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Measurement of Angles of Abduction for Diagnosis of Shoulder Instability in Dogs Using Goniometry and Digital Image Analysis


Address reprint request to James L. Cook, DVM, PhD, Comparative Orthopaedic Laboratory, University of Missouri, 379 East Campus Drive, Columbia, MO 65211.


Objective— To compare abduction angles of shoulders with medial instability and unaffected shoulders in the same dogs and in age- and breed-matched dogs.

Study Design— Case–control study.

Animals— Dogs with medial instability of the shoulder (n=33) and 26 control dogs.

Methods— Dogs were sedated and positioned in lateral recumbency with both scapulas parallel to the table. With the elbow and shoulder in extension, the non-recumbent limb was maximally abducted and the angle between the scapular spine and lateral aspect of the brachium measured with a goniometer; a digital image was taken from the cranial aspect. Both techniques were performed in triplicate by 2 examiners. Mean abduction angles for each shoulder were determined from goniometric measurements and image analysis. Data were analyzed for significant differences between affected and unaffected shoulders, measurement techniques, and examiners. Strength of correlation between measurement techniques was determined.

Results— Mean abduction angles for shoulders with instability (53.7±4.7° goniometric, 51.2±4.9° image) were significantly (P<.001) larger than for all unaffected shoulders (32.6±2.0° goniometric, 30.9±2.3° image). In dogs diagnosed with instability, affected shoulders had significantly (P<.001) larger abduction angles than the contralateral (unaffected) shoulders. No significant differences were identified between right and left shoulders for control dogs, measurement techniques, or examiners. A strong (r=0.90) significant (P<.001) positive correlation between measurement techniques was noted.

Conclusions— Shoulder abduction angles measured under sedation provide objective data for diagnosis of shoulder instability in dogs. Shoulders with clinical and arthroscopic evidence of medial instability have significantly higher abduction angles than shoulders that are considered normal.

Clinical Relevance— Determination of shoulder abduction angles should be included in the diagnostic protocol for forelimb lameness assessment in dogs.

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