Complimentary performance of sonication compared to an enhanced method of tissue processing in periprosthetic joint...

This retrospective single-centre study compares an enhanced periprosthetic tissue (PPT) culture method developed in our laboratory to sonication over a five-year period (2020-2024) to evaluate the advantages of each method and determine when explanted prostheses should be sent for sonication.

We analysed 686 PPT and 169 sonication samples from 164 patients with suspected periprosthetic joint infection (PJI) at the Frimley Health NHS Foundation Trust, comparing an enhanced method of processing PPT and sonication. PJI diagnosis was based on EBJIS criteria and MDT discussion.

Sonication demonstrated high sensitivity (95.7 %), specificity (91.92 %), and positive & negative predictive values (92.21 % & 95.55 % respectively). On the other hand, PPT cultures showed a sensitivity of 83.58 %, specificity of 87.062 %, and positive & negative predictive values of 86.59 % & 84.13 % respectively). However, sonication cultures showed higher contamination rates (mean 5.3 % vs 2.8 % for PPT), which declined over time. In 15 of 70 patient episode (21.4 %) results of PPT and sonication cultures were complimentary. With a pre-test PJI probability of 50 %, sonication yielded post-test probabilities of 92 % for positive results and 5 % for negative results.

Both sonication and enhanced PPT culture play vital roles in diagnosing PJI. When laboratory processes are monitored, improvements can be made with contamination rates. A multimodal diagnostic approach incorporating both methods and clinical context optimises accuracy, particularly in patients with moderate to high pre-test probability in the diagnosis of PJI.