Digital radiography is another of the innovations of veterinary medicine that has significantly changed the way we practice. Conventional radiography was often more of an art than a science. Motion artifacts and exposure errors were common and cause for repeated exposures. With the advent of digital radiography, veterinarians now have unprecedented imaging capability for evaluation of orthopedic conditions of the horse. Detail is, for most structures, incredible. So much so, that we have had to re-learn much of what we thought was “normal” about articular structures. We have fewer re-takes and we can magnify and change the contrast and brightness of the images to evaluate subtle findings not previously possible.
In some cases it is necessary or helpful to perform special radiographic studies of a horse with a potential injury to synovial structures within the limb. A "contrast study" is a radiographic study in which a radiopaque dye (that appears on the radiographic image as a bright white liquid) is injected into the body, usually to define the limits of a synovial structure such as a joint capsule or tendon sheath.
The digital radiograph on the right was taken of a horse that stepped on a nail and developed a severe lameness of that foot a few days later. In this image you can see that a needle has been placed into the navicular bursa and contrast material was injected to see if the hole in the horse's sole communicated with the bursa. A thin stream of contrast material can be seen exiting from the bursa through the solar surface of the foot, confirming penetration of the nail from the sulcus of the frog into the navicular bursa. This information is critical to the proper management of this type of injury. With an arthroscope placed into the navicular bursa, an opening was made in the sole of the foot to clean and flush the bursa. Post-operatively, regional limb perfusion was used in conjunction with systemic anti-microbial and anti-inflammatory therapy to help eliminate the infection.