Tuesday, March 25, 2014

Can intraoperative frozen sections help identify Propionibacterium at the time of revision shoulder arthroplasty?

Sensitivity of Frozen Section Histology for IdentifyingPropionibacterium acnes Infections in Revision Shoulder Arthroplasty

We have pointed out previously that Propioibactrium is often recovered from failed shoulder arthroplasties.  This is a facultative anaerobic bacterium that can grow in the presence as well as in the absence of air. It has a strong ability to form a biofilm on implants in which it can persist for many years and in which it is protected from the action of antibiotics.

We have also pointed out that (1) the source of these Propionibacteriuim is likely to be the dermal glands that are necessarily transected with shoulder skin incisions and (2) that special culturing protocols are necessary for detecting the presence of this organism.

These authors sought to determine the sensitivity of frozen section histology in identifying patients with Propionibacterium acnes infection during revision total shoulder arthroplasty.

The patients were retrospectively selected from a database of all patients who underwent revision shoulder arthroplasty between 2005 and 2012. All cases with periprosthetic joint infection were identified and were compared with a group of aseptic revisions.

Shoulders were considered infected if they had two or more positive cultures. Infected patients were subsequently divided into P. acnes infections and infections from other organisms to create three groups: (1) the non-infection group (n=15), (2) the P. acnes infection group (n=18), and (3) the other infection group (n=12).
The histologic diagnosis was determined by one pathologist for each of the four different thresholds:

5 or more polymorphonuclear leukocytes per high-power field in each of 3 or more fields
5 or more polymorphonuclear leukocytes per high-power field in each of 5 or more fields
10 or more polymorphonuclear leukocytes per high-power field in each of 5 or more fields
23 polymorphonuclear leukocytes in 10 high-power fields
They also searched for a new threshold based on a retrospective analysis.

Each of these thresholds were 100% specific for infection.

They found that a new threshold - a total of 10 polymorphonuclear leukocytes in 5 high-power fields (400×) -  provided a sensitivity of 72%.


Frozen sections are useful if positive, irrespective of the threshold applied: in this retrospective study,  if there were 5 or more polymorphonuclear leukocytes per high-power field in each of 3 or more fields it was likely that bacteria were present. It is important to note that this "new threshold" was derived from a retrospective analysis, it has yet to be tested prospectively. Even applying the to the data set from which it was derived resulted in missing over 1/4 of the cases of Priopionibacterium. If frozen sections are negative, infection cannot be excluded no matter what threshold is set.

In our revision arthroplasty practice we do not use frozen sections. We harvest 5 non-fluid cultures before prophylactic antibiotics are administered and send them for Propionibacterium-specific cultures. In most cases we perform a single stage prosthesis exchange and vigorous surgical debridement. The patient is put on either oral Augmentin or IV Ceftriaxone+Vancomycin (depending on the presence of osteolysis, component loosening, membrane formation and other know associates of infection) until the culture results are finalized at three weeks (not two as in the study reviewed here).

Our approach is outlined in some detail here.


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