This study was completed in partial fulfillment of the requirements of his master's degree, Department of Physical. Therapy, School of Allied Health Professions, ...
Reliability of the Attraction Method for Measuring Lumbar Spine Backward Bending PAUL BEATTIE, JULES M. ROTHSTEIN, and ROBERT L. LAMB The distraction method is one method used to measure forward bending of the spine. Although this technique, which requires the use of a tape measure held over the spine and the location of anatomical landmarks, appears to be highly practical, previous studies have not examined its use for measuring backward bending. The purpose of our study was to determine the reliability of a similar technique, the attraction method, for measuring backward bending of the lumbar spine and to examine whether subjects with low back pain (LBP) could perform similar motion as subjects without LBP. Two groups composed of 100 subjects each, one with "significant" limiting low back pain (SLBP) and the other without "significant" limiting low back pain (NSLBP), were evaluated twice by a physical therapist to assess intrarater reliability. To assess interrater reliability, 11 subjects from the NSLBP Group were evaluated by a second therapist. For the total sample of 200 subjects, the intraclass correlation coefficient (ICC) for intrarater reliability was .95; for the SLBP Group, the ICC was .93; and for the NSLBP Group, the ICC was .90. For the sample of 11 NSLBP Group subjects examined for interrater reliability, the ICC was .94. Using a Kolmogorov-Smirnov test, we found the distribution for backward bending of the two groups to be significantly different. The attraction method, thus, appears to be a reliable method for measuring backward bending of the lumbar spine. Key Words: Backache, Lumbosacral region, Physical therapy.
Evaluation of patients with low back pain (LBP) frequently includes measurement of trunk range of motion. Although studies have shown extremity ROM measurements to have some validity and reliability,1,2 measurement of trunk motion has proven to be more difficult. Many clinical techniques have been described for measuring trunk motion. These include the use of radiographs,3-7 inclinometers,3,8-10 spondylometers,10-12
Mr. Beattie is Instructor, Division of Physical Therapy, Department of Orthopedics, College of Medicine, University of New Mexico, Albuquerque, NM 87131 (USA). At the time of this study, he was Staff Physical Therapist, Medical College of Virginia Hospital, Richmond, VA. This study was completed in partial fulfillment of the requirements of his master's degree, Department of Physical Therapy, School of Allied Health Professions, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA. Dr. Rothstein is Assistant Professor, Department of Physical Therapy, School of Allied Health Professions, Medical College of Virginia. Dr. Lamb is Associate Professor and Director of Graduate Studies, Department of Physical Therapy, School of Allied Health Professions, Medical College of Virginia. This article was submitted September 27, 1985; was with the authors for revision 19 weeks; and was accepted July 1, 1986. Potential Conflict of Interest: 4.
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fingertip-to-floor methods,13 goniometers,14 plumb lines,3,5,10,15 and tape measures.3,6,10,14-18 Each of these techniques has disadvantages, such as cost, exposure to radiation, need for specialized equipment, and questionable reliability (Tab. I).19,20 Probably because a multitude of techniques exists for measuring back motion, no one method has been developed fully (ie, its reliability and validity demonstrated) for clinical use. No studies, therefore, have demonstrated the reliability of measuring spinal motion in patients with LBP. Most reliability studies of trunk motion have examined healthy subjects,1,3,5,6,8,10,14-16 rather than focusing on the subjects whom therapists examine most often (ie, those with LBP). Several authors have reported that patients with LBP have reduced motion.17,21-23 No studies, however, actually document the limitations in motion. Such limitation has been impossible to document because heretofore a reliable means of measuring backward bending has not been developed. One potentially useful method for measuring spinal motion in patients with LBP involves the use of a tape measure placed directly over the lumbar
spine while the patient bends forward or backward. This method has been described only for the measurement of forward bending (flexion).3,6,10,14-18 Macrae and Wright6 investigated and modified Schober's18 method, which used a tape measure placed over the lumbar spine to measure forward bending. Macrae and Wright's method involved using a tape measure held directly over the spine between points 10 cm above and 5 cm below the lumbosacral junction in the standing subject (Figure). The subject then was asked to bend forward, and the new, increased distance between the points was measured. The difference between this new distance and the starting distance of 15 cm was considered to be the amount of forward bending. Macrae and Wright attempted to validate this method by superimposing two sets of radiographs to correlate the measurements obtained from 11 subjects with and without spinal disease. One radiograph was taken while the subject was standing erect, and the second radiograph was taken with the subject in a position of forward bending. Based on a product-moment correlation coefficient of .97, Macrae and Wright conPHYSICAL THERAPY
RESEARCH TABLE 1 Advantages and Disadvantages of Commonly Used Clinical Tools to Measure Lumbar Spine Motion Instrument
Advantages
Superimposition of radiographs3-7
direct measure
Inclinometer38-10
easy to use, fairly good reliability
Spondylometer10-12
easy to use, fairly good reliability inexpensive, accessible
Plumb line method3,5,10,15
Goniometry14 Tape measure over spine3,6,10,14-18
Fingertips to floor13
inexpensive, accessible, easy to use inexpensive, accessible
inexpensive, accessible
Figure. Illustration of the marks used to obtain measurements with the attraction method. The 0-cm mark represents the spinal intersection of a horizontal line drawn between the left and right posterior superior iliac spines. From this point, a second mark is placed 10 cm superior and a third mark 5 cm inferior. The most caudal and cephalad lines, therefore, are 15 cm apart (ie, the starting position). With backward bending, these marks approximate (ie, move toward one another). The difference between the starting distance (15 cm) and the distance between the attracted marks provides an indication of backward bending. (Adapted from Macrae and Wright.6) Volume 67 / Number 3, March 1987
Disadvantages cost, exposure to radiation, equipment not always accessible equipment not always accessible, requires patient to maintain positions for prolonged periods of time equipment not always accessible questionable reliability, not suitable for extremely flexible subjects, difficult to perform questionable reliability and validity questionable reliability, requires precise identification of bony landmarks, no single set of instructions available unreliable, provides only an index of total forward bending
cluded that their method accurately measured forward motion of the lumbar spine. Moll and Wright20 suggested that the modified Schober method also might be useful for assessing backward bending by measuring the attraction of the skin marks as they approach one another during backward bending. This attraction method has the obvious advantages of being safe, inexpensive, and easy to perform, and it requires no special equipment. If the attraction method could be shown to be reliable, it could become a useful clinical measurement tool for evaluating patients with LBP. The purpose of our study was to determine the intrarater and interrater reliabilities of the attraction method for measuring backward bending of the lumbar spine and to determine whether the distribution of backward bending measurements obtained with the attraction method was different in subjects with "significant" limiting low back pain (SLBP) as compared with subjects without "significant" limiting low back pain (NSLBP).
METHOD Subjects The subjects in this study consisted of two groups of volunteers who were pa-
tients, students, or staff members at the Medical College of Virginia, Richmond, Va, at the time of the testing. The NSLBP Group subjects (n = 100) did not have any LBP during the two-month period before the study that required them to limit work, school, or recreational activities. Low back pain was defined as pain on the posterior surface of the trunk below the basilar costal margins or above the greater trochanter. The two-month period was chosen because many people with LBP have been known to improve within that period of time, whereas those in whom pain persists past that period frequently will seek medical assistance.24 The SLBP Group subjects (n = 100) had episodes of LBP that caused them to limit work, school, or recreational activities within the twomonth period before testing; that is, these subjects would be considered candidates for physical therapy. The term "limit" is used to indicate that subjects would have had to modify these activities (eg, change their role at work, engage in recreational activities different from those they previously had pursued). None of the subjects in either group had a history of neurological or connective tissue disease, spinal fusion, or scoliosis with a lateral spinal curvature greater than 40 degrees (as determined by the examiner's [P.B.] observation). None of the female subjects thought that they were pregnant at the time they were measured. All subjects completed a questionnaire and a consent form before admission to the study. The SLBP Group consisted of 50 men and 50 women, aged 16 to 65 years, with a mean age of 37.6 ± 11.6 years (Tab. 2). The NSLBP Group consisted of 37 men and 63 women, aged 20 to 76 years, with a mean age of 32.4 ± 12.3 years (Tab. 2).
Procedure Intrarater reliability. After the subjects completed the questionnaire and consent form, they entered an examination room where they removed their shoes and disrobed to expose their back from the gluteal fold to the midthoracic spine. The examiner then knelt behind the standing subject and identified the inferior margins of the subject's posterior superior iliac spines (PSISs) with his thumbs. At the point where the midline of the lumbar spine intersected an imaginary line drawn between the two PSISs, a small ink mark was drawn horizontally. From this initial ink mark, two more marks were drawn horizon365
tally, the first 10 cm above and the second 5 cm below the original mark (Figure). The examiner then used the dorsum of his hand to hold the tape measure against the subject's back. The examiner then asked the subjects to bend backwards as far as possible without bending their knees. When the subjects reached the end of the movement, the examiner measured the new distance between the upper and lower ink marks and subtracted that measurement from the starting distance of 15 cm (eg, 15 cm - 12.5 cm = 2.5 cm of backward bending). After each measurement was made, the examiner erased the ink marks with alcohol. The examiner then immediately took a second measurement with the attraction method to determine intrarater reliability. To help prevent the examiner from being biased by the first measurement, the tape measure was turned over so that only the blank side was visible to the examiner when he took the measurement. The examiner marked the tape with his thumb at the point of intersection of the tape and the lower ink mark. The distance then was determined by holding the tape next to a ruler. Interrater reliability. To determine the interrater reliability of the attraction method, a second examiner measured 11 members of the NSLBP Group. After the subjects were measured twice by the first examiner, they remained in the examination room where in turn they were measured by a second examiner who also used the attraction method. To assess his intrarater reliability, the second therapist also measured the subjects two consecutive times with the attraction method.
TABLE 2 Characteristics of the Sample Studied Variable Men Women Mean age (yr) Age range (yr) Mean height (in)c Height range (in) Mean weight (lb)d Weight range (lb) Subjects with previous lumbar surgery Subjects with leg pain at the time of the study
SLBPa Group (n = 100)
NSLBPb Group (n = 100)
50 50 37.61 ±11.64 16-65 67.70 ± 4.27 53-77 171.84 ± 37.2 105-280
37 63 32.44 ± 12.33 20-76 66.74 ± 4.07 59-76 147.80 ±32.71 92-250
12
2
29
0
a
SLBP = with "significant" limiting low back pain. NSLBP = without "significant" limiting low back pain. c 1 in = 2.54 cm. d 1 lb = 0.454 kg. b
TABLE 3 Frequency Distributions for Backward Bending of Subjects SLBPa Group
NSLBPb Group
Upper Limit for Cell (cm)
Frequency
Cumulative Frequencyc
Frequency
Cumulative Frequencyc
Difference in Cumulative Frequenciesd
0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 >4.00
18 39 15 18 3 2 3 1 0 0 0 1 0 0 0 0 0
18 57 72 90 93 95 98 99 99 99 99 100 100 100 100 100 100
0 6 0 21 9 21 8 15 4 7 2 5 1 0 0 0 1
0 6 6 27 36 57 65 80 84 91 93 98 99 99 99 99 100
18 51 66 e 63 57 38 33 19 15 8 6 2 1 1 1 1 100
a
Data Analysis To determine the degree of agreement for the paired measurements, we calculated intraclass correlation coefficients (ICCs) for the SLBP Group, the NSLBP Group, and the SLBP and NSLBP Groups combined. We also used the ICC to find the degree of agreement, or interrater reliability, between the paired measurements, or the first measurements, taken by the two examiners on the 11 NSLBP Group subjects in the interrater reliability portion of the study. To determine the intrarater reliability for the two measurements taken by each therapist who examined the 11 NSLBP Group subjects for interrater reliability, we calculated an ICC for each therapist's paired measurements. The ICC used
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SLBP = with "significant" limiting low back pain. NSLBP = without "significant" limiting low back pain. c Cumulative frequencies. d Represents the difference between the cumulative frequencies for a given cell for the SLBP and NSLBP Groups. e Largest difference between cumulative frequency bins. Critical value for cell difference for the Kolmogorov-Smirnov test (n = 100, p < .01) is .16. b
was that described by Shrout and Fleiss (equation 1,1).25 We also calculated distributions of backward bending for the SLBP and NSLBP Groups using bin intervals of 0.25 cm, starting with 0.25 cm and ending with 4.00 cm. Frequency counts and cumulative frequency counts for each bin interval then were made, and the two distributions were compared using the Kolmogorov-Smirnov test26 (Tab. 3).
RESULTS The ICC value for the 100 paired measurements taken on the SLBP Group was .93. The ICC value for the 100 paired measurements taken by the same examiner on the NSLBP Group was .90. The ICC value for the entire sample of 200 paired measurements was .95. Intrarater reliability, therefore, ranged from .90 to .95 (Tab. 4). To determine the influence of certain traits on reliability (eg, sex, height, leg PHYSICAL THERAPY
pain), we calculated ICCs for several subgroups (Tab. 4). All of the calculated ICCs were within . 15 of those calculated for the larger groups. The ICC value for interrater reliability was .94. This value was determined by calculating an ICC using the first measurement obtained by each of the two examiners who measured 11 subjects in this part of the study. For the subjects used in the intertester reliability portion of the study, we calculated the intratester reliability that was obtained by each of the two examiners. Thefirstexaminer obtained an ICC of .98 for the 11 subjects, and the ICC for the second examiner's two measurements was .97. The subjects in the SLBP Group demonstrated a mean backward bending value of 0.6 cm (s = 0.4 cm) with a range of 0.0 cm to 2.8 cm (Tab. 5). The subjects in the NSLBP Group demonstrated a mean backward bending value of 1.58 cm (s = 0.7 cm) with a range of 0.3 to 4.45 cm. The results of a Kolmogorov-Smirnov test showed these two distributions to be significantly different. DISCUSSION Intrarater Reliability The attraction method appears to be highly reliable for measuring backward bending of the lumbar spine when the TABLE 4 Intraclass Correlation Coefficients for Intratester Reliability of Various Subgroups Group All subjects SLBPa Group NSLBPb Group All men All women MeninSLBP Group Men in NSLBP Group Women in SLBP Group Women in NSLBP Group SLBP Group subjects with leg pain SLBP Group subjects without leg pain
same examiner measures a subject twice without a long intertest interval. Repeated measurements on SLBP and NSLBP Group subjects demonstrated high ICC values, thus establishing population-specific intrarater reliability for patients with LBP and for a healthy group. The stability of the attraction method over longer time intervals (ie, from one day to the next) was not examined in this study and should be investigated before this method can be considered reliable for making longterm serial measurements of patients.
200 100 100 87 113
.95 .93 .90 .91 .96
50
.91
16-21
37
.81
22-28
50
.94
29-36
63
.94
37-43
29
.94
TABLE 5 Values for Backward Bending by Age and Sex Age (yr)
a
Sex
n
SLBP Group (cm)
n
NSLBPb Group (cm)
s
44-50 51-57 Over 57
.92
a
Volume 67 / Number 3, March 1987
The results of the Kolmogorov-Smirnov test demonstrate that the SLBP and NSLBP Groups have different distributions of measurements for backward bending. More of the SLBP Group subjects have smaller amounts of motion than the NSLBP Group subjects. Theoretically, anthropometric factors, such as height and weight, may have contributed to this difference. As Table 2 shows, however, the subjects in each group were quite similar. Many authors have suggested that spinal motion changes with age and according to sex.5,7,14,15,27 When establishing normative data for spinal motion, therefore, age and sex should be considered. Values for backward bending measurements according to age and sex are shown in Table 5. The age range for the entire sample was 16 to 76 years. Both groups showed a decrease in backward bending with an increase in age. For each age category, subjects in the NSLBP Group tended to have more movement than those in the SLBP Group (Tab. 5). Inferences based on this observation, however, must be weighed against the small sample size and the unequal cell size. The NSLBP Group had a mean age of 32.4 years (s = 12.3 years), whereas the SLBP Group had a mean age of 37.6 years (s = 11.6 years).
We found the attraction method to have demonstrated high interrater reliability for a small sample of subjects from the NSLBP Group. Before these results can be generalized to other groups, however, at least three factors must be taken into account. First, the sample did not include subjects with SLBP; thus, the method has not been proven to have population-specific interrater reliability (ie, that patients with LBP would have a different interrater reliability). Second, the small sample size limited the strength of this portion of the study. Finally, for interrater reliability to be proven in the attraction method, research must demonstrate that any person trained to perform this technique can do so repeatedly with a reasonable degree of accuracy. Further studies, therefore, are needed to examine the interrater reliability of the attraction method using several examiners to
ICC
SLBP = with "significant" limiting low back pain. b NSLBP = without "significant" limiting low back pain.
Distribution of Backward Bending Measurements
Interrater Reliability
Number of Subjects
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RESEARCH measure a larger sample of SLBP and NSLBP subjects.
TOTALS a b
M F M F M F M F M F M F M F
1 5 11 31 13 18 3 2 5 2 2 0 2 5 100
0.90 1.00 0.73 1.00 0.57 0.73 0.42 0.58 0.26 0.50 0.33 0.48 0.50 0.20 0.60
0.78 0.28 0.39 0.81 0.29 0.47 0.16 0.33 0.18 0.41 0.21 0.27 0.19 0.45
s 3 2 12 9 18 12 6 6 7 8 3 8 1 5 100
2.00 2.26 1.89 1.73 1.32 1.77 1.27 1.40 1.16 0.95 1.10
0.44 1.01 0.58 0.46 0.64 0.25 0.85 0.55 0.07 0.14
0.75 0.58 1.58
0.35 0.30 0.69
SLBP = with "significant" limiting low back pain. NSLBP = without "significant" limiting low back pain.
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In the SLBP Group, 51 % of the subjects were between the ages of 22 and 36 years. The NSLBP Group was composed of 63 women and 37 men, whereas the SLBP Group was composed of 50 men and 50 women. The NSLBP Group contained 31 women aged 22 to 28 years and 18 women aged 29 to 36 years, as compared with 9 women aged 22 to 28 years in the SLBP Group. The NSLBP Group contained 13 men aged 29 to 36 years compared with 18 men in the SLBP Group. The NSLBP Group contained 11 men aged 22 to 28 years compared with 12 men in this cell for the SLBP Group. Overall, the age and sex characteristics of both groups appear to be reasonably close with the exception of the disproportionately high number of women aged 22 to 28 years in the NSLBP Group. This large cell is a result of the sample being drawn, in part, from physical therapy students, the majority of whom were women aged 22 to 28 years. The mean backward bending value for this subgroup was 1.66 cm compared with the overall mean of 1.58 cm for the NSLBP Group. When the backward bending values for the 31 female subjects aged 22 to 28 years were not used, the mean for the NSLBP Group was 1.56 cm. The large number of women aged 22 to 28 years in the NSLBP Group did not appear to affect the mean significantly. Further study will be needed to establish definitive normative data for backward bending of the lumbar spine as measured by the attraction method. Initially, the attraction method will have to be proven to have interrater reliability to ensure that different raters will agree. Future studies also should measure larger samples of the appropriate survey groups and report the results by age and sex. This study was not intended to provide conclusive normative data for backward bending of the lumbar spine but rather to illustrate the results of a preliminary investigation and to provide initial data that can be used with caution.
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Based on our data, we found that the SLBP Group subjects appeared to have less backward bending than the NSLBP Group subjects. This observation is in agreement with similar research by McKenzie.21 Although the results of our study confirm that SLBP patients have less backward bending than healthy subjects, our study is descriptive, rather than demonstrative, because we did not attempt to show whether a cause-andeffect relationship existed between LBP and limitations in backward bending. Many questions relative to limited backward bending and LBP remain unanswered. Is limited backward bending, for example, a cause of LBP or its effect? If the patient's normal backward bending is restored, will the pain decrease, or is limited backward bending a protective mechanism used to guard against further injury? Kapp et al performed a retrospective study on 67 patients meeting these criteria for a herniated nucleus pulposus (HNP).23 The authors stated that those subjects who regained their normal lumbar extension reported relief of pain but that those subjects who did not regain normal lumbar extension required surgery. Thesefindings,however, only are applicable to those subjects meeting those authors' criteria for HNP. Further study is necessary to determine the relationship of limited backward bending to other painful spinal disorders such as muscle or ligamentous injury and diffuse degenerative joint disease. Therefore, the use of a reliable measurement of backward bending could be clinically significant. Our study has demonstrated the reliability of the attraction method for measuring backward bending of the lumbar spine and for determining whether LBP subjects exhibit similar motions as NSLBP subjects. Future research will be needed to examine the validity of this method. We believe one proof would be to compare measurements obtained from radiographs with those obtained by using the attraction method. Despite its frequency, LBP remains one of the most perplexing and chal-
lenging problems treated by physical therapists. The human spine is a poorly understood, multisegmental structure that has not been examined with accurate measurement techniques. Patients with complaints of spinal pain often present clinical pictures clouded by psychosocial effects often resulting from the medical profession's poor understanding of LBP. The use of the attraction method is a step toward helping both the clinician and the researcher to gain a better understanding of LBP. CONCLUSIONS We have found that the attraction method for measuring backward bending of the lumbar spine had good intrarater reliability for repeated measures within a short time span on a sample of 100 SLBP Group subjects and 100 NSLBP Group subjects. We found no appreciable difference in intrarater reliability between SLBP or NSLBP Group subjects. In a sample of 11 NSLBP Group subjects, we also demonstrated that the attraction method for measuring backward bending of the lumbar spine does have interrater reliability. Before these findings can be generalized to other groups, however, further study is necessary. The comparison of distributions of measurements of backward bending for 100 SLBP Group subjects and 100 NSLBP Group subjects showed that the SLBP Group tended to have less backward bending than the NSLBP Group. Comparisons of the two groups by age and sex demonstrated that the SLBP Group consistently had less backward bending than the NSLBP Group. Acknowledgments. We thank Philip Breidenbough, PT, for his assistance in this study and Dan Riddle, PT, for his assistance in the analysis of these data and in the preparation of this manuscript.
PHYSICAL THERAPY
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