- The use of colony forming units (CFU) from sonication of prostheses has been shown to correlate with the diagnosis of PJI and serves as an adjunct in identifying PJI4

- Literature investigating the use of CFU in predicting failure following DAIR in lacking

Objective

- To identify a CFU value derived from sonication culture which is predictive of DAIR failure for the treatment of PJI

Methods

- 89 DAIR procedures performed at a multicenter single institution between 2016-2025 with sonication cultures obtained were included for analysis

- PJI diagnosis was established using MSIS 2018 consensus criteria

- Exclusion Criteria:

•septic revisions

•septic revisions not treated with DAIR

•inadequate workup to determine MSIS criteria

•absent CFU values within electronic medical records (EMR)

•sonication of antibiotic spacers

- Patients were stratified into cohorts based on CFU values:

•0-50 CFU

•51-100 CFU

•>100 CFU

- Failure was defined as requiring revision arthroplasty related to PJI or infection-related death within two years of surgery

- Kruskal-Wallis and Fisher's Exact tests were used for analyses between cohorts

- Receiver operating characteristic (ROC) analysis identified a CFU threshold predictive of failure

- Failure-free survival was compared using Kaplan-Meier analysis

Results

- No significant differences in baseline characteristics (Table 1)

- Twenty-two (25%) patients failed treatment

- ROC analysis revealed a CFU threshold 64 as most predictive of treatment failure

•AUC 0.60; Youden 23.27; sensitivity 59.09%; specificity 64.18%

- Kaplan Meier analysis revealed a trend of higher failure-free survival with lower CFU values (p = 0.17)

Conclusions

- This study highlights the association between CFU values derived from sonication culture and treatment failure following DAIR for PJI

- A threshold of 64 CFU was identified as predictive of failure

•AUC of 0.60 reflects limited discriminative ability

•CFU alone is unlikely to predict failure. Consider other variables.

- The use of CFU values may strengthen orthopaedic surgeons’ ability to predict treatment failure and adjust treatment accordingly

- Future studies with higher power are needed to determine whether a threshold of CFU can be used to predict DAIR failure

•Consider regression analysis controlling for age, BMI, comorbidities, microbial virulence, length of surgery

References

[1] Urish KL, Bullock AG, Kreger AM, et al. A Multicenter Study of Irrigation and Debridement in Total Knee Arthroplasty Periprosthetic Joint Infection: Treatment Failure Is High. Journal of Arthroplasty. 2018;33(4):1154-1159. doi:10.1016/j.arth.2017.11.029

[2] Kong CCW, Yee DKH, Cheung YC, et al. C-Reactive Protein as a Predictor of the Success of Debridement, Antibiotics and Implant Retention in Patients With Periprosthetic Joint Infection: A 17-year Retrospective Study of 2 Major Joint Arthroplasty Centers. Arthroplasty Today. 2025;35. doi:10.1016/j.artd.2025.101799

[3] Toh RX, Yeo ZN, Liow MHL, Yeo SJ, Lo NN, Chen JY. Debridement, Antibiotics, and Implant Retention in Periprosthetic Joint Infection: What Predicts Success or Failure? Journal of Arthroplasty. 2021;36(10):3562-3569. doi:10.1016/j.arth.2021.05.023

[4] Rothenberg AC, Wilson AE, Hayes JP, O’Malley MJ, Klatt BA. Sonication of Arthroplasty Implants Improves Accuracy of Periprosthetic Joint Infection Cultures. Clinical Orthopaedics and Related Research. 2017;475(7):1827-1836. doi:10.1007/s11999-017-5315-8