Page 237 - Adams and Stashak's Lameness in Horses, 7th Edition

Diagnostic Imaging 203

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Figure 3.19. Lateromedial (LM) projection of the metacar­
pophalangeal joint with marked supracondylar bone loss on the
Figure 3.18. Dorsolateral to palmaromedial oblique (DLPMO) palmar cortex of distal MCIII (short arrow), secondary to chronic
projection of the metacarpus showing a well‐defined osseous body inflammation and effusion within the joint.
(sequestrum) surrounded by a radiolucent rim (cloaca) on the mid‐
diaphysis of MCIV. There is mild surrounding sclerosis and a small
periosteal reaction just proximal to the cloaca, representing the
involucrum (arrow).

Trabecular Bone
Generalized bone opacity may be decreased or
increased. Decreased bone density is seen secondary to
chronic moderate to severe lameness resulting in decreased
load bearing. The osteopenia that develops in these limbs
can be recognized radiographically as a coarse trabecular
pattern with or without thin cortices (Figure 3.22).
Increased bone opacity, often referred to as sclerosis,
is identified radiographically with loss of trabecular pat­ Figure 3.20. Palmaroproximal to palmarodistal oblique
tern secondary to bone deposition within the medullary (Pa45Pr‐PaDiO, skyline) projection of the navicular bone. On the
cavity (Figure 3.23). Sclerosis is a common adaptive flexor aspect of the navicular bone, note the poor corticomedullary
definition, irregular medullary sclerosis, and cortical erosions
response to load bearing and is frequently found in the consistent with advanced degenerative changes.
third carpal bone and central and third tarsal bones
(Figure 3.24). Increased bone density is also routinely
seen at proximal MCIII or MTIII at the origin of the route of infection. Both acute and chronic osteomyelitis
suspensory ligament. 23,56 can be identified radiographically (Figures 3.25 and
3.26). It generally takes 7–10 days after clinical signs of
Radiographic Signs (Bone Response Patterns) acute osteomyelitis are observed before the earliest
with Osteomyelitis detectable radiographic bone changes occur because at
least 50% of mineral content must be depleted from the
Osteomyelitis in equine limbs may be hematogenous bone to be radiographically visible.
in origin or result from penetrating wounds or open Because osteomyelitis can affect any bone in an equine
fractures. The region affected depends on the source and limb and must be differentiated from other focal bone