Spline approximation of auricular shape and comparison among those of neonates

In Japan, 60% of neonates are born with auricular deformity. Therefore it is important to express the auncular shape numerically and utilize it for medical treatment. In this paper, the auricular shape is approximated by B-spline function of order four with four internal knots. Derived positions of control points are used as an indicator of auricular shape. Neonates' 490 auricular shapes are classified into following six groups: normal ear, upper folded helix, diagonal side folded helix, side folded helix, Stahl's ear and folded lobulus auriculae. Control points of each group are compared and it is revealed that every group can be characterized by those positions. Also discriminant analyses using the position and Mahalanobis generalized distance are performed. For folded lobulus auriculae, upper folded and folded helix success ratio of more than 0.7 is obtained. However, as diagonal side folded helix and Stahl's ear are unable to distinguish from normal ear sufficiently, those success ratios are less than 0.7. Finally, target auricular shape after treatment is generated by moving control pints gradually toward the direction where Mahalanobis distance between normal ear becomes the least.