Influence of Fractures in Different Inferior Orbital Wall Locations on Ocular Motility Disorders
Orbital floor fractures are a significant cause of ocular motility disorders, yet the underlying mechanisms remain poorly understood. This study aimed to clinically characterize fractures in different locations of the inferior orbital wall and to determine the relationship between the type of fracture and the resulting ocular motility disorder. The research was conducted retrospectively, analyzing patients who presented with ocular motility disorders due to orbital floor fractures within seven days of trauma. The study was approved by the ethics committee, and informed consent was waived due to its retrospective nature.
The inclusion criteria for the study were patients aged 12 years or older who could clearly describe diplopia symptoms and cooperate in the forced duction test (FDT). Additionally, all patients had a confirmed diagnosis of inferior orbital wall fracture via computed tomography (CT) scanning. Exclusion criteria included concurrent ocular rupture or severe vision loss, another concurrent orbital wall fracture, or a history of ocular trauma. Routine eye examinations were conducted, including uncorrected and best-corrected visual acuity tests, slit-lamp examination, and ocular fundus and intraocular pressure (IOP) measurements. Ocular motor examinations included ductions and versions, assessed by the same examiner. The FDT was used to assess restrictive and paralytic eye movement disorders, with a positive FDT indicating entrapment of the inferior rectus or inferior rectus and inferior oblique muscles in the fracture area. A negative FDT suggested superior rectus paralysis or muscle injury. The Hess screen test was performed on all patients, and diplopia testing was conducted to assess the damaged muscle and the nature of the diplopia. Axial dystopia (enophthalmos or exophthalmos) was determined using a Hertel/Krahn exophthalmometer. All patients underwent 64-slice spiral CT scanning in horizontal, coronal, and sagittal planes, with images reconstructed using bone and soft-tissue algorithms.
The study included 32 patients, comprising 26 males and six females, with an average age of 29 years (range: 13–55 years). All patients had corrected visual acuity greater than 0.3 logarithm of the minimum angle of resolution (logMAR), clear refractive systems, normal ocular fundus, and normal IOP. The fractures were caused by car accidents (14 cases), violent striking (13 cases), and other causes (5 cases). The patients were categorized based on the location of the fracture: anterior segment fractures (5 cases), posterior segment fractures (6 cases), and combined anterior and posterior segment fractures (21 cases).
In the five cases with anterior segment fractures, CT scans showed anterior orbital floor fractures with intact posterior segments and incarceration of the inferior rectus muscle or surrounding soft tissue. Ocular motor examinations revealed obvious restriction on supraduction and slight restriction on infraduction. A positive FDT indicated impeded passive upward displacement of the eyeball, with normal downward motility. The Hess screen test showed obvious contraction at the top graph and slight contraction at the bottom graph. All patients in this group exhibited restrictive ocular motility disorders, with four (80.0%) showing limited upward movement and one (20.0%) showing limited vertical movement. All patients had upward gazing deficiency.
In the six cases with posterior segment fractures, CT scans showed posterior orbital floor fractures with intact anterior segments and partial trapping of orbital contents in the fracture orifice. The ocular motility disorder in these cases was paralytic. Positive FDT results were obtained in vertical movements, with all six (100%) patients showing limited downward movements. There was no obvious restriction on supraduction and infraduction. Five (83.3%) cases had downward gazing deficiency. The Hess screen test showed obvious contraction at the bottom graphs.
In the 21 cases with combined anterior and posterior segment fractures, CT scans showed large collapsed areas of the orbital floor and substantial amounts of orbital contents trapped. Among these patients, three had restrictive ocular motility disorders, four had paralytic disorders, and 14 had combined restrictive and paralytic disorders. Ocular motor examinations showed obvious restriction on both supraduction and infraduction. Most cases exhibited enophthalmos (18 cases), hypesthesia of the trigeminal nerve region (16 cases), subconjunctival hemorrhage (16 cases), and periorbital ecchymosis (17 cases). Detailed data for all groups are provided in Table 1.
The study demonstrated that fractures in different locations of the inferior orbital wall cause distinct types of ocular motility disorders. Anterior segment fractures primarily involve restrictive eye movement disorders, characterized by fractures between the orbital rim and the junction between the inferior orbital sulcus and the inferior orbital margin. The tilted end of the fracture plate is located in the maxillary sinus, while the other end is connected to the orbital wall, resulting in the clamping of the lower rectus sheath or surrounding soft tissues. The inferior rectus muscle has abundant adipose tissue between this site and the orbital floor, providing some protection and resulting in less direct muscle injury during trauma. However, muscle sheath or surrounding soft tissue incarceration can lead to limited movement of the extraocular muscles, even after surgical reconstruction of the orbital wall. This limitation may be due to ischemia, fibrosis, and contraction following the incarceration of the extraocular muscles, necessitating further surgical treatment if required.
Posterior orbital floor fractures primarily involve paralytic factors, with fractures located in the suborbital groove where the suborbital fissure meets the orbital apex. These fractures often involve large-area collapsed fractures of the orbital floor between the inferior orbital fissure and the ethmoid maxillary suture, with orbital contents partially emptied into the maxillary sinus cavity. The oculomotor nerve branches into the lower rectus muscle site, and the muscle itself may show contusion, leading to ophthalmoplegia and affecting eye performance. The lower part of the inferior orbital wall has less adipose tissue between the inferior rectus muscle and the orbital floor, making the muscle more susceptible to direct contusion and subsequent paralysis during trauma. The large extent of fractures and possible incarceration of orbital contents, including the inferior rectus muscle and surrounding soft tissues, contribute to the characteristic paralytic disorder in these cases.
Combined anterior and posterior segment fractures involve both restrictive and paralytic movement disorders, with fractures extensive enough to involve both segments of the inferior orbital wall. These fractures can cause most of the orbital contents to exit into the maxillary sinus, damaging the inferior rectus muscle and surrounding soft tissues and promoting nerve damage in the innervating muscles. Both ocular muscle restriction and paralytic dyskinesia are present in these cases, with hemorrhage, tear, direct contusion, or related innervation injury of the incarcerated rectus muscle affecting the motor function of the muscle from both restrictive and paralytic aspects.
In conclusion, this study highlights the distinct types of ocular motility disorders caused by fractures in different locations of the inferior orbital wall. The findings underscore the relationship between fracture type and ocular motility disorder, providing valuable insights for determining prognosis and selecting the most appropriate operation time in patients with ocular motility disorders. The study was supported by grants from the Scientific Research Fund of National Health Commission-Henan Province Medical Science and Technology Project and the Basic and Advance Technology Research Project of Henan Province.
doi.org/10.1097/CM9.0000000000001624
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