Page 360 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.8 Soft-tissue injuries 335

VetBooks.ir fetlock degenerative joint disease (DJD) and contra- to image (Fig. 1.657). It may be a component of
fragmentation or fracture of the base of the PSBs.
lateral laminitis are common lethal complications.
Surgical arthrodesis of the fetlock is the preferred
assess the bony component of the injury. CT and
alternative for salvage. Radiographs of the digit and fetlock are required to
MRI may be useful to confirm injury in this area.
Prognosis Ultrasonography can provide diagnostic images in
The prognosis is hopeless for sports activities. It is an experienced operator’s hands, but it can be dif-
poor for pasture soundness with conservative man- ficult to obtain adequate quality images due to the
agement and fair after surgical arthrodesis. position of these ligaments under the base of the
PSBs, the angle between their fibres and the skin,
DISTAL SESAMOIDEAN the presence of the ergot and the thick, poorly
LIGAMENT DESMOPATHY echogenic skin in that area. The use of a con-
vex or microconvex array transducer can improve
Definition/overview image quality. Oblique distal sesamoidean ligament
This is a rare condition involving strain injury to (ODSL) and straight distal sesamoidean ligament
one or several of the distal sesamoidean ligaments (SDSL) tears are rare, but they are occasionally rec-
(DSLs). Short (deep) and cruciate distal sesamoid- ognised, especially in trotters. They should be con-
ean ligament (DDSL) injury is rare, but probably sidered a part of suspensory apparatus breakdown
underdiagnosed as these ligaments are difficult injuries (including SL desmitis and PSB transverse
and basilar fractures), although the author has
encountered several cases of ODSL injury as a result
1.657 of overreach injuries to the palmarolateral or medial
aspect of the fetlock. Severe injury to the straight
and oblique DSLs can lead to proximal interphalan-
geal (PIP) joint subluxation.

Aetiology/pathophysiology
The aetiology is unclear, but this condition may be
due to trauma (overreach), to a single strain injury,
possibly due to asymmetric overextension of the
fetlock, or to chronic recurrent strain. Surprisingly,
these injuries are usually not associated with lesions
in the SL, although, occasionally, concurrent branch
injuries may be encountered. Avulsion fractures of
the base of the PSBs, insertions sites on the proximal
phalanx or middle scutum insertion on the second
phalanx may be present.

Clinical presentation
Fig. 1.657 Long-axis, parasagittal sonogram of the The clinical signs are variable. Lameness is usually
palmaromedial fetlock. A microconvex probe is placed marked to moderate and there may be obvious dis-
between the axial border of the base of the medial PSB tension of the digital sheath or fetlock joint. With
and P1, just medial to the ergot. The normal DDSLs ODSL desmopathy, thickening may be palpated
(arrows) are visualised deep to the SDSL. The latter over the distal abaxial aspect of the affected sesamoid
originates from the proximal scutum (PS) and base of bone. In some horses there are little or no localising
the PSBs. The scan plane catches the medial edge of signs. There is usually marked pain on passive digi-
the SDFT. tal flexion and hyperextension.