Cervical spine alignment, sagittal deformity, and clinical implications

This paper is a narrative review of normal cervical alignment, methods for quantifying alignment, and how alignment is associated with cervical deformity, myelopathy, and adjacent-segment disease (ASD), with discussions of health-related quality of life (HRQOL). Popular methods currently used to quantify cervical alignment are discussed including cervical lordosis, sagittal vertical axis, and horizontal gaze with the chin-brow to vertical angle. Cervical deformity is examined in detail as deformities localized to the cervical spine affect, and are affected by, other parameters of the spine in preserving global sagittal alignment. An evolving trend is defining cervical sagittal alignment. Evidence from a few recent studies suggests correlations between radiographic parameters in the cervical spine and HRQOL. Analysis of the cervical regional alignment with respect to overall spinal pelvic alignment is critical. The article details mechanisms by which cervical kyphotic deformity potentially leads to ASD and discusses previous studies that suggest how postoperative sagittal malalignment may promote ASD. Further clinical studies are needed to explore the relationship of cervical malalignment and the development of ASD. Sagittal alignment of the cervical spine may play a substantial role in the development of cervical myelopathy as cervical deformity can lead to spinal cord compression and cord tension. Surgical correction of cervical myelopathy should always take into consideration cervical sagittal alignment, as decompression alone may not decrease cord tension induced by kyphosis. Awareness of the development of postlaminectomy kyphosis is critical as it relates to cervical myelopathy. The future direction of cervical deformity correction should include a comprehensive approach in assessing global cervicalpelvic relationships. Just as understanding pelvic incidence as it relates to lumbar lordosis was crucial in building our knowledge of thoracolumbar deformities, T-1 incidence and cervical sagittal balance can further our understanding of cervical deformities. Other important parameters that account for the cervical-pelvic relationship are surveyed in detail, and it is recognized that all such parameters need to be validated in studies that correlate HRQOL outcomes following cervical deformity correction.

Download Full-text

Cervical sagittal alignment after Prestige LP cervical disc replacement: radiological results and clinical impacts from a single-center experience

BMC Musculoskeletal Disorders ◽

10.1186/s12891-021-03962-x ◽

2021 ◽

Vol 22 (1) ◽

Author(s):

Xiaofei Wang ◽

Yang Meng ◽

Hao Liu ◽

Hua Chen ◽

Beiyu Wang ◽

...

Keyword(s):

Sagittal Alignment ◽

Disc Replacement ◽

Cervical Disc ◽

Adjacent Segment ◽

Single Center ◽

Disc Disease ◽

Sagittal Vertical Axis ◽

Cervical Disc Replacement ◽

Cervical Sagittal Alignment ◽

The Impact

Abstract Background Cervical disc replacement (CDR) has been widely used to treat one- and two-level cervical degenerative disc disease. Studies have shown the effectiveness of CDR in preserving range of motion (ROM) and delaying adjacent segment degeneration (ASD). Cervical sagittal alignment is an important factor affecting favorable clinical outcomes in cervical spine surgery. This study aimed to explore whether cervical sagittal alignment can be maintained after CDR and to identify the impact of cervical sagittal alignment on outcomes after CDR. Methods This was a single-center, retrospective study. 132 patients who underwent one-level CDR were included. Cervical sagittal alignments, including cervical lordosis (CL), segmental alignment (SA), sagittal vertical axis (SVA), T1 slope (T1s), and T1s minus CL (T1s-CL), were measured. The effects of cervical sagittal alignment on the CDR outcomes were analyzed. Patients were divided into the heterotopic ossification (HO) group and ASD group to determine the potential impacts of cervical sagittal parameters. Results The cervical sagittal alignment parameters, except for the SVA, were significantly improved after CDR and showed decreasing trends at the last follow-up. Significantly higher CL and T1s were found in patients with better ROM after CDR. SVA ≥ 20 mm increased the risk of anterior HO (odds ratio = 2.945, P = 0.007). Significantly kyphotic SA and lower T1s values were found in the ASD patients than in the non-ASD patients (P < 0.05). Patients with ASD at the inferior level showed significantly worse CL (P < 0.05). Conclusion CDR had limited function of improving cervical sagittal alignment. Poor cervical sagittal alignment after CDR was associated with HO, ASD, and less ROM.

Download Full-text

The association of cervical sagittal alignment with adjacent segment degeneration

European Spine Journal ◽

10.1007/s00586-019-06157-0 ◽

2019 ◽

Vol 29 (11) ◽

pp. 2655-2664 ◽

Cited By ~ 1

Author(s):

Xiaoyu Yang ◽

Ronald H. M. A. Bartels ◽

Roland Donk ◽

Mark P. Arts ◽

Caroline M. W. Goedmakers ◽

...

Keyword(s):

Cervical Spine ◽

Sagittal Alignment ◽

Neck Disability Index ◽

Adjacent Segment Degeneration ◽

Adjacent Segment ◽

Trial Register ◽

Sf 36 ◽

Cervical Sagittal Alignment ◽

Intervertebral Cage

Abstract Purpose Cervical spine surgery may affect sagittal alignment parameters and induce accelerated degeneration of the cervical spine. Cervical sagittal alignment parameters of surgical patients will be correlated with radiological adjacent segment degeneration (ASD) and with clinical outcome parameters. Methods Patients were analysed from two randomized, double-blinded trials comparing anterior cervical discectomy with arthroplasty (ACDA), with intervertebral cage (ACDF) and without intervertebral cage (ACD). C2–C7 lordosis, T1 slope, C2–C7 sagittal vertical axis (SVA) and the occipito-cervical angle (OCI) were determined as cervical sagittal alignment parameters. Radiological ASD was scored by the combination of decrease in disc height and anterior osteophyte formation. Neck disability index (NDI), SF-36 PCS and MCS were evaluated as clinical outcomes. Results The cervical sagittal alignment parameters were comparable between the three treatment groups, both at baseline and at 2-year follow-up. Irrespective of surgical method, C2–C7 lordosis was found to increase from 11° to 13°, but the other parameters remained stable during follow-up. Only the OCI was demonstrated to be associated with the presence and positive progression of radiological ASD, both at baseline and at 2-year follow-up. NDI, SF-36 PCS and MCS were demonstrated not to be correlated with cervical sagittal alignment. Likewise, a correlation with the value or change of the OCI was absent. Conclusion OCI, an important factor to maintain horizontal gaze, was demonstrated to be associated with radiological ASD, suggesting that the occipito-cervical angle influences accelerated cervical degeneration. Since OCI did not change after surgery, degeneration of the cervical spine may be predicted by the value of OCI. NECK trial Dutch Trial Register Number NTR1289. PROCON trial Trial Register Number ISRCTN41681847. Graphic abstract These slides can be retrieved under Electronic Supplementary Material.

Download Full-text

An assessment of the most reliable method to estimate the sagittal alignment of the cervical spine: analysis of a prospective cohort of 138 cases

Journal of Neurosurgery Spine ◽

10.3171/2016.10.spine16632 ◽

2017 ◽

Vol 26 (5) ◽

pp. 572-576 ◽

Cited By ~ 6

Author(s):

Roland D. Donk ◽

Michael G. Fehlings ◽

Wim I. M. Verhagen ◽

Hisse Arnts ◽

Hans Groenewoud ◽

...

Keyword(s):

Cervical Spine ◽

Vertebral Body ◽

Sagittal Balance ◽

Interrater Reliability ◽

Sagittal Alignment ◽

Controlled Trial ◽

Cervical Alignment ◽

Cervical Sagittal Alignment ◽

Tangent Method ◽

The Mean

OBJECTIVEAlthough there is increasing recognition of the importance of cervical spinal sagittal balance, there is a lack of consensus as to the optimal method to accurately assess the cervical sagittal alignment. Cervical alignment is important for surgical decision making. Sagittal balance of the cervical spine is generally assessed using one of two methods; namely, measuring the angle between C-2 and C-7, and drawing a line between C-2 and C-7. Here, the best method to assess sagittal alignment of the cervical spine is investigated.METHODSData from 138 patients enrolled in a randomized controlled trial (Procon) were analyzed. Two investigators independently measured the angle between C-2 and C-7 by using Harrison's posterior tangent method, and also estimated the shape of the sagittal curve by using a modified Toyama method. The mean angles of each quantitative assessment of the sagittal alignment were calculated and the results were compared. The interrater reliability for both methods was estimated using Cronbach's alpha.RESULTSFor both methods the interrater reliability was high: for the posterior tangent method it was 0.907 and for the modified Toyama technique it was 0.984. For a lordotic cervical spine, defined by the modified Toyama method, the mean angle (defined by Harrison's posterior tangent method) was 23.4° ± 9.9° (range 0.4°–52.4°), for a kyphotic cervical spine it was −2.2° ± 9.2° (range −16.1° to 16.9°), and for a straight cervical spine it was 10.5° ± 8.2° (range −11° to 36°).CONCLUSIONSAn absolute measurement of the angle between C-2 and C-7 does not unequivocally define the sagittal cervical alignment. As can be seen from the minimum and maximum values, even a positive angle between C-2 and C-7 could be present in a kyphotic spine. For this purpose, the modified Toyama method (drawing a line from the posterior inferior part of the vertebral body of C-2 to the posterior upper part of the vertebral body of C-7 without any measurements) is a better tool for a global assessment of cervical sagittal alignment.Clinical trial registration no.: ISRCTN41681847 (https://www.isrctn.com)

Download Full-text

Radiographic analysis of the correlation between ossification of the nuchal ligament and sagittal alignment and segmental stability of the cervical spine in patients with cervical spondylotic myelopathy

Acta Radiologica ◽

10.1177/0284185118778866 ◽

2018 ◽

Vol 60 (2) ◽

pp. 196-203 ◽

Cited By ~ 1

Author(s):

Jinwei Ying ◽

Honglin Teng ◽

Yunfan Qian ◽

Yingying Hu ◽

Tianyong Wen ◽

...

Keyword(s):

Cervical Spine ◽

Cervical Spondylotic Myelopathy ◽

Sagittal Alignment ◽

Angular Displacement ◽

Radiographic Finding ◽

Control Group ◽

Chronic Injury ◽

Sagittal Vertical Axis ◽

Cervical Sagittal Alignment ◽

Nuchal Ligament

Background Ossification of the nuchal ligament (ONL) caused by chronic injury to the nuchal ligament (NL) is very common in instability-related cervical disorders. Purpose To determine possible correlations between ONL, sagittal alignment, and segmental stability of the cervical spine. Material and Methods Seventy-three patients with cervical spondylotic myelopathy (CSM) and ONL (ONL group) and 118 patients with CSM only (control group) were recruited. Radiographic data included the characteristics of ONL, sagittal alignment and segmental stability, and ossification of the posterior longitudinal ligament (OPLL). We performed comparisons in terms of radiographic parameters between the ONL and control groups. The correlations between ONL size, cervical sagittal alignment, and segmental stability were analyzed. Multivariate logistic regression was used to identify the independent risk factors of the development of ONL. Results C2–C7 sagittal vertical axis (SVA), T1 slope (T1S), T1S minus cervical lordosis (T1S-CL) on the lateral plain, angular displacement (AD), and horizontal displacement (HD) on the dynamic radiograph increased significantly in the ONL group compared with the control group. The size of ONL significantly correlated with C2–C7 SVA, T1S, AD, and HD. The incidence of ONL was higher in patients with OPLL and segmental instability. Cervical instability, sagittal malalignment, and OPLL were independent predictors of the development of ONL through multivariate analysis. Conclusion Patients with ONL are more likely to have abnormal sagittal alignment and instability of the cervical spine. Thus, increased awareness and appreciation of this often-overlooked radiographic finding is warranted during diagnosis and treatment of instability-related cervical pathologies and injuries.

Download Full-text

The Influence of Natural Head Position on the Cervical Sagittal Alignment

Journal of Healthcare Engineering ◽

10.1155/2017/2941048 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7

Author(s):

Kuan Wang ◽

Zhen Deng ◽

Zhengyan Li ◽

Huihao Wang ◽

Hongsheng Zhan

Keyword(s):

Cervical Spine ◽

Sagittal Alignment ◽

Vertical Axis ◽

Head Position ◽

Biomechanical Analysis ◽

Sagittal Vertical Axis ◽

Cervical Sagittal Alignment ◽

Backward Shift ◽

The Relationship ◽

Curvature Type

Introduction. This study investigated the relationship between the parameters related to the natural head position and cervical segmental angles and alignment of patients with neck pain. Material and Methods. The lateral radiographs of the cervical spine were collected from 103 patients and were used to retrospectively analyze the correlation between the natural head position, cervical local sagittal angles, and alignment. Sagittal measurements were as follows: cervical curvature classification, slope of McGregor’s line (McGS), local sagittal angles (C0–C2 angle, C2–C5 angle, C5–C7 angle, and C2–C7 angle), T1 slope, center of gravity of the head to sagittal vertical axis (CG–C7 SVA), and local sagittal alignment (C0–C2 SVA and C2–C7 SVA). Results. McGS was significantly correlated to C0–C2 angle (r=0.57), C0–C2 SVA (r=−0.53), C2–C7 SVA (r=−0.28), and CG–C7 SVA (r=−0.47). CG–C7 SVA was also significantly correlated to curvature type (r=0.27), C5–C7 angle (r=−0.37), and C2–C7 angle (r=−0.39). Conclusions. A backward shift with an extended head position may accompany a relatively normal curvature of the cervical spine. The effect of posture control in relieving abnormal mechanical state of the cervical spine needs to be further confirmed by biomechanical analysis.

Download Full-text

The Sagittal Balance of the Cervical Spine: Radiographic Analysis of Interdependence between the Occipitocervical and Spinopelvic Alignment

Asian Spine Journal ◽

10.31616/asj.2019.0165 ◽

2020 ◽

Vol 14 (3) ◽

pp. 287-297 ◽

Cited By ~ 1

Author(s):

Babak Alijani ◽

Javid Rasoulian

Keyword(s):

Cobb Angle ◽

Sagittal Balance ◽

Sagittal Alignment ◽

Surgical Reconstruction ◽

Sagittal Imbalance ◽

Sagittal Vertical Axis ◽

Asymptomatic Patients ◽

Significant Difference ◽

Cervical Sagittal Alignment ◽

Global Sagittal Alignment

Study Design: This was a prospective clinical study.Purpose: Previous studies have indicated that cervical lordosis is a parameter influenced by segmental and global spinal sagittal balance parameters. However, this correlation still remains unclear. Therefore, a better understanding of the normal values and interdependencies between inter-segmental alignment parameters is needed. This is a preliminary analysis that helps to understand these factors.Overview of Literature: Change in global sagittal alignment is associated with poor health-related quality of life. Questions regarding which parameters play the primary roles in the progression of spinal sagittal imbalance and which might be compensatory factors remain unanswered.Methods: Prospectively, 420 adults (105 asymptomatic, 105 cervical symptomatic, 105 lumbar symptomatic, and 105 post-surgical) were selected. Whole-spine standing lateral radiographs were taken, and spinopelvic, thoracic, and cervical parameters were measured. Then, the data were analyzed using correlation coefficient test and multiple regression analysis.Results: All the parameters showed a normal distribution. The mean values of the cervical parameters are as follows: C1C2 Cobb angle, −27.07°±4.3°; C2C7 Cobb angle, −16.4°±5.6°; OCC2 Cobb angle, −14.5°±3.8°; OCC7 Cobb angle, −29.8°±5.6°; C2C7 Harrison angle, 20.4°±4.3°; and C7 slope, −25.4°±5.6°. The analysis of these parameters revealed no statistically significant difference between asymptomatic, symptomatic, and post-surgical patients. C7 sagittal vertical axis (SVA) correlated with the C2C7 Cobb angle (r =0.7) in all groups. No significant correlation was noted between cervical and spinopelvic parameters in asymptomatic patients. However, C1C2 Cobb angle correlated significantly with pelvic incidence (PI, r =−0.2), lumbar lordosis (LL, r =0.2), and pelvic tilt (PT, r =−0.2) in cervical symptomatic patients. Irrespective of the patient symptom sub-group (n=420), C1C2 Cobb angle correlated with LL (r =0.1) and C2C7 Harrison angle correlated with PI and PT (r =0.1).Conclusions: Our results indicate significant interdependence between the spinopelvic and cervical alignment, especially in cervical symptomatic patients. In addition, strong correlation was found between the C7 SVA and C2C7 Cobb angle. Overall, the results of this study could help to better understand the cervical sagittal alignment and serve as preliminary data for planning surgical reconstruction procedures.

Download Full-text

Lumbar Level Significantly Influences Postoperative Global Sagittal Balance Following Pedicle Subtraction Osteotomy

Global Spine Journal ◽

10.1177/21925682211032563 ◽

2021 ◽

pp. 219256822110325

Author(s):

Athan G. Zavras ◽

T. Barrett Sullivan ◽

Navya Dandu ◽

Howard S. An ◽

Christopher J. DeWald ◽

...

Keyword(s):

Sagittal Balance ◽

Sagittal Alignment ◽

Adult Spinal Deformity ◽

Vertical Axis ◽

Pedicle Subtraction Osteotomy ◽

Current Evidence ◽

Sacral Slope ◽

Sagittal Vertical Axis ◽

Lumbar Level ◽

Global Sagittal Alignment

Study Design: Retrospective cohort study. Objectives: The current evidence regarding how level of lumbar pedicle subtraction osteotomy (PSO) influences correction of sagittal alignment is limited. This study sought to investigate the relationship of lumbar level and segmental angular change (SAC) of PSO with the magnitude of global sagittal alignment correction. Methods: This study retrospectively evaluated 53 consecutive patients with adult spinal deformity who underwent lumbar PSO at a single institution. Radiographs were evaluated to quantify the effect of PSO on lumbar lordosis (LL), thoracic kyphosis (TK), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), T1-spinopelvic inclination (T1SPI), T1-pelvic alignment (TPA), and sagittal vertical axis (SVA). Results: Significant correlations were found between PSO SAC and the postoperative increase in LL ( r = 0.316, P = .021) and PT ( r = 0.352, P = .010), and a decrease in TPA ( r = −0.324, P = .018). PSO level significantly correlated with change in T1SPI ( r = −0.305, P = .026) and SVA ( r = −0.406, P = .002), with more caudal PSO corresponding to a greater correction in sagittal balance. On multivariate analysis, more caudal PSO level independently predicted a greater reduction in T1SPI (β = −3.138, P = .009) and SVA (β = −29.030, P = .001), while larger PSO SAC (β = −0.375, P = .045) and a greater number of fusion levels (β = −1.427, P = .036) predicted a greater reduction in TPA. Conclusion: This study identified a gain of approximately 3 degrees and 3 cm of correction for each level of PSO more caudal to L1. Additionally, a larger PSO SAC predicted greater improvement in TPA. While further investigation of these relationships is warranted, these findings may help guide preoperative PSO level selection.

Download Full-text

Obesity does not impact clinical outcome but affects cervical sagittal alignment and adjacent segment degeneration in short term follow-up after an anterior cervical decompression and fusion

The Spine Journal ◽

10.1016/j.spinee.2019.02.016 ◽

2019 ◽

Vol 19 (7) ◽

pp. 1146-1153 ◽

Cited By ~ 1

Author(s):

Bryce A. Basques ◽

Jannat M. Khan ◽

Philip K. Louie ◽

Jeremy Mormol ◽

Steven Heidt ◽

...

Keyword(s):

Clinical Outcome ◽

Sagittal Alignment ◽

Adjacent Segment Degeneration ◽

Adjacent Segment ◽

Short Term ◽

Anterior Cervical Decompression ◽

Cervical Sagittal Alignment

Download Full-text

Magnetic resonance imaging assessment of degenerative cervical myelopathy: a review of structural changes and measurement techniques

Neurosurgical FOCUS ◽

10.3171/2016.3.focus1667 ◽

2016 ◽

Vol 40 (6) ◽

pp. E5 ◽

Cited By ~ 61

Author(s):

Aria Nouri ◽

Allan R. Martin ◽

David Mikulis ◽

Michael G. Fehlings

Keyword(s):

Spinal Cord ◽

Cervical Spine ◽

Cervical Myelopathy ◽

Structural Changes ◽

Sagittal Alignment ◽

Measurement Techniques ◽

Cord Compression ◽

Age Related ◽

Magnetic Resonance Imaging Assessment ◽

Degenerative Cervical Myelopathy

Degenerative cervical myelopathy encompasses a spectrum of age-related structural changes of the cervical spine that result in static and dynamic injury to the spinal cord and collectively represent the most common cause of myelopathy in adults. Although cervical myelopathy is determined clinically, the diagnosis requires confirmation via imaging, and MRI is the preferred modality. Because of the heterogeneity of the condition and evolution of MRI technology, multiple techniques have been developed over the years in an attempt to quantify the degree of baseline severity and potential for neurological recovery. In this review, these techniques are categorized anatomically into those that focus on bone, ligaments, discs, and the spinal cord. In addition, measurements for the cervical spine canal size and sagittal alignment are also described briefly. These tools have resulted collectively in the identification of numerous useful parameters. However, the development of multiple techniques for assessing the same feature, such as cord compression, has also resulted in a number of challenges, including introducing ambiguity in terms of which methods to use and hindering effective comparisons of analysis in the literature. In addition, newer techniques that use advanced MRI are emerging and providing exciting new tools for assessing the spinal cord in patients with degenerative cervical myelopathy.

Download Full-text