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Updated: Mar 28, 2026
State of the Art Cranial Ultrasound Imaging in Neonates
Published on: February 2, 2015
The primal sagittal plane of the head: a new concept
1Department of Oral and Maxillofacial Surgery, Houston Methodist Hospital, Houston, TX, USA; Institute for Academic Medicine, Houston Methodist Hospital, Houston, TX, USA; Department of Surgery (Oral and Maxillofacial Surgery), Weill Medical College, Cornell University, New York, USA.
Abstract:
To assess facial form, one has to determine the size, position, orientation, shape, and symmetry of the different facial units. Many of these assessments require a frame of reference. The customary coordinate system used for these assessments is the 'standard anatomical frame of reference', a three-dimensional Cartesian system made by three planes: the sagittal, the axial, and the coronal. Constructing the sagittal plane seems simple, but because of universal facial asymmetry, it is complicated. Depending on the method one selects, one can build hundreds of different planes, never knowing which one is correct. This conundrum can be solved by estimating the sagittal plane a patient would have had if his or her face had developed symmetrically. We call this the 'primal sagittal plane'. To estimate this plane we have developed a mathematical algorithm called LAGER (Landmark Geometric Routine). In this paper, we explain the concept of the primal sagittal plane and present the structure of the LAGER algorithm.
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