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ULNAR NERVE INJURY

Detailed Clinical Notes — MGR University BPT Exam 2026 (15 Marks)

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1. ANATOMY OF THE ULNAR NERVE

• Axilla: Runs medial to the axillary artery, between it and the axillary vein.
• Arm: No branches given in the arm. At mid-arm it pierces the medial intermuscular septum, passing to the posterior compartment in front of triceps.
• Elbow: Becomes superficial, lies behind the medial epicondyle in the ulnar groove (accompanied by the superior ulnar collateral artery). Enters the forearm between the two heads of flexor carpi ulnaris (FCU) - this entrance is called the cubital tunnel.
• Forearm: Descends along the medial forearm, lying anterior to flexor digitorum profundus (FDP), deep to FCU.
• Wrist: Passes anterior to the flexor retinaculum, on the lateral side of the pisiform, medial to the ulnar artery. Enters the Guyon's canal (between pisiform and hook of hamate, covered by volar carpal ligament).
• Palm: Divides into superficial (sensory) and deep (motor) terminal branches.

Note: The dorsal cutaneous and palmar cutaneous branches do NOT pass through Guyon's canal - this is clinically important for localizing the level of injury.

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2. CAUSES OF ULNAR NERVE INJURY

A. At the Elbow (Most Common Site)

1. Supracondylar fracture of humerus - direct injury by fractured segments or late injury by callus
2. Fracture of medial epicondyle - nerve is commonly injured; anterior transposition should be done at open reduction
3. Cubital tunnel syndrome - compression under humeral-ulnar aponeurosis (Feindel & Stratford, 1958)
4. Tardy ulnar palsy - chronic/delayed palsy due to:
   • Cubitus valgus from malunited lateral condyle fracture (gradual stretching)
   • Recurrent subluxation/dislocation of the ulnar nerve (found in 16.2% of 2000 elbows)
   • Shallow ulnar groove, hypoplasia of trochlea
5. Dislocation of the elbow
6. Prolonged external compression - leaning on hard surface with flexed elbow (ulnar groove syndrome)
7. Postoperative palsy - prolonged elbow flexion or pronation during surgery
8. Missile wounds / lacerations

B. At the Wrist

1. Lacerations (most common cause in civilian life)
2. Guyon's canal syndrome - compression by ganglion, lipoma, hamate hook fracture, ulnar artery thrombosis
3. Repetitive occupational trauma
4. Dislocations / fractures near the wrist

C. In the Forearm / Upper Arm

• Missile wounds, lacerations (may injure brachial artery and other nerves simultaneously due to proximity)

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3. CLINICAL FEATURES (Signs & Symptoms)

Sensory Loss

• Medial (ulnar) side of the hand and palm
• The whole of the little finger
• Medial side (ulnar half) of the ring finger
• Dorsum of the hand (medial aspect) - supplied by dorsal cutaneous branch
• Sensory loss does NOT extend above the wrist in ulnar nerve injuries at the elbow (if it does, suspect lower brachial plexus or C8/T1 root lesion)

Motor Paralysis

• FCU - wrist deviates radially on flexion against resistance
• Medial half of FDP (ring & little fingers) - loss of distal IP flexion
• All interossei
• 3rd & 4th lumbricals
• Hypothenar muscles (abductor, flexor, opponens digiti minimi)
• Adductor pollicis
• Deep head of flexor pollicis brevis

• FCU and FDP are spared (branches arise above wrist)
• Intrinsic muscles of hand only (as above minus FCU and FDP)
• The dorsal cutaneous branch is also spared in wrist lesions (it exits 5-8 cm above the wrist)

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4. DEFORMITIES

Claw Hand (Main en Griffe / "Ulnar Claw")

• Classic deformity of ulnar nerve palsy
• Involves ring and little fingers predominantly
• Posture: Hyperextension at metacarpophalangeal (MCP) joints + Flexion at proximal and distal interphalangeal (PIP and DIP) joints
• Mechanism: Loss of interossei and lumbricals (which flex MCP and extend IP joints) unopposed by long flexors and extensors
• Also called "benediction posture" or "ulnar clawing"

Paradox of the claw hand: Claw deformity is LESS pronounced in high (above elbow) lesions because FDP to ring and little fingers is also paralyzed, reducing the IP flexion component. It is MORE pronounced in low (wrist) lesions where FDP is intact. This is known as the "ulnar paradox."

Wasting

• Wasting of hypothenar eminence
• Wasting of first dorsal interosseous (most visible - guttering between 1st and 2nd metacarpals)
• Flattening of the normal transverse arch of the hand

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5. SPECIAL CLINICAL TESTS

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6. INVESTIGATIONS

1. Nerve Conduction Studies (NCS) / Electromyography (EMG)
   • Gold standard for localization
   • Shows focal slowing of motor conduction velocity across elbow segment (> 10-15 m/s slowing)
   • Conduction block: localized reduction in CMAP amplitude > 20-30%
   • Elbow flexed at 70-90 degrees for accurate measurement
   • Recording from first dorsal interosseous AND abductor digiti minimi increases yield
   • Found in > 75% of cases
2. X-ray - to detect bony abnormalities (cubitus valgus, fracture, medial epicondyle irregularity)
3. MRI / Ultrasound - to detect compressive lesions (ganglion, lipoma, cyst in Guyon's canal), nerve thickening

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7. TREATMENT

Conservative Management (Physiotherapy Role)

• Indicated for neuropraxia and mild compression neuropathies
• Activity modification - avoid leaning on elbow, avoid prolonged elbow flexion
• Splinting/Orthosis:
  • Anti-claw splint: blocks MCP hyperextension, allowing IP extension via intact extensors
  • Night elbow extension splint at ~30 degrees for cubital tunnel syndrome
• Exercises:
  • Passive and active range of motion to prevent joint stiffness
  • Strengthening of spared muscles
  • Tendon gliding exercises
  • Intrinsic-minus exercises as nerve recovers
• Sensory re-education after nerve repair
• Electrotherapy: TENS, NMES for muscle stimulation, ultrasound for scar

Surgical Management

• Most common surgical procedure
• Indicated in: tardy ulnar palsy, recurrent subluxation, cubitus valgus deformity, fractures of medial epicondyle
• The nerve is moved from behind to in front of the medial epicondyle
• Can be subcutaneous, intramuscular, or submuscular
• Should always be performed when there is risk of ulnar nerve involvement (e.g., open reduction of medial epicondyle fracture)

• Division of humeral-ulnar aponeurosis (cubital tunnel release)
• For cubital tunnel syndrome without subluxation

• Removal of medial epicondyle to decompress the nerve

• For acute lacerations - epineural suture repair
• Primary repair if tension-free; nerve graft (sural nerve) if gap is too large

• To correct claw hand deformity and restore pinch/grip
• Correction of claw: Zancolli lasso procedure, Brand tendon transfer (FDS to lateral bands)
• Restoration of adductor pollicis (Froment's): ECRB or FDS transfer

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8. LEVEL-WISE COMPARISON OF ULNAR NERVE INJURY

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9. ANATOMICAL VARIATIONS RELEVANT CLINICALLY

• Martin-Gruber Anastomosis: Fibers from median nerve join ulnar nerve in the forearm - may cause intact intrinsic function despite complete ulnar division at the elbow.
• Riche-Cannieu Anastomosis: Connection between median and ulnar nerves in the palm - may cause intact intrinsics despite wrist-level ulnar injury.

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10. KEY POINTS FOR EXAM (Summary)

• Ulnar nerve = C8, T1, medial cord of brachial plexus
• Most commonly injured at the elbow (medial epicondyle area) and wrist
• Key deformity: Ulnar claw hand (ring and little fingers, MCP hyperextension + IP flexion)
• Ulnar paradox: High lesion = less clawing; Low lesion = more clawing
• Froment's sign = adductor pollicis weakness
• Wartenberg's sign = abducted little finger
• Tardy ulnar palsy = late-onset palsy, classically after cubitus valgus
• Treatment: Anterior transposition is the standard surgery; anti-claw splint + physiotherapy conservatively
• NCS/EMG: elbow flexed 70-90 degrees; record from FDI and ADM
• Sensory: medial 1.5 fingers, medial palm, and dorsum of hand

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RADIAL NERVE INJURY

Detailed Clinical Notes — MGR University BPT Exam 2026 (15 Marks)

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1. ANATOMY OF THE RADIAL NERVE

1. Superficial radial nerve (SBRN) - purely sensory; descends under brachioradialis; emerges at wrist to supply skin of proximal two-thirds of extensor surfaces of thumb, index, middle, half of ring finger, and dorsum of hand
2. Posterior interosseous nerve (PIN) - purely motor; passes under the arcade of Frohse (proximal edge of supinator muscle) to supply all remaining wrist and finger extensors

• Posterior cutaneous nerve of arm - skin over triceps
• Lower lateral cutaneous nerve of arm - lateral lower half of arm
• Posterior cutaneous nerve of forearm - extensor surface of forearm and wrist
• Superficial radial nerve - dorsum of hand, dorsal thumb, index, middle and half of ring finger

Key anatomical fact: The radial nerve lies directly on bone in the radial groove - making it vulnerable to humeral shaft fractures. 22% of all humeral shaft fractures are associated with radial nerve injury.

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2. CAUSES OF RADIAL NERVE INJURY

A. At the Axilla (High Lesion)

1. Crutch palsy - improperly adjusted crutch pressing on axilla
2. Fracture-dislocation of the upper humerus or attempts at reduction
3. Honeymoon palsy - sleeping partner's head on arm compresses nerve
4. Shoulder joint replacement
5. Compressive dressing / lymph nodes

B. In the Spiral Groove / Mid-Arm (Most Common)

1. Fracture of humeral shaft - most common cause overall; nerve may be stretched, compressed by callus, or divided
2. Saturday night palsy - prolonged pressure from arm draped over a chair/edge during deep sleep (often alcohol-related); classic neurapraxia
3. Tourniquet paralysis - incorrect tourniquet placement on arm
4. Intramuscular injection injury - inadvertent injection into radial nerve
5. Pressure during surgery - arm resting at edge of operating table in pronation

C. At the Elbow / Posterior Interosseous Nerve (PIN)

1. Fracture or dislocation of the radial head
2. Radial tunnel syndrome - entrapment at one of five sites (LEAFS mnemonic)
3. Rheumatoid synovitis - synovial proliferation compressing PIN
4. Lipoma / ganglion in the radial tunnel
5. Arcade of Frohse entrapment (proximal edge of supinator)
6. Neuralgic amyotrophy (Parsonage-Turner syndrome)

• Leash of Henry (recurrent radial vessels)
• Extensor carpi radialis brevis (ECRB) tendon edge
• Arcade of Frohse (most common)
• Fascial band at the radial head
• Supinator (distal edge)

D. At the Wrist

1. Cheiralgia paresthetica (Wartenberg syndrome) - tight wristwatch, handcuffs, wrist surgery
2. Fracture of distal radius / de Quervain tenosynovitis

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3. CLINICAL FEATURES

Classic Deformity: WRIST DROP

• Inability to extend the wrist - wrist hangs in flexion by gravity
• Inability to extend the MCPjoints of fingers (extension of IP joints is preserved - done by interossei via extensor expansion, supplied by ulnar nerve)
• Inability to extend the thumb at MCP and IP joints
• Weakness of supination (though biceps can partially compensate)

Important exam point: "Extension of interphalangeal joints is done by interossei through the extensor expansions, supplied by the ulnar nerve - unaffected by radial nerve injury. This must not be mistaken for signs of regeneration." - S Das

Sensory Loss

• Sensory loss is relatively minor and inconsistent
• May be absent or very limited even with complete axillary division
• Autonomous zone (when present): small area over dorsum of first dorsal web space (between 1st and 2nd metacarpals, over first dorsal interosseous)
• In practice, sensory assessment is less clinically important for radial nerve

Level-Wise Clinical Features

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4. SPECIAL TESTS AND CLINICAL SIGNS

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5. INVESTIGATIONS

1. X-ray humerus - to identify humeral shaft fracture, callus, radial head fracture
2. Nerve Conduction Studies (NCS) / EMG
   • Confirms level and severity of injury
   • Saturday night palsy: conduction block across spiral groove (demyelinating) - good prognosis
   • Humeral fracture palsy: low amplitude CMAP (axonal loss) - worse prognosis
   • PIN lesion: normal radial SNAP; denervation only in PIN-supplied muscles; BR, ECRL, triceps spared on needle EMG
   • Cheiralgia paresthetica: low/absent dorsal radial SNAP; normal needle EMG
3. Ultrasound - enlarged cross-sectional area of radial nerve (>5.75 mm² at spiral groove is highly specific); detects hematoma, callus, soft tissue mass
4. MRI - detects soft tissue masses, edema pattern in muscles (denervation changes)

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6. PROGNOSIS

• Neurapraxic injuries (e.g., Saturday night palsy, tourniquet palsy) - excellent prognosis; recovery in 6-8 weeks
• Axonotmetic injuries (humeral shaft fractures, closed injuries) - recovery possible but slower; depends on axonal regrowth (1 mm/day) and distance from target muscle
• Humeral fracture-associated palsy - less favorable prognosis, protracted course, often incomplete recovery
• PIN neuropathy from trauma - generally good recovery with conservative treatment

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7. TREATMENT

Conservative / Physiotherapy Management

1. Splinting - Wrist Drop Splint (Cock-up Splint)
   • Holds wrist in 30-45 degrees of extension
   • Prevents contracture of wrist flexors
   • Allows functional use of the hand
   • Must be worn continuously until nerve recovers
2. Exercises:
   • Passive range of motion to all wrist and finger joints to prevent stiffness
   • Stretching of wrist flexors and intrinsics
   • Active-assisted and active exercises as nerve recovers
   • Strengthening of triceps, brachioradialis (if spared)
   • Functional retraining and activities of daily living
3. Electrotherapy:
   • NMES/FES to extensor muscles to maintain muscle bulk and reduce atrophy
   • TENS for pain management
   • Ultrasound for scar/callus management
4. Activity modification / Positioning:
   • Avoid sustained pressure on posterior arm
   • Correct positioning during sleep and work
   • Padding of elbow/arm area
5. Sensory re-education as nerve regenerates

Surgical Management

1. Exploration and primary nerve repair:
   • Indicated if nerve is divided (open wound, penetrating injury)
   • Epineural suture repair, tension-free
   • Nerve graft (sural nerve) if a gap exists
2. Neurolysis:
   • For nerve entrapped in callus or scar after humeral fracture
   • Incise scar and free the nerve
3. PIN decompression:
   • Division of arcade of Frohse and other tight structures in the radial tunnel
   • For PIN compression syndrome
4. Tendon transfers (for established paralysis - radial nerve palsy):
   • Goal: restore wrist extension, finger extension, thumb extension
   • Classic triple tendon transfer:
     • Pronator teres (PT) → Extensor carpi radialis brevis (ECRB) - wrist extension
     • Flexor carpi radialis (FCR) → Extensor digitorum communis (EDC) - finger extension
     • Palmaris longus (PL) → Extensor pollicis longus (EPL) - thumb extension
5. Management of humeral shaft fracture with radial nerve palsy:
   • Primary radial nerve palsy (present at time of fracture, closed injury): mostly neurapraxia - conservative management; observe for 3-4 months
   • If no recovery after 3-4 months: surgical exploration, neurolysis, or repair
   • Secondary radial nerve palsy (appears after manipulation/surgery): explore surgically

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8. LEVEL-WISE QUICK COMPARISON (High-Yield Table)

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9. COMPARISON: PIN SYNDROME vs RADIAL TUNNEL SYNDROME

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10. KEY POINTS FOR EXAM (Summary)

• Radial nerve = C6, C7, C8 (sometimes T1), posterior cord of brachial plexus
• Largest nerve of the upper limb; primarily motor
• Spiral groove is the most common site of injury (humeral shaft fracture, Saturday night palsy)
• Classic deformity = Wrist drop (inability to extend wrist and MCPs)
• Triceps is spared in spiral groove lesions (branches arise proximal to groove)
• IP joint extension is preserved in all levels (interossei - ulnar nerve)
• PIN lesion = finger drop + radial deviation on wrist extension, no sensory loss
• Saturday night palsy = neurapraxia, recovers in 6-8 weeks
• Treatment: cock-up/wrist extension splint + physiotherapy; tendon transfer for established palsy
• Classic tendon transfer: PT to ECRB, FCR to EDC, PL to EPL
• Autonomous sensory zone: dorsal web space between 1st and 2nd metacarpals

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