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© Florence P. Kendall 2005. Author grants permission to reproduce for personal use but not for sale

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© Florence P. Kendall 2005. Author grants permission to reproduce for personal use but not for sale

DEFINITIONS

The following definitions relate to the trunk and hip joints. They are considered to be essential for understanding the functions of the trunk muscles.

The trunk, or torso, is the body excluding the head, neck, and limbs. The thorax (i.e., rib cage), the abdomen (i.e., belly), the pelvis (i.e., hip bones), and the low back are all parts of the trunk. The term trunk raising may be used to describe raising the trunk against gravity from various positions: from face-lying (i.e., prone), trunk raising backward; from side-lying, trunk raising sideways; and from back-lying (i.e., supine), trunk raising forward. The term may also apply, in standing, to raising the trunk from positions of forward bending, side bending, or backward bending to the erect position.

The thorax is elevated (chest lifted upward and forward) by straightening the upper back, bringing the rib cage out of a slumped position. The thorax is depressed when sitting or standing in a slumped position, or it may be pulled downward by the action of certain abdominal muscles.

The trunk is joined to the thighs at the hip joints. The movement of hip flexion means bending forward at the hip joint. It may be done by bringing the front of the thigh toward the pelvis, as in forward leg raising, or by tilting the pelvis forward toward the thigh, as in the sit-up movement. (Positions of the pelvis in good and faulty postural alignment are illustrated on pp. 173 and 64.)

JOINTS OF THE VERTEBRAL COLUMN

Vertebral joints include the bilateral synovial joints of the vertebral arches, where the inferior facets of one vertebra join with the superior facets of the adjacent vertebra, and the fibrous joints between successive vertebral bodies united by intervertebral fibrocartilaginous disks. Movement between two adjacent vertebrae is slight, and this movement is determined by the slope of the facets and by the flexibility of the intervertebral disks. The range of motion of the column as a whole, however, is considerable, and the movements permitted are flexion, extension, lateral flexion and rotation.

The joints between the first two vertebrae of the column are exceptions to the general classification. The atlanto-occipital joint, which is between the condyles of the occipital bone and the superior facets of the atlas, is classified as a condyloid joint The movements permitted are flexion and extension with very slight lateral motion. The atlanto-axial joint is composed of three joints. The lateral two fit the general description of the joints of the vertebral column. The third, a median joint formed by the dens of the axis and the fovea dentis of the atlas, is classified as a trochoid joint and permits rotation.

Forward bending and backward bending are used to assess the range of motion in flexion and extension of the spine. Several variations of these tests exist.

RANGE OF MOTION IN TRUNK FLEXION

The forward-bending, long-sitting position involves hip joint flexion along with back flexion. One must try to disregard the hip joint movement when observing the contour of the back. (See Normal Range of Motion, p. 174.)

Range of motion and contour of the back may also be observed by having a subject bend forward from the standing position. As a test position, however, this has certain disadvantages. If the pelvis is not level or is rotated, the plane of forward bending will be altered, and the test will not be as satisfactory as that in the long-sitting position in which the pelvis is level and rotation is better controlled.

RANGE OF MOTION IN TRUNK EXTENSION

Because the low back muscles are seldom weak, the range of back extension may be determined by the active strength test in the prone position. (See p. 181.) Whether the range of motion is normal, limited, or excessive, the subject is capable of moving through the existing range. The anterosuperior-iliac spines should not be lifted from the table during back extension, because doing so adds hip extension to the back extension range of motion. (See figures below.)

Back extension often is checked in the standing position. The test is useful as a gross evaluation, but it is not very specific. Swaying forward at the hips is almost a necessity for balance when bending backward, but doing so adds the element of hip extension to the test, or the knees must bend somewhat if the hip does not extend.

To assess flexion of the back without associated hip joint flexion, place a subject in the supine position, resting on the forearms with elbows bent at right angles and arms close to the body. If the subject can flex the spine in this position with the pelvis flat on the table (i.e., no hip flexion), the range of motion is considered to be good.

Sometimes it is necessary to ascertain the range of back flexion passively. With the subject in the supine position, the examiner lifts the upper trunk in flexion to completion of the subject's range of motion. The subject must relax for the examiner to obtain complete flexion.

Similar to the test to determine range of motion in spine flexion, a test can be done to determine the range in spine extension. The subject lies prone on a table, resting on the forearms with elbows bent at right angles and arms close to the body. If the subject can extend the spine enough to prop up on the forearms with the pelvis flat on the table (i.e., anterosuperior-iliac spines on the table), the range of motion in extension is considered to be good.

Sometimes it is necessary to determine the amount of passive back extension with the subject prone on the table by lifting the subject up in extension through the available range of motion.

Scapular instability and, specifically, serratus anterior weakness can interfere with the back extension test, as seen in the accompanying photograph.

| Note: Push-ups shouldnot be done by individuals I who exhibit this type ofweakness.

FLEXION

According to Stedman's Medical Dictionary, "to flex" means to bend and "to extend" means to straighten (1). However, some ambiguity exists when describing the positions and movements of the cervical and lumbar spines.

In the cervical region, flexion of the spine is movement in the direction of decreasing the normal forward curve. Movement continues to the point of straightening or flattening this region of the spine, but it normally does not progress to the point of the spine curving convexly backward. (For exceptions, see Chapter 4, pp. 146 and 153.)

In the thoracic region, flexion of the spine is movement in the direction of increasing the normal backward curve. In normal flexion, the spine curves convexly backward, producing a continuous, gently rounded contour throughout the thoracic area. (For exceptions, see Chapter 4, p. 153).

In the lumbar region, flexion of the spine is movement in the direction of decreasing the normal forward curve. It progresses to the point of straightening or flattening the lower back. Normally, the lumbar spine should not curve convexly backward, but excessive flexion in the low back is not uncommon. Certain types of activities or exercises (e.g., knee-bent sit-ups) can cause flexion beyond the normal range and make the back vulnerable to strain from heavy lifting movements. (See pp. 174, 175.)

EXTENSION

Extension of the spine is movement of the head and trunk in a backward direction, while the spine moves in the direction of curving convexly forward.

In the cervical region, extension is movement in the direction of increasing the normal forward curve. It occurs by tilting the head back, bringing the occiput toward the seventh cervical vertebra. It may occur, in sitting or standing, by slumping into a round upper-back, and forward-head position that results in approximating the seventh cervical vertebra toward the occiput.

In the thoracic region, extension is movement of the spine in the direction of decreasing the normal backward curve by straightening the upper back. Movement may progress to, but normally not beyond, the straight (or flat) position.

In the lumbar region, extension is movement in the direction of increasing the normal forward curve. It occurs by bending the trunk backward or by tilting the pelvis forward. As indicated by the photographs on the facing page, the range of extension is highly variable, making it difficult to establish a standard for the purpose of measurements. Furthermore, these variations may exist without complaints of pain or disability, making it difficult to determine to what extent limited or excessive motion constitutes a disability. Too often, assessment of back extension is inaccurate or arbitrary.

From a supine position, normal flexion will allow enough curling of the trunk to lift the scapulae from the supporting surface. The area of the seventh cervical vertebra will be lifted upward approximately 8 to 10 inches.

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From a prone position, normal extension will allow the head and chest to be raised enough to lift the xiphoid process of the sternum approximately 2 to 4 inches from the table.

MOVEMENTS OF THE __VERTEBRAL COLUMN

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Hyperextension of the spine is movement beyond the normal range of motion in extension; it also may refer to a position greater than the normal anterior curve. Hyperextension may vary from slight to extreme. Excessive extension in the standing position is obtained by anterior pelvic tilt and is a position of lordosis. It is important to note that the range of back extension as seen in testing does not automatically translate into the same degree of lordosis in standing. Other factors, such as hip flexor length and abdominal muscle strength, also affect the position of the lumbar spine.

LATERAL FLEXION

Lateral flexion and rotation are described separately, although they occur in combination and are not considered to be pure movements.

Lateral flexion of the spine, which occurs in a coronal plane, is movement in which the head and trunk bend toward one side while the spine curves convexly toward the opposite side. A curve convex toward the right is the equivalent of lateral flexion toward the left. From a standing position with the feet approximately 4 inches apart, the body erect, and arms at the sides, normal lateral flexion (i.e., bending directly sideways) will allow the fingertips to reach approximately to the level of the knee.

Lateral flexion varies according to the region of the spine. It is most free in the cervical and lumbar regions and is restricted in the thoracic region by the rib cage.

ROTATION

Rotation is movement in a transverse plane. It is most free in the thoracic region and is slight in the lumbar region. Rotation in the cervical region permits an approximately 90° range of motion of the head and is referred to as rotation of the face toward the right or the left. Rotation of the thorax on the pelvis is described as clockwise (i.e., forward on the left side) or counterclockwise (i.e., forward on the right side).

Less-than-average back extension range of motion but normal muscle strength.

Average back extension range of motion, with anterosu-perior-iliac spines in contact with the table.

Excessive range of motion in back extension plus hip joint extension that raises the anterosuperior-iliac spines from the table. This subject is a diver and also has excessive flexion of the back. (See p. 175.)

TO MOVEMENTS OF THE

SPINE AND PELVIS

Backward bending in the standing position requires that the pelvis and thighs be displaced forward for balance. Spine extension must be distinguished from backward bending. How far the spine will bend backward depends on the available range of motion in the spine and the length of the abdominal muscles. How far the body will bend backward depends on the length of the hip flexors in addition to the above.

This subject is not trying to touch fingertips to the floor, which would require more hip joint flexion, but has fully flexed the spine. Flexion is normal, as denoted by the straight lumbar spine, and a smooth, continuous curve is in the thoracic region. (See pp. 175 and 377 for excessive flexion and p. 175, bottom right, for limited lumbar flexion.)

Lateral flexion of the spine depends on the available range of motion in the spine and the length of the opposite lateral trunk flexors. How far the body can bend sideways depends on the length of the opposite hip abductors in addition to the above. To ue side bending for measuring lateral flexion, the pelvis must be level and the feet a standardized distance apart

This subject has a high hip on the right. If this subject were to do side bending with a measurement taken of the distance from the fingertips to the floor, the measurement would be less on the right than on the left. If these measurements were then read as lateral flexion of the spine, it would be recorded— incorrectly—as lateral flexion more limited toward the right than toward the left. By virtue of the high hip on the right, the spine is already in lateral flexion, so the shoulder and arm will not move downward as far as would occur if the pelvis were level.

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Accurate measurements of spine extension and flexion as well as of lateral flexion should not include movements in the hip joints, which do occur in the bending movements illustrated above.

Various devices have been developed with the hope that meaningful objective measurements can be obtained. Goniometers, inclinometers, flexible rulers, tape measures, and radiographs have been used in an effort to establish a suitable method for measurement. Without first defining normal flexion of the lumbar spine, however, measurements may not be meaningful.

PELVIS

The neutral position of the pelvis is one in which the anterosuperior-iliac spines are in the same transverse plane, and in which the spines and the symphysis pubis are in the same vertical plane. An anterior pelvic tilt is a position of the pelvis in which the vertical plane through the antero-superior-iliac spines is anterior to a vertical plane through the symphysis pubis. A posterior pelvic tilt is a position of the pelvis in which the vertical plane through the antero-superior iliac spines is posterior to a vertical plane through the symphysis pubis. In a standing position, an anterior pelvic tilt is associated with hyperextension of the lumbar spine and flexion of the hip joints, whereas a posterior pelvic tilt is associated with flexion of the lumbar spine and extension of the hip joints. (See pp. 64-70.)

In lateral pelvic tilt, the pelvis is not level from side to side; rather, one anterosuperior spine is higher than the other. In standing, a lateral tilt is associated with lateral flexion of the lumbar spine and with adduction and abduction of the hip joints. For example, in a lateral tilt of the pelvis in which the right side is higher than the left, the lumbar spine is laterally flexed resulting in a curve that is convex toward the left. The right hip joint is in adduction and the left in abduction.

The pelvis is in a posterior tilt of 10°, and the lower back is flat (i.e., normal flexion).

BACK FLEXIBILITY AND HAMSTRING LENGTH

Equipment: Same as for hamstring length test, plus a ruler. The ruler is used to measure the distance of the fingertips either from or beyond the base of the big toe. This measurement is used only as a record to show the overall forward bending; it in no way indicates where limitation or excessive motion has taken place.

Starting Position: Sitting with legs extended (long-sitting) and feet at, or slightly below, right angles.

Reason: To standardize the position of the feet and knees.

Test Movement: Reach forward, with knees straight, and try to touch the fingertips to the base of the big toe or beyond, reaching as far as the range of muscle length permits.

Reason: Both the back and hamstrings will elongate to their maximum.

Normal length of back, hamstring, and gastroc-soleus muscles.

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