Sunday, August 24, 2014

Failed glenoid component, lessons and questions

Our readers are aware that the glenoid component is the 
 in total shoulder arthroplasty.

Recently we were consulted on a patient from elsewhere whose post operative x-ray taken two years ago had this appearance
Here's a closer view of his glenoid fixation showing lucency's around the pegs of the glenoid component
The dark areas between the pegs and the bone in postoperative films are filled with fluid and/or soft tissue so that the component is not well fixed in the bone. As shown in an earlier post, we use a CO2 jet to remove fluid and soft tissue from the bone/cement interface. This enables pressurized cement to completely fill the space between the pegs and the bone, optimizing component fixation. This practice has essentially eliminated the issue of postoperative periprosthetic lucent lines.

Two years later, we met this shoulder for the first time. At the time of presentation to us for consultation the patient had been experiencing increasing pain in the shoulder since his original total shoulder arthroplasty. The x-rays taken at our first visit are shown below. Note the osteolysis around the glenoid component pegs on the AP view
 and the 'watermelon seed' of cement between the glenoid component and the bone posteriorly on the axillary view. The problem with this 'watermelon seed' is shown in this prior post.
 After discussion of the alternatives and considering the possibility of Propionibacterium infection, the patient desired to have a revision with complete prosthesis removal, harvest of specimens for culture, thorough debridement, insertion of a new prosthesis with Vancomycin allograft fixation, and the red antibiotic protocol.

At surgery, the joint fluid was turbid and the glenoid component was completely loose; the 'watermelon seed' was floating free in the joint space. Removal of the trabecular metal stem was very difficult because of bone ingrowth; multiple osteotomies around the component were required. A modified bodice repair was needed to close the humeral osteotomies made for component removal. A glenoid component was not used in the reconstruction.

Note that bone ingrowth is not necessary for humeral component fixation and greatly complicates revision.

The postoperative films are shown below.

Immediate assisted range of motion exercises were started after surgery. IV antibiotics will be continued for 6 weeks and transitioned to oral antibiotics if the cultures (which are now pending) become positive. 

The patient reports that the shoulder is already more comfortable than in the prior two years. We are hopeful.

Consultation for those who live a distance away from Seattle.

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