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We investigated the period from first stage surgery to the day when CRP became negative, andto the day of second stage surgery. The incidence of recurrence of infection after revision THAwas investigated.ResultsThe average period to negative CRP was 25 days, and that to the second stage surgery was 64days. There has been no recurrent infection until now.DiscussionThe antibiotics-impregnated cement spacer for the treatment of periprosthetic infection wasintroduced around 1990, and success rate of this technique was reported to exceed 90%. In ourseries, we experienced no recurrence of infection in spite of containing 3 MRSA cases and 2CNS cases. The advantages of the antibiotics-impregnated cement spacer were to avoid softtissue shortening and to allow patient to walk without weight bearing. We concluded that twostagerevision technique with antibiotics-impregnated cement spacer is an effective treatmentfor periprosFriday, October 8, 2010, 11:00-11:50Session B11: Knee MechanicsInfluence of Activity on the Primary Stability of Three Designs ofCementless Tibial Tray*Mark Taylor - University of Southampton - Southampton, United Kingdom*Email: mtaylor@soton.ac.ukIntroduction: Cementless tibial fixation has been used for over 30 years. There are severalpotential advantages including preservation of bone stock and ease of revision. Moreimportantly, for young active patients there is the potential for increased longevity of fixation.However, the clinical results have been variable, with reports of extensive radiolucent lines,rapid early migration and aseptic loosening. Problems appear to stem from a failure to becomesufficiently osseointegrated, which in turn suggests a lack of primary stability. In order toachieve boney ingrowth, interface micromotions should be less than 50 microns, whereasfibrous tissue formation is known to occur if micrmotions are in excess of 150 microns. Thedegree of micromotion at the bone-implant interface are dependent on the kinematics andkinetics of the replaced joint. Finite element analyses has been used to assess primary stability,however, it is becoming increasing difficult to differentiate performance . The aim of this studywas too examine the micromotion for a variety of different activities for three commerciallyavailable tibial tray designs.Methods: A finite element model of the implanted proximal tibia was generated form CT scansof a 72 year old male and material properties were assigned based on the Hounsfield units.Three tray designs were evaluated: LCS, Duofix and Sigma (DePuy Inc, Warsaw USA). Theimplants were assumed to be debonded, with a coefficient of friction of 0.4 applied to thebone-implant interface except for the porous coated region of the Duofix design, which wasfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]