A Morphometric Study of the External Ear: Age and Sex Related Differences

July 26, 2010

Patrick K. Sullivan, MD
Michael J. Brucker, MD
Jagruti Patel, MD

Author’s affiliation:

Brown Medical School
Rhode Island Hospital Department of Plastic Surgery
Providence, Rhode Island

ABSTRACT

The human ear is a defining feature of the face. Its subtle structures convey signs of age and gender that are unmistakable, however, not easily defined. With analysis of normative cross-sectional data, this study endeavors to show anatomic and aesthetic differences between men and women, as well as changes in ear morphology with age. 123 volunteers were randomly selected for this study. The cohort consisted of 89 women with age range 19 to 65 (median 42) and 34 men age range 18 to 61 (median 35). The average total ear height across the entire cohort for both left and right ears was 6.30cm. The average lobular height was 1.88cm. The average lobular width was 1.96cm. As expected based on head size, significant male/female differences were noted in the distance from the lateral palpebral commissure to both the helical root and insertion of the lobule. Measured distances for males were approximately 4.6% longer in both vectors compared to women. Similarly, the height of the pinna was significantly larger in men compared to women by approximately 6.5%. The average height and width of the lobule between male and female, however, were nearly identical. Analysis of age related data showed a significant difference in the total ear height between the subpopulations. When the lobular height was subtracted out of the total ear height, however, statistical significance was lost. This suggested that the lobule was the only ear structure that changed significantly with age. In addition, lobular width significantly decreased with age. This study establishes normative data for ear morphology and clearly demonstrates the changes of earlobe morphology with advancing age.

INTRODUCTION

The human ear is a defining feature of the face that is an important key in the natural, harmonious, aesthetically pleasing face. Its subtle structures convey signs of age and gender that are unmistakable, however, not easily defined. More specific to the plastic surgeon, we can look at an ear and know that it is not youthful, yet lack the parameters of a normal youthful ear. Thus we currently lack the information needed to correct it. Anatomy of the external ear has been detailed by many authors and texts.1, 2, 3 Brent and others have exhaustedly and brilliantly described the proper form and placement in ear reconstruction.4, 5, 6, 7, 8 Very little has been described, however, to guide the surgeon in rejuvenation of the ear.

Tolleth in 1978 published his heavily referenced work describing the proportions of the normal ear. 9 He described the position of the ear as well as the varied shape of the ear and earlobe. His article gives general proportions as surgical guides; however, their derivation is based on the author’s artistic perception. Though certainly a helpful contribution his assessments were almost entirely subjective.

We intend to describe the aesthetic proportions of the human ear based on normative cross-sectional data. Within this data, we will show anatomic and aesthetic differences between men and women, as well as changes in ear morphology with age. The ear conveys as much information on age and gender as other defining features of the face. It should be treated as such by the aesthetic plastic surgeon when desiring optimal facial rejuvenation that also does not inappropriately masculinize or feminize. With the appropriate normative data, we hope to better define the approach to ear rejuvenation.

MATERIALS AND METHODS

123 volunteers were randomly selected for this study. All volunteers were either employees of Rhode Island Hospital or affiliated with the Department of Plastic Surgery at Rhode Island Hospital. Age and sex of each volunteer were recorded. The cohort consisted of 89 women with age range 19 to 65 (median 42) and 34 men age range 18 to 61 (median 35). Standardized measurements of each ear included total ear height (TEH), lobular height (LH), lobular width (LW), distance from the lateral palpebral commissure to the root of the helix, and distance from the lateral palpebral commissure to the insertion of the lobule. TEH was measured as the distance from the caudal most projection of the lobule to the cephalic most projection of the helix. LH was measured as the distance from the caudal most projection of the lobule to the base of the tragal notch. LW was measured as the horizontal width of the lobule at the midpoint of the lobular height. All measurements were taken using a standard pinch caliper by a single investigator. An example of these measurements is demonstrated in figures 1 and 2.

Digital photographs were obtained of all 246 ears using a Nikon 990 digital camera. Photographs were taken with the volunteer in the standard lateral position, at a distance of one meter, with the camera lens set at approximately 105 mm focal length. Digital images were then archived and analyzed using the Mirror Professional software.

Using the Mirror software, the axis of the pinna was defined as a line that incorporates the midpoint curvature of the antitragus and evenly bisects the pinna. The axis of the lobule was defined as a line from the caudal most projection of the lobule through the same point on the antitragus. The angle of the lobule relative to the pinna was defined as the acute angle created by the intersection of the two axies.

Statistical analysis between male and female data was performed using the student’s t-test with a two tail distribution and a 95% confidence interval. Analysis of age related changes was performed using both analysis of variance and the Pearson test for linear correlation.

Figure 1. Caliper measurement of the lobule height, width, and total ear height.

Figure 2. Caliper measurement of the distance between the lateral palpebral commissure and both the root of the helix and the insertion of the lobule.

RESULTS

Combined data from all 246 ears is depicted in table 1. The average total ear height across the entire cohort for both left and right ears is 6.30cm. The average lobular height was 1.88cm. These values generate a LH to TEH ratio of 29.7%. The average lobular width was 1.96cm. The average height of the pinna, calculated by subtracting the lobular height from the total ear height, was 4.43cm.

Table 1 also lists data when the cohort is broken down into male and female subgroups. As expected based on head size, significant differences were noted in the distance from the lateral palpebral commissure to both the helical root and insertion of the lobule. Measured distances for males were approximately 4.6% longer in both vectors compared to women. Similarly, the height of the pinna was significantly larger in men compared to women by approximately 6.5%. The average height and width of the lobule between male and female, however, were nearly identical. Average lobular height was 1.89cm for men and 1.87cm for women. Average lobular width was 1.95cm for men and 1.97 for women.

For analysis of age related changes in ear anatomy, the cohort was divided into three subgroups. The age ranges of 18 to 30 years (group 1), 31 to 45 years (group 2), and 46 to 65 years (group 3) were arbitrarily selected based on overall age distribution within the cohort. A significant difference was noted in the total ear height, which increased from 6.19cm in group 1 to 6.45cm in group 3. When the lobular height was subtracted out of the total ear height, however, statistical significance was lost. The calculated height of the pinna was 4.40cm for group 1, 4.41cm for group 2 and 4.47 cm for group 3. This suggested that the lobule was the only ear structure that changed significantly with age. In fact, the lobule increased in height from 1.78cm in group 1 to 1.98cm in group 3 while the width decreased from 2.05cm in group 1 to 1.91cm in group 3. When the data was broken down further to analyze age related changes in ear anatomy based on sex, only lobular width in men failed to reach statistical differences across the age groups. Lobular height significantly increased with age for both men and women and lobular width significantly decreased with age for women only.

The angle between the axis of the pinna and the axis of the lobule was quite variable across the entire cohort. An average value of 8.9º posterior to the axis of the pinna was calculated with a standard deviation of 6.5º. No statistical difference could be found in any of the data subgroups.

Figure 3. Example of a patient with significantly elongated earlobes who requests facial rejuvenation (top). The one year post operative view is shown. Also shown is the pre- operative, operative planning and post-operative pictures of a different patient (bottom).

DISCUSSION

The ear is an important and under recognized defining feature of the face. Its shape conveys information about age and sex that is clear yet difficult to characterize. We have attempted to breakdown the basic aesthetic proportions of the ear and lobule with a broad cross-sectional study. The data generated from this study has been both predictable and unexpected.

One of the more thorough discussions of normal ear morphology as it relates to the rhytidectomy patient was by McKinney and colleagues in 1993.10 This study addressed specifically the treatment of the ear and earlobe in aesthetic surgery. Using similar measurement parameters to our own, they obtained data on one hundred “normal” volunteers and found a mean ear height of 6.5cm and a mean lobule height of 1.8cm. This correlates well with our data. McKinney did not, however, find a significant correlation between earlobe height and aging. No analysis between male and female volunteers was reported.

It is unclear why these results are disparate from our own. One possibility could be his method of calculation; which involved linear correlation between age and the ratio of earlobe height to total ear height. Our calculation of statistical significance compares age groupings and lobular height. When our data is analyzed for linear correlation between age and lobular height, we find a statistically significant coefficient of 0.25. Another possibility would be if McKinney only measured one ear from each volunteer. His methods with regard to this point are unclear. Nonetheless, if only the right ear from each of our volunteers is analyzed, the correlation coefficient remains statistically significant at 0.18.

When our data was analyzed with regard to sex of the volunteers, we uncovered some very interesting similarities. Our data clearly suggests that earlobe size does not vary significantly between men and women. While total ear size is larger in men, their earlobe height and width remain nearly identical to women in our cohort. Additionally, when this data was analyzed for age and sex changes, we find a consistent and statistically significant increase in earlobe height for both men and women. A majority of women and none of the men had pierced earlobes in our cohort. This suggests that the increase in earlobe height with age is not entirely due to the weight effects of earrings. Lengthening of the earlobe is more likely an unavoidable result of the aging process. Figure 3 shows a schematic of the morphologic changes of the earlobe with age.

In aesthetic earlobe reshaping, the ultimate goal is to achieve a more youthful appearance. We therefore draw upon data collected for the youngest subgroup of our cohort as our aesthetic standard. The average youthful earlobe is approximately 1.8cm long and 2cm wide at its midpoint. In general, the earlobe is gently curved from the distal extent of the helix towards the base of the lobule. In the case of the detached lobule, the shape of the earlobe then takes a circular turn and inserts slightly posterior to the anterior projection of the tragus. A height to width ratio of approximately 90% aids in creating the preoperative markings. Figure 3 shows a typical rhytidectomy patient with significantly elongated earlobes contributing to her aged appearance. The patient underwent endoscopic brow lift, composite rhytidectomy and earlobe reshaping. The method used for earlobe reshaping is shown in the pre-operative markings in Figure 3. The caudal projection of the lobule is excised as shown with a slightly greater amount of skin taken posteriorly. This conceals the closure along the posterior aspect of the lobular border.

Figure 4. Proposed changes in earlobe shape with advancing age (left to right). The helix is identical in all three depictions, with progressive lengthening and narrowing of the lobule.

Many authors have discussed the importance of proper earlobe placement in the rhytidectomy patient.10, 11, 12 Considerations such as ear morphology, flap tension and contraction from healing must be taken into account to assure an acceptable end result. Several authors have recommended specific parameters for inset of the earlobe during rhytidectomy. Their application in varying clinical situations, however, can often be quite subjective. In light of this, we attempted to quantify the normal position of the earlobe in relation to the upper two-thirds of the ear.

Similar to Tolleth, we defined the main axis of the ear to be the line passing through the midpoint curvature of the antitragus and evenly bisecting the pinna. The axis of the lobule incorporates the same antitragal point and passes through the caudal most projection of the earlobe on lateral view. While our results do not reach statistical significance, the trend is clearly toward the retrograde shift of the lobule from the upper two-thirds of the ear. Earlobes that insert anterior to the main axis of the ear tend to give a reclined appearance to the ear as a whole. When this look is recreated in the rhytidectomy patient, the end result is an undesirable pixy ear deformity. Our current practice is to inset the earlobe in a more cephalic position at a 20 degree axis which is posterior to the nine degree axis norm described in this report. The natural tendency is for the inset to migrate anterior and caudal with wound contraction. With proper placement, however, the final position of the earlobe should remain posterior to the main axis of the ear.

In conclusion, we believe that the data obtained in this study has generated some very useful parameters for ear morphology. Most important is the relation of ear and earlobe morphology to advancing age. Few surgeons would disagree with the notion that elongated earlobes are an undesirable result of aging. What we lacked was the data to describe both the age related change as well as the youthful mean. As depicted in figure 4, the normal lobule clearly changes from a short and wide structure in youth to one that is long and narrow. There are, however, many individuals who have large earlobes as one of their individual characteristics. When these earlobes become even larger with aging a much more noticeable problem emerges. These are the patients in whom earlobe contouring is particularly indicated. We have now gained the parameters necessary to reshape and rejuvenate the ear.

CORRESPONDING AUTHOR

Patrick K. Sullivan, MD
Associate Professor of Plastic Surgery
Brown Medical School
Rhode Island Hospital Department of Plastic Surgery
2 Dudley St., Suite 450
Providence, Rhode Island, 02905

REFERENCES

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