Petrous Bone Fracture: A Virtual Trauma Analysis *†Marion Montava, †Arnaud Deveze, *Pierre-Jean Arnoux, ‡Samuel Bidal, *Christian Brunet, and †Jean-Pierre Lavieille *Laboratoire de Biome ´canique Applique ´e, Aix-Marseille University; ÞDepartment of Otolaryngology, University Hospital Nord, Assistance Publique Ho ˆ pitaux de Marseille; and þAltair Development France, Marseille, France Objective: The temporal bone shields sensorineural, nervous, and vascular structures explaining the potential severity and complications of trauma related to road and sport accidents. So far, no clear data are available on the exact mechanisms in- volved for fracture processes. Modelization of structures helps to answer these concerns. Our objective was to design a finite element model of the petrous bone structure to modelize tem- poral bone fracture propagation in a scenario of lateral impact. Materials and Methods: A finite element model of the petrous bone structure was designed based on computed tomography data. A 7-m/s lateral impact was simulated to reproduce a typical lateral trauma. Results of model analysis was based on force re- corded, stress level on bone structure up to induce a solution of continuity of the bony structure. Results: Model simulation showed that bone fractures follow the main axes of the petrous bone and occured in a 2-step process: first, a crush, and second, a massive fissuration of the petrous bone. The lines of fracture obtained by simulation of a lateral impact converge toward the middle ear region. This longitudinal fracture is located at the mastoidYpetrous pyramid junction. Discussion: Using this model, it was possible to map petrous bone fractures including fracture chronology and areas of fu- sion of the middle ear region. This technique may represent a first step to investigate the pathophysiology of the petrous bone fractures, aiming to define prognostic criteria for patients’ care. Key Words: BiomechanicVFinite element modelingVPetrous boneVTemporalVVirtual trauma. Otol Neurotol 33:651Y654, 2012. Petrous bone fractures occur during craniocerebral trauma of variable severity (1,2). Head injury with petrous bone fracture is frequent and directly related to the development of modern human activity: motor vehicle accidents (cars, motorcycles, and bicycles), sports injuries (skiing, moun- tain bikes), home and work accidents, assaults, gun shot wounds, and complications of medical conditions (syncope, convulsions, altered vision, and other causes of falls among elderly subjects) (2Y5). Approximately 30% of head trauma victims receive cranial fractures, and 18% of cranial frac- tures involve the temporal bone (6). The intensity of the craniocerebral trauma and the pre- sence of neurovascular structures within the petrous bone structure (facial nerve, vestibular labyrinth, cochlea, and internal carotid artery) explain the seriousness and com- plexity of petrous bone fracture symptoms. Early diag- nostic is necessary as the prognosis for hearing function and facial nerve impairment depends on the time before care is provided (1,4,7). Temporal bone fractures are classified as longitudinal, transverse, or mixed, depending on their trajectories with regard to the petrous pyramid ridge. Longitudinal frac- tures, the most common (70%Y90 %), are defined as frac- tures running parallel to the petrous ridge and are usually the result of a temporal or parietal impact to the head. Transverse fractures (10%Y30%) are defined as fractures coursing perpendicular to the petrous ridge and are usually the result of an occipital or frontal impact to the head. Mixed fractures are defined as those with both longitudi- nal and transverse components (4,8,9). High-resolution computed tomography (CT) with bone windows is the imaging technique of choice to assess tem- poral bone involvement in head traumas (10). To complete the analysis of the radiological data and specify the injury, digital simulation tools can simulate trauma conditions and, through calculations, can follow the entire trauma chronol- ogy. Many finite element models have been developed in Address correspondence and reprint requests to Marion Montava, M.D., Laboratoire de Biome ´canique Applique ´e, UMR T 24 IFSTTAR, Aix-Marseille Univ, Boulevard Pierre Dramard, 13916 Marseille Cedex 20, France; E-mail: marion.montava@mail.ap-hm.fr Financing of the work: Fondation des Gueules Casse ´esYDossier 21- 2009 The authors disclose no conflicts of interest. Otology & Neurotology 33:651Y654 Ó 2012, Otology & Neurotology, Inc. 651 Copyright © 2012 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.