A New Piece of the Puzzle to Understand Cervical Sagittal Alignment: Utilizing a Novel Angle δ to Describe the Relationship among T1 Vertebral Body Slope, Cervical Lordosis, and Cervical Sagittal Alignment.
Abstract
Cervical alignment has become increasingly important in the planning of spine surgery.
A relationship between the slope of T1 (T1S), the cervical lordosis (CL), and the
overall cervical sagittal vertical axis (cSVA) has previously been demonstrated, but
the exact nature of this relationship is poorly understood. In this study, we derive
theoretical and empirical equations to better understand how T1S and CL affect cSVA.
The first equation was developed on a theoretical basis using inherent trigonometric
relationships of the cervical spine. By treating the cervical spine as the arc of
a circumference, and by taking into account the cervical height (CH), the geometric
relationship between theT1S, CL, and cSVA was described via a trigonometric identity
utilizing a novel angle δ subtended by the CH and cSVA (δ = T1S-CL/2). The second
equation was developed on an empiric basis by performing a multiple linear regression
on data obtained from a retrospective review of a large multicenter deformity database.
The theoretical equation determined that the value of cSVA could be expressed as:
$cSVA\ = \ CH*{\rm{tan}}( {\pi /180*( {T1S - CL/2} )} )$. The empirical equation determined
that value of cSVA could be expressed as: $cSVA=({1.1*T1} )\ - ( {0.43*CL} ) + 6.69$.
In both, the sagittal alignment of the head over the shoulders is directly proportional
to the T1S and inversely proportional to CL/2. These 2 equations may allow surgeons
to better understand how the CL compensates for the T1S, to accurately predict the
postoperative cSVA, and to customize cervical interbody grafts by taking into consideration
each individual patient's specific cervical spine parameters.
Type
Journal articlePermalink
https://hdl.handle.net/10161/20367Published Version (Please cite this version)
10.1093/neuros/nyz088Publication Info
Goldschmidt, Ezequiel; Angriman, Federico; Agarwal, Nitin; Trevisan, Marcos; Zhou,
James; Chen, Katherine; ... International Spine Study Group (ISSG) (2020). A New Piece of the Puzzle to Understand Cervical Sagittal Alignment: Utilizing a Novel
Angle δ to Describe the Relationship among T1 Vertebral Body Slope, Cervical Lordosis,
and Cervical Sagittal Alignment. Neurosurgery, 86(3). pp. 446-451. 10.1093/neuros/nyz088. Retrieved from https://hdl.handle.net/10161/20367.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
Collections
More Info
Show full item recordScholars@Duke
Christopher Ignatius Shaffrey
Professor of Orthopaedic Surgery
I have more than 25 years of experience treating patients of all ages with spinal
disorders. I have had an interest in the management of spinal disorders since starting
my medical education. I performed residencies in both orthopaedic surgery and neurosurgery
to gain a comprehensive understanding of the entire range of spinal disorders. My
goal has been to find innovative ways to manage the range of spinal conditions, straightforward
to complex. I have a focus on managing patients with complex s

Articles written by Duke faculty are made available through the campus open access policy. For more information see: Duke Open Access Policy
Rights for Collection: Scholarly Articles
Works are deposited here by their authors, and represent their research and opinions, not that of Duke University. Some materials and descriptions may include offensive content. More info