title: Vibration transfer in the ball-stem contact interface of artificial hips.
abstract: Audible squeaking has put the reputation of ceramic bearings for total hip replacements into question. Inter-articular friction induces vibrations in the ceramic head which are transferred through the head-taper interface to the femoral stem. If excited to sufficient amplitudes, squeaking can be emitted by the stem. Hence, the damping and amplification properties of this interface have a crucial influence on stem vibrations. The aim of this study was to determine the vibration transfer behavior between the head and the taper of a femoral stem and its dependence on the assembly force, in order to assess its influence on the development of audible squeaking. A ceramic head was assembled on a titanium femoral stem taper with high and low forces. Frequency response functions characterizing the head-stem interface were determined experimentally. The interface demonstrated negligible influence on vibration transfer in the squeaking frequency range (1-5 kHz). However its damping effect in lower and higher frequency ranges was significant and some areas of amplification were also found. Although squeaking vibration was not influenced by the particular interface studied, the method established can be utilized to trace taper designs with dynamic properties that decrease the susceptibility to squeaking.
authors.affiliation: TUHH - Hamburg University of Technology, Institute of Biomechanics, Denickestrasse 15, 21073 Hamburg, Germany. hothan@tuhh.de
authors.forename: Arne
authors.initials: A
authors.lastname: Hothan
authors.forename: Kathrin
authors.initials: K
authors.lastname: Lewerenz
authors.forename: Cornelius
authors.initials: C
authors.lastname: Weiss
authors.forename: Norbert
authors.initials: N
authors.lastname: Hoffmann
authors.forename: Michael
authors.initials: M
authors.lastname: Morlock
authors.forename: Gerd
authors.initials: G
authors.lastname: Huber
mesh_terms: D005269:Femur; D006622:Hip Prosthesis; D011474:Prosthesis Design / Q000295:instrumentation / Q000379:methods*; D013016:Sound; D013499:Surface Properties; D014732:Vibration
keywords: Eigenfrequency; Hip; Squeaking; Transfer; Vibration