Pollicization (Index Finger Transfer)

Indication. Pollicization creates an opposable thumb where the native thumb cannot be reconstructed, in two broad groups: - Congenital thumb hypoplasia or aplasia — Blauth grade IIIB (hypoplastic thumb with an unstable or absent carpometacarpal joint), grade IV (floating thumb / pouce flottant) and grade V (complete aplasia). In grade IIIB the basal joint cannot resist the deforming pull of the thenar muscles, so soft-tissue reconstruction alone (opponensplasty, web deepening) will fail — pollicization is required. In radial longitudinal deficiency (RLD) the pollicization is usually combined with wrist centralisation on the ulna.

• Traumatic thumb loss — amputation at or proximal to the MCP joint with failed or non-viable replantation (crush, avulsion, prolonged ischaemia), a mangled thumb unsuitable for composite reconstruction, or failure of a prior thumb reconstruction. In isolated adult traumatic loss, toe-to-hand transfer is usually preferred; pollicization is reserved for multi-digit loss where the index is otherwise going to be sacrificed. Timing. For congenital cases operate at 1 to 2 years of age — the cortical plasticity for thumb-to-finger integration is greatest before age 3 and is significantly reduced beyond 5 years (Manske). For traumatic loss, operate as soon as soft tissues allow and the patient is medically fit. Contraindications.
• Absolute: a robust adjacent (middle) finger that could be transposed instead; an inadequate pedicle (no Doppler signal in either digital artery — toe transfer preferred); family or patient refusal; an anaesthetically unfit patient.
• Relative: severe global developmental delay (the child may not integrate the new thumb functionally); severe RLD with absent index AND middle finger (pollicization is not possible); an index finger with significant pre-existing deformity or injury. The one decision that matters. Pollicization versus toe-to-hand transfer is the central choice, and it rests on indication, donor morbidity and microsurgical feasibility:

Consent specifically for vascular compromise (1-3 percent, may require revision), malrotation or malposition (5-10 percent, may require revision), first web creep (15-20 percent, may require Z-plasty), stiffness, digital nerve neuropraxia, and the need for prolonged hand therapy. In congenital cases also discuss the frequently bilateral nature of the condition and staged contralateral surgery. Setup. Supine, arm abducted 90 degrees on a hand table, upper-arm tourniquet (about 250 mmHg in adults, lower in children). General anaesthesia in children (often with an axillary block in older patients); local infiltration (1 percent lidocaine with 1:100,000 epinephrine) after induction reduces tourniquet pain and bleeding. Typical tourniquet time is 90-120 minutes — release it 10-15 minutes BEFORE skin closure to verify perfusion. Pre-operative planning is the whole game: confirm the indication and the contralateral hand, Doppler or Allen-test the dominant pedicle, mark the desired rotation EXTERNALLY on the skin, mark the first web Z-plasty, and give prophylactic antibiotics (IV cefazolin at induction).

The goal: transpose the index finger onto the thumb ray remnant, after shortening its metacarpal, so the new thumb sits in about 120-160 degrees of axial rotation and 40 degrees of palmar abduction and opposes the remaining digits — while protecting the neurovascular pedicles throughout. The exposure is laid out in full as the first steps below (related approaches: Bruner volar zigzag approach to the digit and dorsal approach to the metacarpals and phalanges).

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Rehabilitation | Phase | Timing | Immobilisation | Therapy and activity | |-------|--------|----------------|----------------------| | Early | Day 0-14 | Thumb spica (long-arm plaster in children); web held abducted | Elevate above heart for 48-72 hours; check new-thumb perfusion every 1-2 hours for 24 hours; dressing change at 48-72 hours | | Intermediate | Weeks 2-4 | Sutures out at 10-14 days; K-wire out at 4 weeks | Begin protected mobilisation at 4 weeks; scar massage from 2 weeks | | Strengthening | Weeks 4-12 | Night web splint for 8-12 weeks | Progressive passive then active then resisted motion; light activities from 4-6 weeks | | Return to function | 3-6 months | Wean night splint | 3-6 months of structured therapy; final pinch and grasp 50-70 percent of the other side by 12-18 months; sport from 8-12 weeks | Most children return to school at 2-4 weeks (with the splint). Final pinch and grasp strength reach about 50-70 percent of the contralateral hand by 12-18 months, and the pollicized digit is used as a thumb for grasp, pinch and bimanual tasks in most patients. Secondary surgery (web deepening, opponensplasty revision) is needed in 15-25 percent. Complications

Epidemiology. Thumb hypoplasia or aplasia is the most common congenital thumb anomaly, and roughly 1 in 100,000 live births has thumb aplasia; it is frequently bilateral and strongly associated with radial longitudinal deficiency (where up to 90 percent of patients have thumb hypoplasia or aplasia). Blauth grades IIIB, IV and V are the indications for pollicization, and bilateral disease is the rule in RLD — families must be counselled about staged contralateral surgery. The index ray as donor. Pollicization re-uses native tissues, which is why it needs no microsurgical anastomosis:

• Skeletal — the index metacarpal head and a segment of shaft are excised; the shortened metacarpal base is fixed to the carpus (the trapezium remnant, or the scaphoid/trapezoid if absent) with a K-wire and capsular suture. The index proximal phalanx becomes the new thumb metacarpal, and the index middle and distal phalanges become the new thumb proximal and distal phalanges. No true CMC joint is created — the new basal joint is a fibrous union.
• Neurovascular — the radial digital artery is usually dominant; in RLD the ulnar digital artery dominates. The common digital artery to the second web is ligated DISTAL to its bifurcation with the middle finger radial digital artery. Two to three dorsal veins and both digital nerves are preserved and mobilised with the pedicle (the nerves lie volar to the arteries in the digit).
• Tendons — the FDP becomes the new FPL and the FDS is preserved as a check rein. The EIP and EDC to the index are shortened to retension the extensor apparatus.
• Skin — the dorsal skin paddle is preserved and transposed volarly to line the new first web, and the volar skin becomes the new thumb pulp. Classification (Blauth). The Blauth grade drives the decision to reconstruct soft tissue versus pollicize:

The exam trap is the grade IIIB thumb with a present but unstable CMC — it is NOT a candidate for soft-tissue reconstruction alone; pollicization is needed. Functional outcomes. Most children use the pollicized digit as a thumb for grasp, pinch and bimanual tasks, with grip strength of about 50-70 percent of the contralateral side. The new thumb does not grow like a native thumb (the metacarpal growth plate is excised), so the size differential becomes more apparent as the child grows, and secondary surgery is required in 15-25 percent. In traumatic loss in adults the trapezium is usually present and the intrinsics are normal, but cortical re-mapping is limited — the patient perceives the new thumb as an index finger in the thumb position, so counselling is critical. Key evidence. Buck-Gramcko (1971) established the modern technique with 120-160 degrees of axial rotation and 40 degrees of palmar abduction. Manske (1992) showed that children operated before age 3 integrate the pollicized digit far better than older children — the cortical re-mapping window is real. Taghinia and Upton (2011) confirmed pollicization as the gold standard for Blauth IIIB-V hypoplasia, and the long-term institutional experience (Taghinia, Littler and Upton, 2012) documents useful pinch and grasp in the majority with meticulous technique and early surgery.