A New Drill for Frontal Sinus Surgery

The advent of endoscopic sinus surgery revolutionized the diagnosis and management of sinus disease. As rhinologists mastered the new techniques, they also became more adventurous. However, they continued to avoid the frontal recess and ostium for many reasons, the main one being lack of suitable instrumentation. Now that endoscopists have become familiar with this area and instruments are available, the frontal sinus ostia is no longer avoided. Inexperienced manipulation in this area may produce further scarring and stenosis with subsequent persistent frontal sinusitis. This report describes a dental drill that has been modified to overcome this problem by allowing endoscopic enlargement of iatrogenically stenosed frontal sinus ostium. The anatomy of the frontal recess and frontal sinus ostium is very complex and has been accurately described by Messerklinger1 and Stammberger and Hawke.2 The medial wall of the frontal recess is made up of the most anterior and superior attachment of the middle turbinate to the skull base. This area must not be manipulated or drilled because of possible damage to the dura. The lateral wall is formed by the lamina papyracea. Posteriorly, the anterior lamella of the ethmoid bulla is found below, and the suprabullar recess above. The frontal sinus ostium is located in the floor of the frontal sinus. The anterior ethmoidal artery and nerve (which usually run in a bony canal) are located in the posterior wall. The nasal process of the frontal bone forms the medial, anterior, and lateral walls. In the past, when stenosis of the frontal duct and recess had occurred either from disease or iatrogenically, the only recourse was some type of external approach. Today a modified Lathrop procedure as described by Draf3 is the choice of most endoscopists. This procedure requires the removal of part of the roof of the nasal septum and extensive removal of the floor of the frontal sinus. The advantage of the modified dental drill is that it can be used to circumferentially enlarge a stenosed and scarred frontal sinus recess and ostium, thereby creating a more anatomically natural frontal sinus outflow tract. The frontal sinus ostium, frontal recess, and frontal sinus infundibulum are angled between 100° and 134° to the horizontal plane.4 If one were attempting to enlarge the frontal sinus ostium in a circumferential direction, a conventional drill would be unsuitable. Similarly, the removal of the nasal process of the frontal bone that forms the anterior wall of the frontal sinus ostium is easier if the cutting can be performed from behind, rather than at a tangent. The only drill small enough to be able to be inserted into the nose and still permit endoscopic visualization of the cutting head is a dental drill, but the shaft of the conventional dental drill is too short. To overcome this problem, the author modified a dental drill. The shaft of a contra-angled dental handpiece has been lengthened to 100 mm (KaVo Werk Dentale Einrichtungen, Warthausen, Germany). It uses a pediatric dental head (52G E229587), which accepts the latch type of dental burrs. This fits into a surgical shank (No. 3624) (reduction, 1:4), producing a working speed of 2000 to 5000 rpm. An irrigation channel is attached, to provide a flow of saline solution that cools the burr and keeps it free of bone dust (Fig. 1). The drill bits are the standard latch type of dental burrs, 21 or 26 mm long. They are available with cutting or diamond heads, in a variety of sizes (Brasseler USA, Savannah, GA). Modified contra-angle dental handpiece. The shaft of the handpiece has been lengthened to 10 cm. A small pediatric dental head is used that accepts the latch type of dental burrs. A saline irrigation channel prevents bone dust from clogging the cutting surfaces of the drill bits. The power source (KaVo Intrasept surgical unit No. 905) is a mobile unit that delivers variable speeds and torque to the handpiece (Fig. 2). The operator controls the speed by means of a foot-operated switch. Sterile saline irrigation is also delivered by the power source, and the rate of flow can be adjusted to suit the operator and the requirement of the surgical field. The console provides electrical power to drive the dental handpiece, and contains the pump for saline irrigation. It enables the surgeon to set the speed and torque of the motor, as well as the amount of saline flow. A foot control allows variable speed selection, overriding the console settings. The surgery is performed in an operating room with the patient under general anesthesia and lying on a special radiolucent operating table. Fluoroscopic equipment is positioned before the beginning of surgery and after the patient is anesthetized. The fluoroscopic image is compared with the reconstructed computed tomography scan. The operative field is infiltrated with local anesthetic solution containing epinephrine. The endoscopic surgery is performed using a television monitor. The frontal sinus ostium is located using a curved suction tip as a probe. Its position is checked by fluoroscopy. Both anteroposterior and lateral views are obtained to ensure correct positioning and to facilitate safe surgical manipulation. The modified dental drill with a tapered diamond drill bit is next introduced into the nasal passage. The 30° angled, 4-mm endoscope is inserted above the shaft of the handpiece, and under visual control the tip of the drill is introduced into the frontal sinus ostium. The position of the drill is once more confirmed by fluoroscopy. The enlargement of the ostium commences by first drilling in an anterior direction. Drilling should never extend posteriorly, as this is where the anterior ethmoid artery is located. It is also dangerous to initially drill in a medial direction because the cribriform plate can extend quite far forward. It is possible to drill laterally, but damage to the lamina papyracea and the orbital periosteum5 must be avoided. The new ostium should be as large as possible to reduced the likelihood of repeat stenosis. Hosemann et al.6 found that a neo-ostium with a diameter exceeding 5 mm was more likely to stay open than one with a smaller diameter. It is very important to suction the new opening at least once a week for the first month so that blood clots and debris can be removed. The patient is also encouraged to perform saline irrigation until the ostium mucosa has healed. The author has used this approach to correct iatrogenically stenosed frontal sinus ostia in three cases. The first one closed in 1 year because only a 2-mm opening was created. The subsequent two cases have remained open for 2 years. Hosemann has used this drill for the past 18 months. His experience with the drill has been similar to the author's (W. Hosemann, personal communication, July 1998). The modified dental drill is a new tool in the armamentarium of the rhinologist treating iatrogenically created frontal sinus recess and ostium stenosis. It allows endoscopic enlargement of the frontal sinus ostium so that a more “anatomically correct” reconstruction is possible without having to perform either an external approach or extensive resection of the floor of the frontal sinus.

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