Page 571 - Adams and Stashak's Lameness in Horses, 7th Edition

Lameness of the Distal Limb 537

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Figure 4.117. Ultrasound images (left) and contrast tenogram (right) demonstrating a lateral marginal lesion of the DDFT within the
tendon sheath at the level of the proximal sesamoid bones (left; arrows).

Diagnosis
Ultrasonography is currently the most commonly
used method to diagnose tendon injury and can be used
in the pastern for branch lesions of the SDFT, core
lesions of the SDFT, and some abnormalities of the
DDFT. However, ultrasonographic examination in the
pastern region may result in false‐negative results. 2,14,64
This is especially true for the DDFT, where surface and
longitudinal lesions are more common than core lesions
and more difficult to visualize with ultrasound. 14,77,78 It
is important to note that the DDFT becomes bilobed at
the level of the pastern. Each lobe should be similar in
size and shape. A lesion may involve one or both lobes
and is typically characterized by enlargement and altera-
tion of the tendon with or without a hypoechoic region
(Figure 4.118), making it more difficult to visualize with
ultrasound. Dystrophic mineralization may be seen with Figure 4.118. There is enlargement and mixed echogenicity of
chronic injuries (Figure 4.119). 76 the lateral lobe of the DDFT.
In cases that have been blocked to the DFTS or with
nonspecific signs of chronic tenosynovitis of the DFTS,
diagnostics beyond ultrasound should be considered. 77,78 ultrasound. 18,24,25 Five‐ to 7‐mL contrast is injected with
An MRI examination is superior to an ultrasound exam- or without 10‐mL local anesthetic, the horse is walked
ination to characterize the location, type, and severity of 4–5 strides to distribute contrast, and then a lateral to
damage to both the SDFT and DDFT within the pastern medial radiograph is made.
(Figure 4.120). When MRI is not available, a contrast Tenoscopy of the DFTS is a definitive diagnostic tool
tenogram may be useful to define marginal tears of the to document intrathecal lesions of both SDFT and
DDFT as well as tears of the manica flexoria with DDFT that may not be visible with ultrasound. An
improved positive and negative predictive values over added benefit of tenoscopy is the ability to debride