Friday, September 20, 2013

Cyanoacrylate Microbial Sealant and the Prevalence of Positive Cultures in Revision Shoulder Arthroplasty

Cyanoacrylate Microbial Sealant May Reduce the Prevalence of Positive Cultures in Revision Shoulder Arthroplasty May Reduce the Prevalence of Positive Cultures in Revision Shoulder Arthroplasty

Cyanoacrylate-based, microbial sealant is an adhesive skin barrier designed to prevent bacterial contamination in surgical wounds. These authors evaluated whether cyanoacrylate microbial sealant reduced the positive intraoperative culture rates in revision shoulder arthroplasty.
They retrospectively reviewed 86 patients who had unilateral revision shoulder arthroplasty between January 2005 and December 2011 and then excluded 31 patients with a history of previous shoulder infection, clinical signs of preoperative infection, and the lack of intraoperative cultures.

This left 55 patients presumed to be uninfected at the time of the revision procedures. The indications for surgery included glenoid component loosening (n = 14), fracture sequelae (n = 14), rotator cuff deficiency (n = 10), glenoid arthritis (n = six), prosthetic dislocation (n = six), and stiffness (n = five). All patients received preoperative antimicrobial prophylaxis. 

Stopping right there for a minute, while we do not know the number of primary arthroplasties from which these revisions came, it is again noted that glenoid component failure remains a leading cause of presumed "aseptic" failure in shoulder arthroplasty.

18 of these cases underwent revisions to hemiarthroplasties, seven underwent revisions to anatomic total shoulder arthroplasties, and 30 underwent revisions to reverse total shoulder arthroplasties.
A change in the authors practice was made in September 2009 after which cyanoacrylate microbial sealant was used in addition to the surgeon's usual prep and drape in all revision cases. As a result of this change 40 shoulders (Group SP) underwent standard, alcohol-based preparation with adhesive iodine-barrier drapes placed over the entire shoulder and axilla, covering all the skin. 15 shoulders (Group MS) had applications of cyanoacrylate microbial sealant in addition to the alcohol-based preparation and adhesive iodine-barrier drapes received in Group SP. 

It is of note that these groups were not concurrent or randomized, so it is unclear whether they are comparable.

Intraoperative aerobic and anaerobic deep tissue cultures were taken from tissue lining the prosthesis.
The prevalence of cases with positive cultures was 18% (seven of 40) in Group SP compared with 7% (one of 15) in Group MS. Of note is that these cultures were positive in spite of intravenous antibiotic prophylaxis.

The authors do not indicate if they used modern methods for the detection of Priopionibacterium. Thus it is possible that the presence of this organism went undetected in some of the cases. Nevertheless of the shoulders with positive cultures, 6 of 8 were positive for Priopionibacterium.  The prevalence of positive, anaerobic Propionibacterium acnes cultures was 13% in Group SP compared with 7% in Group MS. It is clear that Propionibacterium are often present in such surgical fields.

In spite of their reporting that the p values did not come close to statistical significance (Fisher's exact test comparing positive culture rate for the two groups = .4231), the authors suggest that "the application of a cyanoacrylate microbial sealant may reduce the prevalence of positive cultures and thereby subsequent infections in revision shoulder arthroplasties". The basis for this statement is unclear.

At this point there does not appear to be good evidence supporting the use of the sealant. It is important to recognize that the most likely source of Propionibacterium is the cut edge of the incision, so that changing the skin draping may not be an effective approach.

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