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Chronic neck pain in young adults: perspectives on anatomic differences
Accepted Manuscript Chronic neck pain in young adults: Perspectives on anatomic differences Ji-Hye Lee, Youn-Kwan Park, Joo-Han Kim PII:
S1529-9430(14)00241-1
DOI:
10.1016/j.spinee.2014.02.039
Reference:
SPINEE 55803
To appear in:
The Spine Journal
Received Date: 4 December 2011 Revised Date:
1 December 2013
Accepted Date: 9 February 2014
Please cite this article as: Lee J-H, Park Y-K, Kim J-H, Chronic neck pain in young adults: Perspectives on anatomic differences, The Spine Journal (2014), doi: 10.1016/j.spinee.2014.02.039. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Chronic neck pain in young adults: Perspectives on anatomic differences. Ji-Hye Lee, Youn-Kwan Park and Joo-Han Kim Neurosurgery, Korea University Guro Hospital, Seoul, Republic of Korea
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Corresponding author Youn-Kwan Park, MD Neurosurgery, Korea University Guro Hospital 80, Guro-dong, Guro ku, Seoul, 152-050, Republic of Korea Tel) 82-2-2626-3095
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Fax) 82-2-863-1684
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Email) [email protected]
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Chronic neck pain in young adults: Perspectives on anatomic
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differences Background context: Neck pain (NP) is a common musculoskeletal disorder, but little
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is known about the associated risk factors.
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Purpose: We compared anatomical differences in the neck and trunk area of young
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adult patients with chronic neck pain and control subjects without neck pain to identify
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risk factors and predictors.
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Study Design: Age-, sex-, and BMI-matched retrospective case-control study of a
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consecutive sample.
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Patient sample: Patients with axial NP for longer than 6 months (23 males and 25
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females) and pain-free volunteers (23 males and 25 females).
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Outcome measures: Linear and angular dimensions of the cervicothoracic juction
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Methods: Mid-sagittal magnetic resonance imaging (MRI) scans of the cervicothoracic
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spine were obtained. Four linear and four angular parameters were identified and
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measured. These parameters included depth of the T1-manubrium arch (T1AD), depth of
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the thoracic cage (TXD), tangential height of T1 (T1H1), relative height of T1 (T1H2), T1
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slope (T1S), thoracic inlet inclination (TiI), T1-manubrium arch inclination (T1AI), and
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the angular difference between TiI and T1AI (TiI -T1AI). The measurements were taken
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by two neurosurgeons.
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Results: T1AD and TiI were identified as predictors for NP in the binary logistic
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regression analysis. Each mm increase in T1AD lessened the probability of NP with an
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adjusted odds ratio (OR) of 0.823 (95% CI 0.701–0.966) in females and 0.809 (95% CI
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0.681–0.959) in males. Each degree increase in TiI was associated with the probability
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of NP with an adjusted OR of 1.247 (95% CI 1.060–1.466) in males.
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Conclusions: Measurement of cervicothoracic junctional structures is a reliable and
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feasible method of estimating potential predictor of chronic neck pain in young adults.
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Forward inclination of the thoracic inlet in males and a shallow thoracic cage in females
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were identified as important predictors.
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Keywords: Neck pain, Radiologic study, Gender differences, Thoracic cage dimension, Thoracic inlet inclination
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8 Introduction
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Chronic neck pain is a common musculoskeletal disorder. In adults, the mean point, 1
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year, and lifetime prevalence estimates for neck pain have been reported to be 7.6%,
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37.2%, and 48.5%, respectively [1]. Annually, 11 to 14.1% of workers report limited
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activity as a result of neck pain [2]. Several studies have investigated the risk factors
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associated with the development of chronic neck pain [3-10]. These include female
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gender, older age, high job demands, low social/work support, ex-smoker, a history of
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lower-back disorders, and a history of neck disorders [4]. Furthermore, metabolic
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syndrome, which includes a high body mass index (BMI), is associated with neck pain,
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particularly in males [10]. However, little is known regarding which individuals will
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develop neck pain, particularly with regard to physical factors. Several studies have
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suggested that head posture is closely related to neck pain [3, 5, 6, 9]. However, the
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reliability and validity of this factor is controversial because the measurement is based
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on surface anatomy [11].
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Over the past two decades, the importance of sagittal plane alignment for normal spine function and its role in the development of various disease states have become 2
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increasingly clear [12-18]. In particular, lumbar lordosis has been shown to be involved
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in maintaining an upright posture and can be affected by pelvic morphology and
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orientation. The present study extended this concept to the cervical spine as an
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anatomical structure that may affect the development of neck pain. We focused on the
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morphology of the upper thoracic cage, particularly the thoracic inlet, the arc consisting
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of the manubrium, the first rib, and the first thoracic vertebra (T1) and the surrounding
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area. To our knowledge, no previous study comparing sagittal alignment and the
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dimensions of the thoracic inlet in males and females with and without chronic neck
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pain has been reported. To identify the anatomical predictors for chronic neck pain, we
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compared the cervicothoracic junction in patients with and without chronic neck pain
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using magnetic resonance imaging (MRI).
12 Materials and methods
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A total of 96 young adults aged 20–40 years were enrolled in the present study. Of those,
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48 were patients with chronic neck pain (23 males and 25 females) and 48 were pain-
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free volunteers (23 males and 25 females). The neck-pain group consisted of
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consecutively enrolled patients who had visited our outpatient clinic between January,
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2009 and February, 2011 with persistent mechanical axial neck pain for more than 6
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months and received a cervical spine MRI. All patients had a history of conservative
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care at a primary care unit. Exclusion criteria included a history of neck injury,
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neurological symptoms or signs, radiological abnormalities indicating cervical
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radiculopathy or myelopathy, previous surgery for cervical disorders, and congenital
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anomalies of the cervicothoracic spine. The pain-free subjects were age-, sex-, and
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BMI-matched volunteers recruited from the community by means of announcements
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about the study. The first round of volunteer recruitment occurred in September 2010,
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and 16 subjects were recruited. The second round of volunteer recruitment took place
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after enrolment of the patient group was completed, and the 32 volunteers were age-,
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sex-, and BMI-matched. The inclusion criteria for the pain-free group included no
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previous neck pain (lifetime-to-date), no medical history of a cervical spinal disorder or
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cervical spinal surgery, and no radiological abnormalities detected prior to or during the
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study. Age, sex, weight, and height were recorded, and BMI was calculated as the
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weight in kilograms divided by the square of the height in meters. The degree of neck
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pain experienced by the patients and its effect on everyday life were measured using a
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Visual Analogue Scale (VAS) score for neck pain and the Neck Disability Index (NDI),
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respectively.
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All participants underwent MRI scans of the spine in the supine position performed by technicians blinded to participant status. A standard foam headrest was
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used to ensure that the cervical spine was in the same position for each participant. The
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scans included mid-sagittal T2 images of the whole spine and the cervical spine. All
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measurements were performed using a Picture Archiving and Communication System
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(PACS). Four linear dimensions and four angular parameters were measured on each
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mid-sagittal MRI scan. The parameters are shown in Table 1 and in Figures 1 and 2.
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The MRI scans were presented in random order for assessment by two neurosurgeons
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(Y.P and J.L.). One investigator (Y.P.) measured the MRI scans twice on two separate
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occasions to evaluate intraobserver variation. Interobserver variation was assessed by a
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second observer (J.L.) blinded to both participant status and the assessment of the other
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observer. Variations in the results were analyzed using intraclass correlation coefficients
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(ICCs, SPSS) and the Bland-Altman analysis (Analyse-it ver. 2.26, Analyse-it Software,
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Leeds, UK).
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The Statistical Package for the Social Sciences version 20 (SPSS, Chicago, IL, USA) was used to conduct the statistical tests. Morphology measurements were
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summarized using means ± standard deviations (SD). Unpaired t-tests were used for the
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primary comparisons between the painful and pain-free groups, stratified by sex. Odds
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ratios (ORs) and 95% confidence intervals (CIs) for neck pain predictors were
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calculated using multivariate logistic regression analysis with adjustments made for the
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factors significantly associated with neck pain. Variables that had achieved significance
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levels of p<0.05 in the univariate analyses were entered into the multivariate models.
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Before entering, any less significant variables highly correlated with a better one, such
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as variables from the same dimensions or categories (e.g., T1AD/TXD, T1H1/T1H2, and
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four angular parameters) were dropped to reduce the problem of multicollinearity.
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Results
No significant differences in mean age or BMI between males and females or
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between the neck-pain and pain-free groups were found. The baseline characteristics of
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each group are shown in Table 2. The duration of neck pain was significantly greater in
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females; however, the intensity of neck pain and the NDI score did not differ between
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the sexes.
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The interobserver and intraobserver reliabilities of the MRI measurements were
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calculated for each parameter using an intraclass coefficient (ICC) analysis and 95%
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confidence intervals (CIs). The ICCs for intraobserver reliability were rated as very high
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(0.90~1.00) for all parameters except T1S. However, those for interobserver reliability 5
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decreased. Consequently, two vertical dimensions and T1S were rated as high
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(0.70~0.89) in (Table 3). Bland-Altman plots for the intra- and interobserver agreement
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were generated for all parameters, and the plots for three potential predictors (T1AD,
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TxD1, and TiI) identified in the comparative study are presented in Table 4 and Figures 3
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and 4. The plots for those other parameters were not presented because they did not
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show evidence of systematic relationships between the differences and the means of the
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measurements between examiners. In this analysis, the main bias of interobserver
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reliability was found to originate from one observer consistently reporting higher values
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for three variables, especially for T1AD, compared with the other observers, regardless
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of group. However, 95% of the differences in each parameter were within ±1.96
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standard deviations of the mean of the differences. Therefore, this denotes good
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agreement between the two sets of measurements. Furthermore, the mean differences
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between the NP group and pain-free group for both sexes were greater than the 95% CIs
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of the absolute bias occurring in single measurements.
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Table 5 shows the radiological parameters in the neck-pain and pain-free groups
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according to sex. Two AP dimensions (T1AD and TXD) were significantly smaller in
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both sexes in the neck-pain group compared with those in the pain-free cohort. The
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height of the T1 vertebral body relative to the thoracic cage (T1H1) and the manubrium
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(T1H2) was greater in the neck-pain group than in the pain-free group, but the difference
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was significant only for T1H2. TiI, which indicates a tendency of the T1 vertebra to
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incline forward over the vertical axis, was significantly larger in patients with neck pain
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compared with those in the pain-free group, and the level of significance was higher in
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males than in females. TiI –T1AI was significantly greater in patients with neck pain than
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in pain-free subjects; this difference was statistically significant in both males and
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females. Differences in T1S were significant in both sexes, whereas those in T1AI were
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significant in males only.
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Table 6 shows the unadjusted and adjusted ORs of eight radiological parameters for NP according to gender. When all potential confounders were included
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simultaneously in a multivariable model, the OR of the AP dimension of the rib cage
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(T1AD) remained significant in females, whereas the OR of both AP and angular
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dimensions (T1AD and TiI) remained significant in males. Other variables showing
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significance in the univariate analyses were not associated with NP. Given the study
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design, neither age nor BMI was associated with NP.
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10 Discussion
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The aim of this study was to investigate the role of cervicothoracic junction structures in
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neck pain. Over the past two decades, sagittal spinopelvic alignment has been
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extensively investigated in patients with lumbar spine disorders and pain-free subjects
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of all ages [15, 19-21]. Several anatomical studies have shown that the mobile lumbar
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spine is connected to the fixed pelvic girdle, and the relationship between lumbar and
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pelvic structures plays an important role in the mechanics underlying spinopelvic
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stability [12, 14]. The cervical spine is a mobile region associated with several functions
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important for survival. It allows head movement, which provides a wide field of vision
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and holds the head in a stable position during fast movement. In humans, head and neck
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movement is controlled by neural reflexes that enable the neck to turn, allowing
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tracking moving objects. In contrast, the thoracic cage is a rigid, almost fixed structure,
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as is evident in the relationship between the lumbar spine and the pelvis. Several studies
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have investigated the association between lumbopelvic structure and back pain [12, 15,
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16]; however, none focused on the involvement of the anatomical structures of the neck
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in neck pain. To our knowledge, the present study is the first reported MRI investigation
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of the relationship between neck pain and cervicothoracic structures. We focused
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specifically on the manubrium, the first rib, and T1 vertebra, which form the uppermost
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part of the thoracic cage. This arch provides an anatomical base for the cervical spine to
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which several muscles involved in active movement of the cervical column and the
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cranium, such as the sternocleidomastoid, scalenes, splenius, and semispinalis, are
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attached.
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Our results showed that compared with pain-free subjects, the AP diameter of
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the thoracic cage was significantly smaller in patients with chronic neck pain, and this
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feature was more predominant in females than in males. This finding suggests that
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thoracic cage size may be a predictor for neck pain, and that the AP diameter of the
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uppermost thoracic cage, which serves as a fixed base for head and neck motion, is an
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important factor. The smaller the base, the more likely and frequently the head will
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extend beyond it, particularly when the head moves forward (Fig. 5). This in turn may
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increase neck extensor activity causing neck muscle fatigue [22]. Our finding that
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thoracic cage size is a predictor for neck pain was based on the measurement of bony
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anatomical landmarks and skeletal structure. However, skeletal structure is influenced
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by interactions with the muscles, ligaments, and joints. In general, bony development is
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affected by skeletal muscle; thus, a small bony cage may be related to less muscle mass.
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Although we did not assess muscle cross-sectional area or strength, diminished muscle
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bulk supporting the thoracic and cervical spine would increase the stress on ligamentous
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and joint structures and cause neck pain. An inability to support sustained neck and
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upper trunk posture may cause muscle fatigue and neck pain [23]. Recent studies have
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reported that altered activation of the deep cervical flexor muscles is involved in neck
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pain disorders [22, 24], and specific training of these muscles in females with chronic
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neck pain reduced the pain and improved muscle activation [25]. The sex-related differences in predictors identified here have not been reported
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previously. However, a previous study reported basic anatomical differences in young
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adult males and females [19] that might explain some aspects of the gender differences
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in those parameters. The dorsal position and flat curvature of the upper thoracic spine
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described in females in the previous study might be related to the shallow thoracic cage
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we identified in females, and the ventral position and convex curvature they described
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in males might be consistent with the tendency of males to slope forward. In the pain-
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free group, AP diameter, BMI, and height were significantly greater in males than in
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females; however, the difference in AP diameter (T1Ad, 10% less and TXd, 12% less)
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exceeded that found of the other parameters (height, 9.3% less and BMI, 8.7% less).
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This finding warrants a cross-sectional study of a large cohort to investigate chest
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dimensions and related parameters in females without neck pain. According to national
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statistics on the Korean general population [26, 27], the male/female differences in
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chest circumference (12.2% less in females), height (9.1% less in females), BMI (8.3%
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less in females), and thoracic cage depth might constitute typical characteristics of
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females and a potential source of chronic neck pain.
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Our results showed that the angle of the thoracic inlet (TiI) was significantly
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larger in patients with chronic neck pain than in the pain-free subjects, the statistical
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significance of which was greater in males (Fig. 6B). T1H2, an indicator of the vertical
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position of the weight-bearing center (T1 upper endplate) relative to the manubrium,
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was associated with neck pain, suggesting that the angle of the upper aperture of the 9
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thoracic cage and the relative position of the T1 upper endplate may play a role in neck
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pain. The steeper the slope and the higher T1, the more prone it is to move over the
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weight-bearing center when leaning forward. In turn, this may increase neck extensor
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activity, resulting in neck muscle fatigue. The interrelation between the angle of the
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thoracic inlet and neck pain is not a new concept. It has long been hypothesized that
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musculoskeletal pain related to poor posture is the result of muscle imbalance [28] and
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recognized that abnormalities in head posture are associated with the development of
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chronic neck pain [3, 5, 6, 9]. Upper-Crossed Syndrome (UCS), described by Janda [28,
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29], is the best-known example of posture-related muscle pain. In his hypothesis,
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crossed imbalance of muscles around the shoulder girdle is thought to create joint
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dysfunction and cause pain. Specific postural changes associated with in UCS include
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forward head posture (HPF), increased cervical lordosis and thoracic kyphosis, elevated
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and protracted shoulders, and rotation or abduction and winging of the scapulae [28, 29].
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However, the ability of clinical observation to assess HPF in individuals with and
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without neck pain is unknown because results are conflicting [11]. Although several
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measurement methods have been introduced [6, 9, 30], no gold standard has been
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established. Photographic measurement of the sagittal posture of the thoracic and
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cervical spine is readily performed in daily clinical practice and has been reported to
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give highly reproducible results with high intra- and interobserver reliability [3, 6].
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However, a recent study reported poor reliability and validity of the photographic
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measurement [11] because it did not fully reflect the curvatures of the thoracic and
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cervical spine. Although the slope of the thoracic inlet in males in our study appears to
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be similar to HPF, basic differences exist. The angular parameters detected in our study
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were related to skeletal attributes rather than muscular imbalance because the T1-arch
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and lower structures were almost immobile in our preliminary dynamic plain x-rays and
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dynamic computed tomography (CT) scans (data not shown). In contrast, the
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craniovertebral angle (CVA) used to assess HPF is measured in the structures above C7,
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which are mobile. Moreover, the measurements in the present study were performed in
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the supine position at rest to limit the effect of muscle tension, whereas the CVA is
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measured in the sitting or standing position. The intra- and interobserver reliability of
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the MRI measurements suggested a greater accuracy than that mentioned above using
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head posture. Although we found some consistent, significant differences between the
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measurements made by the observer blind to participant status and the observer who
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was aware of the patient history, the use of observation for assessment is clinically
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useful when the mean differences between individuals with and without neck pain are
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sufficiently large, as shown in Table 4. Some of the disagreement is thought to originate
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from the short training stage after the initial instruction, with a lack of discussion
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between the two observers before the independent measurements. Since this
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measurement task is not a regular clinical activity, the training stage seems crucial for
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better agreement, though it looks very simple. However, even in this first-time
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measurement, 95% of the differences of each parameter were within ±1.96 standard
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deviations of the mean of the differences, indicating good agreement between the two
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sets of measurements.
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The practical significance of non-modifiable structural features is a subject
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requiring further study. Our study population comprised young adults; therefore, our
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findings were more likely to be developmental than acquired, adaptive, or degenerative.
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We do not have any well-oriented ideas or directions at the moment. However, the
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population at risk might benefit from preventive measures, such as postural adaptation 11
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or ergonomic support, to lessen the chance of the development of weak points in daily
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life or to strengthen the muscles holding the structures so as to eliminate fatigue. Muscle
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support and balance might be important factors in relieving neck pain resulting from
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skeletal anomalies. In particular, the scapular stabilizers and lower thoracic and lumbar
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extensor muscles decrease the thoracic inlet angle by increasing lordosis of the lower
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spine, which is why patients with lower-back pain are prone to chronic neck pain.
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Furthermore, the deep flexors of the cervical spine are important for correcting the
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increased cervical lordosis typically found in patients with neck pain. Thus, our findings
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support and extend previous observations regarding posture in patients with chronic
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neck pain and treatment strategies.
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This study has some limitations. First, the study population was relatively small.
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Thus, our findings may not relate to the general population. Moreover, we did not assess
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the job or workplace environment of our cohorts, which would have provided a direct
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measure of the posture stresses/strain on the neck during daily activities. Our study
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population was limited to an urban area in Korea. Thus, caution should be exercised
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when generalizing our findings to other populations. Furthermore, although the males
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and females were BMI-matched, the values were slightly lower than the average of the
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general population. Thus, future studies require a large number of patients with chronic
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neck pain subdivided according to type of work, BMI, and other associated factors. The
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age of the subjects in the present study was 20–40 years. We excluded people older than
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40 years to eliminate the effect of age-related degenerative changes in the cervical spine
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that contribute to neck pain. We further excluded congenital anomalies such as Klippel–
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Feil Syndrome and patients who had undergone cervical surgery. Thus, our results
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should not be generalized to these populations. The inherent nature of the retrospective
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design does not allow us to establish a causative link between the anatomical
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differences and chronic neck pain, and so a prospective cohort study of young adults
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with the anatomical predictors we have identified is warranted.
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4 Conclusions
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Our data suggest that a shallow thoracic cage in females and forward slope of the
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thoracic inlet in males were associated with the development and persistence of chronic
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neck pain. A cross-sectional study including a large number of patients and control
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subjects and a prospective cohort study are needed to determine the predictor of neck pain in the general population.
11 12 References
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During J, Goudfrooij H, Keessen W, Beeker TW, Crowe A. Toward standards for
posture. Postural characteristics of the lower back system in normal and pathologic conditions. Spine (Phila Pa 1976). 1985;10(1):83-7. 19.
Janssen MM, Drevelle X, Humbert L, Skalli W, Castelein RM. Differences in male and
female spino-pelvic alignment in asymptomatic young adults: a three-dimensional analysis using upright low-dose digital biplanar X-rays. Spine (Phila Pa 1976). 2009;34(23):E826-32. 20.
Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the
normal thoracic and lumbar spines and thoracolumbar junction. Spine (Phila Pa 1976). 1989;14(7):717-21. 21.
Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW. An analysis of sagittal spinal
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alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976). 1995;20(12):1351-8. 22.
Johnston V, Jull G, Souvlis T, Jimmieson NL. Neck movement and muscle activity
characteristics in female office workers with neck pain. Spine (Phila Pa 1976). 2008;33(5):55563. Rezasoltani A, Ali-Reza A, Khosro KK, Abbass R. Preliminary study of neck muscle
size and strength measurements in females with chronic non-specific neck pain and healthy control subjects. Man Ther. 2010;15(4):400-3. 24.
Falla DL, Jull GA, Hodges PW. Patients with neck pain demonstrate reduced
electromyographic activity of the deep cervical flexor muscles during performance of the 25.
Falla D, O'Leary S, Farina D, Jull G. The change in deep cervical flexor activity after
Clin J Pain. 2012;28(7):628-34. 26.
Ko BK. 2009 National Physical Status Survey: Korea Sport Promotion Foundation;
2010: p215-9. 27.
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training is associated with the degree of pain reduction in patients with chronic neck pain.
Choi YG, Yoo SH, Park SY. Chronological change of body height and weight type of
shape and body composition in Korean. J Korean Soc Health Statistics. 1997;22(1):35-54. 28.
Janda V. [The significance of muscular faulty posture as pathogenetic factor of
29.
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vertebral disorders]. Arch Phys Ther (Leipz). 1968;20(2):113-6.
Morris CE, Greenman PE, Bullock MI, Basmajian JV, Kobesova A. Vladimir Janda, MD,
DSc: tribute to a master of rehabilitation. Spine (Phila Pa 1976). 2006;31(9):1060-4. 30.
Falla D, Jull G, Russell T, Vicenzino B, Hodges P. Effect of neck exercise on sitting
posture in patients with chronic neck pain. Phys Ther. 2007;87(4):408-17.
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craniocervical flexion test. Spine (Phila Pa 1976). 2004;29(19):2108-14.
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Figure legends
Fig. 1. Description of the linear parameter measurements.
30 31
Fig. 2. Description of the angular parameter measurements.
32 33
Fig. 3. Bland-Altman analysis of the intraobserver agreement for three parameters 15
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(T1AD, TxD1, and TiI) plotted against the average of each parameter superimposed with
2
the mean and 95% limits of agreement.
3 Fig. 4. Bland-Altman analysis for the interobserver agreement for three parameters
5
(T1AD, TxD1, and TiI) plotted against the average of each parameter superimposed with
6
the mean and 95% limits of agreement.
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Fig. 5. Dynamic x-ray images of the lateral cervical spine in two representative cases
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with (A, B) small and (C, D) large AP diameters. When the neck is flexed, the center of
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the head (arrows, external auditory meatus) is positioned far in front of the fixed base
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(solid line) in cases with a small base, but not too far away in those with a large base.
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Fig. 6. Mid-sagittal whole spine T2 images of two representative cases showing A) a
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thin, slender thoracic cage in a female, and B) an inclined thoracic inlet in a male. A
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small AP diameter is associated with cervical hypolordosis (A), whereas an inclined
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thoracic inlet is associated with hyperlordosis (B).
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The English in this document has been checked by at least two professional editors,
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both native speakers of English. For a certificate, please see:
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http://www.textcheck.com/certificate/WUe2zz 16
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Parameter
Abbreviation
Depth of T1-manubrium arch (mm)
T1AD
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Table 1. Nomenclature for magnetic resonance imaging (MRI) parameters, with their abbreviations and descriptions
Description
the T1 spinous process TXD
Mid-sagittal anteroposterior (AP) diameter of thoracic cage, horizontally
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Depth of thoracic cage (mm)
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Mid-sagittal distance between the top of the manubrium and the tip of
intersecting the xiphoid process. Tangential height of T1 (mm)
T1H1
Tangential height of the centroid of the cranial T1 end-plate from the T1A line
Relative height of T1 (mm)
T1H2
Vertical distance from the top of the manubrium to the line of the cranial
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T1 end-plate tangent. T1S
Angle between the superior endplate of T1 and the horizontal.
Thoracic inlet inclination (°)
TiI
Angle between lines drawn from the top of the manubrium to the centroid of
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T1 slope (°)
the cranial T1 end-plate and the horizontal.
T1AI
Difference between two angles (°)
TiI - T1AI
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T1-manubrium arch inclination (°)
*See Figure 1 and 2 for illustrations of the parameters.
Angle between lines drawn along the T1-manubrium arch and the horizontal
Angle between line drawn from the top of the manubrium to the centroid of the cranial T1 end-plate and a line drawn along the T1-manubrium arch
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Parameters
Male
Neck Pain
Group
Group
Group
23
23
25
30(6)
30(7)
0.99
32(5)
BMI (kg/m )
23(2)
23(3)
0.65
21(2)
Symptoms duration (yr)
NA
1.4(0.9)
VASn
NA
4.3(2.1)
NDI
NA
13.6(8.0)
All values are expressed as means (standard deviations).
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NA indicates not applicable.
p
p
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Group
p
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Age(yr)
Neck Pain
Female Pain-free
Number
Pain-free
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Table 2. Clinical baseline characteristics of the neck-pain and pain-free groups.
32(6)
0.99
21(3)
0.56
NA
2.1(1.3)
0.039
NA
5.3(2.1)
0.23
NA
15.0(5.4)
0.67
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reliability
reliabilty
ICC (95%CI)
ICC (95%CI)
T1AD (mm)
0.97 (0.95-0.98)
0.90 (0.82-0.94)
TXD (mm)
0.99 (0.98-0.99)
0.98 (0.96-0.99)
T1H1 (mm)
0.98 (0.96-0.99)
0.88 (0.79-0.93)
T1H2 (mm)
0.96 (0.94-0.98)
0.90 (0.82-0.94)
T1S (°)
0.89 (0.81-0.94)
0.79 (0.65-0.88)
TiI (°)
0.98 (0.96-0.99)
0.94 (0.88-0.97)
T1AI (°)
0.98 (0.97-0.99)
0.94 (0.89-0.97)
TiI-T1AI (°)
0.94 (0.88-0.97)
0.93 (0.87-0.96)
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Inter-observer
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Intra-observer
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Parameters
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measurements calculated by intraclass coefficient (ICC) analysis.
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Inter-observer
Mean differences
mean
mean
between groups
bias (95%CIs)
bias (95%CIs)
Male
T1AD (mm)
0.07 (0.51, 0.65)
3.04 (2.44, 3.64)
5.3
TXD (mm)
0.65 (0.02, 1.30)
-0.83 (-1.82, 0.16)
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T1H1 (mm)
0.22 (0.08, 0.51)
0.54 (0.14, 0.94)
2.6
T1H2 (mm)
1.22 (0.58, 1.86)
-1.70 (-2.37, -1.03)
T1S (°)
-1.15 (-2.02, -0.27)
2.54 (1.54, 3.55)
TiI (°)
0.68 (0.20, 1.15)
-0.98 (-1.42, -0.54)
9.1
5.0
T1AI (°)
0.26 (-0.11, 0.62)
-0.12 (-0.52, 0.28)
4.8
1.2
TiI-T1AI (°)
0.43 (-0.06, 0.92)
-0.86 (-1.35, -0.38)
3.8
2.8
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Intra-observer
Female 5.3
7.2
1.1
6.3
4.6
2.1
3.7
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Table 5. Radiological parameters in the neck-pain and pain-free groups according to sex.
Parameters
free
p
Pain-
Neck Pain
Pain
free
Group
Group
Group
Group
T1AD (mm)
114(6)
108(5)
0.0018
103(5)
97(6)
0.0008
TXD (mm)
176(13)
163(17)
0.0069
155(10)
148(8)
0.008
T1H1 (mm)
26(5)
28(6)
ns
27(5)
28(4)
ns
T1H2 (mm)
30(11)
36(9)
0.032
32(8)
36(7)
0.039
T1S (°)
19(8)
21(5)
ns
19(5)
15(6)
0.021*
TiI (°)
44(8)
53(8)
0.0002
47(9)
52(7)
0.029
T1AI (°)
22(6)
27(5)
0.0058
22(7)
23(7)
ns
TiI-T1AI (°)
24(3)
28(5)
0.0021
27(4)
Values are expressed as means (standard deviations)
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p
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Female
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Radiological
29(4)
0.013
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Table 6. Radiological predictors of chronic neck pain according to sex.
Unadjusted OR
p
Adjusted OR
(95%CI)
p
(95%CI)
1.003 (0.915, 1.099)
0.96
BMI
0.998 (0.943, 1.055)
0.94
T1AD (mm)
0.815 (0.705, 0.941)
0.005*
0.809 (0.681, 0.959)
TXD (mm)
0.940 (0.895, 0.988)
0.013*
na
T1H2 (mm)
1.078 (1.004, 1.157)
0.04*
TiI (°)
1.169 (1.059, 1.290)
0.002*
1.247 (1.060, 1.466)
TiI-T1AI (°)
1.303 (1.091, 1.555)
0.003*
na
0.015*
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ns
0.008*
Female Unadjusted OR
p
Adjusted OR
(95%CI)
p
(95%CI)
1.009 (0.908, 1.121)
0.86
BMI
0.878 (0.669, 1.153)
0.35
T1AD (mm)
0.814 (0.713, 0.930)
0.002*
0.823 (0.701, 0.966)
TXD (mm)
0.899 (0.829, 0.975)
0.01*
na
T1H2 (mm)
1.087 (1.002, 1.179)
0.045*
TiI (°)
1.085 (1.006, 1.170)
0.034*
TiI-T1AI (°)
1.204 (1.031, 1.406)
0.019*
0.017*
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Parameters
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na
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ns
*Adjustments made for the parameters significantly associated with neck pain in the univariate analysis.
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OD; odd ratio, ns; not significant, *; significant, na; not applicable
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100
105 110 Mean of T1AD
115
120
4 2 0 -2 -4 -6 -8
125
140
160 180 Mean of TxD
200
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120
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5 4 3 2 1 0 -1 -2 -3 -4 -5
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Difference between measures
95
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90
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5 4 3 2 1 0 -1 -2 -3 -4 -5
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Difference between measures
Difference between measures
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30
40
50 Mean of TiI
60
70
6 5
3 2 1 0 -1 85
95
105 Mean of T1AD
160 Mean of TxD
5 3 2 1 -1 -2 -3
180
200
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4
0
125
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Difference between measures
120
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Difference between measures
12 10 8 6 4 2 0 -2 -4 -6
115
30
40
50 Mean of TiI
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S1529-9430(14)00241-1
DOI:
10.1016/j.spinee.2014.02.039
Reference:
SPINEE 55803
To appear in:
The Spine Journal
Received Date: 4 December 2011 Revised Date:
1 December 2013
Accepted Date: 9 February 2014
Please cite this article as: Lee J-H, Park Y-K, Kim J-H, Chronic neck pain in young adults: Perspectives on anatomic differences, The Spine Journal (2014), doi: 10.1016/j.spinee.2014.02.039. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Chronic neck pain in young adults: Perspectives on anatomic differences. Ji-Hye Lee, Youn-Kwan Park and Joo-Han Kim Neurosurgery, Korea University Guro Hospital, Seoul, Republic of Korea
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Corresponding author Youn-Kwan Park, MD Neurosurgery, Korea University Guro Hospital 80, Guro-dong, Guro ku, Seoul, 152-050, Republic of Korea Tel) 82-2-2626-3095
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Fax) 82-2-863-1684
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Email) [email protected]
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Chronic neck pain in young adults: Perspectives on anatomic
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differences Background context: Neck pain (NP) is a common musculoskeletal disorder, but little
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is known about the associated risk factors.
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Purpose: We compared anatomical differences in the neck and trunk area of young
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adult patients with chronic neck pain and control subjects without neck pain to identify
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risk factors and predictors.
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Study Design: Age-, sex-, and BMI-matched retrospective case-control study of a
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consecutive sample.
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Patient sample: Patients with axial NP for longer than 6 months (23 males and 25
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females) and pain-free volunteers (23 males and 25 females).
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Outcome measures: Linear and angular dimensions of the cervicothoracic juction
13
Methods: Mid-sagittal magnetic resonance imaging (MRI) scans of the cervicothoracic
14
spine were obtained. Four linear and four angular parameters were identified and
15
measured. These parameters included depth of the T1-manubrium arch (T1AD), depth of
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the thoracic cage (TXD), tangential height of T1 (T1H1), relative height of T1 (T1H2), T1
17
slope (T1S), thoracic inlet inclination (TiI), T1-manubrium arch inclination (T1AI), and
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the angular difference between TiI and T1AI (TiI -T1AI). The measurements were taken
19
by two neurosurgeons.
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Results: T1AD and TiI were identified as predictors for NP in the binary logistic
21
regression analysis. Each mm increase in T1AD lessened the probability of NP with an
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adjusted odds ratio (OR) of 0.823 (95% CI 0.701–0.966) in females and 0.809 (95% CI
23
0.681–0.959) in males. Each degree increase in TiI was associated with the probability
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of NP with an adjusted OR of 1.247 (95% CI 1.060–1.466) in males.
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Conclusions: Measurement of cervicothoracic junctional structures is a reliable and
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feasible method of estimating potential predictor of chronic neck pain in young adults.
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Forward inclination of the thoracic inlet in males and a shallow thoracic cage in females
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were identified as important predictors.
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Keywords: Neck pain, Radiologic study, Gender differences, Thoracic cage dimension, Thoracic inlet inclination
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8 Introduction
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Chronic neck pain is a common musculoskeletal disorder. In adults, the mean point, 1
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year, and lifetime prevalence estimates for neck pain have been reported to be 7.6%,
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37.2%, and 48.5%, respectively [1]. Annually, 11 to 14.1% of workers report limited
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activity as a result of neck pain [2]. Several studies have investigated the risk factors
14
associated with the development of chronic neck pain [3-10]. These include female
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gender, older age, high job demands, low social/work support, ex-smoker, a history of
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lower-back disorders, and a history of neck disorders [4]. Furthermore, metabolic
17
syndrome, which includes a high body mass index (BMI), is associated with neck pain,
18
particularly in males [10]. However, little is known regarding which individuals will
19
develop neck pain, particularly with regard to physical factors. Several studies have
20
suggested that head posture is closely related to neck pain [3, 5, 6, 9]. However, the
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reliability and validity of this factor is controversial because the measurement is based
22
on surface anatomy [11].
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Over the past two decades, the importance of sagittal plane alignment for normal spine function and its role in the development of various disease states have become 2
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increasingly clear [12-18]. In particular, lumbar lordosis has been shown to be involved
2
in maintaining an upright posture and can be affected by pelvic morphology and
3
orientation. The present study extended this concept to the cervical spine as an
4
anatomical structure that may affect the development of neck pain. We focused on the
5
morphology of the upper thoracic cage, particularly the thoracic inlet, the arc consisting
6
of the manubrium, the first rib, and the first thoracic vertebra (T1) and the surrounding
7
area. To our knowledge, no previous study comparing sagittal alignment and the
8
dimensions of the thoracic inlet in males and females with and without chronic neck
9
pain has been reported. To identify the anatomical predictors for chronic neck pain, we
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1
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compared the cervicothoracic junction in patients with and without chronic neck pain
11
using magnetic resonance imaging (MRI).
12 Materials and methods
14
A total of 96 young adults aged 20–40 years were enrolled in the present study. Of those,
15
48 were patients with chronic neck pain (23 males and 25 females) and 48 were pain-
16
free volunteers (23 males and 25 females). The neck-pain group consisted of
17
consecutively enrolled patients who had visited our outpatient clinic between January,
18
2009 and February, 2011 with persistent mechanical axial neck pain for more than 6
19
months and received a cervical spine MRI. All patients had a history of conservative
20
care at a primary care unit. Exclusion criteria included a history of neck injury,
21
neurological symptoms or signs, radiological abnormalities indicating cervical
22
radiculopathy or myelopathy, previous surgery for cervical disorders, and congenital
23
anomalies of the cervicothoracic spine. The pain-free subjects were age-, sex-, and
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BMI-matched volunteers recruited from the community by means of announcements
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about the study. The first round of volunteer recruitment occurred in September 2010,
2
and 16 subjects were recruited. The second round of volunteer recruitment took place
3
after enrolment of the patient group was completed, and the 32 volunteers were age-,
4
sex-, and BMI-matched. The inclusion criteria for the pain-free group included no
5
previous neck pain (lifetime-to-date), no medical history of a cervical spinal disorder or
6
cervical spinal surgery, and no radiological abnormalities detected prior to or during the
7
study. Age, sex, weight, and height were recorded, and BMI was calculated as the
8
weight in kilograms divided by the square of the height in meters. The degree of neck
9
pain experienced by the patients and its effect on everyday life were measured using a
10
Visual Analogue Scale (VAS) score for neck pain and the Neck Disability Index (NDI),
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respectively.
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All participants underwent MRI scans of the spine in the supine position performed by technicians blinded to participant status. A standard foam headrest was
14
used to ensure that the cervical spine was in the same position for each participant. The
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scans included mid-sagittal T2 images of the whole spine and the cervical spine. All
16
measurements were performed using a Picture Archiving and Communication System
17
(PACS). Four linear dimensions and four angular parameters were measured on each
18
mid-sagittal MRI scan. The parameters are shown in Table 1 and in Figures 1 and 2.
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The MRI scans were presented in random order for assessment by two neurosurgeons
20
(Y.P and J.L.). One investigator (Y.P.) measured the MRI scans twice on two separate
21
occasions to evaluate intraobserver variation. Interobserver variation was assessed by a
22
second observer (J.L.) blinded to both participant status and the assessment of the other
23
observer. Variations in the results were analyzed using intraclass correlation coefficients
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(ICCs, SPSS) and the Bland-Altman analysis (Analyse-it ver. 2.26, Analyse-it Software,
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Leeds, UK).
3
The Statistical Package for the Social Sciences version 20 (SPSS, Chicago, IL, USA) was used to conduct the statistical tests. Morphology measurements were
5
summarized using means ± standard deviations (SD). Unpaired t-tests were used for the
6
primary comparisons between the painful and pain-free groups, stratified by sex. Odds
7
ratios (ORs) and 95% confidence intervals (CIs) for neck pain predictors were
8
calculated using multivariate logistic regression analysis with adjustments made for the
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factors significantly associated with neck pain. Variables that had achieved significance
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levels of p<0.05 in the univariate analyses were entered into the multivariate models.
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Before entering, any less significant variables highly correlated with a better one, such
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as variables from the same dimensions or categories (e.g., T1AD/TXD, T1H1/T1H2, and
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four angular parameters) were dropped to reduce the problem of multicollinearity.
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Results
No significant differences in mean age or BMI between males and females or
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between the neck-pain and pain-free groups were found. The baseline characteristics of
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each group are shown in Table 2. The duration of neck pain was significantly greater in
19
females; however, the intensity of neck pain and the NDI score did not differ between
20
the sexes.
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The interobserver and intraobserver reliabilities of the MRI measurements were
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calculated for each parameter using an intraclass coefficient (ICC) analysis and 95%
23
confidence intervals (CIs). The ICCs for intraobserver reliability were rated as very high
24
(0.90~1.00) for all parameters except T1S. However, those for interobserver reliability 5
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decreased. Consequently, two vertical dimensions and T1S were rated as high
2
(0.70~0.89) in (Table 3). Bland-Altman plots for the intra- and interobserver agreement
3
were generated for all parameters, and the plots for three potential predictors (T1AD,
4
TxD1, and TiI) identified in the comparative study are presented in Table 4 and Figures 3
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and 4. The plots for those other parameters were not presented because they did not
6
show evidence of systematic relationships between the differences and the means of the
7
measurements between examiners. In this analysis, the main bias of interobserver
8
reliability was found to originate from one observer consistently reporting higher values
9
for three variables, especially for T1AD, compared with the other observers, regardless
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of group. However, 95% of the differences in each parameter were within ±1.96
11
standard deviations of the mean of the differences. Therefore, this denotes good
12
agreement between the two sets of measurements. Furthermore, the mean differences
13
between the NP group and pain-free group for both sexes were greater than the 95% CIs
14
of the absolute bias occurring in single measurements.
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Table 5 shows the radiological parameters in the neck-pain and pain-free groups
16
according to sex. Two AP dimensions (T1AD and TXD) were significantly smaller in
17
both sexes in the neck-pain group compared with those in the pain-free cohort. The
18
height of the T1 vertebral body relative to the thoracic cage (T1H1) and the manubrium
19
(T1H2) was greater in the neck-pain group than in the pain-free group, but the difference
20
was significant only for T1H2. TiI, which indicates a tendency of the T1 vertebra to
21
incline forward over the vertical axis, was significantly larger in patients with neck pain
22
compared with those in the pain-free group, and the level of significance was higher in
23
males than in females. TiI –T1AI was significantly greater in patients with neck pain than
24
in pain-free subjects; this difference was statistically significant in both males and
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females. Differences in T1S were significant in both sexes, whereas those in T1AI were
2
significant in males only.
3
Table 6 shows the unadjusted and adjusted ORs of eight radiological parameters for NP according to gender. When all potential confounders were included
5
simultaneously in a multivariable model, the OR of the AP dimension of the rib cage
6
(T1AD) remained significant in females, whereas the OR of both AP and angular
7
dimensions (T1AD and TiI) remained significant in males. Other variables showing
8
significance in the univariate analyses were not associated with NP. Given the study
9
design, neither age nor BMI was associated with NP.
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10 Discussion
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The aim of this study was to investigate the role of cervicothoracic junction structures in
13
neck pain. Over the past two decades, sagittal spinopelvic alignment has been
14
extensively investigated in patients with lumbar spine disorders and pain-free subjects
15
of all ages [15, 19-21]. Several anatomical studies have shown that the mobile lumbar
16
spine is connected to the fixed pelvic girdle, and the relationship between lumbar and
17
pelvic structures plays an important role in the mechanics underlying spinopelvic
18
stability [12, 14]. The cervical spine is a mobile region associated with several functions
19
important for survival. It allows head movement, which provides a wide field of vision
20
and holds the head in a stable position during fast movement. In humans, head and neck
21
movement is controlled by neural reflexes that enable the neck to turn, allowing
22
tracking moving objects. In contrast, the thoracic cage is a rigid, almost fixed structure,
23
as is evident in the relationship between the lumbar spine and the pelvis. Several studies
24
have investigated the association between lumbopelvic structure and back pain [12, 15,
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16]; however, none focused on the involvement of the anatomical structures of the neck
2
in neck pain. To our knowledge, the present study is the first reported MRI investigation
3
of the relationship between neck pain and cervicothoracic structures. We focused
4
specifically on the manubrium, the first rib, and T1 vertebra, which form the uppermost
5
part of the thoracic cage. This arch provides an anatomical base for the cervical spine to
6
which several muscles involved in active movement of the cervical column and the
7
cranium, such as the sternocleidomastoid, scalenes, splenius, and semispinalis, are
8
attached.
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Our results showed that compared with pain-free subjects, the AP diameter of
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the thoracic cage was significantly smaller in patients with chronic neck pain, and this
11
feature was more predominant in females than in males. This finding suggests that
12
thoracic cage size may be a predictor for neck pain, and that the AP diameter of the
13
uppermost thoracic cage, which serves as a fixed base for head and neck motion, is an
14
important factor. The smaller the base, the more likely and frequently the head will
15
extend beyond it, particularly when the head moves forward (Fig. 5). This in turn may
16
increase neck extensor activity causing neck muscle fatigue [22]. Our finding that
17
thoracic cage size is a predictor for neck pain was based on the measurement of bony
18
anatomical landmarks and skeletal structure. However, skeletal structure is influenced
19
by interactions with the muscles, ligaments, and joints. In general, bony development is
20
affected by skeletal muscle; thus, a small bony cage may be related to less muscle mass.
21
Although we did not assess muscle cross-sectional area or strength, diminished muscle
22
bulk supporting the thoracic and cervical spine would increase the stress on ligamentous
23
and joint structures and cause neck pain. An inability to support sustained neck and
24
upper trunk posture may cause muscle fatigue and neck pain [23]. Recent studies have
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1
reported that altered activation of the deep cervical flexor muscles is involved in neck
2
pain disorders [22, 24], and specific training of these muscles in females with chronic
3
neck pain reduced the pain and improved muscle activation [25]. The sex-related differences in predictors identified here have not been reported
5
previously. However, a previous study reported basic anatomical differences in young
6
adult males and females [19] that might explain some aspects of the gender differences
7
in those parameters. The dorsal position and flat curvature of the upper thoracic spine
8
described in females in the previous study might be related to the shallow thoracic cage
9
we identified in females, and the ventral position and convex curvature they described
10
in males might be consistent with the tendency of males to slope forward. In the pain-
11
free group, AP diameter, BMI, and height were significantly greater in males than in
12
females; however, the difference in AP diameter (T1Ad, 10% less and TXd, 12% less)
13
exceeded that found of the other parameters (height, 9.3% less and BMI, 8.7% less).
14
This finding warrants a cross-sectional study of a large cohort to investigate chest
15
dimensions and related parameters in females without neck pain. According to national
16
statistics on the Korean general population [26, 27], the male/female differences in
17
chest circumference (12.2% less in females), height (9.1% less in females), BMI (8.3%
18
less in females), and thoracic cage depth might constitute typical characteristics of
19
females and a potential source of chronic neck pain.
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Our results showed that the angle of the thoracic inlet (TiI) was significantly
21
larger in patients with chronic neck pain than in the pain-free subjects, the statistical
22
significance of which was greater in males (Fig. 6B). T1H2, an indicator of the vertical
23
position of the weight-bearing center (T1 upper endplate) relative to the manubrium,
24
was associated with neck pain, suggesting that the angle of the upper aperture of the 9
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thoracic cage and the relative position of the T1 upper endplate may play a role in neck
2
pain. The steeper the slope and the higher T1, the more prone it is to move over the
3
weight-bearing center when leaning forward. In turn, this may increase neck extensor
4
activity, resulting in neck muscle fatigue. The interrelation between the angle of the
5
thoracic inlet and neck pain is not a new concept. It has long been hypothesized that
6
musculoskeletal pain related to poor posture is the result of muscle imbalance [28] and
7
recognized that abnormalities in head posture are associated with the development of
8
chronic neck pain [3, 5, 6, 9]. Upper-Crossed Syndrome (UCS), described by Janda [28,
9
29], is the best-known example of posture-related muscle pain. In his hypothesis,
10
crossed imbalance of muscles around the shoulder girdle is thought to create joint
11
dysfunction and cause pain. Specific postural changes associated with in UCS include
12
forward head posture (HPF), increased cervical lordosis and thoracic kyphosis, elevated
13
and protracted shoulders, and rotation or abduction and winging of the scapulae [28, 29].
14
However, the ability of clinical observation to assess HPF in individuals with and
15
without neck pain is unknown because results are conflicting [11]. Although several
16
measurement methods have been introduced [6, 9, 30], no gold standard has been
17
established. Photographic measurement of the sagittal posture of the thoracic and
18
cervical spine is readily performed in daily clinical practice and has been reported to
19
give highly reproducible results with high intra- and interobserver reliability [3, 6].
20
However, a recent study reported poor reliability and validity of the photographic
21
measurement [11] because it did not fully reflect the curvatures of the thoracic and
22
cervical spine. Although the slope of the thoracic inlet in males in our study appears to
23
be similar to HPF, basic differences exist. The angular parameters detected in our study
24
were related to skeletal attributes rather than muscular imbalance because the T1-arch
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and lower structures were almost immobile in our preliminary dynamic plain x-rays and
2
dynamic computed tomography (CT) scans (data not shown). In contrast, the
3
craniovertebral angle (CVA) used to assess HPF is measured in the structures above C7,
4
which are mobile. Moreover, the measurements in the present study were performed in
5
the supine position at rest to limit the effect of muscle tension, whereas the CVA is
6
measured in the sitting or standing position. The intra- and interobserver reliability of
7
the MRI measurements suggested a greater accuracy than that mentioned above using
8
head posture. Although we found some consistent, significant differences between the
9
measurements made by the observer blind to participant status and the observer who
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was aware of the patient history, the use of observation for assessment is clinically
11
useful when the mean differences between individuals with and without neck pain are
12
sufficiently large, as shown in Table 4. Some of the disagreement is thought to originate
13
from the short training stage after the initial instruction, with a lack of discussion
14
between the two observers before the independent measurements. Since this
15
measurement task is not a regular clinical activity, the training stage seems crucial for
16
better agreement, though it looks very simple. However, even in this first-time
17
measurement, 95% of the differences of each parameter were within ±1.96 standard
18
deviations of the mean of the differences, indicating good agreement between the two
19
sets of measurements.
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The practical significance of non-modifiable structural features is a subject
21
requiring further study. Our study population comprised young adults; therefore, our
22
findings were more likely to be developmental than acquired, adaptive, or degenerative.
23
We do not have any well-oriented ideas or directions at the moment. However, the
24
population at risk might benefit from preventive measures, such as postural adaptation 11
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or ergonomic support, to lessen the chance of the development of weak points in daily
2
life or to strengthen the muscles holding the structures so as to eliminate fatigue. Muscle
3
support and balance might be important factors in relieving neck pain resulting from
4
skeletal anomalies. In particular, the scapular stabilizers and lower thoracic and lumbar
5
extensor muscles decrease the thoracic inlet angle by increasing lordosis of the lower
6
spine, which is why patients with lower-back pain are prone to chronic neck pain.
7
Furthermore, the deep flexors of the cervical spine are important for correcting the
8
increased cervical lordosis typically found in patients with neck pain. Thus, our findings
9
support and extend previous observations regarding posture in patients with chronic
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neck pain and treatment strategies.
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This study has some limitations. First, the study population was relatively small.
12
Thus, our findings may not relate to the general population. Moreover, we did not assess
13
the job or workplace environment of our cohorts, which would have provided a direct
14
measure of the posture stresses/strain on the neck during daily activities. Our study
15
population was limited to an urban area in Korea. Thus, caution should be exercised
16
when generalizing our findings to other populations. Furthermore, although the males
17
and females were BMI-matched, the values were slightly lower than the average of the
18
general population. Thus, future studies require a large number of patients with chronic
19
neck pain subdivided according to type of work, BMI, and other associated factors. The
20
age of the subjects in the present study was 20–40 years. We excluded people older than
21
40 years to eliminate the effect of age-related degenerative changes in the cervical spine
22
that contribute to neck pain. We further excluded congenital anomalies such as Klippel–
23
Feil Syndrome and patients who had undergone cervical surgery. Thus, our results
24
should not be generalized to these populations. The inherent nature of the retrospective
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design does not allow us to establish a causative link between the anatomical
2
differences and chronic neck pain, and so a prospective cohort study of young adults
3
with the anatomical predictors we have identified is warranted.
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4 Conclusions
6
Our data suggest that a shallow thoracic cage in females and forward slope of the
7
thoracic inlet in males were associated with the development and persistence of chronic
8
neck pain. A cross-sectional study including a large number of patients and control
9
subjects and a prospective cohort study are needed to determine the predictor of neck pain in the general population.
11 12 References
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pain of chronic nontraumatic origin: a comparison between patients and pain-free persons. Arch Phys Med Rehabil. 2009;90(4):669-74. 6.
Yip CHT, Chiu TTW, Poon ATK. The relationship between head posture and severity
and disability of patients with neck pain. Manual Ther. 2008;13(2):148-54. 7.
Hanten WP, Lucio RM, Russell JL, Brunt D. Assessment of Total Head Excursion and
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Silva AG, Punt TD, Johnson MI. Reliability and validity of head posture assessment
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Korovessis P, Stamatakis M, Baikousis A. Segmental roentgenographic analysis of
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vertebral inclination on sagittal plane in asymptomatic versus chronic low back pain patients. Jackson RP, Hales C. Congruent spinopelvic alignment on standing lateral
radiographs of adult volunteers. Spine (Phila Pa 1976). 2000;25(21):2808-15. 14.
Jackson RP, Kanemura T, Kawakami N, Hales C. Lumbopelvic lordosis and pelvic
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balance in standing volunteers and patients with low back pain matched for age, sex, and size. A prospective controlled clinical study. Spine (Phila Pa 1976). 1994;19(14):1611-8. 16.
Farcy JP, Schwab FJ. Management of flatback and related kyphotic decompensation
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posture. Postural characteristics of the lower back system in normal and pathologic conditions. Spine (Phila Pa 1976). 1985;10(1):83-7. 19.
Janssen MM, Drevelle X, Humbert L, Skalli W, Castelein RM. Differences in male and
female spino-pelvic alignment in asymptomatic young adults: a three-dimensional analysis using upright low-dose digital biplanar X-rays. Spine (Phila Pa 1976). 2009;34(23):E826-32. 20.
Bernhardt M, Bridwell KH. Segmental analysis of the sagittal plane alignment of the
normal thoracic and lumbar spines and thoracolumbar junction. Spine (Phila Pa 1976). 1989;14(7):717-21. 21.
Gelb DE, Lenke LG, Bridwell KH, Blanke K, McEnery KW. An analysis of sagittal spinal
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alignment in 100 asymptomatic middle and older aged volunteers. Spine (Phila Pa 1976). 1995;20(12):1351-8. 22.
Johnston V, Jull G, Souvlis T, Jimmieson NL. Neck movement and muscle activity
characteristics in female office workers with neck pain. Spine (Phila Pa 1976). 2008;33(5):55563. Rezasoltani A, Ali-Reza A, Khosro KK, Abbass R. Preliminary study of neck muscle
size and strength measurements in females with chronic non-specific neck pain and healthy control subjects. Man Ther. 2010;15(4):400-3. 24.
Falla DL, Jull GA, Hodges PW. Patients with neck pain demonstrate reduced
electromyographic activity of the deep cervical flexor muscles during performance of the 25.
Falla D, O'Leary S, Farina D, Jull G. The change in deep cervical flexor activity after
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Ko BK. 2009 National Physical Status Survey: Korea Sport Promotion Foundation;
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training is associated with the degree of pain reduction in patients with chronic neck pain.
Choi YG, Yoo SH, Park SY. Chronological change of body height and weight type of
shape and body composition in Korean. J Korean Soc Health Statistics. 1997;22(1):35-54. 28.
Janda V. [The significance of muscular faulty posture as pathogenetic factor of
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vertebral disorders]. Arch Phys Ther (Leipz). 1968;20(2):113-6.
Morris CE, Greenman PE, Bullock MI, Basmajian JV, Kobesova A. Vladimir Janda, MD,
DSc: tribute to a master of rehabilitation. Spine (Phila Pa 1976). 2006;31(9):1060-4. 30.
Falla D, Jull G, Russell T, Vicenzino B, Hodges P. Effect of neck exercise on sitting
posture in patients with chronic neck pain. Phys Ther. 2007;87(4):408-17.
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craniocervical flexion test. Spine (Phila Pa 1976). 2004;29(19):2108-14.
26 27
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Figure legends
Fig. 1. Description of the linear parameter measurements.
30 31
Fig. 2. Description of the angular parameter measurements.
32 33
Fig. 3. Bland-Altman analysis of the intraobserver agreement for three parameters 15
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1
(T1AD, TxD1, and TiI) plotted against the average of each parameter superimposed with
2
the mean and 95% limits of agreement.
3 Fig. 4. Bland-Altman analysis for the interobserver agreement for three parameters
5
(T1AD, TxD1, and TiI) plotted against the average of each parameter superimposed with
6
the mean and 95% limits of agreement.
8
Fig. 5. Dynamic x-ray images of the lateral cervical spine in two representative cases
9
with (A, B) small and (C, D) large AP diameters. When the neck is flexed, the center of
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the head (arrows, external auditory meatus) is positioned far in front of the fixed base
11
(solid line) in cases with a small base, but not too far away in those with a large base.
12
Fig. 6. Mid-sagittal whole spine T2 images of two representative cases showing A) a
14
thin, slender thoracic cage in a female, and B) an inclined thoracic inlet in a male. A
15
small AP diameter is associated with cervical hypolordosis (A), whereas an inclined
16
thoracic inlet is associated with hyperlordosis (B).
18 19 20
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The English in this document has been checked by at least two professional editors,
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both native speakers of English. For a certificate, please see:
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http://www.textcheck.com/certificate/WUe2zz 16
ACCEPTED MANUSCRIPT Acknowledgments Authors thank SY Whang, PhD, for the statistical support. This study was supported by a
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Korea University Grant.
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Parameter
Abbreviation
Depth of T1-manubrium arch (mm)
T1AD
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Table 1. Nomenclature for magnetic resonance imaging (MRI) parameters, with their abbreviations and descriptions
Description
the T1 spinous process TXD
Mid-sagittal anteroposterior (AP) diameter of thoracic cage, horizontally
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Depth of thoracic cage (mm)
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Mid-sagittal distance between the top of the manubrium and the tip of
intersecting the xiphoid process. Tangential height of T1 (mm)
T1H1
Tangential height of the centroid of the cranial T1 end-plate from the T1A line
Relative height of T1 (mm)
T1H2
Vertical distance from the top of the manubrium to the line of the cranial
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T1 end-plate tangent. T1S
Angle between the superior endplate of T1 and the horizontal.
Thoracic inlet inclination (°)
TiI
Angle between lines drawn from the top of the manubrium to the centroid of
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T1 slope (°)
the cranial T1 end-plate and the horizontal.
T1AI
Difference between two angles (°)
TiI - T1AI
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T1-manubrium arch inclination (°)
*See Figure 1 and 2 for illustrations of the parameters.
Angle between lines drawn along the T1-manubrium arch and the horizontal
Angle between line drawn from the top of the manubrium to the centroid of the cranial T1 end-plate and a line drawn along the T1-manubrium arch
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Parameters
Male
Neck Pain
Group
Group
Group
23
23
25
30(6)
30(7)
0.99
32(5)
BMI (kg/m )
23(2)
23(3)
0.65
21(2)
Symptoms duration (yr)
NA
1.4(0.9)
VASn
NA
4.3(2.1)
NDI
NA
13.6(8.0)
All values are expressed as means (standard deviations).
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NA indicates not applicable.
p
p
25
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Group
p
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Age(yr)
Neck Pain
Female Pain-free
Number
Pain-free
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Table 2. Clinical baseline characteristics of the neck-pain and pain-free groups.
32(6)
0.99
21(3)
0.56
NA
2.1(1.3)
0.039
NA
5.3(2.1)
0.23
NA
15.0(5.4)
0.67
ACCEPTED MANUSCRIPT Table 3. Intraobserver and interobserver reliabilities of magnetic resonance imaging (MRI)
reliability
reliabilty
ICC (95%CI)
ICC (95%CI)
T1AD (mm)
0.97 (0.95-0.98)
0.90 (0.82-0.94)
TXD (mm)
0.99 (0.98-0.99)
0.98 (0.96-0.99)
T1H1 (mm)
0.98 (0.96-0.99)
0.88 (0.79-0.93)
T1H2 (mm)
0.96 (0.94-0.98)
0.90 (0.82-0.94)
T1S (°)
0.89 (0.81-0.94)
0.79 (0.65-0.88)
TiI (°)
0.98 (0.96-0.99)
0.94 (0.88-0.97)
T1AI (°)
0.98 (0.97-0.99)
0.94 (0.89-0.97)
TiI-T1AI (°)
0.94 (0.88-0.97)
0.93 (0.87-0.96)
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Inter-observer
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Intra-observer
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Parameters
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measurements calculated by intraclass coefficient (ICC) analysis.
ACCEPTED MANUSCRIPT Table 4. Bland–Altman analysis of the agreement between observers and the mean between-group differences for each parameter in both sexes.
Inter-observer
Mean differences
mean
mean
between groups
bias (95%CIs)
bias (95%CIs)
Male
T1AD (mm)
0.07 (0.51, 0.65)
3.04 (2.44, 3.64)
5.3
TXD (mm)
0.65 (0.02, 1.30)
-0.83 (-1.82, 0.16)
13
T1H1 (mm)
0.22 (0.08, 0.51)
0.54 (0.14, 0.94)
2.6
T1H2 (mm)
1.22 (0.58, 1.86)
-1.70 (-2.37, -1.03)
T1S (°)
-1.15 (-2.02, -0.27)
2.54 (1.54, 3.55)
TiI (°)
0.68 (0.20, 1.15)
-0.98 (-1.42, -0.54)
9.1
5.0
T1AI (°)
0.26 (-0.11, 0.62)
-0.12 (-0.52, 0.28)
4.8
1.2
TiI-T1AI (°)
0.43 (-0.06, 0.92)
-0.86 (-1.35, -0.38)
3.8
2.8
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Intra-observer
Female 5.3
7.2
1.1
6.3
4.6
2.1
3.7
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Table 5. Radiological parameters in the neck-pain and pain-free groups according to sex.
Parameters
free
p
Pain-
Neck Pain
Pain
free
Group
Group
Group
Group
T1AD (mm)
114(6)
108(5)
0.0018
103(5)
97(6)
0.0008
TXD (mm)
176(13)
163(17)
0.0069
155(10)
148(8)
0.008
T1H1 (mm)
26(5)
28(6)
ns
27(5)
28(4)
ns
T1H2 (mm)
30(11)
36(9)
0.032
32(8)
36(7)
0.039
T1S (°)
19(8)
21(5)
ns
19(5)
15(6)
0.021*
TiI (°)
44(8)
53(8)
0.0002
47(9)
52(7)
0.029
T1AI (°)
22(6)
27(5)
0.0058
22(7)
23(7)
ns
TiI-T1AI (°)
24(3)
28(5)
0.0021
27(4)
Values are expressed as means (standard deviations)
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p
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Pain-
Female
RI PT
Male
SC
Radiological
29(4)
0.013
ACCEPTED MANUSCRIPT
Table 6. Radiological predictors of chronic neck pain according to sex.
Unadjusted OR
p
Adjusted OR
(95%CI)
p
(95%CI)
1.003 (0.915, 1.099)
0.96
BMI
0.998 (0.943, 1.055)
0.94
T1AD (mm)
0.815 (0.705, 0.941)
0.005*
0.809 (0.681, 0.959)
TXD (mm)
0.940 (0.895, 0.988)
0.013*
na
T1H2 (mm)
1.078 (1.004, 1.157)
0.04*
TiI (°)
1.169 (1.059, 1.290)
0.002*
1.247 (1.060, 1.466)
TiI-T1AI (°)
1.303 (1.091, 1.555)
0.003*
na
0.015*
M AN U
Age
SC
Parameters
RI PT
Male
AC C
EP
TE D
ns
0.008*
Female Unadjusted OR
p
Adjusted OR
(95%CI)
p
(95%CI)
1.009 (0.908, 1.121)
0.86
BMI
0.878 (0.669, 1.153)
0.35
T1AD (mm)
0.814 (0.713, 0.930)
0.002*
0.823 (0.701, 0.966)
TXD (mm)
0.899 (0.829, 0.975)
0.01*
na
T1H2 (mm)
1.087 (1.002, 1.179)
0.045*
TiI (°)
1.085 (1.006, 1.170)
0.034*
TiI-T1AI (°)
1.204 (1.031, 1.406)
0.019*
0.017*
M AN U
Age
SC
Parameters
RI PT
ACCEPTED MANUSCRIPT
ns
na
EP
TE D
ns
*Adjustments made for the parameters significantly associated with neck pain in the univariate analysis.
AC C
OD; odd ratio, ns; not significant, *; significant, na; not applicable
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
100
105 110 Mean of T1AD
115
120
4 2 0 -2 -4 -6 -8
125
140
160 180 Mean of TxD
200
TE D
120
EP
5 4 3 2 1 0 -1 -2 -3 -4 -5
AC C
Difference between measures
95
SC
90
RI PT
5 4 3 2 1 0 -1 -2 -3 -4 -5
M AN U
Difference between measures
Difference between measures
ACCEPTED MANUSCRIPT
30
40
50 Mean of TiI
60
70
6 5
3 2 1 0 -1 85
95
105 Mean of T1AD
160 Mean of TxD
5 3 2 1 -1 -2 -3
180
200
EP
4
0
125
M AN U 140
AC C
Difference between measures
120
TE D
Difference between measures
12 10 8 6 4 2 0 -2 -4 -6
115
30
40
50 Mean of TiI
RI PT
4
SC
Difference between measures
ACCEPTED MANUSCRIPT
60
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT