This 65 year old male patient who fell 10 to 12 feet onto his left shoulder six months ago and his shoulder has been hurting ever since. He has difficulty sleeping on his shoulder and has pain on abduction of the shoulder.
When radiographing the shoulder, a minimum of three views should be obtained: internal rotation, external rotation, and baby arm (abduction view). It is vital that the upper lung fields to include the lung apex be visualized to rule out any possibility of a Pancoast tumor or reinfection apical tuberculosis.
This patient has advanced acromioclavicular joint arthrosis with joint space narrowing and osteophyte formation crossing the joint space. The glenohumeral articulation is normal. Note that the subacromial space is severely compromised with the humeral head almost obliterating the subacromial space. This is best seen on the external rotation view since you can observe on the internal rotation view the subacromial space does not look anywhere nearly as greatly compromised.
This patient’s plain film radiographic findings support the diagnosis of a complete chronic rotator cuff tear with retraction of the distal attachment of the rotator cuff. The unopposed action of the deltoid muscle will force the humeral head to glide cephalically and severely narrow the subacromial space. I suspect this rotator cuff tear has been present a long period of time and on MRI you would see fatty infiltration in the cuff muscles representing disuse atrophy. The normal measurements for the acromial humeral joint space is on an average of 9 mm, the minimum measuring 7 mm and the maximum 11 mm. A measurement less than 7 mm is indicative of a rotator cuff tear. A measurement greater than 11 mm may indicate posttraumatic subluxation, dislocation, joint effusion, stroke, or brachial plexus lesions (drooping shoulder).
Reference Yochum & Rowe, Essentials of Skeletal Radiology, Chapter 2 Measurements of Skeletal Radiology, Lippincott, Williams and Wilkins, 2005.