Diagnosis of Persistent Infection in Prosthetic Two-Stage Exchange: Evaluation of the Effect of Sonication on Antibiotic Release from Bone Cement Spacers

Abstract

Introduction: When treating periprosthetic joint infection with a two-stage procedure, antibiotic-impregnated spacers can be used in the interval between prosthetic removal and reimplantation. In our experience, cultures of sonicated spacers are most often negative. The objective of the study was to assess whether that sonication causes an elution of antibiotics, leading to elevated antibiotic concentrations in the sonication fluid inhibiting bacterial growth and thus causing false-negative cultures.Methods: A prospective monocentric study was performed from September 2014 to March 2016. Inclusion criteria were a two-stage procedure for prosthetic infection and agreement of the patient to participate in the study. Spacers were made of gentamicin-containing cement to which tobramycin and vancomycin were added. Antibiotic concentrations in the sonication fluid were determined by mass-spectometry (LC-MS).Results: 30 patients were identified (15 hip and 14 knee and 1 ankle arthroplasties). No cases of culture positive sonicated spacer fluid were observed in our serie. In the sonication fluid median concentrations of 13.2µg/ml, 392 µg/ml and 16.6 µg/ml were detected for vancomycin, tobramycin and gentamicin, respectively. According to the European Committee on antimicrobial susceptibility testing (EUCAST), these concentrations released from cement spacer during sonication are higher than the minimal inhibitory concentrations (MICs) for most bacteria relevant in prosthetic joint infections.Conclusion:Spacer sonication cultures remained sterile in all of our cases. Elevated concentrations of antibiotics released during sonication could explain partly negative-cultured sonicated spacers. Indeed, the absence of antibiotic free interval during the two-stages can also contribute to false-negative spacers sonicated cultures.

Sonication Culture of Antimicrobial Agent-Containing Cement Spacers Removed during Staged Revisions for Arthroplasty Infection

“…However, other groups have reported different experiences with the ACS sonication. Some studies have shown that ACS sonicate fluid culture has low diagnostic yield and does not seem to add information beyond that provided by periprosthetic tissue cultures (14,20). Recently, Olsen et al reported no benefit of ACS sonicate fluid culture for the diagnosis of persistent infection or to predict outcomes of 41 subjects undergoing two-stage revision for PJI (15).…”

“…There is variation among studies regarding the duration of the antimicrobial release from the cement, but elution of antibiotics above the MIC of the infecting organism can be observed for several months (24). Some studies have reported the theoretical possibility that sonication of the spacer would leach antimicrobials out of the cement and result in inhibition of bacterial growth in culture (14,25). In some of our patients, the ACS was broken and processed in several pieces, which could potentially result in elution of sequestered antibiotic from the ACS, leading to negative-culture results (26).…”

“…In some of our patients, the ACS was broken and processed in several pieces, which could potentially result in elution of sequestered antibiotic from the ACS, leading to negative-culture results (26). Mariaux et al measured antimicrobial concentrations in ACS sonicate fluid showing levels at or above the MIC of common PJI pathogens (14). All ACS sonicate fluid cultures were negative, which was partially attributed to the presence of high antibiotic levels on the sonicate fluid.…”

“…These studies have included a limited number of patients using qualitative, semiquantitative, and quantitative ACS sonicate fluid culture, which makes the generalization of results difficult. New data from other authors raise questions regarding the utility of ACS sonicate fluid culture in the management of PJI (14,15). Further studies are needed to define the utility of ACS sonicate fluid culture in patients undergoing two-stage arthroplasty revision for PJI; hence, we report our experience with sonication of ACSs for the diagnosis of persistent infection.…”

Sonication fluid culture of antibiotic-loaded bone cement spacer has high accuracy to confirm eradication of infection before reimplantation of new prostheses

“…However, these studies only included a small number of participants using qualitative, semi-quantitative, and quantitative sonication spacer fluid culture, making these results hard to be widely generalized. Moreover, data from other authors reported different experiences with the value of sonication fluid culture of bone cement spacer in comparison with conventional intraoperative tissue culture in the management of recurrent and persistent PJI [ 20 , 21 ].…”