Ultrasound Examination of the Shoulder

"Shoulder lameness presents a diagnostic challenge to the practitioner," said Mary Beth Whitcomb, DVM, lecturer in surgical and radiological sciences at the University of California, Davis, in her presentation: "How to Perform a Complete Ultrasound Exam of the Equine Shoulder" during the 2003 American Association of Equine Practitioners convention. "Radiographs of this area have limited visibility, nuclear scintigraphy is expensive, and ultrasound is inexpensive and available to most practitioners.

"Examining the shoulder is indicated when there is swelling or trauma to the area and for forelimb lameness that's refractory (continues to be present) after a lower limb blocks," she recommended. "The shoulder is also a relatively common location for draining tracts. Ultrasound can be used to follow tracts into deeper tissues to identify foreign material, sequestered bone, or abscesses. It is important to remember that there may be multiple tracts and/or foreign bodies. Ultrasound can also be used to identify communication of these draining tracts with the synovial structures of the shoulder joint."

She said that a shoulder ultrasound examination should include evaluation of the following structures: Biceps tendon, bicipital bursa, humeral tubercles, scapula, tendons of attachment of the supraspinatus muscle and infraspinatus muscle and infraspinatus bursa.

Whitcomb noted that a practitioner gets the best images with the coat clipped using #40 blades, washed, and covered with ultrasound coupling gel. Alcohol can be used to improve contact in horses which can't be clipped. She noted that practitioners should use the highest frequency transducer available (preferably 7-10MHz), scanning at a depth of 4-6 cm. She described shoulder anatomy as seen on ultrasound in great detail for attendees.

Results of Shoulder Exams

Whitcomb described the results of 81 ultrasound shoulder examinations in 61 horses at UC Davis from 1999-2000. Forty-three horses (70.5%) had shoulder abnormalities. The most common was bicipital bursitis (inflammation of the bicipital bursa; 19 horses). Other pathologies included irregularities of the tubercles and scapular spine, tendinitis, osteomyelitis (bone inflammation), fractures, joint effusion, problems with tendon attachments, dystrophic mineralization (hardening) of damaged musculature (particularly the brachiocephalicus muscle belly), and osteophyte formation or degenerative joint disease.

"The results of this study strongly support the use of ultrasound to diagnose soft tissue and bony abnormalities of the entire shoulder region," Whitcomb stated. She also noted that lesions of the infraspinatus tendon and bursa had not previously been reported, but were found in this study.

Another use of ultrasound in the shoulder is to guide procedures such as analgesia injection and lavage (flushing) of infected synovial structures (bursa); she described several cases and procedures as examples.

"The technique for evaluation of the entire shoulder region is exceptionally well described by Tnibar, et al. 1 ," Whitcomb said. "The author highly recommends using the technique described in that study to perform ultrasound of the shoulder region. The addition of this technique to your practice may prove beneficial in diagnosing challenging upper forelimb lamenesses."

1 Tnibar, M.; Auer, J.A.; Bakkali, S. Ultrasonography of the equine shoulder: technique and normal appearance. Veterinary Radiology 1999; 40:44-47.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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