Topic Overview

Clinical Anatomy of Carpal Bones

Carpal Bones (Proximal → Distal, Lateral → Medial)

Scaphoid, Lunate, Triquetral, Pisiform, Trapezium, Trapezoid, Capitate, Hamate

Mnemonics

1. “Some Lovers Try Positions That They Can’t Handle”

   • Scaphoid

   • Lunate

   • Triquetral

   • Pisiform

   • TrapeziUM

   • Trapezoid

   • Capitate

   • Hamate

2. “She Looks Too Pretty; Try To Catch Her”

   • S → Scaphoid

   • L → Lunate

   • T → Triquetral

   • P → Pisiform

   • T → Trapezium

   • T → Trapezoid

   • C → Capitate

   • H → Hamate

3. For proximal vs distal rows:

   • Proximal (SLTP) → “Some Lovers Try Positions”

   • Distal (TTCH) → “That They Can’t Handle”

• Scaphoid

  • Most commonly fractured carpal bone.

  • Fracture usually at the waist.

  • Blood supply enters distally → proximal fragment prone to avascular necrosis.

  • Pain and tenderness in the anatomical snuffbox.

• Lunate

  • Most commonly dislocated carpal bone.

  • May compress median nerve in carpal tunnel → produces symptoms similar to carpal tunnel syndrome.

• Pisiform

  • Sesamoid bone within tendon of flexor carpi ulnaris.

  • Occasionally mistaken for fracture on X-ray.

• Capitate

  • Largest carpal bone.

  • Rarely fractured, but forms important central pivot of carpal movement.

• Hamate

  • Hook (hamulus) may fracture.

  • Fracture may injure ulnar nerve and artery in Guyon’s canal → sensory and motor deficits in hand.

• Carpal Instability

  • Results from ligamentous injury between carpal bones.

  • Common cause of chronic wrist pain.

• Congenital Variations

  • Carpal coalition → fusion of carpal bones (e.g., lunate and triquetral).

  • Often asymptomatic, but may cause restricted movement.

Ossification of Carpal Bones

• Each carpal bone ossifies from a single center.

• No carpal bone is ossified at birth.

• Sequence of appearance (helpful for age estimation in children):

1. Capitate – 2nd to 3rd month after birth.

2. Hamate – 3rd to 4th month after birth.

3. Triquetral – 3rd year.

4. Lunate – 4th year.

5. Scaphoid – 5th year.

6. Trapezium – 6th year.

7. Trapezoid – 7th year.

8. Pisiform – last, appears around 10–12 years (puberty).

• Complete ossification by about 20 years.