RELIABILITY OF A POWERPOINT METHOD FOR WEAR MEASUREMENT AFTER TOTAL HIP ARTHROPLASTY: A RETRIEVAL STUDY USING THREE-DIMENSIONAL LASER SCANS
The PowerPoint (2007 Version; Microsoft, Redmond, Wash) method is reported to have improved repeatability and reproducibility and is better able to detect differences in radiographs than previously established manual wear measurement methods. In this study, the PowerPoint method and the Dorr and Wan method were used to calculate the polyethylene liner wear volume. The wear volumes of retrieved polyethylene liners calculated from the 3D laser scanning method were compared with each method. This study hypothesized that the wear volume calculated by the PowerPoint method would correlate well with the wear volume measured by 3D laser scanning method. Between March 2004 and June 2009, 22 polyethylene liners from 20 patients were collected during revision Total hip arthroplasty(THA). Exclusion criteria included (1) missing an early primary postoperative radiograph or prerevision radiograph, (2) evidence of acetabular loosening or migration, (3) existence of significant mismatch between early primary postoperative radiograph and prerevision radiographs on vertical axis, and (4) liner wear-through. After applying these exclusion criteria, 17 retrieved polyethylene liners from 16 patients were included in this study. Wear volumes were calculated using the PowerPoint, the Dorr and Wan methods by 3 independent experienced observers who were unaware of the study design, and 3-dimensional (3D) laser scanning methods. Spearman correlation coefficients for wear volume results indicated strong correlations between the PowerPoint and 3D laser scanning methods (range, 0.89–0.93). On the other hand, Spearman correlation analysis revealed only moderate correlations between the Dorr and Wan and 3D laser scanning methods (range, 0.67–0.77). The PowerPoint method is an efficient tool for the sequential radiologic follow-up of patients after THA. The PowerPoint method can be used to monitor linear wear after THA and could serve as an alternative method when computerized methods are not available.