[An unusual form of isolated fracture of the orbital floor: "valve fracture". Therapeutic problems].

Among isolated fractures of the orbital floor, the authors are pointing out an unusual clinical type characterized by the irreducibility of the orbital contents ruptured in the maxillary sinus by using classical procedures. This primary failure is due to a bone fragment dropped in the sinus and being attracted by the herniated collar when trying to integrate the hernia in the orbit. To name this type of lesion, the word "valve fracture" is proposed because of the analogy of the one way function of a valve and its different mechanism from the classical trapdoor fracture. The different concepts of the pathogenesis of isolated fractures of the orbital floor and the physiopathology of the frequently associated ocular disturbances are briefly exposed. The authors report the case which confronted them to the valve fracture. Following a direct trauma to the right orbital area a 13-year-old child presented a limitation of the upwards movements of the right eye with diplopia and a positive forced duction test. The surgical exploration shows an orbital hernia in the sinus which is impossible to reposition either with a higher incision (under the orbital rim) or with a lever incision, upper vestibular incision (through maxillary sinus). Only the infraorbital marginotomy described by P. Tessier exposes completely the lesions and allows understanding of the mechanism of this primary irreducibility related to the valve movement of the fractured bone fragment. Above all, marginotomy allows an atraumatic set. If is performed combining gentle handles of pulling and forcing back on the ruptured pieces while keeping opened the valve.