Question
A patient with a nerve injury was asked to make an “O” with their index finger and thumb but was unable to do so. Which muscle is most likely involved?
| A. |
Opponens pollicis |
| B. |
Abductor pollicis brevis |
| C. |
Flexor pollicis brevis |
| D. |
Palmar interossei |
|
Correct Answer � A Explanation |
 |
– Opponens pollicis is key for thumb opposition, allowing the thumb to move medially across the palm. This movement, vital for forming an “O” shape, is innervated by the median nerve. Damage here, such as in carpal tunnel syndrome, can impair opposition.
Incorrect Options:
– Abductor pollicis brevis: Abducts the thumb away from the palm but doesn’t perform true opposition.
– Flexor pollicis brevis: Primarily flexes the thumb; plays a minor role in opposition.
– Palmar interossei: Adducts fingers, not involved in thumb movement; innervated by the ulnar nerve.