三维摄影测量技术评估青年人群面部不对称性

Three-dimensional photogrammetry to evaluate facial asymmetry among young population

目的评估中国青年人群的面部不对称性。方法 2017年5至12月在北京地区公开招募青年受试者。使用VECTRA H1三维立体照相机为所有受试者拍摄面部三维照片。将照片导入Geomagic Wrap 2017中,标记软组织标志点并建立坐标系,通过外眦点的水平面和过口角点的水平面将面部分为上、中、下3个部分。冠状面上,通过坐标计算双侧标志点到正中矢状面的距离以及睑裂高;面深度方面,通过坐标计算面深度指标,共13个测量指标。以配对t检验比较双侧测量值是否存在统计学差异,并计算双侧绝对差值和非对称率。最后对男性和女性的测量结果进行比较,P<0.05为差异有统计学意义。结果共招募到122名青年受试者,其中男性60名,年龄(25.1±3.8)岁,女性62名,年龄(27.3±4.3)岁。(1)冠状面上,男性双侧耳屏点和口角点到正中矢状面距离比较,差异有统计学意义(P<0.05);女性双侧外眦点、上睑顶点以及耳屏点到正中矢状面距离比较,差异均有统计学意义(P<0.05)。双侧标志点中(除外睑裂高),双侧外眦点到正中矢状面的距离绝对差值最小,在男性和女性中分别为(1.00±0.88) mm和(1.08±0.79) mm(t=0.541,P=0.589),非对称率仅为2.1%和2.4%;双侧耳屏点到正中矢状面距离的绝对差值最大,在男性和女性中分别达到(3.45±2.54) mm和(2.89±2.86) mm(t=-1.149,P=0.253),非对称率为4.6%和4.1%。(2)面深度方面,所有受试者双侧面深度指标比较,差异均有统计学意义(P<0.05)。双侧耳屏点到颏前点距离绝对差值最大,在男性和女性中分别达到(2.62±1.69) mm和(2.45±1.69) mm(t=-0.491,P=0.625),非对称率均为1.8%;双侧耳屏点到眉间点距离绝对差值最小,在男性和女性中分别为(1.77±1.25) mm和(1.91±1.54) mm(t=0.587,P=0.558),非对称率为1.4%和1.6%。结论中国青年人群中普遍存在一定的面部不对称性,双侧绝对差值一般不超过3.5 mm,上1/3面部的对称性较高,下1/3面部对称性较低。

Objective To evaluate facial asymmetry among Chinese young population via three-dimensional photogrammetry.Methods Young subjects were recruited in Beijing from May to December in 2017.Three-dimensional facial images were obtained by VECTRA H1 camera.The images were exported to Geomagic Wrap 2017.Soft tissue landmarks were identified,and a coordinate system was built on every image.The face was divided into upper,middle,and lower part by the horizontal plane passing the exocanthion and the horizontal plane passing the cheilion.On the coronal plane,the distances between the midsagittal plane and the homogeneous landmarks located on the right and left hemifaces as well as bilateral palpebral fissure height were computed.In terms of facial depth,facial depth parameters located on the right and the left hemifaces were computed.There was a total of 13 parameters.Parameters on one hemiface were compared with those on the other hemiface using paired t-test.Mean absolute difference(MAD)and asymmetric rate(AR)were computed.Finally,we compared the result on men to the result on women via t-test.P<0.05 was considered statistically significant.Results There was a total of 122 young subjects,60 men(25.1±3.8 years old)and 62 women(27.3±4.3 years old).(1)On coronal plane,among males,the difference between bilateral tragion and midsagittal plane and the difference between bilateral cheilion and midsagittal plane were statistically significant(P<0.05);among females,the difference between bilateral exocanthion and midsagittal plane,the difference between bilateral palpebrale superius and midsagittal plane,and the difference between bilateral tragion and midsagittal plane were statistically significant(P<0.05).Among bilateral landmarks(except for palpebral fissure height),the MAD of the distance between bilateral exocanthion and midsagittal plane was the smallest,(1.00±0.88)mm(AR=2.1%)and(1.08±0.79)mm(AR=2.4%)among men and women,respectively(t=0.541,P=0.589).The MAD of the distance between lateral tragion and midsagittal plane was the largest,(3.45±2.54)mm(AR=4.6%)and(2.89±2.86)mm(AR=4.1%)among men and women,respectively(t=-1.149,P=0.253).(2)In terms of facial depth,among both males and females,the difference between all bilateral facial depth parameters was statistically significant(P<0.05).The MAD of the distance between the pogonion and bilateral tragion was the largest,(2.62±1.69)mm(AR=1.8%)and(2.45±1.69)mm(AR=1.8%)among men and women,respectively(t=-0.491,P=0.625);the MAD of the distance between the glabella and bilateral tragion was the smallest,(1.77±1.25)mm(AR=1.4%)and(1.91±1.54)mm(AR=1.6%)among men and women,respectively(t=0.587,P=0.558).Conclusions Facial asymmetry is universal among Chinese young population.The MAD does not exceed 3.5 mm.Upper one-third face has higher symmetry while lower one-third face has lower symmetry.