Synechiae and ostial stenosis are common and troublesome complications following endoscopic sinus surgery. Many investigators have advocated the use of stents to minimize the risk of postoperative stenosis while others have found their use to be of no benefit. This article reviews the advantages and disadvantages of various stents used in sinus surgery, and discusses such innovations as drug-releasing stents.
The formation of synechiae is the most common complication following endoscopic sinus surgery (ESS). Early series report a rate of 7.5% to 10.5% synechiae formation, with 2.5% to 4% requiring revision surgery. Dissection of the frontal recess is the most technically challenging aspect of ESS because of the difficult angle of dissection, the complexity of the frontal recess anatomy, and its relationship to the orbit and cribiform plate. In addition, the frontal sinus is associated with the highest rate of stenosis postoperatively when compared with all other sinuses. Chandra and colleagues reported a 10% stenosis rate when frontal recess dissection was performed. Stents have long been described as an attempt to decrease the rate of synechiae and stenosis.
Stents placed following ESS have five potential functions:
The primary purpose of a stent is to separate edges of a wound surface so as to prevent synechial band formation or stenosis. For example, by not allowing the middle turbinate to make contact with the lateral nasal wall, lateralization of the middle turbinate can be prevented.
Stents also serve to take up space that would otherwise be filled with blood, with fibrin, or with mucus, which would serve as a substrate for unwanted epithelial migration.
In concordance with this, stents can decrease the time and discomfort of postoperative debridement as there is simply less clot/debris to remove.
Stents may also provide a matrix for epithelial migration, especially in areas of denuded bone, as the stent’s surface provides subepithelial scar a chance to stabilize.
Finally, stents serve as an occlusive dressing, which has a positive influence on wound healing. Occlusive dressings have been shown to decrease inflammation and necrosis early in wound healing and fibrosis and scarring late in the process.
Middle meatal stents
As detailed above, the main purposes of stents placed in the middle meatus postoperatively are to decrease synechiae, prevent middle turbinate lateralization, and to fill the ethmoid, which would otherwise be filled with blood, mucus, or fibrin. It is our practice to stent the middle meatus with a “spacer” made from a glove finger, 2-0 silk suture, and a portion of a polyvinyl acetal sponge (Mercocel, Mystic, Connecticut). The sponge is placed inside the glove finger and the two are sutured together and inserted into the middle meatus and inflated with saline. This spacer is smooth and does not adhere to the surrounding tissue, so there is no additional damage to the surrounding tissue upon removal. This technique also prevents the ethmoid from filling with crust and clot, leading to far less postoperative debridement. Finally, the spacer serves as an occlusive dressing that improves wound healing.
Foam made of biodegradable synthetic polyurethane, such as NasoPore (Stryker, Kalamazoo, Michigan), can also be used as a middle meatal stent. This material is initially firm, keeps mucosal surfaces separated, and takes up space in the ethmoid. The material has a hydrophilic component and exposure to water leads to rapid fragmentation of greater than 90% after 5 days. This material can be suitable for patients who cannot tolerate other types of middle meatal stents. However, it is the authors’ experience that the material rarely has degraded by 1 week postoperatively. There is also evidence that mucosal healing is initially delayed when compared with a finger-cot stent, but healing appears equal by 3 months postoperatively.
Other middle meatal stents have been described. Shikani detailed a silicone stent with two flanges—one triangular, separating the middle turbinate from the lateral nasal wall, and one smaller, securing the stent in the maxillary sinus. The stent was left in place for 10 to 14 days and results of 50 sides were compared with 50 controls. After a mean follow-up of 8.2 months, patency rate of the stent side was 100% compared with 70% on the control side. This same study design was repeated in a pediatric population, resulting in 10% adhesion formation on the stent side and 55% adhesions on the control side.
Frontal sinus stents
The practice of stenting of the frontal sinus has generated debate about several related issues, including type of material, duration, and the basic need for stenting. Outcomes are difficult to evaluate and to compare because of the inherent difficulty of providing for an adequate control. Also, reports have been based on only a few patients, which indicates stenting is generally reserved for a small number of patients.
The first frontal sinus stents were rigid tubes made of various materials. In 1976, Neel and colleagues used a canine model to demonstrate that a thin Silastic (pliable silicone) sheet resulted in less fibrosis, less osteoblastic activity, and more normal mucosal lining when compared with the previously used rigid rubber stents. Numerous prefabricated frontal sinus stents have since been described using silicone. Two examples are the Freeman (InHealth Technologies, Carpinteria, California) and Rains frontal sinus stents (Smith & Nephew ENT, Memphis, Tennessee). The Freeman stent is a biflanged tube and is available in two sizes (14F catheter and 16F catheter). This stent can be inserted via an external incision or endoscopically with an insertion device and a dissolving gel cap for the distal flange. In Freeman’s initial report, 6 of 46 patients (13%) failed stenting with restenosis of the frontal sinus after a mean follow-up of 29 months. The Rains frontal sinus stent has a collapsible tapered bulb tip and is available in 4-mm and 6-mm outer diameter sizes. This stent can also be placed endoscopically with a curved suction. In Rains’s initial report with a maximum follow-up of 46 months and mean stent duration of 35 days, there was a 94% patency rate. The downside of the prefabricated stents is that they are rigid and cannot adapt to varying ostial diameters ( Fig. 1 ). Although reported as flexible, they are much more rigid than traditional Silastic sheeting.
Stents can also be fashioned out of Silastic tubing or sheeting. In our practice, we fabricate stents out of Silastic sheeting varying from 0.01 to 0.04 in thick. The thin sheeting is generally used in three situations:
Tubed in a unilateral frontal sinusotomy when greater than 40% of the mucosa has been denuded
To line a frontal sinus in which a large segment of the mucosa has been disturbed (eg, following tumor removal)
Following a frontal sinus unobliteration
The stents can also be used to aid in frontal recess and ostium debridement. When a Silastic stent is placed in the frontal sinus for 1 week and removed at the first debridement, cleaning of the frontal recess and ostium without traumatizing the mucosa is greatly simplified. In these situations, the Silastic conforms to ostium/sinus shape and serves as a matrix or scaffold for mucosal regrowth. Fig. 2 depicts thin silicone sheeting cut to size for insertion into the frontal sinus. Fig. 3 demonstrates a 0.01-in thick frontal sinus stent in place 3 months postoperatively and the same frontal sinus 5 months postoperatively in a patient who had severe refractory disease.
The thicker sheeting (0.04 in) can be used to form a U-shaped stent that extends up into the frontal opening as it sits on top of the septum following a Draf III procedure ( Fig. 4 ). The Silastic sheeting has numerous advantages as a stenting material. First, it is pliable and easily conforms to the shape of the frontal ostium or frontal sinus. The internal frontal ostium is not a universal shape or size, and therefore a universal stent rarely is a perfect fit. The pliable nature of the material also prevents undue pressure on the sinus mucosa. Finally, the Silastic material may act as an occlusive dressing, which, as previously mentioned, improves tissue healing.
As the duration of stenting increases, more time is allowed for the wound to stabilize and for the mucosal surfaces to remain separated. On the other hand, complications have more potential to occur the longer the stent is left in place (see below). Weber and colleagues, in their excellent review on packing and stents, advocate for a duration of 6 months rather than a particular material. Orlandi and Knight demonstrate that long-term stenting is well tolerated. In their study, nine patients had a mean stenting time of 31.6 months. Orlandi and Knight advocate that stents remain in place until there is an indication for removal (infection or pain). Electron microscopy has demonstrated that, when mucosa is only partially removed, ciliated cells regenerate fully by 6 months following surgery. However, if the mucosa is completely removed, the mucosal regeneration is significantly altered. With complete mucosal disruption, edematous proliferation of granulation occurs, which ultimately results in scar formation. Epithelium then forms after a period of 6 months to 1 year and contains only scattered ciliated cells. Based on this data, one defined stenting period cannot be advocated for all patients. However, if needed, it can be safely done long term. Judgment must be based on the amount of mucosa preserved intraoperatively, and longer stenting times of up to a year are required when there has been complete mucosal disruption.
Now that the types of stents and duration of stenting has been reviewed, the larger question of when to stent, if at all, must be raised. The size of the internal frontal sinus ostium at the completion of the procedure has been the most consistent indication for a stent. Hosemann and colleagues found that a frontal sinusotomy of greater than 5 mm has a stenosis rate of 16% compared with a rate of 33% when the diameter decreases to less than 5 mm. The stenosis rate increases even more to 50% when the diameter is less than 2 mm. Therefore, a frontal ostium size of less than 5 mm should cause the surgeon to pause and consider stent placement.
Extensive mucosal disruption in the frontal sinus or frontal recess is another relative indication for stent placement. When circumferential mucosal disruption is present, most investigators would agree and advocate stent placement to keep the mucosal surfaces apart. The opposite end of the spectrum, however, may not be so clear. Dubin and Kuhn, in their report on frontal sinus osteomas, used a stent when 40% or more of the mucosa was disrupted in the frontal recess. With regards to extended frontal sinus procedures with a drill (Draf IIb or Draf III), there has often been significant mucosal disruption. Kikawada and colleagues, finding restenosis following stent removal, do not advocate stent placement. However, only 4 patients in their series of 22 had a silicone tube stent placed following a Draf IIb or Draf III procedure. One of these 4 patients (25%) had restenosis following stent removal, whereas 5 of 22 patients without stents also had restinosis (22.7%). These numbers are too small to draw any definite conclusions regarding the efficacy of stenting in extended frontal sinus surgery, nor is there a significant difference between the two groups. One study with larger numbers evaluated the use of a Silastic stent for 2 months following a Draf III procedure in 25 patients compared with 39 without. There was no statistical difference between the two groups with regard to frontal ostium patency or symptoms. Weber and colleagues report that stenting prevented stenosis in 15 of 21 (71%) sinuses in their retrospective review using Rains stents, H-shaped silicone tubes, or U-shaped silicone tubes. This study had no control group, so it is difficult to determine if surgical success can be attributed to the stents. This study also represents a complex patient group that has demonstrated refractory disease necessitating aggressive surgical intervention; therefore, a 70% patency can be considered a success.
We advocate stenting with Silastic sheeting in situations where there has been denuded bone or significant disruption of the mucous membrane. This includes any of the following situations:
Cases where greater than 40% of the mucosa in the frontal recess has been denuded
Cases following tumor resection (osteoma or inverting papilloma) where a large portion of the frontal sinus mucosa has been denuded
Cases of frontal sinus unobliteration
Cases involving advanced frontal sinus techniques (eg, Draf III)
In addition, when the frontal sinus ostium is less than 5 mm in diameter, a stent should be considered.
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