Ulnar Nerve Injury
ULNAR NERVE INJURY
- Ulnar nerve injury may be high or low.
1) High ulnar nerve palsy
- High ulnar nerve palsy is caused by injury proximal to the elbow.
- All the muscles supplied by ulnar nerve are paralysed & there is atrophy of hypothenar eminence.
- Sensory loss in the medial 1/3rd of the palm & medial one & half of fingers.
2) Low ulnar nerve palsy
- Injury in distal-third of forearm or at wrist.
- Flexor digitorum profundus & flexor carpi ulnaris are spared.
- Muscles of hand are paralysed:
Hypothenar muscles:
- Palmar brevis
- Abductor digiti minimi
- Flexor digiti minimi
- Opponens digit minimi
- Adductor pollicis
- All interossei (Palmar & Dorsal) & medial two lumbricals (3rd & 4th).
- Sensory loss is same as in high ulnar nerve palsy.
Muscles examination in ulnar nerve injury
- Individual muscles which can be examined in ulnar nerve palsy are:-
1) Flexor carpi ulnaris:
- The patient is asked to palmar flex the wrist against gravity.
- In doing so, the hand deviates towards the radial side.
- The tendon of flexor caroi ulnaris just above the pisiform, does not stand out.
- On performing the same test against resistance, the tendon cannot be felt.
2) Abductor digiti minimi:
- The patient is asked to abduct the little finger against resistance while keeping the hand flat on the table (in order to avoid action of flexors of the finger).
3) Interossei:
- Palmar interossei do addduction (PAD), the dorsal interossei do abduction (DAB) of the fingers at metacarpophalangeal joints.
These can be tested as follows:-
1) Egawa’s Test:
- This is for dorsal interossei (abductors) of the middle finger.
- With the hand kept flat on a table palmar surface down, the patient is asked to move his middle finger sideways.
- This is for palmar interossei (adductors) of the fingers.
- In this test, the examiner inserts a card b/w two extended fingers & the patient is ssked to hold it as tightly as possible while the examiner tries to pull the card out.
- The power of adductors can thus be judged.
- In case of weak palmar interossei, it is easy to pull out the card.
- First dorsal interosseous muscle can be separately examinated by asking the patient to abduct the index finger against resistance.
3) The lumbricals:
- These are mainly responsible for flexion at the metacarpo-phalangeal joints but their isolated action cannot be tested.
4) Adductor pollicis:
- The patient is asked to grasp a book b/w the thumb & index finger.
- Normally, a person will grasp the book firmly with thumb extended, taking full advantage of the adductor pollicis & the first dorsal interosseous muscles.
- If the ulnar nerve is injured the adductor policis will be paralysed & the patient will hold the book by using the flexor pollicis longus (supplied by median nerve) in place of the inter-phalangeal joint of the thumb.
- This is because more pronounced if the examiner tries to pull the book out while the patient tries to hold it.
- This sign is known as ‘Froment’s sign’ or the ‘book test’.
6) Wartenberg’s sign:
- Inability to adduct the small finger in against the ring finger due to weakness of palmar interosseous muscles.
Exam Question
- High ulnar nerve palsy is caused by injury proximal to the elbow..
- Tardy ulnar nerve palsy is seen in Lateral condyle # humerus.
- Knuckle bender splint is used for Ulnar Nerve Palsy.
- Claw hand is caused by lesion involving Ulnar nerve.
- Cubital tunnel syndrome involves Ulnar nerve.
- In Hansen’s disease, the nerve commonly affected at elbow is Ulnar nerve.
- Most common nerve injured in fracture of medial epicondyle of humerus is Ulnar nerve.
- Inability to adduct the thumb is due to the injury of Ulnar nerve.
- Froment test is positive in lesion of Ulnar nerve.
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