Indications

The endoscopic approach is particularly suitable to avoid excessive dissection within the orbit, including situations in which the MR is rotated posteriorly as well as in cases of lost or displaced MR. A team approach with the ophthalmologist is essential for comprehensive management of the patient. Further strabismus procedures are often required for optimal patient outcome.

Technique

Access to the orbit begins with a standard endoscopic anterior and posterior ethmoidectomy, which provides access along the entire lamina papyracea. The lamina is subsequently removed, as for an orbital decompression, exposing the periorbita. Under endoscopic guidance, the periorbita is incised with a crescent knife in the posterior orbit, which exposes the orbital fat (Figure 1).

Dissection of the fat can be accomplished with a blunt probe and bipolar diathermy. The MR is more easily identified posteriorly due to the bulkier posterior segment of the

MR. Once identified, the muscle can be followed anteriorly and dissected circumferentially to expose the entire MR.

In cases of muscle retrieval of an intact but posteriorly rotated MR, a 6-0 Vicryl suture should be placed into the anterior muscle belly (Figure 2). This is followed by transection of the muscle just anterior to the point of attachment of the suture (Figure 3). The use of bipolar diathermy to cauterize the intended transection line helps reduce bleeding which can impair endoscopic vision. A hook should be used to keep the muscle under tension to facilitate these maneuvers. In the case of muscle hypertrophy secondary to thyroid disease, the muscle can be considerably hypertrophied. It must nevertheless be completely identified and all muscle fibers transected for the procedure to be effective.

The suture previously attached to the distal segment of the MR, is subsequently passed under endoscopic vision to the ophthalmologist for reattachment to the globe (Figure 4). The ophthalmologist approaches via an anterior, subconjunctival route to grasp the suture for subsequent reattachment to the globe. In cases of strabismus, this route would usually be at a point on the globe posterior to the original insertion site (Figure 5). This step frees the severe MR

traction on the globe, thus allowing access for further strabismus procedures.

To minimize the risk of formation of postoperative adhesions secondary to the inflammation present in thyroid diseaseassociated ophthalmopathy or after previous surgical trauma, a course of postoperative oral corticosteroids is complemented by the placement of a MeroGel sinus dressing (MedtronicXomed, Jacksonville, FL) impregnated with corticosteroids in the ethmoid cavity at the end of the surgery.

In cases of lost or displaced MR, the focus of the endoscopic approach would be to identify the muscle, assess damage to the MR and to free the muscle from any entrapment or adhesions. Again, this is more easily done starting from the posterior aspect of the muscle. Further definitive treatment depends on the individual operative findings. In cases of trauma, reattachment of the muscle may be attempted but is often unsuccessful due to partial resection of the muscle during trauma or severe postoperative fibrosis secondary to delayed presentation.

Discussion

The natural proximity of the MR muscle to the ethmoid cavity makes the transnasal endoscopic approach feasible. This tech-

nique is relatively less invasive and provides an additional option to ocular muscle surgery. It becomes particularly valuable when the traditional open route is unable to provide sufficient access and exposure. This could happen in cases of Grave’s orbitopathy, which can result in severe adduction of the eye, rendering the patient functionally blind. The critical step in the management is to disinsert and recess the tight MR, thus allowing the globe to abduct freely. This would facilitate access to the rest of the ocular muscles.

The technique begins with a standard orbital decompression with incision of the periorbita. This step is easily accomplished but care should be taken with the incision as the MR is in very close proximity with the periorbita. As the incision is made, the orbital fat tends to prolapsed into the field of vision and should therefore be performed in a posterior to anterior direction. The use of bipolar diathermy helps to shrink the fat and improve visibility. Identification of the MR adjacent to the posterior ethmoid is a constant feature. It is near the lamina and easily identified. The optic nerve and ophthalmic artery are in close proximity but these remain deep to the MR, which protects them from trauma during the incision and dissection.

In patients with a contracted MR, suture attachment and complete transaction is needed to free the muscle. Once

free, the ophthalmologist can easily grasp the suture under endoscopic vision, and together with its attached muscle, draw it anteriorly for reattachment at the desired location. Further strabismus surgery can subsequently proceed once the MR is freed and repositioned.

The use of powered instruments in ESS has resulted in an increased incidence of severe ocular muscle injuries.10 The natural proximity of the MR in this case makes it the most vulnerable to injury. In the unfortunate scenario of ESS orbital injury, it is imperative that early evaluation and exploration of the extraocular muscles be done before the development of fibrosis and scarring to improve the functional outcome.11 Endoscopic exploration has low morbidity and should be considered when there is any doubt about the status of the MR. There is less dissection compared with the open approach, hence less risk of fat adherence syndrome.

Conclusion

The endoscopic approach to the orbit provides an alternative approach to the challenging problem of lost muscle retrieval and can retrieve displaced, lost or transacted muscles that were previously irretrievable using conventional, open surgery. Further cooperation with our ophthalmology colleagues would guide the expanding possibilities of transnasal endoscopic ocular muscle surgery.

References

1.Kennedy DW, Zinreich SJ, Rosenbaum AE, et al: Functional endoscopic sinus surgery. Theory and diagnostic evaluation. Arch Otolaryngol 111:576-582, 1985

2.Kassam A, Snyderman CH, Mintz A, et al: Expanded endonasal approach: The rostrocaudal axis. Part I. Crista galli to the sella turcica. Neurosurg Focus 19:E3 (review)

3.Wormald PJ, Ooi EM, Van Hasselt CS, et al: Endoscopic removal of sinonasal inverted papilloma including endoscopic medial maxillectomy. Laryngoscope 113:867-873, 2003

4.Metson R, Pletcher SD: Endoscopic orbital and optic nerve decompression. Otolaryngol Clin North Am 39:551-561, 2006

5.Plager DA, Parks MM: Recognition and repair of the “lost” rectus muscle. A report of 25 cases. Ophthalmology 97:131-136, 1990; discussion 136-137

6.McKeown CA, Metson RB, Dunya IM, et al: Transnasal endoscopic approach to expose the medial rectus from the annulus of Zinn to the penetration of Tenon’s capsule. J Pediatr Ophthalmol Strabismus 33: 225-229, 1996

7.Srivastava SK, Reichman OS, Lambert SR: The use of an image guidance system in retrieving lost medial rectus muscles. J AAPOS 6:309-314, 2002

8.Lenart TD, Reichman OS, McMahon SJ, et al: Retrieval of lost medial rectus muscles with a combined ophthalmologic and otolaryngologic surgical approach. Am J Ophthalmol 130:645-652, 2000

9.Flanders M, Hwang SY, Al-Ghamdi S, et al: Endoscopically assisted strabismus surgery. Am J Rhinol 21:297-301, 2007

10.Graham SM, Nerad JA: Orbital complications in endoscopic sinus surgery using powered instrumentation. Laryngoscope 113:874-878, 2003

11.Huang CM, Meyer DR, Patrinely JR, et al: Medial rectus muscle injuries associated with functional endoscopic sinus surgery: characterization and management. Ophthal Plast Reconstr Surg 19:25-37, 2003

KEYWORDS

Orbital fracture; Trauma; Endoscopic; Facial trauma

A variety of surgical approaches to orbital floor fractures have been described. These approaches include the subciliary, transconjunctival, transmaxillary, endonasal, and, recently, the endoscopic transmaxillary approach. As in other surgical specialties, technological advances continue to be used for the betterment of patients with facial trauma. The treatment of orbital fractures has benefited from these advances, particularly in the endoscopic arena. Currently, most orbital floor fractures are repaired with either a transcutaneous or transconjunctival eyelid approach. The use of endoscopy can easily be added to these approaches to enhance the surgeon’s visualization, particularly deep in the orbital cavity. Endoscopy also can be used in a minimally invasive, transmaxillary approach to the orbital floor that eliminates complications associated with eyelid incisions (ie external scarring, eyelid edema, ectropion, entropion, and granuloma formation). In this article, we review the technique for transmaxillary, endoscopic repair of orbital blow-out fractures.

© 2008 Elsevier Inc. All rights reserved.

A variety of surgical approaches to orbital floor fractures have been described. These approaches include the subciliary,1 transconjunctival,2 transmaxillary,3 endonasal,4 and, recently, the endoscopic transmaxillary approach.5,6 As in other surgical specialties, technological advances continue to be used for the betterment of patients with facial trauma. The treatment of orbital fractures has benefited from these advances, particularly in the endoscopic arena. Currently, most orbital floor fractures are repaired with either a transcutaneous or transconjunctival eyelid approach. The use of endoscopy can easily be added to these approaches to enhance the surgeon’s visualization, particularly deep in the orbital cavity. Endoscopy also can be used in a minimally invasive, transmaxillary approach to the orbital floor that eliminates complications associated with eyelid incisions (ie, external scarring, eyelid edema, ectropion, entropion, and granuloma formation).7 In this article, we review the technique for transmaxillary, endoscopic repair of orbital blow-out fractures.

Address reprint requests and correspondence: E. Bradley Strong, MD, Department of Otolaryngology, University of California, Davis School of Medicine, 2521 Stockton Blvd., Ste 7200, Sacramento, CA 95817.

E-mail address: edward.strong@ucdmc.ucdavis.edu.

Surgical anatomy

The orbital floor is divided into medial and lateral segments by the infraorbital nerve. The medial segment is larger and more fragile, whereas the lateral segment is smaller, thicker, and stronger than the medial segment (Figure 1). This anatomic division of the orbital floor results in repeatable fracture patterns. Fractures can be endoscopically classified into 3 types8: (1) trap door, (2) medial blow-out, and (3) lateral blow-out. Trap door fractures occur when a large fragment of the medial orbital floor is displaced inferiorly, but remain “hinged” at the laminar bar (Figure 2A). Medial blow-out fractures result in bone disruption between the laminar bar and the infraorbital nerve (Figure 2B). Lateral blow-out fractures result in bone comminution from the laminar bar to the lateral orbital wall (Figure 2C).

Indications for surgery

The indications for endoscopic repair are identical to traditional repair. They include (1) isolated orbital floor injuries with extraocular muscle entrapment, (2) preoperative enophthalmos, or (3) significant disruption of the orbital floor ( 50%). There is, however, one absolute