Principles of shoulder arthroplasty

Patients with an intact rotator cuff and a humeral head that is centered in the glenoid fossa will benefit from both: a hemiarthroplasty and a total s houlder arthroplasty. However,the functional outcome following total should er arthroplasty is superior to that of hemiarthroplasty. Superior migration or mal-positioning of the humeral head in the anterior or posterior direct ion are generally associated with a maximum active flexion of 90 degrees an d a high rate of loosening of the glenoid component. Total shoulder arthrop lasty leads to superior results in patients with osteoarthritis and mal-pos itioning of the humeral head in the posterior direction. However, if the he ad can not be centralized in the glenoid fossa a significant risk of glenoi d loosening remains. A superior functional outcome of total shoulder arthroplasty in patients wi th rheumatoid arthritis can be observed. On the other hand inferior bone qu ality and a rotator cuff might lead to loosening of the glenoid component. Radiographic signs of glenoid loosening are frequently observed. However, t hese hardly require operative revisions. If a glenoid component can not be inserted, a bipolar or inverse prosthesis might be considered an alternativ e.