Radial Nerve Exploration

The question is almost always timing, not whether. The radial nerve is the most commonly injured peripheral nerve with humeral shaft fractures, yet the large majority of closed palsies recover without surgery. The skill is deciding who to operate on now, who to watch, and who will eventually need a tendon transfer.

Primary exploration — operate without waiting for any of: - Open fracture or penetrating injury (gunshot, industrial, laceration) over radial nerve territory with a palsy — primary exploration, debridement and nerve assessment; primary repair if a clean division leaves a gap less than 2 cm, cable graft if larger.

• Vascular injury needing operative repair — the brachial artery is approached anteriorly and the radial nerve is examined in the same field.
• Iatrogenic palsy recognised intraoperatively during humeral ORIF — explore immediately if nerve function is absent and there is no prior documentation of a palsy (distinguish tourniquet deflation palsy from a retractor or instrument injury).
• New palsy after a closed reduction — suggests the nerve is interposed in the fracture site; explore within 48–72 hours.
• A Holstein-Lewis fracture being fixed operatively anyway — inspect and protect the nerve in the same field (a closed Holstein-Lewis fracture managed non-operatively is observed, not explored). Secondary exploration — after failed conservative management. Most closed injuries recover spontaneously. The landmark evidence: Shao et al. (systematic review, 1045 patients) found overall recovery of 88% and spontaneous recovery of approximately 71% with no significant difference in final outcome between early exploration and expectant management; Ring, Chin and Jupiter (24 high-energy palsies) found every intact nerve and every closed-fracture palsy recovered, with transection confined to open fractures within complex limb injuries. Explore at 3–4 months if there is no clinical improvement AND no EMG reinnervation potentials — do not wait beyond 6 months from injury. | Timepoint | Assessment | Interpretation and action | |-----------|------------|----------------------------| | 6 weeks | Baseline EMG/NCS | Confirms denervation; excludes a pre-existing neuropathy | | 10–12 weeks | Repeat EMG | Early voluntary motor units equals a favourable prognosis — continue observation | | 16 weeks (4 months) | Repeat EMG plus clinical review | No motor units and no clinical change equals proceed to exploration | | 6 months | Final pre-transfer EMG | Significant deficit with no recovery equals explore or plan tendon transfer | PIN and radial tunnel syndrome. Posterior interosseous nerve compression in the radial tunnel presents with deep aching lateral forearm pain (often misdiagnosed as lateral epicondylitis), tenderness 4–5 cm distal to the lateral epicondyle and anterior to the radial head, a positive resisted middle-finger extension test, and finger extension weakness — with no wrist drop in early disease (ECRL is spared). Manage conservatively (rest, splinting, physiotherapy, activity modification) for 3–6 months before surgical decompression. The one decision that matters.

Consent specifically for incomplete recovery, the small risk of worsening an already-injured nerve, wound infection, haematoma, sural-nerve donor morbidity if a graft is needed, and the possible later need for tendon transfer. Setup. Lateral decubitus or prone for the posterior humeral approach; supine with the arm on an arm board for the anterior Henry and the Thompson/PIN approaches. Upper-arm tourniquet, loupe magnification, microsurgical instruments, and a nerve stimulator with nerve action potential (NAP) recording available.

The goal is to expose the radial nerve at its level of injury, assess its continuity, and do the minimum that restores conduction — external neurolysis of a viable nerve, decompression of an entrapped segment, repair or graft of a divided one, and complete decompression of the PIN through the radial tunnel. The exposure is the heart of the operation and is laid out in full below. Key anatomy that drives the approach. The radial nerve (posterior cord, C5–T1) exits via the triangular interval and winds the spiral groove with the profunda brachii artery at the middle-to-distal third junction; it then pierces the lateral intermuscular septum about 10 cm above the lateral epicondyle (the Holstein-Lewis zone), runs anteriorly between brachialis and brachioradialis/ECRL — giving off the brachioradialis and ECRL branches before the elbow — and divides at the radial head into the superficial radial nerve (sensory) and the PIN (motor). The PIN enters the supinator 3–4 cm distal to the radial head, beneath the Arcade of Frohse, and traverses the full length of supinator. That course dictates three exposures.

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The five PIN compression sites (FREAS). Before decompressing the radial tunnel, know the five structures that can compress the PIN — decompression proceeds through them in order.

Intraoperative decision-making — what to do with the nerve you find.

Structures at risk.

Immediate and early rehabilitation. | Phase | Timing | Management | |-------|--------|------------| | Immediate | Days 0–14 | Humeral-shaft exploration: posterior slab or functional brace (dictated by fracture fixation), plus a wrist cock-up splint holding the wrist in 30–40 degrees of extension for the wrist drop. PIN decompression: soft dressing only, with gentle active range of motion begun at 3–5 days. Elevation and analgesia; avoid NSAIDs for the first 48 hours if haemostasis is a concern. | | Early | Weeks 2–6 | Remove the splint at 2–3 weeks unless combined ORIF was performed. Active-assisted wrist and finger extension; extensor tendon gliding; passive wrist flexion to preserve joint mobility. A dynamic wrist-extension splint by day if active extension is absent; a static resting splint at night throughout recovery. | Serial EMG/NCS monitoring. | Timepoint | Action | Finding and response | |-----------|--------|----------------------| | 6 weeks | Baseline EMG | Confirms denervation; excludes a pre-existing neuropathy | | 10–12 weeks | Repeat EMG | Early voluntary motor units equals favourable prognosis — continue observation | | 16 weeks | Repeat EMG plus clinical review | No units equals proceed to exploration if not yet done | | 6 months | Final pre-transfer EMG | No recovery equals tendon transfer planning | | 12–18 months | Plateau assessment | Most nerve recovery is complete; remaining deficit is permanent | Tendon transfers for irreversible radial nerve palsy. A complete radial palsy loses wrist extension, finger MCP extension and thumb extension (ECRL/ECRB, EDC and EPL all denervated), so a balanced reconstruction needs three transfers — one for each function. The classic standard set: - PT to ECRB — restores wrist extension. Pronator teres is the standard, near-mandatory donor for wrist extension, not an optional extra.

• FCU to EDC OR FCR to EDC — restores finger MCP extension. FCU is powerful but sacrifices the main ulnar-deviating wrist flexor; FCR-to-EDC (Brand) is preferred by many because it preserves FCU and gives a more synergistic action.
• PL to rerouted EPL — restores thumb extension and retropulsion. Palmaris longus is expendable; reroute the EPL out of its third compartment to add abduction. If PL is absent, FDS of the ring finger can substitute. Common variants: the standard (FCU) set — PT-ECRB, FCU-EDC, PL-EPL; the FCR (Brand) set — PT-ECRB, FCR-EDC, PL-EPL; and the Boyes superficialis set — PT-ECRB, FDS(middle)-EDC, FDS(ring)-EIP+EPL — independent finger and thumb extension at the cost of two superficialis donors. Timing: not before 12–18 months when awaiting nerve recovery, with EMG showing no reinnervation and irreversibility confirmed. Where the nerve injury is known to be unreconstructable from the outset, an early PT-to-ECRB transfer acts as an internal splint while the other functions are awaited. Wrist-drop splinting during recovery. The wrist cock-up splint is a critical adjunct: it holds the wrist in 30–40 degrees of extension, preventing flexion contracture of the wrist and MCP joints, maintaining a functional hand position for grip, and protecting the extensor tendons from overstretch. Use a dynamic wrist-extension splint by day for partial function and a static resting splint at night; continue until active wrist extension reaches MRC grade 3 or better, with daily passive ROM and occupational therapy review every 4–6 weeks to adjust fit as oedema resolves. Expected recovery. | Scenario | Expected recovery | |----------|-------------------| | Closed injury, explored at 3–4 months | 80–90% good to excellent (MRC grade 4–5) | | Closed injury, explored at 4–6 months | 60–75% functional recovery | | Explored beyond 6 months | 40–50% partial recovery; higher transfer rate | | Nerve graft required | 50–70% good recovery depending on gap length | | Tendon transfers | Reliable functional restoration of wrist and digit extension | Peripheral nerve regenerates at approximately 1 mm per day (about 1 inch per month) — estimate reinnervation from the injury or repair site to the target muscle. For a spiral-groove lesion, distance to ECRL is about 12–15 cm (recovery 4–5 months) and to EDC about 25–30 cm (recovery 8–10 months after repair); add 4–6 weeks latency for axonal sprouting to begin at the repair site before counting down. Complications.

Epidemiology. Radial nerve palsy complicates roughly 11.8% of humeral shaft fractures (Shao, 2005); the middle and middle-distal shaft, and transverse and spiral patterns, carry the highest association. Transection is essentially confined to open injuries within complex upper-limb trauma. Surgical anatomy — proximal to distal. The radial nerve arises from the posterior cord of the brachial plexus (C5–T1) and leaves the axilla posterior to the axillary artery through the triangular interval (bounded by the long head of triceps, teres major and teres minor). It winds around the posterior humerus in the shallow spiral groove with the profunda brachii artery, at the junction of the middle and distal thirds (approximately 14–20 cm from the humeral head), covered by the lateral and medial heads of triceps. It exits the posterior compartment by piercing the lateral intermuscular septum approximately 10 cm proximal to the lateral epicondyle — the Holstein-Lewis entrapment site. In the anterior compartment it runs between brachialis (medially) and brachioradialis and ECRL (laterally), giving motor branches to brachioradialis and ECRL before the elbow (so these are preserved even with a PIN palsy), and passes anterior to the lateral epicondyle and radiocapitellar joint to divide into the superficial radial nerve and PIN at about the level of the radial head. PIN and the Arcade of Frohse. The PIN enters the supinator approximately 3–4 cm distal to the radial head. The Arcade of Frohse — the proximal fibrous arch of supinator — is present as a defined fibrous structure in approximately 30–55% of specimens (tendinous or membranous) and is the most common compression site. The PIN passes beneath the arcade into the supinator tunnel, traverses the full length of supinator (approximately 3–4 cm), and exits through the distal edge to innervate all the remaining finger and thumb extensors. Superficial radial nerve. A purely sensory branch, it courses along the radial border of the forearm beneath brachioradialis and exits between the brachioradialis and ECRL tendons approximately 8–10 cm proximal to the wrist to become subcutaneous (Wartenberg's point), supplying the dorsal radial hand and dorsal thumb, index and middle fingers to the PIP level. Fascicular organisation. At the spiral groove the ECRL and ECRB motor fascicles lie dorsoradially, the PIN fascicles dorsally, and the superficial radial nerve fascicles ventrally — an arrangement that allows targeted neurolysis and intraoperative stimulation mapping. Key evidence. | Study | Design | n | Finding | |-------|--------|---|---------| | Ring, Chin, Jupiter — JHS Am 2004 | Retrospective cohort | 24 | High-energy palsies: all intact and closed-fracture nerves recovered; transection only in open complex injuries | | Shao et al. — JBJS Br 2005 | Systematic review | 1045 | Overall recovery 88%; spontaneous recovery approximately 71%; early versus delayed exploration equivalent | | Venouziou et al. — Injury 2011 | Cohort | 18 | Low-energy palsies all recovered; high-energy carry a neurotmesis risk and worse prognosis | | Holstein and Lewis — JBJS Am 1963 | Original description | — | Defined the distal-third spiral fracture pattern associated with radial nerve palsy | | Spinner — JBJS Br 1968 | Anatomical study | — | Defined the Arcade of Frohse as the key PIN compression site |