Single explant requiring urgent analysis
Routine explant analysis
Explant analysis as part of the NRR
For surgeons and hospitals wishing to participate in the NRR project, we can provide cost free explant analysis.
Hip, knee and ankle arthroplasties
As standard, reports provide volumetric wear calculations and mapping of material loss. We provide other focused analysis if necessary – such as imaging of fixation surfaces – or as specifically requested.
Bearing surface analysis
Bearing surfaces are scanned using advanced coordinate measuring machines (CMMs). We have two CMMs in house, a Strato Apex 574 and a Legex 322, both from Mitutoyo. The CMMs have measurement accuracies of less than one micron (one thousandth of a millimetre). CMMs use a ruby probe to glide over the surfaces of components being analysed, continuously collecting data points.
Automated programmes allow the CMM to distinguish between the unworn parts of the bearing surfaces and determine the geometry of the parts when they left the factory. From this unworn area, the original geometry of the component can be reverse engineered. By comparing the actual surface (the post revision geometry) of a component to the original (as manufactured) surface, the magnitude of wear can be calculated and mapped. CMMs are capable of scanning most surfaces, including the more complicated geometries such as knee and ankle replacements. The accuracy of wear analysis is limited however by the ease with which the original geometry can be reverse engineered.
Taper junction analysis
The head/stem taper connection is of real concern in contemporary hip arthroplasty. Material shed from this interface appears to be particularly potent in provoking adverse tissue reactions in the host.
Similar to the bearing surfaces, we use a CMM to scan over the taper surfaces and identify the unworn regions of the components. From this unworn surface, the original, as manufactured geometry of the taper can be reverse engineered. This idealised geometry is then compared to the actual position of the material following explantation, allowing the amount of material loss to be estimated and plotted using bespoke software.
On site we have access to an SJ400 contacting profilometer from Mitutoyo. This machine employs a fine stylus to stroke over the surface under examination, providing measurements to sub-micron levels of accuracy. We also have access to a scanning electron microscope with EDAX capability to further investigate areas of interest.
High resolution light microscopy
ExplantLab has a Mitutoyo MF-A1010D light microscope capable of producing high resolution images at up to x1000 magnification. It has measurement accuracy that is the highest in its class, conforming to JIS B 7153. It can work in conjunction with iWorks software to convert captured data into three dimensional image reconstructions.
Analysis of component position
ExplantLab has an unparalleled database of measurements of three dimensional acetabular component orientation in hip replacement surgery. These results have been published in several high impact, peer reviewed articles. When provided with x-rays, we can give an indication of the relative position the surgeon placed a component and whether that was a factor in the performance of the prosthesis.
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