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The shoulder is initially evaluated with conventional radiographs. Shoulder arthritides and other disease processes and their severity can be determined. However, the complex anatomy of the scapula and humerus is best demonstrated with CT.
There is normally 5 degrees of glenoid retroversion with respect to the scapular blade.
There is about 30 degrees of scapular anteversion with respect to the chest wall.
Preoperative CT in a patient status post reduction of posterior shoulder dislocation. Note normal alignment of scapula and glenoid.
Alterations of glenoid version and surface area/size occurs with various pathological processes. Insufficient bone stock can compromise glenoid component fixation. A severely eroded or worn glenoid cannot support a glenoid prosthesis. The orthopaedic surgeon must be aware of remaining glenoid bone stock to plan for potential eccentric reaming or excision of proud surfaces. Bone graft or customized glenoid prostheses may be required in more advanced cases.
Osteoarthritis typically results in posterior wear of the glenoid cartilage and subchondral bone (white arrow). In this patient, there is a large humeral head osteophyte (yellow arrow) and a loose body in the subscapularis bursa (red arrow).
Rheumatoid arthritis frequently results in diffuse glenoid bone loss with medial migration of the joint line to the base of the coracoid process (red arrow).
Massive rotator cuff tear with degenerative arthritis results in superior migration of the humeral head with wear of the superior glenoid and undersurface of the acromion. The glenoid becomes "acetabularized" with the coracoid and acromial arch functioning as the anterior and superior glenoid.