The frontal sinus is commonly affected by inflammatory diseases, traumatic fractures, benign tumors, and malignant neoplasms. Because of its proximity to the brain, eye, and nose, disease processes originating from these anatomic sites can extend to involve the frontal sinuses. Transnasal endoscopic surgery is presently the principal approach for managing frontal sinus pathologies, with open external approaches mostly limited to the repair of frontal sinus fractures. The trend away from classic external frontal sinus approaches to contemporary endonasal techniques exploded over the past two decades with the introduction of specialized instruments, the development of high-powered endoscopes, and image-guided surgical navigation systems. A major limitation of transnasal endoscopic frontal sinus surgery is access to the lateral and most anterior aspects of the frontal sinus. Access to the lateral and anterior sections of the frontal sinus is feasible through expanded transnasal techniques, such as the Draf procedures, but the working angles are somewhat less favorable and disruption of healthy paranasal sinus system is often necessary. Nonetheless, the anterior and lateral segments of the frontal sinus are easily accessible through the classic bicoronal cranial exposure with osteoplastic bone flaps. However, the bicoronal approach involves a broad field surgery far beyond the outlines of the frontal sinus. An approach to the frontal sinus that allows access to all aspects of the frontal sinus that combines the minimally invasive advantages endoscopic and the exposure of open access surgery is desirable.
Transorbital approaches to frontal sinus diseases offer an alternative to pure endonasal approaches, combining the desirable aspects of classic external approaches and the more contemporary endonasal approaches. Because the thin superior and medial walls of the orbit are intimately associated with the frontal sinus, osteotomy windows in the fronto-orbital complex offer a direct surgical corridor to frontal sinus pathologies. Lim et al. and Boahene et al. have contributed extensively to the popularity of transorbital anterior skull base approaches with a series of publications over the past decade.
There are four main technical aspects to transorbital frontal sinus surgery: soft-tissue exposure of the fronto-orbital bone complex, creation of a mini-orbitofrontal bone window, management of the targeted pathology, and reconstruction. These four technical components are performed in a minimally invasive manner over short working distances with bimanual dissection in a coplanar fashion augmented or enhanced with endoscopes or surgical microscopes.
Soft-Tissue Exposure of the Frontoorbital Bone Complex
Exposure of the orbitofrontal bone complex for the transorbital approach is through an upper eyelid supratarsal crease or conjunctival incision. The access incision—supratarsal versus conjunctival—is selected depending on the targeted subsite of the frontal sinus.
The supratarsal crease incision is the workhorse approach through which the entire fronto-orbital bar can be exposed ( Fig. 31.1 ). The supratarsal crease is a distinct skin fold above the upper eyelid margin that results from insertion of the levator aponeurosis into the eyelid skin. Incisions placed in this crease are routinely used for upper eyelid blepharoplasty and camouflage well. An extension of the incision into a lateral orbital wrinkle expands the soft-tissue exposure and heals acceptably well provided the scar does not extend past the bony orbital rim.
The supratarsal crease should be outlined preoperatively with the patient sitting upright. The incision extends from the inner canthal region to the lateral canthal area following the natural upper eyelid crease. At least 3 mm of skin is left intact over the medial canthus to prevent webbing. The lateral extension of the incision is planned in a natural wrinkle line. When appropriately planned, the marked line should not be visible when the eyelids are open (see Fig. 31.1 ).
To protect the cornea, a temporary Frost suture or cornea shield is placed. The forehead and upper eyelid are infiltrated with local anesthetic with vasoconstrictive agents. The infiltration also hydrodissects the tissue planes to facilitate dissection. The incision is carried through the skin and orbicularis oculi muscle. The orbital septum deep to the orbicularis oculi muscle is kept intact, preventing fat herniation. Dissection is carried over the orbital septum to the superior orbital rim. The periosteum along the superior orbital rim is sharply incised and released along the superior and lateral orbital rim. Subperiosteal dissection is widely performed to expose the entire anterior frontal sinus wall and the superior orbital rim (see Fig. 31.1 ). Releasing the periosteal attachments at the temporal line broadens the exposure. The supraorbital neurovascular bundle should be carefully released from its foramen or notch and protected. An orbitofrontal minicraniotomy can now be performed to provide access to the frontal sinus. To protect the eyelid skin, pledgets are placed along the skin edge as a protective cushion when retracting.
The orbital walls can also be accessed via conjunctival incisions. The transconjunctival approach may be used to expose all quadrants of the orbit. A precaruncular medial conjunctival incision with extensions into the upper and lower eyelids is ideal for exposing lesions along the medial aspects of the frontal sinus floor ( Fig. 31.2 ). The upper and lower lacrimal puncta are identified and preserved. They can be cannulated to prevent inadvertent injury. The conjunctiva behind the caruncle is infiltrated with local anesthetic. A precaruncular conjunctival incision down to bone is made with a guarded needle-tip cautery. Through this access the periorbital along the medial and superior orbital wall is elevated as extensively as needed. The anterior and posterior ethmoid arteries become visible, bridging the gap between the periorbital and orbital bone at the level of the cribiform plate. They should be ligated and divided to provide more working space. The ethmoid arteries are important landmarks in this surgical approach, as they mark a level above which intracranial access can then be gained after removal of a thin orbital bone. The working surgical cavity is maintained by gentle distraction with a malleable retractor, which can be held in place with a clamp holder.
Orbitofrontal Bone Window
A computed tomography–guided image mapping of the outline of the frontal sinus is essential in planning and opening an optimal orbitofrontal bone window. The bone window can be variably positioned based on the location of the target pathology to provide the most direct exposure for instrumentation (see Fig. 31.1 ). To access the frontal sinus recess, intersinus septum, and contralateral sinus, the bone window should be positioned close to the frontonasal suture line. A laterally centered bone window is necessary for exposing the lateral frontal sinus recesses. The planned ostectomy may be limited only to the anterior frontal sinus wall and superior orbital ridge or extended to include the orbital roof and frontal sinus floor depending on the targeted pathology. Once the planned osteotomy is designed, the osteotomy site may be preplated to facilitate an anatomic reconstruction after the procedure. Low-profile 1.0 titanium plates are adequate. The minicraniotomy is then performed using an oscillating saw or ultrasonic bone scalpel and osteotomes. Beveling the bone cuts inward allows the bone flap to be replaced on a supported lip at the end of the case. A 1.5- to 2.5-cm orbitocranial window is usually adequate for direct visualization and bimanual instrumentation. Illumination and a detailed view of the frontal sinus are greatly enhanced by endoscopic magnification.
Management of Selected Targeted Disease
Inverting papilloma is a rare, benign, sinonasal tumor that is locally aggressive and has a tendency to recur. Complete resection is critical because up to 9% of inverting papillomas can progress to squamous cell carcinoma. Complete resection of the tumor and adjoining predisposed mucosa after fully outlining the disease extent within the frontal sinus decreases the likelihood of recurrence.
A trabsorbital approach through a supratarsal crease incision is a versatile approach for thorough resection of inverting papilloma with extensive involvement of the frontal sinus ( Fig. 31.3 ). The transorbital approach is combined with a transnasal endoscopic approach to comprehensively address disease in the nose and sinuses.