Magnetic resonance versus computed tomography: imaging bony fractures of the orbit with view to surgical reconstruction — a retrospective feasibility study

77 A three-dimensional method of assessing the outcome of orbital reconstruction after trauma E. Brouns ∗ , M. Vehmeijer, N. Liberton, M. van Eijnatten, T. Forouzanfar Department of Oral and Maxillofacial Surgery/3D Innovationlab VU University Medical Center, Amsterdam, The Netherlands Background and Objective: Orbital blow-out fractures are commonly a result of motor vehicle accidents, interpersonal violence, or sports injuries and often require reconstructive surgery. A plethora of different surgical approaches are currently used in orbital floor reduction. These include transconjunctival, subciliary, mid-lower eyelid, infraorbital and, more recently, endoscopic transantral approaches. Some of the aforementioned treatment strategies are combined with additional measures like intraoperative imaging or navigation to enhance the accuracy hence surgical outcome. The current treatment method at the VU University Medical Center consists of a combination of virtual preoperative planning and three-dimensional (3D) printing. This novel approach has resulted in very good “subjective” clinical outcomes. However, an “objective” method of assessing the outcome of orbital reconstructions after trauma is still sought. Methods: To date, 15 patients have been operated using the aforementioned method. In order to assess the overall accuracy and the outcome of the orbital floor operation, virtually planned STL models were compared with the postoperative STL models of three patients. This presentation will describe all steps required to objectively assess the outcome of orbital reconstruction after trauma. Findings: The proposed 3D method demonstrated a strong agreement between the virtually planned and the resulting orbital floor reduction. This novel strategy offers a possible alternative to intraoperative CT and navigation in the treatment of orbital floor patients. Conclusions: Pre- and postoperative STL models can be used to evaluate the accuracy of orbital floor reconstructions after trauma. http://dx.doi.org/10.1016/j.ijom.2017.02.276 Magnetic resonance versus computed tomography: imaging bony fractures of the orbit with view to surgical reconstruction — a retrospective feasibility study T. Cooper ∗ , B. Schmutz, E. Hsu, A. Lynham University of Queensland, Queensland, Australia Objective: To examine the disparity between orbital fractures imaged with magnetic resonance (MR) versus those imaged with computed tomography (CT) using virtual segmentation and threedimensional (3D) modelling. Methods: Data from a previous study involving patients with suspected unilateral orbital fracture recruited from Royal Brisbane and Women’s Hospital Maxillofacial Surgery clinics was used. The primary predictor variable was the imaging technique (MR versus CT) and the secondary predictor variable was type of fracture (orbital blowout versus zygomaticomaxillary complex [ZMC]). Outcome measurements were average deviation of fracture margins and greatest deviation of fracture margins as defined on MR and CT based virtual 3D models.

Findings: Of the cases made available three were ZMC fractures and seven were blowout orbital fractures (n = 10). Defect margins mapped from MR exhibited an average of 1.24 mm deviation from CT overall and an average greatest deviation of 3.10 mm. Blowout fractures (n = 7) exhibited an overall average deviation of 0.85 mm and average greatest deviation of 2.01 mm. ZMC fractures (n = 3) exhibited an overall average deviation of 2.14 mm and average greatest deviation of 5.64 mm. There was a significant difference between blowout and ZMC fractures average deviation (0.85 mm versus 2.14 mm, P < 0.01). Conclusion: Orbital blowout fractures can be defined on MR with clinically acceptable accuracy as evidenced by the overall average deviation of 0.85 mm. The same cannot be said for ZMC fractures. MR should be considered as an alternative imaging modality for orbital blowout fracture when the risks of CT are clinically significant. http://dx.doi.org/10.1016/j.ijom.2017.02.277 Meta-analysis of orbitozygomatic complex trauma. The cost–benefit relationship for the usefulness of eye care and orthoptic screening S. Crimi ∗ , A. Calvo, M. Sergiampietri, E. Nastro, F.S. De Ponte Maxillofacial Unit, G.Martino Policlinic Hospital, University of Messina, Italy Objectives: The aim of the study is to demonstrate the importance of the ophthalmologic and orthoptic evaluation in the management of the orbitozygomatic complex fractures in both stages: immediately and in the postoperative follow-up. Methods: The ophthalmologic and orthoptic assessment at the “Time 0” (acute) and distance can have indeed a double advantage: from a clinical point of view to have objective data on the outcome of the surgery and from an ethical point of view to improve the “concordance” of the patient, showing him the outcome of the situation pre- and postsurgery. Only in 2015, 81 patients have been hospitalised, 74 of whom underwent surgery. In particular 40 fractures COMZ (54%), 23 fractures of the orbital floor (31%), 4 fractures interesting only the medial wall (5%), 1 NOE fracture (2%), 6 fractures Le Fort (8%). Results: All patients were studied clinically and functionally with Hess-Lancaster screen before and after the surgery. Seven patients have been managed conservatively for the absence of symptoms and signs of ocular movements involvement detected by Lancaster screen. Three patients still present diplopia. Conclusions: A thorough clinical study of ophthalmologic and orthoptics evaluation with Hess-Lancaster screen in the pre- and postoperative appear so necessary both in the indication of surgical timing, both in identifying the presence or onset of diplopia appear useful in order to establish needs and timing of surgical treatment. Advantage of Hess Lancaster screen is the capability to quantify through numerical parameters the entity of ocular impairment and help the clinician in order to treat and follow such patients in a correct way. http://dx.doi.org/10.1016/j.ijom.2017.02.278