The occurrence of squeaking under wear testing standards for ceramic on ceramic total hip replacements

Ceramic on ceramic total hip replacement clinical reports may on occasion note a noise or squeaking. There is much debate on whether this is an actual concern, but some medical centres want to avoid any possible negative impact on the patients' wellbeing due to the noise generated. The aim of this study was to determine what sound frequencies can be picked up from hip testing standards for ceramic on ceramic under different lubrication conditions. The ISO-14242-1 (35° cup angle) and ISO-14242-4 (55° cup angle with a 4 mm translational mismatch) standards were used for testing with dry, water and serum lubrication conditions up to 10000 cycles. No sound was detected for water and serum conditions under standard walking (ISO-14242-1) testing. An audible noise with a frequency range of 0.4-0.8 kHz was picked up within 600 cycles under water and edge loading (ISO-14242-4) conditions. All dry testing produced a high pitch squeak when the frequency was higher than 2 kHz. One sample under dry edge loading conditions had an audible noise of 0.8 kHz, considered not as squeaking, as it was not high pitch. Dry testing for both, standard walking (ISO-14242-1) and edge loading (ISO-14242-4) conditions, which resulted in a high pitch noise, had a frequency range of 2-8 kHz and 5-9 kHz respectively. One sample tested with edge loading and serum produced a faint squeak noise after 6000 cycles with a frequency of 7 kHz. Edge loading due to ISO-14242-4 conditions had an increased torque which may be playing a role in increased friction leading to noise. Edge loading conditions were more prone to the generation of audible noise and squeaking whilst under lubricated conditions.