Lateral skull.

The pineal gland must be visible as a result of calcium deposition before the following four measurements are made: (1) (Fig. 2-2)

Measurements A and B are used to assess anterior or posterior pineal displacement, whereas measurements C and D are used to assess superior or inferior displacement.

An alternative and more accurate method for pineal gland localization is the Pawl-Walter method. (3)

Lateral skull.

Two measurements are made: the greatest AP diameter and the greatest vertical diameter. The AP value is the widest distance between the anterior and posterior surfaces of the pituitary fossa. The vertical dimension is between the fossa floor and the plane between the opposing surfaces of the anterior and posterior clinoid processes. (4,5) (Fig. 2-3)

The AP dimension averages about 11 mm, with a normal range of 5-16 mm. The vertical measurement averages about 8 mm, with a normal range of 4-12 mm. (4,5,6) (Table 2-1) In children these values will be progressively smaller with decreasing chronologic age.

All lateral flexion and rotation of the skull should be eliminated for these measurements to be accurate.

Lateral skull.

Three points are located and joined together by two lines; the subsequent angle is measured. The three points are the nasion (frontal-nasal junction), the center of the sella turcica (midpoint between the clinoid processes), and the basion (anterior margin of the foramen magnum). (Fig. 2-4)

The average normal angle subtended by these two lines is 137°, with a normal variation of 123-152°. (8) (Table 2-2)

None.

Lateral skull; lateral cervical spine.

A line is drawn from the posterosuperior margin of the hard palate to the most inferior surface of the occipital bone. (9) The relationship of the odontoid apex to this line is then examined. (Fig. 2-5)

In 90% of individuals the odontoid apex should not lie above this line > 8 mm in males and > 10 mm in females. (9) In children younger than 18 years, these maximum values diminish with decreasing chronologic age.

Of all methods used to evaluate for basilar impression on the lateral projection, McGregor’s line appears to be the most accurate and reproducible. (10)

Lateral skull; lateral cervical spine.

A line is constructed from the posterior margin of the hard palate to the posterior aspect of the foramen magnum. The relationship of this line to the tip of the odontoid process is then assessed. (11) (Fig. 2-6)

In the majority of patients the tip of the odontoid process should not project above this line; however, a normal variation of 3 mm above this line may occur. (8) A measurement of ≥7 mm is definitely abnormal.

This relationship can also be evaluated on lateral cervical views but is best done on lateral skull films, preferably with computed tomography (CT). To locate the posterior aspect of the foramen magnum, identify the inner table of the occipital bone, follow it anteriorly, and observe for an oblique cortical white line crossing the diploe to merge with the outer table. This should be found slightly posterior to the plane of the atlas spinolaminar junction.

Lateral skull.

A line is drawn between the anterior (basion) and posterior (opisthion) margins of the foramen magnum. Two assessments are then made in relation to this line: (a) the occipital bone and (b) the odontoid process. (Fig. 2-7)

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. (10,12)

A true lateral view with no lateral flexion distortion should be obtained for this positional line to be applied.

AP open mouth.

The digastric groove medial to the base of the mastoid process is located on each side and a line is drawn between them. The vertical distance to the odontoid apex and atlanto-occipital joints is then measured. (Fig. 2-8)

The digastric line-odontoid apex measurement averages 11 mm but may range between 1 and 21 mm. The odontoid should not project above this line. The digastric line-atlanto-occipital joint average measurement is 12 mm, with a normal range between 4 and 20 mm. (10,13) (Table 2-3)

Computed tomography (CT) evaluation is the most accurate method for obtaining clear visualization of the necessary anatomic landmarks.

Lateral skull; lateral cervical spine.

A line is drawn from the tuberculum sellae to the internal occipital protuberance. The vertical distance between this line and the apex of the odontoid is measured. (14) (Fig. 2-9)

See Table 2-4.

None.

Lateral skull; lateral cervical spine.

None.

Lateral cervical spine; lateral skull.

Four osseous landmarks are located: the basion, opisthion, and anterior and posterior arches of the atlas. Two measurements are then made: The first is the distance between the basion and the posterior arch at the spinolaminar junction (B-P), and the second is the distance between the opisthion and the posterior margin of the anterior arch (O-A). The ratio of these two measurements (B-P:O-A) is then calculated. (16) (Fig. 2-11)

In the normal individual the ratio is always < 1.

This relationship can be assessed only when there are no associated fractures or dislocations of the atlas and odontoid process.

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. (Fig. 2-12)

A small, insignificant difference exists between males and females. The measurement is slightly increased in normal children. (1,2) (Table 2-6) In flexion the shape of the interspace takes on a V configuration, whereas in extension it has an inverted V pattern. (3,4)

Flexion is the optimum view to assess the interspace, because in this position the most stress is placed on the transverse ligament of the atlas.

Lateral skull; lateral cervical spine.

Two lines are drawn and the resultant angle measured. The first line is drawn from the posterior aspect of the hard palate to the posterior margin of the foramen magnum (Chamberlain’s line). The second line is drawn through the midpoints of the anterior and posterior tubercles of the atlas (atlas plane line). The angle formed posteriorly is then measured. (7) (Fig. 2-13)

The posterior angle formed by these two lines should be 13°. If this angle is > 13°, it is abnormal. (2)

The accuracy of this measurement is affected in individuals with acute neck pain owing to muscular spasm.

Lateral cervical spine.

The posterior vertebral body surfaces are connected with a continuous line that traverses the intervertebral disc. A straight line cannot be drawn because of the normal concavity of the posterior surface. The key landmarks are the alignment of the superior and inferior posterior body corners. (Fig. 2-14)

Normally, there is a smooth vertical alignment of each posterior body corner.

Flexion and extension films are especially useful in determining disruptions in George’s line. (8,9) The posterior body line can be incorporated with other complex measuring systems to assess stability. (10,11) Care should be taken to eliminate positional rotation, because this will create a projectional disruption of the line at consecutive levels (stair stepping). This line can be applied throughout the entire spine.

Lateral cervical spine (neutral, flexion, extension).

The cortical white line of the spinolaminar junction is first identified at each level C1 to C7. Each spinolaminar junction will be curved slightly anteriorly from superior to inferior. For consistency, the most anterior part of the convexity is compared between levels. (Fig. 2-15)

When each spinolaminar junction point is joined, a smooth arc-like curve results. At the C2 level, the spinolaminar junction line in children should not be > 2 mm anterior to this line.

None.

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. (17) (Fig. 2-16)

Measurements vary according to the cervical level. (18) (Table 2-7) Values will be altered in children. (17,19)

None.

AP open mouth; cervical spine.

The lateral margins of the atlas lateral masses are compared to the opposing lateral corner of the axis articular surface. (Fig. 2-17)

These two landmarks should be in vertical alignment.

None.

Lateral cervical spine (neutral).

A vertical line is drawn through the apex of the odontoid process. (27) (Fig. 2-18)

This line should pass through the C7 body.

None.

Cervical spine, neutral.

Numerous methods have been devised. (28,29,30,31,32,33,34,35) Some are described here.

See Table 2-8.

The position of the head is a critical factor in determining the lordosis. If the chin is lowered, tucked downward, or retracted 1 inch, the effect is to straighten the lordosis. (36,37,38)

Lateral cervical spine (flexion, extension).

Two lines are constructed on each film. The first line is drawn along the posterior surface of the axis. The second line is drawn along the posterior surface of the C7 body until it intersects the axis line. (40) (Fig. 2-20)

None.

Lateral cervical spine (neutral, flexion, extension).

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 are the anterior arch of the atlas; the inferior corners of the axis and C3; the superior corner of C4; and the inferior corners of C5, C6, and C7. (43,44) At C2-C3 this is called the RPI; behind the larynx, the RLI (C4-C5); and behind the trachea (C5-C7), the RTI. (Fig. 2-21)

Measurements will vary according to the level being measured and the position of the patient at the time of the exposure. (43,44) (Table 2-9)

The values at the C4 and C5 levels may alter, depending on the position of the larynx, which may change with swallowing, screaming, axial rotation, and lateral flexion. (44) There is no difference between the sexes, and the values are not altered significantly by radiographic magnification. (44) Patients > 180 lb (82 kg) may have a space 1 mm greater than the normal range, and patients older than 70 years have spaces of 1 mm less than normal. (44) No more than a 1-mm change occurs in the measurement between flexion and neutral. (43) Anterior degenerative osteophytes may cause deflection of the pharyngeal contour.

AP spine.

This is the preferred method in scoliosis assessment. In patients with double scoliotic curves each component should be measured. Care should be taken to ensure that common landmarks are used in progressive evaluations. Interobserver errors in measurement range up to 10°, which is a problem because a 5° progression of a scoliosis between two successive radiographs is considered significant when deciding on therapeutic options. (1,2,3)

AP spine.

This method gives values approximately 25% lower than those of Cobb’s method (10°), and some investigators have advocated its use for larger curves; but this practice is to be discouraged. (6) (See Chapter 4.)

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, and the resultant angle is measured at the intersection of the lines. (Fig. 2-24)

Measurements vary according to age and sex. (9) (Tables 2-10 and 2-11)

Frequently the vertebral bodies at the ends of the thoracic spine will not be clearly visible. In these circumstances the first visible segment will suffice but may alter the angular value. Interobserver measurement errors up to 11° are common. (2) Physiologic anterior vertebral body wedging accounts for the natural kyphotic curvature of the thoracic spine. (10,11) This normal anterior wedging for each vertebral body is 4-5° or 2-3 mm. (11,12,13,14) The wedging increases by almost 1 mm for each successive level, with approximately 45° of thoracic kyphosis accounted for by this wedging. (11)

Lateral chest.

The distance between the posterior sternum and the anterior surface of the T8 body is measured. (Fig. 2-25)

The sagittal dimension will normally vary slightly. (18) (Table 2-12)

None.

Lateral lumbar spine.

A number of methodologies have been described, but only two are presented. (1,2)

Considerable variation exists in disc height, according to the lumbar interspace being assessed.

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

Lateral lumbar spine.

Lines are drawn through and parallel to each lumbar body endplate; the lines are extended posteriorly until they intersect. The angles formed at each interspace are then measured. (Fig. 2-27)

Measurements vary according to the lumbar level. (6) (Table 2-14)

An alternative method of measurement includes the vertebral bodies in the calculation. (7)

Lateral lumbar spine.

A line is drawn through and parallel to the superior endplate of the first lumbar segment. A 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. (Fig. 2-28)

A wide variation exists within normal individuals. However, the average appears to be 50-60°. (6,7)

Some investigators prefer to use the inferior endplate of the L5 body to eliminate the effects of an altered sacral position. (8)

Lateral lumbar spine.

Two lines are drawn, and the angle formed is measured. For the first line, the centers of the L3 and L5 bodies are located by intersecting diagonal lines from opposing corners for each of the two vertebra. A line is then constructed joining the midpoints of these two bodies. Next the midpoint of the first sacral segment is located in a similar manner, and a second line is drawn between the L5 and S1 midpoints. The posterior angle thus formed is measured. (Fig. 2-29)

A wide variation in this angle exists. (16) (Table 2-15)

There appear to be small changes in this angle between the recumbent and the upright positions.

Lateral sacrum, lumbar spine.

Two lines are drawn. First, a tangential line is drawn parallel to and through the posterior margin of the first sacral segment. Second, a vertical line is drawn, intersecting the tangential sacral line. The angle formed is then measured. (Fig. 2-30)

A wide variation in this measurement occurs. (16) (Table 2-16)