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.

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Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

Shoulder arthritis - x-ray appearance (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).

This is a non-commercial site, the purpose of which is education, consistent with "Fair Use" as defined in Title 17 of the U.S. Code.          

Note that author has no financial relationships with any orthopaedic companies.

What might be learned from this failed total shoulder?

A middle aged patient presented with pain and clicking in the shoulder after a prior total shoulder joint replacement. 

The x-ray below shows that a large sized stem incarcerated in the humeral diaphysis preventing full seating of the humeral component. As a result the humeral head rested on the superior aspect of the glenoid giving rise to rocking horse loosening of the glenoid component. The keeled glenoid component had been inserted with a lot of cement so that when the loose component was removed a large defect in the glenoid bone was left. 

Rocking horse loosening from eccentric loading is a common contributor to glenoid component failure.  A smaller stem fully inserted and fixed with impaction grafting may have avoided humeral component malpositioning. Using a pegged glenoid component inserted with minimal cement may have reduced the amount of glenoid bone loss.
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You may be interested in some of our most visited web pages   arthritis, total shoulder, ream and run, reverse total shoulder, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'