Medial Buttressing in Orbital Blowout Fractures

Assessment of Orbital Compartment Pressure: A Comprehensive Review

The orbit is a closed compartment defined by the orbital bones and the orbital septum. Some diseases of the orbit and the optic nerve are associated with an increased orbital compartment pressure (OCP), e.g., retrobulbar hemorrhage or thyroid eye disease. Our aim was to review the literature on the different approaches to assess OCP. Historically, an assessment of the tissue resistance provoked by the retropulsion of the eye bulb was the method of choice for estimating OCP, either by digital palpation or with specifically designed devices. We found a total of 20 articles reporting direct OCP measurement in animals, cadavers and humans. In nine studies, OCP was directly measured in humans, of which five used a minimally invasive approach. Two groups used experimental/custom devices, whilst the others applied commercially available devices commonly used for monitoring the compartment syndromes of the limbs. None of the nine articles on direct OCP measurements in humans reported complications. Today, OCP is mainly estimated using clinical findings considered surrogates, e.g., elevated intraocular pressure or proptosis. These diagnostic markers appear to reliably indicate elevated OCP. However, particularly minimally invasive approaches show promises for direct OCP measurements. In the future, more sophisticated, specifically designed equipment might allow for even better and safer measurements and hence facilitate the diagnosis and monitoring of orbital diseases.

Traumatic dislocation of the eye into the maxillary sinus: Case report and literature review

Traumatic dislocation of the eye is usually encountered in high-energy injuries. These include traffic accidents, accidents at work, sporting accidents, falling from a height, impact of the hooves or horns of animals, gunshot injuries, and physical assault. Such incidents are accompanied by facial soft tissue damage and injuries to the facial skeleton, especially the orbit, and can be associated with varying degrees of dislocation of the eye. We describe a rare case of non-fatal traumatic eye dislocation into the maxillary sinus, coupled with an orbital fracture resulting from a physical assault on a 63-year-old woman. The cause of death was asphyxiation due to manual strangulation and mechanical asphyxia. Even though dislocations of the eye are relatively rare, forensic pathologists should be aware of such injuries to correct assessment of injury mechanism. The available literature regarding eye dislocation is summarized, and the forensic issues applicable to the assessment of such cases are reviewed.

Aetiology, clinical features and surgical outcomes of isolated medial rectus palsy

IMPORTANCE

Isolated medial rectus palsy is extremely rare in clinical practice.

BACKGROUND

To report demographics, aetiology, clinical findings, imaging features and surgical outcomes in patients with isolated medial rectus palsy.

DESIGN

Retrospective study.

PARTICIPANTS

All patients treated for isolated medial rectus palsy at Zhongshan Ophthalmic Center, Sun Yat-sen University, between September 2003 and March 2019.

METHODS

Review of patient records.

MAIN OUTCOME MEASURES

Aetiology, clinical findings, imaging features and surgical outcomes.

RESULTS

A total of 32 patients (22 males, 10 females) were included. Mean age was 33.19 ± 19.78 years. The right eye was involved in 17 patients, the left eye was involved in 14 patients, and both eyes were involved in one patient. The most common causes were iatrogenic injury (43.75%), followed by trauma (37.50%) and congenital (18.75%). The most common clinical findings included outward deviation, diplopia and limited adduction. Six patients showed combined small-angle vertical strabismus, and 10 patients experienced a scale of -1 motility defect in other directions. After individualized strabismus surgery, preoperative exotropia of 60 ± 25 prism diopters (PD) was significantly reduced to 12 ± 13 PD (t = 10.938, P < .0001). Ocular motility improved in 21 patients, and five patients achieved normal ocular motility. Successful correction was obtained in 20/32 (62.50%) patients, with under-correction in 12/32 (37.50%) patients. Twenty-eight patients had only one surgery, three patients had two surgeries and one patient had three surgeries.

CONCLUSIONS AND RELEVANCE

The most common cause of isolated medial rectus palsy was local injury. Satisfactory results were obtained after individualized surgical interventions based on personalized preoperative evaluations.

Does endoscopic sinus surgery alter the biomechanics of the orbit?

Objective

The purpose of this study is to determine if removal of ethmoid cell septations as commonly performed in endoscopic sinus surgery leads to a change in orbital wall fracture patterns and the force required to create them.

Methods

Six fresh-frozen cadaveric heads were acquired and underwent endoscopic uncinectomy, maxillary antrostomy, and anterior and posterior ethmoidectomy on one, randomized, side. The contralateral sinuses were used as intra-specimen control. Hyaluronic acid gel globe injections were performed to simulate normal intra-ocular pressure. Post-op CT scans confirmed no orbital fractures or violation of the lamina papyracea prior to trauma testing. Orbital trauma was induced using a guided weight-drop technique. Both orbits were tested in random order, and sequentially higher drops were performed until both the test and control side demonstrated an orbital fracture on CT scan.

Results

In all six heads, the post-sinus surgery side incurred a medial orbital wall fracture, and no orbital floor fractures were identified. On the other hand, on the control side, all six heads incurred orbital floor fractures at drop heights equal to, or higher than, the surgical side. Fisher’s exact test demonstrated a significant difference in fracture pattern (p <  0.001).

Conclusions

To our knowledge, this is the first demonstration that the structures removed during sinus surgery may act as a buttress for the medial orbital wall. The anatomic changes of sinus surgery may alter the biomechanics of the orbit and affect the pattern of subsequent traumatic blowout fractures.

Finite element analysis of the human orbit. Behavior of titanium mesh for orbital floor reconstruction in case of trauma recurrence

INTRODUCTION

The authors' main purpose was to simulate the behavior of a titanium mesh implant (TMI) used to reconstruct the orbital floor under the stress of a blunt trauma.

MATERIALS AND METHODS

The orbital floor of a previously validated finite element model (FEM) of the human orbit was numerically fractured and reconstructed by a simplified TMI. Data from a CT scan of the head were computed with MICMICS (Materialise, Louvain, Belgium) software to re-create the skull's geometry. The meshing production, the model's properties management and the simulations of blunt traumas of the orbit were conducted on HYPERWORKS^® software (Altair Engineering, Detroit, MI, USA). Some of the elements of the orbital floor were selected and removed to model the fracture; these elements were duplicated, their characteristics being changed by those of titanium to create a TMI covering this fracture. A 3D FEM composed of 640,000 elements was used to perform 21 blunt trauma simulations on the reconstructed orbit.

RESULTS

In 90.4% (19/21) of the tests conducted, the TMI, whether free from any bony attachment or screwed to the orbital rim, has tended to move in the orbit and/or to deform.

DISCUSSION

In the event of traumatic recurrence, which is not rare, TMIs may deform in a "blow-in" motion and threaten intra-orbital structures.

Development and validation of an optimized finite element model of the human orbit

INTRODUCTION

The authors' main purpose was to develop a detailed finite element model (FEM) of the human orbit and to validate it by analyzing its behavior under the stress of blunt traumas.

MATERIALS AND METHODS

A pre-existing 3D FEM of a human head was modified and used in this study. Modifications took into account preliminary research carried out on PubMed database. Data from a CT scan of the head were computed with Mimics^® software to re-create the skull geometry. The mesh production, the model's properties and the simulations of blunt orbital traumas were conducted on Hyperworks^® software.

RESULTS

The resulting 3D FEM was composed of 640 000 elements and was used to perform blunt trauma simulations on an intact orbit. A total of 27 tests were simulated. Fifteen tests were realized with a metallic cylinder impactor; 12 tests simulated a hit by a closed fist. In all the tests conducted (27/27), the orbital floor was fractured. Fracture patterns were similar to those found in real clinical situations according to the buckling and hydraulic theories of orbital floor fractures.

DISCUSSION

The similitude between the fracture patterns produced on the model and those observed in vivo allows for a validation of the model. This model constitutes, at the authors knowledge, the most sophisticated one ever developed.