title: Variability of the temporal bone surface's topography: implications for otologic surgery.
abstract: Otologic surgery is performed for a variety of reasons including treatment of recurrent ear infections, alleviation of dizziness, and restoration of hearing loss. A typical ear surgery consists of a tympanomastoidectomy in which both the middle ear is explored via a tympanic membrane flap and the bone behind the ear is removed via mastoidectomy to treat disease and/or provide additional access. The mastoid dissection is performed using a high-speed drill to excavate bone based on a pre-operative CT scan. Intraoperatively, the surface of the mastoid component of the temporal bone provides visual feedback allowing the surgeon to guide their dissection. Dissection begins in "safe areas" which, based on surface topography, are believed to be correlated with greatest distance from surface to vital anatomy thus decreasing the chance of injury to the brain, large blood vessels (e.g. the internal jugular vein and internal carotid artery), the inner ear, and the facial nerve. "Safe areas" have been identified based on surgical experience with no identifiable studies showing correlation of the surface with subsurface anatomy. The purpose of our study was to investigate whether such a correlation exists. Through a three-step registration process, we defined a correspondence between each of twenty five clinically-applicable temporal bone CT scans of patients and an atlas and explored displacement and angular differences of surface topography and depth of critical structures from the surface of the skull. The results of this study reflect current knowledge of osteogenesis and anatomy. Based on two features (distance and angular difference), two regions (suprahelical and posterior) of the temporal bone show the least variability between surface and subsurface anatomy.
authors.affiliation: Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: Jérémy
authors.initials: J
authors.lastname: Lecoeur
authors.forename: Jack H
authors.initials: JH
authors.lastname: Noble
authors.forename: Ramya
authors.initials: R
authors.lastname: Balachandran
authors.forename: Robert F
authors.initials: RF
authors.lastname: Labadie
authors.forename: Benoit M
authors.initials: BM
authors.lastname: Dawant
keywords: bone topography; otologic surgery; robotic surgery; temporal bone; universal stereotactic frame
references.citation: Otol Neurotol. 2010 Jan;31(1):94-9
references.pmid: 20019561
references.citation: Otol Neurotol. 2009 Jun;30(4):436-42
references.pmid: 19339909
references.citation: IEEE Trans Biomed Eng. 2011 Sep;58(9):2625-32
references.pmid: 21708495
references.citation: IEEE Trans Med Imaging. 2002 Feb;21(2):122-38
references.pmid: 11929100
references.citation: IEEE Trans Med Imaging. 2003 Nov;22(11):1470-9
references.pmid: 14606680
references.citation: IEEE Trans Biomed Eng. 2011 Oct;58(10):2904-10
references.pmid: 21788181
references.citation: Int J Med Robot. 2010 Sep;6(3):281-90
references.pmid: 20812268
references.citation: J Laryngol Otol. 1962 Sep;76:679-82
references.pmid: 13943318
references.citation: Med Phys. 2008 Dec;35(12):5375-84
references.pmid: 19175097