Gaurav K. Thawait MD, Presenter: Nothing to Disclose

Shrey Kumar Thawait MD, Abstract Co-Author: Nothing to Disclose

Avneesh Chhabra MD, Abstract Co-Author: Research grant, Siemens AG Research Consultant, Siemens AG Research grant, Integra LifeSciences Holdings Corporation Research grant, General Electric Company

Laura Marie Fayad MD, Abstract Co-Author: Fellowship funded, General Electric Company Fellowship funded, Siemens AG

John A. Carrino MD, MPH, Abstract Co-Author: Research grant, Siemens AG Research grant, Carestream Health, Inc Research Consultant, General Electric Company

A paucity of information exists about the frequency and spectrum of vertebral level variants. Our goal was to determine the prevalence of spinal segmental variants in a non-symptomatic convenience sample.

IRB approval was obtained for this HIPAA-compliant retrospective study. Whole body isotropic computed tomography imaging with multi-planar reconstructions of 300 patients with no established diagnosis of neck, dorsum or back pain were reviewed. Total and segmental vertebral numbering was accomplished by counting from C2 to the sacrum. The presence of cervical ribs, thoracolumbar transitional vertebra (TLTV) and lumbosacral transitional vertebra (LSTV) was documented. Transitional vertebra was defined as the vertebra that retains features of the segment above and below it. LSTVs were subtyped by the Castellvi classification.

Total presacral segment distributions were: 23 in 2.3% (7/300), 24 in 91.7% (275/300) and 25 in 6% (18/300). Segmental vertebral distributions were : C7/T12/L4 = 0.3% (1/300), C7/T12/L5 = 89.7% (269/300), C7/T12/L6 = 3.7% (11/300), C7/T13/L4 = 2.3% (7/300), C7/T11/L5 = 0.3% (1/300), C7/T11/L6 =0.7% (2/300) , C7/T13/L5 = 2.7% (8/300), and C7/T13/L6 = 0.3% (1/300). Cervical ribs were present in 5% (15/300). TLTV were present in 14.3% (43/300). LSTV were present in 29.3% (88/300). LSTV subtypes were: Type Ia (unilateral dysplastic transverse process) = 4.3% (13/300), Type Ib (bilateral dysplastic transverse processes) = 2.3% (7/300), Type IIa (incomplete unilateral lumbarization/sacralization with diarthrodial joint) = 6% (18/300), Type IIb (incomplete bilateral lumbarization/sacralization with diarthrodial joint) = 9.7% (29/300), Type IIIa (unilateral lumbarization/sacralization with osseous fusion) = 1% (3/300), Type IIIb (bilateral lumbarization/sacralization with osseous fusion) = 4% (12/300) and Type IV (unilateral type II with a type III on the contralateral side) = 2% (6/300).

This study provides a first approximation for the prevalence of spinal segmental variability. Deviation from the typical total and segmental distribution is not infrequent and transitional situations are common.

The substantial variability of spine segmental anatomy may confound spine imaging interpretation with regards to ascribing vertebral levels which may provide a detailed insight to radiologists.

Thawait, G, Thawait, S, Chhabra, A, Fayad, L, Carrino, J, An Epidemiological Imaging Study of Spinal Segment Variants in a Nonsymptomatic Population.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034320.html