223
Work 51 (2015) 223–228 DOI 10.3233/WOR-141856 IOS Press
Comparison of the lumbar flexion angle and repositioning error during lumbar flexion-extension in young computer workers in Korea with differing back pain Min-Hee Kima and Won-Gyu Yoob,∗ a
b
Institute of Health Science, Yonsei University, Wonju, Korea Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, Gimhae, Korea
Received 11 April 2013 Accepted 23 December 2013
Abstract. BACKGROUND: Differences in LBP symptoms are particularly important with regard to the controversy over repositioning error because there can be considerable variation in the pattern of LBP symptoms in a heterogeneous LBP group. For this reason, several researchers have suggested that a study of subdivided LBP types is needed. Indeed, some recent studies have attempted to differentiate LBP subgroups. OBJECTIVE: This study used a comparative cross-sectional design to compare the lumbar flexion angle and repositioning error between people with and without LBP during a lumbar flexion-extension task. METHODS: The subjects were divided into three groups: a control group of 13 asymptomatic subjects, 13 LBP subjects with L4-5 pain associated with lumbar flexion, and 13 LBP subjects with L4-5 pain associated with lumbar extension. The subjects performed a lumbar flexion-extension task. Joint kinematics on the lumbar flexion angle and lumbar spine repositioning error were measured using a 3-D motion capture system. RESULTS: The lumbar flexion angle of the LBP group with flexion pain was significantly greater than that of the asymptomatic group and the LBP group with extension pain. The difference in lumbar repositioning error was significantly greater in the LBP group with lumbar flexion pain than in the asymptomatic group. CONCLUSIONS: This study suggests that lumbar hyper-mobility occurred and proprioception of the lumbar segment was decreased in people with LBP associated with lumbar flexion compared with people with LBP associated with lumbar extension. We also suggest that a lumbar repositioning error measurement using the lumbar flexion-extension test may be a more effective evaluation method in people with LBP associated with lumbar flexion than in those with LBP associated with lumbar extension. Keywords: Hyper-mobility, low back pain, proprioception, repositioning error
1. Introduction
∗ Corresponding author: Won-Gyu Yoo, Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, 607 Obangdong, Gimhae, Gyeongsangnamdo 621-749, Korea. Tel.: +82 55 320 3994; Fax: +82 55 329 1678; E-mail: [email protected].
Recently, an association between LBP and prolonged posture, specifically prolonged sitting, has been reported [27]. Remaining seated for long periods of time can cause special problems for the spine, circulation, muscles, and joints [15]. Phillips et al. [19] stated that the sitting position is a potent risk factor for LBP.
c 2015 – IOS Press and the authors. All rights reserved 1051-9815/15/$35.00
224
M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error
Prolonged sitting posture is a risk factor for LBP continues. It may be that prolonged sitting should not be encouraged in LBP patients [15,19]. Panjabi [16] suggested that the stabilizing systems of the spine consist of passive spinal structures, active spinal muscles, and neural control. According to this theory, increased lumbar spine motion in low back pain (LBP) patients indicates inappropriate control of the neuromuscular system [27]. Lumbar spine movements and alignment patterns are provided by active muscles and passive ligaments and control a large proportion of spinal stability [2,29]. Mechanoreceptors in the spine provide proprioceptive information for structures including passive ligaments. Stretching or deformation of supraspinous or intraspinous ligaments stimulates the mechanoreceptors, and the paraspinal muscles are then activated via neural control to facilitate spinal stability [24]. Thus, proprioceptive information from mechanoreceptors may be important in controlling lumbar spine motion [8,14]. Proprioception has been regarded as necessary for body movement control and is important in diagnosing motor-control impairment [18]. Proprioception provides awareness and determines the position of the body in space, so it can adjust and control movement [17]. Spinal structures impaired by injury or stress can lead to impairment in movement control of the spine and in proprioception [17,18]. Proprioceptive impairment is known to result in poor stabilization of the lumbar spine, and is described as repositioning error [14,17,18]. Newcomer et al. [13] showed significantly higher repositioning error in patients with LBP during lumbar flexion. However, Parkhurst et al. [17] reported no correlation between LBP and repositioning error, and some researchers have reported no proprioceptive impairment in people with LBP. It is worth considering the reasons for these inconsistent results with regard to repositioning error in LBP studies. The inconsistent findings may be due to subject characteristics, variation in experimental conditions, or differences in LBP symptoms. Differences in LBP symptoms are particularly important with regard to the controversy over repositioning error because there can be considerable variation in the pattern of LBP symptoms in a heterogeneous LBP group [4]. The results found in subjects complaining of one pattern of LBP symptoms in a heterogeneous LBP group could be counterbalanced by opposite results found in subjects complaining of another pattern of LBP symptoms [26]. To address these concerns, several researchers have suggested that a study of subdivided LBP types is needed.
Indeed, some recent studies have attempted to differentiate LBP subgroups [4,5]. Korean household Internet and computer distribution rates have rapidly increased since 2000 and Korea has now been identified as a country with the highest distribution of Internet and computers in the world with the rates exceeding 80% [30]. The conglomerates and public companies in Korea use 1 computer per worker [30]. A review of the rates of use of the Internet using computers by age indicated that teenagers and people in their 20s use the Internet the most frequently [30]. Therefore, as of 2013, Korean males and females in their 20s and 30s are thought to be exposed the most to diseases related to computers. Therefore, the characteristics of low back pain in young computer workers in Korea that correspond to these age groups should be classified. Thus, in the present study, we compared lumbar movement, specifically, lumbar flexion angle and lumbar spine repositioning error, during a lumbar flexion-extension task in young computer workers in Korea between LBP subgroups with differing back pain symptoms using 3-D motion analysis.
2. Methods 2.1. Participants The subjects were divided into three groups: a control group of 13 asymptomatic subjects (8 males, 5 females), 13 LBP subjects with L4-5 pain associated with lumbar flexion (8 males, 5 females), and 13 LBP subjects with L4-5 pain associated with lumbar extension (8 males, 5 females). They were young computer workers in Korea with LBP who sat for more than 4 h/ day at work. The LBP groups included mechanical LBP without radiating pain. Exclusion criteria were 1) a history of spinal or leg surgery, 2) a medical diagnosis of ankylosing spondylitis, 3) a medical diagnosis of rheumatoid arthritis, 4) a medical diagnosis of degenerative disease, 5) a medical diagnosis of other neurological disorders, or 6) visually determined severe kyphosis or scoliosis. Twenty-six subjects with nonspecific LBP for at least 3 months’ duration were recruited from the local community after meeting the inclusion and exclusion criteria. The subjects were classified based on clinical examinations. The LBP subjects with lumbar pain associated with lumbar flexion and extension were classified according to the methods proposed by McKenzie [11] and Sahrmann [20]. The McKenzie ap-
M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error
proach evaluates LBP based on the patient’s response to standardized mechanical loading strategies [11]. The Sahrmann approach classifies movement system impairment based on a kinesiopathological approach and movement directions and symptoms associated with LBP [20]. The common assessment concept identifies the directional preference that provokes or alleviates LBP symptoms. Using these classification systems, the patients were classified into two LBP subgroups: one in which lumbar flexion caused more symptoms and the other in which lumbar extension caused more symptoms [11,12,20]. The movement tests related to lumbar flexion symptoms included trunk flexion while standing, hip and knee flexion in the supine position, backward rocking in the quadruped position, and lumbar flexion while sitting. The symptoms usually increased and became peripheralized with repeated flexion and usually decreased and became centralized with repeated extension of the lumbar spine. The movement tests related to lumbar extension symptoms included trunk extension while standing, trunk and hip extension in the prone position, forward rocking in the quadruped position, and shoulder flexion in the supine position. The symptoms usually increased and became peripheralized with repeated extension and usually decreased and became centralized with repeated flexion of the lumbar spine. All subjects completed the self-reported Oswestry Disability Index [3]. Table 1 summarizes the characteristics of the three groups of subjects. There were no significant differences in age, height, and weight among the three groups. There was a significant difference in the Oswestry Disability Index between the controls and each LBP group (P < 0.05) and no significant difference in this index between the LBP groups with flexion and extension pain (P > 0.05). This study was approved by the Yonsei University Faculty of Health Sciences Human Ethics Committee and the subjects provided written informed consent before participating. 2.2. Kinematic data The lumbar flexion-extension task consisted of standing, flexion-extension, and re-standing sections. To record kinematic data, we used a 3-D motion capture system. The 3-D motion capture system consisted of six infrared cameras was used to record the kinematic data. The kinematic data were collected using camera sampling at 60 Hz. In total, 20 retro-reflective markers were attached at the T12 and L2 spinous pro-
225
cesses bilaterally, 3 cm lateral from the L2 spinous process, the anterior and posterior superior iliac spines, lateral femoral epicondyle, the midpoint between the anterior superior iliac spine and the lateral femoral epicondyle, the lateral malleolus, the midpoint between the lateral femoral epicondyle and the lateral malleolus, the distal head of the second metatarsal, and the posterior aspect of the calcaneus. The reflective markers were attached at these anatomical locations according to the VICON Plug-in-Gait marker placement protocol. The subjects stood with their feet separated and placed equally on the experimental floor, and static trials were recorded after placing retro-reflective markers on the subjects. The anthropometric measurements made included the height, weight, leg length, and joint width of the knee and ankle. All trials were processed with VICON Nexus software. The recorded kinematic data filtered with a Woltring filter were computed with VICON Plug-In Gait and a customized BodyLanguage model. The kinematic parameters were the flexion angle and repositioning error of the lumbar spine. The lumbar flexion angle was defined as the sagittal angular displacement between the mean angle of the middle 1 second in the standing phase and the mean angle of the middle 1 second in the maximum lumbar flexion of the flexion-extension phase. The repositioning error of the lumbar spine was defined as the difference in the mean sagittal angle of the middle 1 second between the standing and re-standing phases of the task (| mean angle in re-standing – mean angle in standing |). The kinematic data obtained during the lumbar flexion-extension task were analyzed and reported using Polygon software. 2.3. Procedures The subjects were instructed to stand with their arms hanging freely by their sides and their feet spaced slightly apart. For dynamic capture, the subjects were required to stand for 5 seconds (standing phase), to flex forward with their arms dangling freely and hold themselves in the fully flexion position for 3 seconds, and then to return to the upright position (flexionextension phase). Finally the subjects were asked to maintain an upright standing position for 5 seconds (restanding phase). The subjects performed three trials of the lumbar flexion-extension task after practicing and the mean of three trials following a metronome was used for the data analysis.
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M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error Table 1 General characteristics of the subjects Parameter Age (y) Height (cm) Weight (kg) ODIa score
Control (n = 13) 23.81 ± 2.90 171.23 ± 8.44 66.25 ± 10.26 3.04 ± 1.48
LBP with flexion pain (n = 13) 23.47 ± 2.35 173.12 ± 9.14 67.15 ± 11.09 12.53 ± 5.88∗
LBP with extension pain (n = 13) 23.79 ± 3.91 172.09 ± 8.45 66.88 ± 11.03 14.18 ± 4.27∗
p 0.901 0.323 0.287 0.000
NOTE. Values are mean ± SD. a The Oswestry Disability Index. ∗ Significant difference compared with the control group. Table 2 Lumbar flexion angle during the lumbar flexion-extension task Angle Lumbar flexion ∗ Significant
Control 47.0 ± 7.6
Mean ± SD (degrees) LBP with flexion pain 54.5 ± 6.9∗
p LBP with extension pain 46.5 ± 8.0
0.011
difference compared with the control group and LBP with extension pain. Table 3 Repositioning errorsa of the lumbar spine
Reposition error Lumbar spine
Control 1.2 ± 1.3
Mean ± SD (degrees) LBP with flexion pain 3.2 ± 1.8∗
p LBP with extension pain 2.2 ± 2.0
0.040
a Calculated
by relative displacement changes between standing and re-standing; (sagittal angle in re-standing – sagittal angle in standing). ∗ Significant difference compared with the control group.
2.4. Statistical analysis SPSS software (ver. 14.0; SPSS, Chicago, IL, USA) was used to conduct statistical tests on the kinematics data during the lumbar flexion-extension. Statistically significant differences among the three groups were tested using a one-way analysis of variance with the level of statistical significance set at 0.05. Tukey’s correction was used for multiple comparisons.
3. Results The lumbar flexion angle and lumbar repositioning error showed statistically significant differences among groups. The mean flexion angles of the lumbar spine during the task in the three groups are shown in Table 2. The lumbar flexion angle of the LBP group with flexion pain was significantly greater than that of the control group or the LBP group with extension pain (P < 0.05). Table 3 shows the repositioning error of the sagittal angle in the lumbar spine (the difference in flexion angle between the standing and re-standing sections). The repositioning error of the lumbar spine, was significantly greater in the LBP group with flexion pain than in the LBP group with extension pain (P < 0.05).
4. Discussion In this study, we compared the lumbar flexion angle and lumbar spine repositioning error during a lumbar flexion-extension task in LBP patients with differing pain characteristics. The lumbar flexion angle was significantly greater in the LBP group with flexion pain compared with the control group and the LBP group with extension pain. The difference of only approximately 2 was shown in the total average value because the values of standard deviations were large. Larger differences were actually shown when the values were reviewed by subject. Despite the large standard deviations, the P value of the statistical results proves that the differences between the groups are significant. The spinal muscles do not only function by voluntary contractions; they are also controlled by ligamentmuscle reflexes [23,25]. A ligament-muscle reflex is observed when stimulation of a mechanoreceptor in the spinal ligaments affects the activation pattern of paraspinal muscles [24]. Stretching or deformation of supraspinous or intraspinous ligaments stimulates mechanoreceptors, activating the paraspinal muscles via neural control to prevent spinal instability [16]. However, ligament overloading by muscular overstretching can cause spinal muscle spasms and even permanent damage to the ligament [1]. Changes in the flexibility of the spine are important causes of changes in this neuromuscular stabilizing system [21]. Under
M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error
higher flexibility conditions, the passive elements undergo lengthening, and the reduced tension results in insufficient stretching stimulus to the central nervous system [6]; thus, changes in proprioception in the lumbar segment can occur [21]. The results in the LBP group with symptoms associated with lumbar flexion in this study demonstrated increased lumbar flexion during the lumbar flexion-extension task. Furthermore, this group showed greater repositioning error between the standing and re standing sections compared with the control group and the LBP group with symptoms associated with lumbar extension. Higher repositioning error is related to decreased joint proprioception [9, 22]. A proprioceptive deficit in the lumbar spine, in turn, is associated with lumbar hypermobility because delayed neuromuscular reflexes occur too late to protect against excessive lumbar movement [21]. The results of this study reveal differing characteristics in LBP subjects with different symptoms (i.e., LBP associated with lumbar flexion vs. LBP associated with lumbar extension). The lack of specific, objective diagnostic examinations in mechanical LBP makes a specific therapeutic approach difficult. Based on this research, we suggest that LBP patients with symptoms associated with lumbar flexion were predisposed to lumbar hypermobility with lumbar pain and moreover had increased repositioning errors in the lumbar spine due to impaired proprioception. A therapeutic program is needed to limit lumbar hypermobility, facilitate proprioception, and allow stabilization, with strengthening of lumbar segments in LBP patients with symptoms associated with lumbar flexion, but not in LBP patients with symptoms associated with lumbar extension. In modern society, computer work is clearly the most threatening element that causes low back pain [15,29]. Since the causes of low back pain are diverse, detailed classification of low back pain only in computer workers is necessary. In particular, this study measured low back pain in young low back pain patients that correspond to computer generations in Korea now. Although it is difficult to classify them into chronic patients given their ages, they may show tendencies of being chronic in low back pain because they have been exposed to computers since their childhood. This study was conducted so as to be proactive. That is, to be prepared for the possibility of young computer workers in Korea to develop chronic low back pain. It is hoped that the results of this study will be helpful in preventing low back pain in young computer workers in Korea.
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5. Conclusions This study suggests that lumbar hypermobility occurred and proprioception in the lumbar segment was decreased in people with LBP associated with lumbar flexion compared with people with LBP associated with lumbar extension. We also suggest that measurement of lumbar repositioning error using a flexionextension test would be a more effective evaluation method in people with LBP associated with lumbar flexion than in people with LBP associated with lumbar extension.
Acknowledgements This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2012R1A1B400 1058).
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Andersson GB. Epidemiology of low back pain. Acta Orthop Scand Suppl. 1998; 281: 28-31. Descarreaux M, Lafond D, Jeffrey-Gauthier R, Centomo H, Cantin V. Changes in the flexion relaxation response induced by lumbar muscle fatigue. BMC Musculoskelet Disord. 2008; 9: 10. Fairbank JC, Pynsent PB. The Oswestry Disability Index. Spine. 2000; 25: 2940-2952. Gombatto SP, Norton BJ, Scholtes SA, Van Dillen LR. Differences in symmetry of lumbar region passive tissue characteristics between people with and people without low back pain. Clin Biomech. 2008; 23: 986-995. Harris-Hayes M, Sahrmann SA, Van Dillen LR. Relationship between the hip and low back pain in athletes who participate in rotation-related sports. J Sport Rehabil. 2009; 18: 60-75. Hashemirad F, Talebian S, Hatef B, Kahlaee AH. The relationship between flexibility and EMG activity pattern of the erector spinae muscles during trunk flexion-extension. J Electromyogr Kinesiol. 2009; 19: 746-753. Lehman GJ. Biomechanical assessments of lumbar spinal function. How low back pain sufferers differ from normals. Implications for outcome measures research. Part I: Kinematic assessments of lumbar function. J Manipulative Physiol Ther. 2004; 27(1): 57-62. Leinonen V, Maatta S, Taimela S, Herno A, Kankaanpaa M, Partanen J, Kansanen M, Hanninen O, Airaksinen O. Impaired lumbar movement perception in association with postural stability and motor-and somatosensory-evoked potentials in lumbar spinal stenosis. Spine. 2002; 27: 975-983. Lephart S, Fu F. Proprioception and neuromuscular control in joint stability. Champaign, USA: Human Kinetics, 2000.
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Machado LAC, Maher CG, Herbert RD, Clare H, McAuley JH. The effectiveness of the McKenzie method in addition to first-line care for acute low back pain: A randomized controlled trial. BMC Med. 2010; 8: 10. [11] McKenzie RA, editor. The lumbar spine: Mechanical diagnosis and therapy. Waikanae, New Zealand: Spinal Publications, 1981. [12] McKenzie RA, May S, editors. The lumbar spine – mechanical diagnosis and therapy. 2nd ed. Waikanae, New Zealand: Spinal Publications Limited, 2003. [13] Newcomer K, Laskowski ER, Yu B, Larson DR, An KN. Repositioning error in low back pain. Comparing trunk repositioning error in subjects with chronic low back pain and control subjects. Spine. 2000; 25(2): 245-250. [14] O’Sullivan PB, Burnett A, Floyd AN, Gadsdon K, Logiudice J, Miller D, et al. Lumbar repositioning deficit in a specific low back pain population. Spine. 2003; 28(10): 1074-1079. [15] O’Sullivan PB, Mitchell T, Bulich P, Waller R, Holte J. The relationship beween posture and back muscle endurance in industrial workers with flexion-related low back pain. Man Ther. 2006; 11: 264-271. [16] Panjabi MM. Clinical spinal instability and low back pain. J Electromyogr Kinesiol. 2003; 13: 371-379. [17] Parkhurst TM, Burnett CN. Injury and proprioception in the lower back. J Orthop Sports Phys Ther. 1994; 19: 282-295. [18] Petersen CM, Zimmermann CL, Cope S, Bulow ME, EwersPanveno E. A new measurement method for spine reposition sense. J Neuroeng Rehabil. 2008; 5: 9. [19] Phillips JA, Forrester B, Brown KC. Low back pain: prevention and management. AAOHN J. 1996; 44: 40-53. [20] Sahrmann S, editor. Diagnosis and treatment of movement impairment syndromes. New York, USA: Mosby, 2002.
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Work 51 (2015) 223–228 DOI 10.3233/WOR-141856 IOS Press
Comparison of the lumbar flexion angle and repositioning error during lumbar flexion-extension in young computer workers in Korea with differing back pain Min-Hee Kima and Won-Gyu Yoob,∗ a
b
Institute of Health Science, Yonsei University, Wonju, Korea Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, Gimhae, Korea
Received 11 April 2013 Accepted 23 December 2013
Abstract. BACKGROUND: Differences in LBP symptoms are particularly important with regard to the controversy over repositioning error because there can be considerable variation in the pattern of LBP symptoms in a heterogeneous LBP group. For this reason, several researchers have suggested that a study of subdivided LBP types is needed. Indeed, some recent studies have attempted to differentiate LBP subgroups. OBJECTIVE: This study used a comparative cross-sectional design to compare the lumbar flexion angle and repositioning error between people with and without LBP during a lumbar flexion-extension task. METHODS: The subjects were divided into three groups: a control group of 13 asymptomatic subjects, 13 LBP subjects with L4-5 pain associated with lumbar flexion, and 13 LBP subjects with L4-5 pain associated with lumbar extension. The subjects performed a lumbar flexion-extension task. Joint kinematics on the lumbar flexion angle and lumbar spine repositioning error were measured using a 3-D motion capture system. RESULTS: The lumbar flexion angle of the LBP group with flexion pain was significantly greater than that of the asymptomatic group and the LBP group with extension pain. The difference in lumbar repositioning error was significantly greater in the LBP group with lumbar flexion pain than in the asymptomatic group. CONCLUSIONS: This study suggests that lumbar hyper-mobility occurred and proprioception of the lumbar segment was decreased in people with LBP associated with lumbar flexion compared with people with LBP associated with lumbar extension. We also suggest that a lumbar repositioning error measurement using the lumbar flexion-extension test may be a more effective evaluation method in people with LBP associated with lumbar flexion than in those with LBP associated with lumbar extension. Keywords: Hyper-mobility, low back pain, proprioception, repositioning error
1. Introduction
∗ Corresponding author: Won-Gyu Yoo, Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, 607 Obangdong, Gimhae, Gyeongsangnamdo 621-749, Korea. Tel.: +82 55 320 3994; Fax: +82 55 329 1678; E-mail: [email protected].
Recently, an association between LBP and prolonged posture, specifically prolonged sitting, has been reported [27]. Remaining seated for long periods of time can cause special problems for the spine, circulation, muscles, and joints [15]. Phillips et al. [19] stated that the sitting position is a potent risk factor for LBP.
c 2015 – IOS Press and the authors. All rights reserved 1051-9815/15/$35.00
224
M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error
Prolonged sitting posture is a risk factor for LBP continues. It may be that prolonged sitting should not be encouraged in LBP patients [15,19]. Panjabi [16] suggested that the stabilizing systems of the spine consist of passive spinal structures, active spinal muscles, and neural control. According to this theory, increased lumbar spine motion in low back pain (LBP) patients indicates inappropriate control of the neuromuscular system [27]. Lumbar spine movements and alignment patterns are provided by active muscles and passive ligaments and control a large proportion of spinal stability [2,29]. Mechanoreceptors in the spine provide proprioceptive information for structures including passive ligaments. Stretching or deformation of supraspinous or intraspinous ligaments stimulates the mechanoreceptors, and the paraspinal muscles are then activated via neural control to facilitate spinal stability [24]. Thus, proprioceptive information from mechanoreceptors may be important in controlling lumbar spine motion [8,14]. Proprioception has been regarded as necessary for body movement control and is important in diagnosing motor-control impairment [18]. Proprioception provides awareness and determines the position of the body in space, so it can adjust and control movement [17]. Spinal structures impaired by injury or stress can lead to impairment in movement control of the spine and in proprioception [17,18]. Proprioceptive impairment is known to result in poor stabilization of the lumbar spine, and is described as repositioning error [14,17,18]. Newcomer et al. [13] showed significantly higher repositioning error in patients with LBP during lumbar flexion. However, Parkhurst et al. [17] reported no correlation between LBP and repositioning error, and some researchers have reported no proprioceptive impairment in people with LBP. It is worth considering the reasons for these inconsistent results with regard to repositioning error in LBP studies. The inconsistent findings may be due to subject characteristics, variation in experimental conditions, or differences in LBP symptoms. Differences in LBP symptoms are particularly important with regard to the controversy over repositioning error because there can be considerable variation in the pattern of LBP symptoms in a heterogeneous LBP group [4]. The results found in subjects complaining of one pattern of LBP symptoms in a heterogeneous LBP group could be counterbalanced by opposite results found in subjects complaining of another pattern of LBP symptoms [26]. To address these concerns, several researchers have suggested that a study of subdivided LBP types is needed.
Indeed, some recent studies have attempted to differentiate LBP subgroups [4,5]. Korean household Internet and computer distribution rates have rapidly increased since 2000 and Korea has now been identified as a country with the highest distribution of Internet and computers in the world with the rates exceeding 80% [30]. The conglomerates and public companies in Korea use 1 computer per worker [30]. A review of the rates of use of the Internet using computers by age indicated that teenagers and people in their 20s use the Internet the most frequently [30]. Therefore, as of 2013, Korean males and females in their 20s and 30s are thought to be exposed the most to diseases related to computers. Therefore, the characteristics of low back pain in young computer workers in Korea that correspond to these age groups should be classified. Thus, in the present study, we compared lumbar movement, specifically, lumbar flexion angle and lumbar spine repositioning error, during a lumbar flexion-extension task in young computer workers in Korea between LBP subgroups with differing back pain symptoms using 3-D motion analysis.
2. Methods 2.1. Participants The subjects were divided into three groups: a control group of 13 asymptomatic subjects (8 males, 5 females), 13 LBP subjects with L4-5 pain associated with lumbar flexion (8 males, 5 females), and 13 LBP subjects with L4-5 pain associated with lumbar extension (8 males, 5 females). They were young computer workers in Korea with LBP who sat for more than 4 h/ day at work. The LBP groups included mechanical LBP without radiating pain. Exclusion criteria were 1) a history of spinal or leg surgery, 2) a medical diagnosis of ankylosing spondylitis, 3) a medical diagnosis of rheumatoid arthritis, 4) a medical diagnosis of degenerative disease, 5) a medical diagnosis of other neurological disorders, or 6) visually determined severe kyphosis or scoliosis. Twenty-six subjects with nonspecific LBP for at least 3 months’ duration were recruited from the local community after meeting the inclusion and exclusion criteria. The subjects were classified based on clinical examinations. The LBP subjects with lumbar pain associated with lumbar flexion and extension were classified according to the methods proposed by McKenzie [11] and Sahrmann [20]. The McKenzie ap-
M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error
proach evaluates LBP based on the patient’s response to standardized mechanical loading strategies [11]. The Sahrmann approach classifies movement system impairment based on a kinesiopathological approach and movement directions and symptoms associated with LBP [20]. The common assessment concept identifies the directional preference that provokes or alleviates LBP symptoms. Using these classification systems, the patients were classified into two LBP subgroups: one in which lumbar flexion caused more symptoms and the other in which lumbar extension caused more symptoms [11,12,20]. The movement tests related to lumbar flexion symptoms included trunk flexion while standing, hip and knee flexion in the supine position, backward rocking in the quadruped position, and lumbar flexion while sitting. The symptoms usually increased and became peripheralized with repeated flexion and usually decreased and became centralized with repeated extension of the lumbar spine. The movement tests related to lumbar extension symptoms included trunk extension while standing, trunk and hip extension in the prone position, forward rocking in the quadruped position, and shoulder flexion in the supine position. The symptoms usually increased and became peripheralized with repeated extension and usually decreased and became centralized with repeated flexion of the lumbar spine. All subjects completed the self-reported Oswestry Disability Index [3]. Table 1 summarizes the characteristics of the three groups of subjects. There were no significant differences in age, height, and weight among the three groups. There was a significant difference in the Oswestry Disability Index between the controls and each LBP group (P < 0.05) and no significant difference in this index between the LBP groups with flexion and extension pain (P > 0.05). This study was approved by the Yonsei University Faculty of Health Sciences Human Ethics Committee and the subjects provided written informed consent before participating. 2.2. Kinematic data The lumbar flexion-extension task consisted of standing, flexion-extension, and re-standing sections. To record kinematic data, we used a 3-D motion capture system. The 3-D motion capture system consisted of six infrared cameras was used to record the kinematic data. The kinematic data were collected using camera sampling at 60 Hz. In total, 20 retro-reflective markers were attached at the T12 and L2 spinous pro-
225
cesses bilaterally, 3 cm lateral from the L2 spinous process, the anterior and posterior superior iliac spines, lateral femoral epicondyle, the midpoint between the anterior superior iliac spine and the lateral femoral epicondyle, the lateral malleolus, the midpoint between the lateral femoral epicondyle and the lateral malleolus, the distal head of the second metatarsal, and the posterior aspect of the calcaneus. The reflective markers were attached at these anatomical locations according to the VICON Plug-in-Gait marker placement protocol. The subjects stood with their feet separated and placed equally on the experimental floor, and static trials were recorded after placing retro-reflective markers on the subjects. The anthropometric measurements made included the height, weight, leg length, and joint width of the knee and ankle. All trials were processed with VICON Nexus software. The recorded kinematic data filtered with a Woltring filter were computed with VICON Plug-In Gait and a customized BodyLanguage model. The kinematic parameters were the flexion angle and repositioning error of the lumbar spine. The lumbar flexion angle was defined as the sagittal angular displacement between the mean angle of the middle 1 second in the standing phase and the mean angle of the middle 1 second in the maximum lumbar flexion of the flexion-extension phase. The repositioning error of the lumbar spine was defined as the difference in the mean sagittal angle of the middle 1 second between the standing and re-standing phases of the task (| mean angle in re-standing – mean angle in standing |). The kinematic data obtained during the lumbar flexion-extension task were analyzed and reported using Polygon software. 2.3. Procedures The subjects were instructed to stand with their arms hanging freely by their sides and their feet spaced slightly apart. For dynamic capture, the subjects were required to stand for 5 seconds (standing phase), to flex forward with their arms dangling freely and hold themselves in the fully flexion position for 3 seconds, and then to return to the upright position (flexionextension phase). Finally the subjects were asked to maintain an upright standing position for 5 seconds (restanding phase). The subjects performed three trials of the lumbar flexion-extension task after practicing and the mean of three trials following a metronome was used for the data analysis.
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M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error Table 1 General characteristics of the subjects Parameter Age (y) Height (cm) Weight (kg) ODIa score
Control (n = 13) 23.81 ± 2.90 171.23 ± 8.44 66.25 ± 10.26 3.04 ± 1.48
LBP with flexion pain (n = 13) 23.47 ± 2.35 173.12 ± 9.14 67.15 ± 11.09 12.53 ± 5.88∗
LBP with extension pain (n = 13) 23.79 ± 3.91 172.09 ± 8.45 66.88 ± 11.03 14.18 ± 4.27∗
p 0.901 0.323 0.287 0.000
NOTE. Values are mean ± SD. a The Oswestry Disability Index. ∗ Significant difference compared with the control group. Table 2 Lumbar flexion angle during the lumbar flexion-extension task Angle Lumbar flexion ∗ Significant
Control 47.0 ± 7.6
Mean ± SD (degrees) LBP with flexion pain 54.5 ± 6.9∗
p LBP with extension pain 46.5 ± 8.0
0.011
difference compared with the control group and LBP with extension pain. Table 3 Repositioning errorsa of the lumbar spine
Reposition error Lumbar spine
Control 1.2 ± 1.3
Mean ± SD (degrees) LBP with flexion pain 3.2 ± 1.8∗
p LBP with extension pain 2.2 ± 2.0
0.040
a Calculated
by relative displacement changes between standing and re-standing; (sagittal angle in re-standing – sagittal angle in standing). ∗ Significant difference compared with the control group.
2.4. Statistical analysis SPSS software (ver. 14.0; SPSS, Chicago, IL, USA) was used to conduct statistical tests on the kinematics data during the lumbar flexion-extension. Statistically significant differences among the three groups were tested using a one-way analysis of variance with the level of statistical significance set at 0.05. Tukey’s correction was used for multiple comparisons.
3. Results The lumbar flexion angle and lumbar repositioning error showed statistically significant differences among groups. The mean flexion angles of the lumbar spine during the task in the three groups are shown in Table 2. The lumbar flexion angle of the LBP group with flexion pain was significantly greater than that of the control group or the LBP group with extension pain (P < 0.05). Table 3 shows the repositioning error of the sagittal angle in the lumbar spine (the difference in flexion angle between the standing and re-standing sections). The repositioning error of the lumbar spine, was significantly greater in the LBP group with flexion pain than in the LBP group with extension pain (P < 0.05).
4. Discussion In this study, we compared the lumbar flexion angle and lumbar spine repositioning error during a lumbar flexion-extension task in LBP patients with differing pain characteristics. The lumbar flexion angle was significantly greater in the LBP group with flexion pain compared with the control group and the LBP group with extension pain. The difference of only approximately 2 was shown in the total average value because the values of standard deviations were large. Larger differences were actually shown when the values were reviewed by subject. Despite the large standard deviations, the P value of the statistical results proves that the differences between the groups are significant. The spinal muscles do not only function by voluntary contractions; they are also controlled by ligamentmuscle reflexes [23,25]. A ligament-muscle reflex is observed when stimulation of a mechanoreceptor in the spinal ligaments affects the activation pattern of paraspinal muscles [24]. Stretching or deformation of supraspinous or intraspinous ligaments stimulates mechanoreceptors, activating the paraspinal muscles via neural control to prevent spinal instability [16]. However, ligament overloading by muscular overstretching can cause spinal muscle spasms and even permanent damage to the ligament [1]. Changes in the flexibility of the spine are important causes of changes in this neuromuscular stabilizing system [21]. Under
M.-H. Kim and W.-G. Yoo / Comparison of the lumbar flexion and repositioning error
higher flexibility conditions, the passive elements undergo lengthening, and the reduced tension results in insufficient stretching stimulus to the central nervous system [6]; thus, changes in proprioception in the lumbar segment can occur [21]. The results in the LBP group with symptoms associated with lumbar flexion in this study demonstrated increased lumbar flexion during the lumbar flexion-extension task. Furthermore, this group showed greater repositioning error between the standing and re standing sections compared with the control group and the LBP group with symptoms associated with lumbar extension. Higher repositioning error is related to decreased joint proprioception [9, 22]. A proprioceptive deficit in the lumbar spine, in turn, is associated with lumbar hypermobility because delayed neuromuscular reflexes occur too late to protect against excessive lumbar movement [21]. The results of this study reveal differing characteristics in LBP subjects with different symptoms (i.e., LBP associated with lumbar flexion vs. LBP associated with lumbar extension). The lack of specific, objective diagnostic examinations in mechanical LBP makes a specific therapeutic approach difficult. Based on this research, we suggest that LBP patients with symptoms associated with lumbar flexion were predisposed to lumbar hypermobility with lumbar pain and moreover had increased repositioning errors in the lumbar spine due to impaired proprioception. A therapeutic program is needed to limit lumbar hypermobility, facilitate proprioception, and allow stabilization, with strengthening of lumbar segments in LBP patients with symptoms associated with lumbar flexion, but not in LBP patients with symptoms associated with lumbar extension. In modern society, computer work is clearly the most threatening element that causes low back pain [15,29]. Since the causes of low back pain are diverse, detailed classification of low back pain only in computer workers is necessary. In particular, this study measured low back pain in young low back pain patients that correspond to computer generations in Korea now. Although it is difficult to classify them into chronic patients given their ages, they may show tendencies of being chronic in low back pain because they have been exposed to computers since their childhood. This study was conducted so as to be proactive. That is, to be prepared for the possibility of young computer workers in Korea to develop chronic low back pain. It is hoped that the results of this study will be helpful in preventing low back pain in young computer workers in Korea.
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5. Conclusions This study suggests that lumbar hypermobility occurred and proprioception in the lumbar segment was decreased in people with LBP associated with lumbar flexion compared with people with LBP associated with lumbar extension. We also suggest that measurement of lumbar repositioning error using a flexionextension test would be a more effective evaluation method in people with LBP associated with lumbar flexion than in people with LBP associated with lumbar extension.
Acknowledgements This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (No. 2012R1A1B400 1058).
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