A new approach for the Martell 3-D method of measuring polyethylene wear without requiring the cross-table lateral films

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 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 mu m, precision +/- 26 mu m) were similar to that obtained using the conventional A/P and cross-table lateral views (accuracy +/- 54 mu m, precision +/- 22 mu m), 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. (c) 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.