Ординатура / Офтальмология / Английские материалы / Oculoplasty and Reconstructive Surgery Made Easy_Garg,Touky, Nasralla_2009
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Management of Orbital Trauma and Fractures 359
the motor nerves can be damaged by hemorrhage within their sheath, stretched by orbital edema or hemorrhage or suffer from concussion.
Radiologic studies are helpful in establishing the diagnosis. Waters plain X-ray views provide an excellent view of the orbital floor, showing any bone disruption or herniation. Orbit CT especially the coronal cuts delineates the fracture and the bone soft tissue relationship (Figures 7 and 8). However, the mere radiologic presence of a fracture is not an indication for surgical repair.
Figure 7: Left shows coronal CT scan with fracture floor and the tear drop appearance. There is a fluid level in the maxilla. Right shows a fractured mid floor with tissue herniation
Figure 8: A combined floor and medial wall fracture
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Management
Repair of the orbital floor fractures is mainly indicated in restricted ocular motility showing no improvement, diplopia especially within the central 30º field, enophthalmos of > 3 mm or progressive, defects of more than 50% of the orbital floor that are almost always likely to cause enophthalmos as well as incarcerated muscle causing oculocardiac reflex on ocular motility and rare cases of globe ptosis.
Timing
No universally agreed guidelines exist for the repair of blow out fracture. If in doubt, the patient should be evaluated every 2-3 days during the first 2 weeks, diplopia fields and forced ductions are followed carefully for any change. During this time, hemorrhage and edema will resolve during the first week allowing more accurate assessment. As long as motility improves, the patient should be followed up. On the other hand, if surgery is to be done, the best time is not beyond 2 weeks. After this, adhesions between bone fragments, sinus mucosa and the orbital tissues render the repair quite difficult.
Procedure
Surgical repair of blow-out fractures comprises good exposure through incision, periosteal dissection and exposure of the fracture, release of the entrapped tissues as placement of an implant to prevent adhesions between the orbital tissues and nasal mucosa. The surgeon can proceed from an orbital (subciliary or fornix) approach or an antral (CaldwellLuc) approach. The orbital approach is preferred as it is safer and more effective. In selected cases with large floor defects or with tenaciously herniated orbital contents, a combined orbital and antral approach can be used.
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Implants
Many materials are available for repair of orbital wall fractures. They include:
Autogenous bone
Cancellous bone grafts cannot be used due to high absorption rate, 60-80% of the volume may be lost. Split thickness calvarial or membranous bones such as ribs, iliac crest or the cranium have less absorption rate; 15-30%. This material needs a second surgical site with incidence of morbidity such as hematoma, infection. Harvesting them needs proper and formal training. The graft is usually placed with the cortical side towards the recipient bone and it may need to be secured by micro or minilpates.
Alloplastic material
a.Porous polyethylene: It is porous integrated biocompatible implant with average pore size 200-240 microns. It is easy to mold manually or the help of heat yet it is structurally stable
b.Silicone: A nonporous material that is easy to fashion, inert, safe and effective with low rate of migration, infection and extrusion. It is preferred in cases of orbital volume augmentation.
c.Methyl methacrylate polymer (cranioplastic): It is mixed with copolymer to form a mixture that have a doughy consistency and can be placed to augment orbital volume. This material remains malleable for 3-5 minutes so that it can be shaped. If it hardens before molding is complete, a pneumatic drill is used to fashion it.
It is better to be avoided in patients with chronic sinusitis due to the reported incidence of systemic toxicity and late infection.
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d.Microplates: They are used of there is no enough bone to support the implant. They are made of Titanium alloy. There are less corrosive than steel and produce less scatter on CT studies. They are not magnetic and can be safely imaged by MRI. They are used to reform the orbital rim, medial and lateral canthal angles as well as walls. The alloplastic implants are placed over them to augment the orbital volume.
e.Porous polyethylene implants with embedded titanium provide a new alternative to alloplastic implant materials for orbital reconstruction with a profile that combines several advantages of porous polyethylene and titanium implants.
f.Others like supramid and teflon.
g.Experimental work was done on bone morphogenetic protein (BMP) implant with and without platelet-rich plasma (PRP), which is supposed to promote fracture consolidation in the orbit fracture treatment with scarce inflammatory reaction, and may be a good alternative in orbit fracture reconstruction. Radiological studies suggested intramembranous and progressive cavitation and ossification without a reduction in implant size and with signs of calcium deposition; these events were confirmed by histological analysis.
Surgical Procedures
All are done under general anesthesia and forced duction test is performed initially to confirm the degree of tissue entrapment.
Incision
Variable incisions can be used to expose the inferior orbital rim as well as inferior part of the medial wall.
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a.Subciliary approach: It is similar to that used in lower lid transcutaneous blepharoplasty. The lid is infiltrated with 1% lidocaine with 1:100:000 epinephrine and a horizontal incision 2mm below the lid margin is made. It should not extend too far laterally to avoid compromise of lymphatic drainage. A skin muscle flap is created and retracted inferiorly using Desmarres retractor. This approach is more associated with postoperative lower lid malpositions namely ectropion.
b.Lower transconjunctival approach: The inferior fornix is incised 4 mm below the lower edge of the tarsus. Lateral canthotomy and inferior cantholysis can be done to widen the exposed field. The conjunctiva, Müller‘s muscle and the capsulopalpebral fascia are severed and the plane between the orbicularis and the capsulopalpebral head is reached. Tissues are dissected till the inferior orbital rim is reached. A 4-0 silk tractional suture is passed through conjunctiva and lower lid retractors. This approach is preferred as it is simple, provides excellent exposure with no visible scar and it has minimal risk for post operative lid malpositions. However, there is a rare risk of entropion due to scarred posterior lamina.
c.Antral (Caldwell-Luc) approach: An incision is made in the gingival margin of the canine fossa. Periostium is elevated and separated from the anterior surface of the exposed maxilla. A periosteal elevator is used to create an osteotomy opening into the maxillary sinus. Bone fragments and blood are then evacuated from the sinus. In conjunction with orbital approach, the herniated tissues are gently reposited superior to the orbital floor. The maxillary sinus may then be packed with either petroleum gauze imbricated with antibiotic or a catheter balloon.
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The other end of the gauze or catheter is brought out through an antrostomy to facilitate its removal. This approach has limited visualization, poor access for placement and securing the floor implant, poor hemostasis, higher infection rate, lack of permanent glob support and hazards of forcing bony fragments into the globe and optic nerve. That is why this approach is seldom used for fracture floor repair unless there is complete absence of orbital floor.
Exposure of the Orbital Floor
Dissection is carried out till the inferior orbital rim using blunt and sharp dissection keeping the orbital septum intact to avoid fat herniation. Then the periostium is opened 1.5 mm below the orbital rim and elevated from the orbital floor. With the help of periosteal elevator, the periostium is separated from the floor posteriorly; the fracture is localized and exposed, first the lateral border then the medial and posterior limits. The infraorbital bundle should be identified. Any unattached bone fragments should be removed.
Incarcerated tissues are freed from the fracture using hand on hand maneuver with the periosteal elevator and the metal suction tip or malleable retractors. This is easy in cases of recent fractures yet if the tissues are swollen, the extraction becomes difficult and the bone can be depressed into the maxillary antrum. In case of hinged fractures or in some selected cases, the fracture may be enlarged to achieve atraumatic release. Care should be taken to avoid undue bleeding and trauma to the nearby optic nerve.
Optic nerve should be checked every now and then by detecting the pupillary light reaction or dilating the pupil and noting the optic nerve perfusion by the ophthalmoscope.
Forced duction should be repeated to ensure that no more incarcerated tissues are present. Any bone fragments or blood
Management of Orbital Trauma and Fractures 365
should be aspirated from the maxillary antrum before the defect is covered.
A sterile alloplastic material is fashioned to cover the defect completely and overlapping the surrounding intact bone by 3-4 mm circumferentially. This sheet should not be too large or too thick. The edges are smoothened to avoid trauma to adjacent structures or erosion through the covering periostium. The alloplastic material should be soaked in antibiotic before it is inserted. The thickness of the plate usually range from 0.4-0.6 mm. Thicker implants are indicated in cases of significant enophthalmos and hypophthalmos yet they have the risk of limiting extraocular muscles. The more posterior the implant is placed, the more it reduces enophthalmos. The more anterior it is, the more it reduced hypophthalmos. The choice of the material depend on the nature of the fracture as well as the surgeon preference and training.
When the defect is large or multiple walls are involved, plates and screws are preferred; bone grafts may be a good choice in experienced hands. Titanium mesh may be used if the residual bone is not enough to support an implant. It is not enough by itself and it usually needs to be covered by bone or alloplastic material.
The implant can be fixated by either placing it behind the orbital rim and the mere periosteal closure will keep it in place or two small fixation holes are drilled in the infraoprbital rim just anterior to the defect as well as the anterior edge of the implant. Then the implant is secured to the orbital floor anteriorly by supramid 2-0 sutures.
Forced duction test is repeated. Coexistent medial wall fracturecanberepairedatthesametime.Hemostasisissecured and the periostium is closed over the implant. Lateral canthus is repaired in case of cantholysis and canthotomy. The opened layers are then closed anatomically.
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Eye patch is better avoided and the patient should be watched for bleeding, pupillary reaction and visual acuity postoperatively. Systemic antibiotics, anti-inflammatory drugs as well as cold foments are proven useful.
Complications
Diplopia may persist or worsen after the surgery. This can occur due to fibrosis of the muscle, orbital fat or connective tissue septa either present prior to surgery or secondary to inflammation induced by the surgery. It can be due to unidentified nerve injury before surgery. Diplopia may worsen due to improperly placed implant or residual tissue entrapment. A muscle procedure is better deferred 6-12 months after surgery during which the diplopia may improve or the patient can wear prisms. If a surgery is to be done it is better to be with adjustable sutures.
Overcorrection may occur due to thick implant augmented by postoperative edema that usually resolves after a month. On the other hand residual enophthalmos may be present due to inadequate restoration of orbital volume, bone graft absorption, migrating implant or orbital fat atrophy. It can be mild requiring no further intervention. In some cases, minimal ipsilateral upper lid elevation using Fasenella Servat procedure or contralateral upper lid blepharoplasty to deepen the superior sulcus can be enough to camouflage the appearance. In more extensive cases, the implant may be exchanged for a thicker one.
The orbital implant may become infected. It may be oversized and extruding. In both conditions the implant should be removed and replaced with a proper sized one. If fibrous tissue sufficient to cover the defect has formed since the original surgery, the implant may not require any
Management of Orbital Trauma and Fractures 367
replacement. Chronic lid swelling with superior globe displacement may indicate the presence of a fluid filled cyst formed around the implant. The implant should be removed and the cyst excised.
Ectropion, lower lid retraction or chronic edema may result when the skin approach is used. Retraction can occur due to adhesions between the orbital septum and the inferior orbital rim. This can be corrected by recessing the lower lid retractors.
Persistent infraorbital nerve anesthesia may occur. It may be injured or just compressed by the implant. If the nerve is not cut, function usually returns within 1 year. Sometimes the implant can be exchanged with widening the foramen decompressing the nerve. In some cases, the patient may get tolerant to the numbness in this area.
Blindness may occur in 1: 1500 cases. It can be secondary to compression of the optic nerve by the implant, orbital edema or hemorrhage. This can be prevented by avoiding undue pressure on the globe during surgery, continuous optic nerve monitoring, screening patients for clotting abnormalities preoperatively, using intra and post operative steroids, complete hemostasis before wound closure, avoiding compressive ocular dressing postoperatively and continuous monitoring of the pupil and visual acuity.
It should be remembered that the optic nerve may be damaged from the original injury with delayed visual loss from edema and vascular occlusion and may appear coincidently with surgery and mistakenly blamed on the surgical procedure.
Naso-orbital and Medial Orbital Wall Fractures
These fractures result from a force delivered to the nasal bridge or medial orbital rim. These are the weakest in the midface
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bones and usually injured by the dashboard in cases of automobile accidents. They are commonly associated with fracture floor and contribute to the presenting enophthalmos.
In mild cases, the injury is limited to the nasal bone and the frontal process of the maxilla. In more severe cases, the lacrimal and ethmoid bones (Figure 9) may crack and splay laterally causing traumatic telecanthus, flattening and widening of the midface, rounding of the medial canthus, epistaxis, periorbital ecchymosis, subcutaneous emphysema (if the ethmoid is fractured), with bony nasolacrimal duct injury causing epiphora. The medial rectus is rarely entrapped in the fracture with less common horizontal gaze limitation.
CSF rhinorrhea suggests a cribriform plate fracture. Most of cases are managed conservatively. The patient is treated by bed rest, intravenous antibiotics and instructed not to blow the nose or smoke. If the condition persists, neurosurgical interference is required.
Hemorrhage may be severe if the anterior and or posterior ethmoidal arteries are injured. The bleeding usually stops promptly. However, nasal packing or direct ligation may be required. Any coexistent upper airway obstruction should be relieved.
Figure 9: Medial wall fracture