An orbital floor fracture, often termed a blowout fracture, involves a break in the thin bone forming the bottom of the eye socket. The orbit is the bony cavity housing the eyeball, along with surrounding muscles, nerves, and fat. This injury creates a structural defect in the protective bony housing, which can lead to various functional and cosmetic complications.
Understanding the Orbital Floor and Blowout Mechanism
The orbit is shaped like a four-walled pyramid, and the floor is structurally the weakest wall, separating the eye from the maxillary sinus below. It is primarily composed of the maxillary bone, with small contributions from the palatine and zygomatic bones. This thinness is partly due to its position as the roof of the large, air-filled maxillary sinus.
A classic orbital floor fracture results from blunt force trauma impacting the eyeball itself, rather than the surrounding thick bone of the orbital rim. When an object larger than the orbital opening strikes the eye, the force rapidly increases the hydraulic pressure within the enclosed socket. This sudden internal pressure transfers to the weakest point, causing the thin bone of the floor to buckle and break downward into the maxillary sinus cavity.
This downward break is the “blowout” mechanism, which often results in the orbital contents being partially pushed, or herniated, into the sinus below. Orbital fat and sometimes the inferior rectus muscle, which controls vertical eye movement, can become trapped within the fracture site. The entrapment of these soft tissues prevents the eye from moving correctly and causes functional difficulties.
Recognizing the Signs of Injury
A person experiencing an orbital floor fracture will frequently report diplopia, or double vision, especially when attempting to look up or down. This common and specific sign occurs because the inferior rectus muscle, responsible for vertical eye movement, may be physically tethered by the trapped bone or surrounding fascia. The restricted movement prevents the eyes from aligning, leading to the perception of two separate images.
Swelling and bruising around the eye are immediate and obvious indicators of underlying trauma. Patients may also notice altered sensation or numbness over the cheek, upper lip, and gums on the injured side. This sensory change is caused by trauma to the infraorbital nerve, which travels along a groove in the orbital floor. The nerve can be bruised or compressed by the displaced bone fragments, leading to numbness in its distribution.
Another physical manifestation that may become more apparent as initial swelling subsides is enophthalmos, where the eyeball appears sunken deeper into the socket. This sunken appearance results from the orbital contents, specifically fat and connective tissue, prolapsing through the fracture and into the maxillary sinus. Pain upon attempting to move the eye is a highly specific sign of muscle involvement. In children, nausea and vomiting may occur due to activation of the oculocardiac reflex.
Medical Confirmation and Assessment
The medical evaluation begins with a thorough clinical assessment of the eye’s function and movement. Doctors specifically check for limitations in vertical gaze to determine if the muscle is entrapped. Visual acuity testing is also performed immediately to ensure the injury has not compromised the patient’s ability to see clearly.
A specific clinical maneuver called a forced duction test is often used to confirm if the restriction in eye movement is due to physical entrapment. This test involves using a fine instrument to gently move the eye manually. If the eye cannot be moved, it confirms a mechanical restriction from trapped tissue, differentiating it from simple nerve paralysis.
The definitive diagnostic tool for an orbital floor fracture is the Computed Tomography (CT) scan. The CT scan provides detailed cross-sectional images that clearly show the exact location and size of the bony defect. This imaging is essential for determining whether soft tissues, like the inferior rectus muscle or orbital fat, have herniated into the sinus. The scan also allows medical professionals to measure the degree of bone displacement, which is a major factor in determining the necessity and timing of surgical intervention.
Approaches to Repair and Recovery
Management of orbital floor fractures is highly individualized and is determined by the size of the defect and the severity of the symptoms. Smaller fractures, particularly those involving less than 50% of the floor and no significant muscle entrapment, are often managed conservatively with observation. This non-surgical approach allows time for the initial swelling to dissipate and for symptoms like double vision to potentially resolve.
Surgical repair is generally indicated if there is significant or persistent diplopia, particularly when looking straight ahead, or if the fracture involves a large defect in the orbital floor. Another indication for surgery is significant enophthalmos, typically defined as the eye sinking back more than two millimeters. The primary purpose of the operation is to release any trapped orbital contents and restore the structural integrity of the floor.
During the procedure, the surgeon accesses the fracture site, gently lifts the herniated tissues out of the sinus, and places an implant over the bony defect to reconstruct the floor. Materials used for this reconstruction vary and can include medical-grade plastic, titanium mesh, or absorbable plates. These implants act as a barrier to prevent the orbital contents from falling back into the sinus and provide support for the eyeball in its correct anatomical position.
Following surgery, patients are typically advised to avoid strenuous activities and any action that increases pressure in the head, such as forcefully blowing the nose, for several weeks. Patients can usually resume normal activities approximately three weeks after an uncomplicated repair. While swelling and bruising gradually disappear over weeks, the full resolution of double vision can sometimes take several months as the muscle recovers from trauma and manipulation.