Morphologic variations of the second cervical vertebra in Down syndrome compared with age-matched peers

Restricted access


Atlantoaxial instability is an important cause of pain and neurological dysfunction in patients with Down syndrome (DS), frequently requiring instrumented fusion of the upper cervical spine. This study provides a quantitative analysis of C2 morphology in DS patients compared with their peers without DS to identify differences that must be considered for the safe placement of instrumentation.


A retrospective chart review identified age-matched patients with and without DS with a CT scan of the cervical spine. Three-dimensional reconstructions of these scans were made with images along the axis of, and perpendicular to, the pars, lamina, facet, and transverse foramen of C2 bilaterally. Two of the authors performed independent measurements of anatomical structures using these images, and the average of the 2 raters’ measurements was recorded. Pedicle height and width; pars axis length (the distance from the facet to the anterior vertebral body through the pars); pars rostrocaudal angle (angle of the pars axis length to the endplate of C2); pars axial angle (angle of the pars axis length to the median coronal plane); lamina height, length, and width; lamina angle (angle of the lamina length to the median coronal plane); and transverse foramen posterior distance (the distance from the posterior wall of the transverse foramen to the tangent of the posterior vertebral body) were measured bilaterally. Patients with and without DS were compared using a mixed-effects model accounting for patient height.


A total of 18 patients with and 20 patients without DS were included in the analysis. The groups were matched based on age and sex. The median height was 147 cm (IQR 142–160 cm) in the DS group and 165 cm (IQR 161–172 cm) in the non-DS group (p < 0.001). After accounting for variations in height, the mean pars rostrocaudal angle was greater (50.86° vs 45.54°, p = 0.004), the mean transverse foramen posterior distance was less (−1.5 mm vs +1.3 mm, p = 0.001), and the mean lamina width was less (6.2 mm vs 7.7 mm, p = 0.038) in patients with DS.


Patients with DS had a steeper rostrocaudal trajectory of the pars, a more posteriorly positioned transverse foramen posterior wall, and a narrower lamina compared with age- and sex-matched peers. These variations should be considered during surgical planning, as they may have implications to safe placement of instrumentation.

ABBREVIATIONS DS = Down syndrome; ES = effect size.

Article Information

Correspondence G. Alexander Jones: Loyola University Medical Center, Maywood, IL.

INCLUDE WHEN CITING Published online November 23, 2018; DOI: 10.3171/2018.8.SPINE18750.

Disclosures Dr. Nockels: consultant for Medtronic. Dr. Jones: grant from Medtronic through Loyola University Medical Center for an unrelated research project, stock ownership in InVivo Therapeutics, and honorarium for the Chicago Review Course.

© AANS, except where prohibited by US copyright law.



  • View in gallery

    CT scan of the upper cervical spine demonstrating measurement of the dimensions and angles of the pars and pedicle. A: Midsagittal view through the atlas and axis, with line a representing the plane of the endplate of the axis. B: Sagittal view through the pars and pedicle of the axis, with line b representing the course of the pars and pedicle. The pars rostrocaudal angle is the angle between lines a and b. C: Axial view through the axis at the level of the pedicle. Line c represents the pars axis length. Line d represents the midline. The pars axial angle is the angle between lines c and d. D: View perpendicular to the pedicle. The pedicle height is line e and the pedicle width is line f. The transverse foramen (TF) and transverse process (TP) are also visible. E: Axial view with line g representing the plane of the image seen in panel D.

  • View in gallery

    CT scan of the upper cervical spine demonstrating measurement of dimensions and angle of the lamina. A: Axial view with line a being the lamina length and line b representing the midline. The lamina angle is the angle between lines a and b. B: View perpendicular to the lamina. Lamina height is line c and lamina width is line d. C: Axial view with line e representing the plane of the image seen in panel B.

  • View in gallery

    CT scan of the upper cervical spine demonstrating measurement of the transverse foramen position. Line a is tangent to the posterior wall of the vertebral body. Line b is the transverse foramen posterior distance, measured from the tangent line a to the posterior wall of the transverse foramen.



Ali FEAl-Bustan MAAl-Busairi WAAl-Mulla FAEsbaita EY: Cervical spine abnormalities associated with Down syndrome. Int Orthop 30:2842892006


Alvarez NRubin L: Atlantoaxial instability in adults with Down syndrome: a clinical and radiological survey. Appl Res Ment Retard 7:67781986


Bull MJ: Health supervision for children with Down syndrome. Pediatrics 128:3934062011


Cronk CCrocker ACPueschel SMShea AMZackai EPickens G: Growth charts for children with Down syndrome: 1 month to 18 years of age. Pediatrics 81:1021101988


Doyle JSLauerman WCWood KBKrause DR: Complications and long-term outcome of upper cervical spine arthrodesis in patients with Down syndrome. Spine (Phila Pa 1976) 21:122312311996


Dumitrescu AVMoga DCLongmuir SQOlson RJDrack AV: Prevalence and characteristics of abnormal head posture in children with Down syndrome: a 20-year retrospective, descriptive review. Ophthalmology 118:185918642011


El-Khouri MMourão MATobo ABattistella LRHerrero CFPRiberto M: Prevalence of atlanto-occipital and atlantoaxial instability in adults with Down syndrome. World Neurosurg 82:2152182014


Fleiss JL: The Design and Analysis of Clinical Experiments. New York: Wiley1986


Karaikovic EEDaubs MDMadsen RWGaines RW Jr: Morphologic characteristics of human cervical pedicles. Spine (Phila Pa 1976) 22:4935001997


McKay SDAl-Omari ATomlinson LADormans JP: Review of cervical spine anomalies in genetic syndromes. Spine (Phila Pa 1976) 37:E269E2772012


Martich VBen-Ami TYousefzadeh DKRoizen NJ: Hypoplastic posterior arch of C-1 in children with Down syndrome: a double jeopardy. Radiology 183:1251281992


Miller JDCapusten BMLampard R: Changes at the base of skull and cervical spine in Down syndrome. Can Assoc Radiol J 37:85891986


Nader-Sepahi ACasey ATHHayward RCrockard HAThompson D: Symptomatic atlantoaxial instability in Down syndrome. J Neurosurg 103 (3 Suppl):2312372005


Nakamura NInaba YAota YOba MMachida JAida N: New radiological parameters for the assessment of atlantoaxial instability in children with Down syndrome: the normal values and the risk of spinal cord injury. Bone Joint J 98-B:170417102016


Nakamura NInaba YOba MAota YMorikawa YAta Y: Novel 2 radiographical measurements for atlantoaxial instability in children with Down syndrome. Spine (Phila Pa 1976) 39:E1566E15742014


Pizzutillo PDHerman MJ: Cervical spine issues in Down syndrome. J Pediatr Orthop 25:2532592005


Pueschel SMScola FHTupper TBPezzullo JC: Skeletal anomalies of the upper cervical spine in children with Down syndrome. J Pediatr Orthop 10:6076111990


Rasmussen SAWhitehead NCollier SAFrías JL: Setting a public health research agenda for Down syndrome: summary of a meeting sponsored by the Centers for Disease Control and Prevention and the National Down Syndrome Society. Am J Med Genet A 146A:299830102008


Roy MBaxter MRoy A: Atlantoaxial instability in Down syndrome—guidelines for screening and detection. J R Soc Med 83:4334351990


Segal LSDrummond DSZanotti RMEcker MLMubarak SJ: Complications of posterior arthrodesis of the cervical spine in patients who have Down syndrome. J Bone Joint Surg Am 73:154715541991


Sherman SLAllen EGBean LHFreeman SB: Epidemiology of Down syndrome. Ment Retard Dev Disabil Res Rev 13:2212272007


Shikata JYamamuro TMikawa YIida HKobori M: Atlanto-axial subluxation in Down’s syndrome. Int Orthop 13:1871921989


Siemionow KChou D: To the occiput or not? C1-C2 ligamentous laxity in children with Down syndrome. Evid Based Spine Care J 5:1121182014


Siemionow KHansdorfer MJanusz PMardjetko S: Complications in adult patients with Down syndrome undergoing cervical spine surgery using current instrumentation techniques and rhBMP-2: A long-term follow-up. J Neurol Surg A Cent Eur Neurosurg 78:1131232017


Wakao NTakeuchi MNishimura MRiew KDKamiya MHirasawa A: Vertebral artery variations and osseous anomaly at the C1-2 level diagnosed by 3D CT angiography in normal subjects. Neuroradiology 56:8438492014


Xu RNadaud MCEbraheim NAYeasting RA: Morphology of the second cervical vertebra and the posterior projection of the C2 pedicle axis. Spine (Phila Pa 1976) 20:2592631995


Yamazaki MOkawa AHashimoto MAiba ASomeya YKoda M: Abnormal course of the vertebral artery at the craniovertebral junction in patients with Down syndrome visualized by three-dimensional CT angiography. Neuroradiology 50:4854902008


Zemel BSPipan MStallings VAHall WSchadt KFreedman DS: Growth charts for children with Down syndrome in the United States. Pediatrics 136:e1204e12112015




All Time Past Year Past 30 Days
Abstract Views 78 78 78
Full Text Views 24 24 24
PDF Downloads 26 26 26
EPUB Downloads 0 0 0


Google Scholar