Abstract
Introduction
There is much current debate concerning wear and corrosion at the taper junctions of large head total hip replacements, particularly metal-on-metal hips. Is such damage a modern concern or has it always occurred in total hip replacement but not previously noted. To investigate this five explanted V40 Exeter femoral stems (Stryker Howmedica) were obtained following revision surgery at a single centre. In all cases, the 24–26 mm femoral heads were still attached.
Hypothesis
In conventional ‘small head’ modular hip prostheses such as the Exeter, negligible wear and corrosion is seen at the taper junction of explanted devices.
Methods
The articulating surface and the taper junction of each femoral heads was measured using a Mitutoyo LEGEX322 co-ordinate measuring machine (CMM) In each case a wear map was generated and the wear volume from the contact surface was calculated using a bespoke MATLAB program. The accuracy of such measurements has been previously shown to be within 0.5mm3.
Results
Wear analysis of the articulating surfaces found unworn surfaces with each femoral head having less than 1 mm3 volumetric wear. All tapers had minimal wear with volumetric wear of less than 0.5 mm3.
Discussion and Conclusion
The wear volumes measured fall within the CMM measuring accuracy of 0.5mm3. Furthermore all tapers showed low wear volumes indicating that the taper junction had functioned correctly and distributed the load across the length of the truneon.
Significance
This work adds to the growing evidence that taper problems in modern hip prostheses are associated with increasing head diameter and smaller taper dimensions
