A simplified relationship between the femoral trochlea and the femoral condyle: A sagittal MRI analysis by an ellipse-fitting approach.

Abstract

We have introduced an ellipse-fitting approach to express the shapes of trochlea and condyle on magnetic resonance imaging (MRI) and to analyze their relationship. Fifty healthy right knees were sagittal-imaged by MRI at full extension. On the deepest trochlear groove slice, the articular surface was best-fitted by a circle. Based on the center of this circle, both the most prominent slices of the medial and lateral trochleae were best-fitted by ellipses. On the most distal slice of medial condyle, the articular surface was best-fitted by a horizontal ellipse. Based on the center of this ellipse, the lateral condyle was best-fitted by a rotational ellipse. The semimajor and semiminor axes of the trochlear ellipse and the condylar ellipse constituted a rectangle that represented the relationship between the trochlea and the condyle. The anteroposterior dimension (l) of this rectangle was 12.33 ± 1.41 mm, and the superoinferior dimension (w) was 7.21 ± 1.23 mm. The average tangent angle (θ) of the rectangle was 30.1° ± 2.6°. There were significant sex differences in l, w, and θ (all P ≤ 0.006), and all correlated significantly with the height of the subject (all P ≤ 0.001). The relationship between the femoral trochlea and the femoral condyle differed significantly between males and females, but this could have been a consequence of the significant correlation with subject height. Clin. Anat. 33:500-506, 2020. © 2019 Wiley Periodicals, Inc.