Extensor Pollicis Longus Rupture

EPL rupture is the single most common closed tendon rupture in the hand and the prototype of attritional rupture at a fibro-osseous pulley. The classic scenario - sudden, painless loss of thumb extension weeks after an apparently trivial distal radius fracture - is a board-favourite because it tests understanding of tendon biomechanics, third-compartment anatomy, and the principles of tendon transfer.

The rheumatoid extensor ruptures follow a named, examinable pattern - Vaughan-Jackson syndrome:

• What it is: sequential, progressive rupture of the finger extensor tendons starting on the ULNAR side and marching RADIALLY - the extensor digiti minimi goes first, then the EDC to the small finger, then ring, then middle, and so on.
• The cause: attrition over the dorsally prominent, eroded distal ulna (caput ulnae) combined with dorsal tenosynovitis - the most ulnar tendons sit directly over the offending bone.
• The clinical clue: a rheumatoid patient who "cannot extend the little finger MCP," then weeks later the ring finger - the progressive ulnar-to-radial loss is the signature (and droop is at the MCP joints, with passive tenodesis lost).
• How it relates to EPL: the EPL is on the radial side, so it tends to rupture later in the sequence; finding an EPL rupture in a rheumatoid hand should prompt a search for (already ruptured) ulnar extensors.
• Distinguish from Mannerfelt syndrome: Vaughan-Jackson is extensor tendons over the caput ulnae; Mannerfelt is the FLEXOR (FPL) rupture over a scaphoid/trapezial osteophyte in the carpal tunnel. Both are attritional rheumatoid ruptures, opposite sides of the wrist.

Exam point: progressive ulnar-to-radial loss of finger extension in a rheumatoid hand = Vaughan-Jackson syndrome from caput ulnae - and the key adjunct to any tendon transfer is dorsal tenosynovectomy + treating the distal ulna (Darrach/Sauvé-Kapandji) to stop further ruptures.

EPL rupture: Loss of thumb extension in isolation, with a normal-appearing hand at rest and normal finger extension. Retropulsion sign is positive. PIN is intact.

PIN palsy: Global loss of finger and thumb MCP extension (wrist extension preserved via ECRL, often with radial deviation). The retropulsion sign is also positive, but finger extension is absent too. The deficit extends well beyond the thumb.

A common viva trap is to misattribute an isolated EPL rupture to a PIN palsy - always test finger and wrist extension in every patient with a 'dropped thumb'.

Plain radiographs of the wrist are mandatory in any patient with suspected attritional EPL rupture - the radiograph identifies the cause (DRF, RA, Kienböck, screw impingement) far more often than the radiograph confirms the rupture. Do not delay EIP-to-EPL transfer waiting for MRI in the post-DRF scenario; the diagnosis and decision are clinical.

The choice of EIP is not arbitrary; it satisfies the classic principles of tendon transfer (Boyes/Brand) that examiners expect you to recite for any transfer:

• Supple, mobile joints - the thumb IP/MCP and CMC must be passively correctable first (a stiff joint will not move however good the transfer); release contractures before transferring.
• Expendable donor - taking EIP leaves the index with the EDC, so index extension is preserved (the donor's loss must be tolerable).
• Adequate excursion - the donor's amplitude must match the recipient's need (EPL needs roughly 30 mm; EIP/finger extensors provide it).
• Adequate strength - one grade of power is typically lost after transfer, so the donor must be strong enough.
• Synergy - synergistic donors are easier to re-educate; EIP fires with finger/thumb extension, in phase with the lost EPL.
• Straight line of pull - the transfer should run as directly as possible to its insertion (hence the subcutaneous radial route, not back through the diseased 3rd compartment).
• One tendon, one function - a single transfer should ideally power a single action.
• Soft-tissue equilibrium / supple bed - a healthy, scar-free, well-vascularised bed is needed for gliding (the very reason direct repair of the attritional rupture fails).

Exam point: justify EIP-to-EPL by the transfer principles - expendable, synergistic, correct amplitude and a straight subcutaneous line of pull into a supple thumb - and remember the prerequisite of supple joints and a healthy bed.

Best prognosis: Young, post-DRF, healthy contralateral hand, transfer within 3 months, supervised hand therapy.

Guarded prognosis: Elderly rheumatoid with multiple tendon involvement, severe caput ulnae, late presentation with established thumb adduction contracture, dependent on disease control.

Key threshold: 3-6 months - delayed reconstruction still works but outcomes decline steadily. The transfer itself is reliable; the limiting factors are the bed, the disease, and the rehabilitation.

There is no dedicated registry for EPL rupture because it is a clinical diagnosis treated by an established, low-morbidity tendon transfer. The evidence base is dominated by retrospective case series and a few prospective cohorts (Chung KC et al.). The few randomised comparisons (EIP transfer vs interposition graft; early vs delayed reconstruction) favour EIP transfer as the first-line operation. The single most important practice point - tension the transfer with the thumb in full retropulsion - is consistent across all hand surgery traditions.