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Saturday, October 9, 2010, 14:50-15:20Session A22: Tribology and Biomechanics in ArthroplastyIn Vitro and in Vivo Analysis of Squeaking Frequencies in Ceramic-on-Ceramic Total Hip ArthroplastyINTRODUCTION:*Sari-Ali El-Hadi - Hopital Pitie Salpetriere - Paris, FranceTodd Stewart - University of Leeds - Leeds, UKzonghmin jin - univesity of leeds - Leeds, UKJohn Fisher - university of Leeds - Leeds, UK*Email: hedisari@yahoo.frSqueaking after total hip replacement has been reported in up to 10% of patients. Someauthors proposed that sound emissions from squeaking hips result from resonance of one orother or both of the metal parts and not the bearing surfaces. There is no reported in vitro studyabout the squeaking frequencies under lubricated regime. The goal of the study was toreproduce the squeaking in vitro under lubricated conditions, and to compare the in vitrofrequencies to in vivo frequencies determined in a group of squeaking patients. The frequenciesmay help determining the responsible part of the noise.METHODS: Four patients, who underwent THR with a Ceramic-on-Ceramic THR(Trident®, Stryker®) presented a squeaking noise. The noise was recorded and analysed withacoustic software (FMaster®). In-vitro 3 alumina ceramic (Biolox Forte Ceramtec®) 32 mmdiameter (Ceramconcept®) components were tested using a PROSIM® hip friction simulator.The cup was positioned with a 75° abduction angle in order to achieve edge loading conditions.The backing and the cup liner were cut with a diamond saw, in order to avoid neck-headimpingement and dislocation in case of high cup abduction angles (Figure1). The head wasarticulated ± 10° at 1 Hz with a load of 2.5kN for a duration of 300 cycles. The motion wasalong the edge. Tests were conducted under lubricated conditions with 25% bovine serumwithout and with the addition of a 3 rd body alumina ceramic particle (200 µm thickness and 2mm length). Before hand, engineering blue was used in order to analyze the contact area and todetermine whether edge loading was achieved.RESULTS: Edge loading was obtained. In-vitro, no squeaking occurred under edge loadingconditions. However, with the addition of an alumina ceramic 3 rd body particle in the contactregion squeaking was obtained at the beginning of the tests and stopped after ~20 seconds(dominant frequency 2.6 kHz). In-vivo, recordings had a dominant frequency ranging between2.2 and 2.4 kHz.DISCUSSION: For the first time, squeaking was reproduced in vitro under lubricatedconditions. In-vitro noises followed edge loading and 3 rd body particles and despite, the severeconditions, squeaking was intermittent and difficult to reproduce. However, squeaking isprobably more difficult to reproduce because the cup was cut and the head was fixed in thesimulator, preventing vibration to occur. Squeaking noises of a similar frequency were recordedin-vitro and in-vivo. The lower frequency of squeaking recorded in-vivo, demonstrates apotential damping effect of the soft tissues. Therefore, the squeaking in the patients wasprobably related to the bearing surfaces and modified lubrication conditions that may be due toedge loading. Varnum et al reported recently (3) that all the revised squeaking patients had aneck-cup impingement with metal 3 rd body particles. These metallic wear particles maygenerate squeaking as shown in vitro. However, a larger cohort of squeaking patients is neededto confirm these results.file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]