Cervical Sagittal Parameters Research Articles

Comparison of Cervical Sagittal Parameters among Patients with Neck Pain and Patients with Cervical Spondylotic Radiculopathy and Cervical Spondylotic Myelopathy.

Previous studies have shown that cervical sagittal alignment is strongly associated with cervical deformity, myelopathy, and cervical adjacent-segmental disease, and these cervical sagittal parameters are correlated with health-related quality of life. However, less attention has been paid to cervical sagittal balance in various cervical disorders. This study aimed to compare cervical sagittal parameters between patients with nonspecific neck pain (NS-NP) and patients with cervical spondylotic radiculopathy (CSR) and cervical spondylotic myelopathy (CSM). We retrospectively examined 236 patients from between January 2020 and October 2022. We divided them into three groups (NS-NP, CSR, and CSM) and collected general information and cervical sagittal parameters for these patients. The variation of parameters between the size of these parameters and gender differences was analyzed. Pearson's or Spearman's correlation was applied to analyze the association of cervical sagittal parameters of all patients between the three groups. There were significant differences in age and sex among the three groups (p < 0.001), with the NS-NP group being the youngest and NS-NP being more common in women. The parameters of cervical sagittal position significantly differed among the three groups (p < 0.05). Pearson's or Spearman's correlation result showed that the C2-C7 Cobb angle was negatively associated with the C2-C7 sagittal vertical angle (SVA), and the C2-C7 Cobb angle and T1 slope (T1s) were negatively associated with the spino-cranial angle (SCA). There was a positive correlation between the C2-C7 Cobb angle and C7 slope (C7s), C2-C7 SVA and T1s, C2-C7 SVA and SCA, and C7s and T1s. This study showed that between the three groups, patients with nonspecific neck pain had smaller SCA, and among patients with NS-NP, women had more significant SCA. The smaller anteroposterior diameter of the thorax in women might explain this difference.

A novel rapid measurement method of cervical sagittal parameters based on the integrated inclinometer of a smartphone: a validity and reliability study

Objectives: A new method was introduced using a smartphone’s integrated inclinometer for rapid measurement of sagittal cervical parameters. The present study aims to compare the validity and reliability of the proposed method.Methods: We retrospectively reviewed 120 patients with cervical spondylosis treated at our hospital. The C0-2 Cobb angle, C2-7 Cobb angle, T1-slope (T1S), and neck tilt (NT) were selected as representative sagittal angles for this study. Two methods, the smartphone’s integrated inclinometer and picture archiving and communication system (PACS), were used to measure these four representative angles. Validity, reliability, and measurement times were recorded and compared.Results: The representative parameters (C0-2 Cobb angle, C2-7 Cobb angle, T1S, and NT), the ICC was 0.957 (0.939–0.970), 0.971 (0.958–0.979), 0.974 (0.963–0.982) and 0.949 (0.927–0.964) for validity respectively. For the aforementioned representative parameters, the ICC values were 0.972 (0.960–0.980), 0.979 (0.969–0.985), 0.972 (0.959–0.980), 0.942 (0.917–0.959) for intraobserver reliability respectively. For the representative parameters mentioned above, the ICC values were 0.947 (0.926–0.963), 0.964 (0.949–0.975), 0.956 (0.938-0.969), 0.916 (0.881–0.940) for interobserver reliability respectively. For the validity of the representative parameters mentioned above, the Bland-Altman plot displayed a mean difference of 0.2, 0.1, 0.1, and 0.4°with a 95% CI of 4.3, 4.5, 3.4, and 4.1°, respectively. The measurement by smartphone’s integrated inclinometer (46.31 ± 3.99 s) was significantly quicker than that by PACS (69.48 ± 3.25 s) according to independent-samples T test (p < 0.001).Conclusion: This novel smartphone measurement based on the integrated inclinometer is accurate and reliable for measuring cervical sagittal parameters rapidly and conveniently.

Prevalence and risk factors of occupational neck pain in Chinese male fighter pilots: a cross-sectional study based on questionnaire and cervical sagittal alignment.

Neck pain (NP) is a common musculoskeletal disorder among fighter pilots and has become a rising concern due to its detrimental impact on military combat effectiveness. The occurrence of NP is influenced by a variety of factors, but less attention has been paid to the association of NP with demographic, occupational, and cervical sagittal characteristics in this group. This study aimed to investigate the prevalence and risk factors of NP in Chinese male fighter pilots using a questionnaire and cervical sagittal measurements. Demographic and flight-related data, as well as musculoskeletal pain information, were gathered from Chinese male fighter pilots via a self-report questionnaire. Cervical sagittal parameters were measured and subtypes were classified using standardized lateral cervical radiographs. Differences in various factors between the case and control groups were analyzed using t-tests or chi-square tests. Binary logistic regressions were conducted to explore potential risk factors contributing to NP. Predictors were presented as crude odds ratios (CORs) and adjusted odds ratios (AORs), along with their respective 95% confidence intervals (CIs). A total of 185 male fighter pilots were included in this cross-sectional study. Among them, 96 (51.9%) reported experiencing NP within the previous 12 months. The multivariate regression analysis revealed that continuous flight training (AOR: 4.695, 95% CI: 2.226-9.901, p < 0.001), shoulder pain (AOR: 11.891, 95% CI: 4.671-30.268, p < 0.001), and low back pain (AOR: 3.452, 95% CI: 1.600-7.446, p = 0.002) were significantly associated with NP. The high 12-month prevalence of NP among Chinese male fighter pilots confirms the existence of this growing problem. Continuous flight training, shoulder pain, and low back pain have significant negative effects on pilots' neck health. Effective strategies are necessary to establish appropriate training schedules to reduce NP, and a more holistic perspective on musculoskeletal protection is needed. Given that spinal integrated balance and compensatory mechanisms may maintain individuals in a subclinical state, predicting the incidence of NP in fighter pilots based solely on sagittal characteristics in the cervical region may be inadequate.

Risk Factors for Prevertebral Soft Tissue Swelling Following Single-Level Anterior Cervical Spine Surgery.

Anterior cervical spine surgery (ACSS) is a common surgical procedure used to treat cervical spinal degenerative diseases. One of the complications associated with ACSS is prevertebral soft tissue swelling (PSTS), which can result in airway obstruction, dysphagia, and other adverse outcomes. This study aims to investigate the correlation between various cervical sagittal parameters and PSTS following single-level ACSS, as well as to identify independent risk factors for PSTS. A retrospective study conducted at a single institution. The study population included all patients who underwent single-level ACSS between January 2014 and December 2022. Patients with a history of cervical spine surgery or trauma were excluded from the study. The presence and severity of PSTS was assessed by reviewing pre- and postoperative imaging studies. The potential risk factors for PSTS that were examined include patient age, sex, body mass index, tobacco use, comorbidities, serum albumin levels, operative time, implant type, implanted level, and various cervical spine sagittal parameters. Multivariate linear regression analysis was performed to identify the independent risk factors for PSTS. A total of 62 consecutive patients who underwent single-level ACSS over a 8-year period at a single institution were enrolled in this study. Only preoperative segmental angle showed positive correlation with PSTS among various cervical spine sagittal parameters (r=0.36, p=0.005). Artificial disc replacement showed a negative correlation with PSTS (β=-0.38, p=0.002), whereas the use of demineralized bone matrix (DBM) had a positive impact on PSTS (β=0.33, p=0.009). We found that male sex, lower preoperative serum albumin, and implantation of upper cervical level (above C5) were independent predictors for PSTS after single-level ACSS (β=1.21; 95% confidence interval [CI], 0.27 to 2.15; p=0.012; β=-1.63; 95% CI, -2.91 to -0.34; p=0.014; β=1.44; 95% CI, 0.38 to 2.49; p=0.008, respectively). Our study identified male sex, lower preoperative serum albumin levels, and upper cervical level involvement as independent risk factors for PSTS after single-level ACSS. These findings can help clinicians monitor high-risk patients and take preventive measures to reduce complications. Further research with larger sample sizes and prospective designs is needed to validate these findings.

Does Posterior Cord Compression From the Ligamentum Flavum Influence Clinical Outcomes After Anterior Cervical Discectomy and Fusion?

Retrospective cohort study. To clarify whether outcomes of anterior cervical discectomy and fusion (ACDF) differ according to the presence of posterior cord compression from the ligamentum flavum (CCLF). Although ACDF effectively addresses anterior cord compression from disc material and bone spurs, it cannot address posterior compression. Whether ACDF could result in favorable outcomes when CCLF is present remains unclear. A total of 195 consecutive patients who underwent ACDF and were followed up for >2 years were included. CCLF was graded based on magnetic resonance imaging findings. Patients with CCLF grade 2 were classified as such, whereas patients with CCLF grades 0 to 1 were classified as the no-CCLF group. Patient characteristics, cervical sagittal parameters, neck pain visual analog scale, arm pain visual analog scale, and Japanese Orthopedic Association (JOA) score were assessed. Categorical variables were analyzed using a χ 2 test, whereas continuous variables were analyzed using the Student t test. Multivariable logistic regression analysis was performed to elucidate factors associated with JOA recovery rates of >50%. One hundred sixty-seven patients (85.6%) were included in the no-CCLF group, whereas the remaining 28 patients (14.4%) were included in the CCLF group. Among patients in the CCLF group, 14 patients (50.0%) achieved clinical improvement. JOA score significantly improved in the no-CCLF group after the operation ( P < 0.001), whereas improvement was not appreciated in the CCLF group ( P = 0.642). JOA scores at 3 months ( P = 0.037) and 2 years ( P = 0.001) postoperatively were significantly higher in the no-CCLF group. Furthermore, the JOA recovery rate at 2 years after surgery was significantly higher in the no-CCLF group ( P = 0.042). Logistic regression demonstrated that CCLF was significantly associated with a JOA recovery rate of >50% at 2 years after surgery (odds ratio: 2.719; 95% CI: 1.12, 6.60). ACDF performed for patients with CCLF grade 2 showed inferior JOA score improvement compared with those with CCLF grade 0 or 1. ACDF cannot remove posterior compressive structures, which limits its utility when ligamentum flavum significantly contributes to cord compression.

Can C7 Slope Accurately Substitute for an Invisible T1 Slope According to Age and Cervical Morphology in Cervical Lateral Radiographs?

A retrospective radiologic study. To identify age-associated changes in T1 slope (T1S) and C7 slope (C7S), as well as the difference between T1S and C7S (△, which was defined as T1S minus C7S) and to explore the cervical morphology that C7S can be the most accurate alternative for the invisible T1S. 625 asymptomatic Chinese volunteers received cervical lateral radiographs from August 2021 to May 2022. Occipito-C2 angle (O-C2), C2-7 angle (C2-7), cranial arch, caudal arch, C7S, and T1S were examined. Thereafter, the △ was established. The correlations among T1S, C7S, △ and other cervical sagittal parameters, and between age and other cervical sagittal parameters were evaluated with the Pearson correlation coefficient analysis. Then, analysis of variance (ANOVA) was conducted to compare variations in cervical sagittal parameters among volunteers aged 40 to 59years, 60 to 64years, 65 to 69years, 70 to 74years, and ≥75years of age, and among volunteers with 1 lordotic morphology, 2 lordotic morphology, straight morphology, kyphotic morphology, 1 sigmoid morphology, and 2 sigmoid morphology. Linear regression modeling of the correlation between C7S and T1S in various cervical alignment patterns was then established. △ had the strongest correlation with caudal arch (r = .646), and weakest correlation with cranial arch (r = -.082). Age was significantly correlated with T1S (r = .250), C7S (r = .244), and △ (r = .112). Among them, △ was stable until 74years after which it showed an elevation from 3.3° in the group 70-74years to 4.1° in the group over 75years. Moreover, there was marked variation between T1S and C7S at 1 lordotic, 2 lordotic, straight and 2 sigmoid alignment patterns, but no difference was seen between T1S and C7S at kyphotic and 1 sigmoid alignment patterns. There was a progressive increase in T1S, C7S, and △ with age. Linear regression equations for accurate prediction of T1S were developed based on the C7S in 1 lordotic, 2 lordotic, straight and 2 sigmoid alignment patterns. C7S may be a reliable proxy for T1S in kyphotic and 1 sigmoid alignment patterns.

Do Cervical Parameters Increase the Risk of Thoracic Spinal Stenosis in Patients with Cervical Spinal Stenosis?

The diagnosis and treatment of tandem stenosis have been widely discussed. However, studies on concurrent cervical and thoracic spinal stenosis are rare in the literature. This study was aimed to investigate the risk factors for thoracic spinal stenosis (TSS) in patients with cervical spinal stenosis (CSS). This retrospective cohort study assessed the risk factors for TSS in 162 patients who were diagnosed with CSS. Patients were divided into TSS (n=45) and non-TSS (n=117) groups. We retrospectively analyzed clinical characteristics and radiographic parameters, including age, gender, body mass index, ossification of the cervical posterior longitudinal ligament (OPLLc), hypertrophy of cervical ligamentum flavum (HLFc), cervical stenosis segments, and cervical sagittal parameters. Cervical sagittal parameters were measured on T2-weighted magnetic resonance imaging (MRI), including C2-7 Cobb angle (Cobb), cervical tilt (CT), T1 slope (T1S), thoracic inlet angle (TIA), C2-C7 sagittal vertical axis (C2-C7 SVA) and cervical curvature. Two groups showed significant differences in OPLLc, HLFc, cervical stenosis segments, and TIA. The receiver operating characteristic curves (ROC) demonstrated that the optimal threshold for TIA was 68.25. In multivariate logistic regression analysis, OPLLc (OR=4.403,95% CI=1.782-10.880,P=0.001), HLFc (OR=4.849,95% CI=1.995-11.782,P<0.001) and TIA>68.25 ° (OR=2.555,95%CI=1.044-6.251,p=0.040) were independent risk factors for TSS. Moreover, the multi-index ROC curve demonstrated that the area under the curve for predicted probability was 0.799 (p<0.001). Routine thoracic MRI assessment is strongly recommended in CSS patients with OPLLc, HLFc, and enlarged TIA to screen for neglected but vital thoracic disease.

The Significance of Odontoid Incidence in Patients With Cervical Spondylotic Myelopathy.

Observational study. To analyze the cervical sagittal parameters for standing Digital radiography (DR) and supine Magnetic resonance imaging (MRI), and to further clarify the relationship between odontoid incidence (OI) and cervical spondylotic myelopathy (CSM). 52 CSM patients aged 54.46 ± 2.89years underwent both standing DR and supine MRI scans of cervical spine between November 2021 and November 2022. OI, odontoid tilt (OT), C2 slope (C2S), T1 slope (T1S), C0-2 angle, C2-7 angle (cervical lordosis [CL]), and T1S-CL were measured in both DR and MRI images using Surgimap (Version 2.3.2.1). Pearson correlation and linear regression were used to compare these parameters between the two modalities. Cervical sagittal parameters, including OI, OT, C2S, C0-2 angle, T1S, C2-7 angle (CL) and T1S-CL, showed no significant differences in the measurements between the two modalities. Based on the DR images, OI was related to OT (r = .386, P < .01), C2S (r = .505, P < .01), CL (r = -.412, P < .01), and T1S-CL (r = .320, P < .05), and OI was matched with CL (r2 = .170) and T1S-CL (r2 = .102). Based on MRI images, OI was related to OT (r = .433, P < .01), C2S (r = .516, P < .01), CL (r = -.355, P < .01), and T1S-CL (r = .271, P < .05), and OI matched with C2-7 (r2 = .126) and T1S-CL (r2 = .073). OI is an independent parameter related to cervical anatomy and its measurement is unaffected by external factors. In patients with CSM, odontoid parameters may effectively describe the sagittal alignment of the cervical spine on DR and MRI images.

Cervical Sagittal Alignment and Balance Associated With Aging Chinese Adults: A Radiographic Analysis.

This was a retrospective cohort radiographic study. To determine the age- and gender-related normative values and correlation of cervical sagittal parameters in asymptomatic Chinese adults, and to explore the changes and compensating mechanisms across different age groups. The asymptomatic subjects were divided into 6 groups according to age and then one-way analysis of variance was used to compare the multiple sets of cervical sagittal parameters among the different age groups. Independent t-tests were performed to compare the sagittal parameters among different gender and different cervical spine alignments. Relationships between each parameter were tested by Pearson's correlation. Linear regression analysis based on T1 slope (T1S) and C2 slope (C2S) was used to provide an equation to predict normal cervical alignment. Mean values of each cervical sagittal parameter were presented based on age and gender. There were positive correlations between age and cervical lordosis (CL) (r = -.278, P < .001), T1S (r = .271, P < .001), cervical sagittal vertical axis (cSVA) (r = .218, P < .001), C2-C4 Cobb angle (r = -.283, P < .001), horacic inlet angle (TIA) (r = .443, P < .001), and neck tilt (NT) (r = .354, P < .001). Older groups (aged >50 years) had greater T1 Slope, C2S, and TIA. The C2-C4 Cobb angle maintained a steadily increasing trend and significantly increased in the older adult groups (P < .05), while the C5-C7 Cobb angle was relatively constant. Mean values of parameters were larger in males (P > .05). Linear regression analysis indicated a strong association between T1S and CL (R2 = .551, standard error 1.16°), T1S and C5-7 (R2 = .372; P < .001), and C2S and C2-4 (R2 = .309; P < .001). Normative values of cervical sagittal parameters vary by age and sex. The CL, cSVA, and T1S, C2-4 Cobb angle changed with increasing age, and it can influence the recruitment of compensation mechanism. Normative CL of Chinese adults was predicted by the equation CL = T1S-14.7° ± 1.2°, which could serve as a reference when planning for cervical surgery.

Description of age-related changes in cervical sagittal alignment based on pelvic incidence classification in asymptomatic Chinese population.

To investigate the pelvic incidence (PI)- and age-related cervical alignment changes of Chinese healthy population. Six hundred and twenty-five asymptomatic adult subjects, who underwent the standing whole spinal radiograph, were recruited in this work. The sagittal parameters were measured, including Occipito-C2 angle (O-C2), C2-7 angle (C2-7), cranial arch, caudal arch, T1-slope (T1S), C2-7 sagittal vertical axis (C2-7 SVA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), PI, and sagittal vertical axis (SVA). All subjects were stratified into 5 age groups, namely 40-59years, 60-64years, 65-69years, 70-74years, and 75years and above, with each age group further divided into 2 subgroups based on PI (deeming PI < 50° as low PI, and PI ≥ 50° as high PI). The correlations between PI or age, and other sagittal parameters were assessed. The age-related changes of sagittal parameters in each PI subgroup were also assessed, followed by one-way analysis of variance analysis for change comparison between age groups. The average cervical sagittal parameters were as below: 18.2 ± 6.8° for O-C2, 10.4 ± 10.2° for C2-7, 3.9 ± 7.5° for cranial arch, 6.5 ± 7.1° for caudal arch, 23.6 ± 7.3° for T1S, and 21.0 ± 9.7mm for C2-7 SVA. There was no obvious difference observed between PI and cervical sagittal parameters, excepting for caudal arch. While, C2-7, cranial arch, caudal arch, T1S, and C2-7 SVA increased remarkably with the age. Thereof, C2-7 exhibited great increases at the age of 60-64years and 70-74years, respectively, cranial arch increased notably at 60-64years of age, and caudal arch developed obviously at 70-74years of age, regardless of PI. This study showed the PI- and age-related cervical alignment changes of Chinese healthy population. Based on the classification in our study, high or low PI apparently did not correlate with the occurrence of cervical degenerative disease.

Comparison of three methods for measuring C0-1 angles and C0-2 angles

BackgroundThe mutual compensatory relationship between the upper cervical sagittal alignment and the lower cervical sagittal alignment has been repeatedly reported. However, the evaluation of the upper cervical sagittal parameters are varied in previous studies. This retrospective study was performed to compare three methods for measuring the upper cervical sagittal parameters.MethodsA total of 263 individuals with standing neutral lateral cervical radiographs were included in this study. The Frankfort horizontal line (FHL), foramen magnum line (FML), and McGregor line (ML) were separately used as the reference lines for measuring the C0-1 angle and C0-2 angle. Intraclass correlation (ICC) values were used to compare the consistency and repeatability of the three methods. Pearson’s correlation analysis was used to analyze the correlation between the sagittal parameters of the upper and lower cervical spine.ResultsThe interobserver and intraobserver ICC values obtained from using the ML to measure the C0-1 angle and C0-2 angle were both higher than those obtained from using the FML or FHL. The C0-1 angle and C0-2 angle measured by the three methods were negatively correlated with the C2-7 angle. The upper sagittal parameters measured by the FHL were the most correlated with the C2-7 angle. The correlation between the C0-1 angle measured by the three methods and the C0-2 angle measured with the FHL or ML and the C2-7 angle increased with aging.ConclusionUse of the ML to measure the C0-1 angle and C0-2 angle has higher reliability. Use of the FHL to measure the sagittal alignment of the upper cervical spine is more suitable for evaluating the compensation mechanism between the upper and the lower cervical spine.

Predictive Effect of Cervical Sagittal Parameters and Corresponding Segmental Paravertebral Muscle Degeneration on the Occurrence of Cervical Kyphosis Following Cervical Laminoplasty

Cervical sagittal parameters and paravertebral muscle degeneration are important factors for the occurrence of cervical spondylotic myelopathy. However, the relationship between the 2 risk factors and cervical kyphosis following cervical laminoplasty remains unknown. A total of 130 patients undergoing cervical laminoplasty were enrolled from July 2018 to July 2020 and were followed up for at least 24months. Clinical recovery was recorded, including the Japanese Orthopedic Association, neck disability index and visual analog scale scores. Radiographic sagittal parameters were measured on cervical lateral radiographs: T1 slope (T1S), C2-C7 Cobb lordotic angle (CLA), C2-C7 sagittal vertical axis, O-C2 angle, and T1S-CLA. The magnetic resonance imaging (MRI) parameters of the paraspinal muscles were also measured, including cross-sectional area and fat infiltration (FI). The patients were divided into a kyphosis group and a lordosis group based on the last follow-up results of CLA. Multivariate logistic analysis was performed to analyze risk factors for kyphosis following laminoplasty. Thirty-two patients were assigned to the kyphosis group and 98 were assigned to the lordosis group. Patient baseline and surgical information in the 2 groups showed no statistically significant difference. In the comparison of clinical recovery, patients with kyphosis showed a lower Japanese Orthopedic Association recovery rate than the lordosis group. For the radiographic parameters and muscle condition comparison, CLA, T1S-CLA, and FI were the most significant parameters. The logistic regression revealed that T1S-CLA and FI were the most important variables that predicted kyphosis. We concluded that FI remarkably differed in the paraspinal muscles in the 2 groups. Multivariate logistic regression demonstrated that T1S-CLA and FI significantly influenced the process of kyphosis after cervical laminoplasty.

Correlation and reliability of cervical sagittal alignment parameters between plain radiographs and multipositional MRI images.

A retrospective study. To assess the validity and reliability of cervical sagittal alignment parameters from multipositional magnetic resonance imaging (MRI) and dynamic cervical radiography. Hospital in Suzhou, China. Patients who underwent both multipositional MRI and dynamic plain radiography of the cervical spine within a 2-week interval between January 2013 and October 2021 were retrospectively enrolled in this study. The C2-7 angle, C2-7 cervical sagittal vertical axis (C2-7 SVA), T1 slope (T1S), cervical tilt, cranial tilt, and K-line tilt were measured in three different positions (neutral, flexion, and extension) with multipositional MRI and dynamic radiography. Inter- and intraobserver reliabilities were assessed by intraclass correlation coefficients (ICCs). Pearson correlation coefficients were used for statistical analyses. A total of 65 (30 males and 35 females) patients with a mean age of 53.4 years (range 23-69 years) were retrospectively enrolled in this study. Significant positive correlations were noted regarding all parameters between the plain radiographs and multipositional MRI images. Inter- and intraobserver reliabilities were excellent for all cervical sagittal alignment parameters measured in the two imaging modalities. All cervical sagittal parameters had significant positive correlations with those from multipositional MRI in all three positions (p < 0.05). Pearson correlation coefficients demonstrated moderate and strong correlations between the two examinations. Cervical sagittal alignment parameters measured on multipositional MRI could reliably substitute for those measured on plain radiographs. Multipositional MRI is a valuable, radiation-free alternative for diagnostic evaluation in degenerative cervical diseases.

Axial superior facet slope may determine anterior or posterior atlantoaxial displacement secondary to os odontoideum and compensatory mechanisms of the atlantooccipital joint and subaxial cervical spine

ObjectiveTo introduce novel parameters in determining directions of os odontoideum (OO) with atlantoaxial displacement (AAD) and compensations of cervical sagittal alignment after displacement.MethodsAnalysis was performed on 96 cases receiving surgeries for upper cervical myelopathy caused by OO with AAD from 2011 to 2021. Twenty-four patients were included in the OO group and divided into the OO-anterior displacement (AD) group and the OO-posterior displacement (PD) group by displacement. Seventy-two patients were included as the control (Ctrl) group and divided into Ctrl-positive (Ctrl-P) group and Ctrl-negative (Ctrl-N) group by axial superior facet slope (ASFS) in a neutral position. ASFS, the sum of C2 slope (C2S) and axial superior facet endplate angle (ASFEA), was measured and calculated by combining cervical supine CT with standing X-ray. Cervical sagittal parameters were measured to analyse the atlantoaxial facet and compensations after AAD.ResultsAtlas inferior facet angle (AIFA), ASFS, and ASFEA in Ctrl-P significantly differed from OO-AD.C0-C1, C1-C2, C0-C2, C2-C7, C2-C7 SVA, and C2S in Ctrl-P significant differed from the OO-AD group. C2-C7 SVA and C2S in Ctrl-N significantly were smaller than the OO-PD group. C1-C2 correlated with C0-C1 and C2-C7 negatively in the OO group. Slight kyphosis of C1-C2 in OO-AD was compared with lordosis of C1-C2 in Ctrl-P, inducing increased extension of C0-C1 and C2-C7. Mildly increased lordosis of C1-C2 in OO-PD was compared with C1-C2 in Ctrl-N, triggering augmented flexion of C0-C1 and C2-C7.ConclusionASFS was vital in determining directions of OO with AAD and explaining compensations. ASFS and ASFEA could provide pre- and intraoperative guidelines.Key Points• ASFS may determine the directions and compensatory mechanisms of AAD secondary to OO.• ASFS could be achieved by the sum of ASFEA and C2S.

Age-related changes in cervical sagittal alignment: based on 625 Chinese asymptomatic subjects.

This work aimed to provide a comprehensive description of cervical alignment including cranial arch and caudal arch according to age, thus offering a reference database for cervical deformity treatment. Total 150 males and 475 females aged at 48-88 were enrolled from August 2021 to May 2022. Radiographic parameters were measured, including Occipito-C2 angle (O-C2), C2-7 angle (C2-7), cranial arch, caudal arch, T1-slope (T1s), and C2-7 sagittal vertical axis (C2-7 SVA). Pearson correlation coefficient was employed in analyzing associations among sagittal parameters and between age and each parameter. Five groups were set according to different age stages, namely group with age 40-59 (N = 77), group with age 60-64 (N = 189), group with age 65-69 (N = 214), group with age 70-74 (N = 97), and group with age exceeding 75 (N = 48). An analysis of variance (ANOVA) test was applied to compare multi-sets of cervical sagittal parameters (CSPs). Chi-square test or Fisher's exact test was used in assessing the relationships of various cervical alignment patterns with age groups. T1s exhibited the strongest correlation with C2-7 (r = 0.655) and caudal arch (r = 0.561), and moderately correlated with cranial arch (r = 0.355). The positive correlations between age and C2-7 angle (r = 0.189, P < 0.001), cranial arch (r = 0.150, P < 0.001), caudal arch (r = 0.112, P = 0.005), T1s (r = 0.250, P < 0.001), as well as C2-7 SVA (r = 0.090, P = 0.024) were observed. Moreover, two progressive growths of C2-7 were shown after 60-64 and 70-74years old, respectively. Thereof, cranial arch increased greatly after the age of 60-64, followed by a relative stability in the degeneration. The notable growth of caudal arch was observed after the age of 70-74, and the growth remained stable when exceeding the age of 75. The difference between cervical alignment patterns and age groups was obvious (Fisher's exact test P < 0.001). This work explored in detail the normal reference values of cervical sagittal alignment including cranial arch and caudal arch under different age groups. Age-related changes in cervical alignment depended on the increase in the cranial and caudal arches in different proportions with age.

Extension of decompression to C2 doesn’t affect the spinal sagittal parameters compared with standard open-door laminoplasty

We modified and extended laminoplasty to the upper cervical spine on patients with canal stenosis associated with upper cervical spinal ossified lesions. However, whether the extended decompression range of laminoplasty can cause further effects on cervical stability is rarely studied at present. A retrospective study to analyze the relationship between the surgical levels and cervical sagittal parameters effects was performed in patients with cervical spondylosis myelopathy who had undergone posterior cervical expansive open-door laminoplasty with/without extending to C2. In total, 64 patients were divided into 2 groups according to the surgical levels. Radiologic outcomes of occipito-cervical angle (C0-2 Cobb angle), CL C27 Cobb angle, cervical sagittal vertical alignment, T1-Slope (T1S), T1S minus CL (T1S-CL), spino-cranial angle and center of the sella turcica-C7 SVA (St-SVA) were evaluated on lateral X-rays of the cervical spine at pre-operation, post-operation, and 2-year follow-up. The patient's health-related quality of life was obtained including neck disability index, Japanese orthopaedic association scores, and visual analog scale. Changes in sagittal parameters were observed in both groups after surgery. T1S, cervical sagittal vertical alignment, and T1S-CL significantly increased and CL decreased in 2 groups of patients postoperative. After a 2-year follow-up period, the C0-2 Cobb angle was found to increase compared to preoperative records. In addition, there were no significant differences in spino-cranial angle and st-SVA between preoperative and 2 years follow-up measurements. Health-related quality of life was improved in both groups and was not significantly different. Herein, the parameters indicated a tilting forward of the lower cervical spine and a more lordotic upper cervical spine to maintain a horizontal gaze in patients. However, C2 to 7 laminoplasty was performed to achieve satisfactory clinical results without significantly changing the spinal sagittal parameters.

Radiological features of degenerative cervical kyphosis and relationship between sagittal parameters

To investigate the radiological features of degenerative cervical kyphosis (DCK) and the relationship between cervical sagittal parameters. The quality of life scores and imaging data of 89 patients with DCK treated between February 2019 and February 2022 were retrospectively analysed. There were 47 males and 42 females, with an average age of 48.4 years (range, 25-81 years). Quality of life scores included visual analogue scale (VAS) score and neck disability index (NDI). The imaging data included C 0-C 2 angle, C 2-C 7 angle, C 3-C 7 inclination of zygapophyseal joints, C 7 slope (C 7S), cervical sagittal vertical axis (cSVA), kyphosis range, and kyphosis focal. The patients were grouped by gender, and the differences of the above parameters between the two groups were compared. Pearson correlation was used to analyze the relationship between age, quality of life scores, and cervical sagittal parameters, and the relationship between cervical sagittal parameters. The preoperative VAS score was 0-9 (mean, 4.3); NDI was 16%-44% (mean, 30.0%). There was no significant difference in VAS score and NDI between male and female groups ( P>0.05). The kyphosis range of cervical spines was C 3-5 in 3 cases, C 3-6 in 41 cases, C 3-7 in 30 cases, C 4-6 in 4 cases, C 4-7 in 10 cases, C 5-7 in 1 case, and the kyphosis focal was mostly located between C 4-C 5 (78/89, 87.64%). The C 3-C 7 inclination of zygapophyseal joints were (60.25±5.56)°, (55.42±5.77)°, (53.03±6.33)°, (58.39±7.27)°, and (64.70±6.40)°, respectively. The C 0-C 2 angle, C 2-C 7 angle, C 7S, and cSVA were (-23.81±6.74)°, (10.15±2.94)°, (15.31±4.59)°, and (2.37±1.19) mm, respectively. The C 7S and cSVA of males were significantly larger than females ( P<0.05), with no significant difference in other parameters between male and female groups ( P>0.05). VAS score and NDI were negatively correlated with C 0-C 2 angle ( P<0.05), and positively correlated with C 2-C 7 angle and cSVA ( P<0.05); VAS score was negatively correlated with C 7S ( P<0.05). Except VAS, NDI and all cervical sagittal parameters were affected by age. Age was positively correlated with NDI, C 7S, and cSVA ( P<0.05), and negatively correlated with C 0-C 2 angle and C 2-C 7 angle ( P<0.05). The correlation analysis of cervical sagittal parameters showed that C 0-C 2 angle was negatively correlated with C 2-C 7 angle and cSVA ( P<0.05); C 7S was negatively correlated with C 2-C 7 angle ( P<0.05) and positively correlated with cSVA ( P<0.05). There was no correlation among other parameters ( P>0.05). The inclination of zygapophyseal joints of cervical spines of DCK patients is U-shaped in the kyphosis range, and the inclination at the kyphosis focal is the smallest. When cervical degenerative kyphosis occurs, in addition to the interaction of sagittal parameters, age, gender, neck pain, and dysfunction will also affect the cervical sagittal balance. Furthermore, cervical curvature and morphological changes are not purely local problems.

Validity and reliability of a novel iPhone method to rapidly measure cervical sagittal parameters

We introduced a novel method based on the iPhone’s intrinsic photo edit function to measure sagittal parameters of the cervical spine. This study aimed to assess the validity of this new method compared with the picture archiving and communication system (PACS) method (the gold standard) and to test the reliability of this novel technique. One hundred consecutive patients admitted to our hospital diagnosed with cervical spondylotic myelopathy or cervical spondylotic radiculopathy were retrospectively reviewed. Four angles, including the C0-2 Cobb angle, C2-7 Cobb angle, T1S and neck tilt (NT), were assessed by iPhone and PACS. The validity and reliability were evaluated, and the time taken by both methods was compared. The ICCs of the validity of the C0-2 Cobb angle, C2-7 Cobb angle, T1S and NT were 0.960, 0.976, 0.980 and 0.946, respectively. The ICCs of the intraobserver reliability of the C0-2 Cobb angle, C2-7 Cobb angle, T1S and NT were 0.966, 0.983, 0.971 and 0.951, respectively. The ICCs of the interobserver reliability of the C0-2 Cobb angle, C2-7 Cobb angle, T1S and NT were 0.953, 0.972, 0.957 and 0.929, respectively. The Bland‒Altman plot of validity of the four angles revealed mean differences of 0.3, 0.2, 0.1, and 0.1 degrees with 95% CIs of 4.1, 4.1, 2.9, and 4.3 degrees, respectively. The iPhone measurement time (58.55 ± 4.17 s) was significantly less than that by the PACS (70.40 ± 2.92 s) when compared by the independent-samples T test (P < 0.001). This novel method using the iPhone’s intrinsic photo edit function is accurate, reliable, fast and convenient when measuring cervical sagittal parameters.

Realistic long-term dysphagia rates after anterior cervical discectomy with fusion: is there a correlation with postoperative sagittal alignment and lordosis at a minimum 2-year follow-up?

Postoperative dysphagia after anterior cervical discectomy and fusion (ACDF) has many contributing factors, and long-term data are sparse. The authors evaluated dysphagia after ACDF based on levels fused and cervical sagittal parameters. Patients who underwent ACDF between 2009 and 2018 at the University of California, San Francisco (UCSF), were retrospectively studied. Dysphagia was evaluated preoperatively, immediately postoperatively, and at last follow-up using the UCSF dysphagia score. Dysphagia was categorized as normal (level 7), mild (levels 5 and 6), moderate (levels 3 and 4), and severe (levels 1 and 2). The UCSF mild dysphagia score was further classified as "minimal dysphagia," while moderate and severe dysphagia were classified as "significant dysphagia." "Any dysphagia" included any dysphagia, regardless of grade. Cervical sagittal parameters were measured preoperatively, immediately postoperatively, and at last follow-up. A total of 131 patients met inclusion criteria. The mean follow-up was 43.89 (24-142) months. Seventy-eight patients (59.5%) reported dysphagia immediately postoperatively, and 44 patients (33.6%) reported some dysphagia at last follow-up (p < 0.001). The rates of moderate dysphagia were 13.0% immediately postoperatively and 1.5% at the last follow-up (p < 0.001). Twenty-two patients (16.8%) had significant dysphagia immediately postoperatively, and 2 patients (1.5%) had significant dysphagia at last follow-up (p < 0.001). Patients with immediate postoperative dysphagia had less C2-7 preoperative lordosis (-9.35°) compared with patients without (-14.15°, p = 0.029), but there was no association between C2-7 lordosis and dysphagia at last follow-up (p = 0.232). The prevalence rates of immediate postoperative dysphagia and long-term dysphagia were 87.5% and 58.3% in ≥ 3-level ACDF; 64.0% and 40.0% in 2-level ACDF; and 43.9% and 17.5% in 1-level ACDF, respectively (p < 0.001). The realistic incidence of any dysphagia after ACDF was 59.5% immediately postoperatively and 33.6% at the minimum 2-year follow-up, higher than previously published rates. However, most dysphagia was not severe. The number of fused levels was the most important risk factor for long-term dysphagia, but not for immediate postoperative dysphagia. Loss of preoperative C2-7 lordosis was associated with immediate postoperative dysphagia, but not long-term dysphagia. ACDF segmental lordosis and cervical sagittal vertical axis were not associated with long-term dysphagia in ACDF.

Preliminary Results of Instantaneous Centre of Rotation Change after Thoracic Instrumentation in Adolescent Idiopathic Scoliosis Patients.

The instantaneous centre of rotation (ICR) is the centre of motion with zero velocity where a rigid body moves in a particular plane. ICR, as a dynamic measurement, gives more accurate results in terms of quality and quantity of the vertebral motions compared to range of motion (ROM). We aimed to determine the effect of thoracic instrumentation on cervical movement of adolescent idiopathic scoliosis (AIS) patients who had undergone thoracic level instrumentation by measuring pre-operative and post-operative ICR change in a pilot study. A total of 25 AIS patients were included in this study. C4-C5 and C6-C7 segmental ICR were determined by pre-operative and post-operative cervical flexion-extension radiographs. In addition, cervical sagittal parameters and global sagittal parameters were investigated. There was no statistically significant change in ICR location post-operatively in both x and y coordinates at C4-C5 segment (p: 0.326 and p: 0.946, respectively) and C6-C7 segment (p: 0.209, p: 0.086, respectively). There was a positive correlation between LCL and C4-C5 ICR y coordinate (r: 0.481), but not with C6-C7 ICR y coordinate (r: -0.2, p: 0.398). T5-T12 kyphosis decreased (p: 0.002) and T1 pelvic angle (0.003), SVA (0.02) and sacral slope (0.049) increased significantly post-operatively. T1S was correlated with LCL (r: 0.595, p: 0.002), T5-T12 kyphosis (r: 0.423, p: 0.035), SVA (r: 0.658, p<0.001) and C2-C7 SVA (r: 0.416, p: 0.039). The ICR for cervical region was not changed post-operatively in AIS patients with thoracic instrumentation. There was no relationship found between the development of post-operative cervical kyphosis or lordosis and ICR, which represents the quality and quantity of intervertebral motion. The T1 vertebra plays a key role for cervical, thoracic, and global parameters interaction.