Question
A 17-year-old male presents to the hospital following a right elbow dislocation. The patient is initially neurovascularly intact. However, after reduction, the patient complains of tingling in his hands. What motor deficit might be seen in this patient?
| A. |
Inability to flex and ulnar deviate wrist
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| B. |
Inability to abduct fingers
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| C. |
Inability to extend fingers
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| D. |
Inability to flex thumb at interphalangeal joint
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Show Answer
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Correct Answer � B
Explanation
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Answer B) Inability to abduct fingers
The most commonly reported nerve injury in elbow dislocations is the ulnar nerve.
Damage at the Elbow
- Mechanism of injury: Trauma at the level of the medial epicondyle (e.g. isolated medial epicondyle fracture, supracondylar fracture). It can also be compressed in the cubital tunnel.
Motor functions:
- All the muscles innervated by the ulnar nerve are affected.
- Flexion of the wrist can still occur, but is accompanied by abduction (due to paralysis of flexor carpi ulnaris and medial half of flexor digitorum profundus).
- Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei).
- Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles).
- Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).
Sensory functions: All sensory branches are affected, so there will be a loss of sensation over the areas that the ulnar nerve innervates.
Characteristic signs: Patient cannot grip paper placed between fingers, positive Froment’s sign, wasting of hypothenar eminence.
Damage at the Wrist
Mechanism of injury: Lacerations to the anterior wrist.
Motor functions:
- Only the intrinsic muscles of the hand are affected.
- Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei).
- Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles).
- Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).
Sensory functions: The palmar branch and superficial branch are usually severed, but the dorsal branch is unaffected. This results in sensory loss over the palmar side of medial one and a half fingers only.
Characteristic signs: Patient cannot grip paper placed between fingers, positive Froment’s sign, wasting of hypothenar eminence.
