Sex differences in the zygomatic angle in japanese patients analyzed by MRI with reference to Moiré fringe patterns.

To quantitate the degree of zygomatic protrusion, a new item, "zygomatic angle," was measured on MRI cross sections in the orbitomeatal plane. The sex differences in the zygomatic angle were highly significant on both sides, being larger in males than in females. The shape of the zygomatic protrusion was classified into angulate, intermediate, and massive types according to the value of the zygomatic angle. The incidence of the angulated type was significantly more frequent in females, and that of the massive type was significantly more frequent in males. Another analysis was made of horizontal cross sections in the orbitomeatal plane in moiré photographs. In these cross sections, it was possible to judge the above-mentioned three types of protrusions. The number of Moiré fringes in the infraorbital region was measured in relation to the amount of zygomatic protrusion. The results on Moiré photographs coincided with those obtained by MRI analysis.