Which proximal carpal bone lies directly lateral to the lunate?

Question

BlackTom AI · Accepted Answer

The scaphoid lies lateral (radial) to the lunate in the proximal carpal row, so the correct choice is c. scaphoid.

1. Relevant knowledge points and concepts
- The carpal bones are arranged in two transverse rows: proximal (radial to ulnar) and distal.  
- In the proximal row, from lateral (radial, toward the thumb) to medial (ulnar, toward the little finger), the typical sequence is: scaphoid → lunate → triquetrum (with pisiform as a sesamoid bone on the palmar surface of the triquetrum).  
- Trapezium and trapezoid are part of the distal carpal row, not the proximal row.

2. Step-by-step reasoning
- Identify the target: the lunate is a central proximal carpal bone.  
- Determine what lies immediately lateral (on the radial/thumb side) of the lunate: according to the standard arrangement, scaphoid is directly lateral to the lunate.  
- Verify that the scaphoid articulates with the radius laterally and with the lunate medially, confirming its lateral adjacency.

3. Intermediate anatomical relationships (explicit)
- Proximal row, lateral → medial: scaphoid (articulates with radius and lunate) → lunate → triquetrum.  
- Pisiform is a small sesamoid on the palmar surface of the triquetrum (more medial/volar), not lateral to the lunate.  
- Trapezium and trapezoid are distal to the scaphoid and not in the proximal row.

4. Why the correct answer is correct
- The scaphoid’s position on the radial side of the wrist and its articulation with the lunate places it directly lateral to the lunate, matching the question’s requirement.

5. Why other options are incorrect
- a. Trapezium: distal row bone lateral to scaphoid/trapezoid, not in the proximal row.  
- b. Trapezoid: distal row bone, medial to trapezium, not adjacent lateral to the lunate.  
- d. Pisiform: sesamoid on the palmar surface of the triquetrum, medial/volar relative to lunate, not lateral.  
- e. Triquetrum: lies medial to the lunate, not lateral.

6. Conclusion
This confirms the correct answer is c. scaphoid, which matches the provided answer.

Which proximal carpal bone lies directly lateral to the lunate?单项选择题

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