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Fracture of the orbital floor (57.4%) can occur from zygomatico-maxillary complex fracture in middle third facial skeletal injuries. However, isolated orbital floor fracture-the term coined as ‘blow out fracture’ represents upto 21.4% . Anatomically, the antero-medial 3rd of the floor is formed by orbital surface of maxilla, where as the postero-medial part is formed by palatine bone and lateral 3rd is formed by zygoma. The medial wall of the orbit is formed anterior to posterior, by frontal process of the maxilla behind its lacrimal crest, lacrimal bone, orbital plate of ethmoid and body of sphenoid. The ‘blow out’ fracture of orbit usually involves the medial wall and floor of the orbit being the thinnest. Absolute indications for reconstruction of orbital floor are diplopia with muscle entrapment, enopthalmos and large defect . Many materials have been described for the reconstruction of orbital floor defects with varying rate of success. They include autogenic, allogenic and alloplastic material.
This article reports management of a case of orbital blow-out fracture using autogenous iliac crest bone graft to reconstruct the defect of the orbital floor.
This 14 year old boy reported with the complaints of double vision developed subsequent to a road traffic accident (RTA). There was subconjunctival ecchymosis and mild degree of enopthalmos of right eye with lowering of interpupillary line. The ocular movement was restricted in upward direction and had diplopia in medial, upward, downward and lateral gazes (Fig 1). Force duction test was positive. However the pupillary, corneal and conjunctival reflexes were normal and no paraesthesia over right infraorbital region was detected. Water's projection of skull showed classical ‘hanging drop’ sign at the roof of the maxillary antrum. Axial view CT scan of skull revealed breach in the floor of the right orbit alongwith herniation of periorbital soft tissue into the antrum (Fig 2). The diagnosis of “blow out fracture - right orbit” was established.
The orbital floor was approached through subcilliary incision under nasoendotracheal general anaesthesia. The infraorbital nerve was identified and protected. The herniated periorbital content including inferior rectus muscle and fat was disengaged from the bony defect. From the inner table of right iliac crest a small bone piece was harvested which was shaped to match the contour and size of the defect of the orbital floor. The graft was placed over the defect and fixed with titanium microscrew. The incision was sutured with 5-0 proline. Post-operative recovery was uneventful. Immediate improvement of diplopia, position of the globe, interpupillary level and movement of the eye in upward gaze was noticed. Patient had mild degree of diplopia on medical gaze. The patient was reviewed at regular intervals, initially once every week for two months, followed by every two weeks for three months and subsequently once in every month postoperatively. On his last 6th monthly visit the patient did not have any diplopia in any gaze (Fig 3). The post-operative radiograph showed well established graft in place (Fig 4).
The etiology of the blow out fracture of the orbit is controversial, though the concept of transmission of hydraulic force against the orbital wall to cause fracture is widely accepted . Anatomically the inclined plane of the orbital floor which is also the thinnest, helps the resultant force vector to travel in downward and medial direction. However, in practice the orbital floor undergoes fracture in posteromedial part since the tubular architecture of the canal provides some mechanical strength to the floor. The outcome of this type of fracture depends upon proper diagnosis, timing of surgery, appropriate surgical approach and selection of suitable graft material.
There are varied opinions regarding the indication of repair of orbital floor. According to some authors, diplopia alone is not an indication for surgical repair . A few workers opine that if the Lockwood's suspensory ligament is intact there is no substantive reason to reconstruct the orbital floor . Some authors suggest that the reconstruction may be dispensed if the defect is less than 0.5 cm. Therefore, to ascertain the location and extent of the defect proper investigations viz X-rays, CT are mandatory. In our case, coronal view CT scan and PNS view X-rays were carried out to plan the surgery. The timing of surgery is also not undisputed. Some authors suggest that surgical exploration can be obviated in case of diplopia which resolves within 14 days unless extensive bony wall defect is detected . Another school advocates waiting period of 4-6 months prior to undertaking surgical exploration while others recommend early surgical intervention . We preferred early surgical intervention because the defect was large as well as the Force duction test was positive, which denoted definite entrapment of the peri-orbital content, indicating fibrosis, though some workers achieved good result performing surgery even after 4-6 weeks of injury.
The commonly used surgical approaches to reconstruct the floor of the orbit are transconjunctival, subciliary and infraorbital. However, considering the exposure required and aesthetics, we preferred the subciliary type of approach.
The basic objective of reconstruction of orbital defect is to restore orbital volume, function and aesthetics[5, 7]. To reconstruct the defect of the orbital floor, various autogenous as well as allogenic and alloplastic material have been used with their merits and demerits. In the present case, autogenous iliac cortical bone graft was used to repair the defect as it maintains the volume better in comparison to the cancellous one irrespective of their origin and there is least chance of contamination of the graft. In the present case, the autogenous iliac crest cortical bone graft served the basic goal of reconstruction of the orbital defect satisfactorily.