Lateral Cervical Calculations
% CDL< :: Condylar Angle (deg)
Angle of the occiput plane line to a true horizontal. This angle is used as a reference for placement of the patient prior to a neutral x-ray. Neutral placement position is approximately 30 degrees in extension.
Method: Point 1 is the intersection of anterior occipital condyle and skull. Point 2 is the intersection of posterior occipital condyle and skull. Points 1 and 2 are located and a line is drawn through these points. The angle of this line (the occiput plane line) to a true horizontal is the condylar angle.
CB: The Clinical Biomechanical Significance of this measure stems from the fact that it is used to position a patient prior to a neutral x-ray.
% C1< :: C1 Angle (deg) (SSU)
Angle of the atlas plane line to a true horizontal. Neutral position is approximately 27.3 degrees in extension.
Method: Bisect the vertical distance of the anterior arch of the atlas. Point 1 is the point of bisection. Next, bisect the vertical distance of the posterior arch.
Point 2 is the point of this bisection. Draw a line through points 1 and 2. The angle of this line (the atlas plane line) to a true horizontal is the C1 angle.
CB: An increased angle indicates fixed extension of C1 and posterior displacement of the head weight.
A decreased angle indicates fixed flexion of C1 and anterior displacement of the head weight.
% CDL/C1< :: Condylar/C1 Angle (deg) (SSU)
Angle of the occiput plane line to the atlas plane line. Neutral position is approximately 2.5 degrees in extension.
CB: Diminished or reversed angulation is suggestive of fixed flexion of the occiput and anterior displacement of the head weight.
Increased angulation indicates fixed extension of the occiput and posterior displacement of the head weight.
% C2< :: C2 Angle (deg) (SSU)
Angle of C2 to a true horizontal using perpendicular to posterior C2 body.
Neutral position is approximately 9.1 degrees in extension.
Method: Point 1 is the pedicle junction on the superior posterior C2 body. Point 2 is inferior posterior C2 body. Points 1 and 2 are located and a line is drawn through these points. A second line is drawn perpendicular to the first. The angle of this second line to a true horizontal is the C2 angle.
CB: Decreased angle causes anterior displacement of the head weight, loss of upper cervical curve and anterior weight bearing to the entire cervical curve.
Increased angle causes posterior displacement of the head weight, increase in the upper cervical curve and increased loading to the posterior pillar.
% C1/C2< :: C1/C2 Angle (deg) (SSU)
Angle of the atlas plane line to the C2 body perpendicular. Neutral position is approximately 17.9 degrees in extension.
CB: An increased angle indicates C1 fixed in extension and posterior displacement of the head weight.
A decreased angle indicates C1 fixed in flexion and anterior displacement of the head weight.
% Rc :: Radius of Curvature, Overall (cm)
The radius is a measure of the cervical curvature using three points located on C2, C5 and C7.
CB: A loss of curvature (increased radius of curvature; hypolordotic), in combination with fixed regional flexion, results in increased loading to the anterior pillar. Anterior loading is a causative factor in accelerated anterior pillar (disc and vertebral body) degeneration. Anterior loading results in separation of the posterior (facet) joints leading to hypermobility.
A gain of curvature (decreased radius of curvature; hyperlordotic), in combination with fixed regional flexion, causes increased loading onto the posterior pillar (facet joints). Posterior loading causes facet jamming and hypomobility.
% Rc I :: Radius of Curvature, Ideal (cm)
In the neutral position, the ideal radius is equal to the distance between anterior C1 (anterior point of the atlas plane line) and the posterior superior T2 body.
% Rc Up :: Radius of Curvature, Upper (cm)
The radius of curvature of the upper cervical curve is measured using three points located on C2, C3, C4. The upper radius is compared to the ideal and overall radii. When the cervical curve is coherent, the upper radius approximates the overall radius of curvature. A difference of the upper and lower radii to the overall radius is suggestive of ligamentous disruption or dysfunction.
CB: An increased radius of curvature (hypolordosis) causes increased loading to the anterior pillar, particularly in the presence of fixed flexion of the centerline angle.
A decreased radius of curvature (hyperlordosis) causes increased loading to the posterior pillar. Abnormal facet loading occurs with a non coherent curve, particularly in the presence of fixed extension of the centerline angle.
% Rc Lo :: Radius of Curvature, Lower (cm)
The radius of curvature of the lower cervical curve is measured using three points located on C5, C6, C7. The lower radius is compared to the ideal and overall radii. When the cervical curve is coherent the lower radius approximates the overall radius of curvature. A difference of the upper and lower radii to the overall radius is suggestive of ligamentous disruption or dysfunction.
CB: An increased radius of curvature (hypolordosis) causes increased loading to the anterior pillar, particularly in the presence of fixed flexion of the centerline angle.
A decreased radius of curvature (hyperlordosis) causes increased loading to the posterior pillar. Abnormal facet loading occurs with a non coherent curve, particularly in the presence of fixed extension of the centerline angle.
% CL
The centerline angle of the radius of curvature is a measure of fixed extension or flexion of the cervical curve.
Method: A circular arc is drawn through three points located on C2, C5, and C7 (see “Radius of Curvature, Overall” above). A horizontal line is drawn through the middle of the C4/C5 disc space. The centerline itself is drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL
CB: Fixed flexion of the centerline angle results in anterior weight bearing of the skull throughout the entire cervical curve with maximum torsional loading at C7/T1. The head and neck extensors are in chronic reactive contraction and fatigue.
Fixed extension of the centerline angle results in increased posterior pillar loading.
% CL
The centerline angle of the upper radius of curvature is a measure of fixed extension or flexion of the upper cervical curve.
Method: A circular arc is drawn through three points located on C2, C3, and C4 (see “Radius of Curvature, Upper” above). A horizontal line is drawn through the middle of the C4/C5 disc space. The centerline itself is drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL
CB: Fixed flexion results in increased loading to the anterior pillar, adaptive C2 flexion and reactive C1 extension. The head and neck extensors are in chronic reactive contraction.
Fixed extension results in posterior weight bearing of the head with increased posterior pillar loading.
% CL
The centerline angle of the lower radius of curvature is a measure of fixed extension or flexion of the lower cervical curve.
Method: A circular arc is drawn through three points located on C5, C6, and C7 (see “Radius of Curvature, Lower” above). A horizontal line is drawn through the middle of the C4/C5 disc space. The centerline itself is
drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL
CB: Fixed flexion results in increased loading of the anterior pillar and reactive C1 extension. The neck extensors are in chronic reactive contraction.
Fixed extension of the lower cervical curvature results in increased posterior pillar loading.
% SV< :: Stress Vertebra Angle (deg) (SSU)
The stress vertebra line intersection is a measure of the integrity of the cervical curve. Lines are drawn off the posterior bodies of C2 and C7. The normal angle of intersection is approximately 36.5 degrees.
CB: Diminished angulation represents hypolordosis with resultant increased anterior pillar loading and separation of the facet joints, particularly when in combination with fixed regional flexion.
Increased angulation represents hyperlordosis with resultant increased posterior pillar loading and jamming of the facet joints, particularly when in combination with fixed regional extension.
% SV :: Stress Vertebra (scale of ten divisions)
The stress vertebra represents the location of intersection of the cervical stress lines. The normal location of intersection is at the C4/C5 disc space.
Method: For the determination of this measure, each vertebra and the disc space below are treated as a single vertebral space. Each vertebral space is divided into ten equal graduations from the top of the vertebral space downward. If SV equals C4.9, for example, then the cervical stress lines intersect 9/10ths of the way down the C4 vertebral space.
CB: Intersection of cervical stress lines other than C4/C5 indicates abnormal increased segmental loading at that location.
% GC5 :: Gravity Transfer at C5 (mm) (SSU)
GC5 is a horizontal measure of the head weight as it is projected vertically downward from posterior superior C2 as it passes by the posterior superior C5 body.
Method: Drop a vertical line from posterior superior C2.
GC5 is the horizontal distance from the vertical line to the posterior superior C5 body. In an intact cervical curve, the head weight passes posterior to the C5 reference point. In this case, GC5 is a positive value. As the curve destabilizes through loss of curvature or fixed flexion, the head weight passes anterior of the C5 reference point. In this case, GC5 is a negative value.
CB: Anterior positioning of the head weight creates abnormal anterior loading to the cervical curve. Increased torsional stresses are in direct proportion to anterior linear displacements. Anterior weight bearing causes
posterior joint separation and abnormal ligament loading. Anterior loading is a known degenerative accelerator to the anterior pillar (disc and vertebral body).
% GC7 :: Gravity Transfer at C7 (mm) (SSU)
GC7 is a horizontal measure of the head weight as it is projected vertically downward from posterior superior C2 as it passes by the posterior inferior C7 body.
Method: Drop a vertical line from posterior superior C2.
GC7 is the horizontal distance from the vertical line to the posterior inferior C7 body. In an intact cervical curve, the head weight passes through the C7 reference point. In this case, the value of GC7 is 0 mm. If the head weight passes anterior of the C7 reference point, then GC7 is negative; posterior of the reference point yields a positive GC7.
CB: As the head weight passes anterior to the reference point increased torsional loading occurs at C7/T1 which is directly proportional to the anterior linear displacement. Anterior weight bearing causes posterior joint separation and abnormal ligament loading. Anterior loading and posterior joint separation is a known degenerative accelerator to the anterior pillar of the motion segment.
% C4< :: C4 Vertebral Angle (deg) (SSU)
The C4< is measured comparing a line drawn from the inferior plate of C4 intersecting with a horizontal. The normal value is approximately 10 degrees in flexion. The C4< demonstrates the positional integrity of the base of the upper cervical radius of curvature.
CB: A decreased value would indicate a segmental positioning failure resulting in fixed flexion of the upper radius.
An increased value would indicate a segmental positioning failure resulting in fixed extension of the upper radius.
% C7< :: C7 Vertebral Angle (deg) (SSU)
The C7< is measured comparing a line drawn from the inferior plate of C7 intersecting with a horizontal. The normal value is approximately 27 degrees in flexion. The C7< demonstrates the positional integrity of the base of the lower cervical radius of curvature.
CB: An increased flexion value would indicate a segmental positioning failure resulting in fixed flexion of the lower cervical radius of curvature.
An increased extension value would indicate a segmental positioning failure resulting in fixed extension of the lower cervical radius.
% T1< :: T1 Angle (deg) (SSU)
The T1< is measured comparing a line drawn off the superior plate of T1 intersecting with a horizontal. The normal value is approximately 30 degrees in flexion. The T1< demonstrates positional integrity to the base of the cervical curve. Malpositioning of the T1< results in fixed flexion or extension of the cervical curve.
CB: An increased flexion value would result in hyperlordosis of the lower cervical curve.
A increased extension value would result in hypolordosis of the cervical curve.
% D< :: Disc Angle (deg) (SSU)
The disc angle is formed for each cervical vertebra C2 through C7 by a line drawn off the inferior plate of the vertebra above the disc space in question and a line drawn off the superior plate of the vertebra below the disc space.
Method: A disc space relates to the vertebra above it. For example, the C2 disc space is located below vertebra C2. Therefore, the C2 disc angle is formed by a line drawn off the inferior plate of C2 and a line drawn off the superior plate of C3. The remaining cervical disc angles are formed in a similar manner. The Average/SSU Report compares the measured cervical disc angles to ideal values of intact cervical curves with SV< approximating 36.5 degrees.
CB: Diminished angle results in anterior pillar loading, fixed flexion of the superior vertebra, fixed flexion of the CL
Increased angle results in posterior pillar loading, fixed extension of the superior vertebra, fixed extension of the CL
% V< :: Vertebral Angle (deg)
The vertebral angle is formed for each cervical vertebra C3 through C7 by a line drawn off the inferior plate of the vertebra and a line drawn of the superior plate of the vertebra.
CB: The vertebral angle assesses the structural shape of the vertebra. It contributes to the formation of the spinal curvatures. This measurement helps distinguish between structural and function compensation.
% VH< :: Vertebra to the Horizontal Angle (deg)
The vertebra-to-horizontal angle is formed for each cervical vertebra C2 through C7 by a line drawn off the inferior plate of the vertebra and a true horizontal.
CB: Increased or decreased values indicate departure from normal weight bearing orientation. This measurement helps assess global, regional and segmental vertebral positioning.
% AVH :: Anterior Vertebral Height (mm)
The anterior vertebral height is determined for each cervical vertebra C3 through C7 by measuring the distance from the anterior inferior body to the anterior superior body.
CB: The line lengths of the vertebral body perimeter are measured to assess geometric integrity of the vertebra. Gross disparity of anterior and posterior heights could indicate compression fracture.
The line lengths can be used to determine intra/inter examiner reliability.
% PVH :: Posterior Vertebral Height (mm)
The posterior vertebral height is determined for each cervical vertebra C2 through C7 by measuring the distance from the posterior inferior body to the posterior superior body.
CB: The line lengths of the vertebral body perimeter are measured to assess geometric integrity of the vertebra. Gross disparity of anterior and posterior heights could indicate compression fracture.
The line lengths can be used to determine intra/inter examiner reliability.
% SVL :: Superior Vertebral Length (mm)
The superior vertebral length is determined for each cervical vertebra C3 through C7 by measuring the distance from the anterior superior body to the posterior superior body.
CB: Gross disparity of superior and inferior vertebral
length is suggestive of a structural abnormality.
% IVL :: Inferior Vertebral Length (mm)
The inferior vertebral length is determined for each cervical vertebra C2 through C7 by measuring the distance from the anterior inferior body to the posterior inferior body.
CB: Gross disparity of the superior and inferior vertebral lengths is suggestive of a structural abnormality.
% ADH :: Anterior Disc Height (mm)
The anterior disc height is determined for each cervical disc space C2 through C7 by measuring the distance from the anterior superior body of the vertebra below the disc space in question to the anterior inferior body of the vertebra above the disc space.
CB: Assesses degenerative condition of the disc when compared to values of superior and inferior discs.
% PDH :: Posterior Disc Height (mm)
The posterior disc height is determined for each cervical disc space C2 through C7 by measuring the distance from the posterior superior body of the vertebra below the disc space in question to the posterior inferior body of the vertebra above the disc space.
CB: Assesses degenerative condition of the disc when compared to values of superior and inferior discs.
Lateral Thoracic Calculations
% Rc :: Radius of Curvature, Overall (cm)
The radius is a measure of the thoracic curvature using three points located on T1, T6 and T12.
CB: A loss of curvature (increased radius of curvature; hypokyphotic), in combination with fixed regional extension, results in increased posterior loading.
A gain of curvature (decreased radius of curvature; hyperkyphosis), in combination with fixed regional flexion, causes increased loading to the anterior pillar with separation of the posterior facets.
% Rc I :: Radius of Curvature, Ideal (cm)
In the neutral position, the ideal radius is equal to the distance between posterior superior T1 and posterior inferior T12.
% Rc Up :: Radius of Curvature, Upper (cm)
The radius of curvature of the upper thoracic curve is measured using three points located on T1, T4, and T6. The upper radius is compared to the ideal and overall radii.
When the thoracic curve is coherent, the upper radius approximates the overall radius of curvature. A difference of the upper radius to the overall radius is suggestive of the thoracic curve working as two separate units to accomplish regional and global compensation.
CB: An increased radius of curvature (hypokyphotic) causes increased loading to the posterior pillar, particularly in the presence of fixed extension of the centerline angle.
A decreased radius of curvature (hyperkyphotic) causes increased loading to the anterior pillar, particularly in the presence of fixed flexion of the centerline angle.
% Rc Lo :: Radius of Curvature, Lower (cm)
The radius of curvature of the lower thoracic curve is measured using three points located on T7, T9, and T12. The lower radius is compared to the ideal and overall radii.
When the thoracic curve is coherent, the lower radius approximates the overall radius of curvature. A difference of the lower radius to the overall radius is suggestive of the thoracic curve working as two separate units to accomplish regional and global compensation.
CB: An increased radius of curvature (hypokyphotic) causes increased loading to the posterior pillar, particularly in the presence of fixed extension of the centerline angle.
A decreased radius of curvature (hyperkyphotic) causes increased loading to the anterior pillar, particularly in the presence of fixed flexion of the centerline angle.
% CL
The centerline angle of the radius of curvature is a measure of fixed extension or flexion of the thoracic curve.
Method: A circular arc is drawn through three points located on T1, T6, and T12 (see “Radius of Curvature, Overall” above). A horizontal line is drawn through the middle of the T6/T7 disc space. The centerline itself is drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL
CB: Fixed flexion of the centerline angle results in increased anterior pillar loading.
Fixed extension of the centerline angle results in increased posterior pillar loading.
% CL
The centerline angle of the upper radius of curvature is a measure of fixed extension or flexion of the upper thoracic curve.
Method: A circular arc is drawn through three points located on T1, T4, and T6 (see “Radius of Curvature, Upper” above). A horizontal line is drawn through the middle of the T6/T7 disc space. The centerline itself is drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL
CB: Fixed flexion of the centerline angle results in increased anterior pillar loading.
Fixed extension of the centerline angle results in increased posterior pillar loading.
% CL
The centerline angle of the lower radius of curvature is a measure of fixed extension or flexion of the lower thoracic curve.
Method: A circular arc is drawn through three points located on T7, T9, and T12 (see “Radius of Curvature, Lower” above). A horizontal line is drawn through the middle of the T6/T7 disc space. The centerline itself is drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL
CB: Fixed flexion of the centerline angle results in increased anterior pillar loading.
Fixed extension of the centerline angle results in increased posterior pillar loading.
% SV< :: Stress Vertebra Angle (deg) (SSU)
The stress vertebra line intersection is a measure of the integrity of the thoracic curve. Lines are drawn off the anterior bodies of T1 and T12. The normal angle of intersection is approximately -52.2 degrees.
CB: Diminished angulation represents hypokyphosis with resultant increased posterior pillar loading, particularly when in combination with fixed regional extension.
Increased angulation represents hyperkyphosis with resultant increased anterior pillar loading, particularly when in combination with fixed regional flexion.
% SV :: Stress Vertebra (scale of ten divisions)
The stress vertebra represents the location of intersection of the thoracic stress lines. The normal location of intersection is at the T6/T7 disc space.
Method: For the determination of this measure, each vertebra and the disc space below are treated as a single vertebral space. Each vertebral space is divided into ten equal graduations from the top of the vertebral space downward. If SV equals T4.9, for example, then the thoracic stress lines intersect 9/10ths of the way down the T4 vertebral space.
CB: Intersection of thoracic stress lines other than T6/T7 indicates abnormal increased segmental loading at that location.
% GT7 :: Gravity Transfer at T7 (mm) (SSU)
GT7 is a horizontal measure of the body weight as it is projected vertically downward from posterior superior T1 as it passes by the anterior superior T7 body.
Method: Drop a vertical line from posterior superior T1.
GT7 is the horizontal distance from the vertical line to the posterior superior T7 body. In an intact thoracic curve, the body weight passes anterior to the T7 reference point. In this case, GT7 is a negative value.
CB: A horizontal measure passing posterior to the T7 reference (GT7 is a positive value), indicates a disruption of the thoracic curve or a centerline in fixed extension, both of which cause posterior pillar loading to the lower thoracic and lumbar curves.
% GT12 :: Gravity Transfer at T12 (mm) (SSU)
GT12 is a horizontal measure of the body weight as it is projected vertically downward from posterior superior T1 as it passes by the posterior inferior T12 body.
Method: Drop a vertical line from posterior superior T1.
GT12 is the horizontal distance from the vertical line to the posterior inferior T12 body. In an intact thoracic curve, the body weight passes through the T12 reference point. In this case, the value of GT12 is 0 mm. If the body weight passes anterior of the T12 reference point, then GT12 is negative; posterior of the reference point yields a positive GT12.
CB: A horizontal measure passing posterior to the T12 reference (GT12 is a positive value), indicates a disruption of the thoracic curve or a centerline in fixed extension, both of which cause posterior pillar loading to the lumbar spine.
% T1< :: T1 Angle (deg) (SSU)
The T1< is measured comparing a line drawn off the superior plate of T1 intersecting with a horizontal. The normal value is approximately 30 degrees in flexion. The T1< demonstrates positional integrity to the base of the cervical curve. Malpositioning of the T1< results in fixed flexion or extension of the thoracic curve.
CB: An increased flexion value would result in hyperlordosis of the lower cervical curve.
An increased extension value would result in hypolordosis of the cervical curve.
% T6< :: T6 Vertebral Angle (deg) (SSU)
The T6< is measured comparing a line drawn from the inferior plate of T6 intersecting with a horizontal. The normal value is approximately 0 degrees. The T6< demonstrates the positional integrity of the base of the upper thoracic radius of curvature.
CB: A negative value would force the upper thoracic curve into fixed flexion with resultant anterior pillar loading.
A positive value would force the upper thoracic curve into fixed extension with resultant posterior loading to the lower thoracic and lumbar curves.
% T12< :: T12 Vertebral Angle (deg) (SSU)
The T12< is measured comparing a line drawn from the inferior plate of T12 intersecting with a horizontal. The normal value is approximately 28 degrees in extension. The T12< demonstrates the positional integrity of the base of the lower thoracic radius of curvature.
CB: A diminished value results in fixed flexion of the lower thoracic curve and increased anterior loading to the upper lumbar curve.
An increased value results in fixed extension of the lower thoracic curve and increased posterior loading to the upper lumbar curve.
% D< :: Disc Angle (deg) (SSU)
The disc angle is formed for each thoracic vertebra T1 through T12 by a line drawn off the inferior plate of the vertebra above the disc space in question and a line drawn off the superior plate of the vertebra below the disc space.
Method: A disc space relates to the vertebra above it. For example, the T1 disc space is located below vertebra T1. Therefore, the T1 disc angle is formed by a line drawn off the inferior plate of T1 and a line drawn off the superior plate of T2. The remaining thoracic disc angles are formed in a similar manner.
CB: Diminished angle results in anterior pillar loading, fixed flexion of the superior vertebra, fixed flexion of the CL
Increased angle results in posterior pillar loading, fixed extension of the superior vertebra, fixed extension of the CL
% V< :: Vertebral Angle (deg)
The vertebral angle is formed for each thoracic vertebra T1 through T12 by a line drawn off the inferior plate of the vertebra and a line drawn of the superior plate of the vertebra.
CB: The vertebral angle assesses the structural shape of the vertebra. It contributes to the formation of the spinal curvatures. This measurement helps distinguish between structural and function compensation.
% VH< :: Vertebra to the Horizontal Angle (deg)
The vertebra-to-horizontal angle is formed for each thoracic vertebra T1 through T12 by a line drawn off the inferior plate of the vertebra and a true horizontal.
CB: Increased or decreased values indicate departure from normal weight bearing orientation. This measurement helps assess global, regional and segmental vertebral positioning.
% AVH :: Anterior Vertebral Height (mm)
The anterior vertebral height is determined for each thoracic vertebra T1 through T12 by measuring the distance from the anterior inferior body to the anterior superior body.
CB: The line lengths of the vertebral body perimeter are measured to assess geometric integrity of the vertebra. Gross disparity of anterior and posterior heights could indicate compression fracture.
The line lengths can be used to determine intra/inter examiner reliability.
% PVH :: Posterior Vertebral Height (mm)
The posterior vertebral height is determined for each thoracic vertebra T1 through T12 by measuring the distance from the posterior inferior body to the posterior superior body.
CB: The line lengths of the vertebral body perimeter are measured to assess geometric integrity of the vertebra. Gross disparity of anterior and posterior heights could indicate compression fracture.
The line lengths can be used to determine intra/inter examiner reliability.
% SVL :: Superior Vertebral Length (mm)
The superior vertebral length is determined for each thoracic vertebra T1 through T12 by measuring the distance from the anterior superior body to the posterior superior body.
CB: Gross disparity of superior and inferior vertebral length is suggestive of a structural abnormality.
% IVL :: Inferior Vertebral Length (mm)
The inferior vertebral length is determined for each thoracic vertebra T1 through T12 by measuring the distance from the anterior inferior body to the posterior inferior body.
CB: Gross disparity of the superior and inferior vertebral lengths is suggestive of a structural abnormality.
% ADH :: Anterior Disc Height (mm)
The anterior disc height is determined for each thoracic disc space T1 through T12 by measuring the distance from the anterior superior body of the vertebra below the disc space in question to the anterior inferior body of the vertebra above the disc space.
CB: Assesses degenerative condition of the disc when compared to values of superior and inferior discs.
% PDH :: Posterior Disc Height (mm)
The posterior disc height is determined for each thoracic disc space T1 through T12 by measuring the distance from the posterior superior body of the vertebra below the disc space in question to the posterior inferior body of the vertebra above the disc space.
CB: Assesses degenerative condition of the disc when compared to values of superior and inferior discs.
Lateral Lumbar Calculations
% Rc :: Radius of Curvature, Overall (cm)
The radius is a measure of the lumbar curvature using three points located on L1, L3 and L5.
CB: A loss of curvature (increased radius of curvature; hypolordotic), in combination with fixed regional flexion, results in increased anterior pillar loading and posterior joint separation.
An increase in curvature (decreased radius of curvature; hyperlordotic), in combination with fixed regional extension, causes increased loading to the posterior pillar.
% Rc I :: Radius of Curvature, Ideal (cm)
In the neutral position, the ideal radius is equal to the distance between anterior superior L1 and posterior inferior S1.
% Rc Up :: Radius of Curvature, Upper (cm)
The radius of curvature of the upper lumbar curve is measured using three points located on L1, L2, and L3. The upper radius is compared to the ideal and overall radii.
When the lumbar curve is coherent, the upper radius approximates the overall radius of curvature. A difference
of the upper radius to the overall radius is suggestive of the lumbar curve working as two separate units to accomplish regional and global compensation. Ligament instability or disruption is also suggested,
CB: An increased radius of curvature (hypolordosis) causes increased loading to the anterior pillar, particularly in the presence of fixed flexion of the centerline angle.
A decreased radius of curvature (hyperlordosis) causes increased loading to the posterior pillar, particularly in the presence of fixed extension of the centerline angle.
% Rc Lo :: Radius of Curvature, Lower (cm)
The radius of curvature of the upper lumbar curve is measured using three points located on L3, L4, and L5. The lower radius is compared to the ideal and overall radii.
When the lumbar curve is coherent, the upper radius approximates the overall radius of curvature. A difference of the lower radius to the overall radius is suggestive of the lumbar curve working as two separate units to accomplish regional and global compensation. Ligament instability or disruption is also suggested, CB: An increased radius of curvature (hypolordosis) causes increased loading to the anterior pillar, particularly in the presence of fixed flexion of the centerline angle.
A decreased radius of curvature (hyperlordosis) causes increased loading to the posterior pillar, particularly in the presence of fixed extension of the centerline angle.
% CL
The centerline angle of the radius of curvature is a measure of fixed extension or flexion of the lumbar curve.
Method: A circular arc is drawn through three points located on L1, L3, and L5 (see “Radius of Curvature, Overall” above). A horizontal line is drawn through the middle of the L3/L4 disc space. The centerline itself is
drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL CB: Fixed flexion of the centerline angle results in increased anterior pillar loading and posterior joint separation. The pelvic extensors are in chronic reactive contraction.
Fixed extension of the centerline angle results in increased posterior pillar loading. The pelvic flexors are in chronic reactive contraction.
% CL
The centerline angle of the upper radius of curvature is a measure of fixed extension or flexion of the upper lumbar curve.
Method: A circular arc is drawn through three points located on L1, L2, and L3 (see “Radius of Curvature, Overall” above). A horizontal line is drawn through the middle of the L3/L4 disc space. The centerline itself is
drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL CB: Fixed flexion of the centerline angle results in increased anterior pillar loading.
Fixed extension of the centerline angle results in increased posterior pillar loading.
% CL
The centerline angle of the lower radius of curvature is a measure of fixed extension or flexion of the lower lumbar curve.
Method: A circular arc is drawn through three points located on L3, L4, and L5 (see “Radius of Curvature, Overall” above). A horizontal line is drawn through the middle of the L3/L4 disc space. The centerline itself is drawn from the center of the circular arc to the point where the arc intersects the horizontal line. CL CB: Fixed flexion of the centerline angle results in increased anterior pillar loading.
Fixed extension of the centerline angle results in increased posterior pillar loading.
% SV< :: Stress Vertebra Angle (deg) (SSU)
The stress vertebra line intersection is a measure of the integrity of the lumbar curve. Lines are drawn off the posterior bodies of L1 and L5. The normal angle of intersection is approximately 37.4 degrees.
CB: Diminished angulation represents hypolordosis with resultant increased anterior pillar loading,
particularly when in combination with fixed regional flexion.
Increased angulation represents hyperlordosis with resultant increased posterior pillar loading, particularly when in combination with fixed regional extension.
% SV :: Stress Vertebra (scale of ten divisions)
The stress vertebra represents the location of intersection of the lumbar stress lines. The normal location of intersection is at the L3/L4 disc space.
Method: For the determination of this measure, each vertebra and the disc space below are treated as a single vertebral space. Each vertebral space is divided into ten equal graduations from the top of the vertebral space downward. If SV equals L2.9, for example, then the lumbar stress lines intersect 9/10ths of the way down the L2 vertebral space.
CB: Intersection of lumbar stress lines other than L3/L4 indicates abnormal increased segmental loading at that location.
% GL4 :: Gravity Transfer at L4 (mm) (SSU)
GL4 is a horizontal measure of the body weight as it is projected vertically downward from posterior inferior L1 as it passes by the posterior superior L4 body.
Method: Drop a vertical line from posterior inferior L1.
GL4 is the horizontal distance from the vertical line to the posterior superior L4 body. In an intact lumbar curve, the body weight passes posterior to the L4 reference point. In this case, GT7 is a positive value.
CB: A horizontal measure passing anterior to the L4 reference (GL4 is a negative value), indicates a disruption of the lumbar curve or a centerline in fixed flexion, both of which cause anterior pillar loading to the lower lumbar curve.
% GS1 :: Gravity Transfer at S1 (mm) (SSU)
GS1 is a horizontal measure of the body weight as it is projected vertically downward from posterior inferior L1 as it passes by the posterior superior S1 body.
Method: Drop a vertical line from posterior inferior S1. GS1 is the horizontal distance from the vertical line to the posterior superior S1 body. In an intact lumbar curve, the body weight passes through the S1 reference point. In this case, the value of GS1 is 0 mm. If the body weight passes anterior of the S1 reference point, then GS1 is negative; posterior of the reference point yields a positive GS1.
CB: A horizontal measure passing posterior to the S1 reference (GS1 is a positive value), indicates a increased posterior pillar loading to the lumbar spine.
% L1< :: L1 Angle (deg) (SSU)
The L1< is measured comparing a line drawn off the superior plate of L1 intersecting with a horizontal. The normal value is approximately 30 degrees in extension.
- CB. A decreased value causes flexion of the lower thoracic curve and is usually associated with fixed flexion of the upper lumbar curve.
An increased value results in extension of the lower thoracic curve and is usually associated with increased posterior loading of the lumbar curve and sacroiliac joints.
% L3< :: L3 Vertebral Angle (deg) (SSU)
The L3< is measured comparing a line drawn from the inferior plate of L3 intersecting with a horizontal. The normal value is approximately 0 degrees.
- CB. An increased value results in extension of the upper lumbar spine and is usually associated with increased posterior pillar loading of the lumbar spine and sacroiliac joints.
A decreased value results in flexion of the upper lumbar curve and is usually associated with increased anterior pillar loading of the lumbar spine.
% L5< :: L5 Vertebral Angle (deg) (SSU)
The L5< is measured comparing a line drawn from the inferior plate of L5 intersecting with a horizontal. The normal value is approximately 25 degrees in flexion.
- CB. A decreased negative (extension) value results in increased posterior pillar loading of the lumbar spine and sacroiliac joints.
An increased negative value (flexion) results in increased loading to the anterior pillar of the lumbar spine and sacroiliac joints.
% D< :: Disc Angle (deg) (SSU)
The disc angle is formed for each lumbar vertebra L1 through L5 by a line drawn off the inferior plate of the vertebra above the disc space in question and a line drawn off the superior plate of the vertebra below the disc space.
Method: A disc space relates to the vertebra above it. For example, the L1 disc space is located below vertebra L1. Therefore, the L1 disc angle is formed by a line drawn off the inferior plate of L1 and a line drawn off the superior plate of L2. The remaining lumbar disc angles are formed in a similar manner.
- CB. An increased angle results in fixed extension of the superior vertebra with resultant increased posterior pillar loading.
A decreased angle results in fixed flexion of the superior vertebra with resultant increased anterior pillar loading.
% V< :: Vertebral Angle (deg)
The vertebral angle is formed for each lumbar vertebra L1 through L5 by a line drawn off the inferior plate of the vertebra and a line drawn of the superior plate of the vertebra.
CB: The vertebral angle assesses the structural shape of the vertebra. It contributes to the formation of the spinal curvatures. This measurement helps distinguish between structural and function compensation.
% VH< :: Vertebra to the Horizontal Angle (deg)
The vertebra-to-horizontal angle is formed for each lumbar vertebra L1 through L5 by a line drawn off the inferior plate of the vertebra and a true horizontal.
CB: Increased or decreased values indicate departure from normal weight bearing orientation. This measurement helps assess global, regional and segmental vertebral positioning.
% AVH :: Anterior Vertebral Height (mm)
The anterior vertebral height is determined for each lumbar vertebra L1 through L5 by measuring the distance from the anterior inferior body to the anterior superior body.
CB: The line lengths of the vertebral body perimeter are measured to assess geometric integrity of the vertebra. Gross disparity of anterior and posterior heights could indicate compression fracture.
The line lengths can be used to determine intra/inter examiner reliability.
% PVH :: Posterior Vertebral Height (mm)
The posterior vertebral height is determined for each lumbar vertebra L1 through L5 by measuring the distance from the posterior inferior body to the posterior superior body.
CB: The line lengths of the vertebral body perimeter are measured to assess geometric integrity of the vertebra. Gross disparity of anterior and posterior heights could indicate compression fracture.
The line lengths can be used to determine intra/inter examiner reliability.
% SVL :: Superior Vertebral Length (mm)
The superior vertebral length is determined for each lumbar vertebra L1 through L5 by measuring the distance from the anterior superior body to the posterior superior body.
CB: Gross disparity of superior and inferior vertebral length is suggestive of a structural abnormality.
% IVL :: Inferior Vertebral Length (mm)
The inferior vertebral length is determined for each lumbar vertebra L1 through L5 by measuring the distance from the anterior inferior body to the posterior inferior body.
CB: Gross disparity of the superior and inferior vertebral lengths is suggestive of a structural abnormality.
% ADH :: Anterior Disc Height (mm)
The anterior disc height is determined for each lumbar disc space L1 through L5 by measuring the distance from the anterior superior body of the vertebra below the disc space in question to the anterior inferior body of the vertebra above the disc space.
CB: Assesses degenerative condition of the disc when compared to values of superior and inferior discs.
% PDH :: Posterior Disc Height (mm)
The posterior disc height is determined for each lumbar disc space L1 through L5 by measuring the distance from the posterior superior body of the vertebra below the disc space in question to the posterior inferior body of the vertebra above the disc space.
CB: Assesses degenerative condition of the disc when compared to values of superior and inferior discs.
% S1< :: Sacral Angle
The sacral angle is measured by drawing a line across the top of the sacrum and comparing its inclination to a true horizontal. The sacrum forms the foundation of the lumbar curve and as such contributes to its form. The normal value is 37.9 degrees in flexion.
- CB. An increased sacral angle results in lumbar hyperlordosis, increased posterior loading of L4 and L5, and fixed flexion or extension of the pelvis.
A decreased angle results in lumbar hypolordosis, increased anterior loading of L4 and L5 and fixed extension or flexion of the pelvis.