Blindness as a complication of Le Fort osteotomies: role of atypical fracture patterns and distortion of the optic canal.

Abstract

Blindness in patients suffering maxillofacial trauma is usually caused by optic nerve or optic canal injuries. It is, however, an uncommon complication of facial trauma, with a reported incidence of only 3 to 5 percent. This incidence drops dramatically when fractures are performed in the controlled situation of orthognathic surgery. Given the rarity of ophthalmic complications after traumatic Le Fort I injuries, it is not surprising that few cases have been reported after orthognathic surgery. In this article, three cases of visual loss or skull base injury after elective Le Fort I osteotomy are described. All of these cases were presumably straightforward surgically and were performed by experienced surgeons. The literature is reviewed and the pathomechanics of each injury are experimentally explored in a cadaver model. To determine the presence of increased pressure on the optic nerve, optic canal deformation, or fractures extending to the skull base, two separate experiments were devised. In the first experiment, a pressure transduction system was used to document any significant forces that may be directly transmitted to the contents of the optic canal during pterygomaxillary separation. Then tested was the hypothesis that a stepped or tapered osteotomy will allow for a more predictable pterygomaxillary fracture. One of five cadaver specimens in group 1 demonstrated a transient increase in the right optic canal pressure during down-fracture of the maxilla. This change was less than 10 mmHg, and its duration was less than 5 seconds. The canal pressure returned to baseline with the completion of the fracture. In group 2, there was no documented pressure change with either osteotomy technique. Of note, in group 2, all specimens undergoing standard Le Fort osteotomy demonstrated uncontrolled propagation of the fracture lines superiorly in the pterygoid bones. The uncontrolled and unpredictable nature of pterygomaxillary disjunction may result in the extension of fractures to the skull base or the generation of deforming forces to the optic canal may compress or injure the optic nerve and its circulation. It is proposed that a stepped or tapered osteotomy will generate a more controlled pterygomaxillary separation during orthognathic surgery and may reduce the risk of devastating ophthalmologic complications.