rigid osseous structure compared with an unossified cartilage, possibly resulting in
increased stress, modeling, and risk for bone trauma or fracture at the base of the
extensively ossified cartilage.
On MRI, CL injury was defined as increased signal intensity in T1 and T2*-weighted
(W) gradient echo (GRE) or fast spin echo (FSE) images in part or all of the
ligament, with enlargement or change in shape, or altered definition of the margins,
with or without alteration in signal intensity in the perligamentar tissues. Interpretation
of MR images is potentially confounded by the magic angle effect (MAE) in images
acquired in both low-field48 and high-field magnets49 related to the orientation of the
fibers, especially at the origin; the lateral CL is especially susceptible in images
acquired standing because of its more sloping orientation. Use of sequences with
long echo times is useful to reduce the MAE but does not abolish it completely.
Nuclear scintigraphy was performed in 21 horses, and IRU was identified at the
insertion of a CL in one (n =7) or both (n= 2) limbs of nine horses, medially in 10
limbs, and laterally in one. All of these 11 limbs had associated MRI abnormalities of
the CLs. There was no relationship between the presence of IRU and the presence
of osseous abnormalities detected through the use of MRI.
Magnetic resonance images of 313 feet of 289 horses with foot pain and a definitive
diagnosis of collateral desmopathy of the DIP joint were retrospectively analyzed for
presence and type of osseous abnormality in the middle and distal phalanges (Dakin
et al. 2009). Osseous abnormalities were detected in 45.7% of feet. Endosteal
reaction and entheseous new bone at the ligament origin (8.3% of feet), entheseous
new bone (36.4%) and focal increased bone oedema signal on STIR images (11.5%)
at th e insertion of the ligament, osseous cyst-like lesions (14%.) and diffuse
increased signal intensity on STIR images (7.3%) were recorded.
Moderate or intense focal IRU was seen either at the site of insertion of the CL (15%)
or at the insertion and extending into the ipsilateral palmar process (4%). Focal
intense IRU in one or more palmar process was observed in 14% of feet. There was
a significant association between presence of IRU and osseous injury (P <0.001),
but normal RU did not preclude significant osseous pathology associated with CL
injury. Nuclear scintigraphic examination may be useful for the detection of osseous
pathology associated with CL injury, although a negative result does not preclude the
presence of osseous injury.
Deep digital flexor tendon injuries
Primary lesions of the DDFT as the principal cause of lameness were seen in 80
horses between January 2001 and March 2005 (Dyson et al. 2005). Nineteen of 76
horses (25%) had IRU in the region of the DDFT in lateral pool phase scintigraphic
images. Twenty-four horses (32%) had IRU in bone phase images in the region of
insertion of the DDFT on the distal phalanx. Only 10 of 75 (13.3%) horses had
detectable ultrasonographic abnormalities of the DDFT, although many lesions did
extend into the pastern when evaluated with the use of MRI.
Navicular disease
It is clear that there are a variety of forms of navicular bone pathology (Dyson et al.
2011) such as degenerative lesions of the palmar compact bone, including deep
erosions involving both the fibrocartilage and subchondral bone. There are lesions
restricted to the spongiosa characterized by increased fluid-like signal in fatProceedings
of
the
South
African
Equine
Veterinary
Association
Congress
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