The Subtype Classification Of Medial-inferior Orbital Wall Blowout Fractures According To Computed Tomography

Diplopia and enophthalmos are the most common characteristics of the orbital fractures patients. To date, these patients were diagnosed and treated mostly by doctors working in the maxillofacial surgery, plastic surgery and otolaryngology departments and therefore the classifications of the orbital fractures were formed on the basis of viewpoints hold by these non-ophthalmologists. So there were few detailed, systemic and directed clinical data to evaluate extraocular muscle function changes after orbital blowout fractures from the view of ophthalmologists. In this paper along with our new subtype classification system introduced, the relationship between the location as well as morphology of the fractures and extraocular muscle function changes for medial-inferior orbital blowout fracture patients were studied and discussed which couldprovide more opinions for surgical method choice and observing patients prognosis.From March of 2002 to March of 2005, 52 patients (41 males and 11females) were diagnosed as medial-inferior orbital wall blowout fractures. Age ranged from 10 to 51 years old. The mean delay time between the day of injury and coming to hospital was 4.1 days (range, 1day to 7 months). Hertel exophthalmometry was used for measurement of enophthalmos and extraouclar muscle functions was investigated by candle double vision test and synoptophore. All the patients were evaluated by axial and coronal computed tomography scans, and when it was necessary three-dimension CT reconstruction to confirm the clinical diagnosis.Medial-inferior orbital walls blowout fractures were classified to the 2 subtypes respectively according to measuring the fracture area by software package(Analyze((R)); Mayo Clinic, Rochester, MN, USA). Type IM-M was defined as that the medial wall fracture area was larger than that of inferior wall. Type IM-I was defined as that the inferior wall fracture area was larger than that of medial wall.All data were analyzed statistically by SPSS bag 11.3.Major symptoms of Orbital blowout fracture patients are diplopia(37,71.2%)and enophthalmos(43,82.7%).There were 15 persons with enophthalmos(mean difference between 2 eyes 2.61±0.78 mm)and 13 persons with diplopia in 22 type IM-M patients. Among 30 type IM-I patients there were 28 enophthalmos (mean difference between 2 eyes 3.66±0.93mm) and persons with 24 diplopia. The incidence and severity of enophthalmos in type IM-I were higher than that in type IM-M(Z=5.61, P<0.05;t=3.725, P<0.05) and the incidence of having diplopia had no significant difference between the two subtypes(Z=2.703, P>0.05). In cases of type IM-M, the restrictions of medial rectus muscle were more frequently seen(14/20) phenomenon, by contrast, in type IM-I, the most dominant phenomenon of extraocular muscle dysfunctions were the restriction of inferior rectus muscle(20/30). The incidences of medial rectus muscle and inferior rectus muscle simultaneously being involved in the two subtypes had no statistical difference(5/22, 8/30, X2=0.105,P=0.746), and so were the incidences of single extraocular muscle being involved in the two subtypes(6/22,11/30,X2=0.509,P=0.476). In type IM-M,the most common functional impairment of inferior rectus muscle was the restriction ofit(6/22), and in type IM-I, the occurrence of the restriction of medial rectus muscle was 6/30, which was the highest ratio of dysfunction of medial rectus muscle.There were only 3/22 and 4/30 cases of the paralysis of the inferior oblique muscle in the two subtypes, and CT characteristics of these cases was the facture of the angle acrossing the medial and inferior orbital walls.With the above studies and analysis, the following conclusions were shown bellow:The incidence and severity of enophthalmos had a close relationship with the subtype classification of complexed medial inferior orbital walls blowout fractures. And the each subtype had a obvious characteristics of the extraocular muscle dysfunction repectively. Therefore, the subtype classification of complexed medial inferior orbital walls blowout fractures is a marvelous and significant research to the orbital blowout fractures , and it also has instructive and practical value for the clinical treatment.