Ulnar nerve injury

Question 1

Mechanism of injury of ulnar nerve injury

Answer 1

Cubital tunnel syndrome
Fracture of hammate bone

Question 2

Clinical sign of ulnar nerve injury: claw hand

Answer 2

RESTING hand position: Ulnar claw hand
Hyperextension of MCPJ of 4-5th finger
Hyperflexion of IPJ of 4-5th finger

Question 3

Tx of ulnar nerve injury

Answer 3

MCPJ flexion block splint

Question 4

Innervation of ulnar nerve

Answer 4

flexor carpi ulnaris (flex + adduct)
medial half of flexor digitorum profundus (flex 4-5th DIPJ)
medial 2 lumbricals
palmar and dorsal interossei muscles (PAD, DAB)
Hypothenar muscles (flexor digiti minimi brevis, abductor digiti minimi, opponens digiti minimi)
Adductor pollicis

Question 5

Clinical sign of ulnar nerve injury: Wartenberg sign

Answer 5

ACTIVE test: ask the patient to adduct fingers from a fan-shape position
–> patient unable to adduct the 5th digit (due to the injured palmar interossei)

Question 6

other clinical sign of ulnar nerve injury

Answer 6

• wasting of hypothenar muscles
• gutting/ wasting of dorsal side of hand

Question 7

Clincal sign of ulnar nerve injury: Froment sign

Answer 7

ACTIVE test: ask the patient to keep a pincer grip position and hold a piece of paper in place
failed (due to injured adductor pollicis muscle)
1. paper slip out
2. make an “OK” sign