The diagnosis of orbital fractures is based on clinical and radiographic findings. Although many signs and symptoms have been described, the common signs include periorbital ecchymosis and edema, the presence of a palpebral or subconjunctival hemorrhage or hematoma ("the spectacle hematoma"), limitation of extraocular function (due to entrapment of orbital contents, edema, or neurologic sequelae), hypoesthesia in the distribution of the infraorbital nerve and enophthalmos.
Radiologic assessment of suspected orbital fractures should be performed with CT scanning as plain films are of little diagnostic benefit. Both axial and coronal views (1-3 mm) with reconstruction are preferable. Common CT findings of orbital floor fractures include an air-fluid level in the ipsilateral maxillary sinus, a trap door deformity of the orbital floor with herniation of intraorbital contents, and various other orbital rim or wall fractures. There are two prevailing theories for the mechanism of orbital floor fractures.
First, the hydraulic theory attributes the fracture to a sudden increase in intraorbital pressure. The elevation in pressure on the thinnest bone segment in the orbit, the floor, causes a blow-out fracture to ensue. The buckling theory attributes orbital floor fractures to the force transmitted to the infraorbital rim causing acute deformation with or without fracture. The force is passed on to the thin orbital floor which cannot adequately resist the force and fractures.
A wide range of associated ocular and periocular injuries have been reported in the literature (2-93%). Interestingly, the reported rate of associated injury is much lower for nonophthalmologist (2-25%) compared to ophthamologists (9-93%). A recent study of 365 patients with orbital fracture had an associated ocular injury rate of 26%.
The injuries which required immediate opthalmologic intervention were as follows: traumatic optic neuropathy (35%), elevated intraocular pressure >40 mm Hg (26%), hyphema (22%), traumatic iritis (9%) and ruptured globe (9%). As a general rule, all patients with orbital fractures require evaluation by an ophthalmologist.
Indications for treatment of a subacute orbital fracture (within 2 weeks of injury) include entrapment, enophthalmos, exophthalmos and bony defects greater than 1 cm2. The indications for immediate repair of acute orbital fractures are a nonresolving oculocardiac reflex, young patient (<18 yrs) with "white eye blow-out" associated with severe muscle entrapment, and a large fracture with globe prolapse into the maxillary sinus.
Since orbital volume is roughly 20-30 ml, a 10% change in orbital volume (2-3 ml) may produce enophthalmos. As small volume changes can produce significant symptoms, a primary goal of treatment is anatomic reduction of the fracture to reestablish preinjury volume. If loss of osseous tissue interferes with anatomic realignment then autogenous or alloplastic grafts are necessary.
Autogenous grafts described for orbital reconstruction include: bone (calvarium, ilium, rib, maxilla and mandible) or cartilage (nasal septal, costal and auricular). Calvarial grafts have been shown to be most beneficial in immediate reconstruction but tend to have problems with resorption when utilized in a delayed repair. Although described in the literature, cartilage grafts are infrequently used.
Alloplastic implants can be divided into bioresorbable and nonbioresorbable types. Allogeneic bone and cartilage, lyophilized dura, gelatin film, polydiaxone plates, polylactide plates, and polglactin mesh and plates are all examples of bioresorbable alloplasts used in orbital reconstruction. The advantage of all alloplastic implants is their inherent lack of donor site morbidity. The disadvantages of lyophilized dura and allogeneic grafts are the lack of cellularity and potential for disease transmission.
The primary disadvantage of resorbable plate systems is the concern over long term stability especially in larger bony defects. Nonbioresorbable implants include: silicone, methylmethacrylate, ceramics, polyurethane, polyethylene, porous polyethylene, titanium mesh and plates. All of these materials provide rigid support but have somewhat higher rates of infection than autologous tissues.
Porous polyethylene has been shown to allow for fibrovascular ingrowth with pore sizes between 100-200 micrometers. Titanium mesh and porous polyethylene have been shown to mucosalize on the sinus-exposed surfaces of the implant.
Regardless of the method of reconstruction, patients with post-traumatic enophthalmos should be over corrected 2-3 mm to ensure adequate correction after resolution of edema. Over correction also helps to account for any volume loss secondary to fat necrosis. Opinions differ on the placement of orbital grafts. Some advocate rigid fixation, particularly of autogenous bone grafts, in an attempt to increase "take." Others merely place grafts to span the defect and allow the soft tissue to redrape over the graft.
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