Objective: To determine the location and periarticular shoulder-muscle-abnormalities detected via orthopedic examinations and ultrasonography in ultra-endurance Alaskan sled-dogs, returned from an ultra-endurance sled-dog-race prior to finishing it.
Study design: Prospective clinical study.
Sample population: Sixty-four dogs (128 shoulders).
Methods: Dogs were classified based on clinical evidence of shoulder pain (SP versus control). Orthopedic examination findings, shoulder-abduction-angles (SAA; before- and during-anesthesia), and ultrasonographic findings were recorded. Relationships between orthopedic and ultrasonographic abnormalities were compared.
Results: Pain was elicited on 55/128 shoulders; 73 shoulders were pain-free. The most common painful structures included the biceps-tendon (BT; 30%), triceps-muscle (28%), and infraspinatus-muscle (25%). SAA ranged between 25° and 75° among groups, including pain-free shoulders in dogs without lameness. SAA was greater when dogs were anesthetized (46.3° ± 14.0° vs. 47.8° ± 12.0°; p = .03), especially in SP (mean increase of 3.49° ± 8.85°) compared to control (0.03° ± 7.71°, p = .009). Overall, 103 ultrasonographic abnormalities were detected (SP: 44; control: 59). The most common ultrasonographic abnormality was fluid surrounding the biceps tendon, similarly distributed between groups (SP: 39/44; control: 57/59). Most chronic ultrasonographic abnormalities affected the BT (15/103 abnormalities). No associations were detected between ultrasonographic abnormalities and clinical findings.
Conclusion: Shoulder abduction varied greatly and reached up to 75° in normal joints. Ultrasonographic shoulder-muscle abnormalities were common but did not seem associated with clinical findings.
Clinical significance: Interpretation of shoulder abduction warrants caution, and the presence of fluid around the BT may reflect a physiologic adaptation to racing, rather than a pathologic change in ultra-endurance Alaskan sled-dogs.
