EIP-to-EPL Tendon Transfer (EPL Rupture)

Primary indication. EPL rupture with inability to actively extend the thumb interphalangeal (IP) joint. The transfer is performed for: - Spontaneous EPL rupture after a distal radius fracture (most common — whether managed conservatively or operatively)

• EPL rupture in rheumatoid arthritis, after failed synovectomy or presenting with rupture
• Iatrogenic EPL rupture after ORIF of the distal radius (plate prominence, retractor injury, dorsal screw tip penetrating the 3rd compartment floor)
• Delayed presentation (greater than 3 weeks from rupture), where direct repair is no longer feasible
• Any EPL rupture with a gap defect or poor tendon-end quality Why EIP transfer, not a free graft. The EIP is a functioning, independently innervated motor that can be harvested in the same field and woven directly into the EPL stump in a single stage. A free tendon graft is a passive conduit that relies on the proximal EPL muscle belly and needs a junction at each end. EIP is the standard first-line choice; a graft (palmaris longus or plantaris) is reserved for when EIP is unavailable.

Timing. Operate as soon as the diagnosis is made, ideally within 6–12 weeks of rupture. Beyond about 12 weeks the FPL intrinsic muscle begins to contract and the EPL muscle belly loses excursion, which limits the eventual result. Surgery is still worthwhile in delayed presentations — but the earlier it is done, the better the outcome.

Consent. Counsel the patient about the splinting and recovery (4–6 weeks protected, full activity by 12–16 weeks), the expected outcome of useful thumb IP extension in the large majority, a small risk of a transfer that is too tight or too loose needing revision, dorsal numbness or a neuroma from a superficial radial nerve branch, and a modest (usually unnoticed) reduction in independent index extension at the donor site.

The goal is to harvest a functioning EIP, route it through the 3rd extensor compartment (the EPL's own anatomical line, redirected by Lister's tubercle), and weave it into the EPL distal stump under the correct tension so that the thumb regains active IP extension. The exposure — the three dorsal incisions and identification of the donor, the recipient stump and the routing channel — is laid out as the opening steps below.

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Lister's tubercle is the dorsal radial bony prominence that acts as a pulley for the EPL, redirecting it radially toward the thumb. The 3rd compartment groove lies on the ulnar side of the tubercle. After a distal radius fracture, haematoma accumulates in this rigid compartment and compresses the EPL's blood supply, while the fracture callus or a step in the floor of the groove abrades the tendon on its deep surface.

The operation in pictures

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Rehabilitation | Phase | Duration | Splint | Purpose | |-------|----------|--------|---------| | 1 | 0–3 weeks | Thumb spica with IP in extension; wrist neutral | Protect the Pulvertaft weave while it heals | | 2 | 3–6 weeks | Removable thumb spica; full-time except for exercises | Controlled active range of motion begins | | 3 | 6–10 weeks | Splint for sport and heavy activities | Progressive strengthening | | 4 | 10–16 weeks | No splint | Return to full activities | Exercise protocol - Week 3–4 (protected active motion): gentle active thumb IP extension within the splint; wrist tenodesis exercises (flex and extend the wrist while observing thumb motion). Avoid resisted extension for 6 weeks.

• Week 6–10 (progressive loading): active-assisted thumb extension against gravity; gentle supervised pinch and grip; begin IP flexion while ensuring the transfer is not tethered.
• Week 10–16 (return to function): progressive strengthening; graded manual tasks; return to contact sport generally at 12–16 weeks. Expected outcomes - Active thumb IP extension: useful extension restored in the large majority — excellent-to-good in 11 of 17 (65%) by the dedicated SEEM score (Lemmen 1999, PMID 10190604); the extension lag is reliably abolished when the tendon is coapted with the thumb in full extension (Lee 2015, PMID 26418770).
• Pinch and grip strength: generally returns toward, but slightly below, the contralateral side.
• Index function (donor): independent index extension preserved; index extension strength reduced by about 38% (Lemmen 1999) — usually subclinical and seldom noticed in daily activity.
• Return to work: desk work at 6–8 weeks; manual work at 12–16 weeks.

Complications

Epidemiology. Spontaneous EPL rupture is the classic late complication of a distal radius fracture, arising 6–8 weeks after injury — including non-displaced and minimally displaced fractures managed conservatively. The reported incidence after non-displaced fractures ranges from about 0.07 to 5 percent (Bogart 2020, PMID 30550417). Rupture also occurs in rheumatoid arthritis (from dorsal wrist tenosynovitis at Lister's tubercle), after ORIF (hardware abrasion or a dorsal screw penetrating the 3rd compartment floor), and rarely as a truly spontaneous event. Pathoanatomy and mechanism. The EPL runs in the 3rd extensor compartment, in the groove on the ulnar side of Lister's tubercle, which acts as a pulley redirecting the tendon toward the thumb. After a distal radius fracture two mechanisms combine: a haematoma accumulates in the tight, unyielding compartment and compresses the EPL's precarious blood supply (ischaemia), while the fracture callus or a step on the floor of the groove abrades the tendon on its deep surface where it hooks around the tubercle. The result is an attritional, ischaemic rupture with frayed, necrotic ends and a 2–4 cm gap — which is why direct repair fails. Saito 2025 (PMID 40449182) showed that a fracture line lying distal to Lister's tubercle and a tubercle with a shallow peak (radial peak higher than ulnar) significantly increase rupture risk, whereas the size and location of the tubercle alone do not. Key evidence. The modern tension target comes from Lee 2015 (PMID 26418770): in a prospective comparison of 24 transfers, coapting the tendon with the thumb IP in full extension achieved a mean +7.2° of extension, while coapting in neutral left a -5.2° lag — a significant difference. Lemmen 1999 (PMID 10190604), a 17-case outcome series using the dedicated SEEM score, found excellent-to-good thumb extension in 65%, with no marked loss of independent index extension and only a modest (~38%) reduction in index extension strength. Hong 2020 (PMID 32097314) showed that a wide-awake (WALANT) transfer — which allows active tensioning before closure — gives better early range of motion than general anaesthesia, with equivalent extension and strength. Bonatz 1996 (PMID 8640381) confirmed the classic post-fracture timing (median 7 weeks) and that both EIP transfer and a free palmaris longus graft give good results. Ha 2024 (PMID 38296255) reports the clinical outcomes of EIP-to-EPL transfer for EPL rupture. The consistent message — an attritional rupture that cannot be directly repaired, reconstructed reliably with an EIP transfer tensioned at wrist neutral with the thumb in full extension — is why this is a perennial viva favourite.