DOI: https://doi.org/10.21203/rs.3.rs-2691173/v1
Purpose: Previous studies have shown that cervical sagittal alignment is strongly associated with cervical deformity, myelopathy,and cervical adjacent-segmental disease, and those cervical sagittal parameters are correlated with health-related quality of life, while less attention has been paid to cervical sagittal balance in various cervical disorders. This study aimed to compare cervical sagittal parameters between patients with nonspecific neck pain(NS-NP) and patients with cervical spondylotic radiculopathy(CSR) and cervical spondylotic myelopathy(CSM).
Methods: We retrospectively included 236 patients divided into three groups, NS-NP, CSR, and CSM, and collected general information and cervical sagittal parameters of such kind patients. The variation of parameters between the size of these parameters and gender differences were analyzed. Pearson’s or Spearman’s correlation was applied to analyzethe association of cervical sagittal parameters of all patients between the three groups.
Results: There were significant differences in age and sex among the three groups (P<0.001), among which the NS-NP group was the youngest, and NS-NP was more common in women. The parameters of cervical sagittal position were significantly different among the three groups (P<0.05). Pearson’s or Spearman’s correlation result showed that the C2-C7 Cobb angle was negatively associated with C2-C7 SVA, and the C2-C7 Cobb angle, T1 slope (T1s) were negatively associated with the spino-cranial angle (SCA). There was a positive correlation between the C2-C7 Cobb angle and C7 slope (C7s), C2-C7 SVA and T1s, C2-C7 SVA and SCA, and C7s and T1s.
Conclusion: This study showed that between the three groups, patients with non-specific neck pain had larger C7s, T1s, and C2-C7 Cobb angle and smaller SCA and C2-C7 SVA; and among patients with NS-NP, women had larger SCA and smaller C7s and T1s. The smaller anteroposterior (AP) diameter of the thoraxin women might be the possible explanation for this difference.
Neck pain has long been a concern, and common causes may be neurogenic cervical spondylosis, spinal cord cervical spondylosis, and acute neck pain[1]. Previous studies have reported a close association between cervical sagittal alignment and cervical spine disease. Sagittal alignment and balance of the cervical spine, including cervical Cobb angle, sagittal vertical axis (SVA), and a series of parameters at the cervicothoracic junction, maintain cervical sagittal balance and are important indicators for evaluating cervical degeneration and cervical spine stability[2-4]. Therefore, analysis of cervical sagittal parameters is important to assess cervical sagittal balance and predict clinical outcomes.
Much work has been done on the sagittal parameters of the cervical spine in patients with neck pain. Early imaging studies of the cervical spine by Gore et al. suggested that degenerative changes in C6/C7 may be considered a risk factor for development of neck pain in the future[5].In addition, Moon and Choi et al.[6] conducted a cross-sectional study of Air Force pilots, and they found a lower C2-C7 angle in subjects with neck pain. In 2019, Jouibari et al.[7] further showed that the population of patients with non-specific neck pain had significantly lower the slope of the upper endplate of T1 vertebrae body (T1 slope) compared to the healthy population. And they suggested that this may be related to a compensatory mechanism that shifts the center of head gravity back to the spinal axis. On the other hand, some studies have proposed global sagittal balance measurements, and Grob et al. conducted a study of global sagittal parameters in patients with neck pain and found no significant differences between subjects with and without neck pain[8].This fnding was further supported by other studies[9, 10]. Compared to the above studies, we believe that the sagittal parameters and study population categories related to the preoperative cervical spine are slightly underrepresented. According to recent reports in the relevant literature, three key cervical sagittal parameters, spino-cranial angle (SCA), C7 slope (C7s), T1 slope (T1s) and C2-7 sagittal vertical axis (C2-C7 SVA), are the focus of future studies[2, 11]. SCA is an easily neglected but essential parameter for measuring the sagittal balance of the cervical spine and has attracted much attention in recent years[12-15].The present study can demonstrate well the correlation between SCA and other parameters. Also, this study elevated the control study population to a more accessible cervical spine patient.
Thus, this study aimed to compare the cervical sagittal parameters between nonspecific neck pain (NS-NP) and cervical spondylotic radiculopathy (CSR) and cervical spondylotic myelopathy (CSM) and to illustrate the relationship between each cervical parameter.
The institutional review board of our institution approved the current retrospective research, and a waiver of consent was acquired(Approval 2022-113-1). This paper assessed patients who presented to our hospital with posterior neck discomfort between January 2020 and October 2022. Inclusion criteria: (1) patients with nonspecific neck pain with degenerative cervical spine disease excluded by consultation, physical examination and imaging; (2) patients diagnosed with cervical spondylotic radiculopathy and cervical spondylotic myelopathy after hospitalization; and (3) complete imaging and patient information data. Exclusion criteria: (1) history of previous spinal surgery, cervical spine infection, cervical spine trauma, spinal tumor and congenital spinal deformity; (2) incomplete patient information data records; and (3) The T1 vertebrae cannot be fully revealed on cervical X-ray for various reasons (e.g., patients with obesity, short neck, etc.) and other conditions. Ultimately, 236 patients were selected as the research objective, and the general characteristics of them, such as age, sex, height, weight, were recorded prior to imaging evaluation.
Radiological measurement
As shown in Figure 1, lateral cervical spine films were obtained for all subjects using the Picture Archiving and Communication System (PACS), with the subjects in a neutral position and looking straight ahead. The C2-C7 angle, C2-C7 SVA, T1 slope (T1s), C7 slope (C7s) and spinal angle (SCA) were measured on cervical radiographs. The definition of measurement variables is shown in Table 4[2, 7, 16].
Statistical analysis
Measurements were determined by two independent observers. Then, two measurements were taken by two spine surgeons for each covariate, and the intragroup correlation coefficient (ICC) was analyzed as the mean of each observer's measurements. Intra- and interobserver agreement was excellent, with ICC values ranging from 0.976 to 0.984. The measurement data are shown as the mean ± standard deviation, and the counting data are totals and percentages. SPSS software (version 26.0; SPSS, Chicago, Illinois) was adopted to perform all analyses. If the data between the three groups met the normality and homogeneity of variance test, one-way ANOVA was used, and the Bonferroni test was used for pair-to-group comparison. If the variances were inconsistent, the Welch test was used, and pairwise comparisons between groups were performed using Tamhane's T2 test. The Kruskal‒Wallis test was used for data with nonnormality or inconsistent variance. The parameters between the sexes within the group approximately met the normality and homogeneity of variance test, and an independent t test was used. The chi-square test was used for classified data. Pearson’s or Spearman’s correlation analysis was used to assess the correlation between all patients' cervical sagittal parameters between the three groups. P<0.05 was considered to be statistically significant.
General data
A total of 236 patients were enrolled in the study. According to the diagnosis, the patients were divided into three groups: 70 patients with NS-NP (22 male cases and 48 female cases), 74 patients with CSR (37 male cases and 37 female cases), and 92 patients with CSM (58 male cases and 34 female cases). The characteristics of these patients are summarized in Table 1. There were significant differences in age and sex among the three groups (P<0.001); the age of the NS-NP group was the youngest (41.77±12.00), and NS-NP was more common in women. There were no significant differences in height, weight or BMI (P>0.05).
Cervical imaging parameters
Table 2 summarizes the values and changes in each cervical sagittal parameter among the three groups. There were significant differences in each cervical sagittal parameter between the three groups for the C2-C7 Cobb angle (P<0.001), C2-C7 SVA (P=0.003), C7s (P=0.009), T1s (P=0.008) and SCA (P=0.002).
Figure 2 shows the differences between the three groups for a two-by-two comparison of each imaging parameter. For the C2-C7 Cobb angle, the mean value of the NS-NP group was significantly greater than that of the CSR group (16.00±8.86 vs. 9.65±12.11, P<0.001) versus the CSM group (16.00±8.86 vs. 9.73±12.02, P<0.001). For C2-C7 SVA, the mean value of the NS-NP group was significantly lower than that of the CSR group (1.78±0.77 VS.2.32±0.90, P<0.01) and CSM groups (1.78±0.77 VS. 2.19±0.99, P<0.05). For C7s, the mean value of the NS-NP group was higher than that of the CSR group (19.84±6.48 VS. 16.77±7.86, P<0.05) and CSM groups (19.84±6.48 VS. 16.60±7.01, P<0.05). For T1s, the mean value of the NS-NP group was also higher than that of the CSR group (23.51±6.11 VS.19.95±8.12, P<0.05) and CSM groups (23.51±6.11 VS. 20.30±7.94, P<0.05). For SCA, the mean value of the NS-NP group was significantly lower than that of the CSR group (76.81±7.76 VS.81.80±8.86, P<0.01) and CSM groups (76.81±7.76 VS. 80.61±9.30, P<0.05). However, there were no significant differences in cervical sagittal parameters between the CSR group and the CSM group (P>0.05).
Correlation analysis of cervical sagittal parameters
Pearson’s or Spearman’s correlation analysis was performed to determine correlations between different cervical sagittal parameters in all patients among the three groups (Table 3). There were positive correlations between the C2-C7 Cobb angle and C7s (r=0.618, P<0.01), C2-C7 Cobb angle and T1s (r=0.653, P<0.01), C2-C7 SVA and C7s (r=0.181, P<0.01), C2-C7 SVA and T1s (r=0.154, P<0.05), C2-C7 SVA and SCA (r=0.285, P < 0.01), and C7s and T1s (r = 0.861, P < 0.01). There were negative correlations between the C2-C7 Cobb angle and C2-C7 SVA (r=-0.265, P<0.01), C2-C7 Cobb angle and SCA (r=-0.841, P<0.05), C7s and SCA (r=-0.678, P<0.01), and T1s and SCA (r=-0.620, P<0.01).
Sex-related changes in cervical sagittal parameters
To observe the differences in cervical sagittal parameters between sexes, the three case groups were grouped separately according to sex in this study (Table 2). In the NS-NP group, both C7s and T1s were significantly larger in men than in women (23.28±6.24 vs. 18.27±6.01, P<0.01) and T1s (26.16±5.07 vs. 22.29±6.21, P<0.05), while SCA was smaller in men than in women (72.66±10.14 vs. 78.71±5.54, P<0.05). In the CSM group, the C2-C7 Cobb angle was greater in men than in women (11.58±13.61 vs. 6.58±9.11, P<0.05), and the SCA in men was significantly smaller than in women (78.88±10.39 vs. 83.55±6.14, P<0.01). There were no significant differences in cervical sagittal parameters between men and women in other groups (P>0.05).
Because the cervical spine is more complex than the thoracolumbar spine and has a greater range of motion, it supports the weight of the head and is responsible for many important physiological functions. Therefore, the cervical spine is more susceptible to degenerative changes[17]. Sagittal balance of the cervical spine and normal cervical curvature and alignment play a critical role in maintaining the biomechanical properties and normal movement of the cervical spine[17, 18]. Numerous studies have determined the sagittal parameters of the cervical spine in people with neck pain versus healthy subjects and have found that these parameters vary greatly[3, 7, 19, 20]. However, we are the first to propose a comparison of cervical sagittal parameters between patients with non-specific neck pain and patients with cervical spondylotic radiculopathy and cervical spondylotic myelopathy.
Our results showed that the C2-C7 sagittal axial distance (SVA) and spinal cranial angle (SCA) of patients in the NS-NP group were significantly greater than those in the CSR and CSM groups, while the C2-C7 anterior convex angle, C7s and T1s of patients in the NS-NP group were significantly smaller than those in the CSR and CSM groups. This is similar to the results of previous studies[7, 21, 22]. In people with degenerative cervical spondylosis, the physiological curve of the cervical spine becomes progressively straighter or more lordotic, which leads to a forward shift of the head's center of gravity, resulting in a progressive increase in C2-C7 SVA and SCA and an increase in C7s and T1s to compensate for the sagittal balance of the spine. In contrast to CSR and CSM patients, NS-NP patients may have mainly localized muscle fatigue or muscle stiffness, and patients often present with complaints of a localized neck pain[19, 20, 23]. However, in slowly progressive diseases, such as myelopathy, the nature of patients' complaints is less likely to be localized, and their perception of disability suggests that the sagittal position of the cervical spine in the population of patients with degenerative cervical spondylosis is affected by large variations[22]. As reported by Jouibari et al.[7], there were no differences in the changes in cervical sagittal parameters in patients with neck pain compared with the asymptomatic population, except for the decrease in T1s. This also better explains our results showing that NS-NP patients are less affected by changes in cervical sagittal parameters relative to patients with cervical spondylosis and tend to present similar results as the normal population.
We performed a correlation analysis of cervical sagittal parameters, and the results of our study showed a significant negative correlation between the C2-C7 Cobb angle, C2-C7 SVA and T1 slope and SCA angle, which is consistent with previous findings[2, 13, 15]. In recent studies, a new cervical sagittal parameter, SCA, has gradually been proposed to assess the relationship of SCA with other cervical sagittal parameters and postoperative recovery indices. It has been proposed that SCA can be considered another key parameter to predict imbalance and that higher SCA is positively correlated with NDI in cervical spine patients[12, 13]. Wang et al.[12] reported that patients with a higher SCA had a lower T1 slope (T1s) and C2-C7 Cobb angle, both preoperatively, postoperatively and at follow-up. The results of this study also showed positive correlations between the C2-C7 Cobb angle and C7 slope, C2-C7 Cobb angle and T1 slope, C2-C7 SVA and C7 slope, C2-C7 SVA and T1 slope, C2-C7 SVA and SCA, and C7 slope and T1 slope, while the C2-C7 Cobb angle was negatively correlated with C2-C7 SVA. These correlations indicate that the sagittal curvature of the cervical spine is closely related to the sagittal displacement of the cervical spine. In degenerative cervical spine diseases, cervical curvature changes are one of the most common radiographs[24, 25]. When the cervical spine is in prolonged flexion and the muscle balance along the cervical spine is altered, the muscles and ligaments of the neck are subjected to abnormal mechanical loading, resulting in ligament and joint capsule laxity and loss of cervical physiological curvature, i.e., decreased C2-C7 angle[7, 26]. When the C2-C7 Cobb angle decreases, the center of gravity of the head (CGH) and C2 vertebrae moves forward, which will lead to the same increase of C2-C7 SVA to maintain balance and offset the adverse effects caused by CGH moving forward[18]. In addition, we found that the C2-C7 Cobb angle was positively correlated with the T1 slope and C7 slope, suggesting that when the C2-C7 Cobb angle decreases, the T1 slope and C7 slope exhibit a compensatory decrease to restore the imbalance caused by the CGH forward shift[24, 27-29]. When the physiological curvature of the cervical spine is reduced, many parameters of the cervical spine will change, and there is correlation between these changes. Relevant experimental research results show that the changes of cervical sagittal position are closely related to the complex compensation mechanism, which is also related to the spinal alignment, such as thoracic kyphosis and sacral inclination[3, 4, 30]. In general, the implementation of compensatory mechanisms relies on excessive muscle contraction and excessive tension in the spine and small disc joints, which can further accelerate the progression of spinal degeneration and cause a series of related clinical symptoms, such as low back pain, neck pain, and shoulder pain[31]. Therefore, spine surgeons should consider the patient's cervical sagittal balance during cervical spine surgery and try to restore normal cervical physiological curvature, and studying cervical sagittal balance may help spine surgeons develop better treatment strategies[32-34].
We also performed a comparative analysis of sex differences in cervical sagittal parameters. The age of patients in the NS-NP group was younger, and these findings are similar to those reported by Cohen et al.[1], which are more common in middle-aged and young people, such as office and computer workers, manual laborers, medical workers and professional drivers, who are more likely to experience neck and shoulder pain than others. Among patients with nonspecific neck pain, we found that female patients were often more common than male patients, which was similar to some reports[19, 20]. This may be because the anteroposterior (AP) diameter of the thorax is significantly smaller in women than in men with chronic neck pain. The size of the thoracic AP may be a predictor of neck pain, and the AP diameter of the uppermost thorax, which is the basis of head and neck motion fixation, is an important factor. The smaller the bottom, the more likely and frequent the head is to go beyond it, especially when the head is moving forward[35]. This explains the greater SCA in women than in men in the NS-NP group as well as the fact that the cervical spine compensates for the forward shift of the head's center of gravity by decreasing C7s and T1s[27].
This study reports for the first time the comparison of cervical sagittal parameters between patients with non-specific neck pain and those with cervical spondylotic radiculopathy and cervical spondylotic myelopathy. It further clarifies that these parameters are closely related to cervical spine disease and emphasizes the importance of cervical sagittal balance. Lateral radiographs of the cervical spine, as a simple, convenient, and noninvasive examination, are necessary to evaluate the sagittal balance of the cervical spine. Of course, there are also some shortcomings. First, the lack of clinical data in this study and the failure to compare preoperative and postoperative cervical sagittal parameters and some clinical outcomes in cervical spondylotic radiculopathy and cervical spondylotic myelopathy will be a problem that we need to address in our subsequent studies. Second, this study only evaluated the parameters of the local sagittal position of the cervical spine, which may have certain limitations on the conclusion. The use of sagittal radiographs of the whole spine can be enhanced. Finally, this study is a single-institution center study. More research in this area is needed to supplement and confirm the above results.
This study showed that between the three groups, patients with non-specific neck pain had larger C7s, T1s, and C2-C7 Cobb angle and smaller SCA and C2-C7 SVA; and among patients with NS-NP, women had larger SCA and smaller C7s and T1s. The smaller anteroposterior (AP) diameter of the thorax in women might be the possible explanation for this difference. There was a strong correlation between each cervical sagittal parameter.
Acknowledgements
We are grateful to all study participants for their participation in the study.
Authors’ contributions
DLY and ZW conceived and designed the study, TL and ST collected, TL, JZZ, MZH, WYD and LLD analyzed and interpreted the patient data. TL wrote the paper. All authors read and approved the final manuscript.
Funding
None.
Availability of data and materials
The datasets generated and analysed during the current study are availabled from the corresponding author on reasonable request.
Ethics approval and consent to participate
The study was approved by the ethical committee of The Third Affiliated Hospital of Hebei Medical University. The study the need for written informed consent was waived by the ethical committee of The Third Affiliated Hospital of Hebei Medical University due to retrospective nature of the study. All methods were carried out in accordance with relevant guidelines and regulations.
Consent for publication
Not applicable.
Competing interests
None of the authors has any potential confict of interest.
Table 1 Patient backgrounds among the three groups, means±SD.
Variables |
Patients with NS-NP |
Patients with CSR |
Patients with CSM |
P-Value |
No. of patients(n) Age(year) Male/Female Weight(kg) Height(m) BMI(kg/m2) |
70 41.77±12.00 22/48 68.04±7.06 1.66±0.08 24.84±2.97 |
74 51.35±9.63 37/37 68.45±9.64 1.65±0.08 25.18±2.51 |
92 54.10±11.70 58/34 68.80±10.98 1.66±0.08 24.91±3.11 |
<0.001*** <0.001*** 0.861 0.516 0.757 |
NS-NP: nonspecifc neck pain; CSR: cervical spondylotic radiculopathy; CSM: cervical spondylotic myelopathy; BMI: body mass index;***: P<0.001.
Table 2 Cervical sagittal alignment by sex among the three groups, means±SD.
Variables |
Patients with NS-NP |
Patients with CSR |
Patients with CSM |
P-Value |
C2–C7 Cobb angle (deg) Total Male Female P-Value C2-C7 SVA (cm) Total Male Female P-Value C7 slope(deg) Total Male Female P-Value T1 slope(deg) Total Male Female P-Value SCA(deg) Total Male Female
|
16.00±8.86 18.58±10.21 14.81±8.01 0.136
1.78±0.77 1.94±0.87 1.72±0.72 0.271
19.84±6.48 23.28±6.24 18.27±6.01 0.002**
23.51±6.11 26.16±5.07 22.29±6.21 0.013*
76.81±7.76 72.66±10.14 78.71±5.54 0.014* |
9.65±12.11 10.21±12.73 9.09±11.60 0.695
2.32±0.90 2.37±0.89 2.27±0.92 0.616
16.77±7.86 17.17±8.50 16.38±7.24 0.668
19.95±8.12 20.50±8.61 19.41±7.67 0.570
81.80±8.86 81.06±9.36 82.54±8.39 0.477 |
9.73±12.02 11.58±13.61 6.58±9.11 0.034*
2.19±0.99 2.17±1.06 2.21±0.86 0.871
16.60±7.01 17.50±7.61 15.07±5.63 0.191
20.30±7.94 21.13±9.00 18.88±5.56 0.109
80.61±9.30 78.88±10.39 83.55±6.14 0.008** |
<0.001**
0.003**
0.009**
0.008**
0.002**
|
NS-NP: nonspecifc neck pain; CSR: cervical spondylotic radiculopathy; CSM: cervical spondylotic myelopathy; deg: degrees; SCA: spinal cranial angle.
* Significant correlation at the 0.05 level (2 tailed)
** Significant correlation at the 0.01 level (2 tailed)
Table 3 Comparison of cervical sagittal parameters among the three groups.
|
Age |
BMI |
C2–C7 Cobb angle |
C2-C7 SVA |
C7 slope |
T1 slope |
SCA |
Sex |
0.031 |
0.023 |
0.085 |
0.090 |
0.118 |
0.135* |
-0.167** |
Age |
|
-0.011 |
-0.055 |
0.055 |
-0.028 |
-0.031 |
0.034 |
BMI |
|
|
-0.039 |
0.036 |
-0.072 |
-0.001 |
0.109 |
C2–C7 Cobb angle |
|
|
|
-0.265** |
0.618** |
0.653** |
-0.841** |
C2-C7 SVA |
|
|
|
|
0.181** |
0.154* |
0.285** |
C7 slope |
|
|
|
|
|
0.861** |
-0.678** |
T1 slope |
|
|
|
|
|
|
-0.620** |
SCA: spinal cranial angle
* Significant correlation at the 0.05 level (2 tailed)
** Significant correlation at the 0.01 level (2 tailed)
Table.4 Defnition of all parameters used: parameters description.
C2–C7 Cobb angle
C2-C7 SVA
C7 slope
T1 slope
SCA
|
Angle between the lower plate of C2 and the lower plate of C7.
The distance from the posterior, superior corner of C7 to the plumbline from the centroid of C2.
Angle between a horizontal line and the superior endplate of C7.
Angle between a horizontal line and the superior endplate of T1.
The angle is defined between the C7 slope and the straight line joining the middle of the C7 end plate and the middle of the sella turcica.
|
SCA: spinal cranial angle