Raman Spectroscopy Reveals Microparticles in Synovial Fluids of Patients With Suspected Implant-Related Complications

Prosthetic implant-associated inflammation and failure can be caused by bacterial infections and mechanical wear of the prosthesis. Currently, there is no diagnostic modality that allows simultaneous identification of both causes of implant failure. Here, we present a proof-of-principle study to assess whether Raman spectroscopy can be applied to diagnose implant failure. Synovial fluids from 10 patients with a clinical suspicion of implant-related complications were previously collected and cultured to determine the presence of bacteria. The presence of microparticles in these synovial fluids was assessed by Raman spectroscopy and verified by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). For control, the possibility to detect in vitro-cultured Staphylococcus aureus by Raman spectroscopy was investigated. Raman spectroscopy revealed that all 10 synovial fluid samples contained microparticles: eight contained microplastics (polyethylene, polypropylene, and polystyrene), and nine contained titanium dioxide nanoparticles (anatase and rutile) as verified by SEM-EDX. There was no clear difference in the microparticle content of synovial fluids with or without bacteria. Raman signals relating to individual bacteria and clusters of bacteria were detectable in in vitro cultures of S. aureus, but it was not possible to demonstrate the presence of bacteria in synovial fluids by Raman spectroscopy. Raman spectroscopy is a potential tool for characterizing microparticles in synovial fluids from patients with implant-related complications. This is of clinical relevance as these microparticles can cause joint inflammation. The identification of bacteria by Raman spectroscopy is feasible, but further research is needed before clinical implementation.