Severe distortion of an orbital titanium mesh implant after recurrent facial trauma: a potential threat to the orbital contents?

Orbital Floor Fractures Comparing Different Kinds of Reconstruction: A Proposal for Restoration of Physiological Anatomy

ABSTRACT

The most effective treatment for orbital fractures is still under debate and different strategies are proposed in the literature. All such strategies focus on reconstruction of the orbital structure, neglecting the main function of the medial and inferior walls, these latter being constructed so as to break during high energy trauma. The aim of the authors is to highlight the difference between different reconstructive techniques in an orbital fracture restoration, being inclined to favor repair over reconstruction of the orbital floor, assuming that a second trauma could happen and reconstructive material left in the orbit may damage the visual apparatus in such a scenario. Following this theme, the authors propose a reconstruction strategy using a custom made stereolithographic model and resorbable plate made of polylactic acid mesh molded onto it. The mesh is used alone or in combination with bone graft, to obtain a better reparative result. At present, this approach is best suited to sports people and the young. Even if a deeper evaluation of the method would be useful, the series of case studies presented could be of stimulus for future discussion.

Self-centering second-generation patient-specific functionalized implants for deep orbital reconstruction

Deep and complete reconstruction of the orbital cavity has been shown to be essential for preventing enophthalmos and hypoglobus in patients with orbital defects or deformities. Additively manufactured patient-specific titanium implants provide unlimited options in design. However, implant malpositioning can still occur, even when intraoperative imaging and navigation are used. In this study, we investigated novel orbital implants containing features facilitating self-centering. Accuracy of implant placement and reconstruction of the orbital dimensions were compared retrospectively between self-centering second-generation patient-specific functionalized orbital implants (study group) and CAD-based individualized implants (control group). Design features of implants in the study group included functionalization with navigation tracks, a preventive design, and flanges - so called stabilizers - towards opposite orbital walls. Implant position was evaluated by fusion of preoperative virtual plans and the post-therapeutic imaging. Aberrances were quantified by 3D heatmap analysis. 31 patients were assigned to the study group and 50 to the control group, respectively. In the study group, most implants were designed with either one (n = 18, 58.06%) or two (n = 10, 32.26%) stabilizers. Twice (6.45%), one stabilizer had to be shortened intraoperatively. Implant fit analysis revealed a significantly more precise (p < 0.001) positioning in the study group (n = 22/31) than in the control group (n = 42/50). Self-centering second-generation patient-specific functionalized orbital implants showed significantly more accurate implant positioning, facilitating the transformation of virtual plans into patient's anatomy. The presented design provides an additional instrument for intraoperative quality control besides intraoperative imaging and navigation.

Do mandibular miniplates increase the risk of complex fracture in facial trauma recurrence? Case series

Whether to conserve or remove miniplates, widely used in oral and maxillofacial surgery, has not been agreed on in the literature. Complications such as pain, infection, and screw exposure or loosening have already been largely described. We present the consequences of a trauma recurrence on a mandible with miniplates. The data of 13 patients who had a mandibular fracture previously surgically treated with miniplates (ten mandibular fractures and three mandibular osteotomies) were analysed. All the patients were male; the average age was 32 years (range, 20-64 years). The mechanism of the second trauma was assault in most of the cases. The average time between the first osteosynthesis and the new fracture was 35 months (range, 6-128 months). The fractures occurred at a distance from the miniplates in all the cases except two. No plate fracture was reported. We hypothesised that miniplates reinforced the underlying bone, protecting it from fractures, and transmitted the forces to areas anterior or posterior to the miniplates or to the condyle. Thus, the risk of mandible trauma recurrence should be taken into account in the indication of plate removal, and the biomechanical consequences of the conservation of the miniplates should be studied.

Titanium Nickelide in Midface Fractures Treatment

Background: The question of reconstruction of human tissues and organs with the use of medical materials is still open, because of the accurate requirements for their biological and physical features. The aim of this study was to prove the efficiency of titanium nickelide constructors in treatment of isolated orbital floor fractures or combination with zygomatico-orbital complex fractures. Methods: Patients with a fracture of zygomatico-orbital complex and/or low orbital floor (n = 44) carried out different treatments: in the first group, osteosynthesis and endoprosthesis with titanium nickelide structures; in the second group, titan mini-plates osteosynthesis; in the third group (‘blow-out’), endoprosthesis with a titanium nickelide mesh; and in the fourth group (‘blow-out’), conservative treatment and monitoring (archive data) (p > 0.05). The paraesthesia, diplopia, enophthalmos and exophthalmos degree were measured in points. Results: In one year, the first and second groups had no differences in level of paraesthesia (p > 0.05). The absence of exophthalmos and differences between first and second groups, and between the third and the fourth groups with positive dynamics inside the groups were proved (p < 0.05). In the first and third groups, enophthalmos was absent, and it increased in the second and fourth groups (p < 0.01, p < 0.11). Diplopia in the first and third groups was absent, and it increased in the second and fourth groups (p < 0.05, p < 0.01). Conclusion: The elasticity and biocompatibility of titanium nickelide make the implant insertion and restoration of the lower orbital wall anatomy easier, with good postoperative clinical results.

Do orbital floor plates adequately protect against serious secondary injury?

Reconstruction of the orbital floor is common in cases of trauma and a variety of alloplastic materials, including titanium, can be used. However, we know of no reports about what happens to these materials if there is a second injury to the surgical site. This pilot study on six human cadavers (12 orbits) was therefore designed to investigate the possible outcomes should this occur. A "blowout fracture" was created in each orbit, which was then repaired using a preformed titanium implant. In two orbits, two implants were placed without fixation. The remaining implants were secured to the anterior orbital floor with a single screw, which was placed laterally or medially. A second impact sufficient to fracture the zygomaticomaxillary complex was then applied and its effect on the implants noted.

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.