Lesions of radial nerves

Radial nerve palsy produces an inability to extend the metacarpophalangeal joints, owing to paralysis of the extensor digitorum communis muscle. However, the lumbrical and interossei muscles, which are served by the median and ulnar nerves and insert into the dorsal expansions (extensor hoods) of the proximal phalanges, are able simultaneously to flex the metacarpophalangeal joints and to extend the interphalangeal joints [thus not answer d ]. Also, abduction of the digits, a function of the dorsal interossei, and adduction, a function of the palmar interossei, are both mediated by the ulnar nerve and, therefore, unaffected [thus not answers a and b].

Nerve supply to the triceps is proximal to the mid shaft level

Radial nerve REF: Snell’s anatomy 7^th ed p. 484

Radial nerve injury is seen in:

• Fracture shaft of humerus
• Saturday night palsy
• Injection palsy

Features of radial nerve injury:

• Sensory loss over area supplied by posterior cutaneous nerve of forearm.
• Wrist, thumb and finger extension is lost.

Low radial nerve palsy occurs when the radial nerve is injured at the level of elbow, so that the muscles supplied by the radial nerve in the distal arm (Brachioradialis and Extensor Carpi radialis longus) are spared.

Ref: Essential Orthopedics By J Maheswari, 3nd Edition, Page 53; Apley’s System of Orthopaedics and Fractures By Louis Solomon, 9th Edition, Chapter 11, Page 282

Radial nerve palsy associated with humeral shaft fractures is the most common nerve lesion complicating fractures of long bones. Radial nerve injury is commonly associated with:

• Fracture shaft of humerus
• Saturday night palsy
• Injection palsy

Long head of triceps is supplied by radial nerve before entering the radial groove. Medial head of triceps is supplied by the radial nerve before entering and while in the spiral groove. Lateral head of triceps is innervated by the radial nerve while in the groove.

Options 1 (true)
The cutaneous branch of the radial nerve supply the skin over anatomical snuff box, as such radial nerve injury causes anaesthesia over anatomical snuff box.

A i.e. Radial nerve injury cause anaesthesia over anatomical snuff box; C i.e. Ulnar nerve injury cause claw hand; B i.e. Index finger anesthesia is caused by median nerve injury 

C i.e. Leaves extension at elbow joint intact

Triceps, anconeus are supplied by radial nerve above the level of spiral groove; so these are spared in injuries of radial n. at & below spiral groove thus leaving elbow extension intact Q

A i.e. Loss of nerve supply to brachoradialis

– Mnemonic – “TAB Long radial muscle” i.e. Triceps, Anconeus, Brachialis and Brachioradialis & Extensor carpi radialis longus muscles are spared in low radial nerve lesions (i.e. lesions below the level of elbow.)

– Lateral & posterior cutaneous nerves of arm and posterior cutaneous nerve of forearm are also spared in low radial nerve lesions.

A i.e. Extensor carpi radialis longus 

Extensor carpi radialis longus muscle is supplied by main trunk of radial nerve above the level of elbow joint; whereas extensor carpi radialis brevis, finger extensors (extensor indics, extensor digitorum, extensor digits minimi) are supplied by its posterior interosseous branch and sensation on dorsum of hand by superficial radial branch below the level of elbow joint.

A i.e. Opposition; C i.e. Adduction; B i.e. Flexion 

Posterior interosseous branch of radial nerve supplies extensor pollicis longus & brevis (EPL & EPB) and abductor pollicis longus (AbPL)Q (3) thumb muscles. So radial nerve injury weakens (affects) abduction & extension movements of thumb and spares flexion, adduction & oppositionQ

Movements of Thumb

* PIN = posterior interosseous nerve (br of radial nerve); M= Median & U = Ulnar nerve

* Flexor pollicis brevis has dual nerve supply i.e. superficial head from median and deep hed from ulnar nerve.

Ans. is ‘c’ i.e., Radial

o As with all intramuscular preparations, terramycin (oxytetracycline) intramuscular solution should be injected well within the body of a relatively large muscle.

o In infants and small children the periphery of the upper outer quadrant of the gluteal region should be used only when necessary, such as in burn patients, in order to minimize the possibility of damage to the sciatic nerve.

o The deltoid area should be used only if well developed such as in certain adults and older children, and then only with caution to avoid radial nerve injury.

Ans. B: Radial Nerve

Radial nerve injury occurs in up to 18% of cases of fracture shaft humerus.

It is most common with middle third fractures, although best known for its association with Holstein-Lewis type distal third fracture, which may entrap or lacerate the nerve as it passes through the intermuscular septum.

Most injuries are neurapraxias or axonotmesis; function will return within 3 to 4 months; laceration is more common in open fractures or gunshot injuries.

Delayed surgical exploration should be done after 3 to 4 months if there is no evidence of recovery by electromyography or nerve conduction velocity studies.

Ans: B i.e. Radial nerve

Nerve injury & splints

• Ulnar nerve palsy (lumbricals paralysis) is managed by knuckle bender splint
• Radial nerve palsy (extensors of wrist & metcarpophaingeal joint paralyzed) is managed by cock-up splint
• Axillary nerve injuries (deltoid paralysis) is managed by aeroplane splint Common peroneal nerve injury (extensors & evertors of the foot paralyzed) is managed by foot drop splint

Ans. is ‘a’ i.e., Radial nerve palsy

Complications of humerus shaft fracture

1. Nerve injury : – Radial nerve is the most commonly injured nerve in fracture shaft humerus. It is particularly common in oblique fractures at the junction of middle and distal third of the bone (Holstein- Lews fracture).
2. Vascular injury : – Brachial artery damage.
3. Delayed union or non-union : – Delayed union or non-union may occur, especially in transverse fracture of the midshaft. The cause of non-union is distraction at fracture site due to gravity and weight of plaster.
4. Joint stiffness : – Shoulder & elbow stiffness.

Clinical features of radial nerve palsy

• Clinical features depend upon the site of lesion.

1) If lesion is high

• Wrist drop, thumb drop and finger drop.
• Inability to extend elbow, wrist, thumb & fingers (MP joint)
• Patient can extend interphalangeal joints due to action of lumbricals and interossei.
• Sensory loss over posterior surface of arm & forearm and lower lateral half of forearm.

2) If lesion is low

a) Type I

• Wrist drop, thumb drop and finger drop.
• Elbow extension is preserved.
• Sensory loss over the dorsum of first web space.

b) Type II

• Thumb drop and finger drop
• Elbow and wrist extension is preserved
• Sensory loss over the dorsum of first web space.