Limb Positioning for Assessing Joints via X Ray (AAEP 2012)

Lower limb radiographs can help practitioners uncover valuable information about bones, joints, and joint balance in equine athletes, but Colorado State University (CSU) researchers have determined the usefulness and accuracy of this information depends largely on how the horse stands during X ray capture.

“Imbalances in certain joints such as the interphalangeal joints, also called the pastern and coffin joints, can influence gait, biomechanics, and soundness in horses,” said Erin Contino, DVM, MS, of CSU’s College of Veterinary Medicine, in her presentation at the 2012 American Association of Equine Practitioners Convention, held Dec. 1-5 in Anaheim, Calif.

Imbalances can occur for several reasons, such as the horse’s natural conformation, the type of shoe he is wearing, or how he is shod. Imbalances in the foot where one heel bulb is “higher” than the other, for example, can impact the balance of the joints higher up in the limb, change how the horse bears weight, and even how he moves. In fact, notes Contino, foot imbalances can influence gaits, biomechanics, and soundness.

Further, Contino and colleagues suspected that how the horse’s foot is positioned while taking radiographs can influence joint balance, making accurate X ray interpretation difficult if the foot is not positioned appropriately.

To test this theory, the researchers took radiographs (dorsopalmar, taken directly from the front to back of the limb) of 14 limbs in nine horses. During the study the team placed horses in three different positions: square, and in 5° and 10° abduction (by moving the foot out sideways). They measured two “sides” of the pastern and coffin joints (the later and medial joint spaces) in all three positions. Key findings were:

  • Limb abduction resulted in narrowing of the joint space on the medial (inner) aspect of the joint; and
  • Joint balance differences between the different limb positions were statistically significant.

“As we hypothesized, how a horse is positioned while taking the X rays significantly affects joint balance,” said Contino. “Practitioners are therefore encouraged to position the horse as squarely as possible as correct positioning is essential for evaluating the pastern and coffin joint spaces.”

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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