Scaphoid
From Ganfyd
ΕΤΥΜΟΛΟΓΙΑ
Greek, 'boat-shaped'The scaphoid (navicular of the hand) is one of the eight carpal bones found in the hand. It forms the most lateral part of the proximal row of carpal bones, and is the largest carpal bone in the proximal row. The scaphoid articulates with the radius proximally, the capitate, trapezium and trapezoid distally, and the lunate medially.
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Surface Anatomy
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| Search for Scaphoid in Gray's. | |
The scaphoid can be felt at the base of the thenar eminence, particularly on extension of the wrist. It is also felt within the anatomical snuff box, and this area may be notably tender in a fracture of the scaphoid.
Shape
The scaphoid has a long axis which is distal, lateral and slightly palmar. It has a number of surfaces - the palmar surface and rough dorsal surface, the narrow and rough lateral surface, the convex radial surface, the flat semilunar medial lunate surface, the large concave distal capitate surface, and the large distal surface for trapezoid and trapezium. A round tubercle is apparent on the distolateral part of the palmar surface, whilst the nutrient foramen pierces the dorsal surface and is often limited to the distal half.
Attachments
- The flexor retinaculum attaches to the tubercle
- Abductor pollicis brevis attaches to the tubercle
- The radial collateral ligament attaches to the lateral surface
Joints
- The scaphoid articulates with the radius and the triangular articular disc at the wrist
- The scaphoid articulates with the capitate, trapezoid and trapezium at the midcarpal joint
- The scaphoid is held adjacent to the lunate in the proximal row of carpal bones by several intercarpal ligaments.
Direct Relations
- The tendon of flexor carpi radialis crosses the dorsal surface
Ossification
The scaphoid begins to ossify in the fourth or fifth year.
Variations
There is no nutrient foramen in the proximal part of the scaphoid in 13% of people.
An os centrale may occur between scaphoid, trapezoid and capitate; this usually fuses with the scaphoid during the second prenatal month.
Clinical Relevance
- May be fractured
- Fracture across the proximal scaphoid or 'waist' may fail to unite or lead to avascular necrosis.
