231

Journal of Back and Musculoskeletal Rehabilitation 27 (2014) 231–237 DOI 10.3233/BMR-130442 IOS Press

Influences of posterior-located center of gravity on lumbar extension strength, balance, and lumbar lordosis in chronic low back pain Dae-Hun Kima,∗ , Jin-Kyu Parkb and Myeong-Kyun Jeongc a

Department of Physical Therapy, Kyungdong University, Goseong-gun, Kangwon-do, Korea Department of Neurosurgery, Goodspine Hospital 470-4, Jangdang-Dong, Pyeongtaek-Si, Gyeonggi-Do, Korea c Institute of Rehabilitation Therapy, Hongik Hospital, Yangcheon-gu, Seoul, Korea b

Abstract. BACKGROUND DATA: In patients with chronic low back pain, the center of gravity (COG) is abnormally located posterior to the center in most cases. OBJECTIVE: The purpose of this study was to examine the effects of posterior-located COG on the functions (lumbar extension strength, and static and dynamic balance) and structure (lumbar lordosis angle and lumbosacral angle) of the lumbar spine. MATERIAL AND METHODS: In this study, the COG of chronic low back pain patients who complained of only low back pain were examined using dynamic body balance equipment. A total of 164 subjects participated in the study (74 males and 90 females), and they were divided into two groups of 82 patients each. One group (n = 82) consisted of patients whose COG was located at the center (C-COG); the other group (n = 82) consisted of patients whose COG was located posterior to the center (P-COG). The following measures assessed the lumber functions and structures of the two groups: lumbar extension strength, moving speed of static and dynamic COGs, movement distance of the static and dynamic COGs, lumbar lordosis angle, and lumbosacral angle. The measured values were analyzed using independent t-tests. RESULTS: The group of patients with P-COG showed more decreases in lumbar extension strength, lumbar lordosis angle, and lumbosacral angle compared to the group of patients with C-COG. Also this group showed increases in moving speed and movement distance of the static COG. However, there were no differences in moving speed and movement distance of the dynamic COG between the two groups. CONCLUSIONS: These findings suggest that chronic LBP patients with P-COG have some disadvantages to establish lumbar extension strength and static and dynamic balance, which require specific efforts to maintain a neutral position and to control posture. Keywords: Balance, low back pain, lumbopelvic neutralization

1. Introduction The lumbar spine acts like a muscular corset that stabilizes the trunk regardless of the movement of the extremities. In a normal person, balance is the ability to ∗ Corresponding author: Dae-Hun Kim, Department of physical therapy, Kyungdong University, Toseong-myeon Bongpo-4gil 46, Goseong-gun, Kangwon-do, Korea. Tel.: +82 33 639 0227; Fax: +82 33 639 0239; E-mail: [email protected].

maintain the center of gravity (COG) with minimum swaying on a supporting base [2]. However, in the case of chronic LBP patients, the blocking of two physiomechanisms causes balance disability. First, changes in proprioception can cause somatosensory disabilities. Second, decreases in muscle strength and motor coordination ability can lead to a decline in motor response. Therefore, decreased balancing ability can cause abnormal posture response patterns [3], response time delay [4], and unstable balance [5].

c 2014 – IOS Press and the authors. All rights reserved ISSN 1053-8127/14/$27.50 

232

D.-H. Kim et al. / Influences of posterior-located center of gravity

Compared to normal persons, the loss of balance ability in chronic low back pain patients induces sway in the COG in standing postures [6]. Therefore, these patients need excessive muscle activities in order to recover stable postures. The compensatory actions necessary to maintain the displaced standing posture of the pelvis, increase pressure on the facet joint and the vertebral joint. This increases lumbar instability, aggravating low back pain [7,8]. Changes in the COG affect trunk muscle strength and endurance [9] and reduce the power of the kinetic chain of the trunk [10,11]. Na et al. [12] indicated that trunk muscle weakness was associated with pelvic variables, thereby affecting changes in the lumbar lordosis angle and the lumbosacral angle. On the other hand, according to Mientjes et al. [13] the COG was not located posterior to the center in every chronic low back patient. However, Byl and Sinnott [14] indicated that the COG in many chronic low back pain patients was located posterior to the center. Recently, a study conducted by Yoon [15] reported that the results of analyses of the weight distributions of normal persons and chronic low back pain patients showed that chronic low back pain patients tended to concentrate their weight on their heels. When the COG is thus centered, impact is not sufficiently absorbed when the heels touch the ground during gait, which may cause dysfunction of the knee joint, hip joint, or spine. Clinically, changes in the COG of chronic low back pain patients are compensatory strategies to maintain stable postures, which have diverse effects on the body. However, few previous studies have investigated the function of the lumbar spine in stabilizing movement when the COG located posterior to the center. In these patients, the lumbar spine endures pressure and shearing force from the upper extremities while controlling load transfer to the lower extremities. Therefore, this study investigated changes in lumbar extension strength, static and dynamic balance, the lumbar lordosis angle, and the lumbosacral angle in chronic low back pain patients whose COG is located posterior to the center.

2. Materials and methods 2.1. Subjects A clinical trial study was conducted with nonprobability sampling. In this study, patients who visited the hospital because of chronic low back pain that had

Table 1 Subject characteristics Parameter Age (yrs) Weight (kg) Height (cm)

Subjects (N = 164) C-COG P-COG 47.28 ± 13.29 47.80 ± 14.39 62.42 ± 11.30 63.73 ± 10.03 163.30 ± 9.97 163.43 ± 8.71

Values are Mean ± SD. C-COG: Center-COG, P-COG: PosteriorCOG.

persisted for at least three months were divided into two groups of 82 patients (37 males, 45 females). One group (n = 82) consisted of patients whose COG was located at the center (C-COG) and the other group (n = 82) consisted of those whose COG was located posterior to the center (P-COG). All patients had been diagnosed with chronic LBP by a neurosurgeon, but they had no balance disabilities caused by neurological problems, no vestibular organ problems, and no history of surgery. The ethics committee of the hospital approved this study. Only subjects who agreed to the terms and conditions of the study participated in the experiment. The general characteristics of the patients are shown in Table 1. 2.2. Procedure For the clinical study, the participants stood on the force platform of the I-Balance (CyberMedic Inc., Jeonbuk, Korea) in bare feet for ten seconds while they watched the center of the front monitor connected to the platform. Based on the results, the participants were divided into a group of patients with a centerlocated COG at 0 deg on the y coordinate, and another group of patients with a posterior-located COG at -2 deg or farther back on the y coordinate. For all participants, lumbar extension strength, speed and distance of static and dynamic COG, lumbar lordosis angle and lumbosacral angle were measured to examine the functions and structural stability of the lumbar spine. 2.3. Measurements 2.3.1. Lumbar extension strength Lumbar extension strength was measured using the Medx lumbar extension machine (Medx96 Inc., Ocala Florida, USA) (Fig. 1). This machine uses isometric exercises and measures lumbar muscle strength. To perform the measurement, the subject was in sitting posture, and the lower body and pelvis were fixed to control any compensation. The joint range of motion of the subject’s lumbar region was set at seven angles

D.-H. Kim et al. / Influences of posterior-located center of gravity

233

Table 2 Comparison of lumbar extension strengths, static and dynamic COG speed and distances, lumbar lordosis and lumbosacral angle in two groups Condition COG speeds (deg/sec)

Static Dynamic

COG distances (deg)

Static Dynamic

EO EC EO EC EO EC EO EC

LES (ft lbs) LLA (◦ ) LA (◦ )

C-COG Mean ± SD 0.18 ± 0.16∗ 0.22 ± 0.16† 0.32 ± 0.45 1.56 ± 1.46

P-COG Mean ± SD 0.25 ± 0.16 0.30 ± 0.19 0.34 ± 0.21 1.53 ± 1.10

483.03 ± 174.53∗ 585.98 ± 167.66∗ 708.93 ± 224.03 1263.42 ± 686.42 5387.92 ± 2488.77∗ 23.98 ± 8.74∗ 15.86 ± 6.26∗

555.93 ± 198.22 680.57 ± 355.70 722.86 ± 190.99 1370.74 ± 539.55 4686.9 ± 1857.04 21.09 ± 9.38 13.87 ± 4.36

∗ p < 0.05, † p < 0.01. C-COG: Center-COG, P-COG: Posterior-COG. EO: eye open, EC:eye closed, LES: Lumbar Extension Strengths. LLA: Lumbar Lordosis Angle, LA: Lumbosacral Angle.

structed. When the eyes are open, both the somatosensory system and the visual and vestibular system are measured. When the eyes are closed, the subject’s ability to control posture with eyes closed was measured. Using the visual feedback mechanism, the subject observes own COG movement in four conditions while maintaining COG on the center of the coordinates. The four conditions are as follows: 1) firm/eyes open, 2) firm/eyes closed, 3) foam/eyes open, and 4) foam/eyes closed. In all four conditions, the sway angles of COG at the front, back, left, and right of the body were displayed for 10 seconds. COG sway velocity/sec was measured digitally by using the counting formula of the I-Balance machine. Each test was repeated three times, and the average COG sway velocity was then calculated. Fig. 1. Measurement of the lumbar extension strengthen. (Colours are visible in the online version of the article; http://dx.doi.org/ 10.3233/BMR-130442)

(0◦ , 12◦ , 24◦ , 36◦ , 48◦ , 60◦ , 72◦ ). The muscle strength was measured by the maximum power shown on every angle. The unit of measurement was in ft. lbs. The muscle strength value of the result is the total area of the graph, which shows the values of the seven angles in ft. lbs. 2.3.2. Static and dynamic COG speeds To reduce the resistance to the minimum when the subject is on the I-Balance dynamic body balance device, the subject stands on a firm plate (for static balance) or a foam pad (for dynamic balance) in bare feet with legs about 30 cm apart. With the arms folded, the subject stares at the monitor or closes the eyes, as in-

2.3.3. Static and dynamic COG distances The method used to measure COG distance was the same as that used to measure static and dynamic COG speed. The swayed distance of COG to the center of the coordinates was calculated as a percentage by using the counting formula of the I-Balance machine. Each test was repeated three times, and the average COG movement distance was then calculated. 2.3.4. Lumbar lordosis angle and lumbosacral angle To perform the radiography of the lumbosacral region side, the patient stood in the lateral position, and Dong Kang ACC-630R was used. The Propst-Proctor and Bleck [16] method was used to measure the lumbar lordosis angle between the upper endplate of the first lumber vertebra and the lower endplate of the fifth lumbar vertebra (Fig. 2). The Ferguson [17] method was

234

D.-H. Kim et al. / Influences of posterior-located center of gravity

Fig. 2. Measurement of the Lordosis angle.

Fig. 3. Measurement of the Lumbosacral angle.

used to measure the lumbosacral angle between the upper endplate of the first sacrovertebra. The horizontal plate was then applied (Fig. 3).

The distances and speeds of movement in the static and dynamic COG of the two groups were measured under four measurement conditions. The results indicated that the distances and speeds of movement in the static and dynamic COG significantly decreased in the P-COG group compared to the C-COG group when the patient stood with eyes open or eyes closed on a firm plate (static condition). However, there were no significant differences between the two groups when the patient stood with eyes open or eyes closed on the foam pad (dynamic condition). Finally, the results of measurement of the lumbar lordosis and the lumbosacral angles of the two groups indicated that the angles significantly decreased in the P-COG group compared to the C-COG group.

2.4. Statistical analysis Windows SPSS 12.0 was used to process the study data. The body characteristics of the subjects in the CCOG group and the P-COG group were calculated as average and standard deviations. Data were processed using an independent t-test to compare the lumbar extension strength, speed and distance of COG, as well as the values of the lumbar lordosis and lumbosacral angles. The significance level was set at p = 0.05.

3. Results 4. Discussion The means and standard deviations of lumbar extension strength, distances of the movement of the static and dynamic COG, lumbar lordosis angles, and lumbosacral angles in the two groups are presented in Table 1. The lumbar extension strength of the group of patients with the P-COG and that of the group of patients with the C-COG were compared. The results showed that lumbar extension strength significantly decreased in the P-COG group compared to the C-COG group.

The results of this study indicated that in chronic low back pain patients whose COG was located posterior to the center, the structural stability and functions of the lumbar spine were affected more adversely than in patients whose COG was located at the center. The vertebral column sustains weight. When a person is standing, about 84% of the weight is delivered through the anterior structure, which consists of the vertebral body and the intervertebral disc. About 16%

D.-H. Kim et al. / Influences of posterior-located center of gravity

of the weight is delivered through the posterior structure, which consists of the facet joint and the vertebral lamina [7,8]. When gravity passes through the posterior or anterior lumbar region, changes in the body cause the COG to be at the center of the body with consistent flexion force [18]. Using the I-Balance, this study measured lumbar extension strength, speed, and distance of COG, as well as changes in lumbar lordosis angles and lumbosacral angles for chronic LBP patients with center-located and posterior-located COG. The extension strength of the P-COG group was 4686.9 ± 1857.04 ft. lbs., which was more decrease compared to 5878.2 ± 2488.77 ft. lbs. in the C-COG group (p < 0.05). An LBP patient uses postural compensations or avoids activities to reduce pain. Abnormal postures and chronic habits can change the structure of ligaments and muscles that control weight loading [19]. In particular, they can weaken lumbar extension strength [20,21]. The weakened lumbar extension muscle can cause pain and repeated damage in the lumbar region. Because of the decreased stability of the lumbar region, which sustains the spine and allows smooth adjustment and coordination of the neuromuscular system, the neutral position of the spine is compromised [22]. Therefore, the fact that the extension strength of P-COG was reduced more than that of C-COG seems plausible. Horak [23] reported that factors affecting balance control include vision, proprioceptive sense, ear and vestibular function, cerebellar function, location of feet on the platform, discrepancy in leg lengths, muscle strength in both legs, and musculoskeletal diseases. Generally, a person with LBP suffers loss of balance ability [7,24]. Furthermore, compared to a normal person, his/her postural sway increases in the standing posture [24,25]. His/her medial and lateral postural sway also increase [13]. However, in this study, with eyes closed and open in static balance, the P-COG group’s results for static and dynamic COG speed and distance were more decrease than those of the C-COG group (p < 0.05). Decline in muscle functions caused by LBP or injuries to the skeleton or ligaments can decrease the proprioceptive sense or quality of motion. However, in the C-COG group, COG showed little change. Moreover, lumbar extension strength loss was low and static balance ability on the firm plate was less affected, which was similar to the results of Mientjes and Frank [13] and Byl and Sinnott [14]. However, dynamic balance showed no significant difference (p > 0.05) in all the condition with the eyes open or closed. Regard-

235

ing static and dynamic COG speed and distance, both groups showed large postural sways when the floor was instable, and a high level of balance was needed. Benneil and Goldie [26] reported that inappropriate position input of the ground or gravity to the trunk can lower the somatic sense. Gill and Callaghan [27] reported that the inappropriate proprioceptive sense of a LBP patient is delivered to the central nerve system, thus decreasing the ability to control posture. The trunk muscles and ligaments are the main dynamic stabilizing structure of the lumbar, but the proprioceptive receptor can be damaged in the muscles and ligaments of LBP patients [28–31]. Therefore, because there is an important relationship between the level of proprioceptive sense and the occurrence of LBP, treatment should aim at the recovery of proprioceptive sense in the lumbar region. LBP is affected greatly by the kinds of activities or postures maintained by the patient for a long time [32]. Clinically, sustained activity is related to the posture of the sagittal plane and the spinal curve, so the alignment of the spine on the sagittal plane is an important factor [33]. In advanced research on lumbar lordosis and lumbosacral angles, Kim et al. [34] reported that the average lumbar lordosis angle and lumbosacral angle of normal persons 20 to 29 years old are 33.65 ± 1.30◦ and 48.02 ± 1.05◦ , respectively. However, Lee et al. [35] reported that analysis of the sagittal plane alignment of the normal spine showed that the shapes of spinal curves are unique and various, so it is difficult to define normal or average values. In advanced research on the lumbar lordosis of LBP patients, some researchers reported that lumbar lordosis occurred more often in the P-COG group than in the CCOG group [36,37]. Others reported that lumbar lordosis decreased in the P-COG group [12] or that there was no significant difference in lumbar lordosis between the two groups [34]. Hence, the results of previous studies are contradictory. However, the present study found that the lumbar lordosis and lumbosacral angle of both the C-COG and the P-COG groups were smaller than the normal angle in Kim et al. [34]. However, the amount of decrease was bigger in the P-COG group than in the C-COG group (p < 0.05). Byl and Sinnott [14] explained that a normal person controls COG by using the foot joints. However, because their COG was displaced, the chronic LBP patients controlled COG by using hip joint and lumbar flexion motions. Therefore, when subjects in the P-COG group adjusted their postural control, the lumbar extension muscle was weakened and the posterior

236

D.-H. Kim et al. / Influences of posterior-located center of gravity

tilt of the pelvis increased, thus decreasing the lumbar lordosis and lumbosacral angles. Conclusively, we found that if the COG moved backwards, the extension strength, static and dynamic balance control ability, lumbar lordosis and lumbosacral angle decreased. However, this study has several limitations. First, because the study’s criteria specified patients with diagnoses limited to chronic low back pain, patients with diverse diagnoses were excluded. In addition, because the patients’ symptoms were limited to low back pain, patients with neurologic symptoms were not assessed. Furthermore, because the daily activities and individual motor abilities of the patients in the experimental groups were not controlled, diverse variables appeared. Therefore, based on the limitations of this study, the diverse lumbar functions of patients with the COG located anterior, posterior, left or right of the center should be assessed. Based on this study, studies should be conducted with a view to the treatment of dislocated COG by diverse rehabilitation exercises.

5. Conclusion Among chronic LBP patients, those with P-COG were more unstable in terms of lumbar extension strength and static and dynamic balance. Therefore, because these patients need the ability to maintain a neutral position and to control posture as much as possible, we recommend efficient COG control training and proprioceptive sense exercises.

Acknowledgment We extend our gratitude to the subjects who participated in this study.

References [1] [2]

[3]

[4]

[5]

Akuthota V, Nadler SF. Core strengthening. Arch Phys Med Rehabil 85(2004), 86-92. Nicholas DS, Miller L, Colby LA. Sitting balance: its relation to function in individuals with hemispheres. Arch Phys Med Rehabil 77(1996), 865-869. Mientjes ML, Frank JS. Balance in chronic low back pain patients compared to healthy people under various conditions in upright standing. Clinical Biomechanics 14(1999), 710-716. Hodges PW, Richardson CA. Delayed postural contraction of transversus abdominis in low back pain associated with movement of the lower limb. J Spinal Disord 11(1998), 46-56. Newcomer KL, Laskowski ER, Yu B. Differences in repositioning error among patients with low back pain compared with control subjects. Spine 25(2000), 2488-2493.

[6]

Kantor E, Poupard L, Le Bozec S, Bouisset S. Does body stability depend on postural chain mobility or stability area? Neurosci Lett 308(2001), 128-132. [7] Adams MA, Hutton WC. The effect of posture on the role of the apophysial joints in resisting intervertebral compressive forces. J Bone Joint Surg 62(1980), 358-362. [8] Dunlop RB, Adams MA, Hutton WC. Disc space narrowing and lumbar facet joints. J Bone Joint Surg Br 66(1984), 706710. [9] Lariviere C, Bilodeau M, Forget R. Poor back muscle endurance is related to pain catastrophizing in patients with chronic low back pain. Spine 27(2010), 1178-1186. [10] Pery, J. Gait analysis: Normal and pathological function. Thorofare, NJ: Slack 1992, 87-88. [11] Powers, CC. The influence of altered lower extremity kinematics on patellofemoral joint dysfunction: A theoretical perspective. J Orthop Sports Phys Ther 33(2003), 639-464. [12] Na YM, Kang SW, Bae HS. The analysis of spinal curvature in low back pain patients. J of Korean Acad of Rehab Med 20(1996), 669-674. [13] Mientjes MI, Norman RW, Wells RP, McGell SM. Assessment of an EMG-Based Method for Continuous Estimates of Low Back Compression during Asymmetrical Occupational Tasks. Ergonomics 42(1999), 868-879. [14] Byl NN, Sinnott PL. Variation in balance and body sway in middle-aged adults. Spine 16(1991), 325-330. [15] Yoon JS. The relation study of weight distribution and strength of Lower extremity with and without Low back pain in middle-aged woman. Exercise Science 17(2008), 309-316. [16] Propst SL, Bleck EE. Radiographic determination of lordosis and kyphosis in normal and scoliotic children. J Pediatr orthop 3(1983), 344-346. [17] Ferguson AB. Roentgen diagnosis of extremities and spine 2nd ed. New York 1949, 147-148. [18] Donald A, Neumann DA. Kinesiology of the musculoskeletal system. Mosby 2004, 278-280. [19] Kwon HJ, Kim MJ, Choi YD. The influence in lumbosacral angle, lumbar lordosis, pelvic level and symptoms by standing lumbar traction on HIVD patients. J Korean Acad Orthopaedic Manual Physical Therapy 5(1999), 5-16. [20] Thorstensson A, Arvidson A. Trunk muscle strength and low back pain Scand. J Rehabil Med 14(1982), 69-75. [21] Risch SV, Norvell NK, Pollock ML. Lumbar strengthening in chronic low back pain patients, Physiological and psychological benefits. Spine 18(1993), 232-238. [22] Barr KP, Griggs M, Cadby T. Lumbar stabilization. Am J Phys Med Rehabil 84(2005), 473-480. [23] Horak FB. Clinical measurement of postural control in adults. Phys Ther 67(1987), 1881-1885. [24] Hamaoui A, Do MC, Bouisset, S. Postural sway increase in low back pain subjects is not related to reduced spine range of motion. Neuroscience 357(2004), 135-138. [25] Hamaoui A, Do, MC, Poupard L. Does respiration perturb body balance more in chronic low back pain subjects than in healthy subjects? Clinical Biomechanics 17(2002), 548-550. [26] Benneil KL, Goldie PA. The differential effects of external ankle support on postural control. J Orthop Sports Phys Ther 20(1994), 287-295. [27] Gill K, Callaghan M. The measurement of lumbar proprioception in individuals with and without low back pain. Spine 23(1998), 371-377. [28] Hodges P, Richardson C, Jull G. Evaluation of the relationship between laboratory and clinical tests of transversus abdominis function. Physiother Res Int 1(1996), 30-40.

D.-H. Kim et al. / Influences of posterior-located center of gravity [29]

[30]

[31]

[32] [33]

Radebold A, Cholewicki J, Panjabi MM. Muscle response pattern to sudden trunk loading in healthy individuals and in patients with chronic low back pain. Spine 25(2000), 947-954. Radebold A, Cholewicki J, Polzhofer GK. Impaired postural control of the lumbar spine is associated with delayed muscle response time in patients with chronic idiopathic low back pain. Spine 26(2001), 724-730. Yoshihara K, Nakayama Y, Fujii N. Atrophy of the multifidus muscle in patients with lumbar disk herniation: histochemical and electromyo graphic study. Orthopedics 26(2003), 493495. Cailiet R. Low back pain syndrome, 5th ed. Philadelphia, FA Davis (1995), 147-148. Hardacher JW, Robert F, Peter N, Pilip W. Radiographic

237

standing cervical segmental alignment in adult volunteers without neck symptoms. Spine 22(1997), 1472-1479. [34] Kim KW, Kim YH, Yi PG. A comparison of lumbar lordosis in asymptomatic and low back pain group. J of Korean Orthop. Assoc 30(1995), 83-88. [35] Lee CS, Oh WH, Chung SS. Analysis of the sagittal alignment of normal spines. J of Korean Orthop Assoc 34(1999), 949954. [36] Christie HJ, Kumar S, Warren SA. Postural aberration in low back pain. Arch Phys Med Rehabil 76(1995), 254-267. [37] Korovessis P, Stamatakis M, Baikousis A. Segmental roentgenographic analysis of vertebral inclination on sagittal plane in asymptomatic versus chronic low back pain patients. J of spinal disorders 12(1999), 131-137.

Copyright of Journal of Back & Musculoskeletal Rehabilitation is the property of IOS Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Influences of posterior-located center of gravity on lumbar extension strength, balance, and lumbar lordosis in chronic low back pain.

In patients with chronic low back pain, the center of gravity (COG) is abnormally located posterior to the center in most cases...
409KB Sizes 0 Downloads 0 Views