Frontal Sinus Stenting Techniques Technique

Various techniques may be used for the placement of frontal sinus stents, including intranasal endoscopic placement, "above and below" techniques using both endoscopic frontal sinusotomy and frontal sinus trephination, and external approaches. ^[5] Despite the approach used, several common key points can decrease the risk of restenosis during frontal sinusotomy. First, all efforts must be made to preserve the middle turbinate. Second, agger nasi cell walls including dome and any osteitic bone should be removed. Anterior ethmoid cells should also be removed, and midfrontal or supraorbital cells should be opened. Mucosal preservation is paramount, especially along the posterior and medial walls. Finally, working from posterior to anterior improves surgical safety by minimizing skull base injury. ^[7]

Endonasal stent placement using standard endoscopic sinus instrumentation is the least invasive approach and preferred method of frontal sinus stenting. In this technique, the surgeon completes an uncinectomy, anterior ethmoidectomy, and frontal sinusotomy. Care must be taken not to destabilize the middle turbinate. The frontal sinus surgical ostium (see the image below) is inspected to ensure it will accommodate a stent with minimal pressure on the surrounding mucosa or bone.

Endoscopic placement of right frontal sinus stent after a revision Draf 2b frontal ostioplasty in a patient with previous surgery and radiation for esthesioneuroblastoma. (A) 1/100 thick silastic sheet is cut into a T shape based on the size of the frontal ostium, (B) right frontal ostium; view with a 70º endoscope, (C) the sheet is to be rolled into a stent, grasped with giraffe forceps, and the T flange inserted into the frontal sinus, (D) the rolled part of the stent lines the area of the frontal recess.

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Agger nasi cells and obstructing soft tissue and osteitic bone should be removed as needed to enlarge the frontal sinus outflow tract. The choice of stent type and size depends on the size of the neo-ostium. The frontal sinus is cannulated from below using an up-curved suction tip (with suction off), curved curette, guide wire, or specially designed stent introducer. The frontal sinus stent can then be slid over the cannulating instrument, which is angled at 45º, and advanced upward into the frontal sinus. The stent canal is so be introduced with the help of frontal giraffe instruments (see the image above).

Stents can then be trimmed to approximate the level of the inferior border of the middle turbinate or at the midlevel of the vertical septal height. ^[5] Care must be taken at this step, as stents with insufficient length are prone to obstruction with granulation tissue and stents with excess length predispose to airflow obstruction and crusting. ^[5] Finally, the frontal sinus can be irrigated via the stent. ^[9]

The above (retrograde) and below technique may be useful in cases of refractory frontal sinus disease with unfavorable anatomy in which purely endoscopic access is not possible. This approach uses a combination of external frontal sinus trephination and intranasal endoscopy, which improves access to the entirety of the frontal sinus and thus facilitates treatment of disease in areas with limited access. Frontal sinus trephination is useful in enhancing visualization in complex anatomy due to the presence of type III and type IV frontal cells. It also has been proposed to allow for better visualization of the frontal sinus outflow tract and more precise stent placement. ^[5] This technique, however, is more invasive than a simple endonasal approach and requires an external incision.

Preoperative CT scans should be studied to determine the optimal frontal sinus entry site, and injury to the nasofrontal recess should be avoided. Stereotactic image guidance may also be helpful during frontal sinus trephination. Once the entry site is planned, a 1-2 cm curvilinear incision is made medial to the brow along the supraorbital rim. This incision may be hidden within the brow by moving the brow medially over the planned area of trephination. Injury to hair follicles is prevented by beveling the incision parallel to the follicles, as well as avoiding the use of electrocautery. ^[5]

The periosteum is elevated along the floor of the frontal sinus and over the anterior aspects of the frontoethmoid suture line, ^[14] taking care not to injure to the supraorbital nerve. Trephination of the frontal sinus is then performed with a cutting burr or osteotome. Once the mucosal lining of the sinus is exposed, it should be incised sharply to minimize the degree of mucosal injury. Alternatively, a frontal sinus mini-trephine can be placed and used for irrigation of the frontal sinus with Fluorescein-stained saline. The frontal sinus drainage pathway can then be followed endonasally by following the Fluorescein-stained saline into the frontal sinus. ^[27]

At this point, endoscopic visualization via the frontal trephination is conducted. ^[5] Once the natural drainage pathway is identified, the frontal neo-ostium is opened, and a soft frontal sinus stent is introduced either endonasally or through the trephination and advanced through the nasofrontal recess. A suture tail, which can be grasped from below, may assist with more precise placement.

The modified Lynch frontoethmoidectomy is an older technique described by Neel and colleagues in 1976, ^[4] the use of which has declined due to the advent of endoscopic technology. This technique uses a modified Lynch frontoethmoidectomy. ^[6] Contemporary use of the external frontoethmoidectomy in the United States is rare. In this procedure, first an intranasal ethmoidectomy and frontal sinusotomy are performed. Subsequently, a modified Killian incision is made, extending from the medial brow onto the nasal sidewall. The periosteum is elevated and retracted along with the trochlea of the superior oblique muscle and orbit. The medial canthus is cut, exposing bone.

A portion of the lacrimal bone is removed at the superomedial angle of the orbit, allowing for exposure and removal of a segment of the floor of the frontal sinus. With this exposure, the nasofrontal tract can be enlarged with a Kerrison rongeur. A stent is then passed from above and advanced into the widened nasofrontal tract. The stent is trimmed intranasally to the appropriate length and may be anchored to the nasal septum or lateral nasal wall with suture. ^[5] Currently, this technique is rarely if ever used given the advances in image-guidance and instrumentation making less-invasive approaches feasible.

Frontal sinus stents may help prevent scar tissue formation across the frontal sinus opening, thereby allowing epithelialization to occur along the surface of the stent. Most studies have used subjective improvement or resolution of frontal sinus symptoms as the main outcome measure. Objective data, however, was gathered by Weber et al, who compared the long-term results of patients with and without stents in a prospective fashion, finding a patent frontal outflow tract in 80% of stented patients versus 33% of unstented patients. ^[28] Rains reported a 94% patency rate over 8-46 months follow-up with the his proprietary stent. ^[7] Banhiran et al, however, reported no difference in ostium patency and symptom improvement between short-term stenting and nonstented patients after endoscopic-modified Lothrop procedure. ^[29]

The authors use frontal sinus stenting in very limited situations. The most frequent indication in their experience is with a modified Lothrop cavity with significant demucosalized bone due to the drill-out procedure (see the image below).

Endoscopic placement of right frontal sinus stent after a revision Draf 2b frontal ostioplasty in a patient with previous surgery and radiation for esthesioneuroblastoma. (A) 1/100 thick silastic sheet is cut into a T shape based on the size of the frontal ostium, (B) right frontal ostium; view with a 70º endoscope, (C) the sheet is to be rolled into a stent, grasped with giraffe forceps, and the T flange inserted into the frontal sinus, (D) the rolled part of the stent lines the area of the frontal recess.

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Middle meatal spacers (absorbable or nonabsorbable packing) and suture medialization of the middle turbinate can be used to preempt middle turbinate lateralization and prevent adhesion formation as needed. Various soft stents are now available, including a recently FDA-approved steroid-eluting bioabsorbable implant. ^[30] An endoscopic endonasal approach to the frontal recess is preferred. Frontal sinus trephination or mini-trephine with Fluorescein-stained saline can be used with an above and below approach, as an alternative. Overall, frontal sinus stents are well tolerated by patients. The duration of stenting is variable. Frontal sinus stenting appears to be a useful intervention for prevention of neo-ostium restenosis in selected patients.

Frontal sinus stenting is a valuable technique for treating complicated frontal sinus disease; however the need for stenting should be carefully considered. Placement of stents can create additional trauma and promote iatrogenic scarring. Stents can also harbor biofilms and promote inflammation leading to granulation tissue, neo-osteogenesis, and restenosis. Accidental aspiration is an additional risk. Thus, the procedure is indicated in limited situations. In patients who have failed aggressive medical management, conservative surgery, multiple surgeries, or are at high risk for restenosis of the neo-ostium or obstruction of frontal sinus outflow, stenting may be an option. Stenting of the frontal sinus should be used by experienced surgeons with a clear understanding of frontal recess anatomy and chronic rhinosinusitis pathophysiology.