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. 2021 Oct;11(8):1307-1312.
doi: 10.1177/2192568220972076. Epub 2020 Nov 18.

Cervical Spine Alignment in the Sagittal Axis: A Review of the Best Validated Measures in Clinical Practice

Michael L Martini  1 , Sean N Neifert  1 , Emily K Chapman  1 , Thomas E Mroz  2 , Jonathan J Rasouli  2
Affiliations

Cervical Spine Alignment in the Sagittal Axis: A Review of the Best Validated Measures in Clinical Practice

Michael L Martini et al. Global Spine J. 2021 Oct.

Abstract

Study design: Review of the best-validated measures of cervical spine alignment in the sagittal axis.

Objective: Describe the C2-C7 Cobb Angle, C2-C7 sagittal vertical axis, chin-brow to vertical angle, T1 slope minus C2-C7 lordosis, C2 slope, and different types of cervical kyphosis.

Methods: Search PubMed for recent technical literature on radiograph-based measurements of the cervical spine.

Results: Despite the continuing use of measures developed many years ago such as the C2-C7 Cobb angle, there are new radiographic parameters being published and utilized in recent years, including the C2 slope. Further research is needed to compare older and newer measures for cross-validation. Utilizing these measures to determine the degree of correction intraoperatively and postoperatively will enable surgeons to optimize patient-level outcomes.

Conclusion: Cervical spinal deformity can be a debilitating condition characterized by cervical spinal misalignment that affects the elderly more commonly than young populations. Many of these validated measures of cervical spinal alignment are useful in clinical settings due to their ease of implementation and correlations with various postoperative and health-related quality of life outcomes.

Keywords: C2 slope; T1 slope; cervical spinal deformity; cobb angle; horizontal gaze; kyphosis; lordosis; sagittal vertical axis.

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Conflict of interest statement

Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Lateral cervical radiograph demonstrating satisfactory lordotic alignment with mild-moderate degenerative disc disease, most notable at C5-6.
Figure 2.
Figure 2.
C2-7 Cobb Angle. Lateral cervical radiograph demonstrating the measurement of C2-7 Cobb Angle. The Cobb angle is obtained by drawing parallel lines extending from the lower endplate of the most superior vertebral level (C2) and the lower endplate of the most inferior vertebral level (C7). Perpendicular lines are then drawn from the parallel lines, and the angle of their intersection is equal to the Cobb angle.
Figure 3.
Figure 3.
C2-7 Sagittal Vertical Axis (SVA) is calculated by measuring the horizontal distance between the posterosuperior corner of the C7 vertebral body and a plumb line drawn from the centroid of C2. In general, C2-7 SVA < 4 centimeters is considered to be normal.
Figure 4.
Figure 4.
Chin-Brow Vertical Angle (CBVA) is determined by measuring a line drawn from the patient’s chin to their brow and taking the angle between this line and a vertical line drawn perpendicular to the ground. As such, tilting the head down so that the gaze is toward the floor produces a positive CBVA, while tilted the head up produces a negative CBVA. When the head is in a neutral position with the chin-brown line perpendicular to the floor, the CBVA is zero degrees.
Figure 5.
Figure 5.
(A) C2 slope is measured on lateral radiograph by drawing a line parallel to the C2 lower endplate and taking the angle between this line and the horizontal plane. (B) In comparison to the patient in Figure 5(A), this patient, with C2-7 SVA > 4 centimeters and abnormal CBVA, the C2 slope is markedly elevated.
See this image and copyright information in PMC

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