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Facial Fracture Management Handbook - Nasoethmoid fractures

last modified on: Fri, 09/07/2018 - 10:11

Facial Fracture Management Handbook

return to: Facial Fracture Management Handbook

by Dr. Gerry Funk

 

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Nasoethmoid Fractures

Anatomy and Mechanism of Injury

The nasoethmoid complex can roughly be thought of as the central area of the face below the frontal sinus and anterior cranial fossa, between the orbits, and above the hard palate. The superior margin is defined by the frontal sinus floor, cribriform plate and fovea ethmoidalis. The lateral walls are formed by the frontal process of the maxilla, lacrimal bone, lamina papyracea and frontal bone. The anterior wall is formed by the nasal bones and nasal process of the frontal bone. Large impact forces directed to the nose and nasal dorsum are capable of impacting this bony complex posteriorly and telescoping the anterior bony components into the more posterior ones. The medial orbital walls tend to be splayed laterally in severe telescoping injuries. The characteristic appearance of a severe nasoethmoid fracture is that of a flattened nasal dorsum, and traumatic telecanthus with blunted medial canthal angles. Loss of the rigid attachment of the medial canthal tendon to the frontal process of the maxilla, lacrimal bone, frontal bone and orbital lamina of the ethmoids or fragmentation of the bones which have remained attached to the medial canthal tendons allows them to splay laterally. Frequently frontal sinus fractures accompany severe nasoethmoid fractures.

Physical Exam

Head and neck trauma exam with special attention to:

1. Bony contour of the forehead and root of the nose, check for any step off's.

2. Careful ocular exam with special attention to globe position, diplopia and extraocular movements.

3. Measure the intercanthal distance. There are a number of approximations to the normal intercanthal distance: 1) approximately 30 - 35 mm, 2) half the interpupillary distance, 3) the palpebral fissure width and 4) 1/5 the width of the face at the level of the eyes.

4. Carefully examine the nose for evidence of CSF rhinorrhea and septal hematoma.

5. Be sure that the palate is not mobile.

6. Check sensation in the distribution of cranial nerve V1.

Emergency Management

The emergency management of these fractures revolves around excluding intracranial injury, cerebrospinal fluid leak or an associated ocular injury. An MRI or CT of the brain should be done to evaluate for evidence of frontal contusion. Careful examination of the nose for clear fluid and questioning the patient about the sensation of fluid in the back of the throat or nose at the time of admission and during the first few days of admission is important to rule out CSF leak. If clear fluid is present it should be collected and sent for glucose levels with a simultaneous blood sample. The concentration of glucose in CSF is usually greater than or equal to 50 mg%. Although not diagnostic of CSF if positive, several negative glucose tests of nasal secretions with a common glucose dipstick (Clinistix, Dextrostix, Uristix) essentially excludes a CSF leak. The glucose oxidase test on which these are based is quite sensitive and will be positive at values under 20 mg% (38). If only a small amount of fluid is available and glucose levels cannot be measured accurately, then beta-2-transferrin levels of the fluid should be sent. Beta-2-transferrin is very specific for CSF. Patients with severe nasoethmoid fractures should be placed on antibiotics due to blood in the sinuses and the communication of sinonasal secretions with the orbit.

Radiographic Work Up

At the time of the brain imaging study axial and coronal, fine cut, bone window CT scans including the frontal sinus, skull base, orbits and central sinonasal compartment should be obtained. The Coronal cuts are important for evaluation of the orbital walls and skull base (cribriform area and fovea ethmoidalis). The axial views are useful in evaluating both walls of the frontal sinus. Be sure to look closely for any evidence of intracranial air. If a CSF leak is present the CT may provide information on its location, the most likely area will be the cribriform plate or fovea ethmoidalis. If a CSF leak persists following repair of the fractures despite conservative measures (bedrest, lumbar drain) a metrizimide CT is the best radiologic study to look for the exact area of leak, radionuclide pledget studies have the highest rate of misleading, false positive information and are of little value in the trauma patient with a known leak (39).

Definitive Management

If an associated frontal sinus fracture is present, the operative plan should include the definitive repair of this fracture in conjunction with the nasoethmoid fracture (see frontal sinus fracture management below). The majority of nasoethmoid fractures are approached through a coronal incision and a transconjunctival or sublabial incision if inferior exposure is needed. Medial nasal wall or Lynch type incisions should be avoided. The healing of these incisions when used for repair of nasoethmoid fractures is frequently not optimal.

The most important goals in the repair of nasoethmoid fractures are to correct the telecanthus and bring the nasal dorsum up into a normal anatomic position. The correction of traumatic telecanthus is one of the most difficult challenges in bony facial trauma surgery. In order to repair the telecanthus, intraoperative overcorrection is the rule.

To simulate the three components of the normal medial canthal tendon (anterior horizontal, posterior horizontal and vertical, the disrupted medial canthal tendon or medial canthal tendon with attached bone fragment is secured to a point corresponding to the top of the posterior lacrimal crest (40). This is usually done following preliminary fixation of surrounding frontal and orbital bone fractures with plates and screws. If there is stable bone on the contralateral side the medial canthal tendon can be looped with a 28 ga. wire and secured to bone on the opposite side. If the bone on the opposite side is also fractured and not stable the best method of securing the medial canthal tendon is to place a small screw into the bone of the contralateral anterior, superior orbital wall and tightening the wire around that screw. If an associated frontal sinus fracture is present the wire can often be brought up through the obliterated frontal sinus and secured to a screw placed into the frontal bone. In some cases the medial canthal tendons can be secured to each other using a transnasal wire, however if the orbital walls are not stable the wire will tend to move anteriorly resulting in return of a telecanthic appearance. Despite a technically well done surgery some patients will over time note a return of the traumatic telecanthus and blunted medial canthal angles. This probably results from a loosening of the fixation wire or disruption of the medial canthal tendon at the point of fixation with the wire. In these cases revision surgery may be warranted.

Restoration of the normal dorsal nasal contour is frequently accomplished by fixation of the fractured nasal and frontal bone fragments back into anatomic position. In some situations these bones will be extensively comminuted and unstable. In these cases a dorsal nasal graft of pericranial bone will restore the appearance of a narrow, strong nasal profile. The pericranial bone graft is secured to the frontal bone using a miniplate and screws or lag screws.