SAN FRANCISCO — Plain radiographs are an excellent first-line option for evaluating an individual with an injured shoulder, Dr. C. Benjamin Ma said at a conference on sports medicine sponsored by the University of California, San Francisco.
But the key is to be very specific about the views one wants.
For example, a simple order for anterior-posterior (AP) films of the shoulder will give an oblique and relatively uninformative view of the glenohumeral joint. That's because the shoulder blades are not flat. They're tilted forward, and as a result the glenohumeral joint is rotated toward the midline.
Instead, one should specify an AP view of the glenohumeral joint. The technician will know to tilt the patient slightly before shooting the film.
There are three things that Dr. Ma, of UCSF, said he wants to be able to visualize in the radiographs: the glenohumeral joint, the acromioclavicular joint, and the shape of the acromion.
In addition to the AP view of the glenohumeral joint, Dr. Ma will usually order an axillary lateral view, a supraspinatus outlet view, and an AP view of the acromioclavicular joint.
The axillary lateral film provides a good view of the humeral head sitting in the glenoid fossa. This joint has been likened to a golf ball sitting on a tee. When the shoulder is dislocated, the axillary lateral view allows one to determine whether the golf ball has fallen off the tee toward the front or toward the back.
Anterior dislocations are far more common than are posterior dislocations.
Finally, Dr. Ma said that a weight-bearing view of the shoulder can reveal otherwise hidden problems. He described one patient whom he suspected of having osteoarthritis, but nothing seemed amiss on the regular AP view of the glenohumeral joint. With the patient holding a 1-pound weight, however, it became obvious that there was direct bone-on-bone contact between the humeral head and the glenoid fossa.
To get this view, one should order an AP of the glenohumeral joint with the patient holding a 1-pound weight at 45–60 degrees of abduction.