Abstract
Aim
Antibiotic loaded spacers are often used during a two-stage exchange for periprosthetic joint infections (PJI) both for its mechanical properties and as a means for local antibiotic delivery. The main goal of this study is to compare the rate of positive cultures during reimplantation with the use of different antibiotic loaded spacers: aminoglycoside only vs. combined glycopeptide/aminoglycoside vs. combined glycopeptide/carbapenem/aminoglycoside.
Method
We retrospectively evaluated every two-stage exchange procedures for infected hip/knee arthroplasty between 2012–2018. Microbiological findings in the first and second stage were registered as well as the type of spacer and antibiotic(s) used. Cases in whom no cultures were obtained during reimplantation and cases without sufficient data on antibiotic(s) used in cement spacers were excluded.
Results
Fifty-four cases were included (20THA and 34TKA), with an overall rate of positive cultures during reimplantation of 18.5% (10/54). The rate of positive cultures was statistically significant higher among spacers with monotherapy with aminoglycoside compared to spacers with combined antibiotic therapy- 35.7% (5/14) vs. 12.5% (5/40) respectively(p<0.05). Comparing those with combined glycopeptide/aminoglycoside (2/19) with triple glycopeptide/carbapenem/aminoglycoside therapy (3/21) there was no significant difference. Microorganisms present during the second stage were mostly staphylococci (coagulase-negative in four cases, S.aureus in three), Corynebacterium striatum, Enterococcus faecalis, C.albicans in one case each. In most cases (8/10), the isolated microorganism was the same as the first stage and was resistant to the antibiotic(s) used in the spacer in seven cases. Failure rate with the need for subsequent surgery was significantly higher at 60% (6/10) in cases with positive cultures at reimplantation compared to 4.5% (2/44) for those with negative cultures during reimplantation(p=0.0005).
Conclusions
It has recently been suggested that adding a glycopeptide to the spacer may be advantageous when compared to spacers with aminoglycoside monotherapy, as it will produce significantly lower rates of positive cultures during reimplantation which have been shown to increase the risk of subsequent failure as is the case in our study. Local unavailability of obtaining powder aminoglycosides has driven us to manually add high doses of vancomycin and meropenem to commercially available low-dose gentamicin cement in many of our spacers and they seem to to perform just as well as commercially available vancomycin/gentamicin combination. Although many other variables not considered in this study may influence the rate of positive cultures during the second stage (quality of initial debridement, systemic antibiotic therapy, etc.), we believe these results portrait a sufficiently accurate picture of clinical results with the use of different spacers.
