Page 44 - Adams and Stashak's Lameness in Horses, 7th Edition

10 Chapter 1

Proximal limit of
the digital synovial
VetBooks.ir sheath
Palmar recess of
the fetlock joint
capsule

Common digital extensor tendon
Proximal sesamoid
bone

Superficial distal
sesamoidean
ligament
Joint capsule of
the pastern joint
Superficial digital flexor
tendon

Deep digital flexor tendon
Joint capsule of
the coffin joint

“T” ligament Distal limit of the digital synovial sheath
Distal Navicular bursa
sesamoidean
impar ligament Navicular bone

Digital cushion

Figure 1.10. Sagittal section of equine fetlock and digit.

proximal extremity of the middle phalanx just palmar to these is the pair of cruciate ligaments that cross midline,
the collateral ligaments of the proximal interphalangeal each attaching distally to the contralateral eminence on
joint. Traditionally, the insertion of the SDFT has been the proximal end of the proximal phalanx. Deepest of the
described as also having additional attachments on the dis­ distal sesamoidean ligaments are a pair of short sesa­
tal extremity of the proximal phalanx; radiographic stud­ moidean ligaments extending from the dorsal aspect of
ies have concluded that these attachments are not strictly the base of each proximal sesamoid bone to the edge of
part of the flexor tendon and instead represent associated the articular surface of the proximal phalanx (Figure 1.11).
palmar ligaments. The DDFT descends between the two An extensor branch of the suspensory ligament passes
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branches of the SDFT. A digital synovial sheath surrounds from the abaxial surface of the respective proximal sesa­
both tendons and continues in association with the DDFT moid bone dorsodistad obliquely across the proximal
as far as the “T ligament” (Figures 1.10 and 1.11). phalanx to the dorsal surface where each branch blends
Deep to the digital flexor tendons, a series of ligaments with the common digital extensor tendon near the distal
(often collectively referred to as the distal sesamoidean end of the proximal phalanx. An elongated bursa under
ligaments) extend distad from the bases of the two proxi­ each extensor branch is extensive enough to be consid­
mal sesamoid bones (Figure 1.11). These are the func­ ered a synovial sheath. 16
tional continuation of the suspensory apparatus into the In the dorsal aspect of the pastern, the common digi­
digit. The most superficial of these is the straight sesa­ tal extensor tendon is attached to the proximal ends of
moidean ligament, which attaches primarily to the pal­ the proximal and middle phalanges on its way to its
mar aspect of the middle phalanx and less robustly to the definitive insertion on the extensor process of the distal
palmar first phalanx. The wedge‐shaped middle (oblique) phalanx. A bursa often occurs under this tendon near its
sesamoidean ligament attaches distally to a rough area on union with the extensor branches of the suspensory liga­
the palmar surface of the proximal phalanx. Deep to ment. The tendon of the lateral digital extensor muscle