Roentgenometrics S.THIYAGARAJAN

Application of standard lines and measurements to radiographs

Allows the detection of subtle abnormalities

Assists in avoiding misdiagnosis

Comparison of studies is facilitated

Basilar Angle

Welcker’s basilar angle/Martin’s basilar angle / Sphenobasilar angle

Lateral skull The Nasion(Frontal-nasal junction)

The center of the Sella turcica (Midpoint between the clinoid processes)

The Basion (Anterior margin of the foramen magnum)

Index of the relationship between the anterior skull and its base

>152° - Platybasia

Congenital Isolated impression

Occipitalization

Acquired Paget’s disease

Rheumatoid arthritis

Fibrous dysplasia

This may or may not be associated with basilar impression

Chamberlain’s Line

Palato-occipital line.

Projection: Lateral skull; lateral cervical spine.

The posterior margin of the Hard palate

The posterior aspect of the foramen magnum

(OPISTHION)

The relationship of this line to the tip of the

odontoid process is then assessed

AVERAGE MINIMUM MAXIMUM

137 123 152

Tip of the odontoid process should not project above this line

Normal variation of 3 mm above this line may occur

A measurement of ≥7 mm is definitely abnormal.

An abnormal superior position of the odontoid

Basilar impression

Platybasia

Atlas occipitalization

Bone-softening diseases of the skull base Paget’s disease

Osteomalacia

Fibrous dysplasia

Rheumatoid arthritis

McGregor’s Line (Basal line) Projection: Lateral skull; lateral cervical spine.

Postero superior margin of the hard palate

Most inferior surface of the occipital bone

The relationship of the odontoid apex to this line

is examined

> 8 mm in males

> 10 mm in females

In children younger than 18 years, these maximum values diminish with decreasing chronologic age.

McGregor’s line appears to be the most accurate and reproducible

Abnormal superior position of the odontoid

Basilar impression

Macrae’s Line Foramen magnum line

The Basion (anterior margin of the foramen magnum)

Posterior (Opisthion) margins of the foramen magnum

The inferior margin of the occipital bone should lie at or below this line

In addition a perpendicular line drawn through the odontoid apex should intersect this line in its anterior quarter

If the inferior margin of the occipital bone is convex in a superior direction and/or lies above this line, then basilar impression is present.

If the odontoid apex does not lie in the ventral quarter of this line

Dislocation of the atlanto-occipital joint Fracture

Dysplasia of the dens

Digastric Line (Biventer line)

Projection: AP open mouth

The digastric groove medial to the base of the mastoid process

The vertical distance to the odontoid apex and atlanto occipital joints is

measured

Measure Average (mm) Minimum (mm) Maximum (mm)

Digastric line-odontoid apex 11 1 21

Digastric line-atlanto-occipital joint

12 4 20

Both measurements will decrease in basilar impression

• Platybasia

• Atlas occipitalization

• Bone-softening diseases of the skull base

• Paget’s disease

• Osteomalacia

• Fibrous dysplasia

• Rheumatoid arthritis

Occipitoatlantal alignment

Projection: Lateral skull.

Two lines are constructed

1. Foramen magnum line (FML) is drawn along the inferior margin of the

occiput (MACRAE’S LINE)

2. Atlas plane line (APL) is drawn

through the center of the anterior

tubercle and the narrowest portion of

the posterior arch of atlas

The FML and APL should be parallel.

Divergence of the FML and APL anteriorly suggests anterior-superior malposition of the occiput

Divergence of the lines posteriorly suggests posterior-superior malposition of the occiput

Other method The anterior margin of the foramen magnum should line up with the dens.

A line projected downward from the dorsum sellae along the clivus to the basion should point to the dens. Wachenheim's line

The posterior margin of foramen magnum should line up with the C1 spinolaminar line.

Power ratio :The ratio of Basion - spinolaminar line of C1 to Opisthion - posterior cortex of C1 anterior arch normally ranges from 0.6 to 1.0, with the mean being 0.8. A ratio greater than 1.0 implies anterior cranio-cervical dislocation.

Sella Turcica Size

The greatest AP diameter and the greatest vertical diameter Diameter Average (mm) Minimum (mm) Maximum (mm)

Anteroposterior 11 5 16

Vertical 8 4 12

Small sella Normal variant

Hypopituitarism (long after Sheehan's)

Microcephaly

Myotonic dystrophy

Prader-Willi-Lambert syndrome

Cockayne syndrome

Dystrophia myotonica

Enlarged sella

Pituitary neoplasm

Empty sella syndrome

Extrapituitary mass Neoplasm

Aneurysm

Normal variant

J shaped sella

Elongated sella with shallow anterior convexity which represents exaggerated of sulcus chiasmaticus

Normal variant

MPS

Achondroplasia

Chronic hydrocephalus

Optic chiasmatic glioma

Osteogenisis imperfecta

Neurofibromatosis

Atlantoaxial "overhang" sign AP open-mouth projection

Lateral margin of the lateral masses of

atlas should not appear more lateral than

the superior articular processes of axis

If the lateral margin of the atlas lateral mass lies

lateral to the lateral axis margin, Radiologic sign of

Jefferson’s fracture

Odontoid fracture

Alar ligament instability

Rotatory atlantoaxial subluxation

Mild degree of overhanging may be a normal variant

Atlantodental Interspace

Atlas-odontoid space, predental interspace, atlas-dens interval

Projection: Lateral neutral; flexion-extension cervical spine.

The distance measured is between the posterior margin of the

anterior tubercle and the anterior surface of the odontoid

Decreased space

Advancing age (Degenerative joint disease of the atlantodental joint)

Widened space with reduction in the neural canal size

Trauma

Occipitalization

Down’s syndrome

Pharyngeal infections (Grisel’s disease)

Inflammatory arthropathies Ankylosing spondylitis

Rheumatoid arthritis

Psoriatic arthritis

Reiter’s syndrome

Cervical Gravity Line A vertical line is drawn through the apex of

the odontoid process

Age Minimum (mm)

Maximum (mm)

Adults 1 3

Children 1 5

This line should pass through the C7 body

Gross assessment of where the gravitational stresses are acting at the cervicothoracic junction.

Stress Lines of the Cervical Spine

Ruth Jackson’s lines

Projection: Lateral cervical spine (flexion, extension)

Two lines are constructed on each film

1) The first line is drawn along the

posterior surface of the axis

2) The second line is drawn along

the posterior surface of the C7

body until it intersects the axis

line

Normal Measurements

Flexion - lines should intersect at the level of the C5-C6 disc or facet joints.

Extension - lines should intersect at the level of the C4-C5 disc or facet joints.

The intersection point represents the focus of stress when the cervical spine is placed in the respective positions

The point of intersection does not appear to correlate with the level of degenerative disc disease

Muscle spasm, joint fixation, and disc degeneration may alter the stress point.

Cervical Lordosis

Visual assessment (Subjective)

On the lateral cervical projection

Well maintained anterior convexity is lordosis

Exaggerated anterior convexity is hyperlordosis

Slight anterior convexity hypolordosis

Lack of curvature is alordosis

Posterior convexity is kyphosis

Altered cervical lordosis

Trauma

Degeneration

Muscle spasm

Aberrant inter-segmental mechanics

Depth method Lateral cervical projection

A line is drawn from the tip of the odontoid process to the posterior surface of C7

A horizontal measure is taken from the vertical line to the posterior surface of the C4 body (X)

The average depth is 12 mm

Negative – Kyphosis

Largest values – Hyperlordosis

The depth method provides a more accurate assessment of cervical lordosis

Angle of curve Lateral cervical projection

A line is drawn connecting the anterior and posterior tubercles of the atlas

Second line is drawn along the inferior endplate of C7

Perpendicular lines are drawn from the atlas and C7 lines, and their angle of intersection is recorded as the cervical lordosis (X°)

The average value is 40 degrees

Negative – kyphosis

Large – hyperlordosis

Less accurate than the depth method. Because the measurements depend only on CI and C7

Prevertebral Soft Tissues

The soft tissue in front of the vertebral bodies and behind the air shadow of the pharynx, larynx, and trachea is measured

The bony landmarks Anterior arch of the atlas

Inferior corners of the axis & C3

Superior corner of C4

Inferior corners of C5, C6, and C7

C2-C3 - RPI

Behind the larynx (C4-C5) - RLI Behind the trachea (C5-C7) - RTI.

Widening

Post-traumatic hematoma

Retropharyngeal abscess

Neoplasm from the adjacent bone and soft tissue structures.

Spinolaminar junction line Posterior Cervical Line, arch-body line.

Projection: Lateral cervical spine (neutral, flexion, extension).

The cortical white line of the spinolaminar junction identified at each level C1 to C7

• Each spinolaminar junction will be curved slightly anteriorly from superior to inferior

Level Flexion (mm) Neutral (mm) Extension (mm)

C1 11 10 8

C2 6 5 6

C3 7 7 6

C4 7 7 8

C5 22 20 20

C6 20 20 19

C7 20 20 21

• For consistency, the most anterior part of the convexity is compared between levels

Discontinuous at any level

Anterior or posterior displacement

This line is especially useful for detecting subtle odontoid fractures and atlantoaxial subluxation (anterior)

A disruption in the middle to lower cervical spine may also be a sign of anterolisthesis, retrolisthesis, or frank dislocation.

Cervical Spinal Canal Projection: Lateral cervical (neutral, flexion, extension)

The sagittal diameter is measured

from the posterior surface of the

midvertebral body to the nearest

surface of the same segmental

spinolaminar junction line

Level Average (mm) Minimum (mm) Maximum (mm)

C1 22 16 31

C2 20 14 27

C3 18 13 23

C4 17 12 22

C5 17 12 22

C6 17 12 22

C7 17 12 22

Narrowing of the canal (stenosis) < 12 mm

Significance

If degenerative posterior osteophytes are present, the measurement can be made from their tip to examine the magnitude of the stenotic effect. The degree of stenosis from these spurs is best measured on extension films

An abnormally widened canal may be associated with a spinal cord neoplasm or syringomyelia.

The most accurate measurement is by the ratio of the sagittal dimension of the canal and vertebral body (canal to body ratio, Pavlov’s ratio)

A ratio of less than 0.82 is significant for spinal stenosis. The benefit of this method is that it removes the effects of radiographic magnification.

Cervical, thoracic, and lumbar endplate lines

On the lateral cervical projection, lines arc drawn along the inferior endplate of the C2-T1 vertebrae and extended posteriorly to the cervical spine

The cervical endplate lines should all intersect at a common point located posterior to the spine

Lack of convergence Normal lordotic cervical spine

curve Intersegmental malpositions

Lines that cross closely to the spine Extension malposition of the

superior segment

Lines that diverge sharply flexion malposition of the

superior segment.

Frontal cervical, thoracic, and lumbar projections

Lines are drawn to approximate the inferior vertebral endplates

The lines at adjacent levels should be parallel Divergence of the endplate lines

Lateral flexion malposition opposite the side of divergence

Cervical, thoracic, and lumbar vertebral rotation

Body width method

Distance from the lateral margins of the vertebral bodies to the origin of the spinous process should be equal bilaterally.

Distances not equal Vertebral rotation

Spinous process deviation to the side of the smaller distance.

Pedicle method

Frontal projection

The appearance of the pedicle shadows may suggest vertebral rotation

It is expected the pedicle shadows demonstrate bilateral symmetry

If the width of a pedicle shadow appears narrower than the contralateral pedicle shadow, it suggests

Segmental rotation with the spinous process deviated to the side of the narrower pedicle shadow

Posterior vertebral body

rotation to the side of the wider pedicle shadow

Cervical, thoracic, and lumbar vertebral sagittal alignment

George's line

Lateral projections

Curvilinear line is drawn along the posterior surfaces of the vertebral bodies

The curve should maintain a smooth contour throughout the spinal region without segmental disruption.

Disruption Segmental anterolisthesis

Retrolisthesis

Disruptions at multiple consecutive levels Normal flexion and extension patterns.

However, the adjacent posterior body lines should not demonstrate more than 3 mm of net translation in a comparison of the flexion and extension radiographs

Barge's "e" space Lateral lumbar projection

Lines are drawn along the superior and inferior vertebral endplates of each segment

Lines perpendicular to each endplate line are then drawn and extended across the intervertebral disc space.

The distance between the perpendicular lines at the inferior end- plate of each lumbar segment is measured as the "e" space

The space should not exceed 3 mm

Larger Barge's "e" space

Retrolisthesis of the segment above

Negative values indicate

Anterolisthesis

Visual method Segmental retrolisthesis

Intervertebral disc degeneration (osteophytes, eburnation, reduced disc space, Schmorl's nodes, endplate irregularity)

The lowest segment of a "stack" of three or more vertebrae that do not contribute to a sagittal curvature may be posterior

The lowest involved segment of three or more consecutive segments that appear to be flexed or extended during neutral patient posture may be posterior

Segmental rotation in a coronal plane that produces an hourglass appearance

Narrowed sagittal diameter of the intervertebral foramen

Visual disparity of segmental alignment when comparing the margins of adjacent vertebrae

Retrolisthesis of L5 is often seen as a normal variant, accompanying short pedicles

Cervical toggle analysis Atlas tilt

Lateral cervical projection

Three lines are constructed

Occipital condyle line (OCL) is drawn along the base of the occipital condyles

Atlas plane line (APL) is drawn through the center of the anterior tubercle and the narrowest portion of the posterior arch of the atlas

Listing line (LL) is drawn parallel to the occipital condyle line and

through the narrowest portion of the posterior arch of the atlas. The atlas plane line should be 4 degrees above the listing line

APL > 4 degrees above the listing line

Superior malposition of the atlas

APL < 4 degrees

Inferior malposition of atlas

Atlas laterality 4 lines are constructed: Horizontal ocular orbit line (OOL) is drawn through similar matched points

of the orbits

Superior basic line (SBL) is drawn parallel to the OOL through the tip of the most superior occipital condyle

Inferior basic line (IBL) is drawn through the inferior tips of the lateral masses

Vertical median line (ViML) is drawn perpendicular to the OOL and through the center of the foramen magnum

The distances between the inferior lateral tip of each lateral mass and the VML should be equal.

The atlas is lateral toward the side of the greater measurement when the distances between the lateral inferior tip of each lateral mass and the VML are not equal

In addition, the SBL and IBL lines are thought to converge to the side of atlas laterality 70% of the time

Atlas rotation On a cervical film whose projection is directed vertical to the atlas (base

posterior)

Two lines are constructed

Transverse atlas line (TAL) is drawn through the transverse foramen bilaterally

Perpendicular skull line (PSL) is drawn through points representing the centers of the nasal septum and the basal process of the occiput

The angle of intersection of the two lines should be approximately 90 degrees.

The atlas is rotated posteriorly on the side of the larger angle created by the intersection of the PSL and TAL.

In addition, 70% of the time the atlas is posteriorly rotated to the side of the diverging superior basic line (SBL) and inferior basic line (IBL) on the frontal open mouth projection.

ATLAS MALPOSITION Frontal open-mouth projection

Four lines are constructed

Ocular orbit line (OOL) is drawn through a set of similar points of the orbit

Superior basic line (SBL) is drawn bilaterally through the jugular processes

Inferior basic line (IBL) is drawn through the lateral inferior tip of both lateral masses

Vertical median line (VML) is drawn perpendicular to the OOL through the center of the foramen magnum

VML should approximate the center of the odontoid process base

If the VML does not bisect the odontoid, the axis is laterally malpositioned to the side opposite the VML.

In addition, the center of the odontoid process base is compared with the center of the spinous process to assess for possible spinous deviation.

The direction and magnitude of spinous process lateral malposition may be different from the lateral malposition of the axis body (i.e., the body of the axis may be exhibit right laterality with left spinous deviation).

Cobb’s Method of Scoliosis Evaluation Cobb-Lippman method

Projection: AP spine.

End vertebrae Last segment that contributes to the spinal

curvature. Extreme ends of the scoliosis, where the

endplates tilt to the side of the curvature concavity

Endplate lines On the superior end vertebra, a line is drawn

through and parallel to the superior endplate

On the inferior end vertebra, a line is constructed in a similar manner through and parallel to the inferior endplate

This is the preferred method in scoliosis assessment

In patients with double scoliotic curves each component should be measured.

5° progression of a scoliosis between two successive radiographs is considered significant

Curvatures < 20° - No bracing or surgical intervention

Patient between 10 and 15 years of age, careful monitoring should be implemented to assess for progression of 5° or more in any 3-month period.

Curves between 20° and 40° - Bracing / Surgical intervention Curvature progression in an immature spine, or curvature in excess of 40° -

Surgical intervention

Risser-Ferguson Method of Scoliosis Evaluation

AP spine.

Apical vertebra

Most laterally placed segment in the curve

Vertebral body center

For each end vertebra and apical segment diagonals are drawn from opposing corners of the body to locate the body center

Connecting line

Two lines are constructed connecting the body centers of the apical segment with each end vertebra, and the resultant angle is measured

This method gives values approximately 25% lower than those of Cobb’s method (10°)

Advocated its use for larger curves

Coupled spinal motion sign

Spinal motion is not pure and occurs in directions other than the primary direction of movement

For example, on frontal cervical, thoracic, or lumbar lateral bending projections, the lateral tilting of each vertebra is accompanied by concurrent vertebral rotation

In the cervical and upper thoracic region the spinous processes rotate to the convexity of the curve

In the lumbar and lower thoracic region the spinous processes rotate to the concavity of the curve

The amount of coupled motion may be small and therefore radiographically imperceptible.

Alteration of the normal coupled motion occurs with aberrant intersegmental mechanics, muscle spasm, and vertebral fusion

Interpedicular Distance Coronal dimension of the spinal canal

Projection: AP cervical spine, thoracic spine, and lumbar spine.

The shortest distance between the inner convex cortical surfaces of the opposing segmental pedicles is measured

Spinal Level Maximum (mm)

Cervical spine 30

Thoracic spine 20

L1 TO L3 25

L4, L5 30

This is a useful measurement applied in the evaluation of spinal stenosis, congenital malformation, and intraspinal neoplasms

The maximum interpediculate distance may be increased as a result of pedicular erosion from an expanding spinal cord tumor (Elseberg-Dyke sign)

Thoracic Cage Dimension Straight back syndrome evaluation

Projection: Lateral chest.

The distance between the posterior sternum and the anterior surface of the T8 body is measured

Normal Sagittal Dimensions of the Thoracic Cage

Sex Average (cm) Minimum (cm) Maximum (cm)

Male 14 11 18

Female 12 9 15

Sagittal Dimensions of the Thoracic Cage in Straight Back Syndrome

Sex Average (cm) Minimum (cm) Maximum (cm)

Male 11 9 13

Female 10 8 11

Thoracic Kyphosis

Lateral thoracic spine

A line is drawn parallel to and through the superior endplate of the T1 body

A similar line is drawn through the inferior endplate of the T12 body.

Perpendicular lines to these endplate lines are then constructed

Intersecting angle is measured

Physiologic anterior vertebral body wedging accounts for the natural kyphotic curvature of the thoracic spine

Normal anterior wedging for each vertebral body is 4-5° or 2-3 mm

The wedging increases by almost 1 mm for each successive level, with approximately 45° of thoracic kyphosis accounted for by this wedging

Increased kyphosis Old age

Osteoporosis

Scheuermann’s disease

Congenital anomalies

Muscular paralysis

Cystic fibrosis

Reduction in kyphosis straight back syndrome

Lumbar Intervertebral Disc Angles

Lines are drawn through and parallel to each lumbar body endplate

The lines are extended posteriorly until they intersect

Intersecting angle is measured

Mean angle alteration Antalgia

Muscular imbalance

Normal Values for Lumbar Intervertebral Disc Angles

Disc Level Average Angle (°)

L1 8

L2 10

L3 12

L4 14

L5 14

Improper posture

Facet syndrome - Increased Angle

Acute discal injuries - Decreased Angle

Lumbar Intervertebral Disc Height

Lateral lumbar spine

Visual assessment

Disc height compared with the adjacent levels

Past experience

Hurxthal’s method The distance between the opposing endplates

at the midpoint between the anterior and the posterior vertebral body margins is measured.

Farfan’s method Anterior disc height (A) & posterior disc height (P) are measured and expressed as a

ratio to disc diameter (D)

These two ratios are then reduced to a ratio of each other

When segmental rotation is > 40° or lateral flexion is > 20°, these methods become unreliable.

Decreased disc height Disc degeneration

Post surgery

Post chemonucleolysis

Infection

Congenital hypoplasia

Lumbar spine - normal disc ratios increase

LI 0.17

L2 0.18

L3 0.20

L4 0.25

L5 0.28

Hadley’s S Curve Lumbar facet curve

Projection: Oblique, AP lumbar spine

Curvilinear line is constructed along the inferior margin of the transverse process and down along the inferior articular process to the apophyseal joint space

Line is then continued across the articulation to connect with the outer edge of the opposing superior articular process

The resultant configuration of this line will look like the letter S

The key region of the S is the normally smooth transition across the joint space

Abrupt interruption in the smooth contour of this line may indicate facet imbrication (subluxation)

Lumbar Gravity Line

The center of the L3 body is located by intersecting diagonals from opposing body corners

A vertical line is constructed through center point

Relationship to the upper sacrum is assessed

Center of gravity of the trunk passes through the center of the L3 body and continues vertically to intersect the sacral base

Normally the vertical line will pass through the anterior third of the sacral base.

If this line passes anterior to the sacrum by > 0.5 inch (> 10 mm), an increase in shearing stresses in an anterior direction between the lumbosacral apophyseal joints may be occurring.

Conversely, it has been suggested that a posterior shift in this gravity line may indicate increased weight bearing forces on these same lumbosacral joints that may also be active in the production of low back pain

Van Akkerveeken’s Measurement of Lumbar Instability

Projection: Lateral lumbar spine (neutral, flexion, extension).

Two lines are drawn through and parallel to opposing segmental endplates until they intersect posteriorly.

The distance from the posterior body margins to the point of intersection is then measured.

Alternatively, the displacement can be assessed by measuring the offset in the opposing body corners

Normal Measurements

There should be < 1.5 mm displacement, as determined by either measurement method

If there is > 1.5 mm (3mm) difference in measurement, then it is likely that nuclear, annular, and posterior ligament damage at the displaced segment is present

Lumbar Lordosis Lumbar curve, lumbar spinal angle, lumbar angle

Projection: Lateral lumbar spine.

Line is drawn through and parallel to the superior endplate of the first lumbar segment

Second line is drawn through the superior endplate of the first sacral segment

Perpendiculars are then created, and the angle at their intersection is measured

A wide variation exists within normal individuals. The average appears to be 50-60°

Lumbar spinal canal

Eisenstein's method

Lateral lumbar projection

Line is drawn connecting the tips of the superior and inferior articular processes of the same segment

The canal width (x) is expressed as the distance from the posterior body margin to the middle portion of the facet line

The canal dimension should not fall below 15 mm (although some use 14 mm or 12 mm as the cutoff)

Smaller measurements may indicate spinal stenosis

Spinal stenosis is more accurately assessed on axial MRI and CT images

RATIO METHOD

Frontal lumbar projection

Interpedicular distance is multiplied by sagittal width

Coronal width of the vertebrae is multiplied by the sagittal width

The product of the two canal measures is divided by the product of the two vertebral measures, expressing the canal size as a ratio of the vertebral body

In the lumbar spine, the canal ratio should not fall below 1:3

Meyerding’s Grading Method in Spondylolisthesis

The superior surface of the first sacral segment is divided into four equal divisions. The relative position of the posterior inferior corner of the L5 body to these segments is then made

The posterior inferior corner of the L5 body should be aligned with the posterior-superior corner of the first sacral segment.

The same assessment can be applied to other spinal levels by dividing the superior endplate of the segment below the spondylolisthesis into four equal spaces.

In spondylolisthesis, > 12° dynamic angulation or 8% translation on flexion-extension views is considered evidence of instability

The degree of anterolisthesis of the affected vertebral body can be categorized according to the division in which the posterior-inferior corner of the body lies

Grade 1 The posterior-inferior corner is aligned within the first division

Grade 2 The posterior-inferior corner is aligned within the second division

Grade 3 The posterior-inferior corner is aligned within the third division

Grade 4 The posterior-inferior corner is aligned within the fourth division

If the vertebral body has completely

slipped beyond the sacral promontory, the

condition is called spondyloptosis

Lumbosacral Angle Two lines

First, a horizontal line is made parallel to the bottom edge of the film

Second, an oblique line is drawn through and parallel to the sacral base.

Normal Values for Lumbosacral Angle

Position Average (°)

Standard Deviation

Minimum (°)

Maximum (°)

Upright 41 ±7 26 57

Sacral angle / Barge's angle

The angle of the superior margin of the sacrum from the horizontal plane, measured in the sagittal plane

lumbar lordosis increased if the sacral angle increased

Ullmann’s Line

Garland-Thomas line, right-angle test line

Projection: Lateral lumbar spine, lumbosacral

Parallel to and through the sacral base Perpendicular to the first line at the

anterior margin of the sacral base. The relationship of the L5 body to this perpendicular line is then assessed

Anterior margin of the L5 body crosses the perpendicular line,

Anterolisthesis

This is a useful line for detecting the presence of spondylolisthesis when there is poor visualization of the pars region

Upper Extremity Measurements

Acromioclavicular joint space AP or posteroanterior (PA) shoulder.

The joint space is measured at the superior (S) and inferior (I) borders, and the two values are averaged

Normal Values for Acromioclavicular Joint Space

Sex Average (mm) Minimum (mm) Maximum (mm)

Male 3.3 2.5 4.1

Female 2.9 2.1 3.7

Decreased joint space Degenerative joint disease

Increased joint space

Traumatic separation

Hyperparathyroidism Rheumatoid arthritis

Acromiohumeral joint space

AP shoulder.

The distance between the inferior surface of the acromion and the articular cortex of the humeral head is measured

Normal Values for Acromiohumeral Joint Space

Average (mm)

Minimum (mm)

Maximum (mm)

9 7 11

Narrowed space (<7mm)

Superior shoulder displacement, which is often secondary to shoulder impingement syndrome with rotator cuff tendonopathy.

Enlarged space (>11mm)

Dislocation

Joint effusion

Paralysis

Brachial plexus lesions (drooping shoulder)

Glenohumeral joint space

AP shoulder with external rotation.

The measurements are made at the superior, middle, and inferior aspects of the joint.

These are combined and averaged. Each distance is ascertained between the opposing articular surfaces

The average joint space is 4-5 mm

Joint space diminished

Degenerative arthritis, Calcium pyrophosphate

dihydrate (CPPD) crystal disease

Post-traumatic arthritis.

Widened space

Acromegaly Posterior humeral

dislocation.

Axial Relationships of the Shoulder

Humeral axial angle

AP shoulder with external rotation.

Humeral shaft line (A). A line is drawn through and parallel to the humeral shaft.

The average humeral angles are 60° for males and 62° for females

This relationship may be altered following a fracture, especially in the surgical neck.

Elbow - Anterior humeral line On the lateral elbow projection a line

drawn along the anterior surface of the humerus should intersect the middle third of the lateral condylar ossific center.

If the line passes anterior or posterior to the middle third of the lateral condyle, a fracture may be present

Radiocapitellar Line

Radiocarpal line

Lateral elbow.

A line is drawn through the center of and parallel to the long axis of the radius and is extended through the elbow joint.

This line should pass through the center of the capitellum in all stages of flexion of the elbow

This assists in determining the presence of radial head subluxation (pulled elbow) or dislocation

Axial Relationships of the Wrist PA and lateral wrist.

Radioulnar articular line (A). A tangential line is drawn from the tip of the radial styloid to the base of the ulnar styloid.

Radial shaft line (B). A line is drawn through and parallel to the shaft of the radius.

Radioulnar angle (I). The ulnar side angle between the two lines is measured.

Normal Values for Axial Relationships of the Wrist

Angle Average (°) Minimum (°) Maximum (°)

PA radioulnar 83 72 95

Lateral radius 86 79 94

These lines and constructed angles aid in the assessment of radioulnar deformities, especially those caused by displaced fractures

Hand - Capitolunate sign

On the lateral wrist projection, lines are drawn to approximate the long axes of the lunate and capitate.

Assessment assists in determining the presence of fracture or dislocation.

Scapholunate angle

(scaphoid tilt) On the lateral wrist projection, lines are

drawn to approximate the long axes of the scaphoid and lunate.

If the angle is greater than 80 and the lunate is also extended (dorsiflexed), dorsal intercalated segmental instability (DISI) is suggested.

Metacarpal Sign PA hand

A line is drawn tangentially through the articular cortex of the fourth and fifth metacarpal heads

The line should pass distal to or just touch the third metacarpal head

Postive in

Turner’s syndrome

Fracture deformity

Pseudo/ pseudo-pseudo hypoparathyroidism

Metacarpal index

Determined by dividing the length of each of the last four metacarpals by the width of its midpoint and averaging the values

Marfan's patients are often grater than 8.4, while normals are less than 8.

Method 2 The outer and inner diameters of the

metacarpal bone is measured, as shown below. From these measurements, the Combined Cortical Thickness (CCT) and the Metacarpal Index (MCI) are easily calculated

CCT = L1 - L2

MCI = CCT / L1

Radiolunate angle (lunate tilt)

On the lateral wrist projection, lines drawn to approximate the long axes of the radius and lunate should be parallel.

If the lunate is flexed more than 15 degrees, volar intercalated segment instability (VISI) is suggested.

If the angle is greater than 10 degrees in extension, dorsal intercalated segment instability (DISI) is suggested.

Occasionally VISI and usually DISI occur with scapholunate dissociation

VISI is also related to triquetrolunate dissociation

Radioulnar variance

On the anteroposterior wrist projection, the distal ulnar articular surface should align with the inner portion of the distal radial articular surface.

Short ulna Avascular necrosis of the lunate (Kienbock's disease)

Greater carpal stress distribution to the radius

Long ulna Greater carpal stress distribution to the ulna.

Differences of less than 5 mm are probably not significant.

Teardrop Distance Medial joint space of hip.

The distance between the most medial margin of the femoral head and the outer cortex of the pelvic teardrop is measured

ABNORMAL MEASUREMENT

• >11 mm or • > 2 mm discrepancy from right to

left (Waldenstrom’s sign)

Left to right discrepancies of > 1 mm will be present in 90% of hip joint

effusions.

Legg-Calve-Perthes disease

Septic arthritis

Other inflammatory diseases.

Normal Values for Teardrop Distance

Average (mm)

Minimum (mm)

Maximum (mm)

9 6 11

Hip Joint Space Width

Three measurements are made of the joint cavity

Superior joint space: Space between the most superior point on the convex articular surface of the femur and adjacent acetabular cortex.

Axial joint space: Space between the femoral head and acetabulum immediately lateral to the acetabular notch.

Medial joint space (teardrop distance): Space between the most medial surface of the femoral head and opposing acetabular surface

Normal Values for Hip Joint Space Width

Space Average (mm) Minimum (mm) Maximum (mm)

Superior 4 3 6

Axial 4 3 7

Medial 8 4 13

The superior and axial compartments are approximately equal (4 mm), The

medial space is twice the distance (8 mm)

Superior joint space Reduction Degenerative joint disease

Axial joint space

Degenerative arthritis Inflammatory arthritis (RA)

Medial joint space

Degenerative or inflammatory arthritis

Acetabular Depth A line is drawn from the superior

margin of the pubis at the symphysis joint to the upper outer acetabular margin.

The greatest distance from this line to the acetabular floor is measured

An acetabular depth < 9 mm in females and < 7 mm in males is considered

to be shallow and dysplastic, which may be a factor in precipitating

degenerative joint disease of the hip.

Acetabular center-edge angle

CE angle, CE angle of Wiberg.

A vertical line is drawn through the center point of the femoral head.

Another line is constructed through the femoral head center to the outer upper acetabular margin.

The angle formed is then measured.

Shallow angle Acetabular dysplasia

degenerative joint disease.

It provides a measure of coverage of the femoral head, which means the amount of the acetabulum primarily concerned with weight bearing

Symphysis Pubis Width The measured distance is between the

opposing articular surfaces, halfway

Normal Values for Acetabular Depth

Space Average (mm) Minimum (mm)

Maximum (mm)

Male 13 7 18

Female 12 9 18

Normal Values for Center-Edge Angle

Average (°) Minimum (°) Maximum (°)

36 20 40

Normal Values for Symphysis Pubis Width

Sex Average (mm) Minimum (mm) Maximum (mm)

Male 6 4.8 7.2

Female 5 3.8 6

between the superior and inferior margins of the joint

Widening of the symphysis

cleidocranial dysplasia, bladder exostrophy

Hyperparathyroidism

post-traumatic diastasis

inflammatory resorption ankylosing spondylitis

osteitis pubis

gout

Presacral Space

Retrorectal space

The gray soft tissue density located between the anterior surface of the sacrum and the posterior wall of the rectum is assessed

The most consistent measurement was obtained at the level opposite the S3-S4 disc space

An increase measurement

sacral destruction Tumor

infection

sacral fracture and associated hematoma

inflammatory bowel disease (in which there is thickening of the intestinal wall).

Acetabular Angle

Normal Values for Acetabular Angle in 1-Year-Old

Average (°) Minimum (°)

Maximum (°)

20 12 29

Normal Values for Presacral Space

Age Average (mm)

Minimum (mm)

Maximum (mm)

Children (1-15 years)

3 1 5

Adults 7 2 20

A transverse line is drawn through the right and left triradiate cartilages at the pelvic rim

A second oblique line connecting the lateral and medial acetabular surfaces is then constructed

The angle of intersection is measured

Increased acetabular angle

acetabular dysplasia congenital hip dislocation

Decreased acetabular angle

Down’s syndrome.

Acetabular index Horizontal line is drawn through

the right and left triradiate cartilage (Hilgenreiner's Line).

Another line is drawn along each of the acetabuli to intersect the horizontal triradiate cartilage line

Dividing the hip into 4 quadrants.

The proximal medial femur should be in the lower medial quadrant, or the ossific nucleus of the femoral head, if present (usually observed in patients aged 4-7 month), should be in the lower medial quadrant.

The acetabular index is the angle between the Hilgenreiner line and a line drawn from the triradiate epiphysis to the lateral edge of the acetabulum.

The angles of intersection (x°) should not exceed standards based on age:

@ Birth < 36 degrees in females,

< 30 degrees in males;

6 months < 28 degrees in females,

< 25 degrees in males;

1 year < 25 degrees in females,

24 degrees in males;

7 years < 19 degrees in females, < 18 degrees in males

Enlarged angle Acetabular dysplasia Congenital dislocation of the hip

Shallow angle - Down syndrome

Iliac Angle and Index A line is drawn through the

triradiate cartilage at the pelvic rim

A second line is constructed tangential to the most lateral margin of the iliac wing and iliac body

Iliac index: This is the sum of both the iliac angles and the acetabular angles divided by 2.

The iliac index is most useful in the determination of Down’s syndrome.

When the index is < 60, Down’s syndrome is probable; when the index is 60-68, the syndrome is possible; if > 68, the syndrome is unlikely

Normal Values for Iliac Angle

Age Average (°) Minimum (°) Maximum (°)

0-3 months 44 35 58

3-12 months 55 43 67

Normal Values for Iliac Index

Age Average (°) Minimum (°) Maximum (°)

0-3 months 60 48 87

3-12 months 81 68 97

Measurements of Protrusio Acetabuli

Köhler’s Line

A line is constructed tangentially to the cortical margin of the pelvic inlet and outer border of the obturator foramen.

The relationship of the acetabular floor to this line is assessed

The acetabular floor should not cross this line and usually lies laterally to it.

If the acetabular floor crosses the line, then protrusio acetabuli is present. The most common causes

Idiopathic form

Rheumatoid arthritis

Paget’s disease

Ankylosing spondylitis

Shenton’s Line

Makka’s line, Menard’s line.

A curvilinear line is constructed along the undersurface of the femoral neck and is continued across the joint to the inferior margin of the superior pubic ramus.

The constructed line should be smooth, especially in the transition zone between the femoral neck and superior pubic ramus.

Occasionally, a small portion of the inferior femoral head may just cross the line

Interrupted, discontinuous in Hip dislocation, Femoral neck fracture

Slipped femoral capital epiphysis.

Iliofemoral Line A curvilinear line is constructed along the

outer surface of the ilium, across the joint, and onto the femoral neck

A small portion of the superior femoral head may cause a slight convexity in the line.

The most important normal feature is that the line should be bilaterally symmetrical.

A discrepancy in symmetry may be the result of congenital dysplasia, slipped femoral capital epiphysis, dislocation, or fracture

Femoral Angle Femoral angle of incidence, femoral neck angle,

Mikulicz’s angle.

Two lines are drawn through and parallel to the midaxis of the femoral shaft and femoral neck.

The angle subtended is then measured.

Skinner’s Line

A line is drawn through and parallel to the axis of the femoral shaft.

A second line is constructed at right angles to the shaft line and tangential to the tip of the greater trochanter.

The relationship of the fovea capitis to this trochanteric line is assessed.

The fovea capitis should lie above or at the level of the trochanteric line.

The fovea lies below this line when there is a superior displacement of the femur relative to the femoral head.

The most common causes are fracture and conditions leading to coxa vara.

Klein’s Line A line is constructed tangential to the outer margin of the femoral neck. The degree of overlap of the femoral head will be apparent.

Comparison should be made with the opposite side

Generally there will be the same degree of overlap of the femoral head

In most normal hips the outer margin of the femoral head will be lateral to the line.

This line can be drawn on both the AP and frog-leg projections

If the femoral head does not overlap the line or if there is asymmetry from side to side, then slippage of the femoral capital epiphysis should be suspected.

Pelvic misalignment

Innominate rotation

On the weight- bearing frontal pelvic projection

Femoral head line (FHL) is drawn along the superior margins of the femoral heads bilaterally.

A perpendicular line from the FHL is constructed to intersect the second sacral tubercle and should pass through the center of the pubic symphysis when extended interiorly.

If the perpendicular line intersects the pubic bone instead of the symphysis, the innominate is externally rotated on the side the line crosses through. The innominate on the opposite side is internally rotated.

Rotation can be double-checked by measuring the width of the ilium (a) and the obturator foramen (b).

External rotation of the innominate, using the posterior superior iliac spine (PSIS) as a reference point, is accompanied by a narrower ilium width and a wider obturator foramen on the ipsilateral side. Internal rotation is associated with a wider ilium and narrower obturator width ipsilaterally.

Innominate flexion-extension. On the weight-bearing frontal pelvic projection, the distance from the top of the iliac crest to the inferior margin of the ischial tuberosity should be bilaterally similar

Sacrum rotation. On the weight-bearing frontal pelvic projection, the distances from the lateral margins of the sacrum to the second sacral tubercle (c and d) are measured parallel to the FHL and should be similar.

Leg length inequality. On the frontal weight bearing pelvic projection, a line is drawn parallel to the lower margin of the film to the superior margin of the highest femoral head.

The line should approximate both femoral heads if the legs are of equal length

The vertical measurement of the innominate is larger on the flexed side (PSIS has moved posterior and inferior) and smaller on the extended side (the PSIS has moved anterior and superior).

The sacrum is rotated posteriorly on the wider side and anteriorly on the narrower side.

If the line constructed parallel to the bottom of the film does not approximate the femoral heads bilaterally, the line is drawn to the higher femoral head, and the distance from the line to the lower femoral head estimates the measured leg length deficiency.

Flexed (PI) or externally rotated (EX) innominate will decrease the leg length discrepancy when the innominate misalignment is corrected on the ipsilateral side of the short leg. In other words, correction of flexed or externally rotated innominate raises the ipsilateral femoral head

Conversely, an extended (AS) or internally (IN) rotated innominate will increase the leg length discrepancy when corrected on the ipsilateral side of the short leg. The opposite will be noted if the short leg is on the contralateral side of the innominate misalignment. Axial Relationships of the Knee AP knee.

Four lines and two angles are drawn

Femoral shaft line (A). A line is drawn through and parallel to the midaxis of the femoral shaft.

Tibial shaft line (B). A line is drawn through and parallel to the midaxis of the tibial shaft.

Femoral condyle line (C). A line is drawn through and tangential to the articular surfaces of the condyles

Tibial plateau line (D). A line is drawn through the medial and lateral tibial plateau margins

Femoral angle (FA). This is the angle formed between the femoral shaft and femoral condyle lines.

Tibial angle (TA). This is the angle formed between the tibial shaft and tibial plateau lines

Normal Values for Axial Relationships of the Knee

Angle Average (°) Minimum (°) Maximum (°)

Femoral 81 75 85

Tibial 93 85 100

Significance.

These angles will be altered in fractures and other deformities about the knee.

Patellar Position

Patella alta evaluation

Lateral knee (semiflexed) Patellar length (PL). This is the greatest diagonal dimension between the

superior and the inferior poles.

Patellar tendon length (PT). The distance measured is between the insertion points of the posterior tendon surface at the inferior patellar pole and the notch at the tibial tubercle.

Normal Measurements.

Patellar length and patellar tendon length are usually equal to each other.

A normal variation up to 20%

> 20% - patella alta

• chondromalacia patellae.

A low-riding patella (patella baja)

Polio

Achondroplasia

juvenile rheumatoid arthritis

tibial tubercle transposition

Patellar Malalignment

Patellar tracking, patellar subluxation, patellofemoral joint incongruence.

Tangential knee (skyline)

Patella apex The patella is centered when its apex is directly above the

deepest section of the intercondylar sulcus. Sulcus angle By drawing lines from the highest points on the medial and

lateral condyles to the lowest point of the intercondylar sulcus, an angle is

formed. Normally, this should be 138° ± 6°. Larger angles (shallow intercondylar

groove) predispose the individual to subluxation and dislocation.

Lateral patellofemoral joint index: The narrowest medial joint space measurement is divided by the narrowest lateral joint space measurement.

This index is normally ≤ 1.0. A value > 1.0 is noted in patients with chondromalacia patellae.

Lateral patellofemoral angle. A line tangential to the femoral condyles is intersected by a line joining the limits of the lateral facet.

The angle is normally open. In patellar subluxation these lines

are parallel or open medially.

Significance.

The combined use of these measurements may reveal contributing causes to patellofemoral joint pain syndromes and instability

Axial Relationships of the Ankle

Four lines and two angles are constructed. Tibial shaft line (A). A line is drawn through and parallel to the tibial shaft.

Medial malleolus line (B). A line is drawn tangential to the articular surface of the medial malleolus.

Lateral malleolus line (C). A line is drawn tangential to the articular surface of the lateral malleolus.

Talus line (D). A line is drawn tangential to the articular surface of the talar dome.

Tibial angle (I). The angle is formed medially between the medial malleolus line and talus line.

Fibular angle (II). The angle is formed

laterally between the lateral malleolus line

and talus line

Normal Values for Axial Relationships of the Ankle

Angle Average (°)

Minimum (°)

Maximum (°)

Tibial (I) 53 45 65

Fibular (II) 52 43 63

Significance.

These angles will be altered in fractures of the malleoli, ankle mortise instability, and tibiotalar slant deformities.

The tibiotalar joint space is measured at the lateral and medial joint margins.

This should be done on varus-valgus stress studies, on which there should not be > 3 mm difference between the normal and injured sides.

Talar tilt is assessed by drawing a line tangential to the talar dome and another line along the adjacent tibial surface.

In the neutral position, an angle > 6° indicates significant ligamentous injury.

On valgus-varus stress views, the normal range is 5-23°.

A difference between right and left of > 10° also indicates significant ligamentous damage.

An anterior drawer of 4 mm is another indicator of instability.

Boehler’s Angle

Axial relationships of the calcaneus, tuber angle.

Lateral foot, lateral calcaneus.

The three highest points on the superior surface of the calcaneus are connected with two tangential lines.

The angle formed posteriorly is then assessed

Normal Measurements.

The angle formed posteriorly averages between 30° and 35° in most normal subjects but may range between 28° and 40°.

Any angle < 28° is abnormal.

The most common cause for an angle < 28° is a fracture with displacement through the calcaneus.

Dysplastic development of the calcaneus may also disturb the angle.

Heel Pad Measurement

Two lines are drawn

First line connecting the superior tuborosity to superior most point of anterior process of calcaneum

Parallel to above line touching plantar surface of calcaneum

Shortest perpendicular distance to second line is measured Normal Values for Heel Pad

Measurement

Sex Average (mm)

Maximum (mm)

Male 19 25

Female 19 23

• Increased in

• Obesity

• myxedema

• Acromegaly

• Local inflammation

First metatarsal angle

On the anteroposterior foot projection, lines drawn to approximate the long axes of the first metatarsal and proximal first phalanx should form an angle (x°) of less than 15 degrees.

An increased angle indicates a

hallux valgus deformity.

Meary's angle

On the lateral foot projection, lines drawn to approximate the longitudinal axis of the first metatarsal and talus should be parallel

If the lines are not parallel and form an angle that is greater than 0 degrees, forefoot cavus deformity is indicated.

Calcaneal pitch

A line is drawn from the plantar most surface of the calcaneus to the inferior border of the distal articular surface.

The angle made between this line and the transverse plane (or the line from the plantar surface of the calcaneus to the inferior surface of the 5th metatarsal head) is the calcaneal pitch.

A decreased calcaneal pitch is consistent with pes planus.

Unfortunately, there have been differing opinions between authors concerning the normal range of calcaneal pitch 18 to 20°is generally considered normal (12), although measurements ranging from 17 to 32° have been reported to be normal

Lateral Talocalcaneal Angle

The lateral talocalcaneal angle is the angle formed by the intersection of the line bisecting the talus with the line along the axis of the calcaneus on lateral weight bearing views. A line is drawn at the plantar border of the calcaneus (or a line can be drawn bisecting the long axis of the calcaneus).

The other line is drawn through two midpoints in the talus, one at the body and one at the neck. The angle is formed by the intersection of these axes.

The normal range is 25-45 degrees.

An angle over 45 degrees indicates hindfoot valgus, a component of pes planus

Kite's angle

AP talocalcaneal angle Angle formed by the longitudinal axis of the

Calcaneus and the Talus

Kite Angle < 15° : Tendency to supine rearfoot

15° < Kite Angle < 25° : Normality range

Kite Angle > 25°: Tendency to prone rearfoot

REFERENCE

CLINICAL IMAGING – Dennis M.Marchiori Essentials of Skeletal Radiology 3rd Edition -

Terry R. Yochum B.S., D.C., D.A.C.B.R., F.C.C.R. (C), F.I.C.C., Fellow, A.C.C.R