Comparison of Radiographic Cervical Sagittal Alignment Parameters in Patients With Nonspecific Neck Pain, Degenerative Neck Pain, and Healthy Individuals

Introduction

Neck pain is a common musculoskeletal disorder, with a lifetime prevalence reaching 66% [1]. The persistence of neck pain is partly attributed to modern lifestyle factors, including prolonged sitting and increased use of electronic devices [2]. Therefore, understanding these biomechanical and pathophysiological mechanisms is essential for developing effective treatment strategies.

Clinically, neck pain is classified as either nonspecific or degenerative based on structural pathology [3]: nonspecific neck pain lacks an identifiable structural cause, whereas degenerative neck pain involves identifiable structural abnormalities, such as disc herniation or spinal stenosis [4,5]. However, nonspecific neck pain remains poorly defined, complicating clinical decision-making and limiting targeted treatment. Currently, specific and nonspecific neck pain are differentiated based on clinical examination and reported symptoms. However, this approach is limited, as symptoms overlap between categories and lack of objective criteria [6]. Moreover, the inherent heterogeneity of nonspecific neck pain further complicates research and treatment decisions. Therefore, objective radiographic measures may improve the differentiation of pain subtypes and guide management.

Previous radiographic studies have demonstrated that neck pain occurs both in the presence and absence of identifiable radiological abnormalities [7]. However, most radiological evaluations have focused on disc spacing and cervical lordotic alignment, and comparative radiological analyses between specific and nonspecific subtypes remain limited [8,9]. Moreover, alterations in sagittal parameters can substantially modify the load distribution across vertebral segments, increase muscular and ligamentous stress, and compromise neural foraminal dimensions [10,11]. Normal cervical sagittal alignment is typically defined by a C2–C7 sagittal vertical axis (SVA) of less than 40 mm, a spino–cranial angle (SCA) of 75° to 85°, and a T1 slope less than 25°. Deviations from these normative ranges, including increased SVA, mismatch between T1 slope and cervical lordosis, and reduced SCA, are associated with sagittal imbalance. They can also contribute to altered biomechanical loading and the development of neck pain [12,13].

In a previous study, patients with nonspecific neck pain exhibited reduced T1 slope compared with healthy controls, with no change in global cervical lordosis, suggesting segmental rather than global alignment alterations [14]. Despite these reference values, the relationship between global cervical sagittal balance and different neck pain subtypes remains unclear. Moreover, no study has systematically compared SVA, SCA, and disc features within a single framework. Therefore, in the present study, we aimed to compare cervical sagittal alignment parameters among patients with nonspecific neck pain, degenerative neck pain, and asymptomatic controls. To this end, we evaluated radiographic measures, including SVA, SCA, and intervertebral disc height, to identify structural differences among the 3 groups.

Material and Methods

ETHICS STATEMENT:

The study protocol was approved by the Institutional Review Board of Inje University (approval no. 2025-08-034). This retrospective study used radiographic and clinical data obtained from routine health screening. The requirement for additional informed consent was waived following institutional policy, as all participants had provided consent for the use of their medical data for research purposes. No additional procedures or radiation exposure were involved. To ensure participant confidentiality, all data were anonymized before analysis, and personal identifiers were removed. Access to the data was restricted to authorized study personnel. All methods used were in accordance with relevant institutional and national guidelines.

STUDY DESIGN AND SETTING:

This retrospective observational study utilized data obtained between January 2023 and January 2025 from the Department of Korean Medicine, Yeonsan Dang Dang Hospital, Busan, Republic of Korea.

PARTICIPANTS:

This retrospective study included all eligible patients identified during the study period; therefore, a priori sample size calculation was not performed. A post hoc power analysis was conducted using G*Power software (version 3.1.6; Franz Faul, Kiel University, Kiel, Germany) for a one-way analysis of variance (ANOVA) with 3 groups: nonspecific neck pain, degenerative neck pain, and asymptomatic controls. Based on group differences in the primary alignment variables (SVA and SCA), the effect sizes corresponded to Cohen’s f values of 0.39 to 0.42, with a power ranging from 0.95 to 0.97 at α=0.05. These findings indicate that the present sample size (n=70) was sufficient to detect meaningful intergroup differences.

A total of 70 participants were included in the analysis, including 25 patients with nonspecific neck pain, 20 patients with degenerative neck pain, and 25 asymptomatic healthy controls (Figure 1). Clinical diagnoses were performed by a licensed Korean Medicine Doctor (J.S.), one of the authors, with expertise in musculoskeletal disorders, using standardized criteria applied uniformly across all groups.

The inclusion criteria were as follows: (1) age between 18 and 70 years; (2) for the nonspecific neck pain group, (i) a primary concern of neck pain located at least partly within the anatomical region defined by Merskey, bounded superiorly by the superior nuchal line, inferiorly by an imaginary line through the tip of the first thoracic spinous process, and laterally by sagittal planes tangential to the lateral borders of the neck; (ii) pain duration of less than 3 months, with a pain-free interval of at least 1 month before the onset; (iii) pain intensity higher than 2 on a 10-point numerical rating scale; and (3) for the degenerative neck pain group, radiological or clinical diagnosis of structural pathology such as cervical disc herniation and stenosis.

Pathological causes of neck pain were systematically excluded in the nonspecific neck pain group through the following: (1) review of lateral cervical radiographs confirming the absence of structural abnormalities, such as disc space narrowing, osteophyte formation, and vertebral fracture; (2) clinical neurological examination excluding radiculopathy or myelopathy, including the absence of motor weakness, sensory deficits, or abnormal deep tendon reflexes; and (3) application of clinical and imaging criteria to exclude inflammatory, infectious, neoplastic, or traumatic causes of cervical pathology.

The degenerative neck pain group comprised patients with radiologically confirmed structural pathology, including cervical disc herniation, identified on magnetic resonance imaging (MRI) as a posterior disc protrusion or extrusion (n=18), and cervical spinal stenosis, confirmed by MRI or plain radiography and characterized by decreased spinal canal dimensions (n=2).

Participants in the healthy control group were asymptomatic and had no history of neck pain or spinal disorders; they were selected from among individuals who underwent routine health screening, including lateral cervical radiography, during the study period. Radiographic images were reviewed to confirm the absence of structural abnormalities in the cervical spine. The exclusion criteria were as follows: (1) history of cervical spine surgery or traumatic injury; (2) congenital or systemic musculoskeletal or neurological disorders (eg, rheumatoid arthritis, ankylosing spondylitis, and peripheral neuropathy); (3) presence of tumors, infections, or inflammatory disease affecting the cervical spine; (4) poor-quality radiographs preventing accurate measurement; and (5) refusal or inability to provide informed consent.

RADIOGRAPHIC DATA COLLECTION:

Lateral cervical radiographs (SIG-40-525; Ecoray Inc., Seoul, Republic of Korea) were obtained for clinical purposes using a digital radiography system under standardized exposure conditions (70–80 kVp, 20–25 mAs, and a focus-to-film distance of approximately 180 cm). All images were captured with the participants standing, arms relaxed at their sides, and feet together to minimize postural variation. Participants were instructed to maintain a neutral head position with a horizontal gaze during imaging [15]. The imaging field extended from the nasion–sella line to the 7th cervical vertebra (C7), including the vertebral bodies, spinous processes, and intervertebral disc spaces [16]. Participants removed any accessories that could interfere with image quality. All radiographs were reviewed for adequate visualization of bony landmarks, and suboptimal images were repeated.

RADIOGRAPHIC MEASUREMENTS:

Cervical sagittal alignment was assessed using lateral cervical radiographs, focusing on 3 parameters: SVA, SCA, and intervertebral disc height. The SVA was measured as the horizontal distance between a vertical line from the centroid of C2 and the posterosuperior corner of C7, representing anterior–posterior translation. The SCA was measured as the angle between a line connecting the center of the sella turcica to C7 and a line along the posterior border of the cervical vertebral bodies, reflecting global sagittal curvature relative to the cranial base [16–18]. The intervertebral disc height was calculated as the average of the anterior and posterior disc heights at each cervical level from C2–C3 through C6–C7, with measurements conducted at the midpoint of each vertebral segment [19].

Standardized anatomical landmarks were predefined before measurement to ensure consistency across all radiographs. All measurements were performed using a picture archiving and communication system (PACS; ViewRex 3.0, Techheim, Seoul, Korea) (Figure 2). Each parameter was measured 3 times by a blinded examiner with over 5 years of experience, and the mean values were used for analysis. Intraobserver reliability was excellent, with intraclass correlation coefficients ranging from 0.996 to 0.999 for SVA, 0.908 to 0.967 for SCA, and 0.981 to 0.995 for disc height.

STATISTICAL ANALYSIS:

All analyses were performed using SPSS software (version 18.0; SPSS Inc., Chicago, IL, USA). Normality and homogeneity of variance were assessed using the Shapiro–Wilk and Levene’s tests, respectively. Differences in cervical sagittal parameters (SVA, SCA, and intervertebral disc height) among the 3 groups were analyzed using one-way ANOVA. When significant, post hoc comparisons were performed using the Bonferroni correction. Continuous variables are presented as mean±standard deviation, and 95% confidence intervals (CIs) were calculated. A P value <0.05 was considered statistically significant.

Results

PARTICIPANTS CHARACTERISTICS:

Seventy participants were included in the analysis: 25 with nonspecific neck pain, 20 with degenerative neck pain, and 25 asymptomatic healthy controls. Mean age, height, and weight did not differ significantly among the 3 groups (P>0.05, Table 1). Female participants accounted for 65% (13), 60% (15), and 56% (14) of patients in the degenerative neck pain, nonspecific neck pain, and asymptomatic healthy control groups, respectively.

CERVICAL SAGITTAL ALIGNMENT:

Cervical sagittal alignment significantly differed between the 3 groups in terms of both SVA and SCA (SVA: F=5.988, P=0.004; SCA: F=5.010, P=0.009; Table 2). Post hoc analysis with Bonferroni correction revealed that the nonspecific neck pain group exhibited a significantly higher C2–C7 SVA than both the degenerative neck pain (P=0.004) and healthy control (P<0.05) groups, indicating greater anterior translation of the cervical spine. Additionally, the SCA was significantly smaller in the degenerative neck pain group than in the nonspecific neck pain group (P=0.014), suggesting reduced overall cervical lordosis relative to the cranial base. The nonspecific neck pain group also demonstrated a significantly larger SCA than the healthy control group (P=0.041). In contrast, no statistically significant differences were observed between the degenerative neck pain and control groups for either parameter (Figure 3).

INTERVERTEBRAL DISC HEIGHT:

No significant differences in cervical intervertebral disc height were observed among the degenerative neck pain, nonspecific neck pain, and control groups (P>0.05, Table 3).

Discussion

LIMITATIONS:

This study has certain limitations. First, owing to its cross-sectional design, a causal inference cannot be established between sagittal alignment and neck pain. Therefore, longitudinal studies are required to establish temporal relationships. Second, as radiographic assessment was limited to a static standing posture, it may not reflect dynamic motion or functional loading conditions. Third, measurements were based on two-dimensional lateral images, which do not capture three-dimensional alignment or rotational components. Fourth, only SVA and SCA were used as global alignment parameters, and other factors, such as segmental alignment and neuromuscular function, were not assessed. Fifth, potential confounders, including body mass index, occupational posture, screen time, and daily postural habits, could not be controlled, owing to the retrospective design of the study; these factors may have influenced alignment and symptoms. Finally, the degenerative neck pain group was heterogeneous, with most patients presenting with disc herniation and only few with spinal stenosis, which limits subgroup analysis and generalizability. Future studies should incorporate longitudinal designs with dynamic and three-dimensional assessments while accounting for potential confounders.

Conclusions

The present study demonstrates distinct cervical sagittal alignment patterns in nonspecific neck pain compared to degenerative neck pain and healthy controls. Patients with nonspecific neck pain had increased anterior translation and altered global cervical lordosis, whereas intervertebral disc height did not differ among groups. These findings suggest that structural disc morphology is less relevant than global alignment patterns in nonspecific neck pain. Our results indicate that nonspecific neck pain is associated with global sagittal alignment changes rather than segmental abnormalities, demonstrating that clinical assessment and management strategies should focus on overall cervical alignment rather than isolated segmental features.