St

Sphenoid Sinus Ostium

Figure 29 Sagittal (a) and endoscopic (b) views showing the approximate level of entry into the sphenoid sinus if the posterior MOF (solid arrow) versus the anterior MOF (dotted arrow) are used. Using the posterior MOF will guide the surgeon into the middle third of the sphenoid sinus (S). This corresponds to the area of the sphenoid natural ostium. The anterior MOF or maxillary natural ostium area will guide the surgeon slightly more inferiorly through harder bone, into the inferior third of the sphenoid. The dotted line represents the posterosuperior angulation of the orbital floor toward the orbital apex. PE = posterior ethmoid.

Figure 29 Sagittal (a) and endoscopic (b) views showing the approximate level of entry into the sphenoid sinus if the posterior MOF (solid arrow) versus the anterior MOF (dotted arrow) are used. Using the posterior MOF will guide the surgeon into the middle third of the sphenoid sinus (S). This corresponds to the area of the sphenoid natural ostium. The anterior MOF or maxillary natural ostium area will guide the surgeon slightly more inferiorly through harder bone, into the inferior third of the sphenoid. The dotted line represents the posterosuperior angulation of the orbital floor toward the orbital apex. PE = posterior ethmoid.

Figure 30

Sagittal view showing the usual trajectory of dissection when the MOF and antrostomy ridge are kept in view at all times.

Figure 31 Sagittal view showing the columnellar measurements to the anterior face of the posterior ethmoid (horizontal portion of the middle turbinate basal lamella) at the MOF level (dotted arrow). This measurement is approximately 5 cm. The solid arrow denotes the columnellar measurement to the anterior face of the sphenoid sinus (S) or posterior wall of the posterior ethmoid sinus (PE) at the MOF level. This measurement is generally around 7 cm.

Figure 31 Sagittal view showing the columnellar measurements to the anterior face of the posterior ethmoid (horizontal portion of the middle turbinate basal lamella) at the MOF level (dotted arrow). This measurement is approximately 5 cm. The solid arrow denotes the columnellar measurement to the anterior face of the sphenoid sinus (S) or posterior wall of the posterior ethmoid sinus (PE) at the MOF level. This measurement is generally around 7 cm.

Figure 32 Endoscopic view showing the sphenoid ostium (asterisk), which has been enlarged inferiorly and medially. ST = superior turbinate. MT = middle turbinate. PE = posterior ethmoid. M = maxillary sinus. Arrows denote the antrostomy ridge.

Figure 33 Sagittal (a) and endoscopic (b) views after completion of sphenoethmoidectomy. The sphenoid ostium has also been enlarged medially and inferiorly toward its floor. The common wall between the sphenoid (S) and posterior ethmoid (PE) has been removed. Note the relationship of these cavities to the MOF (arrow). Most of the posterior ethmoid cavity is located above this line. Conversely, most of the sphenoid is located below this line. MT = tail of middle turbinate. B = area of ethmoid bulla. I = infundibular wall.

Figure 34 Sagittal (a) and endoscopic (b) views illustrating the relationship between the horizontal (black dotted line) and vertical (white dotted line) ridge of the antrostomy and the adjacent anterior ethmoid or ethmoid (B) and the posterior ethmoid sinus (PE). The transition area (solid white line) between the horizontal and vertical ridge represents the approximate level where the posterior ethmoid is entered more laterally to this point, through the horizontal portion of the middle turbinate basal lamella.

Figure 34 Sagittal (a) and endoscopic (b) views illustrating the relationship between the horizontal (black dotted line) and vertical (white dotted line) ridge of the antrostomy and the adjacent anterior ethmoid or ethmoid (B) and the posterior ethmoid sinus (PE). The transition area (solid white line) between the horizontal and vertical ridge represents the approximate level where the posterior ethmoid is entered more laterally to this point, through the horizontal portion of the middle turbinate basal lamella.

Basal Lamella Middle Turbinate Vertical

J. Frontal Sinusotomy (Figures 35 and 36)

The frontal sinus is identified by drawing a line parallel to the bony nasolacrimal duct and directed superiorly from the anterior border of the antrostomy (i.e., natural ostium area) to a point 5 to 10 mm behind the anterior attachment (axilla) of the middle turbinate. The correct point of entry will be directed superomedially away from the wall of the orbit and anteriorly away from the anterior ethmoid artery. The anterior ethmoid artery is located an average of 20 mm (range 17-25 mm) from the anterior attachment of the middle turbinate (50).

Palpation of the frontal sinus' posterior wall is the key to identifying the frontal sinus and opening the frontal sinus ostium. The septations that comprise the roof of the suprabullar cells, and the agger nasi or frontal cells, are gently displaced anteroinferiorly with the angled probe to avoid

Was this article helpful?

0 0

Post a comment