Practical considerations for volumetric wear analysis of explanted hip arthroplasties

Abstract

ObjectivesWear debris released from bearing surfaces has been shown to provoke negative immune responses in the recipient. Excessive wear has been linked to early failure of prostheses. Analysis using coordinate measuring machines (CMMs) can provide estimates of total volumetric material loss of explanted prostheses and can help to understand device failure. The accuracy of volumetric testing has been debated, with some investigators stating that only protocols involving hundreds of thousands of measurement points are sufficient. We looked to examine this assumption and to apply the findings to the clinical arena. MethodsWe examined the effects on the calculated material loss from a ceramic femoral head when different CMM scanning parameters were used. Calculated wear volumes were compared with gold standard gravimetric tests in a blinded study. ResultsVarious scanning parameters including point pitch, maximum point to point distance, the number of scanning contours or the total number of points had no clinically relevant effect on volumetric wear calculations. Gravimetric testing showed that material loss can be calculated to provide clinically relevant degrees of accuracy. ConclusionsProsthetic surfaces can be analysed accurately and rapidly with currently available technologies. Given these results, we believe that routine analysis of explanted hip components would be a feasible and logical extension to National Joint Registries.Cite this article: Bone Joint Res 2014;3:60–8.

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

“…The third stage measures the entire surface and compares the data points with the perfect cone to determine any deviations, which represent wear depths, which are summed to calculate volumetric wear. The technique and validation process has been published previously (Bone et al, 2015;Langton et al, 2011b;Langton et al, 2014;Lord et al, 2011).…”

“…The difference between expected distance and measured distance gave linear wear depths. Once linear wear depths were known, the volumetric wear loss was calculated by multiplying the area of each gridsquare (with a maximum size of 1.57 mm) by the mean depths of the four measured points at its corners, as per the method described previously (Langton et al, 2014).…”

Application of a measuring arm with an integrated laser scanner in the analysis of the shape changes of forging instrumentation during production

“…For example, in works [1,17,18], the authors present the use of a coordinate measuring machine equipped with a contact measuring head for analyzing the volumetric wear parameters of the spherical surfaces of joint prostheses. In work [15], the authors expand the research concerning the analysis of the effect of the change of numerous scanning parameters, with the use of the contact scanning measuring head, whereas the authors of works [2,18,25] analyze the 'beneficial' effect of increasing the number of measurement points on the accuracy of the determined volumetric parameters.…”

Determining material loss from the femoral stem trunnion in hip arthroplasty using a coordinate measuring machine

“…As with the bearing surfaces, identification of the original surface is vital in order to accurately determine the volumetric wear. 18 The CMM programme requires the user to enter three variables in order to measure the trunnion. These variables are referenced against the coordinate system ( Figure 2).…”