title: Radiographic and Magnetic Resonance Imaging Identification of Thoracolumbar Spine Variants with Implications for the Positioning of the Conus Medullaris in Rhesus Macaques.
abstract: The anatomy of the vertebral column in mammals may differ between species and between subjects of the same species, especially with regards to the composition of the thoracolumbar spine. We investigated, using several noninvasive imaging techniques, the thoracolumbar spine of a total of 44 adult rhesus macaques of both genders. Radiographic examination of the vertebral column showed a predominant spine phenotype with 12 rib-bearing thoracic vertebrae and 7 lumbar vertebrae without ribs in 82% of subjects, whereas a subset of subjects demonstrated 13 rib-bearing thoracic vertebrae and 6 lumbar vertebrae without ribs. Computer tomography studies of the thoraco-lumbar spine in two cases with a pair of supernumerary ribs showed facet joints between the most caudal pair of ribs and the associated vertebra, supporting a thoracic phenotype. Magnetic resonance imaging (MRI) studies were used to determine the relationship between the lumbosacral spinal cord and the vertebral column. The length of the conus medullaris portion of the spinal cord was 1.5 ± 0.3 vertebral units, and its rostral and caudal positions in the spinal canal were at 2.0 ± 0.3 and 3.6 ± 0.4 vertebral units below the thoracolumbar junction, respectively (n = 44). The presence of a set of supernumerary ribs did not affect the length or craniocaudal position of the conus medullaris, and subjects with13 rib-bearing vertebrae may from a functional or spine surgical perspective be considered as exhibiting12 thoracic vertebrae and an L1 vertebra with ribs. Anat Rec, 300:300-308, 2017. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, California.|Department of Clinical Neuroscience, Divisions of Neurosurgery and Neuroradiology, Karolinska Institute, Stockholm, Sweden.
authors.forename: Marcus
authors.initials: M
authors.lastname: Ohlsson
authors.affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Jaime H
authors.initials: JH
authors.lastname: Nieto
authors.affiliation: California National Primate Research Center, UC Davis, Davis, California.
authors.forename: Kari L
authors.initials: KL
authors.lastname: Christe
authors.affiliation: Department of Radiology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: J Pablo
authors.initials: JP
authors.lastname: Villablanca
authors.affiliation: Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Leif A
authors.initials: LA
authors.lastname: Havton
mesh_terms: D000818:Animals; D005260:Female; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008253:Macaca mulatta; D008279:Magnetic Resonance Imaging; D008297:Male; D012272:Ribs / Q000000981:diagnostic imaging*; D013116:Spinal Cord / Q000000981:diagnostic imaging*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
keywords: computed tomography; lumbar rib; nonhuman primate; noninvasive imaging; supernumerary rib