Anthropometric Assessment of the Normal Adult Human Ear.

PURPOSE: Knowledge of anthropometric measurements of the external ear is important as variations exist based on gender, age and ethnicity. This study has derived anthropometric data pertaining to the external ear in the Maharashtrian population.
MATERIALS AND METHODS: Nine variables of the external ear were measured in 505 Maharashtrian adults (aged 18-64 years) using photoanthropometric methods.
RESULTS: Descriptive data and the left-right symmetry for the study population were obtained.
CONCLUSION: These data have applications in screening for or monitoring diseases, otoplastic surgery, forensics, industrial design, apparel design and ergonomics.

INTRODUCTION

An important organ contributing to the esthetics of the human face is the ear. The size, shape, position and projection of the ear all influence the appearance of the individual. The external ear consists of the external auditory meatus and the auricle or pinna. The latter is most commonly associated with congenital abnormalities such as microtia, macrotia, malposed ear, accessory auricle, lop ear and protruding ear; which may be associated with Down's syndrome, Potter's syndrome and Turner syndrome.[1] Acquired defects result from traumatic injuries and pathologic conditions, especially cancer. Five to eight percent of all skin cancers are located on the auricle[2] as its projection and exposure make it more prone to actinic damage. Rectifying these abnormalities requires information about normal auricular dimensions, the auricle's bilateral position on the face and general conformation. Some studies of the ear involving syndromes and anomalies have been published, but few studies have investigated the ear in the normal population.

Recent anthropometric studies of the external ear from different parts of the world prove that much variability exists depending on the age, sex and ethnic group, and even in the same person between the right and left ears.[3] In spite of this, the available literature suggests that males have larger ears than females, the length and width of the ear keep on increasing with age, and the general size of the ear varies in populations of different ethnicities.[4] Very few studies on anthropometric data of the normal human ear in the Indian population are available and anthropometric measurements given in the Western literature are less likely to be of use in the Indian population.[356]

The purpose of this study is to gather photoanthropometric data about the ear (auricle) in the Maharashtrian population using photogrammetry which is less invasive to a patient, is less time-consuming, and provides a permanent record of data.

MATERIALS AND METHODS

This study is a cross-sectional observational study, wherein no intervention was carried out on the participants. Every fifth patient in the age of 18–64 years was selected to get 505 participants from among the patients reporting to the outpatient department of our institute in May 2015. Individuals of Maharashtrian origin willing to give informed written consent permitting the publishing of photographs of their ears taken with a customized grid were included; those with a history of craniofacial trauma, ear diseases, congenital or acquired anomalies and/or ear surgeries, uncooperative and mentally handicapped individuals and wrestlers, boxers or practitioners of martial arts[7] were excluded.

Similar to the technique of Liu,[8] a 1 mm × 1 mm grid was printed on a clear A4-sized sticker sheet and pasted over an 8 cm × 8 cm × 3 mm clear glass piece and the excess sheet was trimmed off. A customized acrylic platform was fabricated with provision for mounting the camera and housing the glass and grid so that the photographs taken were uniform for all individuals. The mounting for holding the glass was fixed with an LED light strip that was connected to a 9 V battery to provide good illumination [Figures 1 and 2]. Informed written consent for permission to photograph the external ear and use the photographs for anthropometric study was taken from all the participants.

Figure 1

Armamentarium used for the study

Figure 2

Arrangement of armamentarium for the study

All participants were asked to remove their ear accessories. They were then seated upright in a chair such that their Frankfurt horizontal plane was parallel to the floor. A plain white sheet of paper having a cut out at the center for the ear was placed to demarcate the ear margins from the hair and rest of the face. The custom-made platform was placed such that the plane of the mounted grid was parallel to and just touching the plane of the auricle. Then, photographs of the left and right auricles of each individual were taken in the same fashion by a principal investigator [Figures 3–6]. The images and data were transferred to a computer and resized proportionately such that 1 mm of the grid in the image was equal to 1 mm of the standard measuring scale, when the image was printed on A4-sized paper. On the printed images, various landmarks of the auricle were identified. A straight line was drawn marking the attachment of the auricle to the skin of the face. A perpendicular was drawn to this first line such that it was tangential to the highest point on the helix. Another perpendicular was drawn to the first line such that it was tangential to the lowest point on the lobule. Another line is drawn parallel to the first line and tangential to the outermost point on the helix of the auricle. A rectangle was thus drawn tangential to the four borders of the auricle. This rectangle defined the boundaries of the auricle [Figure 7]. The following measurements were made.

Figure 3

Method of recording the photographs

Figure 6

Photograph of right ear of participant

Figure 7

Guide to measurement of the various variables of the ear

Photograph of left ear of participant

Ear length – Perpendicular distance between the tangents to the highest point on the helix and the lowest point on the lobule

Ear breadth – Perpendicular distance between the straight line marking the attachment of the auricle to the skin of the face and the tangents to the outermost point on the helix

Ear length above tragus – Perpendicular distance between the tangent to the highest point on the helix and the superior-most point of the tragus

Ear length below tragus – Perpendicular distance between the tangent to the lowest point on the lobule and the inferior-most point of the tragus

Tragus length – Perpendicular distance between the superior-most and inferior-most points on the tragus

Concha length – Perpendicular distance between the superior-most and inferior-most points on the concha, in a plane parallel to the straight line marking the attachment of the auricle to the skin of the face

Concha breadth – Perpendicular distance between the anterior-most and posterior-most points on the concha, in a plane perpendicular to the straight line marking the attachment of the auricle to the skin of the face

Lobule height – Perpendicular distance between the point of attachment of the lobule to the skin of the face, to the tangent drawn to the lowest point on the lobule

Lobule width – Perpendicular distance between the point of attachment of the lobule to the skin of the face, to the outermost point on the lobule in a plane perpendicular to the straight line marking the attachment of the auricle to the skin of the face.

All measurements were made with a scale to the closest millimeter by the same principal investigator and entered in a tabular format along with the age and sex of each participant. Taking guidelines from the study of Sforza et al.,[9] the assimilated data were divided into four age groups: 18–30 years, 31–40 years, 41–50 years and 51–64 years, and further segregated based on gender.

Statistical analysis

The data were subjected to statistical analysis using SPSS Version 20 (IBM Corp., Armonk, NY). Shapiro–Wilk's test was done to determine normality of the data. Data were not found to be normally distributed; thus, nonparametric tests were done. Mann–Whitney U-test was done to determine statistical significance in the values for males and females within each age group. Spearman's correlation coefficient test was conducted to determine the symmetry between right and left sides among individual age groups and also for whole population. Correlation coefficient (r value) was interpreted as follows:

< 0.2 indicates slight correlation

0.2–0.4 indicates weak correlation

0.4–0.7 indicates moderate correlation

0.7–0.9 indicates high correlation

>0.9 indicates almost perfect correlation.

RESULTS

Age and sex distribution of study population

This study included 505 participants within the age range of 18–64 years (mean age = 38.33 ± 11.994 years). 225 were males (mean age = 40.96 ± 12.017 years) and 280 females (mean age = 36.21 ± 11.571 years). The age groups, number of male and female participants in each group and their mean ages have been enlisted in Table 1.

Table 1

Age and sex distribution of study population

Descriptive data of the study population

The mean values, standard deviation, and standard error for each variable of each ear in the study population are enlisted in Tables 2–9.

Table 2

Descriptive data of study population and comparison of mean left ear measurements among males and females aged 18-30 years

Table 9

Descriptive data of study population and comparison of mean right ear measurements among males and females aged 51-64 years

18–30 years age group

Evaluation of 156 participants, 49 males and 107 females (mean age = 24.72 years), was done. It was observed that males had slightly larger dimensions for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, right ear length above tragus, left ear length below tragus, right ear length below tragus, left ear concha length, right ear concha length, left ear concha breadth, right ear concha breadth, left ear lobule height, right ear lobule height, left ear lobule width and right ear lobule width as compared to females. On the other hand, females had slightly higher values for left ear tragus length and right ear tragus length as compared to the males. The P values for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, right ear length above tragus and left ear lobule width were <0.05 and hence statistically significant. All other variables of the ear between males and females in this age group had a P > 0.05 and hence were not significant [Tables 2 and 3]. The Spearman's correlation coefficient (r) was calculated and the highest strength of correlation was seen for left ear length–right ear length (r2 = 85.9%), while the least was observed for left ear breadth–right ear breadth (r2 = 69.7%). The P value for all the correlations was found to be <0.05, and hence, the correlations were statistically significant [Table 10].

Table 3

Descriptive data of study population and comparison of mean right ear measurements among males and females aged 18-30 years

Table 10

Correlation of right and left side measurements of study population aged 18-30 years

31–40 years age group

Evaluation of 150 participants, 65 males and 85 females (mean age = 35.98 years), was done. It was observed that males had slightly larger dimensions for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, right ear length above tragus, left ear length below tragus, right ear length below tragus, left ear tragus length, right ear tragus length, left ear concha length, right ear concha length, right ear concha breadth, left ear lobule height, left ear lobule width and right ear lobule width as compared to females. On the other hand, females had slightly higher values for left ear concha breadth and right ear lobule height as compared to the males. The P values for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, and right ear length above tragus width were <0.05 and hence statistically significant. All other variables of the ear between males and females in this age group had a P > 0.05 and hence were not significant [Tables 4 and 5]. The highest strength of correlation was seen for left ear length–right ear length (r2 = 85.0%), while the least was observed for left ear concha breadth–right concha ear breadth (r2 = 68.8%). The P value for all the correlations was found to be <0.05, and hence, the correlations were statistically significant [Table 11].

Table 4

Descriptive data of study population and comparison of mean left ear measurements among males and females aged 31-40 years

Table 5

Descriptive data of study population and comparison of mean right ear measurements among males and females aged 31-40 years

Table 11

Correlation of right and left side measurements of study population aged 31-40 years

41–50 years age group

Evaluation of 111 participants, 56 males and 55 females (mean age = 45.79 years), was done. It was observed that males had slightly larger dimensions for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, right ear length above tragus, left ear length below tragus, right ear length below tragus, left ear tragus length, right ear tragus length, left ear concha length, right ear concha length, left ear lobule width and right ear lobule width as compared to females. On the other hand, females had slightly higher values for left ear concha breadth, right ear concha breadth, left ear lobule height and right ear lobule height as compared to the males. The P values for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, right ear length above tragus width and right ear concha length were <0.05 and hence statistically significant. All other variables of the ear between males and females in this age group had a P > 0.05 and hence were not significant [Tables 6 and 7]. The highest strength of correlation was seen for left ear lobule width–right ear lobule width (r2 = 85.7%), while the least was observed for left ear length above tragus–right concha ear length above tragus (r2 = 74.1%). The P value for all the correlations was found to be <0.05, and hence, the correlations were statistically significant [Table 12].

Table 6

Descriptive data of study population and comparison of mean left ear measurements among males and females aged 41-50 years

Table 7

Descriptive data of study population and comparison of mean right ear measurements among males and females aged 41-50 years

Table 12

Correlation of right and left side measurements of study population aged 41-50 years

51–64 years age group

Evaluation of 88 participants, 55 males and 33 females (mean age = 57.03 years), was done. It was observed that males had slightly larger dimensions for left ear length, right ear length, left ear breadth, right ear breadth, left ear length above tragus, right ear length above tragus, left ear tragus length, right ear tragus length, left ear concha length, right ear concha length, right ear lobule height, left ear lobule width and right ear lobule width as compared to females. On the other hand, females had slightly higher values for left ear length below tragus, right ear length below tragus, left ear concha breadth, right ear concha breadth and left ear lobule height as compared to the males. The P values for left ear tragus length and right ear tragus length were <0.05 and hence statistically significant. All other variables of the ear between males and females in this age group had a P > 0.05 and hence were not significant [Tables 8 and 9]. The highest strength of correlation was seen for left ear lobule height–right ear lobule height (r2 = 88.1%), while the least was observed for left ear length below tragus–right concha ear length below tragus (r2 = 67.7%). The P value for all the correlations was found to be <0.05, and hence, the correlations were statistically significant [Table 13].

Table 8

Descriptive data of study population and comparison of mean left ear measurements among males and females aged 51-64 years

Table 13

Correlation of right and left side measurements of study population aged 51-64 years

DISCUSSION

The ear is an extremely important constituent of the human face, functionally as well as esthetically. Every individual wants to have normal-appearing esthetically pleasing ears, and the demand for the same is highest in individuals with congenital or acquired deformities of the ear. Achievement of good functional and esthetic rehabilitation not only boosts one's self confidence but also translates into better social acceptance. The dimensions of the external ear and its various parts vary in different ethnic groups, and this requires that surgeons base their reconstructions on data specifically gathered from each of the ethnic groups. Thus, the current study attempted to furnish data regarding the external ear for normal individuals of Maharashtra.

During this study, it was observed that the shape, curves and lines of the ears of each person are entirely unique. Various shapes of the ear were observed in our study population, i.e., oval, round, triangular or rectangular and variations of those shapes. The position and size of the intertragal notch also varied from person to person. Another important observation in our study was that lobules may be attached or free. Lobules can also be narrow, wide, pointed, squared, flat, creased, etc.

In the last few years, ear dimensions have been investigated in various ethnic groups, using direct as well as indirect anthropometry and photography.[3510111213141516] In spite of the ethnical variations in the actual ear dimensions and position,[351115] all these studies found that the human external ear continues to grow even after skeletal maturity is reached. With increasing age, gradual changes in the microscopic structure of ear cartilage have also been reported, with decrease in the elastic fibers and in the density of cartilage cells.[10] Purkait and Singh[3] in their study even mentioned about the age-related decrease in skin elasticity and resilience. These microscopic changes may explain the macroscopic increments in ear dimensions with increasing age.

Irrespective of the ethnicity of the study population, the findings of Purkait and Singh,[3] Sharma et al.,[5] Ito et al.,[10] Azaria et al.,[11] Brucker et al.,[12] Meijerman et al.,[15] and Bozkir et al.[16] suggest that males have longer and wider ears as compared to females. In our study, males were found to have slightly longer and wider ears as compared to females in all age groups. Thus, gender dimorphism was demonstrated in our study, but the dimensional difference was not statistically significant.

In the present study, we observed that age-related dimensional changes were not identical for all variables: ear length increased faster and for a longer duration as compared to the ear width. This was in agreement with the findings of Purkait and Singh,[3] Meijerman et al.,[15] Niemitz et al.,[17] and Gualdi-Russo.[18] Various studies, such as those by Sharma et al.,[5] Ito et al.,[10] Kalcioglu et al.,[13] and Niemitz et al.,[17] reported that childhood and adolescent growth patterns were faster than those reported after adulthood.

The study conducted by Sforza et al.[9] compiled the sex- and age-related linear and angular dimensions of healthy Italian Caucasians ears. Their results showed progressive increase of ear dimensions with age; ear length increased more than ear width. There was no difference in the angles, ratios, and symmetry indices. As compared to the results obtained in their study, it was seen that for the similar age group, Italian Caucasian men had ear lengths comparable to Indian men, whereas ear length for females and ear breadth for both males and females were on the higher side in the Italian Caucasians.

Ekanem et al.[19] carried out direct measurement of the ear length, lobule length, and lobule width by calipers in a group of 217 adult Nigerians (aged 18–65 years) and the results indicate that the mean total ear height and mean lobular height were higher in the males than in the females while the females had a higher mean lobular width than that in males. The results of our study as compared to that of Ekanem et al.[19] establish that for the similar age, Maharashtrians have higher total ear length, comparable lobule length, and higher lobule width as compared to the Nigerians.

In the study conducted by Shireen and Karadkhelkar,[20] the mean values of ear length, ear breadth, lobule height and lobule width of right and left ears in the students (18–25 years) of Bidar, Karnataka, were compiled. Their study has established the existence of sexual dimorphism in external ear dimensions and also the differences between the auricular indices of both sides. Their results suggest a correlation between the ear variables. Our study establishes an insignificant gender dimorphism and a significant correlation between the different variables of the right and left side ears. The results obtained in our study suggest that people in the age group of 18–30 years and of Maharashtrian ethnicity, both men and women, have slightly smaller dimensions for ear length and lobule length but slightly higher values for ear width and lobule width as compared to their counterparts from Karnataka. This implies that within India also, people of different ethnicity have different dimensions of the various ear variables and hence the shape of the ear also varies.

Anthropometric study of the normal human auricle conducted on adult men in Central India by Purkait and Singh[3] concluded that in comparison with other ethnic groups, Indian males seem to have the smallest auricular and lobular lengths, although their respective widths are comparable with those of others. However, we observed that auricles of Nigerians were smaller in dimension than those of Maharashtrians. Analysis of our data shows that compared to Central Indians, people of Maharashtra had greater ear length but had lesser dimensions for ear breadth, lobule length, lobule width, concha length and concha width. Thus, even within the Indian subcontinent, widespread variations in the dimensions of the auricle exist.

CONCLUSION

Knowledge of the normal auricular dimensions is a prerequisite to be able to diagnose congenital malformations, syndromes, and acquired deformities of the ear. The dimensions of the ear are affected by age and sex. The external ear is not bilaterally symmetrical, but the asymmetry is not statistically significant. The contralateral normal ear serves as reference for otoplastic surgeries. Males have slightly larger external ears as compared to females. The human ear continues to grow even after the attainment of adulthood. The photogrammetric method adopted in the study for measurement of linear ear dimensions has potential in ear morphometry.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.