Is sonication of antibiotic-loaded cement spacers useful in two-stage revision of prosthetic joint infection?

Background: In a two-stage exchange protocol for prosthetic joint infection (PJI), bacteria surviving over the antibiotic-loaded cement spacers may cause the persistence of infection with renewed clinical symptoms following the surgery. Culture after sonication of removed prosthesis is more sensitive than conventional periprosthetic tissue culture for the microbiological diagnosis of PJI. The aim of this study was to assess whether sonication of the spacer at the time of the second-stage procedure may improve the diagnosis of persistent PJI.

Methods: We evaluated by microbiological culture the sonication fluid from 222 cement spacers implanted in a two-stage exchange protocol in 157 patients affected by PJI. A mean of 1.3 (range, 1-4) spacer per patient was performed.

Results: In 53 out of 222 spacers analyzed infection was confirmed according to the MSIS criteria. In 22 cases the infection was confirmed by both cultures on periprosthetic tissue and on sonication fluid from the spacers. In 23 cases persistent PJI was identified because of only cultures of periprosthetic tissue and 8 because of results obtained after spacer sonication. The sensitivity of periprosthetic tissue cultures was higher than that of cultures performed on sonication fluid (84.9% vs 56.6%, p < .001).

Conclusions: Even though sonication of cement spacers has performances inferior than those reported for prosthesis, it can be considered a complementary method to unravel persistent infection during a two-stage exchange protocol for PJI.