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Normal Motion of Wrist Bones

May 29, 2012 by Leave a Comment

The motion of the wrist consists of following movements

  • Flexion
  • Extension
  • Radial deviation
  • Ulnar Deviation
  • Axial rotation around the distal radioulnar joint

Normal flexion and extension are 65-70 degrees. Radial deviation is 20 degrees and ulnar deviation is 40 degrees. Carpal bones contribute about 10 degrees of rotation while rest is contributed by forearm [about 140 degrees]

The motion of the carpus is as a result of  complex arrangements between the two carpal rows. Wrist’s versatility mostly is due to the intercalated three-bone system of the proximal carpal row. [Read more...]

Filed Under: Anatomy, Wrist Injuries Tagged With: , ,

Xray of Wrist Showing Carpal Bones

May 20, 2012 by Leave a Comment

Xray of wrist showing carpal bones.

Each carpal bone has been marked. Readers not used to read xrays might have in understanding overlapping bones.

Carpal Bones

Carpal Bones- See theText For Details

The carpus has eight bones in two rows

The proximal row consists of the scaphoid, the lunate, and the triquetrum.

The distal row consists of Trapezium, trapezoid, capitate and hamate.

In the xray the bones have been mareked as follows.

S – Scaphoid
L- Lunate
T – Triquetrum
P – Pisiform
Tm – Trapezium
Td – Trapezoid
C – Capitate
H – Hamate

Filed Under: Anatomy, Images, Radiology Tagged With: , , ,

Trapezium

March 13, 2010 by Leave a Comment

The trapezium bone or greater multangular bone is a carpal bone situated at distal row on the radial side of the carpus, between the scaphoid and the first metacarpal bone.

Carpal Bones - Distal and Proximal Rows Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate

Surfaces and Articulations

The inferior surface is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface for articulation with the base of the first metacarpal bone.

The dorsal surface is rough.

Left Trapezium Bone, Lesser Multangular means Trapezoid and navicular is another name for scaphoid

The palmar surface is narrow and rough. At its upper part is a deep groove, it transmits the tendon of the Flexor carpi radialis.

The lateral surface is broad and rough, for the attachment of ligaments.

The medial surface presents two facets; the upper, large and concave, articulates with the trapezoid; the lower, small and oval, with the base of the second metacarpal.

Filed Under: Definitions, S-Z Tagged With: , ,

Capitate

March 10, 2010 by Leave a Comment

Capitatetate bone is the largest of the carpal bones, and occupies  the distal row in the center of the wrist.

It has

  • A rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones
  • A constricted portion or neck
  • The body. The bone is also found in many other mammals, and is homologous with the “third distal carpal” of reptiles and amphibians.

Carpal Bones - Distal and Proximal Rows Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate

Capitatus in Latin means having a head.

Left Capitate Bone

Surfaces & Articulations

The superior surface is round, smooth, and articulates with the lunate bone.

The inferior surface is divided by two ridges into three facets, for articulation with the second, third, and fourth metacarpal bones, that for the third being the largest.

The dorsal surface is broad and rough.

The volar surface is narrow, rounded, and rough, for the attachment of ligaments and a part of the Adductor pollicis muscle.

The lateral surface articulates with the trapezoid by a small facet at its anterior inferior angle.

The medial surface articulates with the hamate nt.

The capitate articulates with seven bones

  • Scaphoid and lunate proximally
  • Second, third and fourth metacarpal distally
  • Trapezoid on the radial side, and hamate on the ulnar side.
Filed Under: A-D, Definitions Tagged With: , ,

Scaphoid

March 8, 2010 by 2 Comments

The scaphoid bone is the largest bone of the proximal row of wrist bones and is situated at the radial (radius bone) side of the carpus [See fig below].

It is approximately the size and shape of a medium sized cashew and its long axis is directed  from above downward, lateralward, and forward.

Skaphe means “a boat,” and  eidos means “form” in Greek. The name scaphoid is derived by combining two words signifying its shape.

Carpal Bones - Distal and Proximal Rows Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate

Surfaces & Articulations

The superior surface is convex, smooth, of triangular shape, and articulates with the lower end of the radius.

The inferior surface, directed downward, lateralward, and backward, is also smooth, convex, and triangular, and is divided by a slight ridge into two parts, the lateral articulating with the trapezium, the medial with the trapezoid.

Left Scaphoid Bone

On the dorsal surface is a narrow, rough groove, which runs the entire length of the bone, and serves for the attachment of ligaments.

The volar surface is concave above, and  has a tubercle, which is directed forward and gives attachment to the transverse carpal ligament and sometimes origin to a few fibers of the abductor pollicis brevis.

The lateral surface is rough and narrow, and gives attachment to the radial collateral ligament of the wrist.

The medial surface presents two articular facets; of these, the superior  articulates with the lunate bone the inferior for the head of the capitate bone.

The distal convex surface articulates with trapezium and trapezoid.

to a flexed or “humpback” posture (49,50).

Vascular Supply of Scaphoid

Scaphoid receives majority of its blood supply via dorsal vessels at or just distal to waist area, perfusing proximal pole in a retrograde fashion. Mojor blood supply of the scaphoid is through vascular branches of radial artery entering scaphoid through foramina along its dorsal ridge. It supplies 70-80% of bone, including entire proximal pole.

Second group arise from palmar & superficial palmar branches of radial artery & enter carpal scaphoid in region of its distal tubercle perfusing distal 20-30 % of bone, including tuberosity.

Because of its unusual retrograde vascular supply, the scaphoid has a high risk of nonunion and osteonecrosis after fracture.

Filed Under: Anatomy, Definitions, S-Z Tagged With: , ,

Lunate

March 5, 2010 by 2 Comments

The lunate bone  or semilunar bone is a carpal bone situated in the center of the proximal row of the carpus (wrist).  {See diagram below}

Lunate is situated between the lateral scaphoid bone and medial triquetral bone. .

The name derives from the Latin luna which means “moon”, the lunate bone looks semi-similar to a crescent moon.

Carpal Bones - Distal and Proximal Rows Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate

The superior surface, convex and smooth, articulates with the radius.

The inferior surface is deeply concave and  articulates with the head of the capitate, and, by a long, narrow facet with the hamate.

l

Left Lunate Bone

The dorsal and palmar surfaces are rough, for the attachment of ligaments.

The lateral surface articulates with the scaphoid.

The medial surface is marked by a smooth, quadrilateral facet, for articulation with the triangular bone (triquetral).

Filed Under: Definitions, I-M Tagged With: , ,

Anatomy of The Carpal Bones

January 18, 2008 by 2 Comments

The carpus is made up of 8 carpal bones, which are arranged in two rows.
1. The proximal row contains (from lateral to medial side) (i)the scaphoid, (ii)lunate, (iii) triquetral, and (iv) pisiform bones.
2. The distal row contains in the same order (i) the trapezium, (ii) trapezoid, (iii) capitate, and (iv) hamate bones. [Read more...]

Filed Under: Anatomy Tagged With: , , , , , , , ,