ABSTRACT
BACKGROUND AND OBJECTIVES: The anterior ethmoid canal is the important surgical landmark in endoscopic sinus surgery, intranasal ethmoidectomy, and frontal sinus surgery. However it is not enough to evaluate the anterior ethmoid canal by coronal OMU CT, especially relating anterior to posterior relationship of the anterior ethmoid canal. The pulpose of this study is to evaluate the anterior ethmoid canal in 1 mm axial OMU CT and measure the five parameters relating the anterior ethmoid canal. MATERIALS AND METHODS: A prospective study was performed in 100 sinuses of 50 patients with chronic sinusitis who underwent endoscopic sinus surgery from May through July of 1998. RESULTS: The anterior ethmoid canal is well demonstrated by 1 mm axial OMU CT. The average of five parameters are 6.2+/-1.5 mm, 6.4+/-4.3 mm, 18.5+/-3.9 mm, 26.5+/-5.6 mm, 24.6+/-14.6degrees. However, there is no difference between the right and left side statistically. We observed that the anterior ethmoid canal is located just posterior to the frontal recess without anterior ethmoid air cell in front of the antirior ethmoid canal in 23%. CONCLUSION: The anterior ethmoid canal is well remarked by the 1 mm axial OMU CT. The length and directional angle of the anterior ethmoid canal is individually variable and there is no anterior ethmoid air cell in front of the anterior ethmoid canal in 23%. In these cases, the anterior ethmoid canal is more likely to be injured. So axial OMU CT may be useful in the radiologic evaluation for endoscopic sinus surgery in chronic sinusitis.