Quantification of the Field of View for Standard Lateral Arthroscopy of the Canine Shoulder.

Objective:  The aim of this study was to define the extent of the biceps tendon, subscapularis tendon, and cranial border of the medial glenohumeral ligament within the field of view during standard lateral shoulder arthroscopy in the dog. We also examine the effect of joint flexion on the field of view of the biceps tendon.

Study design:  This was a cadaveric study using 21 shoulders of large breed dogs. Each shoulder was explored with a 30-degree arthroscope using standard lateral ports. For each supporting structure, the margins within the arthroscopic field of view were marked with ink. In 11 shoulders, the distal margin of the biceps tendon was identified and marked first with the limb at a standing angle and then in flexion. The margins of the cranial border of the medial glenohumeral ligament were marked at the standing angle. In 10 additional shoulders, the margins of the subscapularis tendon were evaluated. Each joint was fully dissected and the portion of each stabilizing structure within the field of view was quantified.

Results:  Fifty-eight percent of the cranial border of the medial glenohumeral ligament was within the arthroscopic view. At a standing angle, 48% of the intra-articular length of the biceps tendon was within the arthroscopic view, compared to 63% with the limb flexed. Twenty percent of the subscapularis tendon was within the arthroscopic view.

Conclusion:  A significant portion of the biceps tendon and medial stabilizing structures of the canine shoulder are outside the field of view of arthroscopy through a standard lateral approach. The limitations of the arthroscopic field of view should be appreciated when evaluating the shoulder.