Radiographic Mensuration
Sagittal Vertical Axis (SVA)	The standard measurement of sagittal balance uses the center of the body of C7 as the measuring point for a vertical line that is perpendicular to the ground. The posterior–superior edge of S1 is also used as a second measuring point for a vertical line. The distance between these two lines constitutes the sagittal vertical axis (SVA).	Knott PT, Mardjetko SM, Techy F. The use of the T1 sagittal angle in predicting overall sagittal balance of the spine. Spine J. 2010;10(11):994–8. [99]
Cervical 7 Plumbline (C7-P)	The C7 plumbline is a radiographic reference to determine the sagittal vertical axis, the most traditional measurement of sagittal balance of the spine. A vertical line is drawn from the center of the C7 vertebral body in a caudal direction. The line should connect with or be within 5 mm of the superior–posterior endplate of S1.	Kim D, Davis DD, Menger RP. Spine Sagittal Balance. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534858/# (accessed on 18 November 2022)
Cervical Lordosis (CL) Cobb Method	Measured commonly with the Cobb Angle Method, which utilizes the superior endplate of C3 and inferior endplate of C7 as references for determining sagittal alignment. A line is drawn along the superior endplate of the superior end vertebra C3 and a second line is drawn along the inferior endplate of the inferior end vertebra C7. The acute angle formed by perpendicular lines drawn from the superior and inferior endplates of the two end vertebrae on a lateral radiograph is the angle of sagittal alignment.	Silber JS, Lipetz JS, Hayes VM, Lonner BS. Measurement variability in the assessment of sagittal alignment of the cervical spine: a comparison of the Gore and Cobb methods. J Spinal Disord Tech. 2004 Aug;17(4):301–5. [115]
Cervical Lordosis (CL) Gore Method	The Gore Method relies on the posterior vertebral body as the referencing landmark.1 The posterosuperior and posteroinferior vertebral body endpoints are marked, and the line connecting these two points represents the posterior vertebral body line. Lines are drawn paralleling the posterior vertebral body line of the two end vertebrae (C3 and C7), and the acute angle formed by the intersection of these lines is the angle (°) of sagittal alignment.	Silber JS, Lipetz JS, Hayes VM, Lonner BS. Measurement variability in the assessment of sagittal alignment of the cervical spine: a comparison of the gore and cobb methods. J Spinal Disord Tech. 2004 Aug;17(4):301–5. [115]
Cervical Lordosis (CL) Harrison Posterior Tangent Method	The Harrison Posterior Tangent Method relies on lines being drawn along the posterior vertebral body margins from C2 to C7, whereas the posterior tangents are the slopes along the curve.	Harrison DE, Harrison DD, Cailliet R, Troyanovich SJ, Janik TJ, Holland B. Cobb method or Harrison posterior tangent method: which to choose for lateral cervical radiographic analysis. Spine (Phila Pa 1976). 2000 Aug 15;25(16):2072-8. doi: 10.1097/00007632-200008150-00011. PMID: 10954638.
Thoracic Kyphosis (TK)	Thoracic kyphosis is measured between the upper T1 endplate and the lower T12 endplate. However, many articles measure thoracic kyphosis between T4 and T12 because of the poor quality of normal radiographs due to the superposition of the humeral heads.	J. C. Le Huec, W. Thompson, Y. Mohsinaly, C. Barrey, and A. Faundez. Sagittal balance of the spine, European Spine Journal volume 28, pages 1889–1905 (2019)
Thoracic Inlet Angle (TIA)	The TIA is formed when the T1 vertical line of the upper endplate (from the center of the T-1 upper endplate) meets with the line formed between the upper end of the manubrium and the center of the T-1 upper endplate.	Sun J, Zhao HW, Wang JJ, Xun L, Fu NX, Huang H. Diagnostic Value of T1 Slope in Degenerative Cervical Spondylotic Myelopathy. Med Sci Monit Int Med J Exp Clin Res. 2018 Feb 7;24:791–6. [5]
T1 Slope (T1S)	The T1 slope is the angle formed by drawing a line along the superior endplate of T1 and the horizontal reference line at the median sagittal cervical vertebra from the CT radiographs.	Sun J, Zhao HW, Wang JJ, Xun L, Fu NX, Huang H. Diagnostic Value of T1 Slope in Degenerative Cervical Spondylotic Myelopathy. Med Sci Monit Int Med J Exp Clin Res. 2018 Feb 7;24:791–6. [5]
Pelvic Tilt (PT)	The angle between two of the following radiographic lines: a line from the center of the S1 endplate to the center of the femoral head and a vertical line drawn intersecting the center of the femoral head.	Kim D, Davis DD, Menger RP. Spine Sagittal Balance. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534858/# (accessed on 18 November 2022)
Pelvic Incidence (PI)	PI is defined as the angle between a line drawn perpendicularly to the surface of the superior endplate of the sacrum and a line connecting the midpoint of the superior endplate of the sacrum to the center of the femoral head.	Kim D, Davis DD, Menger RP. Spine Sagittal Balance. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
Sacral Slope (SS)	The angle between the sacral endplate and a line horizontal to the ground.	Mendoza-Lattes S, Ries Z, Gao Y, Weinstein SL. Natural history of spinopelvic alignment differs from symptomatic deformity of the spine. Spine. 2010 Jul 15;35(16):E792–798.
Lumbar Lordosis (LL)	The lumbar lordosis (LL) according to Roussouly is measured between the points of inflection from the lumbar lordosis to the thoracic kyphosis and the upper S1 endplate.	J. C. Le Huec, W. Thompson, Y. Mohsinaly, C. Barrey and A. Faundez. Sagittal balance of the spine, European Spine Journal volume 28, pages 1889–1905 (2019)
Lumbar Lordosis (LL) Harrison Posterior Tangent Method	Alternatively, lumbar lordosis can be measured utilizing the Harrison Posterior Tangent Method from L1 to L5, also known as Absolute Rotation Angle (ARA).	Tadeusz J Janik, Donald D. Harrison, Rene Cailliet, Stepah J. Troyanovich, Deed Harrison. Can the Sagittal Lumbar Curvature be Closely Approximated by an Ellipse? Journal of Orthopedic Research Vol. 16, No. 6 1998, p. 766–770 The Journal of Bone and Joint Surgery Inc.