both neurovascular bundles in the proximal stump — they may be retracted several centimetres proximally
• Measure the gap in each structure after debridement of the damaged segments
• Harvest interpositional vein grafts from the volar forearm (cephalic vein branches) — multiple grafts will be needed
• The artery and vein gaps are often long (5-10 cm) — expect to use multiple vein grafts
• Nerve grafts (sural or dorsal cutaneous branch donors) are almost always needed
• Survival rates for class III ring avulsion replantation are 30-50% — counsel the patient honestly

Special Case: Multiple Digit Amputation

Prioritisation Principles

• Replant the thumb first — it is the most functionally important digit
• Replant the index and long fingers next (key pinch and grip)
• The ring and little fingers are less critical for function — consider using them as parts donors (composite tissue grafts) for the more important digits if vessel length is insufficient
• If all amputated parts cannot be replanted, use a non-replantable part as a source of vein grafts, nerve grafts, or skin

Technical Considerations

• Multiple simultaneous replantations are extremely time-consuming (8-16 hours)
• Two surgical teams operating simultaneously (one on the stumps, one on the parts) reduce total operative time
• Use a single team for microvascular anastomosis — consistency of technique improves patency rates