Page 569 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 535

with corticosteroids and HA, and intralesional treat- Etiology
58
ment of the damaged ligament with stem cells or plate- Similar to injury to other ligaments, there is often
VetBooks.ir fragments that may be associated with DSL avulsion an initial small injury that leads to inflammation,
let‐rich plasma (PRP). Nonarticular base sesamoid
fibrosis, and loss of elasticity, which leads to func-
injuries should be removed using a “keyhole” surgical
4
approach through the DFTS. With this approach, frag- tional shortening of the ligament and constriction over
ments are localized with needles and removed using the flexor tendons. Continued athletic use then causes
arthroscopic rongeurs. Nine of 10 surgically treated additional injury to the previously damaged and func-
horses returned to their intended use. 4 tionally shortened ligament leading to recurrent
inflammation, fibrosis and loss of elasticity, and fur-
ther functional shortening. The permanent fibrosis
Prognosis and resultant constriction over the flexor tendons is
The prognosis for horses with DSL injuries to likely why horses generally do not respond to rest and
return to performance has historically been consid- medical therapy.
ered to be guarded because of the high probability of re‐
injury. However, more recent studies have indicated a Clinical Signs
much better prognosis. Seventy‐six percent, 66%, and
90% of horses with DSL injuries or avulsion fractures of Affected horses have a mild to moderate and consist-
the proximal sesamoid bones returned to performance fol- ent lameness and minimal to no external signs. Horses
lowing treatment. 4,58,61 However, recurrence of DSL desmi- may be positive to flexion of the distal limb.
tis is always a possibility, similar to other soft tissue
injuries. In addition, concurrent musculoskeletal problems Diagnosis
such as PIP joint OA, navicular syndrome, and suspensory
desmitis often reduce the prognosis for full recovery. A palmar (plantar) digital nerve block or intrathecal
DFTS block will greatly improve the lameness associ-
ated with injuries to the PDAL and DDAL.
DESMITIS OF DIGITAL ANNULAR LIGAMENTS Ultrasound of the PDAL is easily performed and the
normal dorsal to palmar/plantar thickness of the liga-
Within the pastern region there are two superficial ment is 2 mm. Desmitis of the PDAL is seen as a
22
ligaments that form a retinaculum for the flexor ten- thickened ligament with heterogeneous echogenicity.
dons: the proximal digital annular ligament (PDAL), Due to location within the foot, distal to the DFTS, it
which inserts medially and laterally on the proximal and is difficult to thoroughly assess the DDAL with ultra-
distal tubercles of P1, and the distal digital annular liga- sound. High‐field MRI is the preferred technique for
ment (DDAL), which runs from the medial and lateral diagnosis of injury to the DDAL (Figure 4.115). The
borders of distal P1 to the palmar/plantar aspect of P3 thickness of the normal DDAL is also 2 mm. When
(Figure 1.11). Primary injury to both the PDAL and the injured, the thickness can increase up to 10 times the
DDAL can be a cause of lameness in the horse. 7,22 normal thickness. 7

Figure 4.115. Transverse and sagittal PD‐weighted images showing thickening and mixed signal intensity DDAL. The dotted line on the
sagittal image represents transverse slice location.