Common Radiographic Measurements

Dustin H. Massel, Benjamin C. Mayo, William W. Long, Krishna D. Modi, and Kern Singh

9.1 Radiographic Measurements

9.1.1 Cervical Measurements (Fig 9.1, Table 9.1)

Cervical Lordosis

• Measured via a lateral radiograph.

• May be referred to as a C2–C7 Cobb angle.

Fig. 9.1. Normal cervical lordosis. Line A: drawn in an anteroposterior (AP) direction at the superior end plate of C2. Line B: drawn in an AP direction at the inferior endplate of C7. Line C: drawn in an inferior direction, perpendicular to line A. Line D: drawn in a superior direction, perpendicular to line B. Angle X, measured between lines C and D, represents cervical lordosis.

Table 9.1 Normal cervical spine curvature measurements (Fig. 9.1)

Spine region	Curvature	Measurements
Cervical	Hypolordosis	< 20 degrees
	Lordosis	20–40 degrees
	Hyperlordosis	> 40 degrees

9.1.2 Thoracic Measurements (Fig 9.2, Table 9.2)

Thoracic Kyphosis

• Measured via a lateral radiograph.

9.1.3 Lumbar Measurements (Fig 9.3, Table 9.3)

Lumbar Lordosis

• Measured via a lateral radiograph.

• May be referred to as a L1–L5 Cobb angle.

9.1.4 Cobb Angle (Fig 9.4)

• Quantifies magnitude of spinal deformities (e.g., scoliosis).

– Cobb angle ≥ 10 degrees = scoliosis.

For more information on scoliosis, see Chapter 12.

Fig. 9.2 Thoracic kyphosis. (a) Normal thoracic kyphosis. (b) Thoracic hyperkyphosis. Line A: drawn in an anteroposterior (AP) direction at the superior endplate of T4. Line B: drawn in an AP direction at the inferior end plate of T12. Line C: drawn in an inferior direction, perpendicular to line A. Line D: drawn in a superior direction, perpendicular to line B. Angle X, measured between lines C and D, represents thoracic kyphosis.

Table 9.2 Normal thoracic spine curvature measurements (Fig. 9.2)

Spine region	Curvature	Measurements
Thoracic	Hypokyphosis	< 20 degrees
	Kyphosis (Fig. 9.2a)	20–45 degrees (average 35 degrees)
	Hyperkyphosis (Fig. 9.2b)	> 45 degrees

Fig. 9.3 Normal lumbar lordosis. Line A: drawn in an anteroposterior (AP) direction at the superior endplate of L1. Line B: drawn in an AP direction at the inferior end plate of L5. Line C: drawn in an inferior direction, perpendicular to line A. Line D: drawn in a superior direction, perpendicular to line B. Angle X, measured between lines C and D, represents lumbar lordosis.

Table 9.3 Normal lumbar spine curvature measurements (Fig. 9.3)

Spine region	Curvature	Measurements
Lumbar	Hypolordosis	< 40 degrees
	Lordosis	40–60 degrees
	Hyperlordosis	> 60 degrees

9.1.5 Coronal Balance (Fig 9.5, Table 9.4)

• Radiograph read as if patient standing with back to you (R on R, L on L).

• C7 plumb line (C7PL) = used as a reference to measure displacement of the vertebral bodies from each other and from midline (based on distance from the central sacral vertical line [CSVL]).

• Coronal compensation = C7 vertebral body directly above the S1 vertebral body (despite abnormal spinal curvature).

• Coronal decompensation = C7 vertebral body laterally displaced from above the S1 vertebral body.

9.1.6 Sagittal Vertical Axis (Fig 9.6, Table 9.5)

• Measured via a lateral radiograph.

• Used for cervical sagittal vertical axis (CSVA) or global spine (SVA) measurements.

• C2 plumb line (C2PL) = used as a reference to measure displacement of the cervical vertebral bodies from each other and from midline in a sagittal plane:

– Primary measure of cervical sagittal alignment.

Fig. 9.4 Cobb’s angle. Define upper and lower vertebral levels associated with curvature/deformity. Line A: drawn in an anteroposterior (AP) direction at the superior end plate of the upper vertebral level associated with curvature/deformity. Line B: drawn in an AP direction at the inferior end plate of the lower vertebral level associated with curvature/deformity. Line C: drawn in an inferior direction, perpendicular to line A. Line D: drawn in a superior direction, perpendicular to line B. Angle X, measured between lines C and D, represents Cobb’s angle.

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