Abstract
The angle between the auricular long axis and the nasal dorsal line (Angle Z) is used during operation for microtia and the expectation of growth of auricle and maxilla. It is said that these lines are parallel in caucasians. In Japan, the mean of this angle was report-ed by Kamiyama to be 16.0° for a male group, 14.6° for a female group, and 15.3° for the total group. An age-related change of this angle was reported by Gyoutoku, but the method of taking photographs was complicated due to the use of a special appliance. To simplify the method of taking photographs, change of the angle between the auricular long axis and the nasal dorsal line (Angle Z) during rotation of the head was studied. This study was perform-ed using two methods, cylindrical models and real persons. The following results were obtained :
1) When using a cylindrical model, the Angle Z was not changed by slight rotation of the model.
2) Theoretically, the following expression was derived
Z= tan-1 (tanθ _??_× cosω) -tan-1 (tanη _??_ × cosω)
ω: angle of rotation
θ _??_: the angle of the nasal dorsal line to a vertical line (ω=0)
η _??_: the angle between the auricular long axis line and a vertical line (ω=0)
3) In individual persons, changes of the Angle Z are unbalanced, but the statistical data of Angle Z is useful.
4) During more or less rotation of the head, the Angle Z changed only slightly. Therefore, we can get useful data from photographs taken by measuring with the eye.
5) Errors of Angle Z from photographs taken by measuring with the eye were less than errors of Angle Z measured by construction on photographs.
