Page 54 - Adams and Stashak's Lameness in Horses, 7th Edition

20 Chapter 1

Extensor carpi
VetBooks.ir Common digital extensor m. Common digital
radialis m.
Extensor carpi radialis m.
extensor m.
Lateral digital
extensor m.
Medial cutaneous
antebrachial n. Extensor carpi
obliquus m.
Deep digital flexor m.
Radius
Ulnaris lateralis m.

Lateral cutaneous Flexor carpi ulnaris m.
antebrachial n.
Proximal limit of
Site of cross section carpal sheath
in Figure 1.24
Dorsal branch of
Bursa under tendon the ulnar n.
of extensor carpi
obliquus m.

Extensor
retinaculum Lateral collateral ligament

Figure 1.20. Dorsal view of left carpus. Distal limit of carpal sheath

superficial part of the ligament attaches distally on the
fourth metacarpal bone and partly on the third metacar­
pal bone. A canal between the superficial part and the
deep part of the ligament provides passage for the ten­
don of the lateral digital extensor muscle and its syno­
vial sheath. The deep part of the ligament attaches on Figure 1.21. Lateral view of left distal forearm, carpus, and
the ulnar carpal bone. proximal metacarpus. Note that the ulnaris lateralis is now called
Palmar to the lateral collateral carpal ligament, four extensor carpi ulnaris.
ligaments attach to the accessory carpal bone, attaching
it to adjacent bones (Figure 1.22). Two muscles have medial cutaneous antebrachial nerve provides the
insertions on the accessory carpal bone. The short ten­ innervation.
don of the extensor carpi ulnaris muscle (formerly The medial collateral carpal ligament extends from
ulnaris lateralis m.) attaches to the proximal border and the medial styloid process of the radius and widens dis­
lateral surface of the bone; the muscle’s long tendon, tally to attach to the second and third metacarpal bones.
enclosed in a synovial sheath, passes through a groove Bundles of fibers also attach to the radial, second, and
on the bone’s lateral surface and then continues distad third carpal bones (Figure 1.23). The ligament also joins
to insert on base of the lateral splint bone (Figure 1.21). the flexor retinaculum on the palmar aspect of the joint.
Proximally, a pouch of the antebrachiocarpal joint cap­ At this juncture a canal is formed that accommodates the
sule lies between the long tendon of the extensor carpi passage of the tendon of the flexor carpi radialis and its
ulnaris and the lateral styloid process of the radius. The synovial sheath as the tendon descends to the base of the
single tendon of the flexor carpi ulnaris muscle attaches medial splint bone. An inconstant first carpal bone may
to the proximal border of the accessory carpal bone. be embedded in the palmar part of the medial collateral
A strong fibrous band from the accessory carpal bone carpal ligament adjacent to the second carpal bone.
attaches to the lateral digital extensor tendon.
Palmar Aspect
Medial Aspect The flexor retinaculum is a fibrous band extending
On the medial side of the carpus, the skin and fascia from the medial collateral ligament, distal end of the
receive blood from branches of the radial artery. The radius, radial and second carpal bones, and proximal