Tuesday, September 20, 2016

Acute failure of a hybrid glenoid component

Acute Failure of a Glenoid Component in Anatomic Shoulder Arthroplasty.

The authors remind us that glenoid loosening is the most common cause of failure in primary total shoulder arthroplasty and often occurs years after the initial surgery. In this case report, they present an unrecognized acute failure of a cemented hybrid glenoid component.

The patient was a 65-year-old man with persistent right shoulder pain and severely restricted range of motion approximately 10 months after a primary anatomic total shoulder performed for longstanding severe osteoarthritis with an intact cuff. The shoulder system was used for the index procedure included pegged, caged glenoid.

A CT arthrogram was ordered to evaluate if there was a rotator cuff tear but instead found that the glenoid component had dissociated and was sitting posterior to the humeral head .  The polyethylene glenoid component had disengaged from its metallic cage. One of the three metallic peg caps remained seated in the glenoid. 

Close inspection of the postoperative films, as early as those immediately following surgery in the postanesthesia care unit, confirmed that the glenoid had failed acutely.

At revision surgery, the glenoid component was retrieved from the posterior capsule. The component failure was seen to have occurred at the interface between one of the pegs and its metallic cap as well as at the cage component, which had disengaged from the polyethylene.

The authors point out that there have been prior recognized failures of this central cage locking mechanism. They suggest that this component requires “straight line” glenoid impaction, directly perpendicular to the face of the glenoid to prevent damage to the locking mechanism of the central peg as it engages the drilled hole. Failure to do so may disengage the central peg from the polyethylene.

Comment: This is points that each implant system has its particular features and that these need to be understood by the surgeon.

In our practice we use an all polyethylene component
our total shoulder arthroplasty is shown in this link.