Importance of elliptic Fourier methods for morphometry of complex outlines: application to the distal human femur

The purpose of this technical note is to present an automatic procedure of shape characterisation using new developments in elliptical Fourier methods combined with image analysis techniques. It was applied, as an example, to the outline of the distal extremity of the distal human femur in inferior axial view. This outline was automatically extracted and characterised by a n ordered series of harmonics, each harmonic being described by four new pa rameters called elliptical descriptors. Step by step reconstructions of out lines using an increasing number of harmonics were than performed. The simu ltaneous study of the elliptic descriptors and of the step by step reconstr uctions allowed a considerably easier geometric and morphologic interpretat ion of the harmonic contributions than classically. The main morphologic fe atures of the distal femur (lateral and medial condyles, intercondylar foss a, lateral and medial borders of the articular surface, and patellar groove ) were mainly described by the first seven harmonics. These new development s in elliptic Fourier methods open interesting perspectives for the study o f complex outlines, providing an accurate individual morphologic characteri sation, and thus the possibility of polymorphic analysis.