Question
A road traffic accident patient has presented to you with features of a nerve injury involving right upper limb.On examination,the patient is able to carry out flexion at metacarpo-phalangeal joint and extension at interphalangeal joint.The most likely nerve involved is ?
| A. |
Median nerve
|
| B. |
Anterior interosseous nerve
|
| C. |
Ulnar nerve
|
| D. |
Radial nerve
|
Show Answer
|
Correct Answer » D
Explanation
|
|
- Flexion at the MCP joints and extension at the IP joints is the characteristic action of the lumbricals (assisted by the interossei through the extensor expansion).
- Since the patient is able to perform this movement, the median and ulnar nerves, which supply the lumbricals and interossei, are functioning.
- Therefore, the intrinsic muscles of the hand are intact.
- Among the given options, the nerve most likely to be injured while preserving this function is the radial nerve.
Why Other Options are Incorrect
A. Median nerve
- Supplies the lateral two lumbricals.
- Injury weakens flexion of the MCP joints and extension of the IP joints of the index and middle fingers.
- These movements would be impaired rather than preserved.
B. Anterior interosseous nerve
- Motor branch of the median nerve.
- Supplies:
- Flexor pollicis longus.
- Lateral half of flexor digitorum profundus.
- Pronator quadratus.
- Causes inability to make the “OK” sign.
- Does not affect lumbrical function.
C. Ulnar nerve
- Supplies the medial two lumbricals and all interossei.
- Injury impairs MCP flexion and IP extension of the ring and little fingers.
- Produces an ulnar claw hand.
