Computed Tomography and Positive Contrast Computed Tomographic Arthrography of the Canine Shoulder: Normal Anatomy and Effects of Limb Position on Visibility of Soft Tissue Structures

Abstract

Soft tissue injuries of the shoulder are an important cause of forelimb lameness in dogs. The objectives of this canine cadaver study were to describe normal anatomy of shoulder soft tissue structures using computed tomography (CT) and computed tomographic arthrography (CTA) and to determine the effects of positioning on visualization of shoulder soft tissue structures. Thirteen forelimbs were removed from eight canine cadavers. Two forelimbs were used for contrast dose optimization. For the remaining 11 forelimbs, shoulder CT and CTA were performed using three defined joint angles (140°, 90°, and 70°). For three forelimbs, CT and CTA images were compared with frozen anatomic sections to describe normal anatomy. Ten forelimbs were used for analysis of positioning effects. Soft tissue structures evaluated were the joint capsule, cartilage, ligaments, tendons, and muscles. A visual assessment score was assigned to each structure using a consensus of two observers. The range and mode of scores were calculated and compared for each modality and limb position. The shoulder joint capsule and medial and lateral glenohumeral ligaments were completely visible with CTA. All tendons and muscles were visualized in all the examinations except for the teres minor muscle tendon and the coracobrachialis muscle, which were not visible on all scans. Positioning the limb in an extended position significantly improved visualization of most soft tissue shoulder structures. Shoulder cartilage was best seen with CTA and with neutral or flexed positioning of the shoulder. Findings indicated that both CT and CTA are feasible imaging techniques for visualization of soft tissue structures of the canine shoulder.

Pilot study of the ultrasonographic examination of the intact and transected medial glenohumeral ligament in dogs

“…In human medicine, high‐field magnetic resonance arthrography (MRA) is the technique of choice to diagnose shoulder joint instability 10,11 . Benefits to MRA have also been demonstrated in veterinary medicine, 7,12–18 however this technique may not be widely available, could be cost prohibitive for some owners, and requires prolonged anesthesia. Computed tomographic arthrography (CTA) has also been considered as a method to visualize canine shoulder soft tissue structures and thus for the diagnosis of shoulder joint injuries 7,12–18 .…”

“…19 Arthroscopy is currently the gold standard technique to assess medial shoulder joint instability in dogs, as it provides direct information on the intra-articular structures, especially the medial glenohumeral ligament. 14 However, arthroscopy is invasive when used solely as a diagnostic tool and requires surgical planning. One alternative, noninvasive method to arthroscopy could be ultrasonography.…”

“…Computed tomographic arthrography (CTA) has also been considered as a method to visualize canine shoulder soft tissue structures and thus for the diagnosis of shoulder joint injuries. 7,[12][13][14][15][16][17][18] However, one recent study indicated that CTA alone was of limited diagnostic value to assess the medial glenohumeral ligament (sensitivity and specificity of 13% and 1%, respectively) and the subscapularis tendon. 19 Arthroscopy is currently the gold standard technique to assess medial shoulder joint instability in dogs, as it provides direct information on the intra-articular structures, especially the medial glenohumeral ligament.…”

“…Benefits to MRA have also been demonstrated in veterinary medicine, 7,12–18 however this technique may not be widely available, could be cost prohibitive for some owners, and requires prolonged anesthesia. Computed tomographic arthrography (CTA) has also been considered as a method to visualize canine shoulder soft tissue structures and thus for the diagnosis of shoulder joint injuries 7,12–18 . However, one recent study indicated that CTA alone was of limited diagnostic value to assess the medial glenohumeral ligament (sensitivity and specificity of 13% and 1%, respectively) and the subscapularis tendon 19 .…”

“…However, one recent study indicated that CTA alone was of limited diagnostic value to assess the medial glenohumeral ligament (sensitivity and specificity of 13% and 1%, respectively) and the subscapularis tendon 19 . Arthroscopy is currently the gold standard technique to assess medial shoulder joint instability in dogs, as it provides direct information on the intra‐articular structures, especially the medial glenohumeral ligament 14 . However, arthroscopy is invasive when used solely as a diagnostic tool and requires surgical planning.…”