Page 176 - Anatomy and Physiology of Farm Animals, 8th Edition

The Equine Foot and Passive Stay Apparatus / 161

suspensory ligament and three sets of
Radius
distal sesamoidean ligaments that con-
VetBooks.ir nect the proximal sesamoid bones with
the middle and proximal phalanges.
Carpal bones Taken together, this set of structures pro-
vides a band that supports the fetlock
(discussed later in the section on the stay
apparatus). The sesamoidean ligaments
that connect the proximal sesamoids to
more distal structures include, from
superficial to deep, a straight sesamoid-
Metacarpus
ean ligament, two oblique sesamoidean
ligaments, and a pair of cruciate sesa-
moidean ligaments (Fig 8‐11A). Their
names describe their gross appearance;
the straight ligament attaches to the mid-
dle phalanx, and the others to the proxi-
Proximal phalanx mal phalanx.
The proximal sesamoids are also linked
together by a broad ligament, the palmar
Middle phalanx (plantar) ligament. This ligament forms a
Navicular bone
smooth depression between the sesamoid
Distal phalanx bones, covered by synovial membrane for
frictionless movement of flexor tendons
Figure 8-10. Palmar view of the equine manus, which pass over the palmar/plantar aspect
illustrating the elements of the suspensory of the sesamoids.
apparatus: suspensory ligament (red), proximal The distal sesamoid bone (navicular
sesamoid bones (purple), and distal sesamoidean bone) has a number of ligaments associ-
ligaments (blue). The suspensory apparatus forms ated with it. Medial and lateral collat-
a continuous ligamentous band that passes from eral ligaments attach the navicular to
the carpus and proximal metacarpus to the proxi- the distal phalanx, and an additional
mal and middle phalanges. This part of the stay unpaired ligament (impar ligament)
apparatus is the most important support for the extends from the distal sesamoid to the
fetlock joint. solar surface of the distal phalanx. The
proximal face of the navicular bone is
Upon reaching the fetlock, the suspen- connected to the middle phalanx and the
sory ligament divides into several branches. deep digital flexor tendon by the T liga-
The main continuation of the suspensory ment (Fig. 8‐2).
ligament attaches to the proximal sesa- The many ligaments and tendons of the
moid bones and to the ligaments that bind equine digit are bound together with a
these two bones together. In addition, number of encircling annular ligaments.
medial and lateral bands (extensor slips or These are reasonably discrete thickenings
extensor branches) extend to the dorsal of the local deep fascia. The palmar/plan-
side of the fetlock to attach to the tendon of tar annular ligament arises from the
the common digital extensor muscle proximal sesamoids and wraps around the
(Fig. 8‐11B). The suspensory ligament acts palmar/plantar aspect of the fetlock, where
as a strong supportive mechanism for the its collagenous fibers blend with the flexor
fetlock, discussed later with the stay tendon sheath (Fig. 8‐11B). More distal,
apparatus. two (proximal and distal) digital annular
The proximal sesamoid bones form a ligaments encircle the bones of the digit
critical physical connection between the and the digital flexor tendons.