Neurospine Search


Lee, Hyun, and Jain: Cervical Sagittal Alignment: Literature Review and Future Directions


Cervical alignment as a concept has come to the forefront for spine deformity research in the last decade. Studies on cervical sagittal alignment started from normative data, and expanded into correlation with global sagittal balance, prognosis of various conditions, outcomes of surgery, definition and classification of cervical deformity, and prediction of targets for ideal cervical reconstruction. Despite the recent robust research efforts, the definition of normal cervical sagittal alignment and cervical spine deformity continues to elude us. Further, many studies continue to view cervical alignment as a continuation of thoracolumbar deformity and do not take into account biomechanical features unique to the cervical spine that may influence cervical alignment, such as the importance of musculature connecting cranium-cervical-thoracic spine and upper extremities. In this article, we aim to summarize the relevant literature on cervical sagittal alignment, discuss key results, and list potential future direction for research using the ‘5W1H’ framework; “WHO” are related?, “WHY” important?, “WHAT” to evaluate and “WHAT” is normal?, “HOW” to evaluate?, “WHEN” to apply sagittal balance?, and “WHERE” to go in the future?


The concept of cervical spinal alignment has gained interest in the field of spinal deformity research over the last decade. However, the number of studies on normative data remain limited [1-5]. Initial studies focused on the correlations between sagittal alignment and outcomes of surgical treatment of cervical myelopathy [6,7]. Changes of sagittal balance following laminoplasty and cervical disc arthroplasty (CDA) were also topics of interest in this period [8-11]. The concept of sagittal spinal alignment had been studied extensively in the thoracolumbar spine since the 2000s, and eventually these concepts were extended to the cervical spine in the 2010s.
The number of studies on cervical sagittal alignment have increased dramatically over the last several years (Fig. 1). Broad areas of research focus in this space have been: (1) correlation of cervical alignment with thoracolumbar spine following surgical treatment; (2) novel measurement parameters correlating cervical spine and thoracolumbar-pelvic alignment including ‘T1 sagittal angle’ (2010, identical to T1 slope) [12], thoracic inlet alignment (2012) [13]; and (3) correlation of health-related quality of life (HRQoL) and cervical radiographic alignment parameters such as cervical sagittal vertical axis (SVA, 2012) [14].
Despite the robust research efforts, the definition of normal cervical sagittal alignment continues to elude us. Further, many studies continue to view cervical alignment as a continuation of thoracolumbar deformity, and do not take into account biomechanical features unique to the cervical spine that may influence cervical alignment, such as the importance of musculature connecting cranium-cervical-thoracic spine and upper extremities. In this article, we aim to summarize the relevant literature on cervical sagittal alignment, discuss key results, and list potential future direction for research using the ‘5W1H’ framework.


1. Degenerative Cervical Spine; Laminoplasty, Disc Arthroplasty, Cervical Fusion, Adjacent Segment Pathology

Correlation between cervical sagittal alignment and the outcomes of cervical myelopathy following laminoplasty has been an important topic in the cervical literature. Because the decompression effect of laminoplasty mainly depends on the posterior spinal cord drift, the cervical sagittal alignment has been shown to correlate with outcomes. Since Suda et al. [6] reported correlation between cervical kyphosis and less favorable neurological recovery in 2003, many articles have reiterated the conclusion [7,15-17]. Kyphosis more than 10°–13° was demonstrated to be an important cutoff for cervical laminoplasty. In addition, investigators focused on alignment changes of the cervical spine following laminoplasty [10,15,18]. Many studies concluded that anterior cervical decompression and fusion with lordosis reconstruction was a more appropriate option for kyphotic cervical spine instead of posterior surgery [19-24].
With popularity of CDA, there was an increased interest in studying adjacent segment pathology (ASP) comparing CDA versus anterior cervical discectomy and fusion (ACDF) starting the 2000s. Pickett et al. [8] and Johnson et al. [9] reported preserved global cervical sagittal balance after Bryan prosthesis even with mild kyphotic changes of the CDA segments in 2004, and several studies have presented similar results [11,25,26].
Since then, multiple studies have since reported that the sagittal malalignment might influence development of ASP. In 2011, Faldini et al. [27] presented mean 16-year follow-up results of 107 patients and concluded that proper lordotic alignment of cervical spine is significant to decrease the risk of adjacent segment degeneration. In a systematic review by Hansen et al. [28] in 2012, they found increased risks of ASP associated with malalignment with low-grade evidence. But recently, Snowden et al. [29] reported that the preoperative and postoperative sagittal alignment do not affect on radiographic ASP at following of CDA and ACDF at least 7 years prospectively. Although the evidence is low and the etiology of ASP is multifactorial, it is generally accepted that the malalignment may contribute to development of ASP [30].

2. Thoracolumbar Deformities: AIS, SD, ASD

Since the late 1990s, cervical kyphosis in adolescent idiopathic scoliosis (AIS) is relatively well-known phenomenon with incidence of 36%–40% and thought to be a reactive change to the hypokyphosis of thoracic spine [31]. The spontaneous correction of cervical kyphosis following instrumented fusion of the thoracolumbar deformity has been reported by numerous authors in 2010s [32-37], which is mainly contributed from the restoration of the thoracic kyphosis (TK) and reciprocal changes between the cervical and thoracic segments. In contrast, radiographic analyses of Scheuermann disease (SD) showed hyperlordosis of cervical spine in the literature with similar compensatory mechanism for the hyperkyphosis of the thoracic spine [38,39].
In adult spinal deformity (ASD), extensive research on the global spinal alignment has been performed since the 2000s and 2010s but most research did not include cervical spine. The studies have elucidated lumbopelvic balance, represented by the formula, PI (pelvic incidence)= SS (sacral slope)+PT (pelvic tilt), and spinopelvic compensation mechanism including pelvic retroversion, hip extension, and knee flexion. Although several authors have commented the cervical lordosis (CL) increases per the increased kyphosis, not many studies had not extended interest in the cervical spine. Berthonnaud et al. [40] included the statistical correlation between CL and TK in their analysis of the spinopelvic balance in 2005. Followed studies on this topic mirrored similar correlation between cervical and thoracolumbar alignment [41,42].
Spontaneous improvement of cervical alignment after correction of global sagittal balance following thoracolumbar osteotomy was published by Smith et al. [43] in 2012. Since then numerous articles have presented the reactive changes of cervical spine including CL and cervical spine SVA [44-46]. In 2014, Smith et al. [47] also reported prevalence of cervical deformity (defined as cervical kyphosis > 0° or C2–7 SVA > 4 cm) by 53% in 470 thoracolumbar ASD patients’ database.
Compensatory correction of the thoracolumbar alignment after the correction of the cervical deformity has been reported by Lee et al. [48] in 2016, Mizutani et al. in 2018 [49] and 2019 [50]. Those studies have indicated that the cervical alignment or deformity has significant correlation with thoracolumbar alignment and their changes.


1. Correlation With Disc Degeneration, Neck Pain, Clinical Outcomes Following Surgery

The clinical implications of sagittal alignment of the cervical spine remain controversial. Okada et al. [51] in 2009. They followed 487 asymptomatic volunteers with magnetic resonance imaging (MRI) at an average of 11.3 years and found no significant correlation between the sagittal alignment of the cervical spine and clinical symptoms. But several articles have been published the effect of sagittal alignment on the clinical symptoms. Lee et al. [52] (2014) reported increased thoracic inlet inclination is a predictor of chronic neck pain. Yang et al. [53] (2015) reported increase T1 slope is related to cervical disc degeneration. Iyer et al. [54] reported low T1 slope (T1S)-CL and high C2–7 SVA area independent predictors of high preoperative Neck Disability Index (NDI).
Previously, Chin-Brow Vertical angle (CBVA) has been presented as an important parameter of the functional outcomes following corrective osteotomy for ankylosing spondylitis patients [55]. Lafage et al. [56] (2016) found that CBVA of < -4.8° or > 17.7° correlated with an Oswestry Disability Index of 40. The first statistical analysis on the clinical correlation with cervical sagittal parameter was presented by Villavicencio et al. [57] in 2011, which demonstrated increased segmental lordosis was related to higher degree of improvement in clinical outcomes in 122 anterior cervical fusion patients with mean 37.5-month followup. In 2102, Tang et al. [14] presented standing cervical SVA including C2–7 SVA SVA C7orrelated with HRQoL parameters in the cohort underwent posterior cervical fusion. Protopsaltis et al. [58] (2015) reported changes in CL correlated to HRQoL improvement in thoracolumbar ASD. Hyun et al. [59] (2017) presented T1S–CL > 22.2° and C2–7 SVA > 43.5 mm correlated with NDI in their posterior cervical fusion patients. Since then, many studies have presented clinical correlation with cervical SVA and T1S–CL.
However, there have been conflicting articles on their conclusions. Vavruch et al. [60] (2002) reported the reconstruction of disc height and lordosis were not related clinical outcomes after ACDF. Lee et al. [61] (2016) reported no significant difference of HRQoL or number of fusion levels in patients had solid anterior cervical fusion without correlation with SVA or CL. Bao et al. [62] (2017) and Lau et al. [63] (2020) have also failed to identify significant association between CL and HRQoL outcomes in their cervical fusion cohort. This implies there could be a range of alignment providing forgiveness without affecting the HRQoL.


1. Conventional Parameters: Angular and Translational

The first searchable study on cervical spine alignment published by Borden et al. [1] in 1960. They measured the maximum horizontal distance from the line connecting the posterior part of the dens and posteroinferior corner of C7 and the mean value was 12 mm in random chest lateral radiographs of 180 patients.
The conventional evaluation of cervical alignment can be categorized into 2 categories. The first one is angle measurement. Although there have been several methods have been presented to measure CL, including Gore method [2], tangential method [64] etc., Cobb method is the mainstay since their publication in 1948, measuring angles between the upper endplate of the uppermost segment and the lower endplate of the lowest segment because of the simplicity and high reliability [65,66]. Most researchers divide CL into C0 (occiput)–C2 lordosis and C2–7 lordosis to evaluate the upper cervical and subaxial cervical spine alignment.
Another conventional parameter is SVA. A distance from the C7 plumb line and the posterosuperior corner of S1 considered as C7 SVA in thoracolumbar spine alignment. Cervical SVA was reported by Kuntz et al. [5] for the first time in their study on the normative measurement study. A C2–7 SVA or center of gravity (COG)–C2 or C7 SVA are using the same plumb line method to evaluate the translation of cervical spine. The CBVA, which is measured by an angle between a line drawn from chin to brow and vertical angle, is the first parameter to assess horizontal gaze [55]. Initially it was mainly applied to ankylosed spine but now getting more interest to evaluate the HRQoL related to horizontal gaze in patients with extensive cervicothoracic or thoracolumbar fusion [42,56,67,68].

2. Innovative Parameters, Since the Concept of ‘T1 Slope’

In 2010, Knott et al. [12] presented the use of ‘T1 sagittal angle’ (identical to current T1S) as an important parameter to predict overall sagittal balance of the spine from cervical spine to lumbopelvic alignment. The concept of T1S started to bring additional interest in the cervical spine alignment. Lee et al. [13] (2012), published an innovative thoracic inlet alignment measurement including thoracic inlet angle (TIA), neck tilt (NT), T1S, cranial tilt (CT), and cervical tilt, etc. (Fig. 2). The term T1S was firstly introduced in this article. The concept was based on the idea that the sagittal balance of the cranium and cervical spine could be influenced by the shape and orientation of immobile thoracic inlet to get a balanced upright posture and horizontal gaze like the PI in the pelvis.
Since then, the concept of T1S widely expanded the variable innovative measurements of cervical spine as well as thoracolumbar spine, pelvis, and lower limb alignment (Table 1, Fig. 3). Studies on numerous innovative parameters have followed with radiographic correlation with the traditional measurement parameters such as TK, lumbar lordosis (LL), PI, SS, etc.
Ames et al. [67] (2015) introduced the parameter T1S–CL in their cervical deformity classification system like PI–LL mismatch in thoracolumbar deformity. Le Huec et al. [69] (2015) proposed a concept of cranial incidence (CI), cranial slope (CS), and CT, with a formula CI=CT+CS, to analyze the anatomical characteristics of crainocervical alignment. They used C7 slope instead of T1S and used spino-cranial angle (SCA) to evaluate the craniocervical alignment. Protopsaltis et al. [70,71] (2017) measured several novel angles including craniocervical angle, C2 pelvic angle, cervicothoracic pelvic angle to evaluate cervical alignment including whole spine sagittal alignment. Yoon et al. [72] (2017) reported occipitocervical inclination. Hashimoto et al. [73] (2018) used a clivoaxial angle to evaluate Dropped head syndrome. Kim et al. [74] (2018) presented K-line tilt as a correlating parameter with C2–7 SVA and T1S–CL. Most recently the measurement extended to upper cervical spine. Protopsaltis et al. [75] (2019) reported C2 slope as another parameter correlates with outcomes and Choi et al. [76] (2019) proposed C2 incidence angle to evaluate the cervical alignment (Fig. 4). Despite of the multiple radiographic parameters that have been described, only T1S and T1S–CL have been shown to correlate with clinical outcomes.

3. Normal Alignment and Compensation; Intra- and Extracervical Spine (Table 2)

There is still no consensus definition of ‘normal’ cervical alignment. Although lordosis is accepted as major presentation of natural cervical alignment, it is well known that significant number of asymptomatic cervical spine is not lordotic. Hardacker et al. [3] (1977) already reported kyphotic cervical alignment of 5° or greater in 36% of asymptomatic volunteers in their study. Kim et al. [77] (2018) reported a 26.3% incidence of kyphotic cervical alignment in asymptomatic cohort and Khalil et al. [42] (2018) reported 32% of kyphosis and 41% of lordosis. Overall, the incidence of asymptomatic kyphosis is approximately 30%.
Hardacker et al. [3] (1997) reported normal O–C7 angle as 40°±9.7° lordosis. In their results, most lordosis occurred at the C1–2 angle and the lower cervical spine C4–7 contributed only 15%. Gore et al. [2] (1986) presented mean C2–7 angle as variable as -15°±10° to -27°±14° according to the age group and gender. Since then many normative studies have presented CL in asymptomatic cohort. O–C2 angle ranged from -12.3° to -32.5° and C2–7 angle ranged from -4.1° to -16.3°. Overall, reported total CL (C0–7) was approximately 30° [5,78,79].
Compensation mechanism within and outside of cervical spine is a well-established phenomenon and has been supported by many studies. Kyphosis of a single or multiple segments can be compensated by the upper or lower adjacent segments, and a kyphotic alignment changes in subaxial cervical spine can be compensated by the hyperlordotic upper cervical spine (C0–2) and vice versa [71,80-82]. Kyphotic changes of cervical spine decrease TK to compensation the alignment and keep the ‘cone of economy’ of global spinal balance. Likewise, increased TK causes hyperlordotic cervical alignment and vice versa. An interesting point is that there is no direct correlation between LL and CL in studies on cervical alignment including thoracolumbar spine and pelvic alignment [47,52]. The LL influences TK and has only indirect effect on the cervical alignment [40,41]. Another compensation mechanism between the T1S and CL has presented by Lee et al. [13] (2012). They presented the concept of thoracic inlet alignment and concluded large TIA increased T1 slope and CL and vice versa to preserve neck tile around 44° and horizontal gaze.
Few studies have presented normative cervical SVA, T1 slope, TIA, and NT values. Lee et al. (2012) [13] reported COG–C7 SVA as 20.7±11.7 mm, T1S 25.7°±6.4°, TIA 69.5°, and NT 43.7° in asymptomatic cohort. Hey et al. [83] (2017) reported C2–7 SVA as 8.8±24.2 mm, T1S as 17.4°±8.7°, and Khalil et al. [42] (2018) reported the range from 21–22 mm of COG–C7 SVA, 19°–32° of T1S, TIA 66°–73° and NT 41°–47°. In summary, C2–7 SVA and T1S are reported approximately 20 mm and 25° respectively. Reported TIA and NT values are around 70° and 45° in the literature [42,83-86].
Aging and sex also influence cervical alignment. In many reports, aged population showed increases cervical SVA, CL, and T1S which is mainly contributed from increased TK [4,87-95]. Chen et al. [96] (2017) and Liu et al. [97] (2019) presented increasing TIA and NT with aging process as well as CL and T1S.


1. Conventional Radiographs and Positional Variations

Simple radiographs are the most important tool to evaluate the alignment of spine. However, still there is no established radiographic guideline to evaluate cervical spine sagittal balance. It is well known that position changes in the arm cause significant variation in standing whole spine lateral radiograph [98]. Likewise, many factors influencing on the measurement results in cervical spine lateral radiographs have been reported.
To keep the horizontal gaze, Lee et al. [13] (2012) evaluated cervical spine lateral radiograph in standing position with horizontal Frankfart plane (an extended line connecting the lower border of the orbit and the external auditory meatus) and they evaluated the thoracolumbar alignment with separate standing whole spine lateral radiographs. Park et al. [99] (2015) reported significant decrease T1S and CL in the standing whole spine lateral radiographs with fist on clavicle position, caused by posterior cranial shift in 101 asymptomatic volunteers. Kusakabe et al. [100] (2019) reported 28.7% showed decreased CL and 29.6% showed increased CL in the sitting position compared the standing position with whole spine lateral radiograph. Based on results of the literature, evaluation of cervical spine alignment by either standing whole spine radiographs or sitting cervical spine lateral radiographs will be less reliable [101,102].
Another huddle to accurate measurement of cervical spine radiograph is unclearly visible lower cervical and upper thoracic spine endplate in patients with short neck or high shoulder contour. Measuring C7 instead of T1 has been recommended by several authors because C7 is clearly visible than T1 in more patients, C2–6 Cobb angle and C7 slope are correlated well with C2–7 angle and T1 slope [69,103-106].

2. Newer Measurement Methods: EOS, CT, MRI

Several innovative imaging techniques have been proposed. Singhatandgige et al. [84] (2015) reported reliable results measured by EOS lateral whole-body stereo-radiograph compared to conventional cervical lateral radiograph. Studies presenting measurement of cervicothoracic junction including thoracic inlet alignment using computed tomography or MRI have been published [86,107-110]. The CT or MRI can visualize C7 lower endplate, T1 upper endplate, the end of manubrium well in the midsagittal images better than conventional radiographs [111]. The supine position in axial imaging may potentially skew the weight-bearing neutral position of the cervical spine. Additional considerations are cost and radiation exposure with CT.


1. Definition of Cervical Deformity

As there is no consensus on “normal” cervical alignment, the precise definition of cervical deformity is a moving target. Smith et al. [47] (2014) initially defined cervical deformity as C2–7 angle > 0° and C2–7 SVA > 4 cm in their thoracolumbar deformity cohort. But later the same study group proposed C2–7 kyphosis > 10° and C2–7 SVA > 4 cm based on the correlation with HRQoL [67]. Passias et al. [112,113] (2018) expanded the definition of cervical deformity as cervical kyphosis: C2–7 Cobb angle > 10°, cervical scoliosis: coronal Cobb angle > 10°, positive cervical sagittal imbalance: C2–C7 SVA> 4 cm or T1S–CL > 10°, or horizontal gaze impairment: chin-brow vertical angle> 25°.

2. Location of the Deformity

Location of the deformity is an important factor to consider for planning surgical correction. Passias et al. [112] (2018) classified the ‘primary driver’ of the cervical deformity as cervical when the lower instrumented vertebra is higher than C7 and cervicothoracic when LIV is T3 or higher. Lee et al. [114] (2018) proposed C5–T3 angle as the cervicothoracic junction based on the significant correlation between the major radiographic parameters including CL, TK, and clinical outcome parameters.
Lee et al. [115] (2019) proposed a surgical treatment strategy based on T1S and cervicothoracic junction angle (Fig. 5). When T1S is normal and cervicothoracic junction is normal, the deformity is located with the cervical spine so need anteriorposterior surgery. The correction should be on the lower cervical spine including pedicle subtraction osteotomy when T1S is normal and cervicothoracic junction angle is kyphotic. A high T1S and kyphotic cervicothoracic junction angle mean the deformity is on the upper thoracic spine and a high T1S and normal cervicothoracic junction implies the correction should be performed on the mid or lower thoracic spine.

3. Cervical Deformity Classifications Presented and Lessons From Dropped Head Syndrome

To date, several classification systems have been proposed. Lamartina and Berjano [116] (2014) presented spinal sagittal plane deformity classified by the location of the regional deformity and compensation mechanism, however, they did not focus on cervical spine in detail.
Ames et al. [67] (2015) proposed a comprehensive cervical spine deformity classification system based on a modified Delphi approach. The classification system included a deformity descriptor and 5 modifiers that incorporated sagittal, regional, and global spinopelvic alignment and neurological status. The descriptors included: ‘C,’ ‘CT,’ and ‘T’ for primary cervical kyphotic deformities with an apex in the cervical spine, cervicothoracic junction, or thoracic spine, respectively; ‘S’ for primary coronal deformity with a coronal Cobb angle > 15°; and ‘CVJ’ for primary craniovertebral junction deformity. The modifiers included C2–7 SVA, horizontal gaze (CBVA), T1S-CL, myelopathy by modified Japanese Orthopedic Association score, and the Scoliosis Research Society-Schwab classification for thoracolumbar deformity. This system covers wide spectrum of thoracolumbar deformity, neurological status as well as the cervical spine deformity in both coronal and sagittal plane.
Koller et al. [117] (2019) published Cervical Spine Research Society-European classification of cervical deformity. It provided 4 types, A to D, based on global trunk balance/imbalance and cervical (cervicothoracic) kyphosis/lordosis. Virk et al. [118] (2020) have presented a classification for severe cervical deformity. They grouped the patients into 3 sagittal morphotypes: focal deformity, flat neck (large TS–CL and lack of compensation), or cervicothoracic.
Given that most cervical deformity is in the sagittal plane, several classifications have focused on the kyphosis and compensation mechanism from the trunk. The compensation of cervical kyphosis by thoracolumbar spine has been studied for ‘Dropped head syndrome.’ Dropped head syndrome is defined as a severe cervical kyphosis or chin-on-chest deformity in the standing or sitting position causing significant cervical sagittal imbalance. The causes are still unclear but thought to be posterior neck muscle weakness, also known as an isolated neck extensor myopathy. Association with other neuromuscular disease has been reported including amyotrophic lateral sclerosis, polymyositis, mitochondrial myopathy, Lewy body dementia, etc. Because of the disabling nature of deformity, corrective surgery is required in selected cases [70,119,120].
Hashimoto et al. [73] (2018) classified the Dropped head syndrome as SVA+ and SVA– types based on their SVA with similar degree of cervical kyphosis angles. SVA– type includes patients whose cervical kyphosis was compensated by decreased TK and increased LL. SVA+ type means absent compensation mechanism in the thoracolumbar spine. They indicated osteoporotic compression fracture, and/or diffuse idiopathic skeletal hyperostosis at the thoracic region and loss of lumbar lordosis due to lumbar spinal stenosis and degenerative lumbar diseases at the lumbar region. Mizutani et al. [49] (2018) presented a cervical kyphosis classification as ‘head-balanced’ and ‘trunk-balanced’ type in cervical deformity patient cohort. The head-balanced type is defined as the head COG plumb line is balanced on the pelvis and the C7 plumb line is shifted posteriorly to compensate cervical kyphosis by thoracolumbar spine. A trunk-balanced type shows the C7 plumb line is balance on the pelvis and the head COG plumb line is anterior to the C7 plumb line because of the compensation failure by the thoracolumbar spine. Endo et al. [119] (2019) also presented similar classification in Dropped head syndrome patients: positive balanced type (C7 SVA ≥ 0 mm) and negative balanced type (C7 SVA < 0 mm).
The studies of Dropped head syndrome studies explain that the cervical kyphosis compensated by thoracolumbar spine shows decreased TK, T1S and increased LL. But the cervical kyphosis without thoracolumbar compensation shows increased TK, T1S and decreased LL. We could extrapolate that compensation by thoracolumbar spine should be one of the important factors to consider for surgical correction of cervical kyphosis based on the studies of Dropped head syndrome.


1. Thoracic Inlet Alignment Studies and Revisiting the Concept of ‘Neck Tilt’

The studies on cervical alignment based on T1S and thoracolumbar alignment have provided significant advancement in our understanding of cervical alignment. Many studies in the literature lack the possible influence of weight and musculature connecting cervical spine, thoracic cage, and upper extremities.
Lee et al. [13] (2012) introduced the concept of TIA=T1S+NT, similar to the PI= SS+PT in the thoracolumbar spine, based on the postulation that there could be a separate balancing mechanism of the cranium and cervical spine influenced by the shape and orientation of thoracic inlet. Because there is no range of motion in thoracic inlet, TIA could provide an anatomical base for the craniocervical alignment in normal asymptomatic cohort. They indicated large TIA increases T1S to preserve NT around 44° in the conclusions. Since then, several studies using radiograph, computed tomography, and MRI have reiterated the conclusion of the article by normative data.
In a study of Scheuermann Disease, Janusz et al. [38] (2015) reported TIA and T1S decreased after correction of TK but NT did not change significantly. Pan et al. [121] (2017) reported similar changes of thoracic inlet alignment after the correction of posttuberculosis cervical kyphosis. Wang et al. [122] (2018) presented higher T1S and TIA in cervical spondylolisthesis group than nonspondylolisthesis group but the NT was unchanged. Song et al. [123] (2020) reported stable NT values and TIA after correction of kyphotic deformities in patients with Hirayama disease. In the results of those studies, T1S increased and TIA decreased according to the correction of cervico TK, but NT remained stable. There results lend support to the hypothesis that TIA compensates to alignment changes of the cerviothoracic junction, and NT remains stable to preserve physiologic cranial and cervical spine balance. The result is minimization of energy expenditure of head and neck muscles akin to the ‘Cone of Economy’ concept in the erect spine.

2. Preliminary NT Measurement Data

To prove the hypothesis of ‘stable NT,’ we measured thoracic inlet alignment (TIA, SS, NT) as well as major radiographic parameters (CL, TK, LL, PI, SS) in 23 patients who underwent primary cervical spine deformity surgery. The groups were divided into head-balanced and trunk-balanced patients. There was a significant difference in the 2 groups in the T1S (0.9° vs. 46.3°, p< 0.01) and TIA (47.5° vs. 90.2°, p< 0.01) but no significant difference in the NT (46.5° vs. 44°). After the corrective surgery, the head-balanced group showed significantly increased T1 slope and TIA, while the trunk-balanced group showed decreased T1S and TIA (Table 3, Figs. 6, 7).
Based on these results, several observations can be made: (1) Cervical deformity compensated by the thoracolumbar spine shows decreased T1S and TIA (Fig. 6). (2) Cervical deformity or cervicothoracic deformity without thoracolumbar compensation shows increased T1S and TIA (Fig. 7). (3) Correction of cervical/cervicothoracic deformity normalizes T1S and TIA. (4) NT is unchanged despite surgical intervention (Fig. 8).

3. Prediction of the Ideal Cervical Alignment

Providing optimal alignment targets for surgical reconstruction of an imbalanced cervical spine is another important target of investigation. In general, it is widely accepted that high T1S, increased CK, high cervical SVA requires more CL to get a horizontal gaze.
Diebo et al. [68] (2016) proposed the alignment target of CL as CL= 10–(LL–TK)/2, to achieve ideal CL based on the thoracolumbar alignment. Ajello et al. [124] (2017) presented a result that a C2–C7 SVA < 25 mm and a CL/C7 slope greater than 0.7 had better clinical outcomes than the group less than 0.7. Staub et al. [125] (2019) presented another formula for normative CL= T1S–16.5°±2° in cervical deformity patients’ cohort using correlations between radiographic parameters. Goldschmidt et al. [126] (2020) used more complicated trigonometric methods and reported a novel δ angle subtended by the cervical height also (δ= T1S°CL/2) and 2 complicated formulas to calculate ideal cervical SVA including “SVA= CH× tan (π/180× (T1S−CL)/2)” and “(1.1× T 1)−(0.43× CL)+6.69”. Zhu et al. [127] (2020) included the thoracic inlet alignment and estimated physiologic CL as a formulas: CL= 0.762× T1S−0.392× C2–C7 SVA+0.25× TIA−13.795 (stepwise multiple regression) and CL = 0.417 × TIA−11.193 (simple linear regression), and they proved their formulas showed good correlation with postoperative alignment.
Despite of these efforts, ideal cervical alignment targets continue to elude us. Some proposed formulas are too complex to predict and not easy to utilize them in the clinical settings. Further, some do not consider thoracolumbar compensation mechanism following cervical deformity correction. Planning of correction without considering the compensation mechanism may result in over- or under-correction. Thus, establishing alignment targets for cervical correction that take TL compensation into account in a fruitful area for future research.


Cervical alignment as a concept has come to the forefront for spine deformity research in the last decade. Studies on cervical sagittal alignment started from normative data and expanded into correlation with global sagittal balance, prognosis of various conditions, outcomes of surgery, definition and classification of cervical deformity, and prediction of targets for ideal cervical reconstruction.
A variety of radiographic parameters have been proposed for evaluation of cervical alignment. However, identifying parameters that correlate with important clinical outcomes remains an area of investigation.
Further, radiographic evaluation method for cervical spine alignment assessment has not been standardized, including position of arms, direction of gaze, etc. Uniform methods of radiographic evaluation would potentially minimize the variability in research results.
Most studies focusing on cervical alignment are based on the concept that the cervical spine is just overlying spinal segment on top of the thoracolumbar spine. These studies do not account for the possible biomechanical influence of the musculature connecting cranium-cervical-thoracic spine and upper extremities. A future classification of cervical deformity needs to include compensation mechanism by the thoracolumbar spine as well as the cervical spine itself, in order to provide the appropriate surgical strategy for reconstruction of the ideal cervical spine alignment.


The authors have nothing to disclose.

Fig. 1.
Number of articles searched by “cervical spine” AND “sagittal alignment” at
Fig. 2.
Schematic drawings of the conventional cervical alignment parameters including thoracic inlet alignment. SVA, sagittal vertical axis.
Fig. 3.
Schematic drawings of the innovative cervical angles reported.
Fig. 4.
Schematic drawings of the innovative measurement of cervical spine involving thoracolumbar spine and pelvis.
Fig. 5.
Surgical planning of fixed cervicothoracic deformities based on location of deformity using the T1 slope and the cervicothoracic junctional (C5–T3) angle. CTJ, cervicothroacic junction; PSO, pedicle subtraction osteotomy; VCR, vertebral column resection.
Fig. 6.
A cervical deformity patient showing head-balanced kyphosis. The preoperative radiographs show low TIA and low T1S to compensate the cervical kyphosis. The SVAs (blue: SVA COG, yellow: SVA C2, red: SVA C7) show a head-balanced over the pelvis alignment. Also, preoperatively hypokyphosis was noted to compensate the cervical kyphosis and preserve global spinal balance. Postoperative radiographs show reversed SVAs, increased thoracic kyphosis as well as increased T1S and TIA. However, the NT remains stable. T1S, T1 slope; TIA, thoracic inlet angle; SVA, sagittal vertical axis; NT, neck tilt; TK, thoracic kyphosis; LL, lumbar lordosis; PI, pelvic Incidence; KA, knee angle; AA, ankle angle.
Fig. 7.
A cervical deformity patient showing trunk-balanced kyphosis. The preoperative radiographs show high TIA and high T1S but the thoracic spins is not compensating cervical kyphosis. The SVAs (Blue: SVA COG, Yellow: SVA C2, Red: SVA C7) show a trunk-balanced over the pelvis alignment. The preoperatively hyperkyphosis means that the deformity is contributed from both cervical and the upper thoracic spine. Postoperative radiographs show corrected cervical kyphosis, SVAs, decreased kyphosis as well as decreased T1S and TIA. In this type of cervical deformity, the NT remains stable. T1S, T1 slope; TIA, thoracic inlet angle; SVA, sagittal vertical axis; NT, neck tilt; TK, thoracic kyphosis; LL, lumbar lordosis; PI, pelvic Incidence; KA, knee angle; AA, ankle angle.
Fig. 8.
Clinical presentation of cervical kyphosis based on the compensation mechanism by the thoracolumbar spine and location of the major deformities. Neck tilt is remaining stable and providing a stable compensation zone like ‘cone of economy’ for the cervical spine. T1S, T1 slope; TIA, thoracic inlet angle; NT, neck tilt; TK, thoracic kyphosis; LL, lumbar lordosis.
Table 1.
Innovative cervical spine measurement angles in the literature; sorted by the published year order
Parameter Measurement methods Study
T1 sagittal angle The angle between a horizontal line and the T1UEP Knott et al. (2010) [12]
Dens angle The angle of the dens in the sagittal plane
Dens-Occiput angle The angle of the dens in relation to the occiput
Cervical tilt The angle formed between the vertical line from the center of T1UEP and the line from the center of T1UEP to the tip of the dens. Lee et al. (2012) [13]
Cranial tilt The angle formed between the line from the center of the T1UEP to the dens and the SVA from the T1UEP.
Neck tilt The angle formed by a line drawn in the upper end of the sternum and a line connect- ing the center of the T1UEP
T1 slope The angle formed between the horizontal plane and the T1UEP.
Thoracic inlet angle The angle formed by a line from the center of the T1UEP vertical to the T1UEP and a line connecting the center of the T1UEP and the upper end of the sternum.
Cranial incidence The angle between the center of the line perpendicular to the McGregor line and the line that joins the middle of the McGregor line to the sella turcica Le Huec et al. (2015) [69]
Cranial slope The angle between the horizontal line and the McGregor line
Cranial tilt The angle between the vertical line and the line joining the center of the McGregor line and the sella turcica
Spino-cranial angle The angle between the C7 slope and the straight line joining the middle of the C7 end plate and the middle of the sella turcica
C2-pelvic angle The angle of a line from C2 centroid to the FH and a line from the FH to the middle of the S1 endplate Protopsaltis et al. (2017) [70]
Cervicothoracic pelvic angle The angle of a line from center of C2 to FH and a line from FH to center of T1 Protopsaltis et al. (2017) [71]
Craniocervical angle The angle of the line from the center of C7 to the posterior corner of the hard palate and McGregor’s line Protopsaltis et al. (2017) [70]
Occipitocervical inclination The angle formed by the line connecting McGregor’s line and the posterior border of the C4 vertebral body Yoon et al. (2017) [72]
Clivoaxial angle The angle subtended by lines drawn parallel to the dorsal surfaces of the clivus and dens Hashimoto et al. (2018) [73]
K-line tilt The angle between the K-line and a line perpendicular to the horizon Kim et al. (2018) [74]
C2 incidence angle The angle between a line from the center of the FH through the midpoint of the sacral superior endplate and an extended line perpendicular to C2 inferior endplate Choi et al. (2019) [76]
C2 slope The angle between the lower endplate of C2 and the horizontal plane Protopsaltis et al. (2019) [75]

UEP, upper endplate; FH, femoral head.

Table 2.
Normative cervical spine measurement values in the asymptomatic cohort in the literature, by the published year order
Study Cohort Values Remarks
Hardacker et al. [3] (1997) 100 Adult volunteers with no neck/radicular pain Total cervical lordosis: -40.0° ± 9.7° 15% of cervical lordosis originate from C4/C7
C1–2: -31.9° ± 7.0°
SVA: C7–S1 15.6 ± 11.2 mm
Gore et al. [2] (1986) 200 Asymptomatic adults (20–65 yr) C2–7: -16° ± 16° to -27° ± 14° (men), -15° ± 10° to -25° ± 16° (women) Divided age groups (20’s to 60’s) and gender. More angle in men and old age groups
Harrison et al. [64] (2000) 30 Lateral cervical radiographs C1–7: -54° By Cobb method
C2–7: -17°
Nojiri et al. [128] (2003) 313 Asymptomatic adults C1–2: -26.5° ± 7° (men), -28.9° ± 6.7° (women) Negative correlation between O–C2 angle and C2–7 angle
C2–7: -16. 102° ± 12.9°(men), -.5° ± 10.3°(women)
Kuntz et al. [5] (2007) Combined data with a literature review Occiput-C2: -14° ± 7° Pooled estimates of the mean and variance of angles were calculated
C1–2: -29° ± 7°
C2–7: -17° ± 14°
Guo et al. [130] (2011) 414 Asymptomatic volunteers O–C2: -16.3° ± 7.0° (female), -14.9° ± 6.5° (males) The optimal atlantoaxial fusion angle may be between 25° and 30°
C1–2: -28.2° ± 4.0° (females), -26.4° ± 4.6° (males)
C2–7: -12.7° ± 6.6° (female), -16.3° ± 7.3° (male)
Lee et al. [13] (2012) 77 Asymptomatic adults O–C2: -22.4°±8.5°, C2-7: -9.9°±12.5° The ratio of C0–C2: C2–7 = 77:23%
T1S: 25.7°±6.4°, NT 43.7°±6.1°, TIA 69.5°±8.6°
SVA COG-C7: 20.7±11.7mm
Abelin-Genovois et al. [78] (2014) 150 Pediatric patients, randomly selected full spine standing views in PACS database O–C2: -15.2° ± 6.7° (group 1), -18.3° ± 6.1° (group 2) Group 1: patients aged < 11 yr Group 2: teenagers older than 11 yr
C1–2: -26° ± 6.2° (group 1), -30.3° ± 6.0° (group 2)
C2–7: -6.5° ± 11.7° (group 1), -0.7° ± 11° (group2)
C7 slope: 21.3° ± 6.9° (group 1), 17.4° ± 6.6° (group 2)
Jun et al. [107] (2014) 50 Asymptomatic adults with cervical CT and radiographs (XR) T1S: 26° ± 5.9° (XR), 22.7° ± 7.2° (CT) No significant difference between the TIA on x-ray and CT
NT: 48.7° ± 7.9° (XR), 52° ± 7.4° (CT)
TIA: 75.1° ± 8.1° (XR), 74.4° ± 9° (CT)
Le Huec et al. [69] (2015) 106 Subjects with pain VAS < 2, ODI < 20%, EOS images Cranial incidence: 27.3°±4.2° One-third of the asymptomatic population had cervical kyphosis
Cranial slope/cranial tilt: 1.6°±6.8°/25°±8.5°
O–C2: -15.8°±7.1°
C1–2: -29.2°±7.2°
C2–7: -4.9°±12.8°
C7 slope: 19.6°±8.8°
Spino-cranial angle: 83°±9.1°
Núñez-Pereira et al. [103] (2015) Lateral standing cervical radiographs of 145 patients (34 asymptomatic) O–C2: -12.7°±6.9° Asymptomatic group data
C1–2: -20.8°±7.3°
C2–7: -15.8°±13.2°
C7 slope: -23.4°±11.7°
Iyer et al. [92] (2016) 115 Asymptomatic volunteers O–C2: -27.4° ± 9.4° C2–7 angle, C7 SVA increased with age
C2–7: -12.2° ± 13.6°
Endo et al. [129] (2016) 52 Healthy adults SVA C7 15.5 ± 8.9 mm
C7 tilt 21.4° ± 9.7°
Hey et al. [83] (2017) 26 Consecutive patients without cervical spine pathology C0–7: -30.7° ± 13° (standing), -46° ± 12.5° (sitting) 73% do not have lordotic C2–7 angle upon standing. Lordosis increases significantly when transitioning to erect sitting
C2–7: -0.6° ± 11.1° (standing), -17.2° ± 12.1° (sitting)
T1S: 17.4° ± 8.7° (standing), 30.2° ± 7.4° (sitting)
Chen et al. [96] (2017) 120 Asymptomatic population (group A: <20 yr; group B: 21–40 yr; group C: 41–60 yr; group D: >61 yr) C1–2: -26.2°±7.2°, -26.5°±6.7°, -24.4°±7.2°, -26.6°±5.8° (groups A, B, C, D) A gradual increase of TIA, NT, and TS, accompanied with an increased CL, is found along with aging in asymptomatic population
C2–7: -12.1°±10.6°, -12.2°±8.2°, -12.6°±13.2°, -17.6°±10.7° (groups A, B, C, D)
C7 SVA: 19.6°±13.5°, 16.6±13.6°, 9.4°±16.7°, 26.7°±10.8° (groups A, B, C, D)
T1S: 23°±7.1°, 21.1°±7.8°, 25.5°±7.6°, 28.7°±9° (groups A, B, C, D)
NT: 39.4°±8.4°, 43.8°±8°, 46.3°±9.4°, 48.2°±6.7° (groups A, B, C, D)
TIA: 62.4°±8.5°, 65°±11.9°, 71.8°±10.3°, 76.9°±8.6° (groups A, B, C, D)
Xing et al. [109] (2017) 52 Asymptomatic adults, MR images and radiographs CL: 19.1°±12.0° (XR), 3.3°±9.8° (MR) Supine MRI cannot substitute for upright cervical radiographs except thoracic inlet measurement
TIA: 70.2°±6.6° (XR), 68.9°±8.5° (MR)
T1S: 25.7°±5.0° (XR), 22.6°±6.4° (MR)
NT: 44.6°±6.1° (XR), 46.3°±8.6° (MR)
Yukawa et al. [79] (2018) 626 Symptomatic volunteers C3–7: -4.1±11.7° Increased by aging process
Khalil et al. [42] (2018) 144 Asymptomatic adults, compared kyphosis (K group) and lordosis group (L group) C0–2 angle: -42°±8° (K group), -30°±8° (L group) 32% of subjects had kyphotic (12±7°), 27% straight (0±3°) and 41% lordotic (-12±7°) cervical spines
C0–C7 angle: -41°±10° (K group), -36°±10° (L group)
Neck tilt: 47°±8° (K group), 41°±8° (L group)
TIA: 66°±8° (K group), 73°±9° (L group)
T1S: 19°±5° (K group), 32°±6° (L group)
Hey et al. [131] (2018) 60 Asymptomatic volunteers, EOS images C2–7: 24.2° (range, 0.8–73) Compared serial radiographs in the same patients
T1S: 22.9° (range, -6.7 to 57.3)
Attiah et al. [132] (2020) 210 Asymptomatic patients, compared age groups (20–30, 30–40, 40–50, 50–60, 60–70, 70–80, 80–90) C2–7: 5.0°, 5.5°, 15.0°, 18.5°, 9.0°, 19.0°, 20.0° CL, TK, cervical SVA, T1S increase with age
SVA C2–7: 21.9 mm, 23.2 mm, 17.7 mm, 18.9 mm, 29.1 mm, 36.5 mm, 30.4 mm
T1S: 23.0°, 23.0°, 22.5°, 25.0°, 26.0°, 36.0°, 36.0°

SAV, sagittal vertical axis; T1S, T1 slope; NT, neck tilt; TIA, thoracic inlet angle; PACS, picture archiving and communication system; CT, computed tomography; VAS, visual analogue scale; ODI, Oswestry Disability Index; MR, magnetic resonance; CL, cervical lordosis; TK, thoracic kyphosis.

Table 3.
Radiographic measurement of primary cervical deformity patients
Parameter Compensated type
Decompensated type
Preoperative Postoperative p-value Preoperative Postoperative p-value
Cervical parameters
 C0–1 lordosis (°) -6.4 ± 6.7 9.0 ± 4.7 < 0.01 -14.2 ± 0.9 1.1 ± 1.7 < 0.01
 C1–2 lordosis (°) -30.6 ± 1.9 -25.6 ± 1.2 < 0.01 -34.5 ± 6.7 -22.7 ± 3.0 < 0.01
 C2–7 lordosis (°) 38.3 ± 18.9 -2.2 ± 2.0 < 0.01 26.8 ± 21.1 -14.2 ± 4.6 < 0.01
 SVA COG-C7 (mm) 61.1 ± 35.1 5.0 ± 13.0 < 0.01 113.1 ± 14.9 36.5 ± 18.0 < 0.01
 SVA C2-C7 (mm) 45.8 ± 14.4 14.8 ± 6.2 < 0.01 83.0 ± 9.0 34.9 ± 6.6 < 0.01
 SVA COG (mm) 12.5 ± 36.1 4.7 ± 21.9 NS 131.6 ± 10.5 42.5 ± 39.3 < 0.01
 SVA C2 (mm) -14.3 ± 23.7 6.5 ± 19.6 < 0.01 92.8 ± 18.0 39.3 ± 35.0 < 0.01
 SVA C7 (mm) -48.6 ± 20.9 -0.4 ± 10.2 < 0.01 18.4 ± 25.4 6.0 ± 24.1 < 0.01
 T1S–CL (°) 39.2 ± 8.7 13.6 ± 4.3 < 0.01 73.0 ± 20.9 18.9 ± 5.4 < 0.01
Thoracic inlet parameters
 TIA (°) 47.5 ± 10.9 60.8 ± 4.7 < 0.01 90.2 ± 12.2 76.0 ± 4.8 0.01
 Neck tilt (°) 46.5 ± 2.4 45.1 ± 1.6 NS 44.0 ± 0.5 43.2 ± 1.2 NS
 T1 slope (°) 0.9 ± 14.3 15.8 ± 3.6 0.01 46.3 ± 11.8 33.1 ± 4.2 0.05
Thoracolumbar parameters
 T2–12 kyphosis (°) 16.8 ± 4.5 34.7 ± 6.8 < 0.01 56.0 ± 9.7 44.4 ± 3.5 < 0.01
 L1–S1 lordosis (°) -56.4 ± 8.6 -41.9 ± 8.4 < 0.01 -47.4 ± 4.2 -47.8 ± 4.4 NS
 PT (°) 6.0 ± 7.9 7.4 ± 6.1 NS (0.07) 16.4 ± 8.6 15.5 ± 7.5 NS
 SS (°) 37.0 ± 10.6 31.0 ± 8.6 < 0.01 36.1 ± 9.6 34.5 ± 12.2 NS

SAV, sagittal vertical axis; TIA, thoracic inlet angle; PT, pelvic tilt; SS, sacral slope; NS, not significant.


1. Borden AG, Rechtman AM, Gershon-Cohen G. The normal cervical lordosis. Radiology 1960;74:806-9.
crossref pmid
2. Gore DR, Sepic SB, Gardner GM. Roentgenographic findings of the cervical spine in asymptomatic people. Spine 1986;11:521-4.
crossref pmid
3. Hardacker JW, Shuford RF, Capicotto PN, et al. Radiographic standing cervical segmental alignment in adult volunteers without neck symptoms. Spine 1997;13:1472-80.
4. Boyle JJ, Milne N, Singer KP. Influence of age on cervicothoracic spinal curvature: an ex vivo radiographic survey. Clin Biomechanics 2002;17:361-7.
5. Kuntz C, Levin LS, Ondra SL, et al. Neutral upright sagittal spinal alignment from the occiput to the pelvis in asymptomatic adults: a review and resynthesis of the literature. J Neurosurg Spine 2007;6:104-12.
crossref pmid
6. Suda K, Abumi K, Ito M, et al. Local kyphosis reduces surgical outcomes of expansive open-door laminoplasty for cervical spondylotic myelopathy. Spine 2003;12:1258-62.
7. Uchida K, Nakajima H, Sato R, et al. Cervical spondylotic myelopathy associated with kyphosis of sagittal sigmoid alignment: outcome after anterior or posterior decompression. J Neurosurg Spine 2009;11:521-8.
crossref pmid
8. Pickett GE, Mitsis DK, Sekhon LH, et al. Effect of a cervical disc prosthesis on segmental and cervical spine alignment. Neurosurg Focus 2004;17:E5.
9. Johnson JP, Lauryssen C, Cambron HO. Sagittal alignment and the Bryan cervical artificial disc. Neurosurg Focus 2004;17:E14.
10. Suk KS, Kim KT, Lee JH, et al. Sagittal alignment of the cervical spine after the laminoplasty. Spine 2007;32:E656-60.
crossref pmid
11. Kim SW, Shin JH, Arbatin JJ, et al. Effects of a cervical disc prosthesis on maintaining sagittal alignment of the functional spinal unit and overall sagittal balance of the cervical spine. Eur Spine J 2008;17:20-9.
crossref pmid pdf
12. Knott PT, Mardjetko SM, Techy F. The use of the T1 sagittal angle in predicting overall sagittal balance of the spine. Spine J 2010;10:994-8.
crossref pmid
13. Lee SH, Kim KT, Seo EM, et al. The influence of thoracic inlet alignment on the craniocervical sagittal balance in asymptomatic adults. J Spinal Dis Tech 2012;25:E41-7.
14. Tang JA, Sheer JK, Smith JS, et al. The impact of standing regional cervical sagittal alignment on outcomes in posterior cervical fusion surgery. Neurosurgery 2012;71:662-9.
crossref pmid pdf
15. Oshima Y, Takeshita K, Taniguchi Y, et al. Effect of preoperative sagittal balance on cervical laminoplasty outcomes. Spine (Phila Pa 1976) 2016;41:E1265-70.
crossref pmid
16. Cho JH, Ha JK, Kim DG, et al. Does preoperative T1 slope affect radiological and functional outcomes after cervical laminoplasty? Spine (Phila Pa 1976) 2014;15 39:E1575-81.
crossref pmid
17. Fujiwara H, Oda T, Makino T, et al. Impact of cervical sagittal alignment on axial neck pain and health-related quality of life after cervical laminoplasty and in patients with cervical spondylotic myelopathy or ossification of the posterior longitudinal ligament. A prospective comparative study. Clin Spine Surg 2018;31:E245-51.
crossref pmid
18. Sakai K, Yoshii T, Hirai T, et al. Cervical sagittal imbalance is a predictor of kyphotic deformity after laminoplasty in cervical spondylotic myelopathy patients without preoperative kyphotic alignment. Spine (Phila Pa 1976) 2016;41:299-305.
crossref pmid
19. Ferch RD, Shad A, Cadoux-Hudson TA, et al. Anterior correction of cervical kyphotic deformity: effect on myelopathy, neck pain, and sagittal alignment. J Neurosurgery Spine 2004;100:13-9.
20. Gwin DE, Iannotti CA, Benzel EC, et al. Effective lordosis: analysis of sagittal spinal canal alignment in cervical spondylotic myelopathy. J Neurosurgery Spine 2009;11:667-72.
21. Sakai K, Yoshii T, Hirai T, et al. Impact of the surgical treatment for degenerative cervical myelopathy on the preoperative cervical sagittal balance: a review of prospective comparative cohort between anterior decompression with fusion and laminoplasty. Eur Spine J 2017;26:104-12.
crossref pmid pdf
22. Cabraja M, Abbushi A, Koeppen D, et al. Comparison between anterior and posterior decompression with instrumentation for cervical spondylotic myelopathy: sagittal alignment and clinical outcome. Neurosurg Focus 2010;28:E15.
23. Liu S, Lafage R, Smith JS, et al. Impact of dynamic alignment, motion and center of rotation on myelopathy grade and regional disability in cervical spondylotic myelopathy. J Neurosurg Spine 2015;23:690-700.
crossref pmid
24. Yoshida G, Alzakri A, Pointillart V, et al. Global spinal alignment in patients with cervical spondylotic myelopathy. Spine 2018;43:E154-62.
crossref pmid
25. Sasso RC, Metcalf NH, Hipp JA, et al. Sagittal alignment after Bryan cervical arthroplasty. Spine 2011;36:991-6.
crossref pmid
26. Guerin P, Obeid I, Gille O, et al. Sagittal alignment after single cervical disc arthroplasty. J Spinal Dis Tech 2012;25:10-6.
27. Faldini C, Pagkrati S, Leonetti D, et al. Sagittal segmental alignment as predictor of adjacent-level degeneration after a Cloward procedure. Clin Orthop Relat Res 2011;469:674-81.
crossref pmid
28. Hansen MA, Dip G, Kim HJ, et al. Does postsurgical cervical deformity affect the risk of cervical adjacent segment pathology? Spine 2012;37:S75-84.
crossref pmid
29. Snowden R, Miller J, Saldon T, et al. Does index level sagittal alignment determine adjacent level disc height loss? J Neurosurg Spine 2019;31:579-86.
30. Park MS, Kelly MP, Lee DH, et al. Sagittal alignment as a predictor of clinical adjacent segment pathology require surgery after anterior cervical arthrodesis. The Spine J 2014;14:1228-34.
crossref pmid
31. Hilibrand A, Tannenbaum D, Graziano G, et al. The sagittal alignment of the cervical spine in adolescent idiopathic scoliosis. J Pediatr Orthop 1995;15:627-32.
crossref pmid
32. Canavese F, Turcot K, De Rosa V, et al. Cervical spine sagittal alignment variations following posterior spinal fusion and instrumentation for adolescent idiopathic scoliosis. Eur Spine J 2011;12:1411-8.
crossref pdf
33. Blondel B, Lafage V, Schwab F, et al. Reciprocal sagittal alignment changes after posterior fusion in the setting of adolescent idiopathic scoliosis. Eur Spine J 2012;21:1964-71.
crossref pmid pmc pdf
34. Yu M, Silvestre C, Mouton T, et al. Analysis of the cervical spine sagittal alignment in young idiopathic scoliosis: a morphological classification of 120 cases. Eur Spine J 2013;22:2372-81.
crossref pmid pmc pdf
35. Roussouly P, Labelle H, Rouissi J, et al. Pre- and post-operative sagittal balance in idiopathic scoliosis: a comparison over the ages of two cohorts of 132 adolescents and 52 adults. Eur Spine J 2013;22(suppl 2):S203-15.
crossref pmid pdf
36. Charles YP, Sfeir G, Matter-Parrat V, et al. Cervical sagittal alignment in idiopathic scoliosis treated by posterior instrumentation and in situ bending. Spine 2015;40:E419-27.
37. Shimizu T, Cerpa M, Lehman RA, et al. Reciprocal change in sagittal profiles after adolescent idiopathic scoliosis surgery with segmental pedicle screw construct. A full-body X-ray analysis. Spine 2019;44:1705-14.
crossref pmid
38. Janusz P, Tyrakowski M, Kotwicki T, et al. Cervical sagittal alignment in Scheuermann disease. Spine 2015;23:E1226-32.
39. Jiang L, Qiu Y, Xu L, et al. Sagittal spinopelvic alignment in adolescents associated with Scheuermann’s kyphosis: a comparison with normal population. Eur Spine J 2014;23:1420-6.
crossref pmid pdf
40. Berthonnaud E, Dimnet J, Roussouly P, et al. Analysis of the sagittal balance of the spine and pelvis using shape and orientation parameters. J Spinal Disord Tech 2005;18:40-7.
crossref pmid
41. Lee SH, Son ES, Seo EM, et al. Factors determining cervical spine sagittal balance in asymptomatic adults: correlation with spinopelvic balance and thoracic inlet alignment. Spine J 2015;15:705-12.
crossref pmid
42. Khalil N, Bizdikian AJ, Bakouny Z, et al. Cervical and postural strategies for maintaining horizontal gaze in asymptomatic adults. Eur Spine J 2018;27:2700-9.
crossref pmid pdf
43. Smith JS, Shaffrey CI, Lafage V, et al. Spontaneous improvement of cervical alignment after correction of global sagittal balance following pedicle subtraction osteotomy. J Neurosurg Spine 2012;17:300-7.
crossref pmid
44. Ha Y, Schwab F, Lafage V, et al. Reciprocal changes in cervical spine alignment after corrective thoracolumbar deformity surgery. Eur Spine J 2014;23:552-9.
crossref pmid pdf
45. Thompson W, Cogniet A, Challali M, et al. Analysis of cervical sagittal alignment variation after lumbar pedicle subtraction osteotomy for severe imbalance: study of 59 cases. Eur Spine J 2018;27:S16-24.
crossref pdf
46. Neuman B, Harris A, Jain A, et al. Reciprocal changes in cervical alignment after thoracolumbar arthrodesis for adult spinal deformity. Spine 2019;44:E1311-6.
crossref pmid
47. Smith JS, Lafage V, Schwab FJ, et al. Prevalence and type of cervical deformity among 470 adults with thoracolumbar deformity. Spine 2014;39:E1001-9.
crossref pmid
48. Lee DH, Ha JK, Chung JH, et al. A retrospective study to reveal the effect of surgical correction of cervical kyphosis on thoraco-lumbo-pelvic sagittal alignment. Eur Spine J 2016;25:2286-93.
crossref pmid pdf
49. Mizutani Z, Verma K, Endo K, et al. Global spinal alignment in cervical kyphotic deformity: the importance of head position and thoracolumbar alignment in the compensatory mechanism. Neurosurgery 2018;82:686-94.
crossref pmid pdf
50. Mizutani Z, Strom R, Abumi K, et al. How cervical reconstruction surgery affects global spinal alignment. Neurosurgery 2019;84:898-907.
crossref pmid pdf
51. Okada E, Matsumoto M, Ichihara D, et al. Does the sagittal alignment of the cervical spine have an impact on disk degeneration? Minimum 10-year follow-up of asymptomatic volunteers. Eur Spine J 2009;18:1644-51.
crossref pdf
52. Lee JH, Park YK, Kim JH. Chronic neck pain in young adults: perspective on anatomic difference. The Spine J 2014;14:2628-38.
crossref pmid
53. Yang BS, Lee SK, Song KS, et al. The use of T1 sagittal angle in predicting cervical disc degeneration. Asian Spine J 2015;9:757-61.
crossref pmid pmc pdf
54. Iyer S, Nemai VM, Nguyen J, et al. Impact of cervical sagittal alignment parameters on neck disability. Spine 2016;41:371-7.
crossref pmid
55. Suk KS, Kim KT, Lee SH, et al. Significance of chin brow vertical angle in correction of kyphotic deformity of ankylosing spondylitis patients. Spine (Phila Pa 1976) 2003;28:2001-5.
crossref pmid
56. Lafage R, Challier V, Liabaud B, et al. Natural head posture in the setting of sagittal spinal deformity: validation of chinbrow vertical angle, slope of line of sight, and McGregor’s slope with health-related quality of life. Neurosurgery 2016;79:108-15.
crossref pmid pdf
57. Villavicencio AT, Babuska JM, Ashton A, et al. Prospective, randomized, double-blind clinical study evaluating the correlation of clinical outcomes and cervical sagittal alignment. Neurosurg 2011;68:1309-16.
crossref pdf
58. Protopsaltis TS, Scheer JK, Terran JS, et al. How the neck affects the back: changes in regional cervical sagittal alignment correlate to HRQOL improvement in adult thoracolumar deformity patients at 2-year follow-up. J Neurosurg Spine 2015;23:153-8.
crossref pmid
59. Hyun SJ, Kim KJ, Jahng TA, et al. Clinical impact of T1 slope minus cervical lordosis after multilevel posterior cervical fusion surgery. Spine 2017;42:1859-64.
crossref pmid
60. Vavruch L, Hedlund R, Javid D, et al. A prospective randomized comparison between the Cloward procedure and a carbon fiber cage in the cervical spine. Spine (Phila Pa 1976) 2002;27:1694-701.
crossref pmid
61. Lee SH, Lee JC, Tauchi R, et al. Influence of the number of cervical fusion levels on cervical spine motion and health-related quality of life. Spine 2016;41:E474-80.
crossref pmid
62. Bao H, Varghese J, Lafage R, et al. Principal radiographic characteristics for cervical spinal deformity. A Health-related quality of life analysis. Spine 2017;42:1375-82.
crossref pmid
63. Lau D, DiGiorge AM, Chan AK, et al. Applicability of cervical sagittal vertical axis, cervical lordosis and T1 slope on pain and disability outcomes after anterior cervical discectomy and fusion in patients without deformity. J Neurosurg Spine 2020;23:23-30.
64. Harrison DE, Harrison DD, Cailliet R, et al. Cobb method or Harrison posterior tangent method. Which to choose for lateral cervical radiograph analysis. Spine 2000;16:2072-8.
65. Cobb JR. Outlines for the study of scoliosis. In: Edwards JW editors. Instructional course lecture. Vol 5. Ann Arbor (MI): American Academy of Orthopedic Surgeons; 1948. p.261-75.

66. Polly DW Jr, Kilkelly FX, McHale KA, et al. Measurement of lumbar lordosis. Evaluation of intraobserver, interobserver, and technique variability. Spine (Phila Pa 1976) 1996;21:1530-6.
crossref pmid
67. Ames CP, Smith JS, Eastlack R, et al. Reliability assessment of a novel cervical spine deformity classification system. J Neurosurg Spine 2015;23:673-83.
crossref pmid
68. Diebo BG, Challier V, Henry JK, et al. Predicting cervical alignment required to maintain horizontal gaze based on global spinal alignment. Spine 2016;23:1795-80.
69. Le Huec JC, Demazon H, Aunoble S. Sagittal parameters of global cervical balance using EOS imaging: normative values from a prospective cohort of asymptomatic volunteers. Eur Spine J 2015;24:63-71.
crossref pmid pdf
70. Protopsaltis TS, Lafage R, Vira S, et al. Novel angular measures of cervical deformity account for upper cervical compensation and sagittal alignment. Clin Spine Surg 2017;30:E959-67.
71. Protopsaltis T, Bronsard N, Soroceanu A, et al. Cervical sagittal deformity develop after PJK thoracolumbar deformity correction: radiographic analysis utilizing a novel global sagittal angular parameter, the CTPA. Eur Spine J 2017;26:1111-20.
crossref pmid pdf
72. Yoon SD, Lee CH, Lee J, et al. Occipitocervical inclination: new radiographic parameter of neutral occipitocervical position. Eur Spine J 2017;26:2297-302.
crossref pdf
73. Hashimoto K, Miyamoto H, Ikeda T, et al. Radiologic features of dropped head syndrome in the overall sagittal alignment of the spine. Eur Spine J 2018;27:467-74.
crossref pmid pdf
74. Kim HS, Kim TH, Park MS, et al. K-line tilt as a novel radiographic parameter in cervical sagittal alignment. Eur Spine J 2018;27:2023-8.
crossref pmid pdf
75. Protopsaltis TS, Ramchandran S, Tishelman JS, et al. The importance of C2 slope, a singular marker of cervical deformity, correlates with patient-reported outcomes. Spine 2019;45:184-92.
76. Choi CS, Lee DH, Hwang CJ, et al. Effectiveness of C2 incidence angle for evaluating global spinopelvic alignment in patients with mild degenerative spondylosis. World Neurosurg 2019;127:e826-34.
77. Kim SW, Kim TH, Bok DH, et al. Analysis of cervical spine alignment in currently asymptomatic individuals: prevalence of kyphotic posture and its relationship with other spinopelvic parameters. Spine J 2018;18:797-810.
crossref pmid
78. Abelin-Genovois K, Idjerouidene A, Roussouly R, et al. Cervical spine alignment in the pediatric population: a normative study of 150 asymptomatic patients. Eur Spine J 2014;23:1442-8.
crossref pmid pdf
79. Yukawa Y, Kato F, Suda K, et al. Normative data for parameters of sagittal spinal alignment in healthy subject: an analysis of gender specific differences and changes with aging in 626 asymptomatic individuals. Eur Spine J 2018;27:426-32.
crossref pdf
80. Yoshimoto H, Ito M, Abumi K, et al. A retrospective analysis of subaxial sagittal alignment after posterior C1-C2 fusion. Spine 2004;29:175-81.
crossref pmid
81. Mukai Y, Hosono N, Sakaura H, et al. Sagittal alignment of the subaxial cervical spine after C1-C2 transarticular screw fixation in rheumatoid arthritis. J Spinal Dis Tech 2007;20:436-41.
82. Kim JT, Lee HJ, Choi DY, et al. Sequential alignment change of the cervical spine after anterior cervical discectomy and fusion in the lower cervical spine. Eur Spine J 2016;25:2223-32.
crossref pmid pdf
83. Hey HWD, Lau ET, Tan K, et al. Cervical alignment variations in different posture and predictors of normal cervical kyphosis. Spine 2017;42:1614-21.
crossref pmid
84. Singhatandgige W, Kang DG, Luksanapruksa P, et al. Correlation and reliability of cervical sagittal alignment parameters between lateral cervical radiograph and lateral wholebody EOS stereoradiograph. Global Spine J 2015;6:548-54.
crossref pmid pmc
85. Janusz P, Tyrakowski M, Glowka P, et al. Influence of cervical spine position on the radiographic parameters of the thoracic inlet alignment. Eur Spine J 2015;24:2880-4.
crossref pdf
86. Weng C, Wang J, Tuchman A, et al. Influence of T1 slope on the cervical sagittal balance in degenerative cervical spine. An analysis using kinematic MRI. Spine 2016;41:185-90.
crossref pmid
87. Park MS, Moon SH, Lee HM, et al. Age-related changes in cervical sagittal range of motion and alignment. Global Spine J 2014;4:151-6.
crossref pmid pmc
88. Kim HJ, Lenke LG, Oshima Y, et al. Cervical lordosis actually increases with aging and progressive degeneration in spinal deformity patients. Spine Deform 2014;2:430-14.
crossref pmid
89. Yoshida G, Yasuda T, Togawa D, et al. Cranopelvic alignment in elderly asymptomatic individuals. Spine 2014;39:1121-7.
crossref pmid
90. Legaye J. Influence of age and sagittal balance of the spine on the value of the pelvic incidence. Eur Spine J 2014;23:1394-9.
crossref pmid pdf
91. Oe S, Togawa D, Nakai K, et al. The influence of age and sex on cervical spinal alignment among volunteers aged over 50. Spine 2015;40:1487-94.
crossref pmid
92. Iyer S, Lenke LG, Nemani VM, et al. Variations in sagittal alignment parameters based on age. A prospective study of asymptomatic volunteers using full-body radiographs. Spine 2016;41:1826-36.
crossref pmid
93. Park MS, Moon SH, Kim TH, et al. Radiographic comparison between cervical spine lateral and whole-spine lateral standing radiographs. Global Spine J 2016;6:118-23.
crossref pmid
94. Machino M, Yukawa Y, Imagama S, et al. Age-related and degenerative changes in the osseous anatomy, alignment, and range of motion of the cervical spine. A comparative study of radiographic data from 1016 patients with cervical spondylotic myelopathy and 1230 symptomatic subjects. Spine 2016;41:476-82.
crossref pmid
95. Tang R, Ye IB, Cheung ZB, et al. Age-related changes in cervical sagittal alignment. Spine 2019;44:E1144-50.
crossref pmid
96. Chen Y, Luo J, Pan Z, et al. The changes of cervical spine alignment along with aging in asymptomatic population: a preliminary analysis. Eur Spine J 2017;26:2363-71.
crossref pmid pdf
97. Liu J, Li P, Ma Z, et al. The effect of aging on the profile of the cervical spine. Medicine 2019;98:e14425.
crossref pmid pmc
98. Legaye J, Duval-Beaupere G. Influence of a variation in the position of the arms on the sagittal connection of the gravity line with the spinal structure. Eur Spine J 2017;26:2828-33.
crossref pmid pdf
99. Park SM, Song KS, Park SH, et al. Does whole-spine lateral radiograph with clavicle positioning reflect the correct cervical sagittal alignment? Eur Spine J 2015;24:57-62.
crossref pmid pdf
100. Kusakabe T, Endo K, Aihara T, et al. Difference in cervical sagittal alignment between the standing and sitting positions. J Orthop Sci 2019;24:1005-9.
101. Hey HWD, Teo AQA, Tan K, et al. How the spine differs in standing and in sitting-important considerations for correction of spinal deformity. Spine J 2017;17:799-806.
crossref pmid
102. Lee HJ, Kim JH, Kim IS, et al. Physiologic cervical alignment change between whole spine radiographs and normal standing cervical radiographs. World Neurosurg 2019;122:e1222-7.
crossref pmid
103. Núñez-Pereira S, Hitzl W, Bullmann V, et al. Sagittal balance of the cervical spine: an analysis of occipitocerivcal and spinopelvic interdependence, with C-7 slope as a marker of cervical and spinopelvic alignment. J Neurosurg Spine 2015;12:16-23.
104. Tamai K, Buser Z, Paholpak P, et al. Can C7 slope substitute the T1 slope? An analysis of cervical spine raiographs and kinematic MRIs. Spine 2018;43:520-5.
crossref pmid
105. Sun J, Zhao HW, Wang JJ, et al. Diagnostic value of T1 slope in degenerative cervical spondylotic myelopathy. Med Sci Monit 2018;24:791-6.
crossref pmid pmc
106. Ye IB, Tang R, Cheung ZB, et al. Can C7 slope be used as a substitute for T1 slope? A radiographic analysis. Global Spine J 2020;10:148-52.
crossref pmid
107. Jun HS, Chang IB, Song JH, et al. Is it possible to evaluate the parameters of cervical sagittal alignment on cervical computed tomographic scans? Spine 2014;39:E630-6.
crossref pmid
108. Paholpak P, Nazareth A, Hsieh PC, et al. Kinematic evaluation of cervical sagittal balance and thoracic inlet alignment in degenerative cervical spondylolisthesis using kinematic magnetic resonance imaging. Spine J 2017;17:1272-84.
109. Xing R, Zhou G, Chen Q, et al. MRI to measure cervical sagittal parameters: a comparison with plain radiographs. Arch Orthop Trauma Surg 2017;137:451-5.
crossref pmid pdf
110. Zhang J, Buser Z, Abedi A, et al. Can C2-6 Cobb angle replace C2-7 Cobb angle? An analysis of cervical kinetic magnetic resonance images and X-rays. Spine 2018;44:240-5.
111. Oshina M, Tanaka M, Oshima Y, et al. Correlation and differences in cervical sagittal alignment parameters between cervical radiographs and magnetic resonance images. Eur Spine J 2018;27:1408-15.
crossref pmid pdf
112. Passias PG, Jalai CK, Lafage V, et al. Primary drivers of adult cervical deformity: prevalence, variation in presentation, and effect of surgical treatment strategies on early postoperative alignment. Neurosurgery 2018;83:651-9.
crossref pmid pdf
113. Passias PG, Vasquez-Montes D, Poorman GW, et al. Predictive model for distal junctional kyphosis after cervical deformity surgery. Spine J 2018;18:2187-94.
crossref pmid
114. Lee SH, Raad M, Neuman BJ, et al. The C5-T3 angle: a novel parameter of the cervicothoracic junction. Spine J 2018;18(8 Suppl):S127. -8.
115. Lee SH, Kebaish KM, Sponseller PD. Upper thoracic osteotomy for cervical deformity. In: Ames CP, Riew KD, Smith JS, Abumi K editors. Cervical spine deformity surgery. New York: Thieme; 2019. p.100-10.

116. Lamartina C, Berjano P. Classification of sagittal imbalance based on spinal alignment and compensatory mechanisms. Eur Spine J 2014;23:1177-89.
crossref pmid pdf
117. Koller H, Ames C, Mehdian H, et al. Characteristics of deformity surgery in patients with severe and rigid cervical kyphosis (CK): results of the CSRS-Europe multi-centre study project. Eur Spine J 2019;28:324-44.
crossref pmid pdf
118. Virk S, Passias P, Lafage R, et al. Intraoperative alignment goals for distinctive sagittal morphotypes of severe cervical deformity to achieve optimal improvements in health-related quality of life measures. Spine J 2020;201267-75.
119. Murata K, Kenji E, Suzuki H, et al. Spinal sagittal alignment in patients with dropped head syndrome. Spine 2018;43:E1267-73.
crossref pmid
120. Endo K, Kudo Y, Suzuki H, et al. Overview of dropped head syndrome (combined survey report of three facilities). J Orthop Sci 2019;24:1033-6.
crossref pmid
121. Pan Z, Luo J, Yu L, et al. Debridement and reconstruction improve postoperative sagittal alignment in kyphotic cervical spinal tuberculosis. Clin Orthop Relat Res 2017;475:2084-91.
crossref pmid pmc pdf
122. Wang Q, Wang Xt, Zhu L, et al. Thoracic inlet parameters for degenerative cervical spondylolisthesis imaging measurement. Med Sci Monit 2018;24:2025-30.
crossref pmid pmc
123. Song J, Cui ZY, Chen ZH, et al. Analysis of the effect of surgical treatment for the patients with Hirayama disease from the perspective of cervical spine sagittal alignment. World Neurosurg 2020;133:e342-7.
crossref pmid
124. Ajello M, Marengo M, Pilloni G, et al. Is it possible to evaluate the ideal cervical alignment for each patient needing surgery? An easy rule to determine the appropriate cervical lordosis in preoperative planning. World Neurosurg 2017;97:471-8.
crossref pmid
125. Staub BN, Lafage R, Kim HJ, et al. Cervical mismatch: the normative value of T1 slope minus cervical lordosis and its ability to predict ideal cervical lordosis. J Neurosurg Spine 2019;30:31-7.
126. Goldschmidt E, Angriman F, et al. A new piece of the puzzle to understand cervical sagittal alignment: utilizing a novel angle δ to describe the relationship among T1 vertebral body slope, cervical lordosis, and cervical sagittal alignment. Neurosurgery 2020;86:446-51.
crossref pmid pdf
127. Zhu Y, An Z, Zhang Y, et al. Predictive formula of cervical lordosis in asymptomatic young population. J Orthop Surg Res 2020;15:2.
crossref pmid pmc pdf
128. Nojiri K, Matsumoto M, Chiba K, et al. Relationship between alignment of upper and lower cervical spine in asymptomatic individuals. J Neurosurg 2003;99(1 Suppl):80-3.
crossref pmid
129. Endo K, Suzuki H, Sawaji Y, et al. Relationship among cervical, thoracic, and lumbopelvic sagittal alignment in healthy adults. J Orthopaedic Surg 2016;24:92-6.
130. Guo Q, Ni B, Yang J, et al. Relation between alignments of upper and subaxial cervical spine: a radiological study. Acta Orthop Trauma Surg 2011;131:857-62.
crossref pdf
131. Hey HWD, Tan KLM, Moorthy V, et al. Normal variation in sagittal spinal alignment parameters in adult patients: an EOS study using serial imaging. Eur Spine J 2018;27:578-84.
crossref pmid pdf
132. Attiah M, Gaonkar B, Alkhalid Y, et al. Natural history of the aging spine: a cross-sectional analysis of spinopelvic parameters in the asymptomatic population. J Neurosurg Spine 2020;32:63-8.

Editorial Office
Department of Neurosurgery, Yonsei University College of Medicine
50-1, Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
Tel: +82-2-2228-2158  E-mail:
The Korean Spinal Neurosurgery Society
#407, Dong-A Villate 2nd Town, 350 Seocho-daero, Seocho-gu, Seoul 06631, Korea
Tel: +82-2-585-5455  Fax: +82-2-2-523-6812  E-mail:
Business License No.: 209-82-62443

Copyright © The Korean Spinal Neurosurgery Society. All rights reserved.

Developed in M2community

Close layer
prev next