From McNamara (1984) by permission.

From McNamara (1984) by permission.

Landmarks Measure from the condylion of the mandible (the most posterosuperior point of the condylar outline) to point A (the deepest midline point on the maxilla between the anterior nasal spine and the prosthion, which is the inferior labial termination of the cortical plate just above the maxillary incisors) (Fig 7.92).

Instruments Spreading calipers are used to measure this distance on a radiograph taken with "cephalostat."

Position Standard cephalometry—see introduction to Chapter 7.

Figure 7.92 Cephalometric measurement of effective midfacial length.

Figure 7.92 Cephalometric measurement of effective midfacial length.

Remarks Unfortunately, clinical evaluation of the maxilla and malar area is difficult and subjective. Relative prominence or flattening of the malar area is best appreciated in profile, relative to the prominence of supraorbital region. Similarly, prominence of the maxilla, in profile, should be relative to the mandible.

Outer Canthal, Nasal, Outer Canthal (ONC) Angle

Definition The angle subtended by the base of the nose in the midline to the outer canthi of the eyes.

Landmarks Draw an imaginary line from the outer canthus of the right eye to the base of the nose (base of the columella) in the midline. Draw a second imaginary line from the outer canthus of the left eye to the same point at the base of the nose. Measure the angle between those two lines

Instruments Two fixed measures such as a tape-measure or flexible ruler and protractor are necessary.

Position The head should be held erect (in the resting position) with the patient facing forward.

Alternative A young infant or child should be lying supine.

Remarks This angle is best measured from a full frontal photograph taken at a fixed distance from the patient (Fig. 7.94). It provides an estimate of both the spacing of the eyes and the upper facial height, and thus it will vary in the presence of hypo- or hypertelorism or an increase or reduction in upper facial height. Although best appreciated from a photograph, it can still provide useful information during clinical evaluation.

_ Figure 7.93 Measuring ONO angle.

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