Friday, August 7, 2015

Painful total shoulder - how do we find out if the glenoid is loose?

Assessment of painful total shoulder arthroplasty using computed tomography arthrography

These authors attempted to assess the accuracy of computed tomography (CT) arthrography when evaluating glenoid component stability in the setting of postarthroplasty shoulder pain. They reviewed all patients presenting during a 5.5-year period to identify those with a painful shoulder arthroplasty more than 1 year after the index procedure, excluding reverse and hemiarthroplasty procedures, patients with a clearly identifiable cause for pain, such as rotator cuff insufficiency or gross component loosening as seen on plain radiographs, and those with culture-positive aspiration.

They identified 14 patients with suspected glenoid component loosening but inconclusive plain radiographs, each of which underwent a CT arthrogram that was evaluated for the presence or absence of contrast material underneath the polyethylene component. Glenoid component stability was evaluated direct arthroscopic visualization. At arthroscopy, soft tissue biopsy specimens were obtained for culture.

CT arthrography suggested glenoid component loosening in 8 of 14 patients (57.1%), and arthroscopic inspection identified loosening in 10 of 14 patients (71.4%). In 3 of 10 patients (30%), CTA suggested a well-fixed glenoid component, but gross loosening was identified during arthroscopy.

They concluded that the prediction of component stability based on the absence of contrast between the glenoid component and the bone-cement interface cannot be depended upon to evaluate the security of the component.

Comment: This study demonstrates that the diagnosis of glenoid component loosening and the diagnosis of Propionibacterium are difficult. Their results shown in table form are:

What is more worrisome is that five of these 14 patients had positive cultures for Priopionibacterium, including two where neither CT nor arthroscopy indicated loosening. It is not known how many samples were taken for culture in each case, but this is a high rate of positive cultures for sure.

Another difficulty is that 'loosening' can be a tough call - if the glenoid is grossly loose, it is obvious, but what if it wiggles just a little when we pull on the edges? How hard does one pull on the component to check?

Finally, how do we manage shoulders with positive cultures but no evidence of component loosening?

Many challenges remain in the evaluation and management of the painful shoulder arthroplasty. Stay tuned.


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