Introduction
-Periprosthetic joint infection (PJI) is a devastating complication of total joint arthroplasty (TJA)
- Therefore, accurate diagnosis of PJI is critical
- Diagnosis is largely guided by MSIS1
- However, evidence of bacterial infection can occur without meeting MSIS criteria2
- Positive bacterial growth on sonication of explanted prostheses has been reported in MSIS negative revisions
- Clinical significance and bacterial prevalence of positive sonication cultures in patients not meeting MSIS criteria remains unclear
Objective
- Investigate bacterial prevalence in MSIS negative, sonication positive vs. MSIS negative, sonication negative (aseptic) revisions
- Difference in CFU and/or bacterial prevalence between groups?
- Difference in bacterial prevalence over time?
Methods
- Retrospective case-control study
• Revision TJA performed at multicenter single institution between 2016-2025
• Required sonication of explanted prosthesis
- Exclusion Criteria:
• Inadequate workup to determine MSIS criteria
• Absent CFU values within electronic medical records (EMR)
• Sonication of antibiotic spacers
- Compared sonication cultures of PJI vs. aseptic revisions
• PJI diagnosis according to MSIS criteria1
- Primary outcome = bacterial prevalence
- Secondary outcome = temporal shift of PJI bacterial prevalence
- Stats:
• Bacterial prevalence: categorical comparisons with Fisher exact tests
• CFU: means compared with T-tests
Results
- Total of 1168 patients (318 PJI; 850 aseptic)
- Total of 354 positive sonication cultures (233 PJI; 121 aseptic)
- Positive sonication cultures in 14.2% of revisions classified as aseptic by MSIS criteria
- Organism-specific findings:
•MSSA, MRSA & GBS exclusive to PJI (p≤0.001)
•S. hominis exclusive to aseptic (p=0.01)
•P. acnes: only organism with statistically significant difference in mean CFU
•80.25 PJI vs 7.17 aseptic (p=0.002)
Conclusion
- Most frequent sonication culture organisms in prior literature (2013-2018): coagulase-negative staphylococci > MSSA/MRSA > Streptococcus spp.3
- Most frequent sonication culture organisms in current cohort (2016-2025): S. aureus* > coagulase-negative staphylococci ^
- Proportional increase in antibiotic resistant bacteria compared to prior studies3
- Temporal increase in S. aureus prevalence from sonication cultures suggests a shift in the microbiological cause of PJI
References
1.Parvizi J, Gehrke T. Definition of periprosthetic joint infection. J Arthroplasty. 2014;29(7):1331. doi:10.1016/j.arth.2014.03.009.
2.Kempthorne JT, Ailabouni R, Raniga S, Hammer D, Hooper G. Occult infection in aseptic joint loosening and the diagnostic role of implant sonication. Biomed Res Int. 2015;2015:946215. doi:10.1155/2015/946215.
3.Rothenberg AC, Wilson AE, Hayes JP, O’Malley MJ, Klatt BA. Sonication of arthroplasty implants improves accuracy of periprosthetic joint infection cultures. ClinOrthop Relat Res. 2017;475(7):1827-1836. doi:10.1007/s11999-017-5315-8.
