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*J. Philippe Kretzer - Laboratory of Biomechanics and Implant Research, University ofHeidelberg - Heidelberg, GermanySebastian Jaeger - Heidelberg University Hospital - Heidelberg, GermanyJoern Reinders - Laboratory of Biomechanics and Implant Research, University of Heidelberg -Heidelberg, GermanyEike Jakubowitz - Heidelberg University Hospital - Heidelberg, GermanyMarc Thomsen - DRK Klinik - Baden-Baden, GermanyRudi Bitsch - Heidelberg University Hospital - Heidelberg, GermanyIntroduction*Email: kretzer@implantatforschung.deInfection following total joint arthroplasty is a major and devastating complication. Afterremoval of the initial prosthesis, an antibiotic-impregnated cement spacer is inserted for approx.three months. Treatment is completed by a second stage revision arthroplasty.Up to now, spacers are produced from conventional bone cements that contain abrasive radioopaquesubstances like zirconium dioxide or barium sulphate. As long as spacer wear products(cement particles containing these hard substances) are not fully removed during the finalrevision surgery they may enter the articulating surfaces of the revision implant leading to thirdbody wear.In order to reduce the formation of reactive wear particles, a special cement (Copal® spacem)without abrasive zirconium dioxide or barium sulphate was developed.To date, no comparative tribological data for cement spacers have been published. Hence, wecarried out a study on the wear properties of Copal® spacem (with and without gentamicin) incomparison to conventional bone cements (Palacos® R and SmartSet® GHV).Material and MethodsIn order to assure reproducible forms of the femoral and tibial components, silicon rubbermoulds were produced and filled with the respective cement. Force-controlled simulation wascarried out on an AMTI knee simulator (Figure I). The test parameters were in accordance toISO 14243-1 with a 50% reduced axial force (partial weight bearing). Tests were carried out at37 °C in closed chambers filled with circulating calf serum. Tests were run for 240,000 cycles(representing the average step rate during 6-8 weeks) at a frequency of 1 Hz. For wear analysis,digital photographs of the spacer were taken at the beginning and at the end of the testingperiod. The areas of wear scars were measured by the means of a digital image processingsoftware.ResultsAt the end of wear test none of the cement specimens showed cracks or failures. Pairwisecomparison between the cement types revealed significant differences: Larger wear scars wereobserved for Copal® spacem compared to Copal® spacem + gentamicin (TUKEY test,p=0.025), whereas smaller wear scars were measured compared to Palacos® R (Figure 2),(TUKEY test, p