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measurement of zygoma and zygomatic arch

[ Author:Dr. Fushun Ma | Time:2011-10-20 10:05:35 |  Font Size: [Large Medium Small]
Tags:Zygoma, zygomatic arch, facial bone measurement

We judge whether a zygaom bone or zygomatic arch is high or not by visual analysis subjectively. It is more practical to setup an objective ruler for measure if the zygoma bone or the arch is too protruding. The problem is that our face is smooth and has no landmark on it. Where should we start to measure the face? We are lucky to have some mathematic solutions for this problem. The following is the physical and bony facial measurement solutions Dr. Ma invented and described in his PhD dissertation.

The physical measurement of the middle face width

Simple numerical measurement of the face width has very little meaning, because when the face is longer it doesn't look wide at the same facial width. The key element to describe a face contour is facial width and length ratio, only when this ratio is in a certain scope the facial appearance is the coordinate. Following a lot of scientific research Dr. Ma provide the facial height index to define the middle face contour coordination. This index is calculate by the mid facial height dividing the middle face width. The mid facial height is the distance  between the mid brow point to the base of the nasal columella. The mid face width is the measure of the widest part of the face. From Dr. Ma's study the facial height ration for north Chinese male is 0.55 ?? 0.03, female 0.54 ?? 0.03, the smaller the value the wider the face. In other words, the width of the face is slightly less than twice as the mid facial height. As the mid face height is roughly the length of the nose, we can say the width of the face is about twice as long as the nose. So if someone's face width is greater than twice of his own nose length, we consider her or his zygoma and zygomatic arch is prominent and it is safe to do a malar reduction surgery for her or him.


Line "b" is twice as long as line "a".

Well, does all wide face need a surgery?  The answer is negative. If the upper and lower part of the face are wide, proportional to the width of the middle portion, the facial outline looks harmoniously, no surgery is needed. However, if the width of the upper and lower part is much narrower than the middle, the face is in a diamond shape. Such a situation guarantees the need of a reduction surgery to restore the facial outline coordination. In order to describe the zygoma area prominence Dr. Ma use the facial diamond index which compares the mid face width and the average width of the upper and lower face. The bigger the index the fat the diamond. The average facial diamond index of the northern Chinese male is 1.26, women1.29.

Bony structure investigation of zygoma and the zygomatic arch

So far we already know that someone's face is wide and diamond enough for a reduction surgery. But we still not sure if the soft tissue or the bony structure of the face need to trim. The physical measurement of the face shows only the facial outline anyway. At this point a facial bone structure investigation is helpful. The best approach is to make maxillofacial CT scan. Using three-dimensional reconstruction and CT images, the width of the middle face bone structure and the thickness of zygoma and zygomatic arch are precisely measured. At the sometime the facial bone symmetry can be observed also. Thus the measurement result can be compared with the standard value from the comparable race, region and gender. With this measures the amount of  osteectomy and direction and the distance of osteotomy can be calculated more precisely. Adequate pre-operative design, careful in application selection and specific operation plan are the key elements of a successful and satisfactory surgery.


CT images of the zygoma and zygomatic arch, the zygomatic arch on the right image is much wider

    
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