Low back pain is considered

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1 The Relationship Between Lumbar Segmental Motion and Pain Response Produced by a Posterior-to-Anterior Force in Persons With Nonspecific Low Back Pain George J. Beneck, PT, MS, OCS 1 Kornelia Kulig, PT, PhD Robert F. Landel, DPT, OCS Christopher M. Powers, PT, PhD 3 Journal of Orthopaedic & Sports Physical Therapy Study Design: Cross-sectional. Objective: To investigate the association between lumbar segmental motion and pain response during the application of a posterior-to-anterior (PA) force to the lumbar spinous processes in persons with nonspecific low back pain. Background: Although low back pain is believed to be associated with altered segmental motion of the lumbar spine, the relationship between subjective reports of pain and objective measurements of segmental motion has not been established. Methods and Measures: Thirty-five individuals between 1 and 5 years of age with nonspecific low back pain (less than 3 months duration) participated. All subjects participated in separate procedures: (1) segmental motion assessment during a PA force application over the lumbar spinous processes using dynamic magnetic resonance imaging (MRI), and () pain assessment during a PA force application procedure outside of the MRI environment. Frequency counts were used to determine the lumbar segments that were most painful, and which functional spinal units had the most and least motion. Fisher exact tests were performed to determine if an association existed between the most painful segment and the functional spinal unit with the most or least motion. Results: L5 was deemed the most painful segment in nearly half of the participants (.1%). The L1- and L3- functional spinal units most frequently had the most motion (5.9% each) and the L-5 functional spinal units most frequently had the least motion (9.%). No association was found between the most painful segment and the functional spinal units with either the most or least motion. Conclusion: The results of this study indicate that an assumption regarding segmental motion cannot be inferred from the pain response when using a PA force application procedure. J Orthop Sports Phys Ther 5;35:3-9. Key Words: lumbar spine, manual therapy, painful segment 1 PhD student, Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA; Lecturer, Department of Physical Therapy, California State University Long Beach, Long Beach, CA. Associate Professor of Clinical Physical Therapy, Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA. 3 Associate Professor and Assistant Chair, Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA. This study was funded by a grant from the Foundation for Physical Therapy. The protocol for this study was approved by the Institutional Review Boards of Stanford University and the University of Southern California. Address correspondence to Christopher M. Powers, Department of Biokinesiology and Physical Therapy, University of Southern California, 15 E Alcazar St, CHP-155, Los Angeles, CA powers@usc.edu Low back pain is considered to be a significant health and economic problem 11,9 affecting approximately 7% to % of adults at some time in their lives. This condition is the most costly musculoskeletal problem affecting industrialized nations with annual costs in the billions. 7 Low back pain is the most common complaint of patients attending outpatient physical therapy and accounts for an estimated 5% of patient visits. 1 Low back pain has been reported to be associated with abnormal lumbar motion. For example, pain was found to be associated with limited gross lumbar motion 5,19, as well as decreased segmental motion. 17, Using an inclinometer, Mellin 19 found diminished spinal extension in both male and female subjects with low back pain. Radiographic measurements of intervertebral lumbar displacements in patients with low back pain revealed decreased motion in both flexion and extension when compared to asymptomatic controls. In the presence of low back pain, motion has been shown Journal of Orthopaedic & Sports Physical Therapy 3

2 to be more limited in extension than flexion., In contrast, only 1 study was identified that reported an association between low back pain and excessive motion. 1 Segmental motion was examined using a manual assessment procedure. Higher disability scores resulting from low back pain were found in subjects deemed hypermobile, as well as hypomobile, when compared to subjects with normal mobility. In managing patients with low back pain, clinicians often make treatment decisions based on motion abnormalities perceived during the examination process. Posterior-to-anterior (PA) force application over the lumbar spinous processes is one such clinical procedure that is commonly used to assess segmental motion and identify symptomatic spinal segments. The findings resulting from this procedure are an important factor in determining the type of intervention prescribed. When a segment is identified as painful and deemed hypomobile, mobilization is typically prescribed 3,,15, ; when a segment is found to be painful and deemed hypermobile, stabilization is often prescribed.,3 While the PA force application procedure is well defined, 15 it is subjective in both the amount of force applied by the examiner and in the determination of the quantity of motion (ie, the presence of hypomobility or hypermobility). Moreover, the association between subjective reports of pain and objective measurements of segmental motion during this procedure has not been established. In other words, it is not known if painful lumbar functional spinal units tend to have more motion or less motion. Hence, the purpose of the study was to use dynamic imaging techniques to investigate the association between lumbar segmental motion and pain response during a PA force application procedure in persons with nonspecific low back pain. METHODS Subjects Thirty-five individuals (1 men and 19 women) between the ages of 1 and 5 years (mean, 31. years), with a diagnosis of nonspecific low back pain, participated in this study. Individuals over the age of 5 were excluded to control for the possible confounding effects of spine osteoarthritis. The subjects had a mean height of 17. ± 1.3 cm, a mean mass of 7. ± 1. kg, and a mean body mass index (BMI) of 3.5 ± 3. kg/m. Only those individuals who reported a recent onset (within the last 3 months) of low back pain at or above the level of the waist and increased pain with lumbar extension in standing were admitted to the study. During standing spinal extension, subjects reported a mean (±SD) pain score of. ± 1.9 using a 1-cm visual analog scale (with representing no pain and 1 the worst pain imaginable) and demonstrated a mean (±SD) of 1. ±. cm of extension as measured by a modified-modified Schó ber test. 31 Subjects were excluded from the study if they demonstrated any of the following: (1) spinal malignancy, () cardiovascular disease, (3) evidence of cord compression, () aortic aneurysm, (5) hiatal hernia, () uncontrolled hypertension, (7) spinal infection, () severe respiratory disease, (9) pregnancy, (1) abdominal hernia, (11) prior low back surgery, (1) gross spinal deformity, (13) spondylolisthesis, (1) known rheumatic joint disease, and (15) implanted biological devices that could interact with the magnetic field (ie, pacemakers, cochlear implants, or ferromagnetic cerebral aneurysm clips). In addition to the above exclusion criteria, subjects could not have any clinical evidence of lumbar disc pathology. Therefore, subjects who demonstrated any of the following were also excluded: (1) radiating pain below the level of the buttock(s), () sensation changes in the lower extremities, (3) diminished reflexes, () lower extremity weakness, (5) urinary or fecal incontinence, and () increased peripheral pain with repeated lumbar extension. All subjects were screened by the same physician to ensure consistency of the physical exam. Instrumentation As in a previous investigation, 5 dynamic imaging of the lumbar spine was performed using a vertically open (double-donut design) MRI system (.5, Signa SP, General Electric Medical Systems, Milwaukee, WI), with a 5-cm opening that allowed the examiner unrestricted access to the subject during testing. This system was equipped with a pulse sequence programming environment and real-time interactive MRI capability. Sagittal plane imaging of the spine was performed using a standard transmit-receive surface coil and an ultrafast spoiled gradient recalled acquisition in the steady state (GRASS) pulse sequence. The design of the coil allowed the examiner to have direct access to the lumbar spinous processes. Images were obtained at a rate of 1 per second using the following parameters: repetition time, ms; echo time, 1 ms; number of excitations, 1.; matrix, 5 5; field of view, 1 cm; and a 7-mm section thickness with an interslice spacing of 1 mm. 5 Procedure Prior to participation, all subjects were informed of the nature of the study, procedures, and risks. Each subject then signed a human subjects consent form as approved by the Institutional Review Board of Stanford University and the University of Southern California. All subjects participated in separate J Orthop Sports Phys Ther Volume 35 Number April 5

3 procedures: (1) segmental motion assessment using MRI and () pain assessment outside of the MRI environment. Separate procedures were used to prevent investigator bias with respect to applying the PA forces during the MRI assessment. If the investigator performing the motion test was aware of the painful segment, less force may have been applied at that segment during the motion testing procedure. In all cases, the MRI procedure was performed first. Subjects were placed in the prone position with a pillow under the abdomen on a sliding table situated within the opening of the MRI system (Figure 1). Subjects were positioned such that the lumbar spine was centered within the magnet. A surface coil was secured to the lower torso using cloth tape. Using a technique described by Maitland et al, 15 a physical therapist with years of manual therapy experience, who is a Fellow of the American Academy of Orthopedic Manual Physical Therapists (AAOMPT), manually applied a single PA force through the spinous process of L5, which was followed by the sequential application of PA forces to the spinous processes of L, L3, L, and L1. In all cases the forces were applied sequentially with images being obtained continuously through the procedure. The amount of force applied was aimed at reaching the end range of the segmental motion and was comparable in magnitude to that of a grade IV as defined by Maitland et al. 15 A third investigator observed the imaging during the data collection on-line and ensured that the examiner applied the force at the designated spinous process. Following the MRI procedure, subjects were removed from the MRI environment and placed in an adjacent examination room. As with the initial assessment, subjects were positioned prone with a pillow under the abdomen. A second physical therapist, with 1 years of manual therapy experience and certified as an Orthopaedic Clinical Specialist (OCS) by the American Physical Therapy Association, performed the pain assessment. Prior to applying the PA force, participants were instructed to report which of the upcoming force applications reproduced their pain and rate the pain intensity via an 11-point verbal rating scale ( representing no pain and 1 the worst imaginable pain). The therapist then applied a single PA force through the spinous process of L5 and subsequently through L, L3, L, and L1. At each segment, the PA force was performed progressively from grade I through IV, as defined by Maitland et al. 15 The pain response was assessed at each grade and the segment where the PA force elicited the highest pain rating was recorded as the most painful segment. To control for differences in the force applied between the testing sessions, the testers practiced the force application procedure outside of the MRI environment prior to testing. Using a hand-held FIGURE 1. Subject and examiner positioning within the MRI system. Each subject was situated such that the spine and torso were within the opening between the vertical magnets. The examiner is shown applying a posterior-to-anterior force to a spinous process during imaging. dynamometer for feedback, the testers practiced applying the PA force until it was established that the force produced was consistently between 9.1 and 11. kg. Image analysis Prior to analysis all images were transferred from the MRI system console to a Macintosh G-3 computer. For purposes of this study, only the images of the vertebral segments at rest and at the end range of segmental motion were analyzed. 5 Sagittal plane intervertebral angles were measured using National Institutes of Health Image Software (National Institutes of Health, Bethesda, MD). The intervertebral angle was defined as the angle formed by lines delineating adjacent vertebral endplates. Segmental lumbar motion was defined as the difference between the intervertebral angles measured from the resting and end range images. Angular displacements at the L1-, L-3, L3-, L-5, and L5-S1 functional spinal units were compared to identify the functional spinal units with the most and least motion. The same investigator took all measurements and was blinded to the painful segment. To establish the intratester reliability of assessing the intervertebral angle, repeated measurements were obtained from 5 subjects. All together, 5 repeated measures were J Orthop Sports Phys Ther Volume 35 Number April 5 5

4 Mean Extension (deg) FIGURE. Mean segmental motion at each functional spinal unit during posterior-to-anterior force application to the superior vertebra (n = 7). The bars represent 1 SD. obtained from each subject (5 measurements at each vertebral level, on separate occasions, 1 week apart). Intraclass correlation coefficients (ICC 3,1 ) for each subject were found to be excellent, ranging from.95 to.99. The overall standard error of measurement ranged between. and.. Statistical Analysis Frequency histograms were used to demonstrate the segments that were most painful and the functional spinal units with the most motion and least motion. Due to cell sizes of less than 5, the Fisher exact test was performed to determine if an association existed between the most painful segment and the functional spinal units with the most or least motion. The alpha level was set at.5. RESULTS L1- L-3 L3- L-5 L5-S1 Functional Spinal Unit Of the 35 subjects evaluated, 7 reported a most painful segment. The PA force application procedure did not reproduce pain in. One subject reported an equal intensity of pain at segments, while another subject reported an equal intensity of pain in all 5 lumbar segments. The data from these subjects were subsequently excluded from the analysis. As in previous studies, 1,5 application of the PA force resulted in extension at every tested vertebra. The mean extension produced by the PA force applied to the superior segment of each functional spinal unit is shown in Figure. Figure 3 shows the distribution of the functional spinal units with the most motion during the PA force application procedure. The L1- and L3- functional spinal units most frequently had the most motion (5.9%), followed by L5-S1 (.%), L-3 (1.%), and L-5 (11.1%). Figure shows the distribution of the functional spinal units with the least motion during the PA force application procedure. The L-5 functional spinal unit most frequently had the least motion (9.%), followed by L1- (5.9%), L3- (.%), L5-S1 (1.5%), and L-3 (3.7%). The distribution of the most painful segment during the PA force application procedure is shown in Figure 5. L5 was the most frequently symptomatic, being most painful in nearly half of the participants (.1%). L was the second most frequently painful segment (5.9%), followed by L3 (1.%), L1 (7.%), and L (3.7%). The frequency of match between the painful segments and the functional spinal units with the most and least motion is shown in Tables 1 and, respectively. The Fisher exact test indicated no association between the most painful segments and the functional spinal units with the most (P =.3) or least motion (P =.7). Number of Subjects L1- L-3 L3- L-5 L5-S1 Functional Spinal Unit With the Greatest Amount of Motion FIGURE 3. Distribution of functional spinal units with most motion during posterior-to-anterior force application (n = 7). Number of Subjects L1- L-3 L3- L-5 L5-S1 Functional Spinal Unit With the Least Amount of Motion FIGURE. Distribution of functional spinal units with least motion during posterior to anterior force application (n = 7). J Orthop Sports Phys Ther Volume 35 Number April 5

5 Number of Subjects Reporting Pain FIGURE 5. Distribution of most painful segment during posterior-toanterior force application (n = 7). DISCUSSION L1 L L3 L L5 Lumbar Level Clinicians often prescribe interventions based on their assessment of pain and motion. Although an association between low back pain and spinal motion has been described in the clinical literature, 3,9,1,,3 the association between pain elicited by manual therapy procedures and segmental spinal motion has not been established. Results of the current study did not find an association between segments deemed most painful and the functional spinal units with either the most or least motion, as defined through sagittal plane MRI assessment. Of the 7 subjects, only 3 reported pain with force applied to the superior segment of the functional spinal unit with the most motion and 5 reported pain with force applied to the superior segment of the functional spinal unit with the least motion. These findings suggest that an assumption regarding segmental motion cannot be made when a painful segment is identified. The present results are not in agreement with findings of previous studies that demonstrate an association between pain and reduced segmental motion. 17, The lack of agreement may be due to the differences in how motion was measured. In both of the above-noted studies, motion was produced actively by the subjects and not passively, as was done in the current investigation. Pearcy et al had their subjects bend forward and backward while motion was measured with biplanar radiography. McGregor et al 17 had subjects perform a rowing motion while spinal mobility was assessed using an interventional MRI scanner. The results of the present study do not support the findings of Lundberg and Gerdle, 1 who reported an association between increased segmental motion and disability resulting from low back pain. However, the results of the present study are in agreement with findings of studies that reported no association between pain and increased segmental motion. 7,1,,7 There are several possible explanations for the lack of association between pain and lumbar segmental motion in the present study. First, motion was only measured in the sagittal plane. It is possible that during the PA force application procedure motion occurred in the transverse or frontal planes as well, and that the combined motion in the planes may have been more closely associated with the most painful segments. Second, protective muscle guarding by the subjects may have limited the amount of motion at the painful segment. It stands to reason that persons with low back pain would want to avoid segmental motion, particularly if a given segment was painful. Such splinting could be accomplished by increasing intra-abdominal pressure or by active muscle contraction of the lumbar extensors. Third, given that the pain assessment was performed outside the MRI environment, the second examiner may not have accurately identified the segment being tested. As a result, the procedure may not have named the correct segment where pain was provoked. The most painful segment was at L or L5 (7% of the subjects). This is consistent with clinical literature that describes these segments as the more common sites of pathology.,9, The functional spinal unit with the most sagittal plane motion was expected to TABLE 1. Crosstabulation of painful segments and functional spinal units with most motion. Matches in bold. (P =.3, df = 1) Painful Segment Functional Spinal Unit L1 L L3 L L5 Total L L L3-1 7 L L5-S1 3 1 Total TABLE. Crosstabulation of painful segments and functional spinal units with least motion. Matches in bold. (P =.7, df = 1) Painful Segment Functional Spinal Unit L1 L L3 L L5 Total L L L3- L L5-S1 3 5 Total J Orthop Sports Phys Ther Volume 35 Number April 5 7

6 be L5-S1, followed by L-5 3 ; however, L5-S1 and L-5 showed the most motion in only % and 11% of the subjects, respectively. Surprisingly L1- and L3- more frequently demonstrated the most motion. This inconsistency may be explained by methodological differences between the studies. In the literature reviewed by White and Panjabi, 3 motion was measured during active bending in standing, with values reported as combined flexion and extension, as opposed to the current study, where motion was measured with subjects lying prone and produced passively by an examiner. Force application during the PA force application procedure was standardized prior to testing, but due to the magnetic environment, it was not measured during the MRI procedure. Therefore, any differences in the amount of force applied during the motion and pain assessment procedures were not known. The fact that both examiners consistently applied similar forces during preliminary testing suggests that comparable forces were used during both the motion and pain assessment procedures. It also should be noted that although only 1 examiner performed the pain assessment procedure, previous investigations have demonstrated good intertester reliability of pain assessments using manual techniques. 13,1,1 Caution is advised in generalizing the results of this study to the entire low back pain population, as participants were relatively young, exhibited moderate symptoms, and had no evidence of lumbar disc pathology or osteoarthritis. Assessment of older subjects, subjects suffering from severe pain, or subjects with evidence of lumbar disc pathology or osteoarthritis may yield different results. CONCLUSION No association was found between the segmental level where pain was reproduced with a PA force and the amount of segmental motion in persons with nonspecific low back pain. 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