Monday, January 14, 2008

Nasoethmoid Orbital Fractures

Continuing with my review of facial fractures. Today is the area between the eyes--the nasoethmoid orbital region. Nasal fractures represent the third most commonly broken bone in the body, and the nose is the most commonly broken facial bone. There is a nice review of simple, acute nasal fractures here.

A facial fracture is considered a nasoethmoid orbital [or naso-orbital-ethmoid (NOE)] fracture if the fracture involves the bone to which the medial canthal tendon is attached. It is important to distinguish NOE fractures from isolated nasal fractures, orbital rim fractures, and fractures which involve only the ethmoid labyrinth. The medial canthal tendon provides globe (eye) support as part of a suspensory sling, which is in continuity with the lateral canthal tendon, and upper and lower tarsal plates. The tendon is also intimately associated with the lacrimal drainage apparatus.

The naso-orbito-ethmoid complex is composed of a confluence of several bones: (1) frontal bone, (2) nasal bone, (3) maxillary bone, (4) lacrimal bone, (5) ethmoid bone, and (6) sphenoid bone. The key anatomical region is the central bone fragment of the medial orbital rim, into which the medial canthal tendon inserts.

Nasoethmoid fractures typically result from a forceful blow to the central aspect of the midface. Motor vehicle accidents are the most common source of injury, followed by assault. Possibly due to the advent of safety air bags in most newly produced vehicles, the incidence of these injuries is decreasing. Less forceful injuries are needed to cause NOE fractures than zygomatic, maxillary, or frontal fractures.

DIAGNOSIS

The best way to confirm the diagnosis is the combination of physical examination and CT scan. Even with soft tissue swelling, physical examination/observation may be informative.

  • Focal areas of swelling or hematoma may overlie an isolated fracture. Periorbital swelling may indicate LeFort II or III fractures.
  • Palpation may reveal mobile bony segments, step-offs, or crepitus, all of which suggest fracture.
  • If the entire nasal pyramid is posteriorly displaced or "telescoped in", the diagnosis is obvious.
  • Measurements of the intercanthal distance should be compared to the interpalpebral distance of the eyes. If the former is significantly larger than the latter, traumatic telecanthus from NOE fracture is presumed. In patients in whom edema makes localization of the medial palpebral angle imprecise, an alternative measurement is interpupillary distance, which should be approximately double the intercanthal distance. If intercanthal distance exceeds one-half the interpupillary distance, traumatic telecanthus must be considered. Normal values are 60 to 70 mm (interpupillary) and 30 to 35 mm (intercanthal).
  • The eyelid traction test is another test for the integrity of the MCT. To do this test, the examiner grasps the lower lid in question and pulls laterally while palpating the nasal root. A lack or reduction of tension with lateral pull suggests NOE fracture with MCT displacement.
  • A thorough eye examination with visual acuity, pupillary responses, and extraocular motion is crucial. Close inspection of the lower lid may reveal a rounded medial palpebral fissure and lid laxity.
  • Although epiphora (overflow of tears) may be associated with NOE fractures, its presence is an unreliable indicator of injury. Lacrimal function may be assessed more accurately by placing irrigation and probing in conjunction with the Jones dye test of lacrimal function.
  • Any fluid from the nose should raise the possibility of a CSF leak. If enough fluid can be collected, it should be sent for analysis of beta2-transferrin, an indicator for CSF. A cruder test for CSF may be performed by collecting a few drops of fluid on filter paper and examining the pattern of migration of fluid. Blood and water tend to form a central pool, while CSF tends to form a second outer ring.

IMAGING

Patients with suspected facial trauma should initially be evaluated with a complete craniofacial CT scan. A full facial analysis from the top of the head through the mandible with 1.5 mm axial cuts will allow coronal reformatting without additional scanning. Plain radiographs have limited utility in assessing isolated nasoethmoid fractures. These films may demonstrate opacification or clouding of the maxillary and ethmoid sinuses, indicating the presence of blood. They are unlikely to characterize the relatively detailed osseous anatomy of the NOE complex. Therefore, CT scan images have replaced plain films as the main imaging tool to assist in the diagnosis and treatment planning for NOE fractures.

FRACTURE CLASSIFICATION

Markowitz and colleagues classify NOE injuries into three fracture patterns accordingly

Type I--single, noncomminuted, central fragment without medial canthal tendon disruption

Type II--comminution of the central fragment without medial canthal tendon disruption

Type III--severe central fragment comminution with fracture extension through the medial canthal insertion or have avulsed the tendon insertion

SURGICAL TECHNIQUE

A combination of four different incisions may be used to provide complete exposure to these fractures--the coronal, a limited midline, a lower eyelid, and the upper buccal sulcus.

Type I Fractures

  • These can be managed with plate-and-screw fixation. The large single-segment fragment must be reduced and then stabilized at the superior orbital rim and piriform. Sargent avoids the eyelid incision in these.

Type II Fractures

  • These fractures require wider exposure to adequately reduce and stabilize. The most common incisions used for both Type II and III fractures are the coronal, lower eyelid, and upper buccal sulcus.
  • The key bone segment to identify is the medial orbital rim bone, into which the medial canthal tendon (MCT) inserts. Care must be taken not to inadvertently strip off the MCT insertion.
  • The key step in the stabilization of the canthal-bearing bone segments is placement of the transnasal wires to obtain a symmetric, secure reduction of these bone fragments. Sargent states that screw-and-plate fixation is not an effective technique in this particular step of stabilization of either Type II or III. There are some nice pictures of his technique in the PRS supplement, Dec 2007 listed below in the references.

Type III Fractures

  • Sargent states that it is rare for the tendon to be completely avulsed unless there is a penetrating injury over the tendon.
  • If the bony fragment to which the MCT inserts is not large enough to place two drill holes approximately 4 mm apart with several millimeter of surround good bone, it should be replaced with a bone graft so that there is adequate support.
  • If the MCT is partially avulsed and the medial bone fragment is of adequate size, the tendon should be reinforced.
  • A slight over-reduction is often needed and can be easily accomplished by continued twisting of the wires.

Other associated fractures (zygomatic, orbital defects, etc) and will need to be addressed as appropriate.

Commonly, there is telescoping of the nose (bridge of the nose is pushed-in and compressed). This characteristic appearance on profile indicates loss of support and the need for a cantilever nasal bone graft. Simple reduction of the NOE and septal fracture will not be adequate treatment.

COMPLICATIONS

  • Persistent telecanthus postoperatively implies inadequacy of the original technique or detachment of the transnasal wire. Reexploration is indicated in such instances.
  • Injury to the lacrimal system causes obstruction and epiphora. It is best avoided by intraoperative stenting of the lacrimal puncta and duct. Care should be made to avoid securing wires too low on the medial nasal wall and lacrimal crests so they do not impinge on the lacrimal sac.
  • If the transnasal wires pass too low on the septum in repair of a type III fracture, the wires may pull the MCT inferiorly and result in scleral show and lid laxity. Repair requires repositioning of the wires to a higher point on the nasal septum.
  • Lower lid ectropion may follow a subciliary (eyelid incision) approach. If severe ectropion occurs, breaking up the scar with Z-plasty or skin grafting from the opposite lid skin may be necessary.
  • Nerve injury may have occurred prior to surgery from the initial traumatic insult. Therefore, the status of the main sensory and motor nerves of the face and forehead must be documented prior to surgery. Care should be taken to identify and preserve the supraorbital and infraorbital neurovascular pedicles while the soft tissue flaps are raised. More commonly, supraorbital nerve injury results from nerve stretching when retracting the soft tissue and orbital tissues to gain access to the superior and medial orbital rims.
  • The nose may be foreshortened, with lack of projection and contracture of the soft tissue.

REFERENCES

Craniofacial Trauma; Supplement to Plastic & Reconstr Surgery, Vol 120, No 7, Suppl 2, Dec 2007; Larry H Hollier, Jr MD and James F Thornton MD

Facial Trauma, Nasal Fractures by Vipul R Dev MD and others--eMedicine Article, Oct 3, 2006

Facial Trauma, Nasoethmoid Fractures by David W Kim MD and others -- eMedicine Article, May 26, 2006

Nasoorbitoethmoid Fractures by E Bradley Strong MD and others -- eMedicine Article, April 30, 2007

Naso-orbital-ethmoid Fractures by Michael G. Stewart, M.D.
January 7, 1993; Grand Rounds--Baylor College of Medicine

Naso-orbital Ethmoid and Frontal Sinus Fractures by Jim C Grant, MD and Byron J Bailey, MD-- Grand Round Presentation, UTMB; April 29, 1998 (power point presentation)

Eyelid Anatomy by Bhupendra C K Patel, MD and others -- eMedicine Article, April 11, 2006

Management of the Medial Canthal Tendon in Nasoethmoid Orbital Fractures: The Importance of the Central Fragment in Classification and Treatment; Plastic & Reconstr Surg, 87:843, 1991; Markowitz, B L, Manson, P N, Sargent L A, et al

3 comments:

Buckeye Surgeon said...

So when are you going to write a textbook? Or at least some sort of study guide for med students rotating through plastic surgery. This is all good stuff.

rlbates said...

Thank you.

tyler said...

hi i just came across this. and im wondering if theres anyone out there that can give me advice. i suffered an orbital fracture 3 years ago resulting in double vision. i had surgery once and it didnt work. i still live with double vision. and im thousands in debt. if theres anyone out there that could give me advice it would be greatly appreciated.( charity programs, grants, anything) my email is juoncl@gmail.com