Orbital fractures



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ORBITAL FRACTURES




HISTORY





      • William Lang 1899 first isolated orbital blowout fracture

      • Converse and Smith 1957 coined the term “blow-out”

      • Pfeiffer 120 cases 1945 where 24 instances enophthalmos and 24 cases “internal orbital fracture” without rim fracture



ANATOMY





  • Seven bones frontal bone, maxilla, zygoma, ethmoid, lacrimal bone, greater and lesser wings of the sphenoid, and the palatine bone

  1. Roof

  2. Lateral

    • Zygoma

    • Greater wing of sphenoid

  3. Floor

    • Zygoma

    • Orbital surface of Maxilla

    • Orbital process of palatine

  4. Medial

    • Anterior lacrimal crest on frontal process of maxilla Maxill

    • Lacrimal

    • Ethmoid

    • body of sphenoid leading to optic canal

  • 4-5cm depth, volume = 30mls

Ligamentous supports of the globe



  • comprises the medial and lateral check ligaments, the medial and lateral canthal ligaments, an inferior sling, and a superior sling.

  • Inferior sling includes not only Lockwood’s ligament and extensions, but also the fascial condensations around the inferior rectus muscle and Tenon’s capsule

  • Superior sling is composed of Whitnall’s ligament, condensations of the levator and superior rectus fascia, and Tenon’s capsule.

Musculofibrous Ligaments of Koornneef

  • Koornneef makes particular note of the intricate network of connective tissue septae within the orbital fat space. This connective tissue has also been shown to contain an abundance of collagen fibers, smooth muscle cells, and fibroblasts.

  • The fat, both within the muscle cone and extraconal, is diffusely interconnected by fine ligaments to the periosteum lining the bony orbital walls, to each of the extraocular muscles, and to the bulbar fascia.

  • These are more prominent in the inferior medial orbit. The connective tissue septae have an intimate relationship with the so-called check ligaments and suspensory ligament of Lockwood.

  • These structures are both supportive and, in part, serve to limit eye movement.

  • Whereas arterioles branch radially within discrete adipose pockets, veins (which course along fibrous septa) have diffuse anastomoses and are abundantly interconnected with extraorbital veins by branches perforating the orbital walls. Venous drainage of the orbit follows a central to peripheral flow pattern.


Fracture patterns

  • Isolated roof fractures rare in adults because of the protection afforded by the supraorbital rim, frontal bone, and frontal sinus.

  • Frequencies of pure blow out fractures (Burn PRS 1999)

  1. Medial wall – 55%

  2. Inferior – 33%

  3. Medial and Inferior – 27%

  • Inferior wall and medial wall most vulnerable

    • Inferior wall - thinness of the maxillary roof, Presence of the infraorbital canal and Curvature of the floor

    • Medial wall - thin lamina papyracea of the ethmoid

  • Lateral wall is strong- least common isolated injury, but always involved in fractures of the zygomatic complex

  • Children have different patterns

    • Due to lack of sinuses, fractures are less likely

    • more likely isolated roof fractures up to 7 years, then floor more likely

Look for associated injuries



      1. Ocular injury

        • Fluorescein for cornea

        • Anterior chamber for blood/hyphaema

        • limbus for signs of laceration (teardrop sign) or deformity

        • funduscopic exam to check for blood in the posterior chamber, and examine retina for signs of detachment

      2. nasal fractures most common

      3. Examine nasal septum

      4. mandibular fractures

BLOWOUT FRACTURES



Mechanism

  • Two mechanisms have been proposed to explain fractures of the orbital floor.

  1. soft tissue transmission - increase in hydraulic pressure resulted from direct trauma to the ocular globe.

  2. bony transmission - maintains that the force delivered to the rim is transmitted along the bone to the floor, thereby causing the fracture

CLINICAL SIGNS AND SYMPTOMS



Diplopia (25-60%)

  • most common in upward gaze

  • caused by restricted ocular movement

  • primary or secondary gaze

  • mechanical or non-mechanical causes

  • Mechanical

  1. entrapment of extraocular muscles, Lockwood’s ligament, Tenon’s capsule, intermuscular membrane, or periorbital fat

    • entrapment has been described with medial rectus in medial wall fracture.

  2. relative change in the effective origin and insertion of the inferior rectus muscle.

  3. entrapment to the fine connective tissue system described by Koornneef.




  • Non Mechanical (less common)

    1. injury to one or more extraocular muscles

    2. fibrosis of the fibrous connective tissue - increased scar tissue and adhesions between the fracture site and the infraorbital muscle sheaths restricts muscle motion

    3. blunt injury to divisions of the third, fourth, and sixth cranial nerves

    4. interruption of circulation to critical muscle areas.

    5. haematoma

    6. oedema

      • Assess with Hess Charts, binocular vision and field, forced duction, radiography and sometimes coronal computed tomography.

      • forced duction test is unreliable during the first week after injury because nonmechanical causes of restriction often give spurious results.

      • Important to test in 1 weeks time if conservative Mx is chosen

      • 73% will have resolution of diplopia with conservative management


Entrapment in children

      • White-eyed blowout fracture

      • Children may be more prone to pure trap door fractures (60% of floor fractures) than adults and incarceration of the muscle in such fractures can lead to permanent damage of the neuromuscular complex.

      • Presents with marked motility restriction and nausea/vomiting

      • Several studies have demonstrated more complete resolution of diplopia if these cases are operated on very early or as soon as the diagnosis is made - best results within 2 days (Jo Gruss), opthamol journals say 1 week.




      • Pathophysiology

        • In children, the flexible orbital floor fractures and is displaced inferiorly, allowing infraorbital tissue to enter the fracture site.

        • The trapdoor then recoils, trapping the inferior rectus.

        • Consequently, the ophthalmic division of the trigeminal nerve is stimulated and, through the reticular formation, transmits the signal to the vagus nerve, which then carries the efferent impulse to the stomach, producing nausea.

        • Nausea and vomiting have a 83% PPV.

        • With entrapment, a compartment syndrome of the inferior rectus may result.

        • Small orbital floor fractures were more likely to have high compartment pressures around the inferior rectus and that diplopia was more likely to persist.

        • The resultant ischemia and inflammation may lead to permanent fibrosis and impaired extraocular motility.

      • Treatment

        • Transconjuctival approach

        • soft-tissue dissection and reduction was much more difficult in the patients whose surgery had been delayed.

        • In most patients, the trapdoor needed to be depressed to release the valve effect on the soft tissues

        • simple reduction of the soft tissue was noted to predispose to recurrent herniation of the soft tissue into the fracture. To prevent a postoperative herniation and entrapment, the fractured orbital floor was patched - pericranial shave graft best



Enophthalmos (28-65%)

Aetiology

  1. enlargement of the bony cavity

  2. amount of periorbital fat

  3. status of the check ligaments arising from the sheath of the lateral and medial rectus muscles

  4. tone of the rectus muscles, which exert slightly more pull posteriorly than the oblique muscles do anteriorly.

  5. soft-tissue scarring and contracture pulling the globe backward

Pathophysiology

  • even when the orbital floor is completely absent, Lockwood’s ligament will support the eye as long as its anchoring points— to Whitnall’s tubercle of the zygoma laterally and to the lacrimal crest medially

  • Pearl described a coronal plane from the lateral orbital rim to the anterior lacrimal crest (divides the globe into 2 equal halves)

  • Fat loss anterior to the axis of the globe does not affect the anteroposterior location of the eye itself.

  • Only fractures located posterior to the axis produce enophthalmos,

  • Only operative procedures that create bony enlargement and fatty displacement behind this axis correct exophthalmos.

  • Only adding volume behind the axis of the globe can correct enophthamos.

  • If there is sufficient space between the top of the globe and the bony roof, volume additions at the axis of the globe can correct vertical dystopia without producing exophthalmos.

  • the severity of the enophthalmos is a measure of the difference between the anterior corneal surface and the lateral orbital rim

  • Manson noted that enophthalmos occurs when orbital floor disruption exceeds a total area of 2 cm2, the bone volume change exceeds 1.5 cc (5% of orbital volume), and significant fat and soft-tissue displacements occur.

  • Enophthalmos of 2.5 to 3 mm correlated with a mean increase in orbital volume of 3.4 mL (10%), while enophthalmos of 3.5 to 5 mm correlated with increase in orbital volume of 7.1 mL.(20%)

  • Parsons and Mathog reported that surgical exploration to prevent enophthalmos is indicated for all orbital blowout fractures with 3 mm of displacement of either the inferior or medial wall.



Classification

Mild <3cm

Moderate 3-4cm

Severe >4 cm


Clinical

  • Hertel exophthalmometer > 2mm 10-14 days after trauma is cosmetically significant and is an indication for surgery.

  • Orbital edema that is present initially may mask any enophthalmos. Therefore, measurements must be rechecked once the orbital edema has subsided. This usually occurs 10 days to 2 weeks after injury.


Displacement of the medial and lateral canthal ligaments

    • inferior displacement and antimongoloid slant of the fissure with lateral canthal tendon displacement

    • If the lateral end cannot be found, the tendon should be sutured to the periorbita or through holes drilled through the lateral orbital rim at the orbital tubercle. It is important to remember that the lateral canthal tendon attaches to the orbital tubercle located 5mm posterior to the lateral orbital rim at level of the upper limbus. If not repaired correctly, the lateral canthal angle will be displaced too far anteriorly.

    • telecanthus with medial canthal detachment

    • If no soft tissue remains or the medial orbital wall is fractured, the tendon can be wired to the adjacent intact medial wall, transnasally to the contralateral medial orbital wall, or to the contralateral medial canthal tendon.


Pseudoptosis

  • deepening of the supratarsal fold occur due to posterior displacement of the globe.

  • distinguished from true ptosis by the fact that there is no change in the distance between the inferior lid margin and the pupil;


Hypoanesthesia of the infraorbital nerve
Maxillary sinusitis(2%).
Orbital emphysema

  • seen usually with medial wall fractures

  • intraorbital air mass can cause central retinal artery occlusion – treat with CT guided needle aspiration of the air mass if accompanied by visual deterioration, rising intraocular pressure, severe pain, or motility disturbances.


Ocular injuries

  • hyphema, corneal rupture

  • retrobulbar and vitreous haemorrhage

  • retinal detachment, glaucoma, angle recession, retinal tear, traumatic cataract, subluxation or globe rupture

  • Marcus Gunn pupil - unilateral lesion in the afferent visual pathway anterior to the chiasm. Consensual response present but not direct.

  • Visual loss - Most commonly from
  1. Traumatic optic neuropathy - most common mechanisms are haemorrhage into the optic-nerve sheath secondary to a shear effect, or contusion of the nerve with associated oedema and compression.

  2. Globe rupture

  • Review of 2516 facial fractures by D. David found 13% incidence of ocular complication. Incidence of blindness 0.8%

  • Other studies show when rupture of the globe is excluded, the incidence of blindness associated with orbital fractures is reported to be 2% to 2.4%.

  • Review of 5936 pts - 2.2% after Lefort III, 0.64% after lefort II, 0.45% after zygomatic fractures


  • Ocular injury more common with orbitozygomatic fractures compared to blowout fractures

  • Most agree that patients who lose their sight at the moment of injury are not likely to recover it.

  • Megadose steroids recommended - initial intravenous loading dose of 30 mg/kg of methylprednisolone, followed in 2 hrs by 15 mg/kg every 6 hours.





RADIOGRAPHIC EVALUATION

  1. Plain xrays

    1. Waters view or occipitomental projection

      1. taken at an angle 37° caudal to the canthomeatal line.

      2. optimally visualizes the superior and inferior orbital rims, nasal bones, zygoma, and maxilla.

    2. Caldwell view, angled 15° caudal to the canthomeatal line

      1. allows additional views of the frontal sinus and superior orbital rim. Provides the best view of the lateral orbital rim and ethmoid bone.

    3. Hanging drop sign

    4. Blood in antrum

  2. CT scan

    1. gold standard fine cut with reconstructions

    2. rounding of the inferior rectus muscle in cross-section is indicative of an injury to the floor secondary to edema and damage within the muscle itself

  3. MRI scans

  4. Orbital U/S (accuracy depends on the expertise of the ultrasonographer)



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