Validation of a new 2-D technique for radiographic wear measurement of cemented, highly cross-linked polyethylene acetabular cups

Abstract

HighlightsMean wear penetration error of the system was −0.002 mm and the precision was 0.055 mmAbove 0.25 mm penetration, wear direction error was within ±10° (median 1.15°)Good inter/intra observer agreement for clinical radiographsPenetration error equal to that of RSA for laboratory radiographs

Does Pelvic Orientation Influence Wear Measurement of the Acetabular Cup in Total Hip Arthroplasty—An Experimental Study

“…Derbyshire & Barkatali [10] reported for their customized software (programmed in C++ language) a mean error of −0.002 mm. The precision was 0.055 mm and the performed comparison tests with the RSA method showed similar accuracy.…”

“…Derbyshire and Barkatali [10] reported achieving a similar accuracy to RSA by using a customized 2D wear measurement tool. Bias, defined as the mean (SD) error of the simulated head penetration measurements, was about −0.002 mm (±0.028 mm), and precision was 0.055 mm for this 2D approach.…”

“…To validate tribological material behaviour under "real world" conditions, an in vivo detection of wear is necessary and required. There is a high priority and relevance for clinical acetabular cup wear measurements to assess common or new types of polymers that implant manufacturers introduce [10].…”

“…radiographs (2D wear ), and three-dimensional methods (3D wear ), including multi-plane radiographs (RSA) within a specialized radiological setup or a multilayer stack of radiographs (CT, MRI) of the artificial hip. However, modern 2D wear methods are developed and used to detect standard UHMWPE cups with a wear rate between 0.1 mm and 0.2 mm/year [10]. Teeter et al [15] reported 13 year results and found a wear rate of 0.08 ± 0.03 mm/year for a conventional polyethylene and of 0.04 ± 0.02 mm/year for a crosslinked polyethylene.…”

Correction of radiographic measurements of acetabular cup wear for variations in pelvis orientation

“…A true wear penetration of 0.4 mm, for instance, would be reduced by approximately 0.02 mm (same settings as above), which is below the accuracy of the best radiographic wear measurement systems. 26 In their theoretical study of a standard cup, Foss et al 8 also concluded that wear measurement errors caused by changes in pelvis orientation were likely to be small compared to other error sources. Notably, though, they did not determine wear from two, sequential displacement vectors (reference and follow-up) using the duo-radiographic technique.…”