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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.
