Hyperguides

Ophthalmology / Oculoplastics

Blow-out Fractures in Adults and Children

Ari D. Abel, MD Dale R. Meyer, MD, FACS
Article


Introduction

Orbital fractures are seen commonly in patients who have blunt trauma to the face and skull. The orbit is involved in trauma since it assumes a prominent position with regard to the craniofacial skeleton.1 These fractures can also involve the globe, eyelids, surrounding bones, sinuses, and brain. It is important that a comprehensive ophthalmic examination be performed to rule out possible intraocular injuries. This can be difficult in the acute setting due to lid and orbital edema or when a patient is not fully conscious. Associated lacerations of the eyelids and lacrimal systems may also need to be addressed at the time of the examination.

Orbital fractures are classified as:

  • Internal fractures: involving the orbital walls
  • External fractures: involving the orbital rims and adjacent bones
  • Complex fractures: involving both the orbital walls and orbital rims1
  • Blow-out fractures: internal fractures confined to the orbital walls, with the floor and medial wall being the most common fracture sites. These fractures result in outward displacement of bone fragments into the associated sinuses (Slide 1).2,3
  • Trapdoor fractures: situations in which a displaced segment of orbital floor remains attached on one side producing a hinged fragment, which can result in muscle entrapment.1 Trapdoor fractures are common in the pediatric population and tend to occur more frequently in this age group as compared to the adult population (Slide 2).5-8
Slide 1 Slide 2

The blow-out fracture is the most common type of orbital fracture that presents to an ophthalmologist. This type of fracture occurs when a blunt object, such as a tennis ball, hockey puck, fist, or elbow, strikes the orbital cavity causing a retropulsion of orbital contents with subsequent elevation of intraorbital pressure. This results in fractures of the thin bones of the orbital floor and medial wall. The area of orbital floor overlying the infraorbital groove is the thinnest portion, making this the site most commonly fractured. These fractures diffuse much of the striking force and limit globe trauma. The major complications of blow-out fractures include ocular motility restriction, which induces diplopia, and enophthalmos.3

Clinical Findings and Clinical Examination

Symptoms associated with blow-out fractures include the following:

  • Diplopia
  • Strabismus
  • Pain on extraocular movement
  • Enophthalmos
  • Infraorbital hypoesthesia
  • Nausea and vomiting: observed with trapdoor fractures, especially in children

A complete ophthalmologic examination is recommended to rule out hyphema, retinal detachment, vitreous hemorrhage, lens subluxation, iridodialysis, ruptured globe, traumatic optic neuropathy, and orbital compartment syndrome secondary to orbital hemorrhage. In addition, there may be fractures of other areas of the skull and face.

Ocular motility examination assesses ocular alignment in both primary and eccentric gaze positions. Limitation of ocular motility may be due to entrapment or restriction of extraocular muscles or the surrounding orbital soft tissues, which can frequently be confirmed on computerized tomography (CT) examinations. The inferior rectus muscle may be involved in floor fractures resulting in limitation of supraduction (upgaze) or, less frequently, infraduction (downgaze). The medial rectus muscle can be affected in medial wall fractures causing a limitation of abduction or, less frequently, adduction. However, diplopia that is present after a recent trauma can be secondary to other ocular motor abnormalities such as a previous phoria that has decompensated due to the injury. Muscle paresis can be secondary to either a direct injury to the muscle itself or an associated cranial nerve injury. Frequently, orbital edema and/or hemorrhage also result in strabismus and diplopia in the early period following injury.

Forced duction testing is helpful to distinguish between muscle restriction and paresis. Orbital edema or hemorrhage can produce a moderately positive test in the early period following the injury. It is worthwhile to wait until the edema subsides before performing forced duction testing. True muscle restriction occurs commonly with trapdoor fractures and predisposes to severe pain on attempted supraduction. It has been demonstrated that supraduction limitations tend to be more significant in trapdoor fractures in which the limitation is usually quite marked.4 Forced duction testing is difficult to perform in children and it is usually deferred until the child is sedated.

Binocular diplopia occurs in the setting of muscle restriction. It is important to quantify the severity and degree of subjective diplopia since this plays an important role in terms of surgical intervention. Diplopia within the central 30° of fixation is usually considered clinically significant.1 However, diplopia beyond 30° of central fixation in downgaze may not be tolerable in some patients. Clinical examination yields a fairly accurate estimation of the range of diplopia. If necessary, the Goldmann visual field perimeter can be used to assess the precise degree of visual impairment in all fields of gaze.

Blow-out fractures take place when orbital walls are displaced in an outward direction. This increases the volume of the orbit and creates enophthalmos. In the acute setting, edema and hemorrhage may produce an exophthalmic picture. Once the swelling subsides, the actual position of the globe becomes apparent. Enophthalmos occurs as a result of a combination of an enlarged orbit space and the prolapse of orbital soft tissue into adjacent sinuses. Chronic soft tissue changes, such as scarring and fat atrophy, can further exaggerate the enophthalmic appearance.1,2 Hertel exophthamometry measures the exact amount of globe displacement along the axial axis. A difference of more than 2 mm between the two eyes is considered to be abnormal. A 3-mm disparity is usually necessary to produce an obvious deformity on clinical examination.

Hypo-ophthalmos is produced by downward globe displacement, which tends to occur in the setting of a large orbital floor defect. In this setting, the inferior corneal limbus drops below the inferior lid margin creating an obvious aesthetic deformity. Extensive orbital floor fractures can even allow the globe to sink into the maxillary sinus.8 A ruler is useful to measure the distance of downward displacement.

Facial hypesthesia is not an uncommon associated finding in blow-out fractures. It presents typically as decreased facial sensation or numbness along the lower eyelid and skin of the upper cheek. This pattern of infraorbital hypesthesia occurs when the infraorbital groove is involved in the orbital floor fracture. The infraorbital groove houses the infraorbital artery, vein, and nerve (CNV1) and is covered only by a thin section of orbital floor that is easily fractured.

It is also important to palpate the lower orbital rim to detect any bony step-offs that may indicate an orbital rim fracture. Palpation along the rim may reveal a crackling sound known as crepitus, which is indicative of orbital emphysema. This tends to take place with medial wall fractures whereby air from the paranasal sinuses becomes entrapped in orbital soft tissue.1 This condition tends to resolve on its own, and patients are instructed to avoid nose blowing.

Radiologic Evaluation

CT scanning is the imaging modality of choice for evaluating internal blow-out fractures and other associated craniofacial fractures. CT provides excellent detail of the orbital bones making it superior to magnetic resonance imaging for the assessment of orbital fractures. Coronal views are the most useful in providing the exact location and size of the orbital wall defects. CT also demonstrates the relationship of the extraocular muscles and orbital soft tissues with the fracture site and can fairly accurately determine whether a muscle rather than fat is entrapped within the defect. This is important because restricted motility on clinical exam can be secondary to either entrapped muscle and/or soft tissue. CT scanning plays a pivotal role in the formulation of a treatment plan.9

Treatment

In the acute post traumatic period, the first decision to make is which fractures must be surgically repaired and which fractures can be observed. Not all isolated internal blow-out fractures need to be repaired, which is why the clinical evaluation and CT are important in establishing a treatment plan. Controversy exists regarding the indications and timing of surgery. Past treatment approaches have varied from repairing all blow-out fractures to repairing none of them. More recently, CT has become a widely accepted and reliable adjunct to help determine the need for early surgical intervention.9 Currently, recommendations for repair within 2 weeks of the trauma are given to patients with:

  • Symptomatic diplopia within 30° of primary gaze
  • Evidence of muscle entrapment on CT and/or a positive forced duction test
  • Large fracture encompassing greater than 50% of the entire orbital floor surface area
  • Displaced orbital rim fracture and/or associated facial fractures, greater than 3 mm of enophthamos
  • Clinically significant hypo-ophthalmos1,10

When frank muscle entrapment is confirmed on both clinical examination and CT, fracture repair within 48 hours is recommended.1,10 Expedient surgical intervention is indicated in this situation to prevent ischemic damage to the extraocular muscle and tissue necrosis, which can cause irreversible motility restriction.5-8,11,12 Muscle entrapment is seen commonly with trapdoor fractures where the prolapsed orbital tissue becomes caught in the fracture. It is believed that the greater elasticity of the orbital bones in the pediatric population predisposes to a higher incidence of trapdoor fractures in this age group.4

Certain conditions can be treated conservatively and observed. These conditions include symptomatic diplopia outside the 30° range of primary gaze without having evidence of frank muscle entrapment, modest-sized isolated fractures, and situations in which there are signs of clinical improvement over a 1- to 2-week period as edema resolves. In cases where symptomatic diplopia persists after edema resolves, surgical intervention can be considered.10

Orbital floor fractures can be approached through various transcutaneous incision sites, which include infraciliary, lower lid crease, and orbital rim margin. A transconjunctival approach also provides excellent exposure of the orbital floor and reduces the incidence of postoperative lid retraction and ectropion.1,13 A lateral canthotomy and cantholysis is helpful to augment exposure when utilizing a transconjunctival incision. It is important to perform forced duction testing prior to performing surgery to assess the actual degree of motility restriction while the patient is sedated.

After the incision is made at one of the aforementioned locations, the dissection is continued down to the orbital rim and the periosteum is exposed and incised just inferior to the edge of the orbital rim. The periosteum is bluntly elevated off the orbital floor with a periosteal elevator to expose the fracture. Once the full extent of the anterior portion of the fracture is exposed, blunt instruments are used to extract soft tissue, fat, and/or muscle from the defect. Next, the full extent of the fractured orbital floor must be exposed after all soft tissue has been released and any residual bony fragments can be extracted.

After achieving complete exposure of the fracture site and releasing all entrapped tissue, the next step is to decide whether to insert an orbital implant. Small fractures may not require the placement of an implant. The ideal implant must cover the orbital defect, have sufficient rigidity to support orbit tissue, be readily available and easy to place, and have biocompatibility. Implant fixation is important for prevention of implant migration or extrusion. Fixation techniques include gluing, placing a 'tab' along the anterior edge of a thin synthetic implant, and direct fixation to the orbital rim with screws, wires, or sutures.

Implants are categorized as either autogenous or alloplastic. Autogenous implants include grafts of bone, cartilage, or fascia. Bone grafts are most commonly used and can be harvested from the cranium, iliac crest, or rib area. Autogenous implants have excellent biocompatibility; however, they may undergo partial resorption over time, which can lead to undercorrection with late-onset enophthalmos. A second procedure is required to harvest the graft, which increases the operating time and can cause donor site morbidity.1,14 Alloplastic implants are defined by their synthetic composition and further characterized as being porous, nonporous, or absorbable. Porous implants are advantageous in that they promote fibrovascular ingrowth, which helps anchor the implant to surrounding tissue and reduces the risk of implant migration. Fibrovascular ingrowth helps to resist the likelihood of infection.

Currently available porous implants include hydroxyapatite and high-density porous polyethylene. Hydroxyapatite has limited use for fracture repair since it is hard, brittle, and difficult to manipulate. High-density porous polyethylene is available as thin sheets, which are easy to handle, contour, and fixate. Medpor also has excellent tensile strength and provides good structural support. Nonporous implants include metallic plates, silicone, Supramid (S. Jackson, Inc., Alexandria, VA), and Teflon (DuPont, Wilmington, DE). Metallic implants are manufactured as micro- or mini-plates, mesh, or grids, and they are typically composed of titanium or vitallium. These metallic implants are usually reserved for orbital rim fractures or large, extensive orbital floor fractures. Absorbable implants, such as polygalactin and gelatin film, tend to be reserved for smaller fractures because they are thin and lack sufficient tensile strength to provide adequate structural support.1,14 More recently, "longer lasting" absorbable implants, such as a LactoSorb (Biomet, Warsaw, IN) have been developed but long-term clinical experience is limited.15 Once the implant is sufficiently secured, the periosteum is closed. The incision is then closed, being careful not to include the septum in the closure so that postoperative lid retraction can be avoided. Prophylactic antibiotics are usually administered perioperatively when synthetic implants are used.

Complications occurring after internal blow-out fracture repair can be due to either the orbital surgery or the orbital fracture. Certain complications can arise in all types of orbital surgery and many of these can be reduced with proper surgical technique. The most significant complication seen as a result of orbital surgery is visual loss, which is rare. This can occur as a result of inadvertent injury to the optic nerve or the globe. Postoperative orbital hemorrhage can induce a central retinal artery occlusion or compressive optic neuropathy. Consequently, the vision and pupils are monitored in the acute postoperative setting to detect any early visual loss or signs of an afferent papillary defect.1 Complications associated with internal blow-out fracture repair include persistent enophthalmos/hypo-ophthalmos, diplopia, and problems caused by orbital implants. Residual enophthalmos and hypo-ophthalmos can be due to soft tissue scarring or insufficient soft tissue support. Postoperative diplopia may be the result of the initial traumatic and/or ischemic muscle injuries or incompletely released entrapped soft tissue.

Complications associated with the use of autogenous and alloplastic implants include infection, inflammation, migration, and extrusion. Donor site morbidity can occur when harvesting autogenous implants.1,14 Fortunately, most of these complications are relatively uncommon and most patients undergoing orbital fracture repair improve with appropriate surgical intervention.

References

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