Veterinary Gross Anatomy

Carpals

CARPAL BONES
(Ox, Sheep and Goat, Horse, Pig, Dog, Rabbit, Fowl)

• The carpals are arranged in the following pattern in domestic animals.

 

Ox

• The carpus consists of six bones arranged in two rows -four in the proximal and two in the distal rows. They are short bones arranged as noted below.

	Medial		Lateral
Proximal row	Radial carpal	Intermediate carpal	Ulnar carpal	Accessory carpal
Distal row	Fused second and third carpal		Fourth carpal

                              

Radial carpal (scaphoid)

• It is the largest bone of the upper row.
• The proximal surface is convexo-concave from before backward and articulates with the radius.
• The distal surface articulates with the fused second and third carpal.
• The lateral face bears facets for the intermediate carpal.
• The dorsal, medial and volar faces are continuous and rough.

Intermediate carpal (lunar)

• It is wedge-shaped.
• The dorsal face is rough and forms the base.
• The apex is posterior, is prolonged medially.
• The proximal face is convexo- concave from before backward and articulates with the radius.
• The distal face is divided by a sagittal ridge into two facets for the second and third and the fourth carpals.
• The medial face has facets for the radial carpal.
• The lateral face articulates with the ulnar carpal.

Ulnar carpal (cuneiform)

• It is very irregular.
• The proximal face is oblique directed backward and downward, encroaches on the distal face and articulates with the fourth carpal.
• The medial face has facets for the intermediate carpal.
• The dorsal face is rough and convex
• The volar face has a facet for the accessory carpal.

Accessory carpal (pisiform)

• It is short, thick and rounded.
• It is a sesamoid bone situated behind the ulnar carpal.
• The proximal face is narrow and rough for flexor ulnaris and ulnaris lateralis.
• The distal face is broad and rough.
• The dorsal face has facet for the ulnar carpal.

Fused second and third carpal (os magnum)

• It is the largest of the carpals the medial one of the two bones of the distal row.
• The proximal face has two facets, medial larger for the radial carpal and the lateral smaller for the intermediate carpal.
• The distal face articulates with the large metacarpal.
• The lateral face has facets for the fourth carpal.
• The medial and dorsal faces are continuous rough and convex.

Fourth carpal (unciform)

• The proximal face has two facets for the intermediate and the ulnar carpals.
• The distal face articulates with the large metacarpal.
• The medial face has facets for the fused second and third carpal.
• The dorsal and the lateral faces are continuous and rough.

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Sheep and Goat

• Resembles that of ox.
• The accessory carpal is long and less tuberous.

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Horse

Has seven or eight bones. They are:

• Radial carpal: Resembles that of the ox.
• Intermediate carpal: The lateral angle of its proximal face is more pointed.
• Ulnar carpal: The smallest bone of the proximal row. The proximal face articulates only with the radius.
• Accessory carpal: It is discoid. The medial face is concave and the lateral is convex and rough. A smooth groove for the long tendon of ulnaris lateralis crosses its anterior part obliquely downward and slightly forward. The anterior border has two facets -the upper concave for the radius and the lower convex for the ulnar carpal.
• First carpal (trapezium): It is inconstant; when present it is situated behind the second.
• Second carpal (trapezoid): It is the smallest bone of the distal row. The proximal face has a convex facet for the radial carpal. The distal face is flat and articulates with the medial small and large metacarpals. The lateral face has two facets for the third carpal. The dorsal and the medial faces are continuous and rough.
• Third carpal (os magnum): It is the largest carpal. It is irregularly triangular with the base anterior. The proximal face articulates with the radial and the Intermediate carpals and distal with the large and medial small metacarpals. The medial border is more concave than the lateral. Fourth carpal (unciform) - It the proximal face is convex and articular and encroaches on the lateral face. The distal face articulates with the large and the lateral small metacarpals. The medial face has two facets for the third carpal.

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Pig

•   It has eight bones – four in each row.

	Medial		Lateral
Proximal row	Radial carpal	Intermediate carpal	Ulnar  carpal	Accessory carpal
Distal row	First carpal	Second carpal	Third carpal	Fourth carpal

The bones of the proximal row resembles that of an ox with the exception that accessory carpal is similar to that of horse but has no lateral groove. The first carpal is small, elongated from before backward, rounded and articulates in front with the second carpal.

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Dog

• It has seven bones -Three in the proximal and four in the distal row. The radial and the intermediate are fused.

	Medial		Lateral
Proximal row	Radial -Intermediate  carpal		Ulnar  carpal	Accessory carpal
Distal row	First carpal	Second carpal	Third carpal	Fourth carpal

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Rabbit 

• It has nine bones arranged in 2 rows.

	Medial		Lateral
Proximal row	Radial carpal	Intermediate carpal	Ulnar carpal	Accessory carpal
Distal row	First carpal	Second carpal	Central carpal	Third carpal	Fourth carpal

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Fowl

• There are only two free bones in the adult.
• The radial carpal is quadrilateral while the ulnar carpal is forked.
• The bones of the lower row fuse with those of the carpus during the development forming the carpometacarpal bone.

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	Medial		Lateral
Proximal row	Radial carpal	Intermediate  carpal	Ulnar  carpal	Accessory carpal
Distal row	First carpal	Second carpal	Third carpal	Fourth carpal