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Blunt forehead trauma and optic canal involvement: finite element analysis of anterior skull base and orbit on causes of vision impairment
  1. Heike Huempfner-Hierl1,
  2. Alexander Bohne1,
  3. Gert Wollny2,
  4. Ina Sterker3,
  5. Thomas Hierl1
  1. 1Department of Oral & Maxillofacial Plastic Surgery, Leipzig University Hospital, Leipzig, Germany
  2. 2Biomedical Imaging Technologies, ETSI Telecomunicación, Universidad Politécnica de Madrid, Madrid, Spain
  3. 3Department of Ophthalmology, Leipzig University Hospital, Leipzig, Germany
  1. Correspondence to Dr Heike Huempfner-Hierl, Department of Oral & Maxillofacial Plastic Surgery, Leipzig University Hospital, Liebigstr. 12, Leipzig 04103, Germany; Heike.Huempfner-Hierl{at}medizin.uni-leipzig.de

Abstract

Background Clinical studies report on vision impairment after blunt frontal head trauma. A possible cause is damage to the optic nerve bundle within the optic canal due to microfractures of the anterior skull base leading to indirect traumatic optic neuropathy.

Methods A finite element study simulating impact forces on the paramedian forehead in different grades was initiated. The set-up consisted of a high-resolution skull model with about 740 000 elements, a blunt impactor and was solved in a transient time-dependent simulation. Individual bone material parameters were calculated for each volume element to increase realism.

Results Results showed stress propagation from the frontal impact towards the optic foramen and the chiasm even at low-force fist-like impacts. Higher impacts produced stress patterns corresponding to typical fracture patterns of the anterior skull base including the optic canal. Transient simulation discerned two stress peaks equalling oscillation.

Conclusions It can be concluded that even comparatively low stresses and oscillation in the optic foramen may cause micro damage undiscerned by CT or MRI explaining consecutive vision loss. Higher impacts lead to typical comminuted fractures, which may affect the integrity of the optic canal. Finite element simulation can be effectively used in studying head trauma and its clinical consequences.

  • Orbit
  • Trauma
  • Optic Nerve

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