Page 452 - Adams and Stashak's Lameness in Horses, 7th Edition

418 Chapter 3

Table 3.6. Frequency of MRI abnormalities in three retrospective high‐field studies of horses with lameness caused by pain localized
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28
6
to the proximal metatarsal region (Brokken et al. and Labens et al. ) or proximal metatarsal and distal tarsal regions (Barrett et al. ).
VetBooks.ir MRI lesions N = 16 horses N = 48 limbs of 39 N = 125 limbs of 103 horses
% incidence
horses
PSD 50 25 53

Bone injury proximal MTIII 0 8 Enthesopathy: 32
Osseous fluid: 23
Concurrent PSD and bone injury proximal 10 19 NS
MTIII
Distal tarsal OA — 6 DITJ: 42
TMTJ: 51
Splint bone injury with focal suspensory — 4 —
desmitis/adhesion

Tarsal bone cyst — 2 18
Slab fracture — ‐ 3
Enthesopathy/desmopathy intertarsal — 2 27
ligaments

Bone marrow lesion tarsal bone(s) — 4 13–22
Medullary injury MTIII — 2 —
Dorsal cortical injury MTIII — 2 —

Tendinopathy DDFT 6 2 —
Tendinopathy SDFT — 2 —
Effusion of the distal tarsal sheath 6 — —
No obvious abnormalities 6 22 —

NS, not specified; OA, osteoarthritis; DDFT, deep digital flexor tendon; MCIII/MTIII, third metacarpal/metatarsal bone; MCIV/MTIV, fourth metacarpal/
metatarsal bone; TMTJ, tarsometatarsal joint; and DITJ, distal intertarsal joint.
Several horses or limbs had simultaneous occurrence of more than one lesion.

proximal palmar/plantar aspect of the cannon bone is The tomographic nature of MRI allows for visualiza­
seen concurrently with proximal desmopathy tion of the margins of the entire suspensory ligament.
(Figure 3.246). The concurrent presence of bony and This has enabled a more definitive diagnosis of adhe­
ligamentous changes appears to be more common in sions between ligament margins and exostoses of the
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forelimbs than hindlimbs, especially in young Quarter second and fourth metacarpal and metatarsal bones,
horses used for cutting. 5 where ultrasonography is unable to determine the exist­
ence of abnormality. Adhesions lead to suspensory
desmitis through tearing of the adhered ligamentous fib­
Adhesions of the Suspensory Ligament
ers with resulting inflammation and lameness. Loss of
In normal forelimbs, a space of loose connective tis­ normal space between the suspensory ligament and a
sue with high signal intensity exists between the medial splint bone, in conjunction with signal or contour
border of the suspensory ligament and the second meta­ changes of the suspensory ligament and bone prolifera­
carpal bone. 124,127 The lateral border of the suspensory tion on the surface of that splint bone, is strongly sug­
ligament is overall closer to the fourth metacarpal bone gestive of adhesion formation. Adhesions may be visible
and may in some areas contact the bone. The same as a tissue band of low signal connecting the ligament to
applies in the hindlimb, where the suspensory ligament an area of osseous proliferation on the axial surface of a
is positioned more laterally on the plantar aspect of the splint bone. However, these findings should be inter­
cannon bone than in forelimbs and the lateral border of preted with caution because normal fibers of the suspen­
the ligament contacts the fourth metacarpal bone sory ligament have been shown to originate from the
between 0 and 2 cm and again between 8 and 12 cm dis­ proximal part of the fourth metatarsal bone and the lat­
tal to the tarsometatarsal joint. eral margin of the normal suspensory ligament is overall