UW Shoulder and Elbow Academy: Total shoulder arthroplasty complicated by rocking horse glenoid component loosening

A 70 year old patient presented to his surgeon with rheumatoid arthritis, loss of comfort and function in the right shoulder and these radiographs.

A total shoulder arthroplasty was performed using a stemless humeral component and a posteriorly augmented glenoid component. Early postoperative films are shown below.

After a year or two the patient was seen by a close colleague of ours who documented a history of progressive shoulder pain and stiffness, but no systemic signs and no history of injury. On examination the cuff muscles appeared strong and there was no evidence of instability, crepetance, or swelling.

Plain films showed evidence of glenoid component loosening and loss of bone from the medial humeral cortex.

The shoulder was evaluated arthroscopically with the findings of 11,000 WBC, 2500 RBC (87%PMN), negative cultures and a loose glenoid component.

CT scan confirmed glenoid loosening with severe osteolysis and evidence of component rocking in the superior and posterior direction.

The rocking horse mechanism for glenoid component loosening is described in this link.

It is uncertain whether an augmented glenoid component results in an increased loosening arm when the humeral component applies posteriorly directed loads to its rim.

At the time of revision, abundant synovitis and a massive glenoid defect were discovered. The loose glenoid component was removed.

Specimens were sent for culture and single stage revision to a stemmed hemiarthroplasty was performed. The glenoid was allografted. There was insufficient bone for fixation of another anatomic glenoid component or baseplate.