Chronic neck pain is a common clinical problem for both the older and the younger generation [8,20]. The annual prevalence of cervicalgia has been reported to be from 30% to 50% [8,20]. Cervicalgia in more than 50% of people lasted for one year or more after the initial onset [2-5,7,22,28]. Though the cause of neck pain is not well established yet, many lesions such as degenerative changes of the disc and facet, ligament, fascia, muscle, nerve root, and dura could be the possibilities [30].

Although some publications presented that the change in cervical sagittal alignment was considered to be the most important factor on cervicalgia, other reports showed that there was no significant correlation between the loss of normal lordotic curve and cervicalgia [9,11-13,21,23,24,27]. The relationship between neck axial pain and cervical sagittal alignment is controversial.

The objective of this article was to study the relationship between cervical spine alignment measured by multiple methods and cervicalgia in young people who are in their twenties.

A total of 61 patients who visited our hospital were enrolled in our study. From these patients, 32 had cervicalgia, and they constituted the pain group (cervicalgia) and 29 of them had no cervicalgia (no cervicalgia). Only male patients were included in our study, and the median age of each group showed similar results (cervicalgia group: median age was 21 years; interquartile range [IQR], 20-21 years vs. no cervicalgia: median age was 21 years; interquartile range [IQR], 20-22 years).

In this study, we investigated the relationship between cervical alignment and cervical axial pain. Our findings revealed that the cervical vertical axis was the most relevant factor for cervicalgia. The Jackson stress line, neck tilting angle and thoracic inlet angle were also associated with cervical axial pain.

The normal lordotic curvature of the cervical spine allows efficient absorption of the load applied to the spine and enables fluid motion and optimal functions [16,32,33]. The posterior muscles, ligaments, and bony parts play crucial roles preserving this lordotic cervical curvature. Biomechanical articles show that the posterior parts of the cervical spine support 65% of the normal compressive forces but the anterior parts support 35% of them [29]. Degenerative changes in the cervical spine were accompanied with shortening of the anterior and posterior vertebral column and facet arthropathies, which results in an alteration of the sagittal balance of the spine [11,15,34]. When disruption of the posterior cervical parts occur, the anterior supports cannot withstand the increased axial loading, which causes the loss of normal lordotic cervical curve. At the biomechanical point of view, this loss of normal function of the cervical lordotic curvature could be a cause of cervicalgia due to muscular imbalance and overload of the partial parts of cervical spine [18,19,25]. As a result, the lordotic curvature is ideal for the cervical spine. There are many methods in measuring the cervical curvature, but identifying which method is best in measuring clinical manifestations such as cervicalgia was controversial.

Grob et al. showed that the segmental kyphotic changes in the cervical spine was not associated with clinical manifestations such as cervical axial pain and shoulder pain [14]. Our study revealed that the incidence of segmental kyphotic change in the cervicalgia group was higher than the no cervicalgia group. Compared to our study, Grob et al. included older age; hence, there was a higher incidence of segmental kyphotic changes in the cervical spine in their study [14]. This factor could have affected the results of their study. The kyphotic changes of the cervical disc spaces were degenerative, which caused axial overload in the anterior cervical column [1,6]. The other study revealed that this pathologic change in the cervical spinal disc was an important pathogenic factor of cervicalgia [30]. We hypothesized that the kyphotic change in each segment was affected by cervical axial pain.

We found that the Jackson physiologic stress line was associated with neck axial pain, while other methods measuring cervical lordosis were not. The relationship between sagittal alignment and neck symptoms was controversial. Harrison et al. used the circular modeling method to measure the sagittal alignment [17]. It showed that the pain groups were more associated with hypolordotic curvatures or large radii of curvature than the normal groups [17]. The retrospective study showed that the degree of cervical lordosis measured with Harrison’s tangent line had moderate diagnostic accuracy on chronic neck pain (sensitivity 0.46, specificity 0.97) or on acute neck pain (sensitivity 0.67, specificity 0.61) [17]. On the other hand, Grob et al. reported that the association between cervical spine alignment and neck pain in more than 100 people older than 45 years old had no relationship with any of the clinical manifestations (duration, frequency, intensity, radiating pain, neurologic dysfunction, and disability) and the global cervical curvature [14]. The other study on the association between radiologic findings of the cervical spine and neck symptoms in a Japanese community population showed that there is no association between cervical sagittal alignment and neck symptoms [10].

In our study, the patients suffering from cervical axial pain had higher TIA and NTA than the patients without cervicalgia. On the contrary, Knott et al. showed that a higher T1 slope was associated with cervical axial pain [26]. This study showed opposite results. Our report and the study by Knott et al. included small sample sizes; our study just enrolled 61 patients and Knott et al. included 52 patients with cervical pain and deformity. Therefore, we believe that a prospective study including a large population without degenerative changes was needed to investigate the effect of cervical parameters, such as NTA, T1 slope, and TIA to measure cervical axial pain.

The study by Tang et al. was the only report on the association of cervical sagittal alignment with clinical outcome [31]. This article included patients that underwent operations. Our study was the only one on cervical sagittal vertical alignment in patients with cervicalgia that did not undergo operations. Tang et al. showed that C2-C7 SVA was negatively correlated with SF-36 physical component score and was positively associated with NDI score, but VAS was not associated with cervical sagittal alignment [31]. As a result, they suggested that positive cervical alignment measured by C2-C7 SVA negatively affected quality of life. Our study revealed that the NDI and VAS score was also positively related with cervical vertical alignment. This correlation may be explained by the “Conus of Economy” theory; it means that the body preserves the balance by regulating the center of gravity over a perimeter that is as narrow as possible [31]. When applying this theory to cervical alignment, it is suggested that to increase sagittal vertical axis, the muscles in the posterior part of the cervical spine must be more contracted to preserve balance. We suggested that the chronic contraction of the posterior cervical muscles showed poor clinical manifestations.

Our article has some limitations. The first limitation is that our study is a retrospective study. The seconds, we only reviewed subject’s simple plain X-ray and CT scan, didn’t check MRI image so we didn’t analysis the degree of degeneration at each cervical level in all subjects. Third, all subjects were just soldiers doing compulsory services, so they may present the cervicalgia to obtain second benefits such as hospitalization, resting and exclusion from their jobs.

Our study showed that the cervical vertical axis was the most valuable method in correlating with clinical manifestations such as NDI score and VAS in early twenties soldiers. The cervical vertical axis was directly correlated with NDI and VAS; hence, we recommended that the spinal surgeons should measure cervical vertical axis for early twenties patients who suffer from cervicalgia without abnormality in radiologic exams.