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The apical angle: a mathematical analysis of the ellipse
B R Moody1, J E McCarthy, R D Sengelmann
1Division of Dermatology, Washington University School of Medicine, St. Louis, Missouri, USA.
Background:
The elliptical excision is a common surgical procedure. The dermatologic literature predominantly describes an excisional geometry with a 3:1 length:width ratio and an apical angle of 30 degrees.
Objective:
To analyze the elliptical excision by applying mathematical principles and define the apical angle and its relationship to the length:width ratio.
Methods:
We examined numerous examples of elliptical excisions as presented in the dermatologic literature. We analyzed the geometry of the excisions and defined it mathematically.
Results:
The apical angle of a 3:1 elliptical excision is not 30 degrees. The true apical angle varies from 37 degrees to 74 degrees depending on excisional geometry.
Conclusion:
The commonly presented apical angle of 30 degrees is incorrect and does not reflect the true apical angle of elliptical excisions.
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