the carpus

THE CARPUS

The bones of the Carpus

Radius

Dorsal view

First row of carpals

Second row of carpals

CANNON and SPLINT BONES

radial carpal 2nd carpal

3rd carpal

accessory carpal

4th carpal

intermediate carpal

2nd metacarpal

Dorsal view

4th metatarsal

Palmar view

Anatomy

Dorsal view of the bottom row of carpal bones

UCICRC

4TH C

3RD C

2ND C

Muscles proximal to the carpus with tendons inserting at the joint

• Flexor carpi ulnaris• Flexor carpi lateralis

Schematic diagram of the musculoskeletal model used in this study.

Harrison S M et al. J Exp Biol 2010;213:3998-4009

©2010 by The Company of Biologists Ltd

Extensor carpi radialis m. Lateral Supracondylar

of Humer

us

Proximodorsal

on Metacarpal III

Radial n.

Extends

carpus

Ulnaris lateralis m. Lateral Epicondyle of Humer

us

Accessory

Carpal Bone

&Metacarpal IV

(Lateral Splint Bone)

Radial n.

Flexes carpus

Extensor carpi obliquus m.(Abductor pollicis longus m.)

Middle of

Radius, Craniolaterally

Proximal

Metacarpal II

(Medial Splint Bone)

Radial n.

Extends

carpus

Extensor carpi radialis: originates from the humerus, continues distally along the dorsal side of the radius, and inserts on the metacarpal tuberosity. Flexes the elbow, extends the carpus. Also used in the stay apparatus to fix the carpus.

Extensor carpi obliquus: originates from the radius and inserts into the top of the second metacarpal. Helps to extend the carpus.

Flexor carpi radialis: originates from the humerus and inserts into the proximal side of the second metacarpal. Flexes the elbow, extends the carpus.

Ulnaris lateralis: originates on the lateral side of the humerus, inserts into the accessory carpal bone and on the proximal side of the lateral splint bone. Flexes the carpus, extends the elbow.

Ligaments of the carpus

The Midcarpal Joint • Medial palmar intercarpal ligament (MPICL)• The lateral palmar intercarpal ligament (LPICL)• The dorsomedial intercarpal ligament (DMICL). • palmar intercarpal ligaments

Biomechanics

Medial viewLateral view

Carpal Joint Function

• To dissipate shock– Multiple cuboidal bone design allows for small

movements during load phases• Safer

– Rows of cuboidal bones making up a joint midway down the limb are advantageous for limbs that are made of a single column of bone.

• to allow for small movements of bones in 3 dimensions; – much greater shock dissipating ability – Better to compensate uneven footing

The advantages of a stack of cuboidal bones at the knee area depends on strong ligamentous

support throughout the support phase

Biomechanics

Over all direction of force on the carpus under load

SCL

ICL

Pathology

Pathology and Lameness

• Hygroma• Degenerative joint disease• Fractures of carpal bones• Soft tissue injury to ligaments• Torn tendons