MSK 22 - Upper Limb Nerve Injuries

Question 1

Can a patient still extend their elbow if the radial nerve is damaged in a mid-shaft humeral fracture?

What position will the patients wrist + fingers be in when the wrist is pronated?

What will the distribution of sensory impairment be?

Answer 1

Yes - the nerve supply to the long and lateral heads of triceps is given off before the radial nerve enters the spiral groove of the humerus. Nerve supply to medial head is given off in spiral groove but is generally proximal to the fracture and is unaffected. Aconeus is paralysed (only a weak extensor).

Flexed in pronation - as there will be paralysis of the brachioradialis and all extensor muscles in wrist and fingers, resulting in “wrist drop” and inability to extend fingers.

Paraesthesia in distribution of superficial branch of radial nerve (thumb, index, middle and medial side of ring) on dorsal surface of hand.

Question 2

What is the result of a high median nerve injury due a supracondylar fracture of the humerus?
What deformities result?
What could the sensory loss be?

Answer 2

• Paralysis of pronator teres, flexor carpi radialis, palmaris longus + flexor digitorum superficialis (common flexor origin from medial epicondyle)
• Both pronators in forearm weak, flexors of wrist apart from flexor carpi ulnaris paralysed
• Forearm will be supinated, with weak flexion of the wrist.
• Hand of benediction (when asked to make a fist), unable to flex thumb, index and middle.
• Ape hand deformity w/thenar waisting.
• Paraesthesia on median nerve distribution on palmar side, tips of index and middle finger on dorsal side.

Question 3

What is the result of a low median nerve injury? (due to penetration from broken glass or compression in carpal tunnel)
What deformity results?

Answer 3

• LOAF muscles only paralysed

- Ape hand deformity (flattened thenar eminence + thumb adducted and externally rotated)

Question 4

What is the result of a low ulnar nerve injury? (due to wrist injury)

What deformity results?

What will the sensory loss be?

Answer 4

• Hypothenar eminence muscles are all paralysed/impaired
• (adductor pollicis, deep head of flexor pollicis brevis, interossei + lumbricals of ring and little fingers)
• Claw hand, little and ring fingers are clawed (hyperextension at MCPJ but flexed at both IPJ’s)
• Little and lateral side of ring finger on palmar surface, surface of distal phalanges only on dorsal side.

Question 5

What is the result of a high ulnar nerve lesion? (by a medial epicondylar fracture or compression in cubital tunnel)

Answer 5

• Same paralysis as low ulnar nerve injury (hypothenar eminence muscles) + paralysis of flexor carpi ulnaris
• Loss of sensation in the lateral side of ring and whole little finger (same on both palmar and dorsal surfaces)
• Clawing is seen but less pronounced than low ulnar nerve lesions (as flexor digitorum profundus is paralysed so no flexion at DIPJ on ring and little fingers) - this is known as the ulnar paradox.