Establishing the diagnosis of implant-associated infections is often difficult, because of variable clinical presentations and lack of uniform diagnostic criteria. Sonication of removed orthopedic devices was shown to have superior sensitivity and specificity for infection. We evaluated the value of microcalorimetry as a quick and reliable tool in the diagnosis of infection in sonication fluid from removed implants. Between 10/2009 and 02/2010 we prospectively included all removed orthopaedic devices at our institution, which were subjected to sonication. Periprosthetic tissue cultures were performed as standard procedure. The removed device was sonicated in Ringer solution (40 kHz, 1 minute) and the resulting fluid was cultured and centrifuged (3000 × g, 10 minutes). The resulting pellet was resuspended in 3 ml tryptic soy broth for isothermal microcalorimetry (sensitivity of 0.25 μW). The detection time until increase of 20 μW was calculated. A 48-channel batch calorimeter (TA Instruments, New Castle, DE, USA) was used to measure the heat flow at 37°C controlled at 0.0001 °C.Objectives
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