Page 55 - Adams and Stashak's Lameness in Horses, 7th Edition

Functional Anatomy of the Equine Musculoskeletal System 21

end of the second metacarpal bone laterad to the acces­
sory carpal bone. By bridging the carpal groove, the
VetBooks.ir carpal canal. It blends both proximally and distally with
flexor retinaculum forms the mediopalmar wall of the
the fascia of the limb. Proximally, the fan‐shaped acces­
sory ligament of the SDFT (radial check ligament) com­
pletes the medial wall of the carpal canal. The accessory
Accessorioulnar ligament carpal bone and its two distal ligaments form the lateral
wall of the carpal canal. The palmar carpal ligament
forms the smooth wall interposed between flexor ten­
Lateral dons and the carpal bones; it serves as part of the com­
collateral mon fibrous capsule on the palmar side of the carpus.
ligament Distally, the palmar carpal ligament gives origin to the
carpal check ligament of the DDFT.
Accessoriocarpo- The carpal canal (Figures 1.24 and 1.25) contains the
ulnar ligament following structures: the SDFT and DDFT enclosed in
the carpal synovial sheath, the medial palmar nerve and
Dorsal intercarpal artery, and the lateral palmar nerve, artery, and vein.
ligaments
Medial to the carpal canal, just outside the flexor reti­
Accessorioquartal naculum, the tendon of the flexor carpi radialis descends
ligament to its attachment on the head of the medial splint bone.
Dorsal carpometacarpal The radial artery and vein lie palmar to this tendon
ligament embedded in the flexor retinaculum.
The carpal synovial sheath enclosing the digital flexor
Accessoriometacarpal tendons extends from 8 to 10 cm proximal to the ante­
ligament
brachiocarpal joint to near the middle of the metacarpus
(Figure 1.25). Fibers from the carpal check ligament of
the SDFT blend into the medial aspect of the proximal
end of the sheath. Between the flexor tendons, an inter­
tendinous membrane attaches to the palmaromedial sur­
face of the DDFT and the dorsomedial surface of the
SDFT, dividing the carpal synovial sheath into lateral
and medial compartments. 40
In the forearm proximal to the carpus, the palmar
Figure 1.22. Carpal ligaments, lateral view.
branches of the median and collateral ulnar arteries
anastomose deep to the flexor carpi ulnaris muscle
(Figure 1.18). Small branches from the palmar branch of
the median and proximal radial arteries supply the vas­
cular network of the deep palmar carpal region, the rete
carpi palmare. The small lateral palmar artery continues
distad to near the proximal end of the fourth metacarpal
bone where it participates with the radial artery in form­
Accessory carpal bone
ing the proximal deep palmar arch. Branches from the
radial artery (also a terminal branch of the median
artery) extend around the medial aspect of the carpus to
contribute to the dorsal carpal rete.
Intermediate carpal
bone
Medial collateral Carpal Joints
ligament
The bones of the carpus abut one another at a num­
Radial carpal bone ber of intercarpal joints, but these are capable only of
minimal gliding movements. The overall movement of
the carpus comes from the horizontally oriented joints:
Third carpal bone antebrachiocarpal (radiocarpal) between the radius and
proximal row of carpal bones, middle carpal between
proximal and distal rows of carpal bones, and carpo­
metacarpal between the distal row of carpal bones and
Second metacarpal bone
the metacarpals. Nearly all of the flexion and extension
of the carpus come from the antebrachiocarpal and mid­
dle carpal joints; the carpometacarpal joint is a plane
Third metacarpal bone
joint with minimal movement. The extensive antebra­
chiocarpal synovial sac extends between the carpal
bones of the proximal row, including the accessory car­
Figure 1.23. Carpal ligaments, medial view. pal bone. It typically does not communicate with the