Ultrasound Beats X Rays for Identifying Articular Lesions

When a horse is lame, computed and digital radiographs (X rays) have, for years, allowed veterinarians to easily visualize bone and joint problems that aren't always visible to the naked eye. But when dealing with abnormalities on joint surfaces, it now appears that ultrasonographic imaging could be the tool of choice, according to one researcher team that completed a study recently comparing the accuracy of ultrasound and radiography in detecting articular lesions.

A team led by Antje Hinz, DVM, formerly a practitioner at Chino Valley Equine Hospital in Chino Hills, Calif., reviewed records of 432 lesions in 254 joints on 137 horses. The researchers selected the study horses after reviewing surgical records of horses that had diagnostic or therapeutic arthroscopy (during which the veterinarian uses a tubular instrument to examine and carry out surgical procedures within a joint) of any joint between November 2003 and December 2006 at the Chino Valley Equine Hospital. 

Lesions identified included everything from bone fragments and degenerative joint disease (arthritis) to the joint disorder osteochondrosis dissecans. Nearly 83% of the lesions were identified via ultrasonography while only 62.2% of the lesions were identified using radiography.

Hinz noted that in 62 instances, ultrasonographic and radiographic findings correlated but surgical findings did not. In 27 of these, ultrasonography and radiography both had false positive findings.

On ultrasonography, erosions of the articular cartilage and subchondral bone unit show up as irregularities and defects within the smooth subchondral bone surface. Radiographs more frequently missed these lesions, a finding consistent with other studies, the researchers noted.

Hinz noted that a high level of ultrasonographic proficiency and specialized equipment is required for an accurate interpretation of findings, especially when evaluating complex joints. For larger joints, the team advised veterinarians use medium-frequency transducers to allow deeper penetration.

"Scanning joints with confidence takes some practice but it is well worth the effort," said Hinz. "It is well-tolerated by the patient, is noninvasive, and provides conclusive information about the condition of articular surfaces."

The study, "Comparison of the accuracy of radiography and ultrasonography for detection of articular lesions in horses," was published in October 2011 in Veterinary Surgery. The abstract is available online.

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