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Although cemented all polyethylene (PE) cups have been routinely used in total hip arthroplasty for decades, no computer-assisted method for measurement of radiographic wear has ever been specifically validated for these implants. Using a validated hip phantom model, AP plain hip radiographs were obtained consecutively for eight simulated wear positions. A version of Martell's Hip Analysis Suite software dedicated to all polyethylene sockets was used by three different examiners of varied experience. Bias (mean, standard deviation and 95% confidence interval limit), repeatability (standard deviation and 95% limit) and reproducibility (standard deviation and 95% limit) for two-dimensional wear measurements were assessed, as recommended by the current ASTM guidelines. Using this protocol, the dedicated software showed an overall mean bias of 0.089 ± 0.060 mm (mean ± SD), and 0.118 mm for 95% CI limit. Repeatability (intra examiner) standard deviation and 95% limit were respectively 0.106 mm and 0.292 mm. Reproducibility (inter examiner) standard deviation and 95% limit were respectively 0.112 mm and 0.308 mm. Martell Hip Analysis for all PE cemented cups is a reliable and low-cost instrument in the assessment of wear, despite being less precise than its original version dedicated to cementless components. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:???–???, 2015.

Due to the uneven and often inadequate quality of cross-table lateral hip radiographs, many radiographic studies of femoral head penetration into polyethylene in total hip arthroplasty are limited to the two-dimensional measurement of femoral head penetration using the A/P film only. We postulated that the use of two oblique frontal projections at 90 degrees to each other would improve the three-dimensional evaluation. Using an established hip phantom, the idealized accuracy and precision of the three-dimensional Martell method was evaluated, contrasting the standard A/P and cross-table lateral projections versus a pair of oblique projections by four independent readers. Accuracy and precision resulting from the use of two oblique projections (average accuracy +/-63 microm, precision +/-26 microm) were similar to that obtained using the conventional A/P and cross-table lateral views (accuracy +/-54 microm, precision +/-22 microm), though the results of the two oblique views were slightly more variable. These observations suggest that by using two oblique A/P projections, the major disadvantage of using the cross-table lateral films, namely the variable quality of the images, is avoided. Perhaps, therefore, the utility and availability of three-dimensional data in comparable clinical studies may be improved.