An orbital floor fracture, also called a blowout fracture, is defined as a fracture of the orbital floor with the inferior orbital rim preserved.
About 10% of all maxillofacial fractures are isolated orbital wall fractures, and most of these occur in the orbital floor. The orbit is involved in 30-40% of all maxillofacial fractures. Isolated orbital floor fractures account for 22-47% of all orbital fractures.2)
In an analysis of 268 injured patients, 72% were men and 28% were women, with a mean age of 36 years.2)
As a structural feature of the orbital floor, the bone thickness along the course of the infraorbital neurovascular bundle is only 0.23 mm, and the posterior medial bone thickness is extremely thin at a mean of 0.37 mm. The lateral side is more than five times thicker, at a mean of 1.25 mm. The medial orbital wall and the infraorbital groove are especially thin and are common sites of fracture.
Fractures are classified as open or closed. Closed, or trapdoor, fractures are a form in which the fractured fragment returns to position. They often show little change on imaging, but are prone to entrapment of the extraocular muscles and are more common in children. In children, the thin bony walls make them more likely to occur; the main causes are falls, blows from their own or another person’s knee, traffic accidents, and punches with a fist. Common sites are the maxilla and ethmoid bone, and most often the orbital floor.
They are essentially synonymous. A blowout fracture refers to the phenomenon in which a blow to the eye raises the pressure inside the orbit, causing the thinnest part, the orbital floor, to blow out. Orbital floor fracture is the name that refers to this representative fracture site.
Preoperative clinical findings (out of 262 cases): enophthalmos 33.6%, diplopia 65.8%, limitation of eye movement 55.1%, and decreased infraorbital nerve sensation 46.2%.2)
The findings by fracture type are shown below.
Open-type fracture
Displacement of fracture fragments: The fracture fragments and soft tissue are markedly displaced into the sinus.
Enophthalmos: Because the orbital volume increases, the eyeball moves backward. Enophthalmos becomes more noticeable as swelling subsides after injury.
Prognosis: If there is no entrapment, the prognosis for eye movement is relatively good.
Closed-type fracture
Few imaging changes: Slight displacement at the fracture site and the missing rectus sign are characteristic findings.
With systemic symptoms: Entrapment of tissue can trigger a vagal reflex, causing severe eye pain, nausea, vomiting, fainting, and bradycardia. It may be mistaken for signs of increased intracranial pressure.
High urgency: If extraocular muscle strangulation is present, there is a risk of muscle necrosis and emergency surgery is indicated.
If tissue is entrapped at the fracture site, vertical eye movements can cause nausea and bradycardia (oculocardiac reflex).
The main cause is restricted movement caused by entrapment of the extraocular muscles and orbital tissues in the fracture. Even if orbital septa (septa) within the orbital fat are caught near the extraocular muscles, eye movement can be limited. Diplopia is caused not by the fracture alone, but by a combination of factors such as trauma, soft tissue injury, fibrosis, and nerve contusion.1)
The cause is blunt trauma to the eyeball and the area around the orbit. Causes of injury (analysis of 268 cases): assault 35.1% (most common), falls 21.6%, sports 19.0%, traffic accidents 13.8%, and workplace accidents 1.1%, in that order.2)
There are two theories about how the fracture occurs.
Cadaver studies have found both theories to be valid.
A complete ophthalmic examination is essential. The first step is to rule out complications that threaten visual function, such as globe rupture and retinal detachment.
A CT scan of the orbit is essential for a definitive diagnosis. Thin-slice axial CT (1.0 to 1.5 mm) with coronal reconstruction is standard.
A more than 13% increase in orbital volume raises the risk of enophthalmos. Note that radiologic herniation of the inferior rectus muscle does not necessarily predict clinical motility impairment.
Orbital congestion, extraocular muscle palsy, nerve palsy, diplopia due to loss of fusion, and medial orbital wall fracture are differential diagnoses. Note that entrapment is a purely clinical diagnosis, not a radiologic one.
In Japan, treatment is determined according to the following policy based on fracture type and whether entrapment is present.
The criteria for deciding surgical indication are shown below.
| Situation | Recommended response |
|---|---|
| Closed type, with extraocular muscle entrapment | Emergency reduction surgery within 24 hours |
| Soft tissue entrapment present | Surgery as early as possible (usually within 2 weeks) |
| Open type and irreversible changes are the main cause | Early reduction before scarring |
| Mild diplopia or minor imaging changes | Observation (expect spontaneous improvement) |
In large open fractures, swelling subsides 2 weeks after injury and enophthalmos becomes prominent, so it is important to explain this to the patient beforehand.
The procedure is performed under general anesthesia. The infraorbital rim is reached through a subciliary lower eyelid skin incision or an inferior fornix conjunctival incision. In children, a transconjunctival fornix incision approach is also used. The orbital tissue trapped in the fracture is gently reduced back into the orbit, and improvement in resistance before and after reduction is confirmed with a traction test. In children, mild cases are known in which resistance disappears with traction alone.
If possible, the fracture is repaired using the fracture fragments. In comminuted fractures, reconstruction material is used to fill the defect. A transmaxillary sinus (paranasal sinus) approach is also an option, and there is a method of placing a balloon in the maxillary sinus.
The main characteristics and complication rates of reconstruction materials are shown below.
| Material | Features | Material-related complication rate |
|---|---|---|
| Titanium mesh | Good rigidity and moldability, suitable for large defects | 2.4% (741 cases)3) |
| Porous polyethylene (Medpor) | Fixed by tissue ingrowth, low infection rate | No reports (326 cases)3) |
| Absorbable material (Poly-L/D-lactic acid) | Suitable for small to moderate defects, low complication rate | 3.4% (176 cases)3) |
| Autologous bone (skull, iliac bone, etc.) | Highly biocompatible, but resorption is an issue | Donor-site complications3) |
| Silicone | Low cost and easy to handle | 17.5% (530 cases, highest rate)3) |
In a systematic review of 444 cases, surgery was reported to improve enophthalmos in 85.2%, diplopia in 74.8%, limitation of eye movement in 61.6%, and sensory disturbance in 61.1%.2)
Not necessarily. Mild double vision and movement problems often improve on their own, and observation may be chosen. Closed fractures with entrapment of the extraocular muscles, or persistent double vision and enophthalmos, are the main reasons for surgery.
Two mechanisms have been proposed for the occurrence of orbital floor fractures, and both have been confirmed as plausible in cadaver studies.
Hydraulic theory
Rise in intraorbital pressure from impact: A fist or ball directly strikes the eye, causing the eyeball to shift backward.
Failure at the weakest point: A sudden rise in intraorbital pressure causes the thinnest area above the inferior orbital neurovascular bundle to blow out.
Escape of soft tissue: Orbital contents (fat and muscle) herniate into the sinus through the fracture.
Buckling theory
Propagation of a pressure wave: A pressure wave generated by blunt trauma to the cheek travels backward through the bone.
Compression and buckling of bone: Compression of the bone in the front-to-back direction causes the weakest part of the orbital floor to buckle, pushing bone fragments downward.
Direct bony deformity: Unlike the hydraulic theory, a direct blow to the eyeball is not always required.
The mechanisms of double vision and eye movement disorders are as follows.
The mechanism of enophthalmos is as follows. As orbital tissue herniates into the paranasal sinus through the fracture, the orbital volume increases, the eyeball shifts backward, and enophthalmos occurs.
Use of custom-made implants tailored to each individual’s fracture pattern based on CT images is advancing.
A shortening of surgery time has been reported, with a significant reduction seen in the preformed method (57.3±23.4 minutes) compared with the freehand shaping method (99.8±28.9 minutes).2)
The endoscopic transnasal and transmaxillary approaches are said to cause less soft tissue injury and less decreased sensation in the infraorbital nerve than conventional transcutaneous approaches.2)
In a narrative review of 66 studies and 3,870 cases by Sivam & Enninghorst (2022), neobone formation was confirmed after complete absorption of Poly-L/D-lactic acid, and studies in 94 cases reported significant improvement in eye movement, diplopia, and enophthalmos.3)
In a systematic review by de Santana et al. (2024), the current evidence was considered insufficient to confirm a direct link between orbital floor fracture and eye movement disorders.1) Further multicenter studies are needed to clarify the pathology.
