Diagnostic Workup for the Orbital Blowout Fracture Patient
In cases in which there is an isolated orbital blowout fracture (i.e., the orbital rims are intact), the leading theory for the mechanism of injury is that the eye itself has been retropulsed into the orbit by blunt force trauma and as a result the hydrostatic pressure within the orbit has increased substantially to a threshold point at which the orbital wall (usually the floor and less commonly the medial wall) “blows out” into the adjacent paranasal sinus to relieve this pressure. 3 It has been presumed that this fracture serves as a safety-valve mechanism to relieve the pressure on the eye before the eyeball itself ruptures, and indeed it is rare in practice to see an open globe injury in association with a pure orbital blowout fracture resulting from blunt trauma. Eye injuries do occur in association with approximately one-third of orbital blowout fractures and can include corneal abrasion, traumatic iritis, microhyphema and hyphema (blood in the anterior chamber of the eye), traumatic iris tears/mydriasis, commotio retinae (bruising of the retina), retinal tear or detachment, traumatic optic neuropathy, orbital hemorrhage, and orbital emphysema. 4 Soft-tissue injuries may also occur, such as a laceration of the lacrimal canaliculus of the eyelid that may occur from a lateral shear force applied to the lid during blunt trauma. If an extraocular muscle is entrapped (or even tethered by adjacent orbital tissue) within the fracture site, the oculocardiac reflex may occur, which can lead to potentially life-threatening bradycardia and even asystole. 5 Thus, all orbital trauma patients should have a full trauma assessment including evaluation for other injuries and monitoring of vital signs. Because identification of the associated ocular injuries referenced above requires specialized equipment and techniques, a full eye examination with an ophthalmologist is advisable, who should perform slit-lamp biomicroscopy and dilated fundus examination. Visual acuity can be measured one eye at a time with a vision checking card by anyone in the health care team, along with assessment of pupils (looking for direct and consensual responses as well as assessing for an afferent pupillary defect), and gross assessment of ocular motility by having the patient follow the examiner’s finger in a wide circle. Any significant dysmotility could be a clue to an underlying orbital fracture. Other signs suggesting an orbital fracture would be frank misalignment of the eye such as strabismus or hypoglobus, relative enophthalmos (although this is often masked by the associated orbital edema in the acute setting), or hypesthesia of the cheek or lip. A laceration medial to the lacrimal punctum should raise suspicion for a canalicular laceration. A periorbital laceration with fat present within the wound indicates the orbital septum and orbit proper have been violated, and one should consider the possibility of intraorbital injury (muscle, nerve, globe) or a retained intraorbital foreign body.
If the orbit is quite tense and firm such that the lids are not able to be readily opened and the globe is under obvious pressure, there is an orbital compartment syndrome. This is an emergency and requires timely release of the orbital pressure, which is usually accomplished via a lateral canthotomy and inferior cantholysis in an effort to avoid central retinal artery occlusion or optic nerve ischemia, which can be catastrophic after 60 to 90 minutes. This technique will be described later in this chapter as part of the swinging eyelid transconjunctival approach.
If the eye is deformed or soft or there is any other concern for an open globe injury, the area should be protected with a shield so that no further manipulations are applied to the globe until evaluation by an ophthalmologist.
Imaging is indicated when there is concern for an orbital fracture or foreign body as described earlier. This should be computed tomography (CT) of the facial bones/orbits with coronal and sagittal reconstructions. Plain X-ray films of the orbit are not sensitive enough to detect many orbital fractures and not detailed enough for surgical reconstruction planning. A CT scan with only axial images is an incomplete study for the purpose of evaluating orbital trauma, as it is nearly impossible to assess the orbital floor on axial view—at a minimum, a coronal reconstruction must be obtained. Soft-tissue and bone windows should both be evaluated directly by the surgeon. The soft-tissue window can show blood in the orbit, tissue edema, and the status of the globe and extraocular muscles. The bone window enables proper assessment of the thin orbital walls (particularly the floor and medial wall, which are so thin that nondisplaced fractures are often not visible on soft-tissue windows). The images must be directly viewed by the evaluating surgeon; one cannot simply rely on reading the report for the scan. It is regrettably too common an occurrence that a CT scan is read as “normal” when in fact a fracture or other abnormality exists. 6 Unfortunately, it tends to be trapdoor fractures that are under-recognized most frequently because of their nondisplaced configuration; these tend to occur in children and require urgent surgical repair. 7
10.2.1 Indications for and Timing of Surgical Repair of Orbital Blowout Fractures
Like many conditions in medicine, and in oculoplastic and orbital surgery in particular, there are few hard rules regarding orbital fracture management. One exception though is the “white-eyed” blowout fracture, or “trapdoor” fracture, most commonly seen in pediatric patients. This is a fracture in which the orbital floor (less commonly the medial orbital wall) is fractured and minimally displaced, actually springing back into near normal anatomical alignment but unfortunately entrapping soft tissue (such as orbital fat or a rectus muscle) within the fracture itself. These fractures externally appear to have minimal edema and ecchymosis, and the eye itself is often “white and quiet” 8 ( ▶ Fig. 10.1). Most striking is the severe limitation of movement of the globe—often an inability to supraduct in floor fractures, or to abduct in medial wall fractures. Some cases can be associated with the oculocardiac reflex, in which bradycardia and nausea may develop during attempted ductions. These fractures can be missed by radiologists or surgeons not familiar with this fracture pattern ( ▶ Fig. 10.2). Nonetheless, it is essential to not miss such a fracture, because treatment involves urgent (same-day) surgical treatment. Delayed treatment of a trapdoor fracture exposes the patient to the risk of permanent injury to the rectus muscle entrapped within the fracture, which can undergo contracture from ischemia and lead to permanent strabismus and muscle dysfunction that is difficult to correct.
Fig. 10.1 A “white-eyed” or “trapdoor” blowout fracture of the right orbital floor in a 12-year-old boy who was struck by a baseball. The right eye exhibits severe limitation of supraduction, but otherwise there are minimal external signs of trauma.
Fig. 10.2 A coronal reconstruction of maxillofacial CT (computed tomography), soft-tissue window. This scan was read by a radiologist as “no fracture identified.” A clue to the fracture is the soft-tissue abnormality between the right inferior rectus muscle and right orbital floor–this is the soft tissue entrapped by the trapdoor fracture and is what tethers the eye and limits supraduction.
A review article by Burnstine in 2002 collated data to offer evidence-based recommendations concerning the indications and timing for orbital fracture repair. 9 Repairing a white-eyed blowout fracture within 24 to 48 hours is supported by level A1 evidence. The other indications and timing recommendations for fracture repair are not as strong, and rely on the addition of clinical judgment. A floor fracture associated with diplopia within 30 degrees of primary gaze from limited supraduction or infraduction that persists beyond a week should be repaired ideally within 7 to 14 days, with newer data suggesting repair within 7 days having better long-term results. 10 Fractures that have a disproportionate amount of soft-tissue disruption compared to the fracture size (e.g., a minimally depressed floor fracture but with a significant “teardrop” deformity of the inferior rectus muscle) may also benefit from earlier repair. 11 Enophthalmos at presentation is generally always associated with a large fracture or combined floor and medial wall fracture, and the enophthalmos can be expected to only worsen as edema subsides; thus, such a fracture should be considered for repair. Any fracture of 50% or greater of the surface of the orbital floor or combined floor and medial wall should be considered for surgical repair because of the high likelihood of developing problematic enophthalmos. The normal discrepancy of exophthalmometry measurements between the two eyes in normal individuals is up to 2 mm. 12 Thus, the development of latent enophthalmos of 2 mm or greater may be an indication for surgical repair if cosmetically unacceptable to the patient. Even after repair, however, some enophthalmos can persist from internal soft-tissue scarring, imperfect reconstruction, or orbital fat atrophy following trauma and surgery. 13 Still, delayed repair of a fracture in a patient who has manifested latent enophthalmos can have good success and should not be discounted. 14
10.2.2 Implant Materials for Orbital Reconstruction
A variety of implant materials have been employed for orbital fracture reconstruction, including autologous tissue (e.g., nasal septum cartilage, calvarial bone graft) and alloplastic materials (such as nylon foil, porous polyethylene sheeting, and titanium mesh). The author uses almost exclusively alloplastic implants because of their ease of use, lack of donor site morbidity, and safety and effectiveness.
One implant material that is thin, flexible, and inexpensive is nylon foil. This is a clear sheet with physical characteristics similar to X-ray film, and is available in a variety of thicknesses. The author most commonly uses 0.4-mm sheets for small isolated orbital floor or medial wall fractures with excellent surrounding bony support. It can also be used as a “wraparound” implant for combined floor and medial wall fractures, particularly when the inferomedial orbital strut is intact. 15 The material is smooth and this is viewed as a positive attribute in terms of not adhering to orbital tissues such as rectus muscles, but this can also make the implant prone to shifting. Thus, a single microscrew is often placed anteriorly to stabilize the implant and prevent migration. 16 Smooth implants, while being nonadherent, do carry a risk of encapsulation and subsequent hematic cyst formation. 17
Porous polyethylene is flexible and malleable while retaining some rigidity, and as a result of being porous undergoes fibrovascular ingrowth into the implant itself, which serves to stabilize the implant and in theory avoid infection and encapsulation. These implants are available in variable thicknesses, including 0.45, 0.85, 1, and 1.5 mm. They are also available with an optional smooth “barrier” surface to prevent fibrovascular ingrowth on one or both surfaces. Porous polyethylene is “sticky” and adheres to the orbital soft tissues (fat, periosteum) and is generally resistant to shifting. The author most commonly employs nonbarrier porous polyethylene sheets for medium-sized blowout fractures with good surrounding bony support. There have been reported cases of latent implant inflammation. 18 Barrier sheets are susceptible to capsular formation and hemorrhage similar to any other smooth implant. 19 For larger fractures, porous polyethylene sheets can be cantilevered from the orbital rim with a titanium miniplate; composite implants of porous polyethylene with an inner layer of titanium (for rigidity and enhanced malleability) are also available. Beware, though, that porous polyethylene, being flexible, can bow as the orbit swells postoperatively, or could be drawn down to a depressed bone plate during the fibrovascular in growth phase. This could have the effect of creating a concave orbital floor configuration (as opposed to convex) and can lead to latent enophthalmos or diplopia ( ▶ Fig. 10.3).
Fig. 10.3 A maxillofacial CT (computed tomography; soft tissue, coronal reconstruction) scan obtained at postoperative month 3 in a patient with persistent vertical diplopia in down gaze following orbital fracture repair with a porous polyethylene sheet. The scan shows a very large fracture spanned by the porous polyethylene sheet with some soft tissue below the implant. The very large size of the fracture (essentially the whole floor with very little residual bony support) may have been better reconstructed with a rigid implant to avoid “bowing” into the maxillary sinus.
Titanium alloy is an inert and lightweight nonferrous metal with appropriate rigidity for implant reconstruction. Because of its ability to hold shape, manufacturers have been able to fabricate preformed orbital implants that are based on an averaging of CT scan data of many patients to create implants that replicate the natural shape of the orbit. These implants span the orbital floor to the medial orbital wall, and maintain the natural convexity of the orbital floor medially and the natural angle from the floor to medial wall transition by the inferomedial orbital strut. They are available in left or right configurations, small and large sizes, and are fenestrated to allow drainage of blood and fluid out of the orbit into the adjacent paranasal sinus. The author prefers these implants for reconstruction in large fractures where there is little of the floor left, floor fractures with disruption of the inferomedial orbital strut, and combined floor and medial wall fractures, especially if there is disruption of the inferomedial orbital strut. Once the implant is cut to size (if needed) and the shape fine-tuned (if needed), it is placed and fixated to the internal inferior orbital rim laterally with a single microscrew. Screws can also be placed on the anterior face of the inferior orbital rim with screw points that fold over the rim; however, efforts should be made to avoid this as the screws and implant could be palpable or could contribute to scarring and lower lid retraction postoperatively. Because the implant is fenestrated, secondary removal if necessary can be difficult as the orbital soft tissues will be strongly adherent to the implant. Care must be taken to ensure tissue or muscle is not herniated around the implant and that bare extraocular muscle is not in contact with the implant or a restrictive strabismus could result. There have been reports of “orbital adherence syndrome” in which the orbital tissues/extraocular muscles/eyelid become tightly scarred to the titanium implant and are very difficult to remedy. 20 And while the rigidity of the implant is on balance a strength and reason for its use, one must be careful when cantilevering the implant that the rise posteriorly is not too high, or else an optic nerve compression or direct nerve injury could result, with catastrophic consequences. Unlike nylon foil or porous polyethylene, which will generally “mold” to the native surrounding orbital shape, the titanium implant will not do this and thus correct position and angulation must be ensured intraoperatively, and rechecked carefully after screw fixation.
While preformed implants reconstruct the orbital shape quite well, custom-made patient-specific implants are available. These are created by the manufacturer based on individual patient CT imaging data with the goal of reconstructing an orbit to closely match the contralateral normal orbit. These implants can be made from titanium or alloplastic material. Cost and production lead time limit their use in most primary fracture repair settings, but this type of implant can be valuable in difficult secondary reconstructions.
10.3 Surgical Techniques
10.3.1 Transconjunctival Approach to the Orbital Floor
A variety of approaches exist to access the orbital floor, including transcutaneous incisions below the lashes, transcutaneous incision over the orbital rim directly, and transconjunctival incision, often performed with a lateral canthotomy and inferior cantholysis (i.e., the “swinging eyelid” approach). 21 There has been a movement away from transcutaneous approaches to the orbit, as these can be associated with visible scarring and cicatricial ectropion of the eyelid. The author most commonly employs the swinging-eyelid approach to the floor; however, in children with small trapdoor fractures in whom wide exposure is not as critical, the floor is often accessed without disturbing the lateral canthus.
The patient is supine on the operating table and under general anesthesia. The lateral canthus and lower eyelid are injected with local anesthetic (2% lidocaine with epinephrine 1:100,000 mixed 1:1 with 0.75% bupivacaine with the addition of hyaluronidase). The patient is administered 10 mg of intravenous dexamethasone if not medically contraindicated and 1 to 2 g of intravenous cefazolin (or other antibiotic if allergic). After prepping and draping in the usual sterile fashion a corneal scleral protecting shield is placed over the operative eye. Prior to placing the shield, forced duction testing can be performed in which the conjunctiva of the eye is carefully grasped with toothed forceps near the limbus (where conjunctiva is fused with Tenon’s fascia) and the eye is rotated up and down and side to side to assess for any restriction of movement. A curved Stevens tenotomy scissors is then used to perform a lateral canthotomy (cutting full thickness across the lateral eyelid commissure within a horizontal lateral canthal rhytid for approximately 0.5 to 1 cm toward the lateral orbital rim) and inferior cantholysis (turning the scissors to point toward the patient’s feet and cutting the firm tissues of the inferior crus of the lateral canthal band and orbital septal attachments to “release” the eyelid). The closed scissors are then placed through the lateral canthal incision and directed medially in the preseptal/postorbicularis plane across the lower lid until the tips reach alignment with the most medial eyelashes, and the scissors are opened to perform a blunt preseptal dissection. The scissors are then backed out laterally and opened such that one tine of the scissors remains in the preseptal plane and the other tine is over conjunctiva. The scissors are then used to cut the fused layers of conjunctiva, lower lid retractors, and orbital septum from the inferior border of the tarsal plate across the eyelid proceeding lateral to medial, taking care not to disrupt the lacrimal canaliculus medially. This yields an efficient preseptal exposure and avoids any thermal injury to the conjunctival and orbital septum from the use of monopolar cautery. Hemostasis is obtained with careful use of bipolar cautery if needed. A 4–0 silk traction suture is placed through the cut end of the conjunctiva and lower lid retractors and clamped superiorly to the head drape, while a Desmarres retractor holds the eyelid inferiorly. A malleable retractor is used to hold the orbital soft tissues down to isolate the inferior orbital rim. The overlying soft tissues can then be cut with a no. 15 blade or at this point with a monopolar cautery device. Care is taken to ensure that the cheek and lid skin is not rolled up superiorly and overlying the rim by the assistant applying downward traction on the cheek skin. The periosteum of the orbital rim is then elevated with a Freer periosteal elevator and the orbital fracture is revealed. Careful subperiosteal dissection is performed around the fracture site medially and laterally, and then the herniated tissues are elevated back into the orbit using a hand-over-hand technique between the Freer elevator and malleable retractor. Sometimes a skeletonized infraorbital nerve/neurovascular bundle is encountered, and this must carefully be separated from the overlying orbital soft tissues. Medially, care is taken to not disrupt the origin of the inferior oblique extraocular muscle, which originates near the entrance to the nasolacrimal duct. The dissection proceeds to the posterior extent of the fracture so that all orbital soft tissues are returned to the orbit and the fracture is entirely exposed. Free fragments of bone are carefully removed during dissection so that they do not become lost in the orbital fat and intraconal space, from which pain, globe, or nerve injury or vision loss could result. There is a perforating neurovascular bundle from the center of the orbital floor from the infraorbital canal into the orbit 22 ( ▶ Fig. 10.4). If this is intact, it should be identified, cauterized, and lysed so that it is not inadvertently lacerated, which could lead to hemorrhage. Sometimes the floor fracture extends all the way posteriorly to the palatine bone. There are essentially no critical structures along the orbital floor to prevent full dissection and release of the fracture all the way posteriorly; however, pauses should be taken every few minutes to avoid sustained retraction on the orbital soft tissues, which puts stress on the globe and optic nerve. Once the fracture is entirely exposed and all soft tissues have been elevated back into the orbit, the fracture site is covered with an implant. In small fractures or trapdoor fractures in which the bony defect is small, the author prefers a 0.45-mm porous polyethylene sheet or a 0.4-mm nylon sheet. The porous polyethylene is generally not fixated, while the nylon sheet is fixated anteriorly with a single 4-mm self-drilling microscrew. For medium-sized fractures, the author prefers 0.85- or 1.0-mm porous polyethylene sheets, usually fashioned in a “guitar-pick” shape to span the fracture circumferentially. For very large fracture, the author prefers preformed titanium orbital implants that are fixated anteriorly with one or two 4-mm self-drilling microscrews on the inner surface of the orbital rim. These implants are cut down to size as needed and then carefully positioned taking great care to ensure there is no herniation of orbital soft tissue around the edges of the implant and that the implant is directly on bone in the subperiosteal space. The implant should be resting on the posterior-most bone behind the fracture site, called the posterior ledge, which is often the palatine bone in such large fractures. This ensures that the trajectory of the floor is maintained (which is a rising trajectory proceeding posteriorly; see ▶ Fig. 10.5). Forced duction testing is then performed to ensure the eye is freely mobile, confirming that there is no tissue entrapment. It is very rare for the author to suture the periosteum or orbicularis muscle, but instead a “sutureless” technique is employed. 23 When a lateral canthotomy/cantholysis has been performed, this is repaired with a double-armed 5–0 Polyglactin suture placed intratarsally from the cut edge of the tarsus to the firm tissue of the lateral canthal band in horizontal mattress fashion. The lateral canthal angle is reformed with a 7–0 Polyglactin sutured cerclage placed gray line to gray line from the upper to lower eyelid, with the knot placed within the lateral wound. A 6–0 fast gut suture is used to close the conjunctiva of the lower eyelid with two simple interrupted sutures (one at the medial third and one at the lateral third), taking care to take very small purchase of conjunctiva only. The skin of the lateral canthus is then closed with 6–0 fast gut simple interrupted sutures. The protecting shield is removed from the eye, the patient is undraped, and the skin is cleansed, followed by the application of erythromycin ophthalmic ointment to the operative eye. The patient is then awoken from anesthesia and extubated and taken to the recovery room and observed for any bleeding ( ▶ Fig. 10.6, composite).
Fig. 10.4 Surgeon’s view of the right orbital floor in a cadaver dissection showing the orbital perforating neurovascular bundle exiting the mid-infraorbital canal and entering the orbital soft tissues.