Abstract
Introduction
Dual-mobility bearings increase the stable range of motion of total hip arthroplasty (THA) but are limited by the mechanical effects of a large diameter metal on polyethylene bearing which may cause high rates of wear from the surfaces of the polyethylene bearing and the head-stem taper. Improved polyethylene (PE) has reduced concern over bearing wear but the effects on the taper junction are unknown.
We aimed to better understand the effect of dual mobility bearings on fretting-corrosion damage to the taper junction by comparison to standard bearings.
Materials and Methods
We collected and analysed retrieved hips of one design with either dual mobility (n= 39) or standard bearings (n=30). The bearing size in the dual mobility group was 42mm whereas in the standard bearing group it had a median of 36mm. Stem trunnions had V40 tapers. Time of implantation and body mass index were comparable between the two groups.
Fretting and corrosion at the stem trunnions was quantified by: 1) visual scoring and 2) surface profilometry.
Results
Corrosion and fretting of the head-stem taper junction was lower in the dual mobility group when compared to the standard group as measured by both visual scoring (p=0.0002) and surface profilometry to measure material loss (p<0.0001). We did not see black debris, characteristic of severe corrosion processes, at the male surfaces in the dual mobility group.
Discussion
In this study, visual damage at the male taper surfaces of dual mobility systems was less that that occurring at the male taper surfaces of standard articulating systems, measurements of wear rates were in agreements with the macroscopic evaluation.
Conclusions
The frictional torque on the head-stem taper junction may be reduced with the use of a dual-mobility system when compared to a standard bearing system.
