------------------------------------------------------------------------------- TITLE: Orbital Blowout Fractures SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: October 11, 1995 RESIDENT PHYSICIAN: John Yoo, M.D. FACULTY: Brian Driscoll, M.D. SERIES EDITOR: Francis B. Quinn, Jr., M.D. ------------------------------------------------------------------------------- "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." Blow-out Fractures: Anatomy The orbits are housed in cavities shaped like four-sided pyramids with their bases directed anteriorly.1 The tip of the pyramid corresponds to the orbital apex which contains the superior orbital fissure and the optic foramen. Seven bones make up the orbits and include the sphenoid, maxillary, lacrimal, ethmoid, frontal, zygomatic, and palatine bones. The roof of the orbit is made up of the orbital surface of the frontal bone with a minor contribution from the lesser wing of the sphenoid bone posteriorly. The lateral wall is formed by the zygomatic bone and the greater wing of the sphenoid. This wall is separated from the floor by the inferior orbital fissure(IOF) and from the roof by the superior orbital fissure(SOF). The floor is composed of the zygomatic, maxillary, and palatine bones. The medial wall is made up of the ethmoid, frontal, lacrimal, and sphenoid bones.1 Anatomically, the orbits are intimately associated with the paranasal sinuses: the sphenoid sinus posteromedially, the ethmoids medially, the frontal sinus superomedially, and the maxillary sinuses inferiorly.1 Pathophysiology Blow-out fractures of the orbital wall(s) are believed to be due to posterior displacement forces on the globe by blunt trauma with transmission of those forces to the thin orbital walls, or blunt trauma to the inferior orbital rim without forces transmitted directly to the globe.2 Blow-out fractures usually involve the orbital floor, but may involve (in descending order) the medial, lateral, and superior orbital walls.3 Blow-out fractures can be classified into pure fractures which are displaced bone fragments in the central part of an orbital wall and impure fractures which have the displaced bone fragments extending to involve an orbital rim.3 The soft tissue and fat of the orbit are able to herniate through the defect left by the blow-out fracture. In smaller defects, extraocular muscles may become entrapped causing diplopia. However, diplopia may also arise from the entrapment of fibrous septae contained within the orbital fat that help support the position and function of the extraocular muscles. As the size of the defect increases, so does the enophthalmos and displacement of the globe. In large defects, movements of the globe are unhindered, but the change in globe position brought on by the large defect affects the function of the extraocular muscles causing diplopia.3 Evaluation Following a thorough history including the details of the injury and any ophthalmic history predating the injury, a physical examination should be performed as quickly as possible. The exam should include evaluation of edema, ecchymosis, craniofacial bony abnormalities, visual acuity, range of extraocular movements, disconjugate gaze and diplopia, pupil size and reactivity to light, presence of subconjunctival hemorrhage, orbital rim step-off's. Exam of the lens, cornea, anterior chamber, and retina should be carried out to search for injuries of the globe such as corneal abrasion/laceration, hyphema, globe rupture. The patient should be examined for anesthesia/hypesthesia of the infraorbital nerve distribution. Diplopia may be due to entrapment of extraocular muscles (usually the inferior rectus) or fascia, injury to the extraocular muscles, hemorrhage in the extraocular muscles or orbit, or nerve damage. Forced duction test should be performed to confirm entrapment of the inferior rectus muscle. Degree of enophthalmos should be assessed by measuring the corneal projection from surrounding structures (lateral orbital rim) and comparing with the uninvolved eye.2,3 The best radiographic study is the CT-scan in axial and coronal planes. Immediate ophthalmologic consultation is usually warranted. Treatment The goals of treatment include preservation of binocular vision and maintenance of cosmesis by minimizing enophthalmos.2 According to Mathog, absolute indications for surgery include: 1)acute enophthalmos or hypophthalmos and 2)mechanical restriction of gaze. His relative indications include: 1)conditions that can later cause enophthalmos or hypophthalmos and persistence of diplopia. The contraindications to surgery include: 1)hyphema, retinal tears, ruptured globe; 2)injury is to the only seeing eye; and serious injury to other organ systems that make the patient unstable.3 The timing of surgery is controversial, but most authors advocate that if surgery is necessary, to wait until 7-14 days after the injury. Performing surgery too early may be associated with distorted anatomy as a result of the edema, increased bleeding due to the inflammatory phase of healing, and the traumatic injuries of the organ systems. Waiting too late will be difficult because of the scarring and fibrosis as well as the fusion of bony fragments in undesirable positions. However, if the patient requires surgery for another reason, then it is worthwhile to consider surgery before the 7-14 days.2,3 Good results may be obtainable even 4-6 weeks post-injury in experienced hands.3 Some of the incisions used for the approach to repair of inferior orbital blow-out fractures include subciliary, transconjunctival, and infra-orbital incisions. Whichever incision is chosen, the dissection should continue in a plane between the orbicularis oculi muscle and the orbital septum until the infraorbital rim is reached, where an incision is made about 5 mm below this rim. The overlying periosteum is elevated posteriorly freeing up the trapped soft tissues. For medial wall fractures, an incision is made midway between the caruncle and the nasal dorsum. the periosteum should be elevated posteriorly, with clipping of the anterior ethmoid artery if needed. Dissection should stay anterior to the posterior ethmoid artery. The bony fragments should be elevated if possible. Some defects are small enough that all that is needed is reduction of the soft tissues. Most, however, require reinforcement of the orbital wall defect with an alloplastic mesh implant. If the defect is too large, greater strength and compensation for soft tissue loss may be necessary and this is provided by a bone graft, such as from the cranium.3 ------------------------------------------------------------------------ BIBLIOGRAPHY 1. Barry M. Zide and Glenn W. Jelks. Surgical Anatomy of the Orbit. Raven Press: New York. 1985. 2. Fonseca RJ and Walker RV. Oral and maxillofacial trauma. W.B. Saunders: Philadelphia, PA. 1991. 3. Mathog, RH. Management of Blowout fractures. Otolaryngol Clin N Amer. 24(1):Feb 1991; 79-91. ------------------------------END----------------------------------------