Upper limb and brachial plexus: intrinsic muscles of the hand: practice question

A Anatomy question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Anatomy · Upper limb and brachial plexus: intrinsic muscles of the hand

Sample item

A man has an ulnar nerve laceration at the wrist and develops a claw deformity of the ring and little fingers. Which normal action, performed by the medial two lumbricals and interossei, is lost and allows this deformity?

AFlexion at the distal interphalangeal jointsBFlexion at the proximal interphalangeal jointsCFlexion at the metacarpophalangeal joints with extension at the interphalangeal jointsDExtension at the metacarpophalangeal joints

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Flexion at the metacarpophalangeal joints with extension at the interphalangeal joints

The lumbricals arise from the tendons of flexor digitorum profundus and insert into the extensor expansion, so they flex the metacarpophalangeal joints and extend the interphalangeal joints. With the medial two paralysed, unopposed extensor digitorum hyperextends the metacarpophalangeal joints while profundus and superficialis flex the interphalangeal joints. The result is the ulnar claw hand.

Option by option

A. Flexion at the distal interphalangeal joints
Distal interphalangeal flexion is by profundus, which is intact when the lesion is at the wrist.
B. Flexion at the proximal interphalangeal joints
Proximal interphalangeal flexion is by superficialis, which is not supplied by the ulnar nerve at the wrist.
C. Flexion at the metacarpophalangeal joints with extension at the interphalangeal joints (correct)
Correct. Loss of this combined action leaves the extensor and long flexors unopposed.
D. Extension at the metacarpophalangeal joints
Metacarpophalangeal extension is by extensor digitorum, which is intact and in fact overacts.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Flexion at the metacarpophalangeal joints with extension at the interphalangeal joints. The lumbricals arise from the tendons of flexor digitorum profundus and insert into the extensor expansion, so they flex the metacarpophalangeal joints and extend the interphalangeal joints.

Why is "Flexion at the distal interphalangeal joints" not the answer?

Distal interphalangeal flexion is by profundus, which is intact when the lesion is at the wrist.

Why is "Flexion at the proximal interphalangeal joints" not the answer?

Proximal interphalangeal flexion is by superficialis, which is not supplied by the ulnar nerve at the wrist.

Why is "Extension at the metacarpophalangeal joints" not the answer?

Metacarpophalangeal extension is by extensor digitorum, which is intact and in fact overacts.

What concept does this question test?

It tests Upper limb and brachial plexus: intrinsic muscles of the hand in Anatomy. With the medial two paralysed, unopposed extensor digitorum hyperextends the metacarpophalangeal joints while profundus and superficialis flex the interphalangeal joints. The result is the ulnar claw hand.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Upper limb and brachial plexus: intrinsic muscles of the hand?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.