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REFERENCES:1Nassut, R.; Mollenhauer, I.; Klingbeil H. In: Biomedizinische Technik, H. 51, S. 103-109B, 2006.FiguresPoster: 76Influence of Tilting of Ceramic Liners on Their in-Vivo SafetyINTRODUCTION:*Thomas Pandorf - CeramTec AG - Plochingen, Germany*Email: t.pandorf@ceramtec.decLooking at the design developments of hip prostheses, several tendencies can be observed.,especially for the acetabular components. The mean patient age decreases more and more, incontrast the patients’ requirements regarding performance are increasing. This implicates thatnot only the mechanical safety has to be ensured but also the requirements concerning the rangeof motion (ROM) necessary for the patients’ various activities. Besides design specific changes,this can be reached by increasing the bearing diameter. Because the anatomical conditions donot allow for an arbitrary increase of the implant size, the tendency to lower the wall thicknessof the acetabular components can be observed, especially for the metal shells. Furthermore, thebone density of young patients is in general higher leading to an increase in bone stiffnesscompared to the average patient in the times of Charnley. This results in increased press-fitforces on the metal shell during and after impaction, leading to large deformations of the metalshells in some cases.Hence, experience shows that intraoperatively difficulties arise to implant the ceramic insertsproperly in the metal shell which has already been impacted in the human bone. Due to thementioned large deformation of the metal shell, it is more difficult for the surgeon to implantthe insert correctly. As a result, a tilted insert is subjected to line or point loading which maylead to chip-offs or even fracture [1].As mentioned there, impacting of an insert starting from tilted position achieved by manuallyinsertion, is only possible above a certain tilting angle of several degree. Inserts tilted aroundless than this certain angle tend to self-centering during impaction as can be affirmed from ourown lab experience.Nevertheless surgeons report chip-offs during impaction of inserts even after carefullychecking the proper and untilted seating. Beside other hypotheses the presence of soft tissuedisturbing the taper-locking surfaces of the connected parts was found as a possible reason forfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]