Planes of Reference for Orbital Fractures: A Technique for Reproducible Measurements of the Orbit on Computed Tomography Scans.

PURPOSE: Planes of reference for orbital fractures (PROF) was developed to standardize measurements made on orbital computed tomography scans. This study describes the use of PROF in determining the location along the orbital floor where the posterior ledge (PL) most commonly occurs. The transverse inclination and anterior-posterior inclination of the orbital floor will also be measured.

METHODS

This study evaluates 104 patients with unilateral orbital fracture. Fifty-two patients had intact infra-orbital margin (IM) and 52 had fractured IM. Facial computed tomography scans were analyzed using Osirix Lite Digital Imaging and Communications in Medicine Viewer version 7.0.1 (Geneva, Switzerland). All skull positions were standardized by orientation according to Frankfurt and mid-sagittal planes. Measurements of distance of PL from IM were determined in the sagittal view. Measurements of the inclination of the orbital floor in the transverse and anterior-posterior sections were done on the coronal and sagittal views respectively.

RESULTS

For patients with intact and fractured IM, the mean distances of PL from IM were 22.1 mm (95% CI: 21.2-23.0) and 21.1 mm (95% CI: 20.2-21.9) respectively. Mean transverse inclination was 19.4° (95% CI: 18.3-20.5). Mean anterior-posterior inclination was 15.5° (95% CI: 14.5-16.5).

CONCLUSION

Planes of reference for orbital fractures is a simple and effective method to acquire standardized measurements of the orbital cavity on computed tomography scans. Understanding the commonest location of PL and the orientation of the orbital floor in 3-dimensional space allows surgeons to perform dissection with greater precision.