Osteoplastic Obliteration of the Frontal Sinus

Introduction

In the preendoscopic era, the osteoplastic flap procedure was the accepted method of management of frontal sinusitis. Initial approaches described in the late 19th century (e.g., the Reidel procedure) conceptualized the complete exenteration of the sinus, including the anterior wall, which of course resulted in a significant cosmetic deformity, reserved for only the most severe disease processes. The more modern osteoplastic obliteration (using abdominal adipose tissue) was described in the 1940s and popularized by the 1970s. It is a versatile surgical approach that provides wide exposure of the frontal sinus and allows for the definitive management of inflammatory, infectious, and neoplastic disease processes. The procedure has maintained a reputation for reliability, with long-term success rates greater than 90% in most reports, even when used in patients with refractory chronic frontal sinusitis.

Advances in endoscopic techniques have largely replaced open sinus surgery. Instead of an obliterative approach, transnasal surgery allows the restoration of function to a diseased sinus, by establishing a permanent drainage pathway. This approach is preferred, as it avoids external scars and unlike open procedures maintains normal sinus physiology. However, there remain certain situations—for example, neoplasms of the frontal sinus or extreme lateral based pathology—in which endoscopic visualization is limited. The osteoplastic flap procedure continues to be an essential surgical approach in these instances.

Key Operative Learning Points

1.
The osteoplastic flap procedure should be considered in cases that are inaccessible to endoscopic techniques, particularly in the setting of refractory chronic sinusitis after previous surgical failure.
2.
A bicoronal flap, raised in the subgaleal plane, is generally used to prevent injury to the scalp neurovasculature.
3.
To prevent intraoperative complications, the frontal sinus must be accurately outlined using plain x-ray film, mini-trephination technique, or image guidance, prior to making the osteotomies.
4.
For noninflammatory pathology, sinus obliteration may not be necessary; instead an endoscopic procedure can be used to create a patent nasofrontal outflow tract.
5.
When sinus obliteration is necessary, key principles must be adhered to for long-term success.
- a.
  Meticulous removal of all visible sinus mucosa
- b.
  Removal of the inner cortex of the anterior wall of the sinus with a cutting and/or diamond burr
- c.
  Permanent occlusion of the nasofrontal outflow tract
6.
While abdominal adipose tissue is currently considered the standard tissue for obliteration of the frontal sinus, more recently described techniques including a rotational pericranial flap or tissue-engineered materials may also be considered.

Preoperative Period

The key to the preoperative patient evaluation is determining which patient would be best served by an open surgical approach given the advanced instrumentation, surgeon comfort, and ease of access to the frontal sinus with standard endoscopic approaches. The osteoplastic flap approach will be of particular use in situations where wide surgical exposure for direct instrumentation of the sinus is necessary. It may be applied in multiple clinical settings (e.g., trauma, neoplasm, or chronic sinusitis), and thus the preoperative evaluation must address the particular disease process at hand.

Successful endoscopic sinus surgery requires the establishment of an appropriate corridor to fully visualize the disease process and establish a patent sinus drainage pathway. Findings such as significant scar formation or osteoneogenesis within the frontal recess (usually due to previous surgical procedures) often portend poor long-term results with transnasal approaches. An anatomically inaccessible pathology located in the far lateral or anterior table of the sinus as well as large fibro-osseous lesions (e.g., osteoma) are difficult to remove endoscopically and may benefit from an osteoplastic approach.

The indications for osteoplastic obliteration will likely continue to evolve over time, with advancement of endoscopic techniques and instrumentation. Perioperative planning requires the combination of a detailed examination of the head and neck, including endoscopy, and high-resolution imaging (usually computed tomography [CT]) to define the most appropriate surgical approach.

History

1.
History of present illness
- a.
  A focused history should include questions about common symptoms of frontal sinus and nasal pathology, including frontal pressure/pain, headache, hyposmia/anosmia, nasal obstruction, epistaxis, generalized fatigue, or a sensation of postnasal drainage.
- b.
  For presumed chronic inflammatory disease, review the current medical regimen (e.g., nasal corticosteroids or saline irrigations) and the effectiveness of these nonsurgical treatments for control of symptoms.
- c.
  Signs of intraorbital pathology such as diplopia or decreased visual acuity should be specifically evaluated.
- d.
  Red flags for a malignant or acute life-threatening illness, such as mental status changes, weight loss, clear (cerebrospinal fluid [CSF]) rhinorrhea, sensory deficits along trigeminal nerve distribution, current history of immune suppression, or severe/progressive pain, should be considered.
2.
Past medical history
- a.
  Prior treatment
  - All previous sinonasal procedures must be detailed, to help determine if an open frontal sinus procedure is indicated. This should include a review of past sinus procedures and pathologic specimens.
  - Previous scalp incisions or surgical incisions are important to assess, as this may limit the viability of the standard bicoronal approach typically used for the osteoplastic flap procedure.
- b.
  Medical illness
  - Review for systemic comorbidities (particularly cardiac disease, chronic pulmonary disease, diabetes mellitus)
- c.
  Past surgical history
- d.
  Family history
- e.
  Allergy assessment
- f.
  Review of current medications

Physical Examination

1.
Head/face:
- a.
  Standard facial assessment, with a particular focus on facial symmetry and facial nerve function. Sensory examination particularly along V1 and V2 territories should be documented.
- b.
  Palpation along the orbital rim and frontal bone should be carried out, both to assess for point tenderness and to address the integrity of the anterior table of the frontal sinus and the presence of a mucocele. The position of the eyes should be examined, and any displacement should be noted.
- c.
  In the case of recent traumatic injury, a thorough inspection should be undertaken to review for facial lacerations, bruising, or bony step-offs that could be indicative of fracture sites. The overall stability of the midface and mandible should also be assessed.
2.
Orbit:
- a.
  Extraocular motion
- b.
  Visual field assessment
- c.
  Assess the position of the globe (i.e., proptosis or enophthalmos).
- d.
  A referral to ophthalmology for any concerning abnormal findings is strongly suggested.
3.
Nasal examination:
- a.
  Standard external nasal examination with assessment of external/internal nasal valves. Note presence/absence of significant septal deformity or hypertrophy of the inferior turbinates.
- b.
  Intranasal examination should evaluate for an intranasal mass, polypoid/inflammatory changes, or obvious purulence. If purulent sinonasal discharge is identified, a specimen should be taken for culture and sensitivities.
4.
Nasal endoscopy:
- a.
  This examination is critical to define the surgical approach for frontal sinus disease, particularly in the previously operated nose. Adequate topical anesthesia should be applied for patient comfort. This examination is often best performed with 0- and 30-degree rigid endoscopes, as additional instruments (i.e., curved suctions) can be used to clear debris when present.
- b.
  The presence/absence of key anatomic landmarks should be noted, particularly the middle turbinate (and its basal lamella), uncinate process, and bulla ethmoidalis.
- c.
  With an angled telescope, an attempt should be made to visualize the frontal recess. Particularly note the presence of polypoid disease or synechiae formation if previous surgery has been performed.
5.
Comprehensive head/neck and general medical examination:
- a.
  Overall health and mental status
- b.
  A thorough examination of the head and neck should be carried out.
- c.
  Cardiovascular, pulmonary, and neurologic examination
- d.
  Skin assessment

Imaging

1.
CT imaging:
- a.
  A high resolution CT scan of the sinuses is the most useful method in the evaluation of frontal sinus disease. This provides an optimal assessment of the position of the frontal sinus in relation to key landmarks such as the anterior skull base, crista galli, and frontal lobes. The interface between inflammatory pathology and the bony anatomy of this region is also clearly delineated ( Fig. 114.1 ).
- b.
  The structure of the anterior and posterior table of the sinus should be visualized. Significant defects in the bony structure of the sinus may prevent safe obliteration of the sinus and require the use of a different surgical approach.
- c.
  If surgical image guidance is considered, image slice thickness should generally not exceed 2 to 3 mm.
- d.
  Evaluation of the bony anatomy of the frontal recess is best performed with CT. This will help classify the pattern of frontal cells on the basis of the Kuhn classification, which may indicate a more challenging endoscopic dissection.
  - Type I: Single frontal recess cell above the agar nasi
  - Type II: Tier of cells above the agar nasi
  - Type III: Large cell pneumatizing from the frontal recess into the sinus
  - Type IV: Isolated frontal sinus cell
- e.
  CT is also particularly useful for evaluating traumatic maxillofacial injuries and identifying benign fibro-osseous lesions (e.g., osteomas).
2.
Magnetic resonance (MR) imaging:
- a.
  Due to lack of detailed bony definition, MR is usually considered as an adjunctive modality. It is, however, particularly beneficial in certain situations due to the ideal soft tissue definition provided.
  - Identifying benign/malignant neoplasms of the frontal sinus, with gadolinium-enhanced imaging
  - For differentiating solid tumors from inflammatory secretions or expansile mucoceles that have specific signal characteristics, particularly on T2-weighted or contrast-enhanced imaging ( Fig. 114.2 )
- b.
  MR is also particularly useful in the evaluation and diagnosis of pathology that has spread to intraorbital or intracranial compartments.
3.
Radiography:
- a.
  Traditionally a 6-foot Caldwell view plain film radiograph has been used for surgical guidance prior to the osteoplastic flap procedure.
- b.
  From this film, a template of the frontal sinus dimensions can be made to help with the proper placement of the osteotomies along the anterior table of the sinus.

Indications

1.
Recurrent chronic sinusitis after failed endoscopic sinus surgery
2.
Inaccessible frontal mucoceles, usually lateral to the midpupillary line and superior to half the height of the posterior table
3.
Severe trauma involving the frontal sinus outflow tract or with CSF leak, not amenable to endoscopic management
4.
Benign or malignant tumors of soft tissue or bone (osteomas) of the frontal sinus, unable to be completely resected via an endoscopic approach

Contraindications

1.
Any disease process amenable to endoscopic management
2.
Cases in which greater than 25% of the anterior or posterior table of the frontal sinus is absent. In these cases, obliteration will likely be unsuccessful due to a limited vascular supply. For anterior table defects, the Reidel procedure may be necessary, while frontal sinus cranialization should be considered for posterior table defects.
3.
Patients whose medical comorbidities preclude a general anesthetic

Preoperative Preparation

1.
Standard perioperative evaluation with history-directed preoperative testing and medical consultations, if indicated
2.
Patient counseling and surgical consent
3.
Review preoperative imaging, and ensure adequacy for image guidance, if deemed necessary.
4.
Review pathology from any previous surgery.
5.
A template outlining the frontal sinus should be made using the x-ray film from the 6-foot Caldwell view. The film should be sterilized for intraoperative use.

Operative Period

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