Endoscopic Orbital Fracture Repair

Endoscopic Repair of a Medial Orbital Wall Facture With the “Milan Technique”

Endoscopic Medial Orbital Wall Reconstruction After Removal of an Orbital Mass Via a Transnasal Approach

Medial Orbital Wall Fractures

The medial orbital wall, as the locus minoris resistentiae, is the second most frequently injured orbital boundary after blunt trauma. As covered further in the chapter, medial orbital wall fractures can also present concomitant orbital floor fractures in a more complex scenario.

Two different etiopathogenic theories have been suggested as an explanation for medial orbital blow-out fractures: the hydraulic theory and the buckling theory. According to the first paradigm, intraorbital pressure becomes elevated owing to retropulsion of the orbit; such elevated pressure leads to fracturing the medial orbital wall in the point of lowest resistance. The latter paradigm links medial orbital wall breaches to a direct trauma involving the medial orbital rim. Independent of the physiopathogenic mechanism, any blunt trauma involving the eyeball and/or the medial orbital rim can lead to a fracture of the lamina papyracea, causing herniation of the medial orbital content into the nasal cavity. This means that not only the fatty orbital content, but also the muscles can enter the nasal cavity with a nonnegligible chance of muscular entrapment; again, enophthalmos and/or diplopia may follow.

From an anatomic standpoint, it is worth remembering that the medial orbital wall is formed not only by the lamina papyracea (which almost inevitably is fractured), but also by the lacrimal bone anteriorly, the maxillary bone inferiorly, and the lesser wing of the sphenoid posteriorly. A suture runs at the border between the ethmoid and the frontal bone, in close proximity to the anterior and posterior ethmoidal arteries. This suture represents the closest point to the dura and thus should be approached with the utmost attention to avoid cerebrospinal fluid leaks. Ethmoidal arteries can allow for an average estimate of the anteroposterior orbital depth, given that the anterior ethmoidal artery runs 24 mm from the lacrimal crest, whereas the posterior ethmoidal artery lies 12 mm posterior to this and the orbital apex 6 mm further posteriorly.

As mentioned earlier, both fat and muscle (more specifically, the medial rectus muscle) can herniate toward the nasal cavity; therefore, indications for medial orbital wall repair are diplopia and significant enophthalmos. Although evaluating gaze in all position is always recommended because the medial rectus muscle is usually affected, the horizontal gaze should be given the maximum attention during evaluation to identify the slightest restrictions. Although clinically relevant enophthalmos, as well as diplopia, are generally appreciable with a careful clinical examination, a CT scan is mandatory to provide information on the fracture site, the number of fragments, and anatomic relationships. This is especially relevant if a pure transnasal endoscopic access is planned, which must rely on the usual landmarks of endoscopic sinus surgery to avoid damage to noble structures. Furthermore, the CT scan provides information on the size of the fracture, allowing for proper planning. Mirrored CT images coupled with neuronavigation enable also more precise orbital reconstructions.

Medial wall fractures have been approached historically in countless ways. The first reliable proposal was the Lynch incision, ultimately abandoned because of poor overall aesthetic results. Currently the approaches to medial wall usually rely on transconjunctival accesses, including the transcaruncular, precaruncular, and retrocaruncular routes. All these accesses usually couple swift direct access to the fracture site with an acceptable surgical field. Nevertheless, these approaches are hampered by very limited visibility of the posterior and superior areas of the medial wall and by potential injuries to the lacrimal sac and to the lower oblique muscle. The need for eyeball manipulation is another disadvantage, though minor, in these approaches. To overcome these disadvantages, many authors have relied on endoscopy, which has been used as an aid to traditional approaches or in completely new ways through the transnasal route.

Many recently introduced techniques saw a tight collaboration among ophthalmologists, maxillofacial surgeons, and otolaryngologists. Most of these techniques have been developed to address both tumors and orbital fractures, with a specific focus on the posteriormost areas—the orbital apex and the periorbital skull base—which are the areas least easily exposed through external approaches. Excellent case series have been published (e.g., Murchison et al. ). In this series a multidisciplinary team (neurosurgeon, otolaryngologist, and orbital surgeon) performed ethmoidectomy, sphenoidotomy, and posterior lamina papyracea removal to enter the orbit in 18 patients with a range of pathologies including cavernous hemangiomas, juvenile angiofibromas, and invasive cutaneous squamous cell carcinoma. Approaching these lesions somehow led the way to approaching with a higher degree of safety, smaller, localized lesions, such as medial wall fractures. In these regards, it may be worth noting that in these case series, complications were relatively common (22% of the patients) and included decreased postoperative visual acuity and cerebrospinal fluid leak. Although the extent of exposition for approaching medial wall fractures is considerably more limited, the orbital surgeon should never forget that the orbit should always be regarded as a high-risk location.

Other interesting case series on endoscopic approaches were published by Chhabra et al. and Bleier et al. These two articles report a detailed experience in treating orbital venous malformations (commonly misnamed as cavernous hemangiomas ), a condition that frequently requires extensive dissection, removal of the papyracea, and extrinsic orbital muscle dissection. The experience with these patients not only strengthened the anatomic knowledge of the medial orbital wall from an endoscopic perspective but also added information on an important feature common to medial orbital wall—that is, the enophthalmos caused by the herniation of orbital content toward the nasal cavity. Although modern views on these techniques state that minimally invasive accesses do not tend to induce enophthalmos, the same approach we describe in detail for medial orbital wall fractures could be adopted to reconstruct the medial orbital wall after endoscopic orbital mass removal.

Restricting once again the focus on endoscopic reconstruction of medial orbital wall fractures, it is worth noting that the transnasal-transethmoidal and transcaruncular approaches and conjunctival incisions are the most commonly used approaches and both grant the avoidance skin incisions and optimization of cosmesis. Among the first notable case series was the one from Hinohira et al., who performed a transnasal endoscopic medial wall reconstruction on 23 patients with isolated medial blowout fractures with a 95.5% success rate. When using the transnasal approach, nevertheless, most authors usually rely on supporting the medial wall with a silicone sheet and/or using additional long-term nasal packing to contain the herniated orbital content, with obvious patient discomfort and a theoretical increased risk of infection. Conversely, the use of other materials such as high-density porous polyethylene with an endoscopic transcaruncular approach (which means an external approach aided by the endoscope, not a pure endoscopic approach) showed excellent results with minimal discomfort.