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Preliminary study of neck muscle size and strength measurements in females with chronic non-specific neck pain and healthy control subjects
Manual Therapy 15 (2010) 400e403
Contents lists available at ScienceDirect
Manual Therapy journal homepage: www.elsevier.com/math
Original article
Preliminary study of neck muscle size and strength measurements in females with chronic non-specific neck pain and healthy control subjects Asghar Rezasoltani*, Ahmadipor Ali-Reza 1, Khademi-Kalantari Khosro 1, Rahimi Abbass 1 University of Shahid Beheshti (MC), Faculty of Rehabilitation, Damavand Ave., across from Bo-Ali Hospital, 16169, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 July 2008 Received in revised form 7 February 2010 Accepted 23 February 2010
Neck muscle weakness and atrophy are two common causes of pain and disability among office workers. The aim of this study was to compare the strength of the neck extensor and flexor muscles and the size of the semispinalis capitis muscle (SECM) in patients with chronic non-specific neck pain (CNNP) and healthy subjects. Twenty female office workers (10 patients with CNNP and 10 healthy subjects) participated in this study. The strength of the neck extensor and flexor muscles was measured by an isometric device and the SECM size was measured by ultrasonography. Neck muscle strength, size of the SECM and the ratios of neck strength to body weight, neck extensor strength to SECM size, SECM size to body weight and neck flexor to extensor strength were all significantly lower in patients compared to controls (P < 0.05). In conclusion, neck strength, the size of the SECM and the ratio of neck muscle strength to SECM size appear to be useful parameters in appraising patients with CNNP. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Neck Muscle Size Strength
1. Introduction Neck pain is an increasing problem in society (Fejer et al., 2006). Chronic neck pain is one of the key factors for disability and discomfort in female office workers (Leijon et al., 2004; Cagnie et al., 2007). It has been reported that muscle weakness and adapting a poor or incorrect posture may be one of the main factors contributing to neck pain in office workers, especially among typists (Hagberg and Kvarnstrom, 1997; Cagnie et al., 2007). A marked neck flexor muscles weakness has been reported in patients with mechanical neck pain when compared to healthy subjects (Silverman et al., 1991). By using an isometric device, a considerable weakness of both the neck flexor and extensor muscles has been revealed in a group of women with chronic nonspecific neck pain (Ylinen et al., 2004a). Neck muscle weakness has been attributed to pain and muscle discomfort (Ylinen et al., 2004a). It is known that muscle function is disturbed in the presence of pain due to reflex inhibition (DeAndre et al., 1965; Stokes and Young, 1984). Ultrsonography has been reported to be a reliable and feasible method to study the function of neck muscles (Rezasoltani et al., 1999; Kristjansson, 2004). DuPount et al. (2001) compared three diagnostic imaging, magnetic resonance imaging, CT scanning and
* Corresponding author. Tel.: þ98 21 77561723; fax: þ98 21 88407070. E-mail address: [email protected] (A. Rezasoltani). 1 Tel.: þ98 21 77561723; fax: þ98 21 88407070. 1356-689X/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.math.2010.02.010
ultrasonography, to measure muscle thickness. The authors reported similar results for all three methods. They stated that muscle ultrasonography was cheaper, more accessible and a noninvasive method as compared to other imaging methods. Ultrasonography studies have shown that the size of the semispinalis capitis muscle (SECM) is significantly smaller in women compared to men however no significant difference was found when muscle size was normalized for body mass (Rankin et al., 2005). In general, ultrasonography is considered to be an appropriate technique to detect muscle weakness and atrophy (Young et al., 1980; Heckmatt et al., 1988; Hides et al., 2008). Previous studies have shown a significant correlation between the strength of the neck extensor muscles and the cross sectional area of neck semispinalis capitis muscle (Mayoux-Benhamou et al., 1989). Furthermore, a positive correlation has been reported between the cross sectional area and multiplied linear dimensions (MLD) of the neck semispinalis capitis muscle and between MLD and the strength of neck extensor muscles (Rezasoltani et al., 1998, 2002). MLD is calculated as the thickness or anterioreposterior dimension (APD) of the muscle multiplied by the width or lateral dimension (LD) of the muscle and is suggested to be highly reliable and less time consuming than cross sectional area measurements (Rezasoltani, 2003). No studies have compared the strength of neck extensor muscles and the size of the semispinalis capitis muscle in patients with chronic non-specific neck pain. The present study aimed to compare the strength of the neck extensor and flexor muscles and the size (MLD) of the neck semispinalis capitis muscle between
A. Rezasoltani et al. / Manual Therapy 15 (2010) 400e403
female office workers with chronic non-specific neck pain (CNNP) and a group of asymptomatic participants. 2. Methods Twenty female office employees (10 with CNNP and 10 healthy subjects) participated in this study. They were all working in the Taleghani General Hospital, Tehran, Iran. All subjects had comparable age and working hours per day (more than 4 h with computers). All patients complained of neck pain during the last year. The exclusion criteria were as follow: any history of spinal surgery, fracture or cancer of the neck, cervical discopathy, congenital disorders of the cervical spine, traumatic injuries to the neck, positive Valsalva maneuver, radicular pain and nerve root compression. All subjects were informed about the aims and the experimental aspects of the research prior to the study. They completed a questionnaire on their health status and took part in a clinical physical examination. The research was approved by the Ethical Committee of Medical University of Shaheed Beheshti, Tehran, Iran. Anthropometric variables such as height and weight were measured by routine measurement tools and body mass index was computed as weight/hieght2. 2.1. Muscle strength The strength of the neck extensor and flexor muscles was measured while the subject sat on a chair with their head, neck and trunk in a neutral position. The load cell was placed against the occipital bone and forehead to measure the strength of the neck extensor and flexor muscles respectively (Rezasoltani et al., 2003). The thorax and pelvis were fastened tightly at the level of the spine of the scapula and the iliac crest. Subjects were asked to relax their trunk and upper limbs. The apparatus was calibrated each time prior to the study by a fixed standard weight. In order to warm up, subjects performed 2e3 sub-maximal neck muscle contractions. They were then instructed to perform three maximum voluntary contractions (MVCs) of neck extension and flexion, each lasting for 2e3 s. The rest interval was 30 s between each attempt. Consistent verbal commands and encouragements were given to the participant when performing MVC efforts. The maximum value from 3 attempts was selected for further analysis. 2.2. Ultrasonography A real time ultrasonography device (CF sonic Fukuda Denshi UF7500, Japan) with the frequency of 7.5 MHz linear array probe was applied in this study. The subjects were asked to sit on a chair while their sternal notch, chin and the nasal tip were kept in a vertical line. Head and neck were also kept in a neutral position when viewing the subject from the lateral side. The subjects hands were on the table close to the body and the seat surface was horizontal. The participants were asked to relax their neck and shoulder muscles. After applying warm gel, the probe of the ultrasound was moved on both sides of the third cervical vertebra to access the right and left semispinalis capitis muscle. When the echogenic vertebral lamina and the separating fascia were clearly apparent, the image was frozen on the monitor. The LD of the SECM was measured as the longest distance between medial and lateral border of the muscle and the APD was measured on the line perpendicular to the LD in the mid-section of the muscle. Two scans were taken from both sides, and the mean of two LDs and APDs taken on the right and two LDs and APDs taken on the left was used for further analysis. The MLD was calculated as APD LD and considered as size of the SECM (Rezasoltani et al., 1998).
401
In all measurements, muscle size was measured prior to muscle strength. The inter-tester reliability was performed by two examiners in the patient group. For the inter-tester reliability, the SECM size on painful side and the strength of the neck extensor and flexor muscles were measured at two different times within an hour interval. 3. Statistical analysis Routine statistical methods were used to determine the mean, SD (standard deviation) and the range of the measured variables. The Interclass correlation coefficient (ICC), standard error of measurement (SEM) with 95% confidence interval (95%eCI), smallest detectable difference (SDD) and Post hoc analysis (Bonforroni) were computed from one way ANOVA to detect the repeatability of neck muscle strength and muscle size measurements taken by two examiners at separate times. An independent-samples t-test was performed to determine any difference in variables of neck strength, the ratio of the strength of the neck extensor and flexor muscles to body weight (Ext./wt. & Flex./wt.), the dimensions (ADP & LD) and size of SECM, the strength of neck extensor muscles to MLD (Ext./MLD), the MLD to body weight (MLD/wt.) and the strength of neck flexor muscles to the strength of the neck extensor muscles (Flex./Ext.) between patients with chronic non-specific neck pain and healthy subjects. Pearson product-moment was used to detect the association between neck extensor strength and SECM size, between neck strength and body weight and between SECM size and body weight. The confidence level was set at a < 0.05 for statistical significance. All statistical analysis was performed using the SPSS statistical software program (version 10.0 for Windows; SPSS Inc., Chicago, IL, USA). 4. Results The mean, standard deviation and the range of anthropometric characteristics of both groups are presented in Table 1. The ICC, SEM (95%eCI) and SDD indicated a high degree of repeatability of the neck extensor strength measurements (ICC ¼ 0.96, SEM ¼ 3.88 N and SDD ¼ 5.48 N), neck flexor strength measurements (ICC ¼ 0.90, SEM ¼ 4.58 N and SDD ¼ 6.47 N) and neck SECM size measurements between testers (ICC ¼ 0.90, SEM ¼ 0.16 cm2 and SDD ¼ 0.22 cm2). Isometric strength of the neck extensor and flexor muscles were significantly lower in patients than controls (P < 0.001, P < 0.05 respectively). The size and the thickness (APD) of the SECM were lower in patients than controls (P < 0.05, P < 0.01 respectively). There was no significant difference in the lateral dimension of the SECM between the two groups. An ultrasonography image of the neck semispinalis capitis is illustrated in Fig. 1. In Table 2, the mean, standard deviation and range of neck extensor and flexor strength, Flex./Ext., Ext./wt., Flex./wt., MLD of the SECM, MLD/wt. and Ext./MLD are shown for the patients and healthy controls.
Table 1 Characteristics of the control subjects (n ¼ 10) and patients with chronic nonspecific neck pain (n ¼ 10). Mean SD and range are provided. Group
Age (years)
Weight (kg)
Height (cm)
BMI
Controls
32.6 6.4 25.0e43.0 37.2 6.0 26.0e45.0
57.1 5.0a 51.0e65.0 64.2 4.8 58.0e71.0
161.0 5.2 153.0e170.0 159.1 4.9 153.0e170.0
22.0 1.9a 19.0e24.4 25.4 2.0 21.5e28.0
Patients a
Significant level (P < 0.01).
402
A. Rezasoltani et al. / Manual Therapy 15 (2010) 400e403
Fig. 1. The ultrasonography image of neck semispinalis capitis muscle (SECM) in patients with chronic non-specific neck pain.
Between the two groups, the quantities of Ext./wt., Flex./wt. and Flex./Ext. were significantly lower in the patients than controls (P < 0.001, P < 0.05). In addition, the Ext./MLD and MLD/wt. were significantly lower in patients than controls (P < 0.001). There was a significant correlation between neck strength (both extension and flexion) and weight of the body in the control group (r ¼ 0.69. P < 0.05 and r ¼ 0.72, P < 0.01). The correlations were also significant between the neck extensor strength and MLD and between MLD and body weight (r ¼ 0.76, P < 0.01 and r ¼ 0.63, P < 0.05) in the control group. There was no significant correlation between neck strength and subject height and between height and MLD in either group. The correlations between the strength of the neck muscles and body weight, strength of neck extensor muscles and MLD and between MLD and body weight were not significant in the patient group. 5. Discussion In this study, the reliability parameters were in accordance with previous studies (Rezasoltani et al., 1998, 2003). The standard error of measurement (SEM) is recommended in the literature as the most important index of reliability, which quantifies error; a smaller SEM indicates a higher degree of reliability (Bland and Altman, 1996). The SDD of neck muscle strength and neck muscle size measurements in patients with chronic non-specific neck pain showed that only changes larger than 6.47 N and 0.22 cm2 for examiner effects can be regarded as real changes when measuring muscle strength and muscle size repeatedly. The reliability and
feasibility measurements concerning neck muscle strength and neck muscle size measurements have been reported from previous studies in patients and healthy subjects (Kristjansson, 2004; Rezasoltani et al., 2006). Kristjansson, 2004 measured the reliability of ultrasonography to measure the size of neck multifidus muscle in 10 healthy individuals and 10 patients with chronic neck pain. The authors detected a high reliability of ultrasonography measurement in patients with chronic neck pain. The results of our study also indicate that the size of the SECM is significantly smaller in patients compared to healthy subjects. Similar results have been revealed for the lumbar and cervical multifidus muscle in patients with chronic low back pain and chronic neck pain respectively (Kristjansson, 2004; Hides et al., 2008). Our finding was also confirmed when we normalized the SECM size by the subject’s body weight. The size of the muscle was also significantly smaller on the painful side compared to the non painful side indicating a reduction of the SECM size at the level of scanning (third cervical spine) in the group of patients with neck pain. Using ultrasonography, Jull et al. (2007) measured the size of SECM in patients with frequent intermittent headache and showed a significant atrophy of SECM at the level of the second cervical vertebrae ipsilateral to the side of headache in patients with cervicogenic headache. In our study, the APD or the thickness of the SECM also appeared to be significantly smaller in patients than controls. Conversely, the LD or lateral dimension of the SECM was not significantly different between the two groups. In an earlier study, the measurement of APD has been reported to be more sensitive than LD to detect any variation in function of the cervical multifidus (Lee and Tseng, 2006).
Table 2 The mean SD and range of the strength of the neck extensor and flexor muscles, the ratios of neck flexor and extensor strength, the strength of neck flexor muscles to body weight, the strength of neck extensor muscles to body weight, semispinalis capitis muscle size (MLD), the strength of neck extensor muscles to semispinalis capitis muscle size (MLD) and MLD to body weight (n ¼ 20, 10 controls and 10 patients). Group
Flex. (N)
Ext (N)
Flex./Ext. (N)
Flex./wt. (N/kg)
Ext./wt (N/kg)
MLD (Cm2)
MLD/wt (cm2/kg)
Ext./MLD (N/cm2)
Controls
62.2 16.1 35.3e87.3 46.2 7.2 37.3e56-9
127.2 23.2 97.1e157 73.4 9.8 62.8e93.2
0.50 0.15 0.2e0.8 0.63 0.11 0.4e0.8
1.1 0.2 0.7e1.4 0.7 0.1 0.6e0.9
2.2 0.4 1.7e2.9 1.2 0.2 0.98e1.5
1.61 0.19 1.3e2.0 1.36 0.26 0.84e1.7
2.80 0.3 2.5e3.4 2.1 0.4 1.3e2.5
79.5 16.0 65.0e110.6 56.0 14.9 40.6e90.0
Patients
Multiplied Linear Dimensions (MLD), wt. ¼ weight, Ext. ¼ cervical extension strength, Flex. ¼ cervical flexion strength.
A. Rezasoltani et al. / Manual Therapy 15 (2010) 400e403
In this study, the strength of the neck extensor (42%) and flexor muscles (26%) and the ratio of neck flexor to neck extensor strength were lower in patients with neck pain than controls. Isometric strength of the neck extensor and flexor muscles has been shown to be reduced in patients with neck pain and cervicogenic headache (Silverman et al., 1991; Jordan and Mehlsen, 1993; Barton and Hayes, 1996; Ylinen et al., 2004a; Ylinen et al., 2004b). Barton and Hayes (1996) and Ylinen et al. (2004a) reported that the strength of neck muscles in patients with neck pain were 50% and 29% of that of a control group. In addition, the ratio between neck flexor and extensor strength in this study is greater than values previously reported for healthy women (Rezasoltani et al., 2003). The level of this ratio indicates that the neck extensor muscles are relatively more weak compared to the flexor muscles in office workers with chronic non-specific neck pain. During working hours, neck muscle weakness may cause excessive stretch and pain on structures such as ligaments and apophysial joint capsules. Therefore, muscle function may be disturbed as a result of pain and reflex inhibition (DeAndre et al., 1965; Stokes and Young, 1984). Reflex inhibition controls the maximum muscle performance and prevents normal muscle function (Ylinen et al., 2004a). Ylinen et al. (2004b) measured the isometric strength of the neck flexor and extensor muscles in female employees with non-specific neck pain and compared the results to a group of age, sex and occupation matched healthy subjects. The authors revealed that neck muscles strength was lower in patients than healthy subjects and attributed this to pain and reflex inhibition at the time of maximum voluntary contraction. In our study, the strength of the neck extensor and flexor muscles per unit weight of the body were significantly lower in the patient group. Similarly, in a group of violin players and their healthy co-players, the strength of neck extensor and flexor muscles per unit weight of the body was significantly lower for the patients (Rezasoltani et al., 2006). In addition, when we compared neck extensor strength with SECM size between patients and healthy subjects, the ratio was significantly lower in the patient group. This ratio may be useful as a practical measurement for the diagnosis of patients with CNNP or for monitoring the effectiveness of a certain physiotherapy or rehabilitation program in patients with neck pain. In this study, there were significant correlations between neck muscle strength and body weight, neck extensor strength and SECM size and SECM size and body weight in the healthy subjects. The results of these correlations were in accordance with similar correlations which were previously documented in athletes and non athlete subjects (Rezasoltani et al., 1998, 2002, 2005). The insufficient relationship between neck extensor strength and SECM size and between SECM size and body weight may be explained by pain and SECM atrophy in the patient group. It should be noted that in this study we measured the size of the SECM at one level of cervical spine only in a relatively small number of subjects. A complementary study is required to measure the SECM at different levels of the cervical spine in a larger number of patients with chronic non-specific neck pain and healthy subjects. 5.1. Practical application This study indicates that the strength of neck extensor and flexor muscles per unit of body weight, the strength of neck extensor muscles per unit size of the neck semispinalis capitis muscle and the size of neck semispinalis capitis muscle per unit body weight are valuable measurements for the assessment of patients with CNNP. Neck muscle strength and the size of the neck semispinalis capitis muscle may also be useful parameters to monitor the effectiveness of a physiotherapy or rehabilitation intervention.
403
Acknowledgment Great thanks to subjects participated for their participation and Dr Shabestary, MD, for his kind co-operation in this study. References Barton PM, Hayes KC. Neck flexor muscle strength in normal subjects and subjects with unilateral neck pain and headache. Archive of Physical Medicine and Rehabilitation 1996;77(7):680e7. Bland JM, Altman DG. Measurement error. British Medical Journal 1996;313:744. Cagnie B, Danneels L, Van Tiggelen D, De Loose V, Cambier D. Individual and work related risk factors for neck pain among office workers: a cross sectional study. European Spine Journal 2007;16(5):679e86. DeAndre JR, Grant C, Dixon ASJ. Joint distension and reflex muscle inhibition in the knee. Journal of Bone and Joint Surgery 1965;47A:313e22. Dupount AC, Sauerberi EE, Fenton PV, Shargge PC, Loeb GE, Richmond FJR. Real time sonography to estimate muscle thickness: comparison with MRI and CT. Journal of Clinical Ultrasound 2001;29(4):230e6. Fejer R, Kyvik KO, Hartvigsen J. The prevalence of neck pain in the world population: a systematic critical review of the literature. European Spine Journal 2006;15(6):834e48. Hagberg M, Kvarnstrom S. Muscular endurance and EMG fatigue in myofascial shoulder pain. In: Nordin M, Andersson GBJ, Pope MH, editors. Musculoskeletal disorders in work place. Baltimore: Mosby; 1997. p. 331. Heckmatt JZ, Pier N, Dubowitz V. Assessment of quadriceps femoris muscle atrophy and hypertrophy in neuromuscular disease in children. Journal of Clinical Ultrasound 1988;16(3):171e81. Hides J, Gilmore C, Stanton W, Bohlscheid E. Mltifidus size and symmetry among chronic LBP and healthy asymptomatic subjects. Manual Therapy 2008;13 (1):43e9. Jordan A, Mehlsen J. Cervicobrachial syndrome and neck muscle function. Journal of Musculoskeletal Pain 1993;1(3):283e8. Jull G, Amiri M, Bullock-Saxton J, Darnell R, Lander C. Cervical musculoskeletal impairment in frequent intermittent headache. Part 1: subjects with single headaches. Cephalalgia 2007;27:793e802. Kristjansson E. Reliability of ultrasonography for the cervical multifidus muscle in asymptomatic and symptomatic subjects. Manual Therapy 2004;9(2):83e4. Lee JP, Tseng WYI. Measurement of segmental cervical multifidus contraction by ultrasonography in asymptomatic adults. Manual Therapy 2006;12(3):286e94. Leijon M, Hensing G, Alexanderson K. Sickness absence due to musculoskeletal diagnoses: association with occupational gender segregation. Scandinavian Journal of Public Health 2004;32(2):94e101. Mayoux-Benhamou MA, Wybier M, Revel M. Strength and cross sectional area of dorsal neck muscles. Ergonomics 1989;32(10):513e8. Rankin G, Stoke M, Newham D. Size and shape of posterior neck muscles measured by ultrasound imaging. Manual Therapy 2005;10(2):108e15. Rezasoltani A. The applicability of muscle ultrasonography in physiotherapy researches. Journal of Physical Therapy Science 2003;15(1):33e7. Rezasoltani A, Kallinen M, Malkia E, Vihko V. Neck semispinalis capitis muscle size in sitting and prone positions measured by real time ultrasonography. Clinical Rehabilitation 1998;12(1):36e44. Rezasoltani A, Kallinen M, Malkia E, Vihko V. Neck muscle ultrasonography of male weight e lifters, wrestlers and controls. Scandinavian Journal of Medicine and Science in Sport 1999;9(4):214e8. Rezasoltani A, Ylinen J, Vihko V. Isometric cervical extension force and dimensions of the semispinalis capitis. Journal Rehabilitation Research and Development 2002;39(3):423e8. Rezasoltani A, Ahmadi A, Jafarigol A. The reliability of measuring neck muscle strength with a neck muscle force measurement device. Journal of Physical Therapy Science 2003;15(1):7e12. Rezasoltani A, Nehzat-Khoshroh M, Forohide F, Ylinen J. Isometric cervical muscle strength in two groups of elite wrestlers and a group of non-athlete subjects. British Journal of Sports Medicine 2005;39(7):440e3. Rezasoltani A, Hariri S, Sotodehjam B. Neck muscle strength measurement in a group of violin players with and without neck pain. Journal of Rheumatic Diseases 2006;9(Supplement A):158e9. Silverman JL, Rodriques AA, Agre JC. Quantitative cervical flexor strength in healthy subjects and in subjects with mechanical neck pain. Archive of Physical Medicine and Rehabilitation 1991;72(9):679e81. Stokes M, Young A. The contribution of reflex inhibition to arthrogenous muscle weakness. Clinical Sciences 1984;67(1):714. Ylinen J, Salo P, Nykänen M, Kautiainen H, Häkkinen A. Decreased isometric neck strength in women with chronic neck pain and the repeatability of neck strength measurement. Archive of Physical Medicine and Rehabilitation 2004a;85(8):1303e8. Ylinen J, Takala EP, Kautiainen H, Nykänen M, Häkkinen A, Pohjolainen T. Association of neck pain, disability and neck pain during maximal effort with neck muscle strength and range of movement in women with chronic non specific neck pain. European Journal of Pain 2004b;8(5):473e8. Young A, Houghes L, Russell R, Parker MJ, Nichols PJR. Measurment of quadriceps muscle wasting by ultrasonography. Journal of Rheumatology and Rehabilitation 1980;19(3):141e8.
Contents lists available at ScienceDirect
Manual Therapy journal homepage: www.elsevier.com/math
Original article
Preliminary study of neck muscle size and strength measurements in females with chronic non-specific neck pain and healthy control subjects Asghar Rezasoltani*, Ahmadipor Ali-Reza 1, Khademi-Kalantari Khosro 1, Rahimi Abbass 1 University of Shahid Beheshti (MC), Faculty of Rehabilitation, Damavand Ave., across from Bo-Ali Hospital, 16169, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 July 2008 Received in revised form 7 February 2010 Accepted 23 February 2010
Neck muscle weakness and atrophy are two common causes of pain and disability among office workers. The aim of this study was to compare the strength of the neck extensor and flexor muscles and the size of the semispinalis capitis muscle (SECM) in patients with chronic non-specific neck pain (CNNP) and healthy subjects. Twenty female office workers (10 patients with CNNP and 10 healthy subjects) participated in this study. The strength of the neck extensor and flexor muscles was measured by an isometric device and the SECM size was measured by ultrasonography. Neck muscle strength, size of the SECM and the ratios of neck strength to body weight, neck extensor strength to SECM size, SECM size to body weight and neck flexor to extensor strength were all significantly lower in patients compared to controls (P < 0.05). In conclusion, neck strength, the size of the SECM and the ratio of neck muscle strength to SECM size appear to be useful parameters in appraising patients with CNNP. Ó 2010 Elsevier Ltd. All rights reserved.
Keywords: Neck Muscle Size Strength
1. Introduction Neck pain is an increasing problem in society (Fejer et al., 2006). Chronic neck pain is one of the key factors for disability and discomfort in female office workers (Leijon et al., 2004; Cagnie et al., 2007). It has been reported that muscle weakness and adapting a poor or incorrect posture may be one of the main factors contributing to neck pain in office workers, especially among typists (Hagberg and Kvarnstrom, 1997; Cagnie et al., 2007). A marked neck flexor muscles weakness has been reported in patients with mechanical neck pain when compared to healthy subjects (Silverman et al., 1991). By using an isometric device, a considerable weakness of both the neck flexor and extensor muscles has been revealed in a group of women with chronic nonspecific neck pain (Ylinen et al., 2004a). Neck muscle weakness has been attributed to pain and muscle discomfort (Ylinen et al., 2004a). It is known that muscle function is disturbed in the presence of pain due to reflex inhibition (DeAndre et al., 1965; Stokes and Young, 1984). Ultrsonography has been reported to be a reliable and feasible method to study the function of neck muscles (Rezasoltani et al., 1999; Kristjansson, 2004). DuPount et al. (2001) compared three diagnostic imaging, magnetic resonance imaging, CT scanning and
* Corresponding author. Tel.: þ98 21 77561723; fax: þ98 21 88407070. E-mail address: [email protected] (A. Rezasoltani). 1 Tel.: þ98 21 77561723; fax: þ98 21 88407070. 1356-689X/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.math.2010.02.010
ultrasonography, to measure muscle thickness. The authors reported similar results for all three methods. They stated that muscle ultrasonography was cheaper, more accessible and a noninvasive method as compared to other imaging methods. Ultrasonography studies have shown that the size of the semispinalis capitis muscle (SECM) is significantly smaller in women compared to men however no significant difference was found when muscle size was normalized for body mass (Rankin et al., 2005). In general, ultrasonography is considered to be an appropriate technique to detect muscle weakness and atrophy (Young et al., 1980; Heckmatt et al., 1988; Hides et al., 2008). Previous studies have shown a significant correlation between the strength of the neck extensor muscles and the cross sectional area of neck semispinalis capitis muscle (Mayoux-Benhamou et al., 1989). Furthermore, a positive correlation has been reported between the cross sectional area and multiplied linear dimensions (MLD) of the neck semispinalis capitis muscle and between MLD and the strength of neck extensor muscles (Rezasoltani et al., 1998, 2002). MLD is calculated as the thickness or anterioreposterior dimension (APD) of the muscle multiplied by the width or lateral dimension (LD) of the muscle and is suggested to be highly reliable and less time consuming than cross sectional area measurements (Rezasoltani, 2003). No studies have compared the strength of neck extensor muscles and the size of the semispinalis capitis muscle in patients with chronic non-specific neck pain. The present study aimed to compare the strength of the neck extensor and flexor muscles and the size (MLD) of the neck semispinalis capitis muscle between
A. Rezasoltani et al. / Manual Therapy 15 (2010) 400e403
female office workers with chronic non-specific neck pain (CNNP) and a group of asymptomatic participants. 2. Methods Twenty female office employees (10 with CNNP and 10 healthy subjects) participated in this study. They were all working in the Taleghani General Hospital, Tehran, Iran. All subjects had comparable age and working hours per day (more than 4 h with computers). All patients complained of neck pain during the last year. The exclusion criteria were as follow: any history of spinal surgery, fracture or cancer of the neck, cervical discopathy, congenital disorders of the cervical spine, traumatic injuries to the neck, positive Valsalva maneuver, radicular pain and nerve root compression. All subjects were informed about the aims and the experimental aspects of the research prior to the study. They completed a questionnaire on their health status and took part in a clinical physical examination. The research was approved by the Ethical Committee of Medical University of Shaheed Beheshti, Tehran, Iran. Anthropometric variables such as height and weight were measured by routine measurement tools and body mass index was computed as weight/hieght2. 2.1. Muscle strength The strength of the neck extensor and flexor muscles was measured while the subject sat on a chair with their head, neck and trunk in a neutral position. The load cell was placed against the occipital bone and forehead to measure the strength of the neck extensor and flexor muscles respectively (Rezasoltani et al., 2003). The thorax and pelvis were fastened tightly at the level of the spine of the scapula and the iliac crest. Subjects were asked to relax their trunk and upper limbs. The apparatus was calibrated each time prior to the study by a fixed standard weight. In order to warm up, subjects performed 2e3 sub-maximal neck muscle contractions. They were then instructed to perform three maximum voluntary contractions (MVCs) of neck extension and flexion, each lasting for 2e3 s. The rest interval was 30 s between each attempt. Consistent verbal commands and encouragements were given to the participant when performing MVC efforts. The maximum value from 3 attempts was selected for further analysis. 2.2. Ultrasonography A real time ultrasonography device (CF sonic Fukuda Denshi UF7500, Japan) with the frequency of 7.5 MHz linear array probe was applied in this study. The subjects were asked to sit on a chair while their sternal notch, chin and the nasal tip were kept in a vertical line. Head and neck were also kept in a neutral position when viewing the subject from the lateral side. The subjects hands were on the table close to the body and the seat surface was horizontal. The participants were asked to relax their neck and shoulder muscles. After applying warm gel, the probe of the ultrasound was moved on both sides of the third cervical vertebra to access the right and left semispinalis capitis muscle. When the echogenic vertebral lamina and the separating fascia were clearly apparent, the image was frozen on the monitor. The LD of the SECM was measured as the longest distance between medial and lateral border of the muscle and the APD was measured on the line perpendicular to the LD in the mid-section of the muscle. Two scans were taken from both sides, and the mean of two LDs and APDs taken on the right and two LDs and APDs taken on the left was used for further analysis. The MLD was calculated as APD LD and considered as size of the SECM (Rezasoltani et al., 1998).
401
In all measurements, muscle size was measured prior to muscle strength. The inter-tester reliability was performed by two examiners in the patient group. For the inter-tester reliability, the SECM size on painful side and the strength of the neck extensor and flexor muscles were measured at two different times within an hour interval. 3. Statistical analysis Routine statistical methods were used to determine the mean, SD (standard deviation) and the range of the measured variables. The Interclass correlation coefficient (ICC), standard error of measurement (SEM) with 95% confidence interval (95%eCI), smallest detectable difference (SDD) and Post hoc analysis (Bonforroni) were computed from one way ANOVA to detect the repeatability of neck muscle strength and muscle size measurements taken by two examiners at separate times. An independent-samples t-test was performed to determine any difference in variables of neck strength, the ratio of the strength of the neck extensor and flexor muscles to body weight (Ext./wt. & Flex./wt.), the dimensions (ADP & LD) and size of SECM, the strength of neck extensor muscles to MLD (Ext./MLD), the MLD to body weight (MLD/wt.) and the strength of neck flexor muscles to the strength of the neck extensor muscles (Flex./Ext.) between patients with chronic non-specific neck pain and healthy subjects. Pearson product-moment was used to detect the association between neck extensor strength and SECM size, between neck strength and body weight and between SECM size and body weight. The confidence level was set at a < 0.05 for statistical significance. All statistical analysis was performed using the SPSS statistical software program (version 10.0 for Windows; SPSS Inc., Chicago, IL, USA). 4. Results The mean, standard deviation and the range of anthropometric characteristics of both groups are presented in Table 1. The ICC, SEM (95%eCI) and SDD indicated a high degree of repeatability of the neck extensor strength measurements (ICC ¼ 0.96, SEM ¼ 3.88 N and SDD ¼ 5.48 N), neck flexor strength measurements (ICC ¼ 0.90, SEM ¼ 4.58 N and SDD ¼ 6.47 N) and neck SECM size measurements between testers (ICC ¼ 0.90, SEM ¼ 0.16 cm2 and SDD ¼ 0.22 cm2). Isometric strength of the neck extensor and flexor muscles were significantly lower in patients than controls (P < 0.001, P < 0.05 respectively). The size and the thickness (APD) of the SECM were lower in patients than controls (P < 0.05, P < 0.01 respectively). There was no significant difference in the lateral dimension of the SECM between the two groups. An ultrasonography image of the neck semispinalis capitis is illustrated in Fig. 1. In Table 2, the mean, standard deviation and range of neck extensor and flexor strength, Flex./Ext., Ext./wt., Flex./wt., MLD of the SECM, MLD/wt. and Ext./MLD are shown for the patients and healthy controls.
Table 1 Characteristics of the control subjects (n ¼ 10) and patients with chronic nonspecific neck pain (n ¼ 10). Mean SD and range are provided. Group
Age (years)
Weight (kg)
Height (cm)
BMI
Controls
32.6 6.4 25.0e43.0 37.2 6.0 26.0e45.0
57.1 5.0a 51.0e65.0 64.2 4.8 58.0e71.0
161.0 5.2 153.0e170.0 159.1 4.9 153.0e170.0
22.0 1.9a 19.0e24.4 25.4 2.0 21.5e28.0
Patients a
Significant level (P < 0.01).
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Fig. 1. The ultrasonography image of neck semispinalis capitis muscle (SECM) in patients with chronic non-specific neck pain.
Between the two groups, the quantities of Ext./wt., Flex./wt. and Flex./Ext. were significantly lower in the patients than controls (P < 0.001, P < 0.05). In addition, the Ext./MLD and MLD/wt. were significantly lower in patients than controls (P < 0.001). There was a significant correlation between neck strength (both extension and flexion) and weight of the body in the control group (r ¼ 0.69. P < 0.05 and r ¼ 0.72, P < 0.01). The correlations were also significant between the neck extensor strength and MLD and between MLD and body weight (r ¼ 0.76, P < 0.01 and r ¼ 0.63, P < 0.05) in the control group. There was no significant correlation between neck strength and subject height and between height and MLD in either group. The correlations between the strength of the neck muscles and body weight, strength of neck extensor muscles and MLD and between MLD and body weight were not significant in the patient group. 5. Discussion In this study, the reliability parameters were in accordance with previous studies (Rezasoltani et al., 1998, 2003). The standard error of measurement (SEM) is recommended in the literature as the most important index of reliability, which quantifies error; a smaller SEM indicates a higher degree of reliability (Bland and Altman, 1996). The SDD of neck muscle strength and neck muscle size measurements in patients with chronic non-specific neck pain showed that only changes larger than 6.47 N and 0.22 cm2 for examiner effects can be regarded as real changes when measuring muscle strength and muscle size repeatedly. The reliability and
feasibility measurements concerning neck muscle strength and neck muscle size measurements have been reported from previous studies in patients and healthy subjects (Kristjansson, 2004; Rezasoltani et al., 2006). Kristjansson, 2004 measured the reliability of ultrasonography to measure the size of neck multifidus muscle in 10 healthy individuals and 10 patients with chronic neck pain. The authors detected a high reliability of ultrasonography measurement in patients with chronic neck pain. The results of our study also indicate that the size of the SECM is significantly smaller in patients compared to healthy subjects. Similar results have been revealed for the lumbar and cervical multifidus muscle in patients with chronic low back pain and chronic neck pain respectively (Kristjansson, 2004; Hides et al., 2008). Our finding was also confirmed when we normalized the SECM size by the subject’s body weight. The size of the muscle was also significantly smaller on the painful side compared to the non painful side indicating a reduction of the SECM size at the level of scanning (third cervical spine) in the group of patients with neck pain. Using ultrasonography, Jull et al. (2007) measured the size of SECM in patients with frequent intermittent headache and showed a significant atrophy of SECM at the level of the second cervical vertebrae ipsilateral to the side of headache in patients with cervicogenic headache. In our study, the APD or the thickness of the SECM also appeared to be significantly smaller in patients than controls. Conversely, the LD or lateral dimension of the SECM was not significantly different between the two groups. In an earlier study, the measurement of APD has been reported to be more sensitive than LD to detect any variation in function of the cervical multifidus (Lee and Tseng, 2006).
Table 2 The mean SD and range of the strength of the neck extensor and flexor muscles, the ratios of neck flexor and extensor strength, the strength of neck flexor muscles to body weight, the strength of neck extensor muscles to body weight, semispinalis capitis muscle size (MLD), the strength of neck extensor muscles to semispinalis capitis muscle size (MLD) and MLD to body weight (n ¼ 20, 10 controls and 10 patients). Group
Flex. (N)
Ext (N)
Flex./Ext. (N)
Flex./wt. (N/kg)
Ext./wt (N/kg)
MLD (Cm2)
MLD/wt (cm2/kg)
Ext./MLD (N/cm2)
Controls
62.2 16.1 35.3e87.3 46.2 7.2 37.3e56-9
127.2 23.2 97.1e157 73.4 9.8 62.8e93.2
0.50 0.15 0.2e0.8 0.63 0.11 0.4e0.8
1.1 0.2 0.7e1.4 0.7 0.1 0.6e0.9
2.2 0.4 1.7e2.9 1.2 0.2 0.98e1.5
1.61 0.19 1.3e2.0 1.36 0.26 0.84e1.7
2.80 0.3 2.5e3.4 2.1 0.4 1.3e2.5
79.5 16.0 65.0e110.6 56.0 14.9 40.6e90.0
Patients
Multiplied Linear Dimensions (MLD), wt. ¼ weight, Ext. ¼ cervical extension strength, Flex. ¼ cervical flexion strength.
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In this study, the strength of the neck extensor (42%) and flexor muscles (26%) and the ratio of neck flexor to neck extensor strength were lower in patients with neck pain than controls. Isometric strength of the neck extensor and flexor muscles has been shown to be reduced in patients with neck pain and cervicogenic headache (Silverman et al., 1991; Jordan and Mehlsen, 1993; Barton and Hayes, 1996; Ylinen et al., 2004a; Ylinen et al., 2004b). Barton and Hayes (1996) and Ylinen et al. (2004a) reported that the strength of neck muscles in patients with neck pain were 50% and 29% of that of a control group. In addition, the ratio between neck flexor and extensor strength in this study is greater than values previously reported for healthy women (Rezasoltani et al., 2003). The level of this ratio indicates that the neck extensor muscles are relatively more weak compared to the flexor muscles in office workers with chronic non-specific neck pain. During working hours, neck muscle weakness may cause excessive stretch and pain on structures such as ligaments and apophysial joint capsules. Therefore, muscle function may be disturbed as a result of pain and reflex inhibition (DeAndre et al., 1965; Stokes and Young, 1984). Reflex inhibition controls the maximum muscle performance and prevents normal muscle function (Ylinen et al., 2004a). Ylinen et al. (2004b) measured the isometric strength of the neck flexor and extensor muscles in female employees with non-specific neck pain and compared the results to a group of age, sex and occupation matched healthy subjects. The authors revealed that neck muscles strength was lower in patients than healthy subjects and attributed this to pain and reflex inhibition at the time of maximum voluntary contraction. In our study, the strength of the neck extensor and flexor muscles per unit weight of the body were significantly lower in the patient group. Similarly, in a group of violin players and their healthy co-players, the strength of neck extensor and flexor muscles per unit weight of the body was significantly lower for the patients (Rezasoltani et al., 2006). In addition, when we compared neck extensor strength with SECM size between patients and healthy subjects, the ratio was significantly lower in the patient group. This ratio may be useful as a practical measurement for the diagnosis of patients with CNNP or for monitoring the effectiveness of a certain physiotherapy or rehabilitation program in patients with neck pain. In this study, there were significant correlations between neck muscle strength and body weight, neck extensor strength and SECM size and SECM size and body weight in the healthy subjects. The results of these correlations were in accordance with similar correlations which were previously documented in athletes and non athlete subjects (Rezasoltani et al., 1998, 2002, 2005). The insufficient relationship between neck extensor strength and SECM size and between SECM size and body weight may be explained by pain and SECM atrophy in the patient group. It should be noted that in this study we measured the size of the SECM at one level of cervical spine only in a relatively small number of subjects. A complementary study is required to measure the SECM at different levels of the cervical spine in a larger number of patients with chronic non-specific neck pain and healthy subjects. 5.1. Practical application This study indicates that the strength of neck extensor and flexor muscles per unit of body weight, the strength of neck extensor muscles per unit size of the neck semispinalis capitis muscle and the size of neck semispinalis capitis muscle per unit body weight are valuable measurements for the assessment of patients with CNNP. Neck muscle strength and the size of the neck semispinalis capitis muscle may also be useful parameters to monitor the effectiveness of a physiotherapy or rehabilitation intervention.
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