Authors: Hak Il Lee, MD Seok Tae Lee, MD MinYoung Kim, MD, PhD Ju Seok Ryu, MD, PhD
Low-Back Pain
Affiliations: From the Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Gyeonggi-do, Republic of Korea. The new affiliation for Dr. Ryu is Department of Rehabilitation Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
Correspondence: All correspondence and requests for reprints should be addressed to: Ju Seok Ryu, MD, PhD, Department of Rehabilitation Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 82 Gumi-ro 173 beon-gil Bundang-gu, Seongnam, 463-707, Korea.
Disclosures: No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. No funds were received in support of this work. This study was not presented in any form. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/15/9402-0123 American Journal of Physical Medicine & Rehabilitation Copyright * 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000149
ORIGINAL RESEARCH ARTICLE
Sex Differences in Predicting Chronicity of Low-Back Pain After Acute Trauma Using Lumbar Muscle Area ABSTRACT Lee HI, Lee ST, Kim MY, Ryu JS: Sex differences in predicting chronicity of lowback pain after acute trauma using lumbar muscle area. Am J Phys Med Rehabil 2015;94:123Y130.
Objective: The aim of this study was to investigate sex differences in predicting chronicity of low-back pain after acute trauma using cross-sectional areas of paraspinal (multifidus and erector spinae) and psoas muscles. Design: Between January 2006 and December 2010, a total of 54 patients were interviewed at least 6 mos after the trauma event. The subjects were classified into chronic low-back pain group and improved low-back pain group according to the presence of low-back pain for more than 6 mos. The crosssectional area of the multifidus, erector spinae, and psoas muscles was measured at the level of the lower margin of the L3 and L5 vertebrae using magnetic resonance imaging.
Results: The cross-sectional area of the multifidus and erector spinae muscles at L5 in the chronic low-back pain group was significantly smaller than that of the improved low-back pain group (P G 0.05) in the men. There were no significant differences in the other parameters between the groups in the men. There were no significant differences in any parameters in the women.
Conclusions: In the men, the cross-sectional area of the multifidus and erector spinae muscles at the lower lumbar level can be considered to be prognostic factors for the chronic low-back pain after acute trauma. The authors thus suggest that strengthening of lumbar paraspinal muscles could be helpful for preventing chronicity of low-back pain. Key Words: Muscles
www.ajpmr.com
Low-Back Pain, Magnetic Resonance Imaging, Cross-Sectional Area,
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
123
L
MATERIALS AND METHODS
ow-back pain (LBP) is one of the most common diseases, with approximately 80% of the adult population experiencing it at least one or more times in their life time.1 Most patients experiencing acute LBP usually recover within 6Y12 wks. However, a large portion of them experience symptom recurrence, with some of them developing chronic LBP (CLBP).1,2 In a large prospective study including 4261 patients, 21.4% showed CLBP at discharge and 26.5% showed clinical disability.3 Factors predicting a clinically relevant improvement in LBP at 3 mos were clinical features at baseline (pain being acute, as opposed to subacute or chronic; higher severity of LBP; lower severity of leg pain and disability) and treatments received (not having undergone lumbar surgery and having been treated with neuroreflexotherapy).3 LBP restricts functional and occupational activities and is detrimental to society and the economy. Thus, appropriate treatment is important.1,2,4 It is generally thought that muscular weakness is linked to LBP, even though the main direction of this link is unclear. Several exercise protocols emphasize lumbar stabilization and core strengthening,5Y7 with a particular focus on the multifidus muscle. The multifidus muscle is attached to the spine at every one to two segments to provide stability and is known to be sensitive to pathologic change. Lumbar stabilization exercises for the multifidus muscle are known to improve LBP and reduce its rate of recurrence.5Y7 To date, there have been several studies of lumbar muscle changes as an index of functional disability in patients with LBP. These studies have reported lumbar muscle atrophy in CLBP patients.8Y13 However, few reports have evaluated the association between the chronicity of acute LBP and the cross-sectional area (CSA) of lumbar muscles. Preliminary data were reported regarding the association between the chronicity of acute LBP and the CSA of lumbar muscles,12 but given the small sample size, the authors were unable to evaluate differences regarding sex and were unable to verify multifidus muscle CSA as a risk factor of CLBP. Therefore, the first aim of the current study was to investigate the influence of the CSA of the paraspinal (multifidus and erector spinae) and psoas muscles and to investigate the predictive values of each muscle on the chronicity of LBP after acute trauma. The second aim was to investigate sex differences in predicting the prognosis of LBP using the CSA of the paraspinal muscles.
124
Lee et al.
Subjects This study was a retrospective cohort study of patients who visited the authors’ teaching hospital for acute LBP and underwent lumbar magnetic resonance imaging (MRI). Between January 2006 and December 2010, a total of 1001 patients (477 men and 524 women) were enrolled in this study’s cohort. Inclusion criteria were as follows: (1) patients who complained of LBP after trauma including in-car accident, car-pedestrian accident, and sport injury; (2) patients who could ambulate and perform activities of daily living and be treated as an outpatient by themselves; (3) age between 20 and 40 yrs; (4) no definite history of LBP; (5) selfreported pain levels of more than 3 on the visual analog scale (VAS; 0~10); (6) MRI performed within 1 mo from the first appearance of symptoms; (7) patients who were treated with oral medication and/ or physical modality and/or back exercise and/or trigger point injection; and (8) no abnormal findings (disk herniation, disk bulging, spinal stenosis, spondylolysis, spondylolisthesis, scoliosis, facet arthritis, spinal fracture, disk degeneration, etc.) on lumbar MRI and normal official radiology report. Thirty-nine men and 35 women satisfied the inclusion criteria. The authors initially evaluated the VAS and presence of radicular symptoms in the lower extremities. The VAS is an easy-to-use evaluation tool for chronic pain and has been used in a wide range of clinical and research settings, with known reliability and validity.14 The therapies received (medication, physical modality, exercise therapy, and trigger point injection) were also reviewed. The authors conducted an interview for persistence of LBP at least 6 mos later. Seven men and 11 women who refused the interview or who changed their postal address or telephone numbers were excluded from the study. A total of 56 subjects (32 men, mean [SD] age, 30.0 [4.5] yrs, and 24 women, mean [SD] age, 29.0 [5.7] yrs) participated in the study. The etiologies of trauma in these 56 patients were in-car accidents (n = 52), car-pedestrian accidents (n = 3), and sport injury (n = 1). The major pathologies of trauma were minor low-back strains and sprains. The subjects were divided into two groups according to the duration of their LBP, namely, a CLBP group and an improved LBP (ILBP) group. The CLBP group was defined as patients who experienced LBP for more than 6 mos, and the ILBP group was defined as patients who showed ILBP within 6 mos.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
FIGURE 1 The CSA of the paraspinal and psoas muscles (B) obtained on axial T2-weighted images at the lower margin of the L3 and L5 vertebrae (A) using the Marosis m-view version 5.4 program. ES indicates erector spinae; Mu, multifidus.
All patients gave informed consent for their clinical details and scans to be used in this study, and the study protocol was approved by the institutional review board of the hospital.
Methods The duration of LBP, height, and body weight were recorded during the interviews. The CSA of the paraspinal muscles (multifidus and erector spinae) and the psoas muscles was obtained from axial T2-weighted images at the lower margin of the L3 and L5 vertebrae using the Marosis m-view version 5.4 program (Fig. 1).12 This image is superior in distinguishing muscle from fat. The authors measured only muscle area excluding fat tissues. The CSA of the multifidus and erector spinae muscles in the paraspinal muscles and the psoas muscles was measured separately on each side. The proportions of the bilateral L5 multifidus and erector spinae muscles from the summation of bilateral erector spinae, multifidus, and psoas muscles were calculated.
The authors evaluated the differences in the CSA and the proportions of these muscles between the CLBP and ILBP groups in each sex. Body weight (kilograms) was divided by the square of height (meters) to calculate the body mass index.
Statistics Statistical analysis was performed using the Statistical Package for the Social Sciences 19.0. The Mann-Whitney U test and the W2 test were used to compare the differences between the two groups. The value that maximized the area under the receiver operating characteristic curve was chosen as a cutoff point for sensitivity and specificity and was used to predict the chronicity of LBP. Statistical significance was considered at P G 0.05. All data were presented as mean (standard deviation).
RESULTS The demographic data are shown in Table 1. The age, height, weight, and body mass index did
TABLE 1 Demographic data of subjects
Male
Age, yrs Height, m Weight, kg BMI, kg/m2
Female
Age, yrs Height, m Weight, kg BMI, kg/m2
ILBP Group (n = 18)
CLBP Group (n = 14)
P
31.28 (4.52) 1.76 (0.05) 72.56 (9.39) 24.37 (2.68) ILBP group (n = 17) 28.35 (5.44) 1.62 (0.05) 54.47 (7.40) 20.30 (2.24)
28.35 (4.01) 1.76 (0.06) 72.21 (8.71) 24.31 (2.87) CLBP group (n = 7) 30.57 (6.62) 1.64 (0.04) 53.85 (4.29) 19.66 (2.13)
0.11 0.87 0.59 0.72 0.34 0.38 0.95 0.66
Values are mean (standard deviation). a P G 0.05. BMI, body mass index.
www.ajpmr.com
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
125
TABLE 2 Clinical data of subjects
VASa Presence of radicular symptoms, % Methods of therapy
Medications Physical modalities Exercise therapy Trigger point injection
Total (n = 56)
ILBP Group (n = 35)
CLBP Group (n = 21)
P
5.71 (1.75) 42.1 86.8 92.1 31.6 34.2
5.24 (1.64) 32.0 80.0 88.0 28.0 32.0
6.62 (1.67) 61.5 100.0 100.0 38.5 38.5
0.033 0.080 0.084 0.193 0.510 0.690
Values are mean (standard deviation) or percentage. a P G 0.05.
not differ significantly between the two groups in either sex (Table 1). The intervals between acute trauma and MRI examination were 12.5 (8.1) days in the men and 11.9 (8.8) days in the women. The initial mean (SD) VAS score in all included patients was 5.71 (1.75). The mean (SD) VAS scores were 5.24 (1.64) and 6.62 (1.67) in the ILBP and CLBP groups, respectively (P = 0.033, Table 2). Some 32.0% and 61.5% showed radicular symptoms in the ILBP and CLBP groups, respectively (P = 0.080, Table 2). The therapies received are described in Table 2. The rates of therapies received (medications, physical modalities, exercise therapy, and trigger point injection) were not significantly different between the two groups (Table 2). In the men, the CSA of the erector spinae muscle at the lower margin of the L5 vertebra in the CLBP group (right, 8.5 [2.4] cm2; left, 8.8 [2.7] cm2) was significantly smaller than that of the
ILBP group (right, 11.2 [3.6] cm2; left, 11.9 [3.5] cm2; P G 0.05; Table 3). The multifidus muscle at the lower margin of the L5 vertebra in the CLBP group (right, 11.0 [1.8] cm2, left, 10.9 [1.8] cm2) was also significantly smaller than that of the ILBP group (right, 12.5 [1.7] cm2; left, 12.5 [2.0] cm2; P G 0.05; Table 3). However, the mean CSA of the psoas muscles at the lower margin of the L5 vertebra and the CSA of all muscles measured at the lower margin of the L3 vertebra did not differ significantly between the two groups (Table 3). In the women, there were no differences between parameters measured at the L3 and L5 levels between the groups (P 9 0.05, Table 4). The proportions of each muscle in relation to the lumbar paraspinal (summation of multifidus, erector spinae, and psoas) muscles at the L5 level are shown in Table 5 (men only). The proportion of the erector spinae in the CLBP group was significantly smaller than that in the ILBP group.
TABLE 3 The CSA of the paraspinal and psoas muscles at the L3 and L5 levels in men
L3 level
Multifidus, cm2 Erector spinae, cm2 Psoas, cm2
L5 level
Multifidus, cm2 Erector spinae, cm2 Psoas, cm2
Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral
ILBP Group (n = 18)
CLBP Group (n = 14)
P
7.3 (1.4) 6.8 (1.3) 14.1 (2.6) 21.2 (4.3) 21.8 (3.6) 43.1 (7.7) 13.4 (2.0) 13.3 (2.5) 26.7 (4.2) 12.5 (1.7) 12.5 (2.0) 25.0 (3.6) 11.6 (3.5) 12.4 (3.5) 24.1 (7.0) 18.4 (2.9) 17.8 (3.0) 36.3 (5.7)
7.1 (1.1) 6.8 (1.2) 14.0 (2.3) 19.5 (3.0) 20.3 (3.3) 39.9 (6.2) 13.1 (2.7) 12.8 (2.4) 26.0 (5.1) 11.0 (1.8) 10.9 (1.8) 22.1 (3.6) 8.5 (2.4) 8.8 (2.7) 17.4 (5.1) 18.3 (3.7) 17.8 (3.2) 36.2 (6.7)
0.722 0.955 0.750 0.301 0.442 0.338 0.561 0.587 0.419 0.041a 0.041a 0.030a 0.016a 0.007a 0.008a 0.639 0.866 0.722
Values are mean (standard deviation). a P G 0.05.
126
Lee et al.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
TABLE 4 The CSA of the paraspinal and psoas muscles at the L3 and L5 levels in women
Multifidus, cm2
L3
Erector spinae, cm2 Psoas, cm2 Multifidus, cm2
L5
Erector spinae, cm2 Psoas, cm2
ILBP Group (n = 18)
CLBP Group (n = 14)
P
5.7 (1.1) 5.2 (1.0) 11.0 (2.2) 13.0 (2.5) 13.6 (2.5) 26.7 (5.0) 6.9 (1.6) 7.0 (1.1) 14.1 (2.7) 10.5 (1.4) 10.4 (1.5) 21.0 (2.9) 10.7 (3.0) 11.0 (3.1) 21.8 (6.1) 11.0 (1.9) 10.7 (1.2) 21.8 (2.9)
5.9 (0.9) 5.8 (1.1) 11.9 (2.0) 13.3 (1.7) 13.7 (2.1) 27.0 (3.7) 7.6 (2.3) 7.5 (1.4) 15.2 (3.1) 10.0 (1.4) 10.2 (1.2) 20.3 (2.6) 8.8 (2.3) 8.8 (2.0) 17.7 (4.3) 10.7 (2.3) 10.5 (2.5) 21.3 (4.8)
0.710 0.209 0.455 0.852 0.901 1.000 0.455 0.576 0.576 0.494 0.951 0.710 0.147 0.147 0.130 0.757 0.664 0.804
Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral
Values are mean (standard deviation). a P G 0.05.
In the men, the CSA of the bilateral L5 erector spinae muscles had a sensitivity of 83.3% and a specificity of 64.3% at a cutoff value of 1915.8 cm2 (Fig. 2A), and the CSA of the bilateral L5 multifidus muscle had a sensitivity of 94.4% and a specificity of 42.9% at a cutoff value of 2085.2 cm2 for predicting the chronicity of LBP (Fig. 2B). In the men, the proportion of the bilateral L5 erector spinae muscles from the summation of the bilateral erector spinae, multifidus, and psoas muscles had a sensitivity of 94.4% and a specificity of 50.0% at a cutoff value of 0.22, and the CSA of the bilateral L5 multifidus muscle from the summation of bilateral erector spinae, multifidus, and
psoas muscles had a sensitivity of 72.2% and a specificity of 42.9% at a cutoff value of 0.3 for prediction of chronicity of LBP. To increase the sensitivity for prediction of chronicity of LBP, the two significant variables (the area of the multifidus and erector spinae muscles) were combined. The combination of two variables increased the sensitivity to 100% but decreased the specificity to 35.7% (Fig. 2C).
DISCUSSION In the authors’ preliminary study, only the erector spinae was significantly smaller in the CLBP
TABLE 5 The proportion of each muscle to lumbar muscles at the L5 level
Men
Multifidus, % Erector spinae, %
Women
Multifidus, % Erector spinae, %
Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral
ILBP Group (n = 18)
CLBP Group (n = 14)
P
0.30 (0.05) 0.29 (0.04) 0.30 (0.05) 0.27 (0.05) 0.29 (0.05) 0.28 (0.05) ILBP group (n = 17) 0.33 (0.03) 0.33 (0.03) 0.33 (0.03) 0.33 (0.05) 0.34 (0.05) 0.33 (0.05)
0.29 (0.03) 0.29 (0.03) 0.29 (0.03) 0.23 (0.05) 0.23 (0.05) 0.23 (0.05) CLBP group (n = 7) 0.34 (0.04) 0.35 (0.04) 0.35 (0.04) 0.29 (0.05) 0.30 (0.06) 0.30 (0.05)
0.985 0.896 0.750 0.027a 0.004a 0.014a 0.260 0.075 0.114 0.234 0.087 0.187
Proportion means each muscle divided by the sum of the multifidus, erector spinae, and psoas muscles; values are mean (standard deviation). a P G 0.05.
www.ajpmr.com
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
127
FIGURE 2 The CSA of the bilateral erector spinae muscle had a sensitivity of 83.3% and a specificity of 64.3% at a cutoff value of 1915.8 cm2 for predicting the chronicity of LBP (A), and the CSA of the bilateral multifidus muscle had a sensitivity of 94.4% and a specificity of 42.9% at a cutoff value of 2085.2 cm2 (B). The combination of two variables increased the sensitivity to 100% but decreased the specificity to 35.7% (C).
group than in the ILBP group, and the multifidus did not differ significantly between the two groups.12 However, this study was unable to consider men and women separately because of the small sample size. The authors thus extended this study to enroll more patients, with the aim of determining sex differences and the importance of the multifidus as well as the erector spinae muscles. In the present study, the CSA of the multifidus and erector spinae muscles in the men measured at the lower margin of the L5 vertebra was significantly smaller in the CLBP group than in the ILBP group. The present study excluded all patients who had a history of LBP and those who had MRIdocumented lumbar lesions. Thus, these results show that small paravertebral muscles at the low lumbar level in early stages after trauma could predict the persistence of LBP. Many previous studies have shown localized or generalized multifidus muscle atrophy in patients with CLBP.8,10,15,16 Most of these studies, however, included patients who had had CLBP for more than 3 mos8,16 and evaluated the correlation of muscular atrophy with leg pain or nerve root compression.8,16 These findings suggest that multifidus muscle atrophy in patients with CLBP can be associated with lumbar lesions, such as lumbar herniated intervertebral disks, which could irritate the nerve roots, and long duration of back pain. In addition, until now, there has been no study evaluating the size of the erector spinae muscle in patients with CLBP. However, in the present study, MRI was conducted at an early stage of trauma, and thus, the observed atrophy cannot be attributed to disuse. The intervals between acute trauma and MRI
128
Lee et al.
examination were 12.5 (8.1) days in men and 11.9 (8.8) days in women. The present study excluded all patients who had lumbar lesions, including disk bulging, on MRI, to eliminate the influence of lesions on muscle atrophy. Thus, other explanations for the small CSA of the multifidus and erector muscles are required. This exclusion was extended to the investigation of the correlation between the chronicity of adult patients without a history of LBP from acute LBP to chronic pain and the CSA of lumbar muscles on MRI. This study followed up patients who had a lumbar MRI at an early stage of LBP and divided them into two groups according to the persistence of LBP, comparing the CSA of the lumbar muscles between the two groups. Thus, the implications of this study could be regarded as being different from those of previous studies. The results of this study enabled the authors to rule out disuse atrophy and root irritation as possible influences on low lumbar muscular atrophy. Therefore, the authors speculate that patients with small muscle area in the lower lumbar region before trauma are prone to develop CLBP, and therefore, muscle area is important for preventing LBP. Although there may be many possible reasons for acute LBP, most cases are thought to develop after sudden and unexpected posture change or loading on the lumbar spine. If lumbar muscles fail to properly react to such sudden loading, the bending momentum and trunk movement may be greater; this may increase the risk for tissue damage. In such cases, the multifidus and erector spinae muscles play an important role in maintaining posture and balance by stabilizing the lumbar spine.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Therefore, it seems that, for those who have a small CSA of the multifidus and erector spinae muscles, the risk for developing CLBP could be higher. Because the authors evaluated only the size of the lumbar muscles, further study regarding the quality of the lumbar muscles is necessary. The VAS scores were significantly different between the ILBP and CLBP groups (P = 0.033). Because small paravertebral muscles cannot be attributed to disuse, weak lumbar muscles (small CSA) are assumed to cause high VAS scores in the CLBP group. Further work to evaluate the correlation between muscular area, strength, and high VAS scores is required. Because the therapies received (medication, physical modalities, exercise therapy, and trigger point injection) were not significantly different between the two groups, it seems that these variables did not influence the chronicity of LBP. The atrophy of the paraspinal muscles can be evaluated using ultrasound, computed tomography, and MRI. In the case of MRI, although it has the disadvantage of being expensive, it offers higher image quality for soft tissues and is superior in terms of anatomic location. For this reason, MRI has been used in a small number of studies, as in the present study.8,13,17 In this study, none of the muscles at the lower margin of the L3 vertebra showed any statistically significant difference between the two groups. These findings suggest that most of the lumbar spinal movements and weight bearing occur at the lower lumbar level. In the women in this study, values measured at the L3 and L5 levels did not differ significantly between the two groups (P 9 0.05). This may be because of the small sample size in the female CLBP group. Further study of the causes of CLBP in women is necessary. In this study, the sensitivity and the specificity for predicting CLBP after trauma were 83.3% and 64.3% for the L5 erector spinae muscle and 94.4% and 42.9% for the L5 multifidus muscle, respectively. In addition, the combination of two variables increased the sensitivity to 100%. The authors believe that these values are high enough for use in clinical practice despite the diverse causes of LBP. There were some limitations in this study. Although many patients had had a lumbar MRI in the authors’ rehabilitation department, all of those with existing lumbar lesions on MRI were excluded to eliminate the influence of such lesions. As a result, large numbers of patients with LBP were excluded because of lumbar lesions. The authors conducted www.ajpmr.com
an interview about the duration of LBP, which may have introduced a memory bias. However, interviews were conducted twice during the study, the interval between 6 mos after trauma, and interview time might be shorter than expected. Finally, this retrospective study was not in control of the magnitude of the accident. Although the accidents of all subjects were not severe and all subjects were capable of independent outdoor gait and activities of daily living, that does not necessarily mean that magnitudes of the accidents in all subjects were absolutely equal. Therefore, in a future prospective study, controlling for the magnitude of the accident will be important.
CONCLUSIONS The CSA of the multifidus and erector spinae muscles at the lower lumbar level can be considered as prognostic factors for the chronicity of LBP in men. The authors thus suggest that evaluation of the CSA of these muscles using MRI would be helpful for further evaluation and planning the treatment of acute LBP. In women, other factors should be considered for predicting the chronicity of acute LBP. REFERENCES 1. Waddell G: Volvo award in clinical sciences. A new clinical model for the treatment of low-back pain. Spine (Phila Pa 1976) 1987;12:632Y44 2. Andersson GB: Epidemiological features of chronic low-back pain. Lancet 1999;354:581Y5 3. Kovacs FM, Seco J, Royuela A, et al: Predicting the evolution of low back pain patients in routine clinical practice: Results from a registry within the Spanish National Health Service. Spine J 2012;12:1008Y20 4. Croft PR, Macfarlane GJ, Papageorgiou AC, et al: Outcome of low back pain in general practice: A prospective study. BMJ 1998;316:1356Y9 5. O’Sullivan P, Phyty G, Twomey L, et al: Evaluation of specific stabilizing exercise in the treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine 1997;22:2959Y67 6. Hides J, Jull G, Richardson C: Long-term effects of specific stabilizing exercises for first-episode low back pain. Spine 2001;26:E243Y8 7. Franca FR, Burke TN, Hanada ES, et al: Segmental stabilization and muscular strengthening in chronic low back pain: A comparative study. Clinics (Sao Paulo) 2010;65:1013Y7 8. Kader D, Wardlaw D, Smith F: Correlation between the MRI changes in the lumbar multifidus muscles and leg pain. Clin Radiol 2000;55:145Y9 9. Danneels L, Vanderstraeten G, Cambier D, et al: CT imaging of trunk muscles in chronic low back pain
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
129
patients and healthy control subjects. Eur Spine J 2000;9:266Y72 10. Hides J, Gilmore C, Stanton W, et al: Multifidus size and symmetry among chronic LBP and healthy asymptomatic subjects. Man Ther 2008;13:43Y9
130
14. Crossley KM, Bennell KL, Cowan SM, et al: Analysis of outcome measures for persons with patellofemoral pain: Which are reliable and valid? Arch Phys Med Rehabil 2004;85:815Y22
11. Wallwork T, Stanton W, Freke M, et al: The effect of chronic low back pain on size and contraction of the lumbar multifidus muscle. Man Ther 2008
15. Hides J, Stokes M, Saide M, et al: Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back pain. Spine 1994;19:165Y72
12. Lee HJ, Lim WH, Park JW, et al: The relationship between cross sectional area and strength of back muscles in patients with chronic low back pain. Ann Rehabil Med 2012;36:173Y81
16. Barker K, Shamley D, Jackson D: Changes in the cross-sectional area of multifidus and psoas in patients with unilateral back pain: the relationship to pain and disability. Spine 2004;29:E515Y9
13. Parkkola R, Rytokoski U, Kormano M: Magnetic resonance imaging of the discs and trunk muscles in patients with chronic low back pain and healthy control subjects. Spine (Phila Pa 1976) 1993;18:830Y6
17. Dangaria TR, Naesh O: Changes in cross-sectional area of psoas major muscle in unilateral sciatica caused by disc herniation. Spine (Phila Pa 1976) 1998;23:928Y31
Lee et al.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Low-Back Pain
Affiliations: From the Department of Rehabilitation Medicine, CHA Bundang Medical Center, CHA University, Gyeonggi-do, Republic of Korea. The new affiliation for Dr. Ryu is Department of Rehabilitation Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
Correspondence: All correspondence and requests for reprints should be addressed to: Ju Seok Ryu, MD, PhD, Department of Rehabilitation Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 82 Gumi-ro 173 beon-gil Bundang-gu, Seongnam, 463-707, Korea.
Disclosures: No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. No funds were received in support of this work. This study was not presented in any form. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/15/9402-0123 American Journal of Physical Medicine & Rehabilitation Copyright * 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000149
ORIGINAL RESEARCH ARTICLE
Sex Differences in Predicting Chronicity of Low-Back Pain After Acute Trauma Using Lumbar Muscle Area ABSTRACT Lee HI, Lee ST, Kim MY, Ryu JS: Sex differences in predicting chronicity of lowback pain after acute trauma using lumbar muscle area. Am J Phys Med Rehabil 2015;94:123Y130.
Objective: The aim of this study was to investigate sex differences in predicting chronicity of low-back pain after acute trauma using cross-sectional areas of paraspinal (multifidus and erector spinae) and psoas muscles. Design: Between January 2006 and December 2010, a total of 54 patients were interviewed at least 6 mos after the trauma event. The subjects were classified into chronic low-back pain group and improved low-back pain group according to the presence of low-back pain for more than 6 mos. The crosssectional area of the multifidus, erector spinae, and psoas muscles was measured at the level of the lower margin of the L3 and L5 vertebrae using magnetic resonance imaging.
Results: The cross-sectional area of the multifidus and erector spinae muscles at L5 in the chronic low-back pain group was significantly smaller than that of the improved low-back pain group (P G 0.05) in the men. There were no significant differences in the other parameters between the groups in the men. There were no significant differences in any parameters in the women.
Conclusions: In the men, the cross-sectional area of the multifidus and erector spinae muscles at the lower lumbar level can be considered to be prognostic factors for the chronic low-back pain after acute trauma. The authors thus suggest that strengthening of lumbar paraspinal muscles could be helpful for preventing chronicity of low-back pain. Key Words: Muscles
www.ajpmr.com
Low-Back Pain, Magnetic Resonance Imaging, Cross-Sectional Area,
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
123
L
MATERIALS AND METHODS
ow-back pain (LBP) is one of the most common diseases, with approximately 80% of the adult population experiencing it at least one or more times in their life time.1 Most patients experiencing acute LBP usually recover within 6Y12 wks. However, a large portion of them experience symptom recurrence, with some of them developing chronic LBP (CLBP).1,2 In a large prospective study including 4261 patients, 21.4% showed CLBP at discharge and 26.5% showed clinical disability.3 Factors predicting a clinically relevant improvement in LBP at 3 mos were clinical features at baseline (pain being acute, as opposed to subacute or chronic; higher severity of LBP; lower severity of leg pain and disability) and treatments received (not having undergone lumbar surgery and having been treated with neuroreflexotherapy).3 LBP restricts functional and occupational activities and is detrimental to society and the economy. Thus, appropriate treatment is important.1,2,4 It is generally thought that muscular weakness is linked to LBP, even though the main direction of this link is unclear. Several exercise protocols emphasize lumbar stabilization and core strengthening,5Y7 with a particular focus on the multifidus muscle. The multifidus muscle is attached to the spine at every one to two segments to provide stability and is known to be sensitive to pathologic change. Lumbar stabilization exercises for the multifidus muscle are known to improve LBP and reduce its rate of recurrence.5Y7 To date, there have been several studies of lumbar muscle changes as an index of functional disability in patients with LBP. These studies have reported lumbar muscle atrophy in CLBP patients.8Y13 However, few reports have evaluated the association between the chronicity of acute LBP and the cross-sectional area (CSA) of lumbar muscles. Preliminary data were reported regarding the association between the chronicity of acute LBP and the CSA of lumbar muscles,12 but given the small sample size, the authors were unable to evaluate differences regarding sex and were unable to verify multifidus muscle CSA as a risk factor of CLBP. Therefore, the first aim of the current study was to investigate the influence of the CSA of the paraspinal (multifidus and erector spinae) and psoas muscles and to investigate the predictive values of each muscle on the chronicity of LBP after acute trauma. The second aim was to investigate sex differences in predicting the prognosis of LBP using the CSA of the paraspinal muscles.
124
Lee et al.
Subjects This study was a retrospective cohort study of patients who visited the authors’ teaching hospital for acute LBP and underwent lumbar magnetic resonance imaging (MRI). Between January 2006 and December 2010, a total of 1001 patients (477 men and 524 women) were enrolled in this study’s cohort. Inclusion criteria were as follows: (1) patients who complained of LBP after trauma including in-car accident, car-pedestrian accident, and sport injury; (2) patients who could ambulate and perform activities of daily living and be treated as an outpatient by themselves; (3) age between 20 and 40 yrs; (4) no definite history of LBP; (5) selfreported pain levels of more than 3 on the visual analog scale (VAS; 0~10); (6) MRI performed within 1 mo from the first appearance of symptoms; (7) patients who were treated with oral medication and/ or physical modality and/or back exercise and/or trigger point injection; and (8) no abnormal findings (disk herniation, disk bulging, spinal stenosis, spondylolysis, spondylolisthesis, scoliosis, facet arthritis, spinal fracture, disk degeneration, etc.) on lumbar MRI and normal official radiology report. Thirty-nine men and 35 women satisfied the inclusion criteria. The authors initially evaluated the VAS and presence of radicular symptoms in the lower extremities. The VAS is an easy-to-use evaluation tool for chronic pain and has been used in a wide range of clinical and research settings, with known reliability and validity.14 The therapies received (medication, physical modality, exercise therapy, and trigger point injection) were also reviewed. The authors conducted an interview for persistence of LBP at least 6 mos later. Seven men and 11 women who refused the interview or who changed their postal address or telephone numbers were excluded from the study. A total of 56 subjects (32 men, mean [SD] age, 30.0 [4.5] yrs, and 24 women, mean [SD] age, 29.0 [5.7] yrs) participated in the study. The etiologies of trauma in these 56 patients were in-car accidents (n = 52), car-pedestrian accidents (n = 3), and sport injury (n = 1). The major pathologies of trauma were minor low-back strains and sprains. The subjects were divided into two groups according to the duration of their LBP, namely, a CLBP group and an improved LBP (ILBP) group. The CLBP group was defined as patients who experienced LBP for more than 6 mos, and the ILBP group was defined as patients who showed ILBP within 6 mos.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
FIGURE 1 The CSA of the paraspinal and psoas muscles (B) obtained on axial T2-weighted images at the lower margin of the L3 and L5 vertebrae (A) using the Marosis m-view version 5.4 program. ES indicates erector spinae; Mu, multifidus.
All patients gave informed consent for their clinical details and scans to be used in this study, and the study protocol was approved by the institutional review board of the hospital.
Methods The duration of LBP, height, and body weight were recorded during the interviews. The CSA of the paraspinal muscles (multifidus and erector spinae) and the psoas muscles was obtained from axial T2-weighted images at the lower margin of the L3 and L5 vertebrae using the Marosis m-view version 5.4 program (Fig. 1).12 This image is superior in distinguishing muscle from fat. The authors measured only muscle area excluding fat tissues. The CSA of the multifidus and erector spinae muscles in the paraspinal muscles and the psoas muscles was measured separately on each side. The proportions of the bilateral L5 multifidus and erector spinae muscles from the summation of bilateral erector spinae, multifidus, and psoas muscles were calculated.
The authors evaluated the differences in the CSA and the proportions of these muscles between the CLBP and ILBP groups in each sex. Body weight (kilograms) was divided by the square of height (meters) to calculate the body mass index.
Statistics Statistical analysis was performed using the Statistical Package for the Social Sciences 19.0. The Mann-Whitney U test and the W2 test were used to compare the differences between the two groups. The value that maximized the area under the receiver operating characteristic curve was chosen as a cutoff point for sensitivity and specificity and was used to predict the chronicity of LBP. Statistical significance was considered at P G 0.05. All data were presented as mean (standard deviation).
RESULTS The demographic data are shown in Table 1. The age, height, weight, and body mass index did
TABLE 1 Demographic data of subjects
Male
Age, yrs Height, m Weight, kg BMI, kg/m2
Female
Age, yrs Height, m Weight, kg BMI, kg/m2
ILBP Group (n = 18)
CLBP Group (n = 14)
P
31.28 (4.52) 1.76 (0.05) 72.56 (9.39) 24.37 (2.68) ILBP group (n = 17) 28.35 (5.44) 1.62 (0.05) 54.47 (7.40) 20.30 (2.24)
28.35 (4.01) 1.76 (0.06) 72.21 (8.71) 24.31 (2.87) CLBP group (n = 7) 30.57 (6.62) 1.64 (0.04) 53.85 (4.29) 19.66 (2.13)
0.11 0.87 0.59 0.72 0.34 0.38 0.95 0.66
Values are mean (standard deviation). a P G 0.05. BMI, body mass index.
www.ajpmr.com
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
125
TABLE 2 Clinical data of subjects
VASa Presence of radicular symptoms, % Methods of therapy
Medications Physical modalities Exercise therapy Trigger point injection
Total (n = 56)
ILBP Group (n = 35)
CLBP Group (n = 21)
P
5.71 (1.75) 42.1 86.8 92.1 31.6 34.2
5.24 (1.64) 32.0 80.0 88.0 28.0 32.0
6.62 (1.67) 61.5 100.0 100.0 38.5 38.5
0.033 0.080 0.084 0.193 0.510 0.690
Values are mean (standard deviation) or percentage. a P G 0.05.
not differ significantly between the two groups in either sex (Table 1). The intervals between acute trauma and MRI examination were 12.5 (8.1) days in the men and 11.9 (8.8) days in the women. The initial mean (SD) VAS score in all included patients was 5.71 (1.75). The mean (SD) VAS scores were 5.24 (1.64) and 6.62 (1.67) in the ILBP and CLBP groups, respectively (P = 0.033, Table 2). Some 32.0% and 61.5% showed radicular symptoms in the ILBP and CLBP groups, respectively (P = 0.080, Table 2). The therapies received are described in Table 2. The rates of therapies received (medications, physical modalities, exercise therapy, and trigger point injection) were not significantly different between the two groups (Table 2). In the men, the CSA of the erector spinae muscle at the lower margin of the L5 vertebra in the CLBP group (right, 8.5 [2.4] cm2; left, 8.8 [2.7] cm2) was significantly smaller than that of the
ILBP group (right, 11.2 [3.6] cm2; left, 11.9 [3.5] cm2; P G 0.05; Table 3). The multifidus muscle at the lower margin of the L5 vertebra in the CLBP group (right, 11.0 [1.8] cm2, left, 10.9 [1.8] cm2) was also significantly smaller than that of the ILBP group (right, 12.5 [1.7] cm2; left, 12.5 [2.0] cm2; P G 0.05; Table 3). However, the mean CSA of the psoas muscles at the lower margin of the L5 vertebra and the CSA of all muscles measured at the lower margin of the L3 vertebra did not differ significantly between the two groups (Table 3). In the women, there were no differences between parameters measured at the L3 and L5 levels between the groups (P 9 0.05, Table 4). The proportions of each muscle in relation to the lumbar paraspinal (summation of multifidus, erector spinae, and psoas) muscles at the L5 level are shown in Table 5 (men only). The proportion of the erector spinae in the CLBP group was significantly smaller than that in the ILBP group.
TABLE 3 The CSA of the paraspinal and psoas muscles at the L3 and L5 levels in men
L3 level
Multifidus, cm2 Erector spinae, cm2 Psoas, cm2
L5 level
Multifidus, cm2 Erector spinae, cm2 Psoas, cm2
Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral
ILBP Group (n = 18)
CLBP Group (n = 14)
P
7.3 (1.4) 6.8 (1.3) 14.1 (2.6) 21.2 (4.3) 21.8 (3.6) 43.1 (7.7) 13.4 (2.0) 13.3 (2.5) 26.7 (4.2) 12.5 (1.7) 12.5 (2.0) 25.0 (3.6) 11.6 (3.5) 12.4 (3.5) 24.1 (7.0) 18.4 (2.9) 17.8 (3.0) 36.3 (5.7)
7.1 (1.1) 6.8 (1.2) 14.0 (2.3) 19.5 (3.0) 20.3 (3.3) 39.9 (6.2) 13.1 (2.7) 12.8 (2.4) 26.0 (5.1) 11.0 (1.8) 10.9 (1.8) 22.1 (3.6) 8.5 (2.4) 8.8 (2.7) 17.4 (5.1) 18.3 (3.7) 17.8 (3.2) 36.2 (6.7)
0.722 0.955 0.750 0.301 0.442 0.338 0.561 0.587 0.419 0.041a 0.041a 0.030a 0.016a 0.007a 0.008a 0.639 0.866 0.722
Values are mean (standard deviation). a P G 0.05.
126
Lee et al.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
TABLE 4 The CSA of the paraspinal and psoas muscles at the L3 and L5 levels in women
Multifidus, cm2
L3
Erector spinae, cm2 Psoas, cm2 Multifidus, cm2
L5
Erector spinae, cm2 Psoas, cm2
ILBP Group (n = 18)
CLBP Group (n = 14)
P
5.7 (1.1) 5.2 (1.0) 11.0 (2.2) 13.0 (2.5) 13.6 (2.5) 26.7 (5.0) 6.9 (1.6) 7.0 (1.1) 14.1 (2.7) 10.5 (1.4) 10.4 (1.5) 21.0 (2.9) 10.7 (3.0) 11.0 (3.1) 21.8 (6.1) 11.0 (1.9) 10.7 (1.2) 21.8 (2.9)
5.9 (0.9) 5.8 (1.1) 11.9 (2.0) 13.3 (1.7) 13.7 (2.1) 27.0 (3.7) 7.6 (2.3) 7.5 (1.4) 15.2 (3.1) 10.0 (1.4) 10.2 (1.2) 20.3 (2.6) 8.8 (2.3) 8.8 (2.0) 17.7 (4.3) 10.7 (2.3) 10.5 (2.5) 21.3 (4.8)
0.710 0.209 0.455 0.852 0.901 1.000 0.455 0.576 0.576 0.494 0.951 0.710 0.147 0.147 0.130 0.757 0.664 0.804
Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral
Values are mean (standard deviation). a P G 0.05.
In the men, the CSA of the bilateral L5 erector spinae muscles had a sensitivity of 83.3% and a specificity of 64.3% at a cutoff value of 1915.8 cm2 (Fig. 2A), and the CSA of the bilateral L5 multifidus muscle had a sensitivity of 94.4% and a specificity of 42.9% at a cutoff value of 2085.2 cm2 for predicting the chronicity of LBP (Fig. 2B). In the men, the proportion of the bilateral L5 erector spinae muscles from the summation of the bilateral erector spinae, multifidus, and psoas muscles had a sensitivity of 94.4% and a specificity of 50.0% at a cutoff value of 0.22, and the CSA of the bilateral L5 multifidus muscle from the summation of bilateral erector spinae, multifidus, and
psoas muscles had a sensitivity of 72.2% and a specificity of 42.9% at a cutoff value of 0.3 for prediction of chronicity of LBP. To increase the sensitivity for prediction of chronicity of LBP, the two significant variables (the area of the multifidus and erector spinae muscles) were combined. The combination of two variables increased the sensitivity to 100% but decreased the specificity to 35.7% (Fig. 2C).
DISCUSSION In the authors’ preliminary study, only the erector spinae was significantly smaller in the CLBP
TABLE 5 The proportion of each muscle to lumbar muscles at the L5 level
Men
Multifidus, % Erector spinae, %
Women
Multifidus, % Erector spinae, %
Right Left Bilateral Right Left Bilateral Right Left Bilateral Right Left Bilateral
ILBP Group (n = 18)
CLBP Group (n = 14)
P
0.30 (0.05) 0.29 (0.04) 0.30 (0.05) 0.27 (0.05) 0.29 (0.05) 0.28 (0.05) ILBP group (n = 17) 0.33 (0.03) 0.33 (0.03) 0.33 (0.03) 0.33 (0.05) 0.34 (0.05) 0.33 (0.05)
0.29 (0.03) 0.29 (0.03) 0.29 (0.03) 0.23 (0.05) 0.23 (0.05) 0.23 (0.05) CLBP group (n = 7) 0.34 (0.04) 0.35 (0.04) 0.35 (0.04) 0.29 (0.05) 0.30 (0.06) 0.30 (0.05)
0.985 0.896 0.750 0.027a 0.004a 0.014a 0.260 0.075 0.114 0.234 0.087 0.187
Proportion means each muscle divided by the sum of the multifidus, erector spinae, and psoas muscles; values are mean (standard deviation). a P G 0.05.
www.ajpmr.com
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
127
FIGURE 2 The CSA of the bilateral erector spinae muscle had a sensitivity of 83.3% and a specificity of 64.3% at a cutoff value of 1915.8 cm2 for predicting the chronicity of LBP (A), and the CSA of the bilateral multifidus muscle had a sensitivity of 94.4% and a specificity of 42.9% at a cutoff value of 2085.2 cm2 (B). The combination of two variables increased the sensitivity to 100% but decreased the specificity to 35.7% (C).
group than in the ILBP group, and the multifidus did not differ significantly between the two groups.12 However, this study was unable to consider men and women separately because of the small sample size. The authors thus extended this study to enroll more patients, with the aim of determining sex differences and the importance of the multifidus as well as the erector spinae muscles. In the present study, the CSA of the multifidus and erector spinae muscles in the men measured at the lower margin of the L5 vertebra was significantly smaller in the CLBP group than in the ILBP group. The present study excluded all patients who had a history of LBP and those who had MRIdocumented lumbar lesions. Thus, these results show that small paravertebral muscles at the low lumbar level in early stages after trauma could predict the persistence of LBP. Many previous studies have shown localized or generalized multifidus muscle atrophy in patients with CLBP.8,10,15,16 Most of these studies, however, included patients who had had CLBP for more than 3 mos8,16 and evaluated the correlation of muscular atrophy with leg pain or nerve root compression.8,16 These findings suggest that multifidus muscle atrophy in patients with CLBP can be associated with lumbar lesions, such as lumbar herniated intervertebral disks, which could irritate the nerve roots, and long duration of back pain. In addition, until now, there has been no study evaluating the size of the erector spinae muscle in patients with CLBP. However, in the present study, MRI was conducted at an early stage of trauma, and thus, the observed atrophy cannot be attributed to disuse. The intervals between acute trauma and MRI
128
Lee et al.
examination were 12.5 (8.1) days in men and 11.9 (8.8) days in women. The present study excluded all patients who had lumbar lesions, including disk bulging, on MRI, to eliminate the influence of lesions on muscle atrophy. Thus, other explanations for the small CSA of the multifidus and erector muscles are required. This exclusion was extended to the investigation of the correlation between the chronicity of adult patients without a history of LBP from acute LBP to chronic pain and the CSA of lumbar muscles on MRI. This study followed up patients who had a lumbar MRI at an early stage of LBP and divided them into two groups according to the persistence of LBP, comparing the CSA of the lumbar muscles between the two groups. Thus, the implications of this study could be regarded as being different from those of previous studies. The results of this study enabled the authors to rule out disuse atrophy and root irritation as possible influences on low lumbar muscular atrophy. Therefore, the authors speculate that patients with small muscle area in the lower lumbar region before trauma are prone to develop CLBP, and therefore, muscle area is important for preventing LBP. Although there may be many possible reasons for acute LBP, most cases are thought to develop after sudden and unexpected posture change or loading on the lumbar spine. If lumbar muscles fail to properly react to such sudden loading, the bending momentum and trunk movement may be greater; this may increase the risk for tissue damage. In such cases, the multifidus and erector spinae muscles play an important role in maintaining posture and balance by stabilizing the lumbar spine.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Therefore, it seems that, for those who have a small CSA of the multifidus and erector spinae muscles, the risk for developing CLBP could be higher. Because the authors evaluated only the size of the lumbar muscles, further study regarding the quality of the lumbar muscles is necessary. The VAS scores were significantly different between the ILBP and CLBP groups (P = 0.033). Because small paravertebral muscles cannot be attributed to disuse, weak lumbar muscles (small CSA) are assumed to cause high VAS scores in the CLBP group. Further work to evaluate the correlation between muscular area, strength, and high VAS scores is required. Because the therapies received (medication, physical modalities, exercise therapy, and trigger point injection) were not significantly different between the two groups, it seems that these variables did not influence the chronicity of LBP. The atrophy of the paraspinal muscles can be evaluated using ultrasound, computed tomography, and MRI. In the case of MRI, although it has the disadvantage of being expensive, it offers higher image quality for soft tissues and is superior in terms of anatomic location. For this reason, MRI has been used in a small number of studies, as in the present study.8,13,17 In this study, none of the muscles at the lower margin of the L3 vertebra showed any statistically significant difference between the two groups. These findings suggest that most of the lumbar spinal movements and weight bearing occur at the lower lumbar level. In the women in this study, values measured at the L3 and L5 levels did not differ significantly between the two groups (P 9 0.05). This may be because of the small sample size in the female CLBP group. Further study of the causes of CLBP in women is necessary. In this study, the sensitivity and the specificity for predicting CLBP after trauma were 83.3% and 64.3% for the L5 erector spinae muscle and 94.4% and 42.9% for the L5 multifidus muscle, respectively. In addition, the combination of two variables increased the sensitivity to 100%. The authors believe that these values are high enough for use in clinical practice despite the diverse causes of LBP. There were some limitations in this study. Although many patients had had a lumbar MRI in the authors’ rehabilitation department, all of those with existing lumbar lesions on MRI were excluded to eliminate the influence of such lesions. As a result, large numbers of patients with LBP were excluded because of lumbar lesions. The authors conducted www.ajpmr.com
an interview about the duration of LBP, which may have introduced a memory bias. However, interviews were conducted twice during the study, the interval between 6 mos after trauma, and interview time might be shorter than expected. Finally, this retrospective study was not in control of the magnitude of the accident. Although the accidents of all subjects were not severe and all subjects were capable of independent outdoor gait and activities of daily living, that does not necessarily mean that magnitudes of the accidents in all subjects were absolutely equal. Therefore, in a future prospective study, controlling for the magnitude of the accident will be important.
CONCLUSIONS The CSA of the multifidus and erector spinae muscles at the lower lumbar level can be considered as prognostic factors for the chronicity of LBP in men. The authors thus suggest that evaluation of the CSA of these muscles using MRI would be helpful for further evaluation and planning the treatment of acute LBP. In women, other factors should be considered for predicting the chronicity of acute LBP. REFERENCES 1. Waddell G: Volvo award in clinical sciences. A new clinical model for the treatment of low-back pain. Spine (Phila Pa 1976) 1987;12:632Y44 2. Andersson GB: Epidemiological features of chronic low-back pain. Lancet 1999;354:581Y5 3. Kovacs FM, Seco J, Royuela A, et al: Predicting the evolution of low back pain patients in routine clinical practice: Results from a registry within the Spanish National Health Service. Spine J 2012;12:1008Y20 4. Croft PR, Macfarlane GJ, Papageorgiou AC, et al: Outcome of low back pain in general practice: A prospective study. BMJ 1998;316:1356Y9 5. O’Sullivan P, Phyty G, Twomey L, et al: Evaluation of specific stabilizing exercise in the treatment of chronic low back pain with radiologic diagnosis of spondylolysis or spondylolisthesis. Spine 1997;22:2959Y67 6. Hides J, Jull G, Richardson C: Long-term effects of specific stabilizing exercises for first-episode low back pain. Spine 2001;26:E243Y8 7. Franca FR, Burke TN, Hanada ES, et al: Segmental stabilization and muscular strengthening in chronic low back pain: A comparative study. Clinics (Sao Paulo) 2010;65:1013Y7 8. Kader D, Wardlaw D, Smith F: Correlation between the MRI changes in the lumbar multifidus muscles and leg pain. Clin Radiol 2000;55:145Y9 9. Danneels L, Vanderstraeten G, Cambier D, et al: CT imaging of trunk muscles in chronic low back pain
Chronicity of Low-Back Pain After Acute Trauma Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
129
patients and healthy control subjects. Eur Spine J 2000;9:266Y72 10. Hides J, Gilmore C, Stanton W, et al: Multifidus size and symmetry among chronic LBP and healthy asymptomatic subjects. Man Ther 2008;13:43Y9
130
14. Crossley KM, Bennell KL, Cowan SM, et al: Analysis of outcome measures for persons with patellofemoral pain: Which are reliable and valid? Arch Phys Med Rehabil 2004;85:815Y22
11. Wallwork T, Stanton W, Freke M, et al: The effect of chronic low back pain on size and contraction of the lumbar multifidus muscle. Man Ther 2008
15. Hides J, Stokes M, Saide M, et al: Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back pain. Spine 1994;19:165Y72
12. Lee HJ, Lim WH, Park JW, et al: The relationship between cross sectional area and strength of back muscles in patients with chronic low back pain. Ann Rehabil Med 2012;36:173Y81
16. Barker K, Shamley D, Jackson D: Changes in the cross-sectional area of multifidus and psoas in patients with unilateral back pain: the relationship to pain and disability. Spine 2004;29:E515Y9
13. Parkkola R, Rytokoski U, Kormano M: Magnetic resonance imaging of the discs and trunk muscles in patients with chronic low back pain and healthy control subjects. Spine (Phila Pa 1976) 1993;18:830Y6
17. Dangaria TR, Naesh O: Changes in cross-sectional area of psoas major muscle in unilateral sciatica caused by disc herniation. Spine (Phila Pa 1976) 1998;23:928Y31
Lee et al.
Am. J. Phys. Med. Rehabil. & Vol. 94, No. 2, February 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
