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BONES OF HAND- CARPAL

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BONES OF HAND- CARPAL

CARPAL BONES
  • Short bones, eight in number.
  • Arranged in two proximal and distal, each row presenting four bones.
  • From lateral to medial side, bones of proximal row are scaphoid, lunate, triquetrum and pisiform.
  • bones of distal row are trapezium, trapezoid, capitate and hamate.

OSSIFICATION:

  • Ossification of carpal bones appear after birth in a spiral manner as follows:

CARPAL  BONE

OSSIFICATION  (in yrs)

Capitate

1

Hamate

2

Triquetrum

3

Lunate

4

Scaphoid

5

Trapezium

6

Trapezoid

7

Pisiform

12

 

 Note: The scaphoid bone is a small carpal bone on the thumb side (radial side) of the wrist. It is the most commonly fractured carpal bone.

  • This is probably because it actually crosses two rows of carpal bones, forming a hinge.

Articulations:

CARPAL BONE

ARTICULATING WITH

Scaphoid

 Radius, trapezium, trapezoid, lunate, capitate

Lunate

Radius, capitate, hamate, scaphoid, Triquetral

Triquetrum

Hamate, lunate, pisiform

Pisiform

Triquetral

Minimum articulation with only 1 bone

Trapezium

Scaphoid, trapezoid, 1st & 2nd metacarpal

Trapezoid

Scaphoid, trapezium, capitate, 2nd metacarpal

Capitate

Scaphoid, lunate, trapezoid, hamate, 2nd 3rd & 4th metacarpals

Maximum articulation with 7 bones

Hamate

Lunate, capitate, Triquetral, 4th & 5th metacarpals

 BONY PILLARS:

  • There are four bony pillars at the four corners of the carpus.
  • All attachments are to these four pillars:
1) The tubercle of the scaphoid:
  • The flexor retinaculum
  • A few fibers of the abductor pollicis brevis
2) The pisiform gives:
  • Flexor carpi ulnaris
  • Flexor retinaculum and its superficial slip
  • Abductor digiti minimi
  • Extensor retinaculum
3) The trapezium:
  • The crest gives origin to the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis. These constitute muscles of thenar eminence.
  • The edges of the groove give attachment to the two layers of the flexor retinaculum.
  • The lateral surface gives attachment to the lateral ligament of the wrist joint.
  • The groove lodges the tendon of the flexor carpi radialis.
4) The hamate:
  • The tip of the hook gives attachment to the flexor retinculum.
  • The medial side of the hook gives attachment to the flexor digiti minimi and the opponens digiti minimi.
APPLIED ANATOMY: 

– Kienbock’s disease is osteochondritis of lunate.

– Capitate is the largest carpal bone, first carpal bone to ossify and articulates with maximum number of bones.

– Lunate is the most commonly dislocated carpal bone.

– Scaphoid is the most commonly fractured carpal bone.

  • The scaphoid bone is a small carpal bone on the thumb side (radial side) of the wrist. It is the most commonly fractured carpal bone.
  • This is probably because it actually crosses two rows of carpal bones, forming a hinge.

Exam Important

  • 4th carpal bones (Lunate) are present at 4 yrs of age.
  • Carpal bones articulate with radius are Scaphoid and lunate.
  • Carpal bone which fracture commonly is Scaphoid.
  • The commonly injured carpal bone next to scaphoid is Trapezium.
  • Lunate carpal bone fracture causes median nerve involvement.
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