Reproducibility of radiographic assessment of femoral implant position after hip resurfacing arthroplasty: a pilot study.

To determine whether femoral implant position can be reproducibly measured on plain digital radiographs, we prospectively studied 40 patients after hip resurfacing arthroplasty. Three observers performed double blinded randomized analysis of calibrated digital radiographs meeting strict quality criteria. The implant stem-shaft angle and femoral anteversion angle were measured by the trapezoid method of axis determination using OsiriX software. The upper and lower offset and the anterior and posterior offset were measured. The statistical analysis was performed using Pearson correlation tests (intra-observer reproducibility) and Fisher F tests (inter-observer reproducibility). Intra-observer reproducibility was very good for all parameters and all observers. Inter-observer reproducibility was excellent except for superior offset measurement. Thus, this study validates a radiographic method for assessing the femoral implant position in hip resurfacing. We believe this could be useful for future studies on hip resurfacing devices.