Sonication is now widely recognised as a useful adjunct in diagnosing implant-associated infection. Yet its clinical impact increasingly depends not on whether it works in principle, but on whether results are comparable across settings. This post examines how sonication moved from proof of concept to routine use, and where its current limitations lie.
Summary
Sonication increases microbiological yield by accessing biofilm on implant surfaces
Comparative studies show added detection beyond tissue cultures alone
Diagnostic performance varies substantially between centres
A major current limitation is process variability rather than biological plausibility.
Why this matters
Accurate microbiological diagnosis underpins treatment decisions in periprosthetic joint infection and fracture-related infection. Low-virulence organisms and chronic presentations frequently challenge tissue culture sensitivity, creating uncertainty around pathogen identification and antibiotic selection.
Sonication was introduced to address this gap by targeting a bacterial compartment that routine tissue sampling accesses only indirectly. Its widespread uptake reflects this biological rationale, but its interpretive reliability depends on consistent execution.
What the evidence shows
Sonication accesses a biologically relevant compartment
In implant-associated infection, bacteria may reside in multiple compartments: periprosthetic tissue, the implant surface, and the bone–implant interface. The relative contribution of each varies with pathogen, chronicity, prior antibiotics, and host response (Trampuz & Zimmerli, 2005).
Low-virulence organisms such as coagulase-negative staphylococci and Cutibacterium acnes preferentially persist in biofilm on implant surfaces, where they may be underrepresented in tissue cultures (Trampuz et al., 2007). Sonication was developed to mechanically disrupt this biofilm and release bacteria into fluid for culture, complementing rather than replacing tissue sampling (Trampuz et al., 2007).
Comparative studies show increased yield but incomplete sensitivity
Multiple comparative studies and meta-analyses demonstrate that sonication fluid cultures detect pathogens missed by tissue cultures alone, particularly in chronic infections and in patients who received antibiotics prior to revision surgery (Zhai et al., 2014; Dudareva et al., 2018; Peng et al., 2023).
Across these studies, sonication shows moderate to good sensitivity and consistently high specificity. Importantly, the added yield is incremental rather than absolute. Sonication improves detection but does not eliminate false negatives, confirming its role as an adjunct rather than a standalone diagnostic test (Zhai et al., 2014; Dudareva et al., 2018).
Diagnostic performance varies widely between centres
Reported sensitivity and specificity of sonication vary substantially across studies. Differences are attributed to variation in processing protocols, sonication duration, transport conditions, culture techniques, and thresholds used to define positivity (Zhai et al., 2014; Alvarez-Otero et al., 2024).
This heterogeneity explains why identical implants processed in different laboratories may yield different results, even when biological conditions are similar. The limitation is therefore not whether sonication can work, but whether it is performed and interpreted consistently.
Guideline positioning reflects this variability
Clinical guidelines acknowledge the value of sonication while explicitly limiting its interpretive authority. The American Academy of Orthopaedic Surgeons includes sonication fluid cultures as an intraoperative diagnostic option alongside multiple tissue cultures and histopathology, without prioritising it over other modalities (AAOS, 2019).
Similarly, the EBJIS definition of periprosthetic joint infection accepts sonication as part of microbiological confirmation but emphasises that results must be interpreted in clinical context and not relied upon in isolation (McNally et al., 2021).
In fracture-related infection, the biological rationale for sonication is comparable, but the evidence base is smaller and more heterogeneous. As a result, sonication remains less consistently embedded in diagnostic pathways for FRI than for PJI (Onsea et al., 2018; Bellova et al., 2021).
Mechanisms behind the pattern
The current limitation of sonication is not biological plausibility but implementation. Once a diagnostic method moves beyond proof of concept, its value depends on reproducibility across real-world settings.
For sonication, variability arises from who performs the procedure, when it is requested, how implants are transported and processed, and how culture results are interpreted. These pathway-level factors shape diagnostic output as much as microbial behaviour itself.
Practical implications for clinical interpretation
Sonication adds access to a biofilm-associated bacterial compartment not reliably sampled by tissue cultures alone
A negative sonication result does not exclude infection, particularly in low-grade or chronic presentations
Differences in protocols can limit comparability of results between centres
Sonication should be interpreted as part of a diagnostic constellation rather than a decisive test
Common pitfalls
Treating sonication as a replacement for tissue sampling
Assuming uniform diagnostic performance across laboratories
Interpreting sonication results without clinical or histological context
Expecting sonication to overcome all limitations of microbiological culture
Closing note
Sonication has largely passed the stage of biological validation. Its remaining challenge is standardisation. Until processing pathways are aligned, the question is not whether sonication works, but whether its results mean the same thing in different clinical settings.
References
Trampuz A, Zimmerli W. Diagnosis and treatment of implant-associated infection. Swiss Med Wkly. 2005.
Trampuz A et al. Sonication of removed hip and knee prostheses for diagnosis of infection. N Engl J Med. 2007.
Zhai Z et al. Sonication fluid culture for diagnosis of prosthetic joint infection: a meta-analysis. J Clin Microbiol. 2014.
Dudareva M et al. The diagnosis of prosthetic joint infection: evaluation of sonication fluid culture in comparison with periprosthetic tissue culture. Clin Microbiol Infect. 2018.
Peng G et al. Diagnostic accuracy of sonication fluid culture for prosthetic joint infection: a systematic review and meta-analysis. J Orthop Surg Res. 2023.
Alvarez-Otero J et al. Variability in sonication processing protocols and its impact on diagnostic yield in prosthetic joint infection. Open Forum Infect Dis. 2024.
American Academy of Orthopaedic Surgeons. Clinical Practice Guideline on the Diagnosis and Prevention of Periprosthetic Joint Infections. AAOS. 2019.
McNally M et al. The EBJIS definition of periprosthetic joint infection. Bone Joint J. 2021.
Onsea J et al. Accuracy of tissue and sonication fluid sampling for the diagnosis of fracture-related infection: a systematic review and critical appraisal. J Bone Jt Infect. 2018.
Bellova P et al. Sonication in the diagnosis of fracture-related infections: a retrospective study on 230 retrieved implants. J Orthop Surg Res. 2021.