CARPUS
- made of 8 carpal bones.
- arranged in two rows.
⭐ Proximal row is convex proximally, and concave distally.
⭐ Distal row is convex proximally and flat distally.
PROXIMAL ROW:
i. Scaphoid ⭐ – Boat-shaped and has a tubercle on its lateral side.
ii. Lunate ⭐ – Half-moon-shaped or crescentic.
iii. Triquetral ⭐ – Pyramidal and has an isolated oval facet on the distal part of the palmar surface.
iv. Pisiform ⭐ – Pea-shaped and has only one oval facet on the proximal part of its dorsal surface.
DISTAL ROW:
i. Trapezium ⭐ – Quadrangular and has a crest and a groove anteriorly. It has a Sellar (concavo-convex) articular surface distally.
ii. Trapezoid ⭐ – Resembles the shoe of a baby.
iii. Capitate ⭐ – The largest carpal bone, with a rounded head.
iv. Hamate ⭐ – Wedge-shaped with a hook near its base.
Each bone has 6 SURFACES:
• Palmar and dorsal surfaces are non-articular, except for the triquetral and pisiform.
• Lateral surfaces of the two lateral bones (scaphoid and trapezium) are non-articular.
• Medial surfaces of the three medial bones (triquetral, pisiform, and hamate) are non-articular.
• Dorsal non-articular surface is always larger than the palmar non-articular surface, except for the lunate, in which the palmar surface is larger than the dorsal.
1️⃣ Scaphoid ⭐ – Tubercle directed laterally, forward, and downwards.
2️⃣ Lunate ⭐ – Small semilunar articular surface for the scaphoid is on the lateral side and the quadrilateral articular surface for the triquetral is on the medial side.
3️⃣ Triquetral ⭐ – Oval facet for the pisiform lies on the distal part of the palmar surface.
4️⃣ Pisiform ⭐ – Oval facet for the triquetral lies on the proximal part of the dorsal surface and lateral surface is grooved by the ulnar nerve.
5️⃣ Trapezium ⭐ – Palmar surface has a vertical groove for the tendon of the flexor carpi radialis and is limited laterally by the crest of the trapezium.
6️⃣ Trapezoid ⭐ – Distal articular surface is larger than the proximal.
7️⃣ Capitate ⭐ – Dorsomedial angle is the distal-most projection from the body of the capitate and has a small facet for the 4th metacarpal bone.
8️⃣ Hamate ⭐ – Hook projects from the distal part of the palmar surface and is directed laterally.
