TITLE: Orbital Floor Fractures
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: April 11, 2007
RESIDENT PHYSICIAN: Jacques Peltier, MD
FACULTY PHYSICIAN: Francis B. Quinn, Jr., MD
SERIES EDITORS: Francis B. Quinn, Jr., MD and Matthew W. Ryan, MD
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Fractures of the orbit and floor are among the m= ost common of the midface. Evalua= tion of the patients involves a complete history, head and neck physical, and appropriate imaging of the sights involved. As motor vehicle accidents and blu= nt trauma account for the majority of these injuries, they are often associated with multiple facial and multisystem trauma. The isolated orbital floor fractur= e, also known as a blowout fracture, is not as common as floor fractures associated with the orbital rim and lateral buttress, also known as tripod fractures. Never the less, th= ese fractures do occur in isolation, most commonly with direct blunt trauma to = the eye. Below follows a discussi= on of the isolated orbital floor fracture. Most of the principles discussed in management of the isolated floor fracture can be applied to floor fractures associated with other midface and mandibular trauma.
Anatomy
The orbits are complex bony structures with stru= ctural contributions from multiple facial and skull bones. In addition to the fron= tal, zygomatic, and maxillary contributions discussed previously, the lacrimal b= one sits behind the maxillary bone medially. The maxillary bone and the lacrimal bone together form the lacrimal fossa, which houses the lacrimal sac. The strong anterior (maxillary bone) and posterior (lacrimal bone) lacrimal cre= sts provide the sites of attachment of the components of the medial canthal ligaments. Note that the medial canthal ligaments have three components: an anterior, posterior, and superior attachment. The thin lamina papyracea of = the ethmoid bone completes the medial orbital wall. The palatine bone makes a s= mall contribution posteroinferiorly. The posterior lateral orbit is provided by = the greater wing of the sphenoid, and the solid optic canal bone is contributed= by the lesser wing of the sphenoid. The optic canal sits posteromedially behind the medial wall, where it is generally protected from all but the most seve= re of injuries. Note that the optic foramen is actually directed toward the lateral orbital rim rather than directly anteroposterior. The important "orbital apex" includes the area lateral to the optic canal throu= gh which cranial nerves III, IV, V, and VI pass to enter the orbit, which is considered part of the superior orbital fissure. When pressure from an inju= ry (or tumor, abscess, or hematoma) causes dysfunction in these nerves, it is called superior orbital fissure syndrome and requires urgent surgical intervention.
It is important to remember the shape of the orb= it before attempting repair of the floor.&nbs= p; Repairing the orbital walls and recreating the orbital volume is necessary to allow repositioning of the globe into its normal anatomical position. As such, it is impo= rtant to remember that the floor is concave inferolaterally and tends to be more convex medially and becomes significantly convex posteriorly behind the equ= ator of the globe.
Important in the design of the orbit is its inhe= rent ability to protect vital structures by allowing fractures to occur. Because the globe is surrounded by= fat and the medial wall and floor of the orbit are thin, force that is transmit= ted to the globe allows fracture of the orbit without significant globe injury. This accounts for the significantly higher incidence of fractures of the orbit as compared to open globe injuries.
History and Physical
Most patients present after facial trauma and may describe decreased visual acuity, blepharoptosis, binocular vertical or obl= ique diplopia (especially in upgaze), and ipsilateral hypesthesia, dysesthesia, = or hyperalgesia in the distribution of the infraorbital nerve. Nausea and vomi= ting are important points of the history to elicit. In one study, 83% of children with trapdoor fractures and nausea and vomiting were found to have entrapment of= the inferior rectus muscle on intraoperative exam. In addition, some patients may com= plain of eyelid swelling following nose blowing, as well as epistaxis.
Periorbital ecchymosis and edema accompanied by =
pain
are obvious external signs and symptoms, respectively. Enophthalmos may be
discerned, but initially it can be obscured by surrounding tissue swelling.
This swelling also may restrict extraocular muscle motility, giving the
impression of entrapment within the floor defect. Proptosis may result from
retrobulbar or peribulbar hemorrhage. Palpation of the orbit may reveal
Examination of the globe is essential and may be difficult secondary to soft tissue edema.&= nbsp; Pupillary dysfunction, if present, coupled with decreased visual acu= ity should alert to the possibility of a traumatic optic neuropathy. Ocular misalignment, hypotropia or hypertropia, and limitation of elevation in the affected eye that is not found to the same degree in the contralateral eye = can be present. Forced duction tests aid in differentiating entrapment from neuromyogenic etiology. The supratarsal crease may deepen along with narrow= ing of the palpebral fissure as a result of enophthalmos or fibrous tissue contraction. Although the palpebral fissure may in fact narrow, the geometr= ic shape is preserved since dehiscence or disruption of the canthal tendons is uncommon.
Treatment
Indications for repair of orbital blowout fractu= res include diplopia that persists beyond 7 to 10 days, obvious signs of entrap= ment, relative enophthalmos greater than 2mm, fracture that involves greater than= 50% of the orbital floor (most of these will lead to significant enophthalmos w= hen the edema resolves). The only urgent indication for repair is entrapment that causes an oculocardiac refl= ex with resultant bradycardia and cardiovascular instability.
The timing of repair is debated. Most agree that if operative intervention is not undertaken in the first 24 hours, it should be delayed = 10 days to let the edema resolve. Fracture repair should be undertaken prior to 14 days to prevent scarring of floor contents to the bone fragments and contents of the maxill= ary sinus.
A Metaanalysis was performed by Michael Burnstin= e in 2000 in which he reviewed the available literature to evaluate the best tim= ing for repair of floor fractures. The following were his recommendations: Immediate repair should be performed if (1) diplopia is present with= CT evidence of an entrapped muscle or periorbital tissue associated with nonresolving oculocardiac reflex: (2) bradycardia, heart block, nausea, vomiting, or syncope, or for “White-eyed blow-out fractures” in young patients (less than 18 years old), with a history of periocular traum= a, little ecchymosis or edema, marked extraocular motility vertical restrictio= n, and CT examination revealing an orbital floor fracture with entrapped muscl= e or perimuscular soft tissue, or (3)if there is early enophthalmos/hypoglobus causing facial asymmetry.
= Repair should be performed within 2 weeks for symptomatic diplopia w= ith positive forced ductions, evidence of an entrapped muscle or perimuscular s= oft tissue on CT examination, and minimal clinical improvement over time, or a large floor fracture causing latent enophthalmos or significant hypo-ophthalmos, or progressive infraorbital hypoesthesia. Observation was recommended for mi= nimal diplopia (not in primary or downgaze), good ocular motility, and no signifi= cant enophthalmos or hypo-ophthalmos.(1)
Multiple surgical approaches have been described= to gain access to the surgical floor. The three most common are the transconjunctival, subciliary, and subtarsal.
The transconjunctival approach allows for good a= ccess to the floor, gives no visible scars, and has a very low incidence of scler= al show or entropion. The disadv= antages are the potential for corneal abrasion and lack of exposure if a lateral canthotomy and cantholysis is not performed.
The subciliary incision is made just below the l= ash line and dissection is performed underneath the tarsus, dividing the obicul= aris muscle from the orbital septum and following the septum to the floor of the orbit. This gives good access= to the floor and gives camouflage to the scar. Several studies have shown a high incidence of scleral show and ectropion with this approach, and it is gener= ally agreed that this approach has the highest risk of these two complications.<= span style=3D'mso-spacerun:yes'>
The subtarsal approach is performed with an inci= sion right down to the orbital rim. It gives the best exposure but can be associated with a high rate of plate exposure and prolonged lid edema.
The transconjuctival approach is started with a lateral canthotomy and lysis of the inferior limb of the lateral canthal tendon. The incision is made through the conjunctiva and the fusion of the lower lid retractors and orbi= tal septum just below the tarsus. 5-0 silk sutures are used for traction to aid with dissection to the orbital rim. At the level of the arcus marginalis, the orbital septum fuses with = the periosteum. This is the point= at which the periosteum is opened with a 15 blade. Regardless of the approach, from t= his point the procedure is the same. Dissection is carefully done from this point with a malleable and an elevator. Care is taken to not retract the g= lobe or the optic nerve to forcefully as this can cause blindness. When the contents of the floor are removed from the maxillary sinus, support in the form of autogenous or synthetic plates are placed in the defect to prevent regress of contents in= to the maxillary sinus. Alternat= ively, a Foley type catheter can be placed through the maxillary antrum to support= the contents of the orbit until scarring occurs. All incisions are closed. Conjunctival incisions can be clos= ed with 6-0 Catgut or left open to heal on their own. Artificial tears and antibiotics a= re used in the post-operative period. Vision is tested in the recovery room and monitored over the next day. Any change in vision sho= uld be evaluated by an ophthalmologist.
Complications
Complications of repair are blindness, orbital h= ematoma, infection of hardware, migration of hardware, entropion, endophthalmos, and= diplopia. Orbital hematoma should be promptly treated with lateral cantholysis and canthotomy followed by evacuation of t= he hematoma in the operative suite. Blindness can be avoided by knowing well the anatomy of the orbit and taking care not to place implants deeper than 4 cm from the lacrimal crest = as the optic nerve is located in this area.
References
1) Clinical Recommendations for Repair of Isolated Orbital Floor Fractures, An Evidence-based Analysis, Michael A Burnstine, MD, Ophthalmology 2002; 109: 1207-1210.
2) Cummings: Otolaryngology Head and Neck Surgery 4th ed. Chapter 26, Maxillofacial Trauma, Robert M. Kellman, Mobsy, Inc. 2005.
3) Buckling and Hydraulic Mechanisms in orbital Blowout Fractures: Fact or Fiction?, Ahmad et al, Jou= rnal of Craniofacial surgery, vol 17, 438-441
4) The Effect of Striking Angle on the Buckling Mechanism in Blowout Fracture, Nag= asao et al, Journal of Plastic and Reconstructive Surgery, Vol 117, number 7, Ma= rch 05