Orbital blowout fractures: experimental evidence for the pure hydraulic theory

Biomechanical analysis using finite element analysis of orbital floor fractures reproduced in a realistic experimental environment with an anatomical model

Introduction: In this study, we attempted to demonstrate the actual process of orbital floor fracture visually and computationally in anatomically reconstructed structures and to investigate them using finite element analysis. Methods: A finite element model of the skull and cervical vertebrae was reconstructed from computed tomography data, and an eyeball surrounded by extraocular adipose was modeled in the orbital cavity. Three-dimensional volume mesh was generated using 173,894 of the 4-node hexahedral solid elements. Results: For the cases where the impactor hit the infraorbital foramen, buckling occurred at the orbital bone as a result of the compressive force, and the von Mises stress exceeded 150 MPa. The range of stress components included inferior orbital rim and orbital floor. For the cases where the impactor hit the eyeball first, the orbital bone experienced less stress and the range of stress components limited in orbital floor. The critical speeds for blowout fracture were 4 m/s and 6 m/s for buckling and hydraulic mechanism. Conclusion: Each mechanism has its own fracture inducing energy and its transmission process, type of force causing the fracture, and fracture pattern. It is possible to determine the mechanism of the fracture based on whether an orbital rim fracture is present.

Mechanisms of Development of Orbital Fractures: A Review

PURPOSE

The purpose of this study is to review the mechanisms in the development of orbital fractures.

METHODS

This is a comprehensive literature review that summarizes the mechanisms of developing orbital fractures.

RESULTS

There are 3 proposed mechanisms in the development of orbital fractures, which include the buckling, hydraulic, and globe-to-wall contact mechanisms. These mechanisms, as well as patient age, causes of injuries, and periorbital anatomy, influence the extent, sites, and patterns of orbital fractures.

CONCLUSION

A deeper understanding of these mechanisms helps us to detect and properly manage orbital fractures in the clinical setting.

Pressure Onto the Orbital Walls and Orbital Morphology in Orbital Floor or Medial Wall Fracture: A 3-Dimensional Printer Study

The purposes of this study were to compare the pressure onto the orbital floor and medial orbital wall between 3-dimensional printer skull models with unilateral orbital floor and medial orbital wall fractures and to compare the morphology of the orbital floor and medial orbital wall between patients with unilateral orbital floor and medial orbital wall fractures. The skull models were created based on computed tomographic (CT) data obtained from every 10 patients with unilateral orbital floor and medial orbital wall fractures. The orbital spaces of these models were filled with silicone, the silicone surface was pushed down, and pressures onto the orbital floor and the medial orbital wall were measured. On preoperative computed tomographic images taken in the same 20 patients, the superior and lateral bulges of the orbital floor and medial orbital wall were measured, respectively. The measurements were done on the unaffected sides. Consequently, the pressure onto the orbital floor was significantly higher in the orbital floor fracture models than in the medial orbital wall fracture models, although the pressure onto the medial orbital wall was not significantly different between the models. As for the morphologic study, the superior bulge of the orbital floor was higher in the orbital floor fracture group than in the medial orbital wall fracture group. The results of this study indicate that since the orbital floor with a high superior bulge receives high hydraulic pressure, patients with a high superior bulge have a greater risk of orbital floor fracture.

Surgical Approaches to Orbital Fractures: A Practical and Systematic Review

Orbital fractures constitute a significant percentage of all midface injuries. Here, we present a contemporary evidence-based review of the major surgical approaches for orbital wall fractures and analyze the literature to compare all major surgical procedures and their complication rates.

Method

A systematic review was conducted to compare surgical approaches (subciliary, transcaruncular, transconjunctival, subtarsal, and endoscopic) and postoperative complications in patients who underwent surgical fixation of orbital wall fractures. A database search in PubMed (PubMed Central, MEDLINE and Bookshelf) was performed for all articles containing the terms "orbital," "wall," "fracture," and "surgery" with different combinations.

Results

A total of 950 articles were obtained and 25 articles were included, representing an analysis of 1137 fractures. The most frequent surgical approach was the endoscopic (33.3%) followed by the external surgical approaches, specifically transconjunctival (32.8%), subciliary (13.5%), subtarsal (11.5%), and transcaruncular (8.9%). The transconjunctival approach had a statistically significantly higher rate of complications (36.19%), followed by the subciliary (21.4%), and endoscopic approach (20.2%, P < 0.0001). The subtarsal approach had a statistically significantly lower rate of complications (8.2%) followed by the transcaruncular approach (14.0%, P < 0.0001).

Conclusion

The subtarsal and transcaruncular approaches were observed to have the lowest rates of complications, whereas the transconjunctival, subciliary, and endoscopic approaches were reported to have higher rates of complications.

Pediatric Orbital Floor Reconstruction Using a Nonresorbable Polypropylene-Based Hernia Mesh: A Case Report

Orbital floor fracture is the most common type of orbit-related injury seen in pediatric age groups. It is also called a white-eyed blowout fracture when the usual signs of orbital fracture-periorbital edema, ecchymosis, and subconjunctival hemorrhage are absent. Several materials are used for orbital defect reconstruction. The most popular and widely used material is titanium mesh. We present a case of a 10-year-old boy with a white-eyed blowout fracture of the floor of the orbit of the left side. The patient had a history of trauma, after which he developed diplopia in the left eye. On examination, his upward gaze was restricted in the left eye, which was suggestive of inferior rectus muscle entrapment. The orbital floor reconstruction was done using a hernia mesh made up of nonresorbable polypropylene material. This case demonstrates the utility of nonresorbable materials in orbital defect reconstruction in pediatric patients. Further studies are needed to better understand the scope of polypropylene-based materials in the floor of orbit reconstruction and their benefits and shortcomings in the long run.

Validation of Hydraulic Mechanism during Blowout Trauma of Human Orbit Depending on the Method of Load Application

The more we know about mechanisms of the human orbital blowout type of trauma, the better we will be able to prevent them in the future. As long as the buckling mechanism's veracity is not in doubt, the hydraulic mechanism is not based on equally strong premises. To investigate the correctness of the hydraulic mechanism's theory, two different methods of implementation of the hydraulic load to the finite element method (FEM) model of the orbit were performed. The intraorbital hydraulic pressure was introduced as a face load applied directly to the orbit in the first variant, while in the second one the load was applied to the orbit indirectly as a set of nodal forces transferred from the external surface of the eyeball via the intraorbital tissues to the orbital walls within the contact problem. Such an approach is aimed at a better understanding of the pattern for the formation of blowout fractures during the indirect load applied to the orbital bones. The nonlinear dynamic analysis of both numerical models showed that the potential fracture was observed in the second variant only, embracing a relatively large area: both medial and lower wall of the orbit. Interestingly, the pressure generated by the intraorbital entities transferred the energy of the impact to the orbital sidewalls mainly; thus, the nature of the mechanism known as the hydraulic was far from the expected hydraulic pressure. According to the eyeball's deformation as well as the areas of the greatest Huber-Mises-Hencky (H-M-H) stress within the orbit, a new term of strut mechanism was proposed instead of the hydraulic mechanism as more realistic regarding the investigated phenomenon. The results of the current research may strongly influence the development of modern implantology as well as affect forensic medicine.

Biomechanical assessment of orbital fractures using patient-specific models and clinical matching

INTRODUCTION

Orbital wall fractures consider one of the most common fractures in the maxillofacial trauma. These fractures caused by two mechanisms, the buckling mechanism and hydraulic mechanism. This study aims to compare between the two mechanisms in terms of intensity and extension using the finite elements method.

MATERIAL AND METHODS

Three-dimensional model of the skull was generated using computed tomography data of young male patient. Virtual loads were applied on the eyeball and the infra-orbital rim separately. Von Mises stresses were examined in each simulation.

RESULTS

The simulation predicted fractures on the infra-orbital rim and orbital floor when simulating the hydraulic mechanism, and on the orbital floor and mesial wall when simulating the buckling mechanism.

CONCLUSION

Biomechanical studies are essential part in understanding maxillofacial fractures mechanisms. The results confirmed and ascertained what is seen clinically, and explained clearly the two mechanisms of orbital fractures.

Occurrence of ocular injury and orbital fracture in orbital blunt trauma patients at tertiary care center emergency room

PURPOSE

To analyze the prevalence and association of ocular injury and orbital fracture in orbital trauma patients METHODS: Patients with periocular trauma who visited the emergency room at the referral center from 2014 to 2016 were screened. Patients examined by ophthalmologists and evaluated by CT scan were included. Patients' age, gender, cause of trauma, and injury patterns were retrieved. The location of the fracture and morphologic parameters were reviewed. The patients were divided into groups based on the presence of orbital fracture and/or the presence of ocular injury and clinical data were compared.

RESULTS

Two hundred patients were included and 158 presented with fracture. Ocular injuries occurred in 129 of 158 (81.6%) in the fracture group, and in 40 of 42 (95.2%) in the no fracture group; ocular injuries were found more often in the no fracture group (p = 0.031). Open globe injuries occurred in 5 of 158 (3.2%) in the fracture group and in 6 of 42 (14.3%) in the no fracture group; open globe injuries were found more often in the no fracture group (p = 0.012). Patients with ocular injuries showed shorter depth of the orbit (41.9 vs. 44.1 mm; p = 0.003) compared to the patients without ocular injuries. Logistic regression revealed that short orbit was associated with the presence of ocular injury (p = 0.004).

CONCLUSION

The incidence of ocular injuries was significantly higher in patients without orbital fracture than in those with fractures of the orbit. The orbital fracture may play a protective role against ocular injury by providing a decompressive effect on the orbital tissue.

Medial Buttressing in Orbital Blowout Fractures

PURPOSE

To study whether ethmoidectomy predisposes the orbit to medial wall fracture with lesser trauma.

METHODS

An interventional cadaver study of 5 heads (10 orbits); the left or right orbit was randomized to undergo endoscopic complete ethmoidectomy with the fellow orbit as control. Fractures were induced with direct globe trauma, and heads underwent CT scanning. Energy to induce fracture, peak orbital pressure at time of fracture, fracture pattern, and volume of herniated tissue were measured and analyzed.

RESULTS

Fractures were induced in both orbits of all cadavers. Experimental orbits after ethmoidectomy sustained orbital fracture at less energy required (2.14 ± 0.66 vs. 3.10 ± 0.19 J, mean difference: -0.96 ± 0.33 J, p < 0.05). Similarly, peak orbital pressure was lower for ethmoidectomized orbits than for controls (11.8 ± 8.42 vs. 28.4 ± 13.2 mm Hg, mean difference: -16.5 ± 6.9 mm Hg, p < 0.05). Orbits after ethmoidectomy were more likely to sustain medial wall involvement in fracture (100%) compared with controls (20%, p < 0.05) and pure medial wall fracture (80%) compared with controls (0%, p < 0.05). Overall volume of herniated orbital contents was not significantly different between groups (p = 0.25); volume of herniated tissue from the medial wall only was significantly greater in orbits after ethmoidectomy (mean difference: 1.01 ± -0.39 cm, p < 0.05).

CONCLUSION

Endoscopic ethmoidectomy in fresh cadavers reduces impact energy necessary to induce orbital fracture and increases the prevalence of medial wall involvement. Clinicians may wish to counsel patients undergoing endoscopic sinus surgery about these relative risks.

Biomechanic Factors Associated With Orbital Floor Fractures

Importance

Orbital floor fractures are commonly seen in clinical practice, yet the etiology underlying the mechanism of fracture is not well understood. Current research focuses on the buckling theory and hydraulic theory, which implicate trauma to the orbital rim and the globe, respectively.

Objective

To elucidate and define the biomechanical factors involved in an orbital floor fracture.

Design, Setting, and Participants

A total of 10 orbits from 5 heads (3 male and 2 female) were used for this study. These came from fresh, unfixed human postmortem cadavers that were each selected so that the cause of death did not interfere with the integrity of orbital walls. Using a drop tower with an accelerometer, we measured impact force on the globe and rim of cadaver heads affixed with strain gauges.

Results

The mean impacts for rim and globe trauma were 3.9 J (95% CI, 3.4-4.3 J) and 3.9 J (95% CI, 3.5-4.3 J), respectively. Despite similar impact forces to the globe and rim, strain-gauge data displayed greater mean strain for globe impact (6563 μS) compared with rim impact (3530 μS); however, these data were not statistically significant (95% CI, 3598-8953 μS; P = .94).

Conclusions and Relevance

Our results suggest that trauma directly to the globe predisposes a patient to a more posterior fracture while trauma to the rim demonstrates an anterior predilection. Both the hydraulic and buckling mechanisms of fracture exist and demonstrate similar fracture thresholds.

Level of Evidence

NA.

The Pattern of Orbital Fractures Managed at Two Referral Centers in Nairobi, Kenya

Orbital fractures are one of the commonest injuries in mid-face trauma and can lead to significant functional and cosmetic defects. This study was aimed at analyzing the pattern of orbital fractures at 2 referral centers in Nairobi. It was a descriptive prospective hospital-based study of the demographics, etiology, clinico-radiological features, and management modalities among patients presenting with orbital fractures at the University of Nairobi Dental Hospital and Kenyatta National Referral Hospital in Nairobi, Kenya. A total of 60 patients (52 males, 8 females; P <0.05) with confirmed orbital fractures were recruited during the 6-months study period. Orbital fractures occurred most frequently in the 21 to 40-year-old age group (80%, P<0.05). The principal etiological factors were motor cycle crashes; 30%, interpersonal violence 23.3%, public vehicle crushes 20%, private vehicle crushes; 10%, injury from flying objects 10% and falls 8.3%. The most commonly affected anatomical sites were the floor (75%), the lateral wall (71.7%), infra-orbital rim (66.7%), zygomatico-frontal suture (63.3%). There were 5 (8.3%) cases of total blindnessThe impure orbital fractures that involve the satellite bones especially the zygomatic complex predominate.

Considerations for the Management of Medial Orbital Wall Blowout Fracture

Recently, diagnoses of and operations for medial orbital blowout fracture have increased because of the development of imaging technology. In this article, the authors review the literature, and overview the accumulated knowledge about the orbital anatomy, fracture mechanisms, surgical approaches, reconstruction materials, and surgical methods. In terms of surgical approaches, transcaruncular, transcutaneous, and transnasal endoscopic approaches are discussed. Reconstruction methods including onlay covering, inlay implantation, and repositioning methods are also discussed. Consideration and understanding of these should lead to more optimal outcomes.

Different onset pattern of oculocardiac reflex in pediatric medial wall blowout fractures

PURPOSE

We report the 2 pediatric patients who had radiographic confirmation of a rare case of medial orbital wall "trapdoor" fracture with extraordinary symptoms of oculocardiac reflex (OCR).

METHODS

This was a small interventional case series.

RESULTS

This is the retrospective report of 2 boys (13 and 10 years old) who developed diplopia, pain, nausea/vomiting, and general malaise following blunt trauma. However, the onset pattern of OCR was absolutely different: delayed onset of OCR just following therapeutic forced duction test to treat the orbital content herniation in the first case and a sudden onset after injury in the second case. In both cases, urgent surgery led to complete normalization of ocular motility.

CONCLUSIONS

Prompt diagnosis and proper treatment are critical to maximize clinical outcome for this rare and critical trauma.

Need for airbag and seatbelt to reduce orbital injuries from steering wheel knob

The aims of this study are to report a blowout fracture of the orbital floor and medial wall caused by being struck by a steering wheel knob of an automobile and to discuss the use of airbags and seatbelts as a preventive measure for orbital injuries. A 58-year-old man was struck in the left eye by a steering wheel. His car hit a telephone pole, and he had a frontal collision injury. In this frontal impact, his left eye was hit by a Brodie knob attached to the steering wheel. At the time of injury, the speed of the car was about 65 km/h. He was not wearing a seatbelt, and the airbag had not deployed. Swelling and ecchymosis were observed at the left periorbital area, and he had diplopia on a left-side gaze. A CT revealed fractures in the medial and inferior wall of the left orbit. Entrapped soft tissues were reduced, and the medial wall and floor were reconstructed with a resorbable sheet. His diplopia disappeared 12 days after surgery. To prevent the injury from the steering wheel knob, an airbag should be installed in any vehicle, which has a steering wheel knob. Legislation mandating the use of airbags as well as seatbelts in vehicles with attached steering wheel knobs should be made.

Orbital trapdoor fractures

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management.

Orbital blowout fracture caused by nose blowing

The occurrence of an orbital blowout fracture caused by nose blowing is an unusual phenomenon. We report a rare case of such a fracture in the bony floor of the orbit of a 30-year-old man. Immediately after strong nose blowing, he experienced left eyelid edema and diplopia. Computed tomography confirmed the presence of a blowout fracture of the inferior wall of the left orbit. His symptoms abated without any surgical treatment. In addition to the facts of this case, we discuss the findings of physiologic studies and human cadaver studies in the context of nose blowing as an etiologic factor in orbital blowout fracture.

Medial wall fracture: an update

This article is a review of the literature and update for management of medial orbital wall fractures. A retrospective review of the literature was performed via PubMed to review the diagnosis and management of medial wall orbital fractures. Medial wall orbital fractures though commonly accompanying orbital floor fractures can also occur alone. There are two primary theories explaining the pathophysiology of medial wall fractures: the hydraulic theory and buckling theory. Most fractures do not require treatment. "White-eyed" trapdoor fractures necessitate immediate surgery to reduce the risk of muscle fibrosis. Trapdoor fractures are more common in the pediatric population. The vast majority of nondisplaced fractures without entrapment do not require surgery. Evaluating patients with medial wall fractures requires evaluation of muscle motility and relative enophthalmos. Patients with entrapped muscles require immediate treatment to prevent permanent injury to the muscle.

Forces charging the orbital floor after fractures

The objective of this study was first to establish a method to measure forces and displacement of the orbital content in defects of the orbital floor in truncated fresh and unfixed heads and second to characterize reconstruction materials with regard to punctuation strength and compression.Orbital floor defects (10 × 20 mm and 15 × 20 mm; 3 mm behind the orbital rim) were prepared after Le Fort I osteotomy. The values of force and displacement were recorded in 6 freshly frozen human heads. In addition, the punctuation strength of 2 reconstruction materials (polydioxanone [PDS] foil and collagen membrane) was evaluated using a Zwick Z010 TN1 universal testing machine. The forces of the orbital content (28.41 [SD, 1.6] g) applied to the defects of 10 × 20 mm and 15 × 20 mm with an intact periorbita were 0.04 (SD, 0.003) N (0.0002 MPa) and 0.07 (SD, 0.02) N (0.0002 MPa), respectively, and with a split periorbita were 0.06 (SD, 0.03) N (0.0003 MPa) and 0.08 (SD, 0.06) N (0.00026 MPa), respectively. The displacement values without reconstruction materials of the 10 × 20-mm and 15 × 20-mm defects were 0.94 (SD, 0.7) mm and 1.2 (SD, 0.5) mm, respectively. The PDS foil could withstand forces of 118.9 (SD, 14.1) N (0.375 MPa), and the collagen membrane could withstand forces of 44.5 (SD, 5.3) N (0.14 MPa). This is the first study to report forces charging the orbital floor. The presented results support the use of PDS foils and collagen membranes as reconstruction materials for orbital floor defects, at least in smaller and medium-sized fractures.

Orbital floor reconstruction considering orbital floor slope

Orbital floor fractures are among the more challenging injuries faced by plastic surgeons. Enophthalmos is defined as backward, usually downward, displacement of the globe into the bony orbit. We describe reconstruction of the orbital floor slope in orbital floor fractures that prevents postoperative complications, especially posttraumatic enophthalmos. Thirty-three patients with orbital floor fractures were treated using reconstruction of the orbital floor slope between April 2009 and July 2010. The patients ranged in age from 12 to 54 years. There were 31 males and 2 females. All patients were operated on using a transconjunctival approach under general anesthesia. The orbital floor was reconstructed with poly-l/d-lactide sheets in all cases. Preoperatively, 23 [Float1]patients (69%) had enophthalmos, and 12 patients (36%) had symptomatic diplopia. The enophthalmos was corrected in 20 patients (86%), and the diplopia resolved in 10 (83%). Extrinsic ocular movement was impaired preoperatively in 1 patient (3%), but resolved after surgery. No patient had impaired visual acuity preoperatively or postoperatively. The results suggest that orbital floor reconstruction considering the orbital floor slope is a safe, reliable method with fewer complications that is more effective at preventing posttraumatic enophthalmos.

Pediatric orbital floor fractures

PURPOSE

To summarize the unique aspects of orbital floor fractures in children with regard to clinical presentation, management, and outcomes.

METHODS

MEDLINE was searched using PubMed for English-language articles on orbital floor fractures in children. All 154 indexed articles pertaining to floor fractures in patients under 18 years of age in PubMed were reviewed. Studies looking at primarily complex fractures and case reports and studies that included pediatric patients but did not analyze them separately were excluded. Overall, 25 studies were included for the review.

RESULTS

Inferior trapdoor fractures with muscle and soft tissue incarceration are the most common type of orbital fracture in children (27.8%-93%). They often present uniquely with severely restricted extraocular motility and diplopia (44%-100%), nausea and vomiting (14.7-55.6%), and minimal signs of external trauma. The majority of studies (83%) that analyzed time to surgery in relation to outcomes found that children who present early after initial injury and undergo prompt surgical repair appear to recover faster and have better postoperative motility than those receiving delayed treatment.

CONCLUSIONS

Our understanding of pediatric orbital floor fractures continues to evolve. For young patients with symptomatic diplopia with positive forced ductions, soft tissue entrapment confirmed by computed axial tomography, and/or trapdoor fracture plus restricted ocular movement, having surgery within 2-5 days has been shown to result in better postoperative outcomes. It is recommended that surgery be considered within 48 hours of diagnosis. Long-term prospective studies are still needed to further characterize orbital floor fractures in children.

Clinical analysis of orbital blowout fractures caused by a globe-to-wall contact mechanism

Computed tomograms of blowout fractures of the pure medial and inferomedial wall that showed that the size of the orbital displacement exactly fitted the shape of the globe in many cases were investigated. To examine the veracity of a "globe-to-wall contact mechanism", we have analysed our own cases of medial or inferomedial blowout fractures (and also the charts of presumptive cases in which this mechanism was suspected), for the clinical information. The size of the displacement of the orbital wall exactly fitted the globe in 20/45 patients (44%). All fractures occurred in the inferomedial area of the orbital wall. In our study, serious complications such as corneal laceration, global rupture, paralysis of the cranial nerve, and ophthalmic nerve neuropathy were seen more often than in other studies.

Interaction of hydraulic and buckling mechanisms in blowout fractures

The etiology of blowout fractures is generally attributed to 2 mechanisms--increase in the pressure of the orbital contents (the hydraulic mechanism) and direct transmission of impacts on the orbital walls (the buckling mechanism). The present study aims to elucidate whether or not an interaction exists between these 2 mechanisms. We performed a simulation experiment using 10 Computer-Aided-Design skull models. We applied destructive energy to the orbits of the 10 models in 3 different ways. First, to simulate pure hydraulic mechanism, energy was applied solely on the internal walls of the orbit. Second, to simulate pure buckling mechanism, energy was applied solely on the inferior rim of the orbit. Third, to simulate the combined effect of the hydraulic and buckling mechanisms, energy was applied both on the internal wall of the orbit and inferior rim of the orbit. After applying the energy, we calculated the areas of the regions where fracture occurred in the models. Thereafter, we compared the areas among the 3 energy application patterns. When the hydraulic and buckling mechanisms work simultaneously, fracture occurs on wider areas of the orbital walls than when each of these mechanisms works separately. The hydraulic and buckling mechanisms interact, enhancing each other's effect. This information should be taken into consideration when we examine patients in whom blowout fracture is suspected.

The paranasal sinuses as a protective crumple zone for the orbit

OBJECTIVES/HYPOTHESIS

The purpose of this study is to test the theory that the paranasal sinuses serve a protective function for the central nervous system and special sensory organs.

STUDY DESIGN

Nonrandomized experimental trauma study with fresh human cadavers.

METHODS

Fresh human cadaver heads were obtained and the sinuses on one side underwent endoscopic endonasal sinus surgery and were then filled with radio-opaque bone cement to obliterate them. The contralateral sinuses were not operated upon to allow both for comparison to the experimental side and to serve as an intraspecimen control. The cadavers underwent serial computed tomography (CT) scans. Scans were performed prior to surgery, after surgery, and after unilateral sinus obliteration to obtain baseline CT studies prior to any impact testing. Sequential drops of increasing energy were then performed directing the impacts onto the globes. Initial endpoints were either orbital fractures or ocular injury. Trauma was induced by impacting a weighted rod onto the globes using a guided drop technique. Orbital rim impact was avoided, so that the effect of direct globe trauma could be assessed; fractures were thus induced via the hydraulic mechanism, in which force is transmitted through the globe to the surrounding tissues and orbital walls. After initial injury endpoints were met, additional impact testing was performed on globes, in which fractures occurred with lower drop forces to ensure impact energy equivalence between the control and the experimental sides.

RESULTS

All the experimentally obliterated paranasal sinus orbits tested suffered trauma-induced globe ruptures, and no orbital wall fractures were encountered. On the control sides, no globe ruptures occurred at either an equivalent or higher energy than the energy needed to induce globe ruptures on the experimental side orbits, although orbital floor fractures on the control sides occurred after lower energy impacts in some cases.

CONCLUSIONS

This study demonstrates that the thin orbital floor fractures preferentially, thereby protecting the globe from rupture as a result of the directed trauma. When the sinus crumple zones were eliminated, globe ruptures occurred.

Incidence of ocular injury in visually asymptomatic orbital fractures

PURPOSE

To determine the incidence of severe ocular injury in visually asymptomatic patients with orbital fractures.

METHODS

Retrospective review of 241 cases of orbital fracture, of which 126 cases had ophthalmic evaluation within 1 week of injury and were included in our analysis. Fracture type, associated symptoms, and injuries were evaluated. Injuries were categorized into severe (requiring immediate evaluation), moderate (requiring evaluation within the next several days), and mild (may not require evaluation). The presence of symptoms and associated visual acuity and severity of injury were analyzed for statistical significance.

RESULTS

Forty-six of 126 patients with orbital fractures were visually asymptomatic. Of these patients, none had severe injuries, 15 had moderate injuries, 23 had mild injuries, and 8 had no injuries. Of those with symptoms, 15 had severe injuries, 27 had moderate injuries, 35 had mild injuries, and 3 had no injuries. Using Fisher exact test analysis, asymptomatic patients were unlikely to have severe ocular injury in the setting of orbital fracture (p = 0.0009). In addition, visual acuity did not accurately predict the presence of severe ocular injury.

CONCLUSION

Visually asymptomatic patients with orbital fractures do not have ocular injury requiring emergent evaluation.

Untersuchungen zum Entstehungsmechanismus der isolierten Orbitabodenfraktur

BACKGROUND

Isolated orbital floor fractures make up a significant proportion of all facial injuries, but the mechanism involved in these injuries to the orbital walls (blow-out fractures) has not yet been completely defined. Two theories have been described, which seem to be mutually exclusive. According to the hydraulic pressure theory, the kinetic energy of the blow is transferred via the incompressible eye tissue to the floor of the orbita, which in turn fractures. The buckling force theory, in contrast, explains these fractures as the result of bending and shear stresses arising from kinetic energy act directly on the orbital rim.

MATERIALS AND METHODS

With the aim of elucidating the mechanism of injury, we constructed a simplified finite-element model of the human orbita by 3D optical scanning of a human skull obtained after an autopsy examination. We created a generic approximation model based on empiric data derived from femoral fractures and reported in the literature. Several experiments were conducted to test both the above hypotheses by direct and indirect application of kinetic energy.

RESULTS

We simulated different types of shear stress with the finite-element model of the skull. The calculated points of maximum pressure were all within the orbital floor.

CONCLUSION

The simulation showed that both mechanisms can lead to fractures, as also documented by recent studies. The generation of a finite-element model and simulation of stresses were initially useful in establishing a method. More detailed studies on the empiric data relating to the various structures and more extensive determination and measurement of different skull and/or orbita geometries are needed before we can achieve a model in which the mechanical attributes of the structures involved are reproduced with closer approximation to the real-life situation.

Air Bag-Induced Orbital Blow-Out Fractures

RATIONALE

Although air bags have decreased the risk of serious injury from motor vehicle crashes, their deployment is not innocuous and can result in injury. The force of the deploying air bag can cause orbital blow-out fractures. We investigated the circumstances that predispose a crash occupant to this particular injury.

STUDY DESIGN

The authors conducted a case series.

METHODS

A total of 150 orbital fractures occurred among 2,739 occupants in crashes included in the Crash Injury Research and Engineering Network (CIREN) database from January 1997 to July 2005. Ten orbital blow-out fractures attributed solely to air bag deployment were extracted and four reported in depth. Occupant, vehicle, and crash characteristics were reviewed for predisposing similarities and to investigate the mechanism of injury.

RESULTS

All crashes had air bag deployment and a frontal or near-frontal principle direction of force. Nine of 10 injured occupants were positioned within the air bag's deployment zone at the time of impact as a result of a forward seat track position, falling asleep at the wheel, being unrestrained, or having decelerated before impact. Six of 10 occupants experiencing orbital blow-out fractures were of shorter than average height. Based on rigorous crash reconstructions, the orbital blow-out injuries were felt to be causally related to air bag deployment.

CONCLUSION

Air bag deployment may result in orbital blow-out fractures. Occupants positioned in close proximity to the air bag during its deployment phase appear to be at increased risk for orbital blow-out fractures.

Radiologic Evaluation of Lacrimal and Orbital Disease

This article discusses the evaluation of specific lacrimal disorders and orbital trauma using CT, MRI, and other radiologic techniques.

Recognition and management of an orbital blowout fracture in an amateur boxer

STUDY DESIGN

Case report.

OBJECTIVES

To identify key elements in the recognition and management of a patient with an orbital blowout fracture and make recommendations on diagnosis, treatment, referral, imaging, and return to sports.

BACKGROUND

Orbital blowout fractures are uncommon but important injuries for physical therapists to recognize. Immediate management is essential in preventing complications. The mechanism of injury is a direct blow to the orbital rim or orbit.

CASE DESCRIPTION

The patient reported to the athletic training room 15 minutes after completing a boxing match and reported that his left eye had suddenly inflated after blowing his nose. We suspected an orbital blowout fracture and referred him immediately to the emergency department where conventional radiographs were ordered. On follow-up the next day, after determining that the radiographs were normal, but still having a high index of suspicion for an orbital blowout fracture, we referred him to his primary care manager. The primary care manager ordered a computed tomography scan that revealed the fracture and referred the patient to ophthalmology.

OUTCOMES

The patient was restricted from the remaining 4 weeks of the boxing season. He completed a rigorous Army physical fitness test 7 days postinjury and the Marine Corps Marathon 47 days postinjury.

DISCUSSION

Orbital blowout fractures without double vision, extraocular muscle entrapment, or persistent numbness can be treated with time and protection. The patient can continue with normal fitness activities except contact or collision sports.

Endoscopic Approach to Medial Orbital Wall Fractures

Repair of medial orbital wall fractures can be challenging with traditional open techniques. This article describes different endoscopic-assisted approaches-transcaruncular and intranasal-which have been used to successfully repair these fractures.

Assessment of biomechanics of orbital fracture: a study in goats and implications for oculoplastic surgery in humans

PURPOSE

To determine the biophysical characteristics of energy absorption of the various orbital structures and the amount of force/energy required to produce an orbital fracture in goats, and to interpret results in terms of human clinical applicability.

DESIGN

Experimental animal study.

METHODS

The energy required to fracture the orbit on direct globe impact was measured. We used a variety of other measurements, including high-speed videography, intraocular pressure, and intraorbital pressure measurements to describe the biophysics of floor fracture. Twenty-one goats and 42 orbits were studied in this single institutional site study.

RESULTS

Our measurements determined the fracture threshold for the caprine orbit averaged 26.5 N (SE 3.1 N) with a total energy threshold for fracture of 2600 mJ (SE 280 mJ). Eye deformation measured 6 mm with deformation energy dissipation measuring 100 to 180 mJ (SE 10 mJ). Eye displacement measured 10 mm with dissipation measuring 50 to 75 mJ (SE 4.0 mJ). The deconvoluted bone fracture energy averaged 2350 mJ (SE 260 mJ).

CONCLUSIONS

Impact energy applied to the orbit through the eyeball is absorbed and dissipated by three primary mechanisms: (1) globe deformation, (2) globe displacement, and (3) orbital fracture. Excess energy (above the energy required for deformation and displacement) >or=2350 mJ will result in an orbital fracture.

Clinical signs of orbital wall fractures as a function of anatomic location

OBJECTIVE

The objective of this study was to see whether clinical signs of medial orbital wall fractures distinguished these fractures from fractures of the lateral orbital wall and the orbital floor.

STUDY DESIGN

The orbital fractures of 424 patients were analyzed. The patients were divided into 2 groups: (1) patients with orbital fractures with a medial orbital wall component and (2) patients with orbital fractures without a medial orbital wall component.

RESULTS

Orbital fractures with involvement of the medial orbital wall showed a significantly higher incidence (P =.001) of diplopia and exophthalmos (P =.039) than fractures without involvement of the medial wall.

CONCLUSION

Posttraumatic orbital clinical signs are associated with a higher incidence of medial orbital wall component fracture. Apparent lack of involvement of the medial orbital wall should not be an exclusion criterion for a surgical intervention when clinical orbital signs exist.