In this study the investigators sonicate the bearing components of the explanted hip prosthesis which allows highly sensitive detection of in vivo biofilms (qualitatively and quantitatively). The hip prosthesis bearing components are composed from different material. The purpose of this study is to analyse the resistance against biofilm adhesion of ceramic, metal and polyethylene prosthesis components through microbiologic analysis of sonicates.

The main reasons for hip prosthesis failure are aseptic loosening and periprosthetic joint infection (PJI). The real frequency of PJI is probably largely underestimated because of non-standardized definition criteria, diagnostic procedure, treatment algorithm and other confounders. Therefore, data from joint registries are not reflecting the frequency of PJI and can be misleading; particularly low-grade PJI can be frequently misdiagnosed as aseptic failure.

Microbiological analysis of sonicate has in comparison with joint aspirate significantly higher sensitivity and specificity, which allows better detection of low grade infection. With aspiration only free-floating, high metabolically active, planktonic form of bacteria could be collected. Contrarily, the less metabolically active bacteria are hidden under the biofilm can remain undetected.

Sonication of prosthetic material mechanically dislodge the biofilm from surface and expose the sessile bacteria for the microbiological analysis.

All foreign materials provoke biofilm formation however, different materials showed different resistance for biofilm adhesion.

In this study patients with PJI are undergoing standard one- or two- stage revision procedure of the hip. The removed bearing components will be sonicated and sent in microbiological analysis. The ceramic, metal and polyethylene prosthesis components will undergo qualitative and quantitative microbiological analysis. The materials will be compared regarding to the presence of biofilm formation.

Inclusion Criteria:

• Subject must be aged 18 or more.
• Subject must be scheduled to undergo an explanation of the hip endoprosthesis during the 1- or 2- stage revision procedure because of the septic or mechanical indication.
• Subject must personally sign and date the informed consent document indicating that the subject has been informed of all pertinent aspects of the study.

Exclusion Criteria:

• Patient not scheduled for the index Operation procedure with removal of hip endoprosthesis

Patients ≥18 y, undergoing hip prosthesis explantation for infection or mechanical (aseptic) reason.