7.2 Peripheral Nerve Injuries & Deformities
Key Takeaways
- Seddon's classification categorizes peripheral nerve injury into Neuropraxia (conduction block, intact axon, full recovery in weeks), Axonotmesis (axonal disruption, intact sheaths, regenerates ~1 mm/day), and Neurotmesis (complete transection requiring surgical repair).
- High median nerve lesions produce the 'Hand of Benediction' upon active fist formation due to loss of FDS and lateral FDP, whereas low median nerve lesions produce the 'Ape Hand' deformity with thenar wasting, treated with a C-bar or thumb spica splint to maintain web space.
- Ulnar nerve lesions produce 'Claw Hand' (hyperextension of 4th/5th MCPs with IP flexion), evaluated via Froment's, Jeanne's, and Wartenberg's signs, and managed orthotically with an MCP flexion blocking (anti-claw) splint.
- High radial nerve lesions cause classic 'Wrist Drop' and loss of finger/thumb extension, requiring dynamic extension splinting to support the wrist in 20°-30° extension and assist MCP extension for functional release.
- Sensory re-education progresses through early-phase protective sensibility education and moving touch before constant touch (30 Hz to 256 Hz vibration), advancing to late-phase tactile localization, stereognosis, and object discrimination.
Last updated: August 2026
Peripheral Nerve Injuries & Deformities
Peripheral nerve injuries of the upper extremity significantly compromise hand function, manual dexterity, and sensory feedback. Successful occupational therapy intervention requires precise anatomical knowledge of motor and cutaneous innervation, rapid identification of classic clinical deformities, fabrication of specialized orthoses, and implementation of sensory re-education protocols.
1. Classification & Mechanics of Peripheral Nerve Regeneration
Peripheral nerve trauma is classified according to the structural integrity of the axon and surrounding connective tissue sheaths (endoneurium, perineurium, and epineurium).
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| SEDDON'S & SUNDERLAND'S NERVE INJURY CLASSIFICATION |
+---------------+------------+--------------------+----------------------+--------------------------+
| Seddon Class | Sunderland | Pathophysiology | Recovery Prognosis | Surgical / OT Management |
+---------------+------------+--------------------+----------------------+--------------------------+
| **Neuropraxia**| Grade I | • Local myelin | • Complete, sponta- | • Conservative management|
| (Class I) | | compression / | neous recovery in | • Maintain PROM & joint |
| | | ischemia. | days to weeks | mobility; splinting to |
| | | • Axon & sheath | (typically 3–6 wks)| prevent contractures; |
| | | fully intact. | • No Wallerian | avoid repetitive com- |
| | | • Conduction block.| degeneration. | pression. |
+---------------+------------+--------------------+----------------------+--------------------------+
| **Axonotmesis**| Grade II, | • Axonal disrup- | • Regenerates spon- | • Conservative monitor- |
| (Class II) | III, IV | tion with distal | taneously along | ing with serial MMT & |
| | | Wallerian degen- | intact endoneurial | sensory mapping. |
| | | eration. | sheath conduits. | • Orthoses to prevent |
| | | sheaths intact. | (approx 1 in/month)| denervated muscles. |
+---------------+------------+--------------------+----------------------+--------------------------+
| **Neurotmesis**| Grade V | • Complete tran- | • No spontaneous | • Mandatory microsurgical|
| (Class III) | | section of axon, | functional | repair (neurorrhaphy, |
| | | endoneurium, | recovery without | nerve conduit, or graft|
| | | perineurium, and | surgical inter- | • Post-op protective |
| | | epineurium. | vention. | splinting & sensory |
| | | • Complete loss. | • Incomplete return. | re-education. |
+---------------+------------+--------------------+----------------------+--------------------------+
Dynamics of Nerve Regeneration
- Wallerian Degeneration: Occurs distal to the injury site within 24 to 48 hours; macrophages clear axonal and myelin debris while Schwann cells proliferate to form endoneurial Bands of Büngner.
- Regeneration Velocity: Axonal sprouting proceeds across the repair site at an average rate of 1 mm per day (approximately 1 inch per month or 2.5 cm/month). Proximal lesions require significantly longer recovery trajectories than distal injuries.
2. Median Nerve Lesions, Deformities & Orthoses
The median nerve is often termed the 'eye of the hand' due to its critical sensory innervation of the radial digits and motor control over thumb palmar abduction and opposition.
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| MEDIAN NERVE LESION CLINICAL PROFILES |
+-------------------------------------------------+-------------------------------------------------+
| HIGH MEDIAN NERVE LESION (Above Elbow / Forearm)| LOW MEDIAN NERVE LESION (Wrist / Carpal Tunnel) |
+-------------------------------------------------+-------------------------------------------------+
| MOTOR DEFICITS: | MOTOR DEFICITS: |
| • Loss of Forearm Pronation (PT, PQ) | • Loss of Thenar Muscles: |
| • Weak Wrist Flexion & Radial Deviation (FCR) | - Abductor Pollicis Brevis (APB) |
| • Loss of Digit 2 & 3 PIP Flexion (FDS) | - Opponens Pollicis (OP) |
| • Loss of Digit 2 & 3 DIP Flexion (FDP radial) | - Superficial Flexor Pollicis Brevis (FPB) |
| • Loss of Thumb IP Flexion (FPL) | • Loss of Lumbricals 1 & 2 (index/middle MCPs) |
| • Loss of Thumb Palmar Abduction/Opposition | (Forearm pronation, wrist flexion, and long |
| | finger flexion remain INTACT). |
| CLINICAL DEFORMITY / SIGN: | CLINICAL DEFORMITY: |
| • Hand of Benediction (Pope's Blessing): | • Ape Hand Deformity: |
| Visible ONLY when client attempts to make an | Flattening of the thenar eminence; thumb is |
| active fist; digits 2 and 3 remain extended | drawn into the plane of the palm in adduction |
| (paralyzed FDS/FDP), while digits 4 and 5 | and extension by unopposed adductor pollicis |
| flex completely (intact ulnar-innervated FDP).| and extensor pollicis longus. |
| | |
| SENSORY LOSS: | SENSORY LOSS: |
| • Palmar surface of thumb, index, middle, and | • Palmar surface of thumb, index, middle, and |
| radial half of ring finger; dorsal fingertips | radial half of ring finger; dorsal fingertips |
| • Palmar cutaneous branch lost (proximal palm) | • Palmar cutaneous branch SPARED (arises prox.) |
| | |
| ORTHOTIC INTERVENTION: | ORTHOTIC INTERVENTION: |
| • Elbow splint in 90° flexion with forearm in | • C-Bar Splint or Short Thumb Spica (Web-Space |
| neutral; dorsal blocking / wrist cock-up | Maintainer): Positions thumb in palmar |
| with C-bar thumb component. | abduction and opposition; prevents contracture|
+-------------------------------------------------+-------------------------------------------------+
3. Ulnar Nerve Lesions, Diagnostic Signs & Orthoses
The ulnar nerve governs power grip and intrinsic fine motor manipulation through its innervation of the hypothenar muscles, all interossei, the medial two lumbricals, and the adductor pollicis.
Motor & Sensory Presentation
- Motor Loss: Flexor carpi ulnaris (high lesion), flexor digitorum profundus to digits 4 & 5 (high lesion), abductor digiti minimi, flexor digiti minimi brevis, opponens digiti minimi, dorsal interossei (abduction), palmar interossei (adduction), adductor pollicis, deep head of flexor pollicis brevis, and 3rd/4th lumbricals.
- Sensory Loss: Volar and dorsal aspects of the ulnar 1.5 digits (little finger and ulnar half of ring finger) and ulnar border of the palm.
+---------------------------------------------------------------------------------------------------+
| ULNAR NERVE CLINICAL DEFORMITY & PROVOCATIVE SIGNS |
+------------------------------------+--------------------------------------------------------------+
| Clinical Sign / Deformity | Biomechanical Mechanism & Clinical Presentation |
+------------------------------------+--------------------------------------------------------------+
| **Claw Hand (Intrinsic Minus Hand)**| • Hyperextension of MCP joints (unopposed EDC) combined with |
| | flexion of PIP and DIP joints (loss of lumbricals 3 & 4). |
| | • Primarily involves digits 4 and 5. |
+------------------------------------+--------------------------------------------------------------+
| **The Ulnar Paradox** | • The claw deformity is **MORE SEVERE IN LOW LESIONS** than |
| | high lesions! In high lesions, the FDP to digits 4 & 5 is |
| | denervated, reducing DIP flexion force. In low lesions, FDP|
| | is intact and pulls denervated digits into acute flexion. |
+------------------------------------+--------------------------------------------------------------+
| **Froment's Sign** | • During lateral/key pinch (holding paper between thumb and |
| | index finger), the client exhibits **hyperflexion of the |
| | thumb IP joint** via the median-innervated *flexor pollicis|
| | longus* (FPL) to compensate for paralyzed adductor pollicis|
+------------------------------------+--------------------------------------------------------------+
| **Jeanne's Sign** | • Simultaneous hyperextension of the thumb MCP joint during |
| | pinch alongside IP hyperflexion (extreme instability). |
+------------------------------------+--------------------------------------------------------------+
| **Wartenberg's Sign** | • The **little finger rests in persistent abduction** away |
| | from the 4th digit due to paralyzed 3rd palmar interosseus |
| | and unopposed extensor digiti minimi (EDM, radial nerve). |
+------------------------------------+--------------------------------------------------------------+
Orthotic Management for Ulnar Nerve Injury
- MCP Flexion Blocking Splint (Anti-Claw / Figure-8 / Lumbrical Bar Splint): Blocks the 4th and 5th MCP joints in 30° to 45° of flexion. By preventing MCP hyperextension, the intact extensor digitorum communis (EDC) tendon excursion is redirected distally to fully extend the PIP and DIP joints, restoring functional open grasp.
4. Radial Nerve Lesions & Functional Restoration
The radial nerve innervates all dorsal extensor musculature of the upper extremity, governing elbow extension, forearm supination, wrist extension, digit MCP extension, and thumb extension/abduction.
Clinical Presentation across Lesion Levels
- High Radial Nerve Lesion (Spiral Groove / Mid-Humeral Shaft Fracture / 'Saturday Night Palsy'):
- Motor Deficits: Loss of extensor carpi radialis longus/brevis (ECRL/ECRB), extensor carpi ulnaris (ECU), extensor digitorum communis (EDC), extensor indicis (EIP), extensor digiti minimi (EDM), extensor pollicis longus/brevis (EPL/EPB), abductor pollicis longus (APL), brachioradialis, and supinator.
- Classic Deformity: Wrist Drop (inability to extend wrist, MCP joints, or thumb). Grip strength is severely diminished secondary to loss of active wrist extension tenodesis stabilization.
- Sensory Loss: Dorsal aspect of the first web space, dorsal surface of the thumb, index, middle, and radial ring fingers proximal to the DIP joints.
- Low Radial Nerve Lesion (Posterior Interosseous Nerve / PIN Syndrome):
- Motor Deficits: Motor branch entrapment at Arcade of Frohse. Paralyzes EDC, EDM, ECU, EPL, EPB, APL, and EIP. Wrist extension is preserved with radial deviation because ECRL (innervated proximally) is intact.
- Sensory Deficits: Pure motor deficit; sensation in the dorsal first web space is completely intact (superficial radial nerve spared).
Orthotic Intervention for Radial Nerve Palsy
- Dynamic Wrist and MCP Extension Splint (Dynamic Radial Nerve Splint / Tenodesis Assist):
- Supports the wrist in 20° to 30° of extension.
- Employs dynamic elastic outriggers or slings that passively maintain the MCP joints and thumb in extension.
- Biomechanical Function: Allows the client to actively flex fingers against elastic traction to grasp objects, and utilizes dynamic elastic recoil to open fingers and release objects.
5. Brachial Plexus Injuries
Brachial plexus injuries result from traction, compression, or avulsion of spinal nerve roots C5 through T1.
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| BRACHIAL PLEXUS INJURY CLINICAL COMPARISON |
+------------------------------------+--------------------------------------------------------------+
| ERB-DUCHENNE PALSY (Upper Trunk) | KLUMPKE'S PALSY (Lower Trunk) |
+------------------------------------+--------------------------------------------------------------+
| • **Involvement:** C5–C6 roots | • **Involvement:** C8–T1 roots |
| • **Mechanism:** Traction tearing | • **Mechanism:** Upward traction from hyper-abduction |
| during breech birth or shoulder | (catching tree branch while falling; difficult delivery). |
| depression in motorcycle crashes.| • **Paralyzed Musculature:** Intrinsic hand muscles (all |
| • **Paralyzed Musculature:** | interossei, thenar/hypothenar, lumbricals), wrist flexors |
| Deltoid, supraspinatus, infra- | (FCU), and long finger flexors (FDP/FDS). |
| spinatus, biceps, brachialis, | • **Classic Clinical Posture:** **Total Claw Hand** (severe |
| brachioradialis, and supinator. | intrinsic minus involving all digits) and flattened hand. |
| • **Classic Clinical Posture:** | • **Associated Autonomic Sign:** **Horner's Syndrome** |
| **'Waiter's Tip' Position:** | (ptosis, miosis, anhidrosis, enophthalmos) due to damage to|
| Arm rests in shoulder adduction, | the sympathetic chain at T1. |
| internal rotation, elbow | • **Sensory Loss:** Medial aspect of arm, forearm, and ulnar|
| extension, forearm pronation, and| border of the hand. |
| wrist flexion. | • **OT Intervention:** Hand-based resting splint to prevent |
| • **OT Intervention:** | clawing/contractures; passive ROM; adaptive grips; |
| Flail arm splint / shoulder | sensory compensation and skin inspection. |
| abduction-external rotation | |
| orthosis; PROM to prevent adduc- | |
| tion/internal rotation contract. | |
+------------------------------------+--------------------------------------------------------------+
6. Sensory Evaluation & Re-Education Protocols
Sensory re-education facilitates the neural reorganization of primary somatosensory cortex maps following peripheral nerve regeneration or surgical repair.
1. Sensory Evaluation Hierarchy
- Semmes-Weinstein Monofilaments: Quantifies threshold touch sensibility (Green/2.83 = Normal light touch; Blue/3.61 = Diminished light touch; Purple/4.31 = Diminished protective sensation; Red/4.56 = Loss of protective sensation; Red/6.65 = Untestable/Deep pressure only).
- Static & Moving Two-Point Discrimination: Assesses functional tactile innervation density. Normal static 2PD is < 6 mm; normal moving 2PD is 2 to 3 mm.
2. Dellon's Sensory Retraining Protocol
Sensory re-education cannot begin until the client demonstrates baseline neural regeneration and perception of protective sensation.
+---------------------------------------------------------------------------------------------------+
| PHASED SENSORY RE-EDUCATION FRAMEWORK |
+-------------------------------------------------+-------------------------------------------------+
| PHASE 1: EARLY SENSORY RETRAINING | PHASE 2: LATE SENSORY RETRAINING |
+-------------------------------------------------+-------------------------------------------------+
| • **Inclusion Threshold:** Initiated when | • **Inclusion Threshold:** Initiated when |
| client perceives moving touch and **30 Hz | client demonstrates constant touch and |
| vibration** (tuning fork), but lacks constant | **256 Hz vibration** perception; moving 2PD |
| touch. | is returning. |
| • **Technique Sequence:** | • **Technique Sequence:** |
| 1. Stroke skin with pencil eraser / texture | 1. Tactile Localization: Client identifies |
| while client watches (Visual + Tactile). | exact stimulus point with eyes closed, then|
| 2. Repeat identical stroke with eyes closed. | opens eyes to verify. |
| 3. Open eyes and confirm tactile feedback. | 2. Stereognosis & Object Discrimination: |
| • Focus: Moving touch before constant touch! | Graded identification of common objects |
| | (coins, keys, cotton, sandpaper grades) |
| | without visual feedback. |
+-------------------------------------------------+-------------------------------------------------+
3. Protective Sensibility Education
For clients with loss of protective sensation (Semmes-Weinstein > 4.56):
- Visual compensation: Inspect skin daily for blistering, redness, and lacerations.
- Thermal protection: Set household hot water heaters to
< 120°F(49°C); use bath thermometers; wear insulated oven mitts. - Mechanical protection: Build up tool handles to distribute pressure over larger surface areas; wear protective leather gloves during gardening or manual labor.
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Test Your Knowledge
A client is referred to occupational therapy following a severe laceration at the volar wrist crease. Evaluation reveals profound muscle atrophy of the thenar eminence, complete inability to actively abduct or oppose the thumb away from the palm, and absent light touch sensation on the palmar surfaces of the thumb, index, middle, and radial half of the ring finger. What clinical deformity is present, and which orthosis is MOST APPROPRIATE?
A
B
C
D
Test Your Knowledge
During a clinical hand assessment, an occupational therapist instructs a client to hold a flat sheet of paper between the thumb and index finger in a lateral key pinch while the therapist pulls the paper away. The therapist observes marked hyperflexion of the client's thumb interphalangeal joint to hold onto the paper. What is this clinical sign, and which nerve impairment does it indicate?
A
B
C
D
Test Your Knowledge
A client sustains a mid-shaft humeral fracture resulting in high radial nerve palsy. Physical examination reveals complete inability to extend the wrist, metacarpophalangeal joints, and thumb, with loss of sensation over the dorsal first web space. Which occupational therapy orthosis is MOST EFFECTIVE for restoring functional hand use during daily occupations?
A
B
C
D