Page 53 - Adams and Stashak's Lameness in Horses, 7th Edition

Functional Anatomy of the Equine Musculoskeletal System 19

the third metacarpal bone. Small branches from the pal­
mar metacarpal arteries extend through the interosseous
VetBooks.ir sal metacarpal arteries. In the distal fourth of the meta­
spaces between cannon and splint bones to join the dor­
carpus, the palmar metacarpal arteries anastomose to
form the distal deep palmar arch. A branch from this
arch to the lateral digital artery is termed the superficial
palmar arch.
Palmar carpal A single, large palmar metacarpal vein courses proxi­
ligament
mad to join the venous deep palmar arch.
The vascular patterns described above are subject to
considerable variations, but the variations are of no clin­
ical significance.
Suspensory ligament
Carpus
Radial a.v. The carpal region includes the carpal bones (radial,
intermediate, ulnar, and accessory in the proximal row;
first, second, third, and fourth in the distal row), the dis­
Deep branch of tal end of the radius, the proximal ends of the three
lateral palmar n.
metacarpal bones, and the soft tissue structures adjacent
to these osseous components.
Branch from
medial palmar a.
Deep part of Dorsal Aspect
proximal deep A vascular network in the skin on the dorsal carpus,
palmar arch the rete carpi dorsale, is formed by branches from the
cranial interosseus, transverse cubital, and proximal
Nutrient a. of 3rd radial arteries. Medial and lateral cutaneous antebra­
metacarpal bone
chial nerves supply branches to the medial and dorsal
aspects of the carpus. The dorsal branch of the ulnar
Lateral palmar nerve emerges between the tendon of the flexor carpi
metacarpal n. ulnaris muscle and the short tendon of the extensor
carpi ulnaris or between the short and long tendons of
Lateral palmar the latter muscle (Figure 1.21). The nerve supplies
metacarpal a.
branches to the fascia and skin of the dorsal and lateral
aspects of the carpus.
The tendons of each of the antebrachial muscles that
cross the carpus are invested with synovial sheaths,
excepting the extensor carpi ulnaris (formerly ulnaris
lateralis) and flexor carpi ulnaris mm. (Figures 1.20 and
Distal deep palmar arch 1.21). The tendon sheath of the extensor carpi radialis
muscle terminates at the middle of the carpus, and then
Superficial palmar arch the tendon becomes adherent to the retinaculum as it
reaches its insertion on the metacarpal tuberosity
(Figure 1.20). A distal bursa near the insertion often
communicates with the carpometacarpal joint.
A subtendinous bursa lies between the tendon of the
extensor carpi obliquus and the medial collateral liga­
ment of the carpus (Figure 1.20). In most foals younger
than 2 years, the bursa is a separate synovial structure;
in older horses it communicates with the adjacent ten­
Figure 1.19. Deep dissection of caudal aspects of left carpus don sheath. 36
and metacarpus with medial palmar artery removed. The extensor retinaculum serves as the dorsal part of
the common fibrous joint capsule of the carpal joints. It
(the “button”) of the respective splint bone to ramify in attaches to the radius, the dorsal intercarpal and dorsal
skin of the pastern. carpometacarpal ligaments, the carpal bones, and the
The palmar metacarpal arteries originate from the third metacarpal bone. Laterally and medially it blends
proximal deep palmar arch, an anastomotic complex with the collateral ligaments of the carpus.
formed by the termination of the radial artery where it
joins the smaller palmar branch of the median artery
(Figure 1.19). Part of the arch lies between the carpal Lateral Aspect
check ligament and the suspensory ligament. The medial The lateral collateral carpal ligament originates from
palmar metacarpal artery supplies a nutrient artery to the styloid process of the radius (Figure 1.22). The