Monday, July 16, 2018

Failed total shoulder: infected?

A patient presented to us one year after having had a left total shoulder using this prosthesis.

The patient experienced pain and stiffness since surgery. The patient has also had chronic swelling and a draining sinus. 

The patient had had two limited I&D's by the original surgeon to drain what was thought to be hematoma. All cultures were negative. The patient  was unable to use the arm for daily activities.
The patient had completed IV antibiotic for a short course of 5 days and an oral course of Keflex and doxycyline. At the time of presentation, the arm had the appearance shown below. CBC, sed rate and CRP were all normal.

And this x-ray showing a fractured central metal peg with surrounding osteolysis. 

We revised this prosthesis by removing all components. The retrieved glenoid showed a fractured peg

The portion of the peg remaining in the glenoid had to be removed with a trephine.

Removal of the humeral component was difficult because of the tight diaphysial fit, the proximal ingrowth surface, and the fragile osteopenic metaphyseal bone.

A cement spacer was inserted with a plan 6 weeks of IV Ceftriaxone followed by oral Augmentin. The pathology report from surgery was as follows: 

Left shoulder capsule, excision: - Fibro-connective tissue with focal fibrin deposition, chronic inflammation, giant cell reaction, and rare neutrophils focally present.  Very few (<5/HPF) neutrophils are identified in one focal area directly underlying surface fibrin deposition. On retrospective review of the frozen section slides, these neutrophils are present, but do not reach numbers above 5/HPF.

At the time of the revision, 8 specimens were submitted for culture. The humeral stem had one colony only of coagulase negative Staph (SpCV 0.1), and one of three capsule specimens grew one colony only of Propionibacterium (SpPV 0.1). The rest showed no growth at 3 weeks.

Four months later, we removed the spacer and inserted a reverse total shoulder. In spite of the glenoid bone deficiency, robust fixation of the baseplate was achieved without bone grafting.

 Comment: When a shoulder arthroplasty fails, we consider
(1) removal/revision of loose components
(2) single stage removal/revision of all components
(3) insertion of an antibiotic spacer, possibly as the first step in a two-stage revision
(4) removal of all components without re-insertion

The decision among these options needs to be based on the information available before and at surgery. Often, as shown in this case, the history, the physical examination, and plain radiographs provide most of the needed information. The results of cultures obtained at the time of revision surgery does not become available in time to inform the surgical decision-making.

This case demonstrates (1) the ever present risk of infection in shoulder arthroplasty, (2) the susceptibility of fatigue fracture of a metal post, (3) the problems created by a tight press-fit bone ingrowth stem should prosthesis removal become necessary.

The potential for fatigue fracture of a hybrid post has been shown in a recent article

Five-year minimum clinical and radiographic outcomes of total shoulder arthroplasty using a hybrid glenoid component with a central porous titanium post.

Here is a radiograph from that article.

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