Evaluating the reliability of the lateral femoral condyle measuring methods by different modalities for patients with lateral patellar dislocation

Abstract

Background A variety of measurement methods and imaging modalities are in use to quantify the morphology of lateral femoral condyle (LFC), but the most reliable method remains elusive in patients with lateral patellar dislocation (LPD). The purpose of this study was to determine the intra- and inter-observer reliability of different measurement methods for evaluating the morphology of LFC on different imaging modalities in patients with LPD. Methods Seventy-three patients with LPD were included. Four parameters for quantifying the morphology of LFC were retrospectively measured by three observers on MRI, sagittal CT image, conventional radiograph (CR), and three-dimensional CT (3D–CT). The intra-class correlation coefficient was calculated to determine the intra- and inter-observer reliability. Bland–Altman analysis was conducted to identify the bias between observers. Results The lateral femoral condyle index (LFCI) showed better intra- and inter-observer reliability on MRI and 3D–CT than on CR and sagittal CT images. The mean difference in the LFCI between observers was lowest on 3D–CT (0.047), higher on MRI (0.053), and highest on sagittal CT images (0.062). The LFCI was associated with the lateral femoral condyle ratio (ρ = 0.422, P = 0.022), lateral condyle index (r = 0.413, P = 0.037), and lateral femoral condyle distance (r = 0.459, P = 0.014). The LFCI could be reliably measured by MRI and 3D–CT. Conclusion The LFCI could be reliably measured by MRI and 3D–CT. The LFCI was associated with both the height and length of LFC and could serve as a comprehensive parameter for quantifying the morphology of LFC in patients with LPD.