reliability and validity of four instruments for …...reliability and validity of four instruments...

Reliability and Validity of Four Instruments for Measuring Lumbar Spine and Pelvic Positions

RAY G. BURDETT, KATHRYN E. BROWN, and MICHAEL P. FALL

We studied the between-therapist reliability and the validity of four instruments in measuring lumbar spine curvature and pelvic tilt. The four instruments and their measurements were 1) a tape measure to measure the change in lumbar curvature during trunk flexion; 2) a gravity goniometer to measure pelvic angle and lumbar curvature during stance, trunk flexion, and trunk extension; 3) a parallelogram goniometer to measure lumbar curvature during stance, trunk flexion, and trunk extension; and 4) a standard goniometer to measure the angle between wooden pointers mounted perpendicularly to the spine to obtain pelvic angle and lumbar curvature during stance, trunk flexion, and trunk extension. We found no single instrument to be the most reliable or valid. Between-therapist reliability ranged from .64 to .93 (Pearson product-moment correlation) and from .60 to .92 (interclass correlation coefficient). The validities of the instruments compared with measurements from roentgenograms generally were low, ranging from -.13 to .76 (Pearson product-moment correlation) and -.73 to -.05 (interclass correlation coefficient).

Key Words: Lumbosacral region, Pelvis, Physical therapy.

Objective methods of externally measuring the motion and curvature of the lumbar spine or the pelvic tilt are important in assessing spine and pelvic functions. Many methods of measuring the curvature or range of motion of the spine and the pelvic tilt have been investigated. These methods can be classified as standard goniometry, tape measurement, and contour measurement.

Standard goniometry was shown by Fitzgerald et al to be reliable in measuring thoracolumbar extension and lateral flexion.1 With this method, however, restricting the measurement to the lumbar region is difficult. Pelvic tilt must be controlled closely or it will be included in the measurement. This method also is not useful in measuring pelvic tilt.

Hart et al2 and Reynolds3 used a modified goniometer called a spondylometer to measure total thoracolumbar flexion and extension. This method was reliable, and pelvic tilt did not affect the measurements because the sacrum surface was used as the reference for the measurement. This method, however, has many of the same limitations as standard goniometry: Lumbar motion is not measured separately from total spine motion, and neither pelvic tilt nor lumbar curvature during stance can be measured.

Gravity goniometers have been used to measure spinal flexion, extension, and lateral flexion.3-5 They measure the angle between the vertical plane and the tangent to the spine at the point of measurement. Regional motions can be measured by calculating the difference between angular motions at the two end points of the region. The gravity goniometer was shown by Reynolds to be reliable in measuring lumbar spine flexion, trunk extension, and lateral flexion.3

Several methods of using a tape measure to measure spine motion have been investigated. Macrae and Wright6 and Fitzgerald et al1 measured lumbar flexion using a skin distraction method based on that developed by Shöber,7 and they found a high reliability with this

method. Reynolds, however, found a low reliability when using the same method.3 Moll et al developed a skin distraction method of measuring lateral flexion8 and a method of measuring trunk extension using a plumb bob and a tape measure.9 They found these methods to produce reliable measurements. Reynolds found this method of extension measurement to have good reliability, but not the lateral flexion measurement.3

Frost et al measured total range of motion in trunk anterior flexion and lateral flexion as the distance from the fingers to the floor, and they measured trunk rotation and extension as the change in distance between bony landmarks.10 The measurements of anterior flexion and lateral flexion had good reliabilities, but the measurements of trunk rotation and extension did not. These methods cannot be used to measure regional spinal or pelvic motion and, because of differences in arm length and leg length among individuals, they may not be appropriate methods for making comparisons among subjects. The methods are reliable and easy to use, however, for showing changes in total motion for an individual over time. Gajdosik et al calculated the angle of pelvic tilt by measuring the distance from the floor to the anterior-superior

Dr. Burdett is Assistant Professor, Program in Physical Therapy, School of Health Related Professions, University of Pittsburgh, Pittsburgh, PA 15261 (USA).

Ms. Brown is Physical Therapy Supervisor, Department of Physical Therapy, Harmarville Rehabilitation Center, Pittsburgh, PA 15238.

Mr. Fall is a physical therapist with West Hartford Physical Therapy and Sports Medicine Associates, West Hartford, CT 06091. He was Staff Physical Therapist, Department of Physical Therapy, Harmarville Rehabilitation Center, when this study was conducted.

This article was submitted January 24,1985; was with the authors for revision 14 weeks; and was accepted October 3, 1985.

Volume 66 / Number 5, May 1986 677

Fig. 1. Modified gravity goniometer being used to measure the angle of the sacrum with respect to the horizontal plane.

Fig. 2. Parallelogram goniometer being used to measure the angle between the tangents to the spine at the sacrum and the thoracolumbar junction.

iliac spine (ASIS) and to the posterior-superior iliac spine (PSIS) and the distance between the ASIS and PSIS.11

They found this method to be reliable for measuring pelvic position and ROM.

Various devices for measuring the contour of the spine have been developed, including a simple, flexible rule that adapts to the contour of the back,4

a device for tracing the contour of the back,12 and an electronic device for recording the coordinates of points along the back.13 Other investigators have used pointers mounted perpendicularly to small bases that are taped to the back to indicate perpendicular planes to the spine.1415 Measurements of the angle

between the pointers are made from photographs. This method was compared to roentgenographic measurements and was reported to have a high validity for measurement of lumbar curvature during stance14 and trunk anterior flexion ROM.15

On the basis of this review of the literature, two basic techniques seem to have the potential of 1) isolating the position or motion of the lumbar spine or pelvis in the sagittal plane, 2) being valid and reliable, and 3) being clinically easy to use. One technique is the skin distraction method, which has been limited mainly to measurement of spine flexion. The other technique is the

measurement of the curvature of a region by measuring the angle between pointers mounted perpendicularly to the curve at two points.

The purpose of our study was to compare the reliability and validity of four instruments for measuring pelvic tilt during stance and lumbar curvature during stance, trunk flexion, and trunk extension. These four instruments were 1) a tape measure, 2) a gravity-operated goniometer modified for use on the back, 3) a parallelogram goniometer, and 4) a standard goniometer to measure the angle between wooden pointers mounted perpendicularly to the back.

METHOD

Subjects Twenty-seven volunteers participated

as subjects for determining the validities of these measurement instruments, and 23 of these volunteers also participated as subjects for determining the reliabilities of the instruments. Informed consent was obtained from each of the subjects. All subjects were between the ages of 20 and 40 years, had no history of chronic back pain or disability, and were not grossly overweight. A skin-fold measurement taken over one PSIS of each subject had a mean value of 1.42 cm (±0.73 cm).

Instrumentation A tape measure marked in centime

ters was used to measure the change in lumbar curvature between the positions of upright stance and trunk flexion. A modification of the method introduced by Shober7 was used. The skin was marked along the midline of the spine 10 cm above and 3 cm below the PSISs. The distance between these markers after trunk flexion was measured using the tape measure, and the change in distance between the marks was used to indicate the amount of lumbar flexion. This method cannot be used to measure pelvic tilt because the reference point for the measurement is on the pelvis. It also cannot be used to measure lumbar curvature for a particular position, but it can be used to measure the change in curvature between two positions. Therefore, we used a tape measure to measure only the change in lumbar curvature between the positions of upright relaxed stance and trunk flexion.

678 PHYSICAL THERAPY

RESEARCH

Figure 1 shows the gravity goniometer* that was modified for use on the back by attaching a 2-cm x 3.5-cm rectangular platform on the base of the goniometer. This platform was placed on the back to form a tangent to the back at a particular point. The angle of the tangent with respect to the vertical plane then was read from the goniometer. Angles were measured at the thoracolumbar (T-L) junction and on the sacrum. Pelvic tilt was defined as the angle between the horizontal plane and the perpendicular to the sacrum. This goniometer can be used to measure pelvic tilt and lumbar curvature during any trunk position because the vertical gravity line is the reference for the measurement. This measure of pelvic tilt, however, will not account for movement between the pelvis and the sacrum. In our study, this instrument was used to measure lumbar curvature and pelvic tilt during stance and lumbar curvature during trunk flexion and extension.

The parallelogram goniometer† that we used is shown in Figure 2. It was constructed so that the linkage between its two platforms resulted in a direct reading of the angular difference between the surfaces of the two platforms. The angular difference between the curvature at the T-L junction and sacrum was measured with this goniometer. It cannot be used to measure pelvic tilt because the pelvis is the reference for the measurement.

Figure 3 shows the two 1.5-cm × 2.5-cm rectangular plastic platforms with 10-cm wooden pointers that we used. These platforms were attached with tape so that one was centered over the T-L junction and one was centered between the PSISs and the skin mark 3 cm below the PSISs. The angle between the pointers was measured in two ways using a standard plastic goniometer. First, the angle was measured directly by aligning the pointers with the lines on the goniometer arms running perpendicularly to the axes of the goniometer arms. Pelvic tilt could not be measured directly this way because the pelvis was the reference for this measurement. Therefore, only lumbar curvature during relaxed upright stance, trunk flexion, and trunk extension were measured with this method.

Fig. 3. Standard goniometer being used to measure the angle between wooden pointers mounted perpendicularly to the spine at the sacrum and thoracolumbar junction.

Fig. 4. Internal and external angles of pelvic tilt and lumbar curvature. IL = internal lumbar angle, EL = external lumbar angle, IP = internal pelvic angle, and EP = external pelvic angle.

Then, a photograph of the pointers on the body was made from the side, and the angle between the pointers was measured from the photograph by aligning the long axes of the goniometer with the pointers. A vertical reference line placed in the field of view of the camera was used as the reference for measuring pelvic tilt. The camera was placed on a horizontal surface and was positioned visually by the therapist so that its film plane was parallel to the sagittal plane of the subject. Pelvic tilt was determined as the angle between the horizontal plane and a pointer mounted perpendicularly to the sacrum. Therefore, any motion that occurred between the pelvis and the sacrum was included in this measurement. The photographs were used to measure pelvic tilt during stance and lumbar curvature during stance, trunk flexion, and trunk extension.

Reliability Determination

Two physical therapists who were unfamiliar with these measurement methods practiced until they became comfortable using these instruments. Each therapist completed the following procedures for each subject. With the subject in the prone position, the low back area was exposed. The PSISs were palpated and marked. A line was drawn between them, and marks were placed along the midline of the spine 10 cm above and 3 cm below this line. The T-L junction also was palpated and marked. The subject then stood in a normal, relaxed posture with the heels about shoulder width apart. The angles of the sacrum and the T-L junction with respect to the vertical plane were measured with the gravity goniometer. The parallelogram goniometer was used to measure the lumbar curvature between the T-L junction and the sacrum. The platforms with pointers were taped to the subject's back at the T-L junction and over the sacrum. The standard goniometer was used to measure the angle between the pointers, and a photograph of the pointers was taken from the side.

The subject then sat on an adjustable-height seat and was positioned with his thighs parallel to the floor, knees in 90 degrees of flexion, and ankles in a neutral position. The subject flexed his trunk and hips from this position until his shoulders contacted his thighs or to his maximum amount of flexion. The subject then was instructed to place his forearms under his thighs and grasp his opposite elbows with his hands to be stabilized in this position. This was done to achieve a fixed position that could be reassumed for subsequent measurements. The angle between the pointers was measured with the standard goniometer, a photograph of the pointers was taken, and the platforms then were removed. The tape measure was used to measure the distance between the 10-cm and 3-cm marks, the gravity goniometer was used to measure the angles at the T-L junction and the sacrum, and the parallelogram goniometer was used to measure the angle between the T-L junction and sacrum.

The subject then was placed in the prone position on a table with a hinged top so that his ASISs were directly above the hinge. His thighs were strapped to the tabletop for stabilization, and the portion of the table under his upper

* Bowen and Co, Inc, Rockville, MD 20852. † Designed and constructed by Gary Debaucher,

Emory University Rehabilitation Center, Atlanta, GA 30322.


body was raised to cause hyperexten-sion. The position of the table was marked for each subject so that the same position could be achieved for subsequent measurements. No attempt was made to keep the table position constant

among subjects or to take each subject to the end of his range. The angles of the T-L junction and sacrum were measured using the gravity goniometer, and the angle between the T-L junction and sacrum was measured using the paral-

TABLE 1 Pearson Product-Moment Correlation Coefficients and Interclass Correlation Coefficients for Between-Therapist Reliabilitiesa

Measurement

Lumbar curvature during trunk flexion

Lumbar curvature during trunk extension

Lumbar curvature during stance

Pelvic tilt during stance

Gravity Goni

ometer

r

.93

.72

.93

.84

ICC

.91

.71

.92

.82

Parallelogram Goni

ometer

r ICC

.93 .92

.64 .60

.90 .89

NM

Instrument

Platforms

Goniometer

r

.85

.77

.88

ICC

.85

.75

.88

NM

Photos

r

.87

.81

.88

.89

ICC

.87

.78

.88

.87

Tape Measure

r ICC

.71 .72

NMb

NM

NM

TABLE 2 Means and Standard Deviations of the Measurements Made by Each Therapist with Each Instrument

Measurement and Instrument

Lumbar curvature during trunk flexiona

Gravity goniometer5

Parallelogram goniometer Goniometric measurement of plat

forms Photographs of platforms Tape measure (cm)

Lumbar curvature during trunk extensiona

Gravity goniometer Parallelogram goniometer Goniometric measurement of plat

forms Photographs of platformsb

Lumbar curvature during stancea

Gravity goniometer Parallelogram goniometer Goniometric measurement of plat

forms Photographs of platforms

Pelvic tilt during stancea

Gravity goniometer Goniometric measurement of plat

forms6

Therapist 1

10.4 11.0

11.0 11.6 20.1

26.4 26.3

26.3 27.2

13.9 12.4

14.6 16.5

14.6

21.7

s

6.1 6.4

6.5 6.7 1.2

6.3 6.3

13.8 13.2

8.1 6.7

10.7 10.5

6.3

8.0

Therapist 2

11.3 11.0

11.8 12.1 20.1

25.6 24.4

24.2 23.7

14.5 12.9

14.3 16.3

13.7

20.2

s

5.3 5.4

6.1 6.9 1.1

9.2 8.0

10.8 12.2

9.4 7.8

9.5 9.8

7.8

7.5

lelogram goniometer. The platforms with the pointers then were placed on the T-L junction and sacrum, the angle between the pointers was measured with the standard goniometer, and a photograph was made of the pointers. The first therapist completed this procedure and erased all of the skin markings. Then, the second therapist immediately performed the same procedure on the same subject.

Validity Determination One of the therapists who assisted in

the reliability determination also participated in determining the validity of these instruments. Each subject was marked as previously described. The subject then was positioned in preparation for a sagittal plane roentgenogram of the low back in one of the three measurement positions: upright relaxed stance, trunk flexion, or trunk extension. Using all the instruments, the therapist measured the lumbar curve and sacral angle of the subject in this position. Then, while the subject was still in this position, a roentgenogram was taken of the low back region, Ten subjects were measured in upright relaxed stance, 6 in trunk flexion, and 11 in trunk extension. Only one position was measured for each subject to limit the exposure of each subject to radiation.

A line was drawn on the roentgenogram along the inferior surface of the 12th thoracic vertebral body (T12) and along the superior surface of the 1st sacral vertebral body (S1) (Fig. 4). The angle of pelvic tilt was defined as the angle between the horizontal plane and the line along the superior surface of S1. The base of the roentgenogram was used as the horizontal reference because the film was positioned so that its base was horizontal during the roentgenogram procedure. The lumbar curvature was defined as the angle between the lines along the inferior surface of T12 and the superior surface of S1. These two angles taken from the roentgenogram were used as the reference angles for determining the validity of the external measurements.

The validity of the tape measure method of measuring change in lumbar flexion was not determined. Two roentgenograms of subjects—one in normal, relaxed stance and one in trunk flexion—would be needed to calculate the change in lumbar curvature internally

a All correlation coefficients are significantly different from zero at the p < .05 level. b NM = not measured.

a Except where indicated, all measurements are in degrees. b Significantly different at p < .05.


RESEARCH

to determine the validity of this method. We took only one roentgenogram for each subject, however, to minimize exposure to radiation.

Data Analysis

To determine the between-therapist reliabilities of the external measurements, Pearson product-moment correlation coefficients (r) and interclass correlation coefficients (ICCs) were calculated between the measurements made by the therapists. Because Pearson product-moment correlation shows only the parallelism of the two sets of measurements, an analysis of variance (AN-OVA) was performed to compare the means of the sets' measurements. Validity of the external measurements also was determined by calculating Pearson product-moment correlation coefficients and ICCs and by performing an ANOVA between external measurements and measurements from the roentgenograms. A probability level of .05 was selected for significance. A correlation coefficient of .80 or above was chosen as an indication of high between-therapist reliability and high validity.

RESULTS

The correlation coefficients for between-therapist reliabilities for each of the instruments and measurements are shown in Table 1. These coefficients ranged from a low of .60 (ICC) and .64 (r) for measuring lumbar curvature during trunk extension with the parallelogram goniometer to a high of .92 (ICC) and .93 (r) for measuring lumbar curvature during trunk flexion using the parallelogram goniometer and for measuring lumbar curvature during stance using the gravity goniometer. Each of the measurements had a reliability correlation coefficient significantly different from zero, but not all measurements reached the value of .80 that was chosen as a clinically significant coefficient.

The least reliable of the measurements was lumbar curvature during trunk extension. Only the method using photographs of the pointers approached a .80 correlation coefficient. The tape measure method of measuring change in lumbar curvature between upright stance and trunk flexion also was unreliable using this criterion. We saw no clear trend for the gravity goniometer, the parallelogram goniometer, or the platforms and standard goniometer to

TABLE 3 Results of Two-Way Analysis of Variance for the Measurement of Lumbar Curvature During Trunk Flexion

Instrument and Source Gravity goniometer

Therapists Subjects Therapist x subject

Parallelogram goniometer Therapists Subjects Therapist x subject

Platforms—goniometric measurement


Platforms—measurement from photographs


Tape measure Therapists Subjects Therapist x subject

df

1 22 22

1 22 22

1 22 22

1 22 22

1 22 22

SS

7.3 1375.4

60.7

0.0 1462.9

63.0

7.0 1636.0 132.0

3.1 1903.2 134.9

0.0 53.5 9.1

MS

7.8 62.5 2.8

0.0 66.5 2.9

7.0 74.4

6.0

3.1 86.5

6.1

0.0 2.4 0.4

F

2.85a

0.00

1.17

0.51

0.01

TABLE 4 Results of Two-Way Analysis of Variance for the Measurement of Lumbar Curvature During Trunk Extension








df

1 22 22

1 22 22

1 22 22

1 22 22

SS

7.8 2667.5 459.6

40.2 1851.2 437.3

52.2 5889.9

884.3

135.7 6441.9 679.8

MS

7.8 121.2 20.9

40.2 84.2 19.9

52.2 267.7

38.4

135.7 292.8 30.9

F

0.38

2.02

1.36

4.39a

exhibit a higher overall reliability. Each of these instruments was highly reliable for measuring lumbar curvature during trunk flexion and upright relaxed stance. In addition, the gravity goniometer and photographs of the platforms also were reliable for measuring pelvic tilt during stance.

Table 2 shows the means and standard deviations of the measurements

made by the two therapists. Tables 3 through 6 show the results of two-way ANOVAs comparing the means of these measurements. Small, but significant, differences existed between the following measurements made by the two therapists: lumbar curvature during trunk flexion using the gravity goniometer, and pelvic tilt during stance and lumbar curvature during trunk extension using

a Significant at p < . 05.

a Significant at p < .05.


TABLE 5 Results of Two-Way Analysis of Variance for the Measurement of Lumbar Curvature During Relaxed, Upright Stance








df

1 22 22

1 22 22

1 22 22

1 22 22

SS

4.3 3263.6

142.7

2.6 2190.2

131.9

1.4 4238.3 277.6

0.5 4260.7

284.0

MS

4.3 148.3

6.5

2.6 99,6

6.0

1.4 192.7 12.6

0.5 193.7 12.9

F

0.66

0.44

0.11

0.04

TABLE 6 Results of Two-Way Analysis of Variance for the Measurement of Pelvic Tilt During Relaxed, Upright Stance





df

1 22 22

1 22 22

SS

10.5 2036.2

198.5

25.1 2506.6 284.0

MS

10.5 92.5 9.0

25.1 113.9 12.9

F

1.17

3.59a

TABLE 7 Pearson Product-Moment Correlation Coefficients and Interclass Correlation Coefficients for Validities of External Measurements

Measurement





Gravity Goniometer

r

.73

.15

-.12

.10

ICC

-.11

-.73

-.62

-.45

Instrument

Parallelogram Goniometer

r

.46

.24

.03

ICC

-.19

-.71

-.59

NMb

Platforms

Goniometer

r

.70

.51

-.13

ICC

-.09

-.63

-.55

NM

Photos

r

.76a

.60

-.09

.08

ICC

-.05

-.62

-.49

-.20

the photographs of the platforms and pointers.

The correlation coefficients representing the validities of the instruments and the measurements made by each instrument are shown in Table 7. The only correlation that was significantly different from zero was for the measurement of lumbar curvature during trunk flexion using the photographs of the platform pointers. This correlation coefficient also approached the value of .80 chosen for clinical significance.

Table 8 shows the means and standard deviations of the external measurements made with each instrument for each position and the internal measurements made from the roentgenograms. Results of the two-way ANOVA comparing the means of these external and internal measurements are shown in Table 9. The measurements made externally by the therapist with the gravity goniometer, parallelogram goniometer, and the regular goniometer directly or from photographs did not differ significantly for any of the measurement positions. The measurements made internally from the roentgenograms, however, differed significantly from all those made externally for all measurement positions.

DISCUSSION

The reliabilities of the methods of measurement found in our study are similar to those found in other studies of the measurement of trunk motion. Both our study and that of Reynolds3

found the gravity goniometer to be reliable in measuring the curvature or position of the spine. The reliabilities of the methods of measuring pelvic tilt in our study are similar to those found by Gajdosik et al11 in their study of pelvic angle measurement. Their method requires three measurements and a calculation; our method gives the angle of tilt directly. Their method, however, uses points of reference directly on the pelvis, and our method uses the sacrum as the reference surface, which may result in invalid measurements because any motion between the sacrum and the pelvis would be included. We found the measurement of lumbar flexion using the tape measure to be unreliable using a criterion of 80 as a highly reliable correlation coefficient. This finding is similar to the findings of Reynolds3 for this method. Other investigators, how-


a Significantly different from zero at the p < .05 level. b NM = not measured.


RESEARCH

ever, have found this method of measuring the change in lumbar curvature during trunk flexion to be highly reliable.1,6 Our finding of a relatively low reliability in this measurement may be because of the homogeneity of our subjects. The standard deviation was very small when this instrument was used to measure lumbar flexion compared with the standard deviations of the measurements obtained using the other instruments (Tab. 2). This difference would make a high correlation coefficient more difficult to obtain.

We did not find one of the methods studied to emerge as the most reliable when comparing the measurements each could make in common, but we did find that each method has its advantages and disadvantages. A common advantage of these methods compared with many other methods, such as standard goniometry or reaching, is their ability to measure regional motion or position rather than combined motions.

Measuring lumbar flexion using a tape measure is a simple method. A tape measure, however, cannot be used for measuring standing posture because standing is the reference position. Also, using a standard starting distance could result in different numbers of spinal segments contributing to the motion for different individuals. Using a standard distance, however, may produce more reliable results than using the T-L junction as a reference position because therapists may differ in their palpation skills. The other instruments are at least as reliable as the tape measure and can measure other motions or positions as well.

The gravity goniometer and the photographs taken of the platform pointers are the most versatile of the methods we studied because they can measure both pelvic and lumbar spine positions. Reliabilities of measurements made by the gravity goniometer depend on the even application of pressure so that the base of the goniometer is tangent to the spine. Uneven pressure, especially on a patient with a large skin fold over the area of measurement, could tilt the base of the goniometer with respect to the spine. An increase in the length of the base may minimize this problem.

The parallelogram goniometer cannot measure pelvic angle because a horizontal reference is needed, but it can measure the lumbar curvature for any body

TABLE 8 Means and Standard Deviations of the Measurements Made Externally by One Therapist and Made Internally from Roentgenograms (in Degrees)

Measurement





Roentgenogram

-4 .1 a

65.6a

48.8a

29.8a

s

15.1

11.6

17.7

12.2

Gravity Goni

ometer

16.0

34.5

16.9

10.2

s

6.5

4.9

5.7

6.3

Instrument

Parallelogram Goni

ometer

15.0

33.1

16.2

s

6.3

5.9

5.8

NMb

Platforms

Goniometer

16.0

32.2

19.8

s

7.2

7.2

9.3

NM

Photos

15.5

32.4

21.3

15.1

s

7.1

6.9

11.3

11.2

TABLE 9 Results of Two-Way Analysis of Variance Comparing the Measurements Made Externallv and Internally Durina the Validity Determination

Measurement and Source Lumbar curvature during trunk

flexion Instrument Subjects Instrument x subject


Instrument Subjects Instrument x subject


Instrument Subjects Instrument x subject

Pelvic tilt during stance Instrument Subjects Instrument x subject

df

4 5

20

4 10 40

4 9

36

2 9

18

SS

1888.3 1460.3 590.1

9395.3 1694.0 1230.3

7494.2 2040.0 3297.8

2080.9 1277.0 1549.1

MS

471.1 292.1

29.5

2348.8 169.4 30.8

1873.6 226.7

91.6

1040.5 141.9 86.1

F

16.0a

9.9

76.4a

5.5

20.5a

2.5

12.1a

1.7

position. Its reliability, similar to that of the gravity goniometer, is dependent on the even application of pressure to its bases. The parallelogram goniometer could be converted to an electrogoniom-eter by the addition of a potentiometer. As such, it could be used to measure continuously lumbar spine position or motion during an activity and also as a biofeedback device. The parallelogram goniometer used in our study can be constructed from readily available parts and tools.

The platforms and pointers can be applied easily to the back using double-sided tape. The main problem with the reliability of this method is skin motion, especially during trunk extension. Patients with large skin folds under the platforms may cause the platform to tilt relative to the underlying spine during motions that tend to compress the skin. This method, however; is very versatile, especially when combined with photography. This method has been used with high-speed photography and videotap-

a Significantly different from the other means at p < .05 level. b NM = not measured.



ing to measure spine and pelvic motion during activities.15,16

The validities of the lumbar curvature and pelvic tilt angles were very low, partly because of the high variability among the subjects between the tangent to the posterior surface of the sacrum and the angle of the surface of the S1. This high variability among the subjects resulted in a low validity for both the pelvic tilt measurements and the lumbar curvature measurements because the pelvic angle was used as a reference to measure this curvature. Use of another reference for pelvic angle from the roentgenograms, such as a line between the ASIS and PSIS, may increase the validity of these external measurements.

CONCLUSIONS

This study has compared the reliabilities and validities of four clinical methods for measuring lumbar curvature and pelvic angle. Each of the methods has advantages and disadvantages that can affect the reliability and validity of the measurements or the ease of use of the instruments. No one instrument was found to be superior to the others. Lum

bar curvature during stance or trunk flexion and pelvic tilt during stance were measured more reliably than was lumbar curvature during trunk extension. Using the superior surface of S1 and the inferior surface of T12 as the references for the validity of the external measurements, we found that none of the instruments were able to measure any of the positions with a high validity. Some refinement of the instruments and procedures used in this study may increase their reliabilities. Other methods may exist that are more reliable and valid for measuring regional spinal curvature or pelvic angle, and studies of these methods are needed.

REFERENCES

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4. Anderson JAD, Sweetman BJ: A combined flexi-rule/hydrogoniometer for measurement of lumbar spine and its sagittal movement. Rheumatol Rehabil 14:173-179,1975

5. Loebl WY: Measurement of spinal posture and range of spinal movement. Annals of Physical Medicine 9:103-110,1967

6. Macrae IF, Wright V: Measurement of back movement. Ann Rheum Dis 28:584-587,1969

7. Shöber P: The lumbar vertebral column and backache. Meunchener Medizinische Woch-enschrift 84:336,1937

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reliability and validity of four instruments for …...reliability and validity of four instruments...

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