Page 339 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

314 CHAPTER 1

VetBooks.ir injuries (see p. 132). Mechanical interference with nerve impingement. This could explain the poorer
healing and prognosis at this particular site. Osseous
prominent metacarpal or metatarsal bones (periosti-
tis due to ‘splints’ or fractures) has been reported to
cause focal SL body or branch injuries. It is unclear, pathology is frequently encountered in the proximal
metacarpus or metatarsus. Recent MRI studies have
however, whether the bone lesion causes desmitis shown that horses with clinically confirmed proxi-
through mechanical interference or whether chronic mal metacarpal/metatarsal pain may present with
ligament thickening and adhesions are the actual abnormalities in bone and ligament tissues alone
cause of the splint bone reaction or fracture. or in combination. PSLD is probably a complex
Branch lesions may be associated with fracture of syndrome affecting either/or the bones, enthesis,
the distal one-third of the splint bones. It is more ligament and surrounding connective tissues.
likely that the fracture is secondary to branch injury
than the contrary in this case, although both aeti- Clinical presentation
ologies are probably possible. Fibrous adhesions Lameness is usually present and varies from mild to
between the SL and surrounding structures are severe, often worsening with exercise. It may be inter-
increasingly recognised and may be a cause of recur- mittent. In the forelimb, there may be an acute-onset
ring desmopathy, failure of treatments or predispose lameness, while chronic, recurrent lameness with an
to splint formation or fractures. insidious onset is more common in the hindlimb. In
Avulsion fractures of the proximal palmar meta- some cases, there may merely be signs of exercise
carpal or plantar metatarsal cortex are an allied but intolerance or poor performance. Lameness may be
separate condition. Fatigue stress fractures of the increased on the circle, especially on the outside limb.
palmar cortex of MC/MT III are unrelated. It often worsens after prolonged or intense exercise
and when ridden. There are usually no specific local
PROXIMAL SUSPENSORY DESMITIS signs, but occasionally a non-specific, diffuse swelling
of the palmar/plantar metacarpus/tarsus region is pal-
Aetiology/pathophysiology pable. In some cases, digital pressure on the palmar/
Proximal suspensory ligament desmitis (PSLD) plantar limb may lead to resentment, although this
probably develops gradually from chronic, cyclic may also be the case in ‘normal’ horses.
strain, although the pathogenesis remains unclear.
It is increasingly suspected that the condition dif- Differential diagnosis
fers in the fore- and hindlimbs. Forelimb PSLD is Lesions within the other ligaments and tendons in
common in racehorses, including Standardbreds and that region (SDFT, plantar ligament, carpal/tarsal
flat racehorses, but it may be encountered at any age sheath disorders, avulsion or stress fractures, frac-
and in horses used for a wide variety of disciplines. tures or osteomyelitis of the proximal splint bones);
Hindlimb PSLD is most commonly encountered in other causes of inflammation in the metacarpal or
middle-aged dressage or eventing horses. The injury metatarsal area; any other causes of lameness and
is also common and particularly severe in European notably, in the hindlimb, bone spavin.
trotters, both in the fore- and hindlimbs and may
be related to either conformation and/or a specific Diagnosis
action related to this discipline. Horses with straight Diagnosis may be challenging as there are no pathog-
hock and low fetlock conformation may be predis- nomonic signs and the ultrasonographic appearance
posed to PSL injuries in the hindlimb. These have varies.
been shown to be associated with a ‘compartment
syndrome’, the ligament and peripheral neurovascu- Clinical examination
lar structures being encased in a tight sheath, formed A systematic, routine lameness investigation is
by the metatarsal bones dorsally and abaxially and warranted. Many cases are positive to fetlock or
the deep plantar fascia plantarly. The high pressure full-limb flexion and, in the hindlimb, to hock flex-
caused by swelling in a non-expandable canal leads ion. The clinical signs, however, are generally non-
to further tissue necrosis, hypovascularisation and specific. The use of diagnostic analgesia is essential.