SPINE Volume 40, Number 8, pp 550-559 ©2015, Wolters Kluwer Health, Inc. All rights reserved.
DIAGNOSTICS
Characteristics of Trunk Control During Crook-Lying Unilateral Leg Raising in Different Types of Chronic Low Back Pain Patients Atsushi Ohe, PT, MS,*† Teiji Kimura, PT, PhD,‡ Ah-Cheng Goh, PT, PhD,§ Akemi Oba, PT,¶ Jun Takahashi, MD, PhD, and Yuji Mogami, MD**
Study Design. Cross-sectional observational study. Objective. To quantitatively clarify the characteristics of trunk control during unilateral leg-raising movement in different types of nonspecific chronic low back pain (NS-CLBP) patients who were identified by aggravation of symptoms during trunk movement. Summary of Background Data. Although there is a need to classify NS-CLBP patients for clinical decision making in physical therapy, the characteristics of trunk control during unilateral legraising movement in different types of NS-CLBP patients have not been quantitatively analyzed in previous studies by simultaneously measuring the lumbar spine movement, trunk muscle activity, and leg movement. Methods. Thirty NS-CLBP patients, of whom 13 were aggravated by trunk flexion (flexion group) and 17 were aggravated by trunk extension (extension group), and 30 healthy controls performed crook-lying unilateral leg-raising movement on the painful side in patient group and the dominant leg in controls. During the unilateral leg-raising movement, pressure changes produced by the movement of the lumbar lordotic curve, measured by a custom-made recording device, were used as indices of the lumbar spine movement. Trunk muscle activities were recorded by surface electromyography and
From the *Department of Rehabilitation, Tachiiri Orthopedic Clinic, Kyoto, Japan; †Department of Health Sciences, Graduate School of Medicine, Shinshu University, Nagano, Japan; ‡Department of Physical Therapy, School of Health Sciences, Shinshu University, Nagano, Japan; §Department of Physical Therapy, School of Health Sciences, Shinshu University, Nagano, Japan; ¶Department of Rehabilitation, Azumi General Hospital, Nagano, Japan; Department of Orthopaedic Surgery, Shinshu University, School of Medicine, Nagano, Japan; and **Department of Orthopedics, Azumi General Hospital, Nagano, Japan. Acknowledgment date: July 1, 2014. Revision date: November 18, 2014. Acceptance date: February 3, 2015. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Teiji Kimura, PT, PhD, Department of Physical Therapy, School of Health Sciences, Shinshu University, 3-1-1, Matsumoto, Nagano 390-8621, Japan; E-mail: tkimura@ shinshu-u.ac.jp DOI: 10.1097/BRS.0000000000000828
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diagnostic ultrasonography. The pressure changes and trunk muscle activities were statistically compared among the 3 groups. Results. At foot-off during unilateral leg-raising movement, the extension group demonstrated increase in pressure changes, whereas the flexion group and controls demonstrated decrease in pressure changes. Bilateral external obliques muscle activities in the extension group were significantly larger than those in the flexion group and controls (P < 0.05). Conclusion. This study demonstrated that the characteristics of trunk control during unilateral leg-raising movement were different depending on the types of NS-CLBP patients. These results indicate that patients with NS-CLBP might select compensatory trunk control strategies subconsciously to prevent the manifestation of LBP. These results also suggest the importance of the different characteristics of trunk control during active limb movement in the clinical reasoning process for the management of different types of NS-CLBP patients. Key words: low back pain, classification, motor control, leg raising, trunk movement, diagnostic ultrasonography, electromyography. Level of Evidence: N/A Spine 2015;40:550–559
I
t has been reported that more than 80% of low back pain (LBP) patients had no radiological abnormality evident and consequently were being diagnosed as nonspecific chronic LBP (NS-CLBP) patients.1–3 Because the characteristics of NSCLBP patients vary widely, there is a need to classify NS-CLBP patients into subgroups in order to identify the most effective treatments for the different types of NS-LBP patients.4–11 One such classification system is based on the mechanical stress imposed on the spine in NS-CLBP patients. This classification system can be divided into 2 main methods: mechanical stress imposed on the spine because of (i) direct movement of trunk4–6,10,11 or (ii) indirect movement of trunk from associated limb movement.7–9 With regard to the direct movement method described by Hall et al,4–6,10 NS-CLBP patients can be classified into a flexion group (FG) and an extension group (EG) on the basis of the direction of the trunk movement, which aggravates the symptoms. On the contrary, the indirect movement method is based on repetitive active limb movement during daily activities,
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DIAGNOSTICS which causes indirect movement of the trunk that can contribute to the patient’s LBP.7–9 Previous studies had reported the variety of indirect trunk movement during active limb movement in patients with chronic LBP.12 Sahrmann8 emphasized the importance of evaluation and treatment based on a classification of the characteristics of movement pattern of the trunk during active limb movement. Regarding the relationship between direct and indirect movement classification methods, it was thought that the type of LBP manifestation identified by the direct movement method might affect the movement pattern of the trunk during active limb movement so as to avoid the trunk movement in the direction that aggravates the LBP. However, the characteristics of movement pattern of the trunk during active limb movement in different types of LBP manifestations have not been reported in previous studies. Furthermore, it is thought that these different movement patterns of the trunk during active limb movement may be affected by the combined activities of both the superficial and deep trunk flexor and extensor muscles. However, the quantitative analysis of trunk control during active limb movement noninvasively by simultaneously measuring the lumbar spine movement and trunk muscle activities has also not been reported in previous studies. Our hypotheses were as follows: When healthy subjects in the control group (CG) raised the dominant leg in crook-lying unilateral leg raising, which was recommended as a suitable task to assess the lumbar spine movement,7,13–15 CG would demonstrate lumbar spine movement in the direction of the extension (i.e., anterior pelvic tilt) at foot-off because it was thought that unilateral leg-raising movement generated a torque on the pelvis and the lumbar spine in the direction of anterior pelvic tilt and the extension of lumbar spine movement.16 However, when NS-CLBP patients raised the leg on painful side, patients would demonstrate a different trunk control pattern that depended on the different types of LBP manifestation identified by direct trunk movement in NSCLBP patient. In other words, these patients would favor a trunk control pattern in the direction opposite to that which produced the pain during direct trunk movement. An understanding of these different movement patterns of the trunk in different types of LBP manifestations, identified by the direct movement method, could help the interpretation of motor control in NS-CLBP patients and could provide useful guidelines for the clinical reasoning process in these types of patients. The purpose of this study was to noninvasively and quantitatively clarify the characteristics of the trunk control during active limb movement in NS-CLBP patients with different types of LBP manifestation based on direct mechanical stress to the lumbar spine.
MATERIALS AND METHODS Subjects The NS-CLBP patients were recruited from the outpatient departments of local hospitals. The inclusion criteria for Spine
Trunk Control Low Back Pain • Ohe et al
the study were chronic LBP patients without neurological symptoms for at least 3 months, and severity of the pain was serious enough to require medical attention. The exclusion criteria for the study were patients with acute pain within the last 3 months, with the presence of structural deformity, inflammatory disease, nonmechanical LBP, or any other corresponding disorders preventing active rehabilitation. Healthy subjects who had no history of LBP requiring medical attention or resulting in absence from work within the last 10 years were recruited as controls from the hospital staff. The ethics committee of Shinshu University, School of Medicine approved this study. All subjects provided written informed consent.
Demographic Data All patients were evaluated before the first intervention. Height and body weight were measured for all subjects. Patients completed an additional questionnaire regarding their area of pain by using a body chart, the severity of pain by using a 100-mm visual analogue scale,17,18 and disability level by using modified Oswestry Low Back Pain Disability Questionnaire.19 Furthermore, patients were classified into an FG or an EG on the basis of the particular movement (trunk flexion or extension in standing) that aggravated their symptoms according to the Low Back Pain Classification System.4–6,10 The demographic data of subjects are listed in Table 1. One-way analysis of variance for age, body weight, height, and body mass index showed no significant difference among the 3 groups. Independent t test for visual analogue scale and Mann-Whitney U test for modified Oswestry Low Back Pain Disability Questionnaire showed no significant difference between FG and EG.
Task of Active Limb Movement The subjects were positioned in crook lying. The examiner instructed the timing of breathing and gave cues at the end of expiration. The subjects flexed their unilateral hip joint from 60° to 90°, which was regulated by a sponge mat for more than 2 seconds according to a timing cue from the examiner (Figure 1). In this study, unilateral leg-raising movement was performed on the painful side in patients with LBP and on the dominant side in the CG. An electronic metronome (ME-110; YAMAHA Corp., Hamamatsu-shi, Shizuoka, Japan) was used for the regulation of the speed in unilateral leg-raising movement.
Instrumentation During unilateral leg-raising movement, the back pressure that was the pressure between the surface of the low back and the bed was recorded with a custom-made back pressure– recording device; the trunk muscle activities of rectus abdominis (RA), external obliques (EO), multifidus (MF), and erector spinae (ES) muscles were recorded by using surface electromyography (sEMG); and the trunk muscle activities of transverse abdominis and internal obliques were recorded by using ultrasonography (US). www.spinejournal.com
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DIAGNOSTICS
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TABLE 1. Demographic Data* Controls (n = 30, M = 14, F = 16 ) FG (n = 13, M = 6, F = 7) EG (n = 17, M = 7, F = 10) Age, yr
P
33.2 ± 9.0 (22–51)
38.9 ± 9.5 (24–58)
32.6 ± 9.0 (20–53)
0.12
58.3 ± 10.8 (43.4–88.0)
59.0 ± 9.6 (52.2–85.1)
57.7 ± 9.2 (43.9–80.1)
0.87
Height, cm
165.2 ± 7.7 (153.3–180.2)
164.7 ± 7.1 (153.8–176.9)
164.8 ± 7.3 (157.1–183.0)
0.97
BMI, kg/m*
21.2 ± 2.6 (17.2–27.8)
21.7 ± 2.9 (16.8–28.1)
20.9 ± 2.1 (17.2–25.2)
0.68
VAS
N/A
42.2 ± 12.8 (18–58)
34.7 ± 14.4 (18–68)
0.26
Modified ODQ
N/A
11.9 ± 4.3 (4–19)
9.7 ± 4.0 (4–18)
0.15
Body weight, kg
Pain scale
*Values are mean ± SD (range). M indicates male; F, female; FG, flexion group; EG, extension group; BMI, body mass index; VAS, visual analogue scale; N/A, not applicable; ODQ, Oswestry Low Back Pain Disability Questionnaire.
Back Pressure–Recording Device Pressure Biofeedback Unit (PBU; Stabilizer, Chattanooga, CA) has been developed as an indirect method to monitor the lumbopelvic movement in a clinical setting.7,13–15 PBU placed beneath the lumbar spine in supine or crook-lying position can monitor the back pressure changes during lumbar spine movement.7,13–15 An increase in back pressure from baseline would indicate a posterior pelvic tilt with the lumbar spine movement toward the direction of flexion, and a decrease would indicate an anterior pelvic tilt with the lumbar spine movement toward the direction of extension.7 We constructed a custom-made back pressure–recording device that consisted of a PBU, a custom-made air pressure sensor (ME Inc., Nagano, Japan), and
a direct-current amplifier (Digital Indicator F430, UNIPULSE Co. Ltd., Tokyo, Japan) to record the analogue signal of back pressure from the PBU (Figure 2).
Foot Switch To identify the timing of initiation in the unilateral leg-raising movement, a foot switch (ME Inc., Nagano, Japan) (Figure 3) was placed beneath the heel of the designated side. This foot switch was able to output the analogue signal at foot-off.
Surface Electromyography Trunk muscle activities were recorded by using an 8 channel telemetric sEMG system (Tele MyoG2 EM-602; Noraxon
Figure 1. Task of unilateral leg-raising movement and block diagram of the synchronization of the timeline between a biosignal-analyzing software in personal computer and measurement software in ultrasound system by using foot switch signal that was imported to both software. sEMG indicates surface electromyography; ULR, unilateral leg raising.
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DIAGNOSTICS
Figure 2. Custom-made back pressure–recording device (ME, Inc, Nagano, Japan).
USA Inc., Scottsdale, AZ). Bipolar Ag/AgCl surface disposable electrodes (Vitrode L-150X; Nihon Kohden Co. Ltd., Tokyo, Japan) were placed with a center-to-center distance of 3 cm, parallel to the muscle fibers in the center of the muscle belly, over the following muscles bilaterally: RA (3 cm lateral to the umbilicus), EO (15 cm lateral to the umbilicus), MF (2 cm lateral to L4–L5 spinous processes), and ES (3 cm lateral to L3 spinous process).20 The earth electrode was placed on the skin overlying the right anterior superior iliac spine. Skin preparation for sEMG was carried out according to the procedure described by Hermens et al.21
Trunk Control Low Back Pain • Ohe et al
Figure 3. Foot switch (ME, Inc, Nagano, Japan).
Diagnostic Ultrasonography US were recorded with a 5.5-cm, 7-MHz linear head transducer (Cardio & Vascular Ultrasound System Vivid 7, GE Healthcare Japan Inc., Tokyo). To record the time series data of the muscle thickness during unilateral leg raising, motion (M) mode22,23 was used at 96 frames per second (Figure 4). The probe was set in a custom-made pad to minimize variability in the angle and pressure over the target area.23 The probe was placed 2.5 cm anterior to the midpoint between the iliac crest and the costal margin on the midaxillary line.24,25 The probe position and gain were
Figure 4. M mode was used simultaneously with B mode to enable the operator to accurately adjust the position of the M mode beam, which is indicated by a dotted line on the B mode. B-mode image revealed a cross section of TrA and IO. M mode is displayed as a 1-dimensional view of the TrA and IO over time in 4 seconds during unilateral leg-raising movement. IO indicates internal oblique; TrA, transversus abdominis. Spine
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DIAGNOSTICS finely adjusted to ensure optimum clarity because of the differences in the body shape and composition between subjects.
Procedure The air mat of the custom-made back pressure–recording device was placed horizontally under the lumbar spine of the subjects with the lower edge of air cell corresponding to the level of S2.7 The PBU was inflated to 40 mm Hg (baseline pressure).7 Raw sEMG signals are usually normalized with the maximum EMG value obtained from maximum voluntary contraction based on the linear relationship between force-generated and integrated EMG level.26–28 However, it was known that NS-CLBP patients were unable to perform maximum contractions.29,30 Therefore, in this study, the amplitude of sEMG comparable with 5 kgf, which was determined in our pilot study as the comfortable level where the subjects did not feel pain and anxiety, was recorded to estimate relative exerted force in each muscle as a method of normalization in sEMG. Cholewicki et al31 indicated that the problem in using reference point method for normalizing EMG signals in patients with LBP is that patients might demonstrate different recruitment pattern of trunk muscle activities during the normalization task. Hence, we compared raw sEMG data from the 5 kgf task and confirmed that there was no significant difference in each of these muscles among the 3 groups. For each muscle, 5 kgf was established by a handheld dynamometer (HHD; μ-tas F-1; ANIMA Corp, Tokyo, Japan), which was fixed by a belt. Subjects were stabilized to the bed at the chest and the pelvis by a belt for each muscle test. For the RA and the EO, the subjects performed sit-up and oblique sit-up from supine position, respectively, with the hips flexed to 60°, attempting to push the HHD placed on the sternum or on the shoulder. For the MF and the ES, the subjects performed back extension from prone position, attempting to push the HHD placed on the upper thoracic area (between the base of spine of both scapulae). The subjects pushed the HHD gradually until they reached 5 kgf, and held it for 5 seconds. The trials for each muscle were performed twice with a 1-minute rest between trials. Bilateral US of transverse abdominis and internal obliques were measured separately because there was only 1 ultrasound probe available. Subjects practiced unilateral leg-raising movement for 3 times, and data collection was executed 4 times. The order of the laterality of the ultrasound probe during unilateral leg-raising movement was determined by using a random number list. These 4 trials provided 4 repetitive sets of data of back pressure and sEMG and 2 repetitive sets of data of US. Each trial was performed with 30 seconds rest.
Data Analysis Signals from back pressure–recording device, foot switch, and sEMG were A/D converted at a sampling rate of 1500 Hz and analyzed by using a biosignal-analyzing software (MyoResearch XP EM-129M; Noraxon USA, Inc, Scottsdale, AZ). 554
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Raw sEMG signals were band-pass filtered between 20 and 350 Hz and smoothing of the sEMG signals was performed by calculating the root-mean-square (RMS) using 50-ms moving window. RMS of each muscle at foot-off was normalized by using the amplitude of RMS comparable with 5 kgf obtained from the 5 kgf task mentioned in the procedure mentioned previously. The change of thickness for each muscle in US was measured at rest and at foot-off using the measurement software in the ultrasound system on the basis of the muscle fascial boundaries from the M-mode image (Figure 4). The timeline between the biosignal-analyzing software in the personal computer and the measurement software in the ultrasound system was synchronized by using the foot switch signal that was imported to both software (Figure 1). Data analyses were performed for the following parameters: (1) back pressure value (BPV) at foot-off, (2) normalized RMS at foot-off in each RA, EO, MF, and ES (i.e., RMS at foot-off/RMS comparable with 5 kgf/body mass), and (3) muscle contraction ratio at foot-off in each transverse abdominis and internal obliques (i.e., muscle thickness at foot-off/ muscle thickness at rest) (Figure 5).
Figure 5. Diagram of data analysis in sEMG, US, back pressure, and foot switch. sEMG shows normalized RMS. US shows thickness of muscle. Back pressure shows change of pressure. sEMG indicates surface electromyography; US, ultrasonography; BP, back pressure; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; IO, internal oblique; TrA, transversus abdominis; (I), ipsilateral to raised leg; (C), contralateral to raised leg; BPV, back pressure value at foot-off.
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DIAGNOSTICS Statistical Analysis Intraclass correlation coefficients were calculated to confirm the relative reliability of each parameter (4 repetition data of back pressure and sEMG and 2 repetition data of US) during unilateral leg-raising movement. A BlandAltman analysis was used to confirm the absolute reliability and to calculate the limits of agreement of each parameter. A Bland-Altman analysis for all 4 trials is not possible without generating huge amount of unnecessary results. We think that the systematic error from the 4 trials can most likely be attributed to fatigue, habituation, and changes in the skin impedance below the electrodes, with increasing repetitions from the 4 trials. Therefore, we chose the first and the last trials for the Bland-Altman analysis of the EMG and BPV measurements. The differences in BPVs and each trunk muscle activity among the 3 groups were compared by using analysis of variance with a post hoc Tukey honestly significant difference test for parametric analysis and the Kruskal-Wallis test with post hoc Steel-Dwass test for nonparametric analysis. The significance level for all testing was set at 0.05. Statistical analysis was performed with SPSS 18.0 for Windows (SPSS Inc., Chicago, IL) except for Steel-Dwass test because SPSS 18.0 did not support multiple comparison for nonparametric variables. Therefore, Steel-Dwass test was performed with “R” statistical software system 2.8.1 (http://www.r-project.org/).
Trunk Control Low Back Pain • Ohe et al
The trunk muscle activities in US among the 3 groups are shown in Table 5. No significant differences among the 3 groups for all parameters of the trunk muscle activities of US were observed.
DISCUSSION Noninvasive and Quantitative Measurement Method for Trunk Control In this study, we developed a custom-made back pressure– recording device that could provide an analogue signal of back pressure from PBU to quantitatively analyze the trunk control during unilateral leg-raising movement by synchronizing the data between the lumbar spine movement and trunk muscle activities, which were derived from sEMG and ultrasonography. Although some previous studies had used wire electrodes for recording local trunk muscle activity,33–35 these methods were invasive and unsuitable for patients. However, this study used a noninvasive measurement method that combined the sEMG and ultrasonography data. The results of the intraclass correlation coefficients for each parameter (Table 2) demonstrated moderate to almost perfect relative reliability.
TABLE 2. Average Intraclass Correlation
Coefficients (ICC) of Back Pressure (ICC1,4), sEMG (ICC1,4), and US (ICC1,2) for All Subjects When Unilateral Leg Raise Movement Was Performed
RESULTS The relative reliability of all parameters during unilateral leg raising was assessed by intraclass correlation coefficient. In all parameters for the 3 groups, moderate to almost perfect reliability, were found (Table 2).32 The absolute reliability was confirmed by using a Bland-Altman analysis. The results showed that there was no fixed or proportional bias for each parameter. The limits of agreement for each parameter are shown in Table 3. The individual waveforms of back pressure that were averaged data from 4 repetitions of unilateral leg-raising trials are shown in Figure 6. It showed that all subjects demonstrated the back pressure onset preceding foot-off in all groups. The percentage distribution of subjects in each of the 3 groups demonstrating an increase or decrease in back pressure from baseline at foot-off is as follows: for CG, 7 subjects (23%) and 23 subjects (77%) demonstrated an increase and decrease in back pressure, respectively; for FG, 3 patients (23%) and 10 patients (77%) demonstrated an increase and decrease in back pressure, respectively; and for EG, 11 patients (65%) and 6 patients (35%) demonstrated an increase and decrease in back pressure, respectively. Significant difference in BPVs was observed among the 3 groups, whereas BPVs in EG demonstrated an increase and BPVs in FG and controls demonstrated a decrease at footoff (P < 0.01) (Figure 7). The trunk muscle activities in sEMG among the 3 groups are shown in Table 4. Bilateral EO in the EG were significantly larger than those in the FG and controls (P < 0.05). Spine
Controls
FG
EG
0.73
0.79
0.71
RA (I)
0.99
0.91
0.77
RA (C)
0.98
0.96
0.92
EO (I)
0.67
0.77
0.82
EO (C)
0.77
0.66
0.86
MF (I)
0.93
0.65
0.94
MF (C)
0.74
0.87
0.81
ES (I)
0.90
0.86
0.89
ES (C)
0.91
0.85
0.90
TrA (I)
0.63
0.47
0.51
TrA (C)
0.62
0.59
0.58
IO (I)
0.79
0.57
0.61
IO (C)
0.62
0.59
0.73
BP BPV sEMG
US
FG indicates flexion group; EG, extension group; BP, back pressure; BPV, back pressure value at foot-off; sEMG, surface electromyography; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; US, ultrasonography; TrA, transversus abdominis; IO, internal oblique; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
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TABLE 3. Limits of Agreement in Back Pressure, sEMG, and US for All Subjects When Unilateral Leg
Raise Movement Was Performed* Controls
FG
EG
−3.45 to 3.19
−1.10 to 2.56
−1.67 to 2.42
RA (I)
−0.19 × 10−1–0.16 × 10−1
−0.55 × 10−2–0.51 × 10−2
−0.35 × 10−1–0.31 × 10−1
RA (C)
−0.12 × 10−1–0.11 × 10−1
−0.34 × 10−2–0.50 × 10−2
−0.11 × 10−1–0.85 × 10−2
EO (I)
−0.45 × 10−1–0.34 × 10−1
−0.86 × 10−2–0.97 × 10−2
−0.48 × 10−1–0.49 × 10−1
EO (C)
−0.35 × 10−1–0.32 × 10−1
−0.57 × 10−2–0.80 × 10−2
−0.41 × 10−1–0.61 × 10−1
MF (I)
−0.19 × 10−2–0.16 × 10−2
−0.15 × 10−2–0.12 × 10−2
−0.15 × 10−2–0.80 × 10−3
MF (C)
−0.56 × 10−2–0.50 × 10−2
−0.35 × 10−3–0.41 × 10−3
−0.17 × 10−2–0.22 × 10−2
ES (I)
−0.30 × 10−2–0.21 × 10−2
−0.16 × 10−2–0.31 × 10−2
−0.12 × 10−2–0.77 × 10−3
ES (C)
−0.42 × 10−3–0.31 × 10−3
−0.49 × 10−3–0.12 × 10−2
−0.11 × 10−2–0.18 × 10−2
TrA (I)
−0.21 to 0.15
−0.10 to 0.14
−0.10 to 0.17
TrA (C)
−0.17 to 0.14
−0.09 to 0.06
−0.11 to 0.09
IO (I)
−0.09 to 0.07
−0.02 to 0.20
−0.08 to 0.19
IO (C)
−0.09 to 0.09
−0.06 to 0.04
−0.02 to 0.04
BP BPV sEMG
US
*Back pressure and sEMG showed limits of agreement of the data in the first and the fourth of the 4 trials. US data showed limits of agreement of the data of 2 trials. FG indicates flexion group; EG, extension group; BP, back pressure; BPV, back pressure value at foot-off; sEMG, surface electromyography; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; US, ultrasonography; TrA, transversus abdominis; IO, internal oblique; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
Moreover, the results of the Bland-Altman analysis for each parameter demonstrated no systematic bias and small range of limits of agreement (Table 3). Therefore, it could be demonstrated that the measurement system used in this study was feasible. It was also demonstrated that intraindividual variability of lumbar spine movement and trunk muscle activities during unilateral leg-raising movement was comparatively small in all groups.
Implications for Clinical Reasoning and Research Previous studies12 indicated the existence of a variable pattern of trunk movement in NS-CLBP patients during active limb movements. However, the reason for the various patterns was not discussed. We hypothesized that the different trunk control during unilateral leg-raising movement depended on the different types of LBP manifestation that were identified by direct trunk movement in NS-CLBP patient. The results of this study supported our hypothesis. The patients in FG demonstrated the lumbar spine movement toward the direction of extension at foot-off in a similar manner with controls (Figures 6 and 7). It was pointed out that the contraction of hip flexor such as the iliopsoas and the rectus femoris that were protagonistic muscles in unilateral leg raising would generate a torque on the pelvis and the lumbar spine in the 556
direction of anterior pelvic tilt and the extension of lumbar spine movement.16 Furthermore, patients in FG might have no need to avoid the lumbar spine movement toward the direction of extension because it was not associated with the aggravating movement of lumbar spine for FG. On the contrary, patients in EG demonstrated the lumbar spine movement toward the direction of flexion at foot-off (Figures 6 and 7). Moreover, this directional characteristic of lumbar spine movement in EG was supported in the sEMG data, with the bilateral EO showing increased activity (Table 4). The extension of lumbar spine movement could increase stress on posterior structures such as the apophyseal joints.16 Hence, it was thought that the lumbar spine movement organized trunk muscle activity in EG was an example of the self-organized compensatory trunk control strategies to prevent the manifestation of LBP. Although Sahrmann8 proposed that the excessive extension of lumbar spine during unilateral leg flexion was one of the characteristics of patients in EG and recommended modifications of such a movement, our study showed that patients in EG demonstrated flexion pattern during unilateral leg-raising movement at a subconscious level. Therefore, our results demonstrated the importance of clinical reasoning that combined the evaluation of direct and indirect trunk movement.
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Figure 7. Comparison of mean and standard deviations of back pressure value among the 3 groups. CG indicates control group; FG, flexion group; EG, extension group. *Significant difference between EG and controls (P < 0.01). †Significant difference between EG and FG (P < 0.01).
Limitations First, the actual angle of trunk movement could not be verified in this study because changes in back pressure were not calibrated with the changes in trunk movement. Second, the trunk muscle power and range of motion in each subject were not measured and not reflected in the results of this study. Third, we could not exclude the possibility of effects of body weight on the results because 5 kg isometric normalization task in this study included the upper body weight of each subject. However, there was internal consistency in the task for all subjects, and there was no difference in body mass index
TABLE 4. Comparison of Trunk Muscle Activity
Based on the Normalized Root-MeanSquare in Surface Electromyography at Foot-off During Unilateral LegRaising Movement Among the 3 Groups*
Figure 6. The individual waveforms of back pressure during unilateral leg-raising movement among the 3 groups. The individual waveforms of back pressure were averaged from the data of 4 times of unilateral leg-raising movement trials. CG indicates control group; FG, flexion group; EG, extension group.
RA
However, this trunk control strategy in EG was different from a normal movement pattern. It was pointed out that the excessive contraction of global muscle in patients with CLBP might be disadvantageous to the patient by causing an increase in the compression load on the lumbar segments.7,36 In this study, all patients who had CLBP for at least 3 months did not demonstrate any anxiety or pain in crook-lying unilateral leg raising. Moseley and Hodges37 indicated that some people who had the experience of persistent LBP might have difficulties in re-establishing normal motor control even when the pain had stopped. On the basis of these previous studies, we think that it is necessary to discuss the need for intervention for the compensatory trunk control observed in EG with careful consideration to the intensity of pain and the period from the onset of LBP. Spine
EO
MF
ES
Controls
FG
EG
(I)
0.45 ± 0.34
0.42 ± 0.41
1.09 ± 1.53
(C)
0.25 ± 0.13
0.27 ± 0.27
0.44 ± 0.73
(I)
0.51 ± 0.35
0.45 ± 0.37
1.58 ± 1.84†‡
(C)
0.85 ± 0.71
0.70 ± 0.87
2.18 ± 1.72†‡
(I)
0.08 ± 0.08
0.05 ± 0.06
0.06 ± 0.05
(C)
0.14 ± 0.26
0.05 ± 0.03
0.12 ± 0.11
(I)
0.09 ± 0.10
0.08 ± 0.06
0.08 ± 0.09
(C)
0.03 ± 0.04
0.04 ± 0.04
0.04 ± 0.03
*Values are mean ± SD. †Significant difference between EG and controls (P < 0.05). ‡Significant difference between EG and FG (P < 0.05). FG indicates flexion group; EG, extension group; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
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TABLE 5. Comparison of Trunk Muscle Activity
Based on the Change Ratio of Muscle Thickness Between Rest and at Footoff Measured by Ultrasound System Among the 3 Groups*
TrA
IO
Controls
FG
EG
(I)
1.09 ± 0.07
1.09 ± 0.09
1.14 ± 0.15
(C)
1.06 ± 0.10
1.10 ± 0.23
1.04 ± 0.11
(I)
1.06 ± 0.07
1.06 ± 0.05
1.11 ± 0.11
(C)
1.03 ± 0.06
1.06 ± 0.12
1.03 ± 0.05
*Values are mean ± SD. FG indicates flexion group; EG, extension group; TrA, transversus abdominis; IO, internal oblique; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
among the 3 groups. Therefore, we think that the effects of body weight on the results were minimal.
CONCLUSION This study demonstrated that the characteristics of trunk control during unilateral leg-raising movement were different depending on the types of NS-CLBP patients. These results indicate that patients with NS-CLBP might select compensatory trunk control strategies subconsciously to prevent the manifestation of LBP. Therefore, these results suggest the importance of clinical reasoning based on the characteristics of trunk control during active limb movement in different types of NS-CLBP patients.
➢ Key Points Characteristics of lumbar spine movement (pressure changes produced by the movement of the lumbar lordotic curve) and trunk muscle activities during unilateral leg raising movement were different depending on the types of NS-CLBP patients. These results indicate that patients with NSCLBP might select compensatory trunk control strategies subconsciously in order to prevent the manifestation of LBP. These results also suggest the importance of clinical reasoning process while paying attention to the different characteristics of trunk control during active limb movement for the management of different types of NS-CLBP patients.
References
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3. Deyo RA, Rainville J, Kent DL. What can the history and physical examination tell us about low back pain? JAMA 1992;268:760–5. 4. Hall H. Acute care: non traumatic low back pain. In: Fardon DF, Garfin SR, eds. Orthopaedic Knowledge Update: Spine 2. Rosemont, IL: AAOS; 2002:153–66. 5. Hall H. A simple approach to back pain management. Patient Care 1992;15:77–91. 6. Hall H, McIntosh G, Melles T. A different approach to back pain diagnosis: identifying a pattern of pain. Can J Contin Med Educ 1994;6:31–42. 7. Richardson CA, Hodges PW, Hides JA. Therapeutic Exercise for Lumbopelvic Stabilization: A motor Control Approach for the Treatment and Prevention of Low Back Pain. 2nd ed. Edinburgh, United Kingdom: Churchill Livingstone; 2004. 8. Sahrmann SA. Diagnosis and Treatment of Movement Impairment Syndromes. St. Louis, MO: Mosby; 2001. 9. Van Dillen LR, Sahrmann SA, Norton BJ, et al. Effect of active limb movements on symptoms in patients with low back pain. J Orthop Sports Phys Ther 2001;31:402–13. 10. Wilson L, Hall H, McIntosh G, et al. Intertester Reliability of a Classification System. Spine 1999;24:248–54. 11. Dankaerts W, O’Sullivan P, Burnett A, et al. Discriminating healthy controls and two clinical subgroups of nonspecific chronic low back pain patients using trunk muscle activation and lumbosacral kinematics of postures and movements. Spine 2009;34:1610–8. 12. Mok NW, Brauer SG, Hodges PW. Failure to use movement in postural strategies leads to increased spinal displacement in low back pain. Spine 2007;32:537–43. 13. Jull GM, Richardson CA, Toppenberg R, et al. Towards a measurement of active muscle control for lumbar stabilisation. Aust J Physiother 1993;39:187--93. 14. Richardson CA, Jull GA, Toppenberg R, et al. Techniques for active lumbar stabilisation for spinal protection: a pilot study. Aust J Physiother 1992;38:105–12. 15. Roussel NA, Nijs J, Mottram S, et al. Altered lumbopelvic movement control but not generalized joint hypermobility is associated with increased injury in dancers. Man Ther 2009;14:630–5. 16. Neumann DA. Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. Philadelphia, PA: Mosby; 2002. 17. Jensen MP, Karoly P, Braver S. The measurement of clinical pain intensity: a comparison of six methods. Pain 1986;27:117–26. 18. Ogon M, Krismer M, Sollner W, et al. Chronic low back pain measurement with visual analogue scales in different settings. Pain 1996;64:425–8. 19. Fritz JM, Irrgang JJ. A comparison of a modified Oswestry Low Back Pain Disability Questionnaire and the Quebec Back Pain Disability Scale. Phys Ther 2001;81:776–88. 20. Cholewicki J, Panjabi MM, Khachatryan A. Stabilizing function of trunk flexor-extensor muscles around a neutral spine posture. Spine 1997;22:2207–12. 21. Hermens HJ, Freriks B, Disselhorst-Klug C, et al. Development of recommendations for SEMG sensors and sensor placement procedures. J Electromyogr Kinesiol 2000;10:361–74. 22. Bunce SM, Moore AP, Hough AD. Measurement of abdominal muscle thickness using M-mode ultrasound imaging during functional activities. Man Ther 2004;9:41–4. 23. Bunce SM, Moore AP, Hough AD. M-mode ultrasound: a reliable measure of transverses abdominis thickness? Clin Biomech 2002;17:315–7. 24. Critchley DJ, Coutts FJ. Abdominal muscle function in chronic low back pain patients measurement with real-time ultrasound scanning. Physiotherapy 2002;88:322–33. 25. Mannion AF, Pulkovski N, Gubler D, et al. Muscle thickness changes during abdominal hollowing: an assessment of betweenday measurement error in controls and patients with chronic low back pain. Eur Spine J 2008;17:494–501. 26. Chaffin DB, Lee M, Freivalds A. Muscle strength assessment from EMG analysis. Med Sci Sports Exerc 1980;12:205–11. 27. Lawrence JH, De Luca CJ. Myoelectric signal versus force relationship in different human muscles. J Appl Physiol 1983;54:1653–59. 28. Perry J, Bekey GA. EMG—force relationships in skeletal muscle. Crit Rev Biomed Eng 1981;7:1–22.
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DIAGNOSTICS 29. McNeill T, Warwick D, Andersson G, et al. Trunk strengths in attempted flexion, extension, and lateral bending in healthy subjects and patients with low-back disorders. Spine 1980;5: 529–38. 30. Newton M, Thow M, Somerville D, et al. Trunk strength testing with iso-machines part 1: experimental evaluation of the Cybex II Back Testing System in normal subjects and patients with chronic low back pain. Spine 1993;18:812–24. 31. Cholewicki J, van Dieën J, Lee AS, et al. A comparison of a maximum exertion method and a model-based, sub-maximum exertion method for normalizing trunk EMG. J Electromyogr Kinesiol 2011;21:767–73. 32. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74.
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33. Ferreira PH, Ferreira ML, Hodges PW. Changes in recruitment of the abdominal muscles in people with low back pain: ultrasound measurement of muscle activity. Spine 2004;29:2560–6. 34. Hodges PW, Richardson CA. Altered trunk muscle recruitment in people with low back pain with upper limb movement at different speeds. Arch Phys Med Rehabil 1999;80:1005–12. 35. Hodges PW, Richardson CA. Delayed postural contraction of transversus abdominis in low back pain associated with movement of the lower limb. J Spinal Disord 1998;11:46–56. 36. Gardner-Morse MG, Stokes IA. The effects of abdominal muscle coactivation on lumbar spine stability. Spine 1998;23:86–9. 37. Moseley GL, Hodges PW. Reduced variability of postural strategy prevents normalization of motor changes induced by back pain: a risk factor for chronic trouble? Behav Neurosci 2006;120:474–6.
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DIAGNOSTICS
Characteristics of Trunk Control During Crook-Lying Unilateral Leg Raising in Different Types of Chronic Low Back Pain Patients Atsushi Ohe, PT, MS,*† Teiji Kimura, PT, PhD,‡ Ah-Cheng Goh, PT, PhD,§ Akemi Oba, PT,¶ Jun Takahashi, MD, PhD, and Yuji Mogami, MD**
Study Design. Cross-sectional observational study. Objective. To quantitatively clarify the characteristics of trunk control during unilateral leg-raising movement in different types of nonspecific chronic low back pain (NS-CLBP) patients who were identified by aggravation of symptoms during trunk movement. Summary of Background Data. Although there is a need to classify NS-CLBP patients for clinical decision making in physical therapy, the characteristics of trunk control during unilateral legraising movement in different types of NS-CLBP patients have not been quantitatively analyzed in previous studies by simultaneously measuring the lumbar spine movement, trunk muscle activity, and leg movement. Methods. Thirty NS-CLBP patients, of whom 13 were aggravated by trunk flexion (flexion group) and 17 were aggravated by trunk extension (extension group), and 30 healthy controls performed crook-lying unilateral leg-raising movement on the painful side in patient group and the dominant leg in controls. During the unilateral leg-raising movement, pressure changes produced by the movement of the lumbar lordotic curve, measured by a custom-made recording device, were used as indices of the lumbar spine movement. Trunk muscle activities were recorded by surface electromyography and
From the *Department of Rehabilitation, Tachiiri Orthopedic Clinic, Kyoto, Japan; †Department of Health Sciences, Graduate School of Medicine, Shinshu University, Nagano, Japan; ‡Department of Physical Therapy, School of Health Sciences, Shinshu University, Nagano, Japan; §Department of Physical Therapy, School of Health Sciences, Shinshu University, Nagano, Japan; ¶Department of Rehabilitation, Azumi General Hospital, Nagano, Japan; Department of Orthopaedic Surgery, Shinshu University, School of Medicine, Nagano, Japan; and **Department of Orthopedics, Azumi General Hospital, Nagano, Japan. Acknowledgment date: July 1, 2014. Revision date: November 18, 2014. Acceptance date: February 3, 2015. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Teiji Kimura, PT, PhD, Department of Physical Therapy, School of Health Sciences, Shinshu University, 3-1-1, Matsumoto, Nagano 390-8621, Japan; E-mail: tkimura@ shinshu-u.ac.jp DOI: 10.1097/BRS.0000000000000828
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diagnostic ultrasonography. The pressure changes and trunk muscle activities were statistically compared among the 3 groups. Results. At foot-off during unilateral leg-raising movement, the extension group demonstrated increase in pressure changes, whereas the flexion group and controls demonstrated decrease in pressure changes. Bilateral external obliques muscle activities in the extension group were significantly larger than those in the flexion group and controls (P < 0.05). Conclusion. This study demonstrated that the characteristics of trunk control during unilateral leg-raising movement were different depending on the types of NS-CLBP patients. These results indicate that patients with NS-CLBP might select compensatory trunk control strategies subconsciously to prevent the manifestation of LBP. These results also suggest the importance of the different characteristics of trunk control during active limb movement in the clinical reasoning process for the management of different types of NS-CLBP patients. Key words: low back pain, classification, motor control, leg raising, trunk movement, diagnostic ultrasonography, electromyography. Level of Evidence: N/A Spine 2015;40:550–559
I
t has been reported that more than 80% of low back pain (LBP) patients had no radiological abnormality evident and consequently were being diagnosed as nonspecific chronic LBP (NS-CLBP) patients.1–3 Because the characteristics of NSCLBP patients vary widely, there is a need to classify NS-CLBP patients into subgroups in order to identify the most effective treatments for the different types of NS-LBP patients.4–11 One such classification system is based on the mechanical stress imposed on the spine in NS-CLBP patients. This classification system can be divided into 2 main methods: mechanical stress imposed on the spine because of (i) direct movement of trunk4–6,10,11 or (ii) indirect movement of trunk from associated limb movement.7–9 With regard to the direct movement method described by Hall et al,4–6,10 NS-CLBP patients can be classified into a flexion group (FG) and an extension group (EG) on the basis of the direction of the trunk movement, which aggravates the symptoms. On the contrary, the indirect movement method is based on repetitive active limb movement during daily activities,
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DIAGNOSTICS which causes indirect movement of the trunk that can contribute to the patient’s LBP.7–9 Previous studies had reported the variety of indirect trunk movement during active limb movement in patients with chronic LBP.12 Sahrmann8 emphasized the importance of evaluation and treatment based on a classification of the characteristics of movement pattern of the trunk during active limb movement. Regarding the relationship between direct and indirect movement classification methods, it was thought that the type of LBP manifestation identified by the direct movement method might affect the movement pattern of the trunk during active limb movement so as to avoid the trunk movement in the direction that aggravates the LBP. However, the characteristics of movement pattern of the trunk during active limb movement in different types of LBP manifestations have not been reported in previous studies. Furthermore, it is thought that these different movement patterns of the trunk during active limb movement may be affected by the combined activities of both the superficial and deep trunk flexor and extensor muscles. However, the quantitative analysis of trunk control during active limb movement noninvasively by simultaneously measuring the lumbar spine movement and trunk muscle activities has also not been reported in previous studies. Our hypotheses were as follows: When healthy subjects in the control group (CG) raised the dominant leg in crook-lying unilateral leg raising, which was recommended as a suitable task to assess the lumbar spine movement,7,13–15 CG would demonstrate lumbar spine movement in the direction of the extension (i.e., anterior pelvic tilt) at foot-off because it was thought that unilateral leg-raising movement generated a torque on the pelvis and the lumbar spine in the direction of anterior pelvic tilt and the extension of lumbar spine movement.16 However, when NS-CLBP patients raised the leg on painful side, patients would demonstrate a different trunk control pattern that depended on the different types of LBP manifestation identified by direct trunk movement in NSCLBP patient. In other words, these patients would favor a trunk control pattern in the direction opposite to that which produced the pain during direct trunk movement. An understanding of these different movement patterns of the trunk in different types of LBP manifestations, identified by the direct movement method, could help the interpretation of motor control in NS-CLBP patients and could provide useful guidelines for the clinical reasoning process in these types of patients. The purpose of this study was to noninvasively and quantitatively clarify the characteristics of the trunk control during active limb movement in NS-CLBP patients with different types of LBP manifestation based on direct mechanical stress to the lumbar spine.
MATERIALS AND METHODS Subjects The NS-CLBP patients were recruited from the outpatient departments of local hospitals. The inclusion criteria for Spine
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the study were chronic LBP patients without neurological symptoms for at least 3 months, and severity of the pain was serious enough to require medical attention. The exclusion criteria for the study were patients with acute pain within the last 3 months, with the presence of structural deformity, inflammatory disease, nonmechanical LBP, or any other corresponding disorders preventing active rehabilitation. Healthy subjects who had no history of LBP requiring medical attention or resulting in absence from work within the last 10 years were recruited as controls from the hospital staff. The ethics committee of Shinshu University, School of Medicine approved this study. All subjects provided written informed consent.
Demographic Data All patients were evaluated before the first intervention. Height and body weight were measured for all subjects. Patients completed an additional questionnaire regarding their area of pain by using a body chart, the severity of pain by using a 100-mm visual analogue scale,17,18 and disability level by using modified Oswestry Low Back Pain Disability Questionnaire.19 Furthermore, patients were classified into an FG or an EG on the basis of the particular movement (trunk flexion or extension in standing) that aggravated their symptoms according to the Low Back Pain Classification System.4–6,10 The demographic data of subjects are listed in Table 1. One-way analysis of variance for age, body weight, height, and body mass index showed no significant difference among the 3 groups. Independent t test for visual analogue scale and Mann-Whitney U test for modified Oswestry Low Back Pain Disability Questionnaire showed no significant difference between FG and EG.
Task of Active Limb Movement The subjects were positioned in crook lying. The examiner instructed the timing of breathing and gave cues at the end of expiration. The subjects flexed their unilateral hip joint from 60° to 90°, which was regulated by a sponge mat for more than 2 seconds according to a timing cue from the examiner (Figure 1). In this study, unilateral leg-raising movement was performed on the painful side in patients with LBP and on the dominant side in the CG. An electronic metronome (ME-110; YAMAHA Corp., Hamamatsu-shi, Shizuoka, Japan) was used for the regulation of the speed in unilateral leg-raising movement.
Instrumentation During unilateral leg-raising movement, the back pressure that was the pressure between the surface of the low back and the bed was recorded with a custom-made back pressure– recording device; the trunk muscle activities of rectus abdominis (RA), external obliques (EO), multifidus (MF), and erector spinae (ES) muscles were recorded by using surface electromyography (sEMG); and the trunk muscle activities of transverse abdominis and internal obliques were recorded by using ultrasonography (US). www.spinejournal.com
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TABLE 1. Demographic Data* Controls (n = 30, M = 14, F = 16 ) FG (n = 13, M = 6, F = 7) EG (n = 17, M = 7, F = 10) Age, yr
P
33.2 ± 9.0 (22–51)
38.9 ± 9.5 (24–58)
32.6 ± 9.0 (20–53)
0.12
58.3 ± 10.8 (43.4–88.0)
59.0 ± 9.6 (52.2–85.1)
57.7 ± 9.2 (43.9–80.1)
0.87
Height, cm
165.2 ± 7.7 (153.3–180.2)
164.7 ± 7.1 (153.8–176.9)
164.8 ± 7.3 (157.1–183.0)
0.97
BMI, kg/m*
21.2 ± 2.6 (17.2–27.8)
21.7 ± 2.9 (16.8–28.1)
20.9 ± 2.1 (17.2–25.2)
0.68
VAS
N/A
42.2 ± 12.8 (18–58)
34.7 ± 14.4 (18–68)
0.26
Modified ODQ
N/A
11.9 ± 4.3 (4–19)
9.7 ± 4.0 (4–18)
0.15
Body weight, kg
Pain scale
*Values are mean ± SD (range). M indicates male; F, female; FG, flexion group; EG, extension group; BMI, body mass index; VAS, visual analogue scale; N/A, not applicable; ODQ, Oswestry Low Back Pain Disability Questionnaire.
Back Pressure–Recording Device Pressure Biofeedback Unit (PBU; Stabilizer, Chattanooga, CA) has been developed as an indirect method to monitor the lumbopelvic movement in a clinical setting.7,13–15 PBU placed beneath the lumbar spine in supine or crook-lying position can monitor the back pressure changes during lumbar spine movement.7,13–15 An increase in back pressure from baseline would indicate a posterior pelvic tilt with the lumbar spine movement toward the direction of flexion, and a decrease would indicate an anterior pelvic tilt with the lumbar spine movement toward the direction of extension.7 We constructed a custom-made back pressure–recording device that consisted of a PBU, a custom-made air pressure sensor (ME Inc., Nagano, Japan), and
a direct-current amplifier (Digital Indicator F430, UNIPULSE Co. Ltd., Tokyo, Japan) to record the analogue signal of back pressure from the PBU (Figure 2).
Foot Switch To identify the timing of initiation in the unilateral leg-raising movement, a foot switch (ME Inc., Nagano, Japan) (Figure 3) was placed beneath the heel of the designated side. This foot switch was able to output the analogue signal at foot-off.
Surface Electromyography Trunk muscle activities were recorded by using an 8 channel telemetric sEMG system (Tele MyoG2 EM-602; Noraxon
Figure 1. Task of unilateral leg-raising movement and block diagram of the synchronization of the timeline between a biosignal-analyzing software in personal computer and measurement software in ultrasound system by using foot switch signal that was imported to both software. sEMG indicates surface electromyography; ULR, unilateral leg raising.
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DIAGNOSTICS
Figure 2. Custom-made back pressure–recording device (ME, Inc, Nagano, Japan).
USA Inc., Scottsdale, AZ). Bipolar Ag/AgCl surface disposable electrodes (Vitrode L-150X; Nihon Kohden Co. Ltd., Tokyo, Japan) were placed with a center-to-center distance of 3 cm, parallel to the muscle fibers in the center of the muscle belly, over the following muscles bilaterally: RA (3 cm lateral to the umbilicus), EO (15 cm lateral to the umbilicus), MF (2 cm lateral to L4–L5 spinous processes), and ES (3 cm lateral to L3 spinous process).20 The earth electrode was placed on the skin overlying the right anterior superior iliac spine. Skin preparation for sEMG was carried out according to the procedure described by Hermens et al.21
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Figure 3. Foot switch (ME, Inc, Nagano, Japan).
Diagnostic Ultrasonography US were recorded with a 5.5-cm, 7-MHz linear head transducer (Cardio & Vascular Ultrasound System Vivid 7, GE Healthcare Japan Inc., Tokyo). To record the time series data of the muscle thickness during unilateral leg raising, motion (M) mode22,23 was used at 96 frames per second (Figure 4). The probe was set in a custom-made pad to minimize variability in the angle and pressure over the target area.23 The probe was placed 2.5 cm anterior to the midpoint between the iliac crest and the costal margin on the midaxillary line.24,25 The probe position and gain were
Figure 4. M mode was used simultaneously with B mode to enable the operator to accurately adjust the position of the M mode beam, which is indicated by a dotted line on the B mode. B-mode image revealed a cross section of TrA and IO. M mode is displayed as a 1-dimensional view of the TrA and IO over time in 4 seconds during unilateral leg-raising movement. IO indicates internal oblique; TrA, transversus abdominis. Spine
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DIAGNOSTICS finely adjusted to ensure optimum clarity because of the differences in the body shape and composition between subjects.
Procedure The air mat of the custom-made back pressure–recording device was placed horizontally under the lumbar spine of the subjects with the lower edge of air cell corresponding to the level of S2.7 The PBU was inflated to 40 mm Hg (baseline pressure).7 Raw sEMG signals are usually normalized with the maximum EMG value obtained from maximum voluntary contraction based on the linear relationship between force-generated and integrated EMG level.26–28 However, it was known that NS-CLBP patients were unable to perform maximum contractions.29,30 Therefore, in this study, the amplitude of sEMG comparable with 5 kgf, which was determined in our pilot study as the comfortable level where the subjects did not feel pain and anxiety, was recorded to estimate relative exerted force in each muscle as a method of normalization in sEMG. Cholewicki et al31 indicated that the problem in using reference point method for normalizing EMG signals in patients with LBP is that patients might demonstrate different recruitment pattern of trunk muscle activities during the normalization task. Hence, we compared raw sEMG data from the 5 kgf task and confirmed that there was no significant difference in each of these muscles among the 3 groups. For each muscle, 5 kgf was established by a handheld dynamometer (HHD; μ-tas F-1; ANIMA Corp, Tokyo, Japan), which was fixed by a belt. Subjects were stabilized to the bed at the chest and the pelvis by a belt for each muscle test. For the RA and the EO, the subjects performed sit-up and oblique sit-up from supine position, respectively, with the hips flexed to 60°, attempting to push the HHD placed on the sternum or on the shoulder. For the MF and the ES, the subjects performed back extension from prone position, attempting to push the HHD placed on the upper thoracic area (between the base of spine of both scapulae). The subjects pushed the HHD gradually until they reached 5 kgf, and held it for 5 seconds. The trials for each muscle were performed twice with a 1-minute rest between trials. Bilateral US of transverse abdominis and internal obliques were measured separately because there was only 1 ultrasound probe available. Subjects practiced unilateral leg-raising movement for 3 times, and data collection was executed 4 times. The order of the laterality of the ultrasound probe during unilateral leg-raising movement was determined by using a random number list. These 4 trials provided 4 repetitive sets of data of back pressure and sEMG and 2 repetitive sets of data of US. Each trial was performed with 30 seconds rest.
Data Analysis Signals from back pressure–recording device, foot switch, and sEMG were A/D converted at a sampling rate of 1500 Hz and analyzed by using a biosignal-analyzing software (MyoResearch XP EM-129M; Noraxon USA, Inc, Scottsdale, AZ). 554
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Raw sEMG signals were band-pass filtered between 20 and 350 Hz and smoothing of the sEMG signals was performed by calculating the root-mean-square (RMS) using 50-ms moving window. RMS of each muscle at foot-off was normalized by using the amplitude of RMS comparable with 5 kgf obtained from the 5 kgf task mentioned in the procedure mentioned previously. The change of thickness for each muscle in US was measured at rest and at foot-off using the measurement software in the ultrasound system on the basis of the muscle fascial boundaries from the M-mode image (Figure 4). The timeline between the biosignal-analyzing software in the personal computer and the measurement software in the ultrasound system was synchronized by using the foot switch signal that was imported to both software (Figure 1). Data analyses were performed for the following parameters: (1) back pressure value (BPV) at foot-off, (2) normalized RMS at foot-off in each RA, EO, MF, and ES (i.e., RMS at foot-off/RMS comparable with 5 kgf/body mass), and (3) muscle contraction ratio at foot-off in each transverse abdominis and internal obliques (i.e., muscle thickness at foot-off/ muscle thickness at rest) (Figure 5).
Figure 5. Diagram of data analysis in sEMG, US, back pressure, and foot switch. sEMG shows normalized RMS. US shows thickness of muscle. Back pressure shows change of pressure. sEMG indicates surface electromyography; US, ultrasonography; BP, back pressure; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; IO, internal oblique; TrA, transversus abdominis; (I), ipsilateral to raised leg; (C), contralateral to raised leg; BPV, back pressure value at foot-off.
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DIAGNOSTICS Statistical Analysis Intraclass correlation coefficients were calculated to confirm the relative reliability of each parameter (4 repetition data of back pressure and sEMG and 2 repetition data of US) during unilateral leg-raising movement. A BlandAltman analysis was used to confirm the absolute reliability and to calculate the limits of agreement of each parameter. A Bland-Altman analysis for all 4 trials is not possible without generating huge amount of unnecessary results. We think that the systematic error from the 4 trials can most likely be attributed to fatigue, habituation, and changes in the skin impedance below the electrodes, with increasing repetitions from the 4 trials. Therefore, we chose the first and the last trials for the Bland-Altman analysis of the EMG and BPV measurements. The differences in BPVs and each trunk muscle activity among the 3 groups were compared by using analysis of variance with a post hoc Tukey honestly significant difference test for parametric analysis and the Kruskal-Wallis test with post hoc Steel-Dwass test for nonparametric analysis. The significance level for all testing was set at 0.05. Statistical analysis was performed with SPSS 18.0 for Windows (SPSS Inc., Chicago, IL) except for Steel-Dwass test because SPSS 18.0 did not support multiple comparison for nonparametric variables. Therefore, Steel-Dwass test was performed with “R” statistical software system 2.8.1 (http://www.r-project.org/).
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The trunk muscle activities in US among the 3 groups are shown in Table 5. No significant differences among the 3 groups for all parameters of the trunk muscle activities of US were observed.
DISCUSSION Noninvasive and Quantitative Measurement Method for Trunk Control In this study, we developed a custom-made back pressure– recording device that could provide an analogue signal of back pressure from PBU to quantitatively analyze the trunk control during unilateral leg-raising movement by synchronizing the data between the lumbar spine movement and trunk muscle activities, which were derived from sEMG and ultrasonography. Although some previous studies had used wire electrodes for recording local trunk muscle activity,33–35 these methods were invasive and unsuitable for patients. However, this study used a noninvasive measurement method that combined the sEMG and ultrasonography data. The results of the intraclass correlation coefficients for each parameter (Table 2) demonstrated moderate to almost perfect relative reliability.
TABLE 2. Average Intraclass Correlation
Coefficients (ICC) of Back Pressure (ICC1,4), sEMG (ICC1,4), and US (ICC1,2) for All Subjects When Unilateral Leg Raise Movement Was Performed
RESULTS The relative reliability of all parameters during unilateral leg raising was assessed by intraclass correlation coefficient. In all parameters for the 3 groups, moderate to almost perfect reliability, were found (Table 2).32 The absolute reliability was confirmed by using a Bland-Altman analysis. The results showed that there was no fixed or proportional bias for each parameter. The limits of agreement for each parameter are shown in Table 3. The individual waveforms of back pressure that were averaged data from 4 repetitions of unilateral leg-raising trials are shown in Figure 6. It showed that all subjects demonstrated the back pressure onset preceding foot-off in all groups. The percentage distribution of subjects in each of the 3 groups demonstrating an increase or decrease in back pressure from baseline at foot-off is as follows: for CG, 7 subjects (23%) and 23 subjects (77%) demonstrated an increase and decrease in back pressure, respectively; for FG, 3 patients (23%) and 10 patients (77%) demonstrated an increase and decrease in back pressure, respectively; and for EG, 11 patients (65%) and 6 patients (35%) demonstrated an increase and decrease in back pressure, respectively. Significant difference in BPVs was observed among the 3 groups, whereas BPVs in EG demonstrated an increase and BPVs in FG and controls demonstrated a decrease at footoff (P < 0.01) (Figure 7). The trunk muscle activities in sEMG among the 3 groups are shown in Table 4. Bilateral EO in the EG were significantly larger than those in the FG and controls (P < 0.05). Spine
Controls
FG
EG
0.73
0.79
0.71
RA (I)
0.99
0.91
0.77
RA (C)
0.98
0.96
0.92
EO (I)
0.67
0.77
0.82
EO (C)
0.77
0.66
0.86
MF (I)
0.93
0.65
0.94
MF (C)
0.74
0.87
0.81
ES (I)
0.90
0.86
0.89
ES (C)
0.91
0.85
0.90
TrA (I)
0.63
0.47
0.51
TrA (C)
0.62
0.59
0.58
IO (I)
0.79
0.57
0.61
IO (C)
0.62
0.59
0.73
BP BPV sEMG
US
FG indicates flexion group; EG, extension group; BP, back pressure; BPV, back pressure value at foot-off; sEMG, surface electromyography; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; US, ultrasonography; TrA, transversus abdominis; IO, internal oblique; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
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TABLE 3. Limits of Agreement in Back Pressure, sEMG, and US for All Subjects When Unilateral Leg
Raise Movement Was Performed* Controls
FG
EG
−3.45 to 3.19
−1.10 to 2.56
−1.67 to 2.42
RA (I)
−0.19 × 10−1–0.16 × 10−1
−0.55 × 10−2–0.51 × 10−2
−0.35 × 10−1–0.31 × 10−1
RA (C)
−0.12 × 10−1–0.11 × 10−1
−0.34 × 10−2–0.50 × 10−2
−0.11 × 10−1–0.85 × 10−2
EO (I)
−0.45 × 10−1–0.34 × 10−1
−0.86 × 10−2–0.97 × 10−2
−0.48 × 10−1–0.49 × 10−1
EO (C)
−0.35 × 10−1–0.32 × 10−1
−0.57 × 10−2–0.80 × 10−2
−0.41 × 10−1–0.61 × 10−1
MF (I)
−0.19 × 10−2–0.16 × 10−2
−0.15 × 10−2–0.12 × 10−2
−0.15 × 10−2–0.80 × 10−3
MF (C)
−0.56 × 10−2–0.50 × 10−2
−0.35 × 10−3–0.41 × 10−3
−0.17 × 10−2–0.22 × 10−2
ES (I)
−0.30 × 10−2–0.21 × 10−2
−0.16 × 10−2–0.31 × 10−2
−0.12 × 10−2–0.77 × 10−3
ES (C)
−0.42 × 10−3–0.31 × 10−3
−0.49 × 10−3–0.12 × 10−2
−0.11 × 10−2–0.18 × 10−2
TrA (I)
−0.21 to 0.15
−0.10 to 0.14
−0.10 to 0.17
TrA (C)
−0.17 to 0.14
−0.09 to 0.06
−0.11 to 0.09
IO (I)
−0.09 to 0.07
−0.02 to 0.20
−0.08 to 0.19
IO (C)
−0.09 to 0.09
−0.06 to 0.04
−0.02 to 0.04
BP BPV sEMG
US
*Back pressure and sEMG showed limits of agreement of the data in the first and the fourth of the 4 trials. US data showed limits of agreement of the data of 2 trials. FG indicates flexion group; EG, extension group; BP, back pressure; BPV, back pressure value at foot-off; sEMG, surface electromyography; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; US, ultrasonography; TrA, transversus abdominis; IO, internal oblique; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
Moreover, the results of the Bland-Altman analysis for each parameter demonstrated no systematic bias and small range of limits of agreement (Table 3). Therefore, it could be demonstrated that the measurement system used in this study was feasible. It was also demonstrated that intraindividual variability of lumbar spine movement and trunk muscle activities during unilateral leg-raising movement was comparatively small in all groups.
Implications for Clinical Reasoning and Research Previous studies12 indicated the existence of a variable pattern of trunk movement in NS-CLBP patients during active limb movements. However, the reason for the various patterns was not discussed. We hypothesized that the different trunk control during unilateral leg-raising movement depended on the different types of LBP manifestation that were identified by direct trunk movement in NS-CLBP patient. The results of this study supported our hypothesis. The patients in FG demonstrated the lumbar spine movement toward the direction of extension at foot-off in a similar manner with controls (Figures 6 and 7). It was pointed out that the contraction of hip flexor such as the iliopsoas and the rectus femoris that were protagonistic muscles in unilateral leg raising would generate a torque on the pelvis and the lumbar spine in the 556
direction of anterior pelvic tilt and the extension of lumbar spine movement.16 Furthermore, patients in FG might have no need to avoid the lumbar spine movement toward the direction of extension because it was not associated with the aggravating movement of lumbar spine for FG. On the contrary, patients in EG demonstrated the lumbar spine movement toward the direction of flexion at foot-off (Figures 6 and 7). Moreover, this directional characteristic of lumbar spine movement in EG was supported in the sEMG data, with the bilateral EO showing increased activity (Table 4). The extension of lumbar spine movement could increase stress on posterior structures such as the apophyseal joints.16 Hence, it was thought that the lumbar spine movement organized trunk muscle activity in EG was an example of the self-organized compensatory trunk control strategies to prevent the manifestation of LBP. Although Sahrmann8 proposed that the excessive extension of lumbar spine during unilateral leg flexion was one of the characteristics of patients in EG and recommended modifications of such a movement, our study showed that patients in EG demonstrated flexion pattern during unilateral leg-raising movement at a subconscious level. Therefore, our results demonstrated the importance of clinical reasoning that combined the evaluation of direct and indirect trunk movement.
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Figure 7. Comparison of mean and standard deviations of back pressure value among the 3 groups. CG indicates control group; FG, flexion group; EG, extension group. *Significant difference between EG and controls (P < 0.01). †Significant difference between EG and FG (P < 0.01).
Limitations First, the actual angle of trunk movement could not be verified in this study because changes in back pressure were not calibrated with the changes in trunk movement. Second, the trunk muscle power and range of motion in each subject were not measured and not reflected in the results of this study. Third, we could not exclude the possibility of effects of body weight on the results because 5 kg isometric normalization task in this study included the upper body weight of each subject. However, there was internal consistency in the task for all subjects, and there was no difference in body mass index
TABLE 4. Comparison of Trunk Muscle Activity
Based on the Normalized Root-MeanSquare in Surface Electromyography at Foot-off During Unilateral LegRaising Movement Among the 3 Groups*
Figure 6. The individual waveforms of back pressure during unilateral leg-raising movement among the 3 groups. The individual waveforms of back pressure were averaged from the data of 4 times of unilateral leg-raising movement trials. CG indicates control group; FG, flexion group; EG, extension group.
RA
However, this trunk control strategy in EG was different from a normal movement pattern. It was pointed out that the excessive contraction of global muscle in patients with CLBP might be disadvantageous to the patient by causing an increase in the compression load on the lumbar segments.7,36 In this study, all patients who had CLBP for at least 3 months did not demonstrate any anxiety or pain in crook-lying unilateral leg raising. Moseley and Hodges37 indicated that some people who had the experience of persistent LBP might have difficulties in re-establishing normal motor control even when the pain had stopped. On the basis of these previous studies, we think that it is necessary to discuss the need for intervention for the compensatory trunk control observed in EG with careful consideration to the intensity of pain and the period from the onset of LBP. Spine
EO
MF
ES
Controls
FG
EG
(I)
0.45 ± 0.34
0.42 ± 0.41
1.09 ± 1.53
(C)
0.25 ± 0.13
0.27 ± 0.27
0.44 ± 0.73
(I)
0.51 ± 0.35
0.45 ± 0.37
1.58 ± 1.84†‡
(C)
0.85 ± 0.71
0.70 ± 0.87
2.18 ± 1.72†‡
(I)
0.08 ± 0.08
0.05 ± 0.06
0.06 ± 0.05
(C)
0.14 ± 0.26
0.05 ± 0.03
0.12 ± 0.11
(I)
0.09 ± 0.10
0.08 ± 0.06
0.08 ± 0.09
(C)
0.03 ± 0.04
0.04 ± 0.04
0.04 ± 0.03
*Values are mean ± SD. †Significant difference between EG and controls (P < 0.05). ‡Significant difference between EG and FG (P < 0.05). FG indicates flexion group; EG, extension group; RA, rectus abdominis; EO, external oblique; MF, lumbar multifidus; ES, erector spinae; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
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TABLE 5. Comparison of Trunk Muscle Activity
Based on the Change Ratio of Muscle Thickness Between Rest and at Footoff Measured by Ultrasound System Among the 3 Groups*
TrA
IO
Controls
FG
EG
(I)
1.09 ± 0.07
1.09 ± 0.09
1.14 ± 0.15
(C)
1.06 ± 0.10
1.10 ± 0.23
1.04 ± 0.11
(I)
1.06 ± 0.07
1.06 ± 0.05
1.11 ± 0.11
(C)
1.03 ± 0.06
1.06 ± 0.12
1.03 ± 0.05
*Values are mean ± SD. FG indicates flexion group; EG, extension group; TrA, transversus abdominis; IO, internal oblique; (I), ipsilateral to raised leg; (C), contralateral to raised leg.
among the 3 groups. Therefore, we think that the effects of body weight on the results were minimal.
CONCLUSION This study demonstrated that the characteristics of trunk control during unilateral leg-raising movement were different depending on the types of NS-CLBP patients. These results indicate that patients with NS-CLBP might select compensatory trunk control strategies subconsciously to prevent the manifestation of LBP. Therefore, these results suggest the importance of clinical reasoning based on the characteristics of trunk control during active limb movement in different types of NS-CLBP patients.
➢ Key Points Characteristics of lumbar spine movement (pressure changes produced by the movement of the lumbar lordotic curve) and trunk muscle activities during unilateral leg raising movement were different depending on the types of NS-CLBP patients. These results indicate that patients with NSCLBP might select compensatory trunk control strategies subconsciously in order to prevent the manifestation of LBP. These results also suggest the importance of clinical reasoning process while paying attention to the different characteristics of trunk control during active limb movement for the management of different types of NS-CLBP patients.
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