Reliability of Determination of Bony Landmarks of the Distal Femur on MR Images and MRIBased 3D Models

Background/objective: consistent determination of the anatomical landmarks on image or image-based three dimensional (3d) models is a basic requirement for reliable analysis of the human joint kinematics using imaging techniques. we examined the intra- and inter-observer reliability of determination of the medial and lateral epicondyle landmarks on 2d mr images and 3d mri-based models of the knee. materials and methods: sixteen coronal plane mri recordings were taken from 18 healthy knees using a knee coil with t2-weighted fast spin-echo sequence and 512×512 pixel size. they were then processed by the mimics software to provide the coronal and axial plane views and to create a 3d image-based model of the femur. each image was reviewed twice, at least one-day apart. the interclass correlation coefficient, standard error of measurement, and coefficient of variation were calculated to assess the intra- and inter-observer reliability of the landmark determination by six experienced radiologists. a mixed model analysis of variance (anova) with two days of observation as the within-subject factor, and observers (six radiologists) and methods (2d vs. 3d) as between-subject factors were used to test the effect of observer, two days of observation and method of evaluation on landmark determination. results: the results indicated that the interclass correlation coefficients for the intraobserver and inter-observer determination of landmarks on images and image-based 3d models were above 0.97. the standard error of measurement ranged between 0.41 and 0.78 mm for x; 1.35 and 3.43 mm for y; and 1.03 and 4.71 mm for z coordinates. furthermore, the results showed no significant difference for within and between-subject comparisons of each coordinate of the lateral epicondyle as well as x and z coordinates of the medial epicondyle. for the y coordinate of the medial epicondyle, the p value of within-subject comparison was borderlinely significant (p=0.049).conclusion: it was concluded that the intra- and inter-observer reliability of the bony landmark determination on both image and image-based 3d models were excellent.