DOI: https://doi.org/10.21203/rs.3.rs-2442916/v1
Purpose: To compare the variation characteristics of cervical sagittal position parameters and the correlation among nonspecific neck pain(NS-NP), 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 characteristics of the variation of parameters between the size of these parameters and gender differences were analyzed. Pearson’s or Spearman’s correlation was applied to analyze the association of cervical sagittal parameters of all patients between the three groups.
Results: There exist obvious 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 obviously 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, T1s were negatively associated with the SCA angle. There was a positive correlation between the C2-C7 Cobb angle and C7s, C2-C7 SVA and T1s, C2-C7 SVA and SCA, and C7s and T1s.
Conclusion: This study found that patients with CSR and CSM had higher SCA and C2-C7 SVA, and smaller C7s, T1s, and C2-C7 Cobb angles than patients with NS-NP; however, there has no obvious difference in sagittal parameters between the two types of cervical spondylosis. The SCA, C2-C7 SVA, C7s, T1s, and C2-C7 Cobb angles all had a strong correlation. Women were more common and had greater SCA than men in NS-NP patients, and women had smaller C7s and T1s than men.
With changes in lifestyle and work style, the number of patients with cervical spondylosis is rapidly increasing with a trend towards younger patients[1].Cervical spondylosis is a typical neurodegenerative disease. Therefore, when diagnosing and treating this disease, it is necessary to strictly check the degree of cervical degeneration, which is also the focus of research in this field.[1, 2].
In recent years, spinal sagittal balance has become a hot topic[3]. Cervical spine balance, including cervical Cobb angle, sagittal axial displacement (SVA), and many cervicothoracic junction parameters, maintain the sagittal balance of the spine are key indicators for evaluating spinal stability[4–6]. The cervical vertebrae are a complex and mobile structure with the main task of keeping the head above the body and gait balance[5, 7]. Cervical spine disease may associated with complex compensatory mechanisms, caused much energy expenditure, enhanced muscle strength, and pain[8]. A simple radiograph is the most important tool for assessing spinal alignment. Therefore, the analysis of cervical sagittal parameters is important for assessing sagittal balance and predicting clinical outcomes. According to recent reports in the relevant literature, three key cervical sagittal parameters, the spine cranial angle (SCA), C7 slope (C7s), T1 slope (T1s) and C2-7 sagittal axial distance (C2-C7 SVA), are the focus of future studies[4, 8]. SCA is an easily neglected but essential parameter for measuring the sagittal balance and has attracted much attention in recent years[9–12]. By measuring various sagittal position parameters on cervical radiographs, we can help us recognize and diagnose diseases.
The difference in cervical sagittal position parameters before operation for cervical diseases has received little attention. This research aimed to compare the variation characteristics and correlation of cervical sagittal position parameters among nonspecific neck pain, CSR, and CSM. For spine surgeons, reliable, simple, and repeatable parameters are important for analyzing cervical stability and providing optimal strategies for the thrapy and intervention of cervical diseases.
The institutional review board approved the current retrospective research. 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 with spinal cord type and neurogenic cervical spondylosis confirmed by CT, MRI and physical examination; 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 and (2) incomplete patient information data records. 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.
As shown in Fig. 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. The C2-C7 Cobb angle, C2-C7 SVA, T1 slope (T1s), C7 slope (C7s) and spinal angle (SCA) were tested on cervical radiographs. The definition of measurement variables is shown in Table 4[4, 13, 14].
Two independent observers were employed to measure the parameters. Then, two measurements were taken by two spine surgeons for each covariate, and the intragroup correlation coefficient (ICC) was analyzed as mean measurements. SPSS26.0 software was used for statistical analysis of the experimental data. The results showed that the consistency among observers reached a high level, and the ICC value was in the range of 0.976 to 0.984. The measurement data are described by means of mean ± standard deviation, and the counting data are described based on percentage. 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 t test was used. The chi-square test was used for classified data. Pearson’s or Spearman’s correlation was applied to assess the association between all patients' cervical sagittal parameters among different groups. P < 0.05 was set as the significant judgement threshold.
Up to 236 patients were enrolled in the research. According to the diagnosis, the research object were divided into three groups: in which 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 were listed in Table 1. There exist obvious 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 has no obvious differences in the indexes of height, weight or BMI .
Table 2 summarizes the values and changes in each cervical sagittal parameter among different groups. There exist obvious 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 for a two-by-two comparison of each imaging parameter. For parameter of C2-C7 Cobb angle, the mean value of NS-NP group was obviously greater compared to 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 obviously lower compared to 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 compared to 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 NS-NP group was also higher compared to 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 NS-NP group was obviously lower compared to 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). But there were no obvious differences in cervical sagittal parameters between the CSR, CSM group (P > 0.05).
Pearson’s or Spearman’s correlation was carried out to detect correlations between different cervical sagittal parameters in all patients among the three groups (Table 3). There exist positive associations between the C2-C7 Cobb angle and C7s (r = 0.618, 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), T1s and SCA (r=-0.620, P < 0.01).
To observe the differences in thoose 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 obviously larger in men compared to 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). For 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 exsit no obvioust 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 is responsible for many key physiological functions. It can be judged that the possibility of degenerative changes in the cervical spine is high [7]. The sagittal balance and physiological curvature of the cervical spine are important for the maintenance of its function, and are closely related to the biomechanical properties of the cervical spine[3, 7]. The treatment of cervical spine disease is a major challenge. To handle complex cervical spine diseases, it is necessary to comprehend cervical spine biomechanics and normative data on cervical alignment[5]. At present, increasing attention has been given to research on cervical sagittal plane parameters by spinal surgeons[13, 15–18]. Normal values of cervical sagittal parameters have been identified by recent investigations, and these normal values vary greatly[5, 13, 19, 20]. However, few studies have compared the variation characteristics and correlation of cervical sagittal plane parameters between patients with nonspecific neck pain and CSR, CSM.
The results ot this paper reflected that the C2-C7 sagittal axial distance (SVA) and spinal cranial angle (SCA) of NS-NP group were obviously greater compared to those of CSR and CSM groups, while the C2-C7 anterior convex angle, C7s and T1s of NS-NP group were obviously smaller than those of CSR and CSM groups. This result is similar to that of previous researches[13, 17, 18]. 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 head's center of gravity, caused 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[19–21]. 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 cervical spine in the population of patients with degenerative cervical spondylosis is affected by large variations[17]. As reported by Jouibari et al.[13], there exist 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 those parameters relative to cervical spondylosis cases and tend to present similar results as the normal population.
We performed a correlation analysis of those parameters, and showed a significant negative correlation between the C2-C7 Cobb angle, C2-C7 SVA and T1 slope and SCA angle, which is in accordance with previous researches[4, 10, 12]. 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[9, 10]. Wang et al. [9] found that patients with higher SCA had a lower T1 slope (T1s) ,both preoperatively, postoperatively stage. The results of this study also reflected that ,there exist a positive association between the C2-C7 Cobb angle and C7 slope, C2-C7 Cobb angle and T1 slope, C2-C7 SVA and SCA, and C7 slope and T1 slope, while the C2-C7 Cobb angle was negatively associated to C2-C7 SVA. These correlations implied that the sagittal curvature 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[22, 23]. When the cervical spine is in prolonged flexion and the muscle balance along the cervical spine is altered, the neck muscles are subjected to abnormal mechanical loading, caused ligament and joint capsule laxity and lower cervical curvature, i.e., decreased C2-C7 angle[13, 24]. 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 [3]. The research results in this paper also show that C2-C7 Cobb angle has a positive correlation with T1 and C7 slopes, which indicates that when this angle is reduced, T1 and C7 slopes will also be reduced to compensate for this and reduce the related imbalance effects [22, 25–27]. 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 [5, 27, 28]. This compensation mechanism is mainly realized through the excessive contraction of the spine and small intervertebral disc joints, which will lead to an increase in the speed of spinal degeneration and many corresponding clinical symptoms, such as low back pain and shoulder pain, which will have a very negative impact on the health of patients[25]. Hence, spine surgeons should consider the patient's cervical sagittal balance during surgery process and repair cervical curvature, and studying cervical sagittal balance may help spine surgeons develop better treatment strategies[26–28].
We also performed a comparative analysis of sex differences in different 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 workers, medical workers and professional drivers, who has high risk to encounter 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[29]. 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[30].
This study reports for the first time the characteristics and correlation analysis of changes in cervical sagittal parameters between nonspecific neck pain cases and those with neurogenic and spinal cervical spondylosis. It further clarifies that these parameters has closel association with the cervical spine disease and emphasizes the meaning of cervical sagittal balance. Lateral radiographs of the cervical spine, as a simple, convenient, and noninvasive examination, are necessary to assess these kind of sagittal balance. Of course, there are also some shortcomings. First, this study only evaluated the local sagittal position parameters, which may have certain limitations on the conclusion. The use of sagittal radiographs of the whole spine can be enhanced. Second, this study is a single-institution center study. More research in this area is needed to supplement and confirm the above results.
This study found that patients with CSR and CSM had higher SCA and C2-C7 SVA and smaller C7s, T1s, and C2-C7 Cobb angles than patients with NS-NP; however, there has no obvious difference in sagittal parameters between two types of cervical spondylosis. SCA, C2-C7 SVA, C7s, T1s, and C2-C7 Cobb angles all had a strong correlation. Women were more common and had greater SCA than men among NS-NP patients, and women had smaller C7s and T1s than men.
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.
Tables 1 to 4 are available in the Supplementary Files section.