Three-dimensional analyses of aging-induced alterations in facial shape: a longitudinal study of 171 Japanese males.

We sought to generate data to facilitate forensic facial comparisons. Specifically, we conducted a longitudinal study of alterations in face shape induced by aging. We obtained two three-dimensional facial shape measurements in 171 Japanese males at intervals of approximately 10 years. With this data, we created a homologous model consisting of 10,741 data points for each face based on 33 anatomical landmarks. We averaged the movements of corresponding data points between the two homologous models for each individual and used this data to predict up to 30 years of face aging in an average Japanese male. We clearly identified aging-induced shape changes, such as drooping and denting of the facial folds, drooping of the upper lip, and projection of the lower eyelid, in the virtually aged model. A quantitative comparison of aging-induced shape alterations among three age groups (individuals in their 20's, 30's, and 40-50's) showed that these alterations accelerated more quickly as age increased. Using our predictive model, we conducted a preliminary study focused on facial shape alterations induced by reductions in body weight. Our findings indicated that our proposed method would also be valid for this purpose.

Ergonomic evaluation of a mechanical anastomotic stapler used by Japanese surgeons.

PURPOSE: The satisfaction rating of currently available mechanical staplers for Japanese surgeons with small hands is low. To identify the issue, we examined the relationship of hand dimensions and grip force with the operation force of a mechanical circular stapler. METHODS: Hand dimensions and grip force were measured in 113 Japanese surgeons (52 men and 61 women). We then evaluated the relationship between grip width and the operation force required to push the lever of the stapler, at three points on the lever, using a digital force gauge. RESULTS: The optimal grip width of the dominant hand was 62.5 ± 8.5 mm for men and 55.5 ± 5.9 mm for women (p < 0.001). The maximum grip force of the dominant hand was 44.2 ± 6.1 kg for men and 29.7 ± 4.5 kg for women (p < 0.001) and the maximum operation force required to push the lever 7.0, 45.0, and 73.0 mm from the end of the lever was 21.8, 28.6, and 42.4 kg, respectively. CONCLUSIONS: To our knowledge, this is the first ergonomic study of a surgical stapler to be conducted in Asia. Firing the stapler by gripping the proximal side of the lever is physically impossible for most Japanese women surgeons since the required operation force exceeds the maximum grip force, which probably accounts for the stress perceived by these women.

Global patterns of the cranial form of modern human populations described by analysis of a 3D surface homologous model.

This study assessed the regional diversity of the human cranial form by using geometric homologous models based on scanned data from 148 ethnic groups worldwide. This method adopted a template-fitting technique for a nonrigid transformation via the iterative closest point algorithm to generate the homologous meshes. Through the application of principal component analysis to 342 sampled homologous models, the largest variation was detected in overall size, and small South Asian crania were clearly verified. The next greatest diversity was found in the length/breadth proportion of the neurocranium, which showed the contrast between the elongated crania of Africans and the globular crania of Northeast Asians. Notably, this component was slightly correlated with the facial profile. Well-known facial features, such as the forward projection of the cheek among Northeast Asians and compaction of the European maxilla, were reconfirmed. These facial variations were highly correlated with the calvarial outline, particularly the degree of frontal and occipital inclines. An allometric pattern was detected in facial proportions in relation to overall cranial size; in larger crania, the facial profiles tend to be longer and narrower, as demonstrated among many American natives and Northeast Asians. Although our study did not include data on environmental variables that are likely to affect cranial morphology, such as climate or dietary conditions, the large datasets of homologous cranial models will be usefully available for seeking various attributions to phenotypic skeletal characteristics.

Three-dimensional shape variation and sexual dimorphism of the face, nose, and mouth of Japanese individuals.

Three-dimensional (3D) shape variations of the face and facial parts in Japanese adults were examined to collect basic data to be used for facial comparison in forensics. In total, 1000 3D facial scans (500 males, 500 females) of Japanese individuals were re-meshed into anatomically homologous shape models and analyzed by principal component analysis (PCA) after Procrustes superimposition. Facial parts (the nose and the mouth) were segmented from homologous face models and analyzed by PCA, too. Among all kinds of objects (the face, the nose, and the mouth), the most predominant shape variation represented by the first principal component (PC1) was the height-width proportion. The second largest variation (PC2) in the face and the nose was depth; for the mouth, it was the relative protrusion of the upper and lower lips. We interpreted predominant shape variations represented by the first five principal components (PCs) in each object. Asymmetric shape variations were observed within these PCs for the nose and the mouth. Sexual dimorphism of the face and the facial parts was also examined by testing the significance of sex-linked differences in PC scores. A significant difference was found between males and females for many PCs. Sexual dimorphism was examined also by emphasizing the shape difference between average male and female faces. Our results revealed predominant 3D shape variations and sexual dimorphism of the face and facial parts. The results may be informative for performing facial comparison in police investigations, an increasingly used technique.

Analysis of skin movement with respect to flexional bone motion using MR images of a hand.

This study describes the methodology for analyzing skin movement with respect to the predefined flexional motion of the hand. The 3D in vivo geometric data were acquired through magnetic resonance (MR) scanning of multiple hands in various postures. Custom software was developed to segment MR images and to generate polygonal isosurfaces. A new bone coordinate system (BCS) was defined to describe the skin movement measured with the skin-surface markers. The BCS was defined by the surface registration technique, which could minimize the distance among the 3D polygonal surfaces of different postures. MR images of six subjects in the 3 postures were captured with skin-surface markers for the experiment. Skin movement on the second metacarpal bone, which was fixed during the flexional motion, ranged from 1.169 to 10.885 mm. While the distance of the skin movement varied from one subject to another, a common skin movement direction was observed among the six subjects. For the repeatability evaluation of the proposed method, the MR images of the same subject were independently processed 10 times by a trained operator. The standard deviation of the skin movement on the second metacarpal of the index finger with respect to the predefined flexional motion ranged from 0.45 to 0.74 mm.

Age-independent and age-dependent sex differences in gait pattern determined by principal component analysis.

Although various studies have reported significant sex differences in pelvic and/or hip-joint motion during normal walking in healthy adults, it is still unclear whether such differences are among the most dominant age-independent sex differences. This study was conducted to analyze the whole waveform of lower-extremity joint kinematics obtained from 191 healthy adults using a principal component analysis (PCA). The PCA was conducted using a 955×1212 input matrix constructed from the participants' time-normalized pelvic and right-lower-limb-joint angles along three axes (five trials of 191 participants×101 data points×4 angles×3 axes). Two-way (age×sex) analyses of variance were conducted on the principal component scores (PCSs) of principal component vectors (PCVs) 1 through 6, each of which explained more than 5% of the variance. We identified a PCV that exhibits a significant age-sex interaction (PCV 1). The characteristics of sex differences reported in previous studies could be observed in the reconstructed waveforms of this PCV. Thus, we can conclude that the sex differences in the gaits reported in previous studies are not consistent across age groups. Furthermore, we also found a PCV that exhibited only a significant sex difference (PCV 6). This PCV was the first and only PCV to exhibit a sex difference without any age-related effect or age-sex interaction. Therefore, we concluded that the movement related to this PCV is age-independent and is the most dominant sex difference in the gaits observed during normal walking.

Multiple regression based imputation for individualizing template human model from a small number of measured dimensions.

Individual human models are usually created by direct 3D scanning or deforming a template model according to the measured dimensions. In this paper, we propose a method to estimate all the necessary dimensions (full set) for the human model individualization from a small number of measured dimensions (subset) and human dimension database. For this purpose, we solved multiple regression equation from the dimension database given full set dimensions as the objective variable and subset dimensions as the explanatory variables. Thus, the full set dimensions are obtained by simply multiplying the subset dimensions to the coefficient matrix of the regression equation. We verified the accuracy of our method by imputing hand, foot, and whole body dimensions from their dimension database. The leave-one-out cross validation is employed in this evaluation. The mean absolute errors (MAE) between the measured and the estimated dimensions computed from 4 dimensions (hand length, breadth, middle finger breadth at proximal, and middle finger depth at proximal) in the hand, 2 dimensions (foot length, breadth, and lateral malleolus height) in the foot, and 1 dimension (height) and weight in the whole body are computed. The average MAE of non-measured dimensions were 4.58% in the hand, 4.42% in the foot, and 3.54% in the whole body, while that of measured dimensions were 0.00%.

COMPARING 3D FOOT SHAPE MODELS BETWEEN TAIWANESE AND JAPANESE FEMALES.

This study compares foot shape and foot dimensions between Taiwanese and Japanese females. One hundred Taiwanese and 100 Japanese female 3D foot scanning data were used for comparison. To avoid the allometry effect, data from 23 Taiwanese and 19 Japanese with foot length between 233 to 237 mm were used for shape comparison. Homologous models created for the right feet of the 42 subjects were analyzed by Multidimensional Scaling. The results showed that there were significant differences in the forefoot shape between the two groups, and Taiwanese females had slightly wider feet with straighter big toe than Japanese females. The results of body and foot dimension comparison indicated that Taiwanese females were taller, heavier and had larger feet than Japanese females, while Japanese females had significantly larger toe 1 angle. Since some Taiwanese shoemakers adopt the Japanese shoe sizing system for making shoes, appropriateness of the shoe sizing system was also discussed. The present results provide very useful information for improving shoe last design and footwear fit for Taiwanese females.

A protocol for evaluating the accuracy of 3D body scanners.

Scan-derived landmarks locations and surface shapes are more and more used, but there is no commonly accepted protocol for evaluating the accuracy of these measurements. Therefore we propose a protocol for evaluating the accuracy of surface shape and the repeatability of scan-derived landmark locations. According to existing Japanese and German domestic standards, we propose to use an artefact (e.g. sphere with diameter of about 120 mm) calibrated very accurately for evaluating the accuracy of scanner-systems. For evaluating the repeatability of landmark locations, we propose to use an anthropomorphic dummy with landmark locations premarked. These test objects are measured by a 3D body scanner to be evaluated. Evaluation parameters such as trueness, precision, and repeatability are calculated from the measured data. A round-robin test was conducted in six different institutes using 17 body/head/foot scanners produced by eight companies. The purposes of the roundrobin test were to evaluate the availability of test objects to different body scanners, and to examine the measurement locations of test objects and quality parameters to be reported. As a result, the proposed test objects could be measured and the data exported by all scanner systems except one, which could not export the ball measurement. For a comparative purpose, a figure of measured surface might be useful.

Errors in landmarking and the evaluation of the accuracy of traditional and 3D anthropometry.

Body dimensions are based on landmarks of the body, but the magnitude of error in landmark determination is not well known. Therefore, a study was performed in which 40 subjects were marked five times in total by one highly skilled marker and a novice marker. Immediately after marking, a skilled measurer determined 34 body dimensions that were based on the mark locations. Intra- and inter-observer errors in landmarking of 35 landmarks, as well as those in 34 body dimensions were quantified. The error in landmarking was defined as the distance between two marks made on the same landmark by the same marker (intra-observer error) or by two different markers (inter-observer error). To make the first mark invisible when the second mark was made, the first mark was made using an invisible ink pen under black light. Landmarks with large intra-observer errors also had large inter-observer errors. Errors in body dimensions were smaller than landmarking errors in 23 measurements, which suggested that the magnitude of landmarking error would be underestimated from errors in body dimensions. In 15 body dimensions, measurements based on marks made by two different markers were not comparable according to the ISO 20685 criterion. Examination of body dimensions and landmarks with large inter-observer errors suggested that reducing inter-observer landmarking errors was necessary to reduce inter-observer measurement errors, and that a possible solution was to explicitly define landmarks with large errors in more detail so that anthropometrists can pinpoint them on the skin. Quantitative data on the intra- and inter-observer landmarking errors in the present study may be useful as a reference when evaluating and comparing the performance of software for calculating landmark locations for 3D anthropometry.

Deformation of foot cross-section shapes during walking.

To clarify the magnitude of shape change during walking, the shapes of four cross-sections (Forefoot, Instep, Navicular, and Heel) of the right foot during standing and walking were measured using a four-dimensional measurement system we developed (14 Hz) with an accuracy of +/-0.5 mm. Images of the sole were measured using a high-speed video camera (120 Hz). Cross-section shapes and derived dimensions were compared between the standing condition, first peak (P1), and midstance valley of two peaks (MSV) of vGRF during walking. Heel and Navicular cross-sections were more laterally inclined during walking than during standing by 6 degrees on average. Compared to at standing, breadth of the cross-section in contact with the ground was wider at the heel and instep at timing P1, and was wider at the forefoot and narrower at heel at timing MSV. Medial length was longer and dorsal arch was higher during walking than during standing. Plantar arch height did not differ between the three conditions. The maximum difference in plantar arch height between standing and P1 was 1.3 mm, much smaller than the inter-individual variation of 7 mm.

Biological variables in height growth of Japanese twins: a comparison with those of singletons.

BACKGROUND: Biological variables in height growth in Japanese singletons are well documented, but there has been less research on Japanese twins. AIM: The study investigated the biological variables in height growth of Japanese twins and compared them with those of Japanese singletons. SUBJECTS AND METHODS: Samples of 92 boys and 99 girls from monozygotic twins, and 41 boys and 38 girls from dizygotic twins born in 1960-1973, from the Twin Class in the Junior and Senior High Schools affiliated to the University of Tokyo, Japan, were considered. The Bayes modal estimation method was applied to the triphasic generalized logistic growth model (BTT model). From the fitted model, the biological variables were extracted. RESULTS: The monozygotic twins, on average, matured earlier than dizygotic twins, but later than singletons. Until pre-adolescence, the height velocity of twin children is lower than that of singleton children. This results in the final stature of twin youths being smaller than that of singleton youths. The twins are, on average, about 2.6 cm smaller than singletons in final height only due to the lower velocity during birth to pre-adolescence. Comparing with the average final stature of dizygotic children, the boys were 3.9 cm and the girls were 2.8 cm shorter than Japanese late-maturing boys and girls, respectively. For monozygotic children, the boys were 3.8 cm and the girls were 3.0 cm shorter than the respective Japanese late-matured singleton boys and girls. CONCLUSION: The biological variables of twins differ significantly from those of singletons. It is important to recognize that singleton reference values do not correctly reflect the growth of twins.

Inter-generation differences in foot morphology: aging or secular change?

Inter-generation differences in foot dimensions were examined using ANCOVA to determine whether aging or secular change is the more important causal factor. In examining the results, bone size was assumed not to change after the end of linear growth, while foot arches were assumed to become flatter rather than higher if there were any changes in skeletal structure. Changes in overall body build according to age were examined using statistical data collected by the government through population-follow-up. Secular changes in foot length (FL) and foot breadth, diagonal (FB) as well as the changes with age in FB were examined using data measured at ages younger than 50 years. The effects of overall body build were examined using the body mass index (BMI). Compared to the 1970 group (birth year: 1960-78) of the same FL, the 1930 group (birth year: 1909-39) had larger foot circumferences, wider breadth measurements, higher dorsal arches and ball, and greater toe 5 angle, but had shorter fibular instep lengths and shorter 5th metatarsal bones. The 1930 groups tended to have larger FB than the 1970 group of the same foot circumference. No inter-generation differences were observed in the heights at the medial and lateral malleoli, toe 1 angle, or the relationship between FB and heel breadth. These findings are discussed in terms of the effects of weight increase after the end of linear growth, changes in skeletal structure, overall body build as young adults, socioeconomic status during the growth period, as well as differential growth rates of foot bones. The conclusions are 1) changes in foot length and longitudinal arches due to aging are negligible, 2) the large circumferences, breadths, and higher dorsal arches and ball of the 1930 group for their foot length are better explained by their robust bones than by the increase in soft tissue after the end of linear growth, and 3) the larger FB of the 1930 group for their foot circumference is partly explained by their shorter fibular instep length. As a whole, factors affecting growth (secular change) are more important than changes after the end of growth (aging) in the inter-generation differences in foot morphology.

Analysis of 3D face forms for proper sizing and CAD of spectacle frames.

Three-dimensional morphological variations in the human face were analysed using digital models of the human face, and the usefulness of such analysis in designing industrial products was demonstrated by validating spectacle frame designs based on an original sizing system developed based on the analysis. A normalized model of the three-dimensional face form was made for each of 56 young adult Japanese males. The morphological distances between subjects were defined, and subjects were divided into four groups based on analysis of the distance matrix. A prototype spectacle frame was designed for the average form of each of the four groups. Tightening force of the prototype frames was adjusted using the materialized average forms with soft material placed at the nasal bridge and side of the head. Four prototype frames as well as a conventional frame were evaluated using sensory evaluation and physical measurement of the pressure and slip in 38 young adult male subjects. For each of the 38 subjects, prototype frames were ranked according to the morphological similarity of the subjects and the average form of the four groups: the frame designed for the average form of the group most similar to the subject was #1, the frame designed for the average form of the next most similar group was #2, and so on. For the groups with smaller or narrower faces, new frame #1 was most preferred and had the best overall fit, smallest slip sensation and largest pressure sensation. The groups with larger or wider faces preferred tighter frames than new frame #1, because they were concerned that the frames might slip, although the frames did not. Most of the subjects habitually wore spectacles, and the reason that groups with larger or wider faces preferred tighter frames was thought to be that they were accustomed to tighter fitting frames.