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Frontal Sinusotomy—Draf I and IIa


Introduction

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    Dissection of the frontal recess is the most difficult of the basic endoscopic dissections.

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    Care must be taken to preserve the mucosa surrounding the frontal recess. Stripping of mucosa can result in postoperative stenosis and neo-osteogenesis.

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    The frontal recess is difficult for another reason: the variable anatomy that can present an obstruction within the frontal recess. Frontal recess cells, posteriorly located frontal bullar cells, and intersinus septal cells all vary in presence and location from patient to patient but must be dissected for a complete frontal recess dissection ( Fig. 9.1 ).

    Fig. 9.1, Schematic drawing of drainage pathways in sagittal view. The frontal sinus drainage pathway is shown in red. The posterior ethmoid and sphenoid sinus drainage pathways through the sphenoethmoid recess are indicated in green. The drainage pathways from the anterior ethmoid are shown in purple. The green-shaded portion should be removed in frontal recess dissection.

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    Although a frontal recess dissection can be performed without removing the ethmoid bulla, a more complete and thorough surgery is possible only after the skull base has been cleared of all superior ethmoid bony partitions.

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    When performed as part of complete functional endoscopic sinus surgery, the frontal recess dissection follows the completion of the maxillary antrostomy, sphenoidotomy, and complete ethmoidectomy.

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    Proper postoperative care and débridements are critical for long-term patency of the frontal recess.

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    Other keys to success are the following:

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      Proper instrumentation

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      Use of angled through-cutting instruments and probes specially designed for the frontal recess

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      Good visualization with a minimum of a 45-degree and preferably a 70-degree endoscope

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      Maintenance of a well-mucosalized frontal recess

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    Endoscopic frontal procedures can be described by the following classification, based on Wolfgang Draf’s initial work in 1991 using the microscope for endonasal frontal recess dissections:

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      Draf I: Removal of the superior uncinate with preservation of the agger nasi ( Fig. 9.2 )

      Fig. 9.2, Schematic drawings in sagittal (A) and coronal (B) views showing the portions of cells and bones removed in a Draf I dissection. The frontal recess cells, anterior ethmoid, uncinate process, and infundibulum are cleared, but the internal frontal sinus ostium (or thinnest part of the frontal recess drainage pathway) is not manipulated.

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      Draf IIa: Removal of all cells within the frontal recess ( Fig. 9.3 )

      Fig. 9.3, Schematic drawings in sagittal (A) and coronal (B) views showing the structures removed in a Draf IIa frontal recess procedure. A Draf IIa dissection removes the cells excised in a Draf I procedure; in addition, it removes all cells lateral to the middle turbinate attachment and opens the internal frontal ostium.

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      Draf IIb: Draf IIa dissection plus removal of the ipsilateral floor of the frontal recess ( Fig. 9.4 )

      Fig. 9.4, Schematic drawings in sagittal (A) and coronal (B) views showing the structures removed in a Draf IIb dissection. The Draf IIb procedure includes the dissection of the Draf IIa procedure with the addition of the ipsilateral middle turbinate attachment to the floor of the frontal sinus; it, therefore, removes all the ipsilateral frontal sinus floor from septum to orbital wall.

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      Draf III: Bilateral Draf IIb dissection plus removal of the intersinus septum and the superior nasal septum to create a single common opening ( Fig. 9.5 )

      Fig. 9.5, Schematic drawings in sagittal (A) and coronal (B) views showing the structures removed in a median frontal sinus drainage, or Draf III, procedure, also called a frontal sinus drill-out or endoscopic modified Lothrop procedure. The procedure includes removal of the midline septum, both middle turbinate attachments to the floor of the frontal sinus, and all of the frontal sinus floor from orbital wall to orbital wall.

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    Nearly all primary cases and a substantial number of revision cases can be adequately treated using a Draf IIa procedure. This chapter discusses the technique for a Draf IIa dissection; the following chapters are devoted to the Draf IIb and Draf III procedures.

Anatomy

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    The anatomic shape of the frontal sinus and frontal recess can be visualized as an hourglass, with the narrowest point corresponding to the frontal sinus ostium.

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    For the purpose of dissection, the frontal recess can be thought of as a box with four borders ( Fig. 9.6 ). Enlarging the recess requires dissection of each wall of the box:

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      Anterior: the superior uncinate process and agger nasi cell

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      Medial: the lateral lamellae of the skull base and intersinus septum, and the attachment of the middle turbinate

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      Posterior: the supraorbital ethmoid cell and the anterior border of the ethmoid bulla

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      Lateral: the medial wall of the orbit

    Fig. 9.6, Schematic drawings showing the boundaries of the frontal recess. (A) In the coronal plane, the medial boundary is the attachment of the middle turbinate. The lateral boundary is the orbit. (B) In the sagittal plane, the anterior border is the anterior wall of the agger nasi cell, which is continuous with the anterior buttress of the nasal spine, also called the nasal beak. The posterior-superior border is the attachment of the ethmoid bulla and/or the suprabullar cell.

Cells of the Frontal Recess

Agger Nasi Cell

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    The most anterior of the ethmoid air cells, the agger nasi cell often has the appearance of a bulge in the superior uncinate process. The cap of the agger nasi cell often makes the floor of the frontal recess ( Fig. 9.7A ).

    Fig. 9.7, (A) Schematic drawing showing an agger nasi cell, suprabullar cell, and frontal bullar cell, which are best appreciated on a sagittal section (as depicted here). (B) Schematic drawing in coronal view of a supraorbital cell, which pneumatizes up and over the orbit. One should be aware of its orientation just superior and anterior to the anterior ethmoid artery.

Interfrontal Sinus Septal Cell

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    An interfrontal sinus septal cell is a cell that arises along the midline septum of the frontal sinus. As it pneumatizes, it narrows the frontal recess from medial to lateral (see Fig. 9.7B ).

Supraorbital Ethmoid Cell

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    A supraorbital ethmoid cell pneumatizes into the frontal bone over the orbit and behind the frontal recess. It may extend lateral to the frontal recess (see Fig. 9.7B ).

Suprabullar Cell

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    A suprabullar cell arises above the ethmoid bulla and pneumatizes up to the attachment of the bulla to the skull base. It is best seen in sagittal view (see Fig. 9.7A ).

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