Back Extensors Testing And Grading

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Quadratus Lumborum Muscle Length Test

In the trunk extension test for the back extensors, the erector spinae muscles are assisted by the latissimus dorsi, quadratus lumborum, and trapezius.

In the prone position, the low back will assume a normal anterior curve.

To avoid false interpretations of the test results, it may be necessary to perform some preliminary tests. It is not necessary to do so routinely, however, because close observation of the subject in a prone position and of the movements taking place during trunk extension will indicate if preliminary tests for length of hip flexors (see p. 377) and strength of the hip extensors (see p. 436) are needed.

Patient: Prone, with hands clasped behind the buttocks (or behind the head).

Fixation: Hip extensors must give fixation of the pelvis to the thighs. The examiner stabilizes the legs firmly on the table.

Test Movement: Trunk extension to the subject's full range of motion.

Resistance: Gravity. Hands behind the head, or hands behind the lower back.

Grading: The ability to complete the movement and hold the position with hands behind the head or behind the back may be considered as normal strength. The low back muscles are seldom weak, but if there appears to be weakness, then hip flexor tightness and/or hip extensor weakness must be ruled out first. Actual weakness can usually be determined by having the examiner raise the subject's trunk in extension (to the subject's maximum range) and then asking the subject to hold the completed test position. Inability to hold this position will indicate weakness. Weakness is best described as slight, moderate, or marked based on the judgment of the examiner.

If the range of motion appears to be limited, a second person should hold the legs down (or legs should be held down with straps) while the examiner passively raises the subject's trunk in extension to that individual's completion of spine extension.

If the hip extensors are weak, it is possible that the examiner can stabilize the pelvis firmly in the direction of posterior tilt toward the thighs, provided that the legs are also firmly held down by another person or by straps. (See p. 182.) Alternatively, the subject may be placed at the end of the table, with the trunk in a prone position and legs hanging down with knees bent as needed. The examiner then stabilizes the pelvis and asks subject to raise the trunk in extension and hold it against pressure. In the presence of tight hip flexors, the back will assume a degree of extension (i.e., lordosis) commensurate with the amount of hip flexor tightness. In other words, the low back will be in extension before beginning the trunk extension movement. In such a case, the subject will be limited in the height to which the trunk can be raised, and the mistaken interpretation may be that the back muscles are weak,

A similar situation may arise if the hip extensor muscles are weak. For strong extension of the back, the hip extensors must stabilize the pelvis toward the thighs. If the hip extensors cannot provide this stabilization, the pelvis will be pulled upward by the back extensors into a position of back extension. Again, as in the case of hip flexor tightness, if the back is already in some extension before the trunk-raising movement is started, the trunk will not be raised as high off the table as it would be if the pelvis were fixed in extension on the thighs. (See pp. 180 and 182.)

Weakness: Bilateral weakness of the back extensor muscles results in a lumbar kyphosis and an increased thoracic kyphosis. Unilateral weakness results in a lateral curvature with convexity toward the weak side.

Contracture: Bilateral contracture of the low back muscles results in a lordosis. Unilateral contracture results in a scoliosis with convexity toward the opposite side.

STRONG BACK EXTENSORS, MISDIAGNOSED

WEAKNESS OF THE GLUTEUS MAXIMUS

Lordosis Lying Prone

Lying prone on a table, this subject exhibits a normal anterior curve in the lower back.

The moment that back extension is initiated, the curve in the lower back increases because of weakness in the gluteus maximus.

Back Extensor Strength Grades

When extension is continued, the subject can raise the trunk higher, but not to completion of the range of motion.

Posterior Pelvic Tilt Test

Holding the pelvis in the direction of posterior pelvic tilt, in the manner provided by a strong gluteus maximus, enables the subject to complete the full range of motion.

Back Extensors

Origin: Iliolumbar ligament, iliac crest. Occasionally from upper borders of the transverse processes of the lower three or four lumbar vertebrae.

Insertion: Inferior border of the last rib and transverse processes of the upper four lumbar vertebrae.

Action: Assists in extension, laterally flexes the lumbar vertebral column, and depresses the last rib. Bilaterally, when acting together with the diaphragm, fixes the last two ribs during respiration.

Patient: Prone.

Fixation: By muscles that hold the femur firmly in the acetabulum.

Test Movement: Lateral elevation of the pelvis. The extremity is placed in slight extension and in the degree of abduction that corresponds with the line of fibers of the quadratus lumborum.

Resistance: Given in the form of traction on the extremity, directly opposing the line of pull of the quadratus lumborum. If the hip muscles are weak, pressure may be given against the posterolateral iliac crest opposite the line of pull of the muscle.

The quadratus lumborum acts with other muscles in lateral trunk flexion. It is difficult to palpate this muscle because it lies deep beneath the erector spinae. Although the quadratus lumborum enters into the motion of elevation of the pelvis in the standing position or in walking, the standing position does not offer a satisfactory position for testing. Elevation of the right side of the pelvis in standing, for example, depends as much (if not more) on the downward pull by the abductors of the left hip joint as it does on the upward pull of the right lateral abdominals.

The test should not be considered as limited to action of the quadratus lumborum but as giving the most satisfactory differentiation that can be obtained.

Grading: Grading the strength of this muscle numerically is not recommended. Simply record whether it appears to be weak or strong.

STRONG LATERAL TRUNK MUSCLES AND STRONG ABDUCTOR MUSCLES

Quad Muscles Lateral Motion Range

Lateral trunk flexion through the subject's full range of Hip abduction through the subject's full range of motion. motion.

STRONG LATERAL TRUNK MUSCLES AND PARALYZED HIP ABDUCTOR MUSCLES

The subject can laterally flex the trunk, but the underneath shoulder will scarcely be raised from the table. The pelvis will be drawn upward as the head is raised laterally, and the iliac crest and costal margin will be approximated.

In attempting to raise the extremity in abduction, the movement that occurs is elevation of the pelvis by the lateral trunk muscles. The extremity may be drawn upward into the position as illustrated, but the hip joint is not abducted. In fact, the thigh has dropped into a position of adduction and is held there by the joint structure rather than by action of the hip muscles.

WEAK LATERAL TRUNK MUSCLES AND STRONG HIP ABDUCTOR MUSCLES

The subject cannot raise the trunk in true lateral flexion. Under certain circumstances, the patient may be able to raise the trunk from the table laterally even though the lateral trunk muscles are quite weak. If the trunk can be held rigid, the hip abductor muscles may raise the trunk in abduction on the thigh. The rib cage and iliac crest will not be approximated laterally as they are when the lateral trunk muscles are strong. By decreasing the pressure providing fixation for the hip abductors, the examiner can make it necessary for the lateral abdominals to attempt initiation of the movement.

The extremity can be lifted in hip abduction, but without fixation by the lateral abdominal muscles, it cannot be raised high off the table. Because of the weakness of the lateral trunk muscles, the weight of the extremity tilts the pelvis downward.

Quadratus Lumborum Muscle Length Test

Before testing the lateral trunk muscles, one should test the strength of the hip abductors, adductors, and lateral neck flexors and the range of motion in lateral flexion.

Raising the trunk sideways is a combination of lateral trunk flexion and hip abduction (the latter being produced by downward tilting of the pelvis on the thigh). The lateral trunk muscles entering into the movement are the lateral fibers of the external and internal obliques, the quadratus lumborum, the latissimus dorsi, the rectus abdominis and the erector spinae on the side being tested.

Patient: Side-lying, with a pillow between the thighs and legs and with the head, upper trunk, pelvis and lower extremities in a straight line. The top arm is extended down along the side, and the fingers are closed so that the patient will not hold onto the thigh and attempt to assist with the hand. The underarm is forward across the chest, with the hand holding the upper shoulder to rule out assistance by pushing up with the elbow.

Fixation: Hip abductors must fix the pelvis to the thigh. The opposite adductors also help to stabilize the pelvis. The legs must be held down by the examiner to counterbalance the weight of the trunk, but they must not be held so firmly as to prevent the upper leg from moving slightly downward to accommodate for the downward displacement of the pelvis on that side. If the pelvis is pushed upward or is not allowed to tilt downward, the subject will be unable to raise the trunk sideways even if the lateral abdominal muscles are strong.

Resistance: The body weight offers sufficient resistance.

Normal (10) Grade:* The ability to raise the trunk laterally from a side-lying position to a point of maximum lateral flexion.

Good (8) Grade: Same as above, except the underneath shoulder is approximately 4 inches up from table.

Fair (5) Grade: Same as above, except the underneath shoulder is approximately 2 inches up from table. (See p. 217 for tests and grades in cases of marked weakness of lateral trunk muscles.)

Note: Tests of the lateral trunk muscles may reveal an imbalance in the oblique muscles. In sideways trunk raising, if the legs and the pelvis are held steady (i.e., not permitted to twist forward or backward from the direct side-lying position), the thorax may be rotated forward or backward as the trunk is laterally flexed. A forward twist of the thorax denotes a stronger pull by the external oblique; a backward twist denotes a stronger pull by the internal oblique. If the back hyperextends as the patient raises the trunk, the quadratus lumborum and latissimus dorsi show a stronger pull, indicating that the anterior abdominal muscles cannot counterbalance this pull to keep the trunk in a straight line with the pelvis.

The test for strength of the lateral trunk flexors is important in cases of scoliosis.

Test Movement: Trunk raising directly sideways without rotation.

Raising the trunk obliquely forward combines trunk flexion and rotation. It is accomplished by action of the rectus abdominis and by the external oblique on one side combined with the internal oblique on the opposite side.

Patient: Supine. (For arm position, see the discussion of grades below.)

Fixation: An assistant stabilizes the legs as the examiner places the patient in the test position. (The examiner is not shown in this photograph.)

Test: The patient clasps hands behind the head. The examiner places the patient into the precise test position of trunk flexion and rotation and then asks die patient to hold that position. If the muscles are weak, the trunk will derotate and extend. There may be increased flexion of the pelvis on the thighs in an effort to hold the extended trunk up from the table.

Resistance: None in addition to the weight of the trunk. Resistance is varied by the position of the arms.

Normal (10) Grade:* Ability to hold the test position with hands clasped behind the head.

Good (8) Grade: Same as above, except with arms folded across the chest.

Fair+ (6) Grade: Same as above, except with arms extended forward. (See illustration of arm positions, p. 203.)

Fair (5) Grade: Ability to hold the trunk in enough flexion and rotation to raise both scapular regions from the table. (See p. 217 for tests and grades in cases of marked weakness of the oblique trunk muscles.)

Note: The test for muscle strength ofthe oblique abdominal muscles is important in cases of scoliosis.

*See numerical equivalents for word symbols used in and The Key to Muscle Grading on p. 23.

ANALYSIS OF MOVEMENTS AND MUSCLE ACTIONS DURING CURLED-TRUNK SIT-UPS

The illustrations on pages 188 and 189 show the various stages of movement of the spine and hip joints that occur during a curled-trunk sit-up. On pages 190-192, the illustrations are repeated with accompanying text that describes the associated muscle actions.

Outlines of the basic features have been made from photographs. Drawings of the femur and pelvis and a dotted line representing part of the vertebral column have been added. The solid line from the anterosuperior spine to the symphysis pubis is the line of reference for the pelvis. A dotted line parallel to the solid line has been drawn through the pelvis to the hip joint, and this line continues as a reference line through the femur to indicate the angle of the hip joint (i.e., the angle of flexion) at the various stages of movement.

Specific degrees, based on the average normal ranges of motion presented here and in Chapter 2, help to explain the movements that occur. Because of individual variations with respect to ranges of motion of the spine and hip joints, the manner in which subjects perform these movements will also vary.

For this particular analysis, the abdominal and erector spinae muscles, as well as the hip flexor and extensor muscles, are assumed to be normal in length and strength. The spine and hip joints are also assumed to permit normal range of motion.

Normal hip joint extension is given as 10°. From the viewpoint of stability in standing, it is desirable to have a few degrees of extension; however, it is not desirable to have more than a few degrees. In the upright or supine position with the hips and knees extended, a posterior pelvic tilt of 10° results in 10° of hip joint extension. This occurs because the pelvis is tilted posteriorly toward the back of the thigh instead of the thigh being moved posteriorly toward the pelvis. Flattening of the lumbar spine accompanies the posterior pelvic tilt. Flexion to the point of straightening or flattening the low back is considered to be normal flexion on the basis that it is an acceptable and desirable range of motion.

With the knee flexed, the hip joint can flex approximately 125° from the zero position to an acute angle of approximately 55° between the femur and the pelvis. With the knee extended (as in the straight-leg-raising test for hamstring length), the leg can be raised approximately 80° from the table. The equivalent of this is a trunk-raising movement, with the legs extended, in which the pelvis is flexed toward the thighs through a range of approximately 80° from the table.

For convenience in measuring joint motion, the trend is to use the anatomical position as zero. Thus, the straight position of the hip joint is considered to be the zero position. However, it is necessary to adhere to geometric terms when describing angles and the number of degrees in angles.

On pages 188 and 189, the right column under Hip Joints refers to the angle of flexion anteriorly between the reference line through the pelvis and the line through the femur, and degrees are expressed in geometric terms. Changes in the angle of flexion represent corresponding changes in the length of hip flexors. The left column under Hip Joints lists the number of degrees from the anatomical position through which the hip joint has moved, first in extension and then in flexion.

188 MOVEMENTS DURING CURLED-TRUNK SIT-UPS WITH LEGS EXTENDED

180" ^ Ant sup sptne

180" ^ Ant sup sptne

3BC

y

U—_i

SPINE

Cervical (Neck)

Thoracic (Upper Back)

Lumbar (Low Back)

PELVIS

HIP JONIS

Anatomical degrees

">meinc d'9rees

Position: Supine, hands clasped behind head

Zero (Normal anterior curve)

Position: Supine, hands clasped behind head

Zero (Normal anterior curve)

Zero

Zero

Neutral

Zero

(Normal

(Normal

position

posterior

anterior

curve)

curve)

Movement: Posterior pelvic tilt, lumbar spine flexion, and hip joint extens

on.

Zero

Zero

Flexed (straight)

10° posterior tilt

10° extension

190

C

Movement: Cervical and thoracic spine flexion. Figure C represents completion of spine flexion phase and beginning of hip flexion phase

Flexed (straight)

Flexed (curled)

Flexed (straight)

10* postenor tilt

10° extension

190*

Movement: Hip joint flexion. The hip joint has moved from a 190° angle of flexion to a 150° angle by pelvis flexing toward femur.

Flexed (straight)

Flexed (curled)

Flexed (straight)

Posterior tilt in relation to trunk

Anterior tilt toward thigh

Flexed 30°

150=

E

Movement: Hip joint flexion, and return toward zero position of cervical and thoracic spines.

Toward zero

Toward zero

Flexed (straight)

Posterior tilt in relation to trunk

Anterior tilt toward thigh

Flexed 80°

1OO*

SPINE

PELVIS

HIP JOINTS

Cervical (Neck)

Thoracic (Upper Back)

Lumbar (Low Back)

Anatomical degrees

Geometric degrees

A

Position: Supine, hands elapsed behind head, knees bent.

Zero (Normal anterior curve)

B

Zero (Normal posterior curve)

Zero (Normal anterior curve)

Neutral position

50°

130°

Movement. Lumbar spine flexion and 10° decrease in hip Joint flexion by virtue of posterior pelvic tilt

Zero C

Zero

Flexed (straight)

10° posterior tilt

50° flexion of thigh

140°

Movement. Cervical and thoracic spine flexion. Figure C represents completion of spine flexion and the beginning of the flexion of the pelvis toward flexed thigh.

Flexed (straight)

D

Flexed (curled)

Flexed (straight)

10° posterior tilt

50° flexion of thigh

140°

Movement: Hip joint flexion. The hip joint has moved from a 140° angle of flexion to a 100° angle by the pelvis flexing toward the femur.

Flexed (straight)

Flexed (curled)

Flexed (straight)

Posterior tilt in relation to trunk

Anterior tilt toward thigh

80° (50° thigh + 30° pelvis)

100°

Movement: Hip joint flexion, and a return toward zero position of the cervical and thoracic spines. On the basis of 125° being complete flexion, hip joint has reached the position of complete flexion.

Toward zero

Toward zero

Flexed (straight)

Posterior tilt in relation to trunk

Anterior tilt toward thigh

125* (50° thigh + 75° pelvis)

55°

ZERO POSITION OF THE SPINE, PELVIS, AND HIP JOINTS

ZERO POSITION OF THE SPINE AND PELVIS AND FLEXION OF THE HIP JOINTS

Figures A and A1 may be regarded as hypothetical starting positions. In reality, especially with the knees bent, the low back tends to flatten (i.e., the lumbar spine flexes) when a normally flexible individual assumes the supine position.

In Figure A, the length of the hip flexors corresponds with the zero position of the hip joints.

In Figure A1, because of the flexed position of the hips, the one-joint hip flexors are shorter in length than those in Figure A. In relation to its overall length, the iliacus is at approximately 40% of its range of motion, which is within the middle xk of the overall range.

POSTERIOR PELVIC TILT, LUMBAR SPINE FLEXION, AND HIP JOINT EXTENSION

POSTERIOR PELVIC TILT, LUMBAR SPINE FLEXION, AND HIP JOINT FLEXION

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