Bony Interobital Distance Cephalometric

Definition The distance between the medial margins of the bony orbit (Fig. 7.43).

Landmarks Measure between the medial walls of the orbits, at approximately the level of the junction between the medial angular process of the frontal bone and the maxillary and lacrimal bones (the dacrion).

Instruments Spreading calipers or a graduated ruler can be used.

Graduated Ruler

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Age from birth (years)

Figure 7.43 Bony interorbital distance, birth to 16 years. From Hansman (1966) and Currarino and Silverman (1960), by permission.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Age from birth (years)

Figure 7.43 Bony interorbital distance, birth to 16 years. From Hansman (1966) and Currarino and Silverman (1960), by permission.

Position The head is held in a cephalostat. Nonrotated, posteroanterior, Roentgen projections of the skull are used, exposed at a target-table-top distance of 100 cm, with a patient-film distance of 5 cm.

Remarks The dacrion is medial to the inner canthus. It is found at the junction of the nasal process of the frontal bone, the frontal process of the maxilla, and the lacrimal bone where the medial canthal ligament is attached. Since the interorbital space is occupied mainly by the ethmoid, it is probable that this bone is narrower than normal when the bony interorbital distance is small. This radiological measurement is more accurate than a soft tissue measurement.

Pitfalls If the skull film is rotated, the bony interorbital distance cannot be measured.

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