There has been widespread concern regarding the adverse tissue reactions after metal-on-metal (MoM) total hip replacements (THR). Concerns have also been expressed with mechanical wear from micromotion and fretting corrosion at the head/stem taper junction in total hip replacements. In order to understand the interface mechanism a study was undertaken in order to investigate the effect of surface finish and contact area associated with modular tapers in total hip replacements with a single combination of materials of modular tapers. An inverted hip replacement setup was used (ASTM F1875-98). 28 mm Cobalt Chrome (CoCr) femoral heads were coupled with either full length (standard) or reduced length (mini) 12/14 Titanium (Ti) stem tapers. These Ti stem tapers had either a rough or smooth surface finish whilst all the head tapers had a smooth surface finish. Wear and corrosion of taper surfaces were compared after samples were sinusoidally loaded between 0.1 kN and 3.1 kN for 10 million cycles at 4 Hz. In test 1 rough mini stem tapers were compared with rough standard stem tapers whilst in test 2 rough mini stem tapers were compared with smooth mini stem tapers. Surface parameters and profiles were measured before and after testing. Electrochemical static and dynamic corrosion tests were performed between rough mini stem tapers and smooth mini stem tapers under loaded and non-loaded conditions.Introduction:
Methods:
A recent PRCT failed to demonstrate superiority of HRA over THA at low speeds. Having seen HRA walk much faster, we wondered if faster walking speed might reveal larger differences. We therefore asked two simple questions: Does fast or uphill walking have an effect on the observed difference in gait between limbs implanted with one HRA and one THA? If there is a difference in gait between HRA and THA implanted legs, which is more normal?
There were 3 females and 6 males in the study group, who had a mean age of 67 (55–76) vs the control group 64 (53–82, p = 0.52). The BMIs of the two groups did not differ significantly (28 v 25, p = 0.11). The mean average oxford score of included patients was 44 (36–48). Radiographs of all subjects were examined to ensure that implanted components were well fixed. The mean time from THA operation to gait assessment was 4 years (1–17 yrs) and that for HRA was 6 years (0.7–10 yrs, p = 0.31). Subjects in this study had a mean TWS of 6.8 km/hr (5–9.5), and a mean TWI of 19 degrees (10–25 degrees).INTRODUCTION
METHODS
