Is it possible to evaluate the parameters of cervical sagittal alignment on cervical computed tomographic scans?

Capturing the cervical spine shape: Angular measurements versus geometric morphometric methods

The cervical spine manifests a wide shape variation. However, the traditional methods to evaluate the cervical spine curve were never tested against its actual shape. The study's main aim was to determine whether the shape classification of the cervical spine, based on traditional angular measurements, coincides with each other and with the shape captured by the 2D landmark-based geometric morphometric method. The study's second aim was to reveal the associations between the cervical spine shape and the demographic parameters, the head's position, and the spine's sagittal balance. CT scans of the cervical spine of 163 individuals were evaluated to achieve these goals. The shape was assessed by measuring the C2-C7 Cobb angle (CA), the C2-C7 posterior tangent angle (PTA), the curvedness of the arch, and by a 2D landmark-based geometric morphometric method. The position of the head and the sagittal balance of the spine were evaluated by measuring the foramen magnum-C2 Cobb angle (FMCA) and the T1 slope angle (T1SA), respectively. Based on the size of the angle measured, each individual was classified into one of the three cervical 'shape groups' (lordotic, straight, and kyphotic). We found that cervical lordosis was the dominant shape regardless of the measuring methods utilized (46.6%-54.6%), followed by straight neck (28.2%-30.1%), and kyphosis (15.3%-25.2%); however, about a third of the 163 individuals were classified into a different shape group using the CA and PTA methods. The cervical spine angle was sex-independent and age-dependent. The T1SA was significantly correlated with CA and PTA (r = 0.640 and r = 0.585, respectively; p < 0.001). In conclusion, the cervical spine shape evaluation is method-dependent and varies with age.

Odontoid incidence: a constant cervical anatomical feature evident in standing plain radiographs and supine magnetic resonance images

OBJECTIVE

To assess whether there is a difference between measurements of odontoid incidence (OI) and other cervical sagittal parameters by X-ray radiography and those by supine magnetic resonance imaging (MRI).

METHODS

Standing X-ray and supine MRI images of 42 healthy subjects were retrospectively analyzed. Surgimap software was employed to measure cervical sagittal parameters including OI, odontoid tilt (OT), C2 slope (C2S), C0-2 angle, C2-7 angle, T1 slope (T1S) and T1S-cervical lordosis (CL). Paired samples t-test was applied to determine the difference between parameters measured by standing X-ray and those by supine MRI. In addition, the statistical correlation between the parameters were compared. The prediction of CL was performed and validated using the formula CL = 0.36 × OI - 0.67 × OT - 0.69 × T1S.

RESULTS

Significant correlations and differences were found between cervical sagittal parameters determined by X-ray and those by MRI. OI was verified to be a constant anatomic parameter and the formula CL = 0.36 × OI - 0.67 × OT - 0.69 × T1S can be used to predict CL in cervical sagittal parameters.

CONCLUSIONS

OI is verified as a constant anatomic parameter, demonstrating the necessity of a combined assessment of cervical sagittal balance by using standing X-ray and supine MRI. The formula CL = 0.36 × OI - 0.67 × OT - 0.69 × T1S can be applied to predict CL in cervical sagittal parameters.

Comparison of Cervical Sagittal Parameters Between Radiographs and Magnetic Resonance Images in Patients With Cervical Spondylotic Myelopathy

STUDY DESIGN

Observational study.

OBJECTIVE

As an important consideration of surgery, cervical sagittal balance is believed to be better assessed using standing radiograph than supine magnetic resonance imaging (MRI). However, few studies have researched this. Our study aimed to observe the correlations and differences in cervical sagittal parameters between radiograph and MRI in patients with cervical spondylotic myelopathy (CSM), and evaluate whether the change of position affects them.

METHODS

We analyzed 84 patients, measuring Cobb angle (CA), T1 slope (T1S), neck tilt (NT), and thoracic inlet angle (TIA). Inter- and intra-parameter analyses were performed to identify any difference between standing radiograph and supine MRI. Statistical correlations and differences between the parameters were compared.

RESULTS

There were excellent inter-observer agreement for each parameter (interclass correlation coefficient >.75), and significant differences were observed in each parameter between radiograph and magnetic resonance imaging (P < .05). Strong correlations were noted between the same parameters in radiograph and MRI. Cobb angle, T1S, and neck tilt were significantly correlated with thoracic inlet angle on both radiograph and MRI, and CA was significantly correlated with T1S on both radiograph and MRI (r: -1.0 to -.5 or .5 to 1.0).

CONCLUSION

Supine MRI obviously underestimated the value of CA, T1S, and TIA. Therefore, standing cervical radiographs should be obtained in CSM patients to assess and determine surgical strategy, not only supine MRI. Moreover, we observed that NT and TIA were not constant morphological parameters.

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

STUDY DESIGN

A retrospective radiologic study.

OBJECTIVES

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.

METHODS

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 59 years, 60 to 64 years, 65 to 69 years, 70 to 74 years, and ≥75 years 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.

RESULTS

△ 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 74 years after which it showed an elevation from 3.3° in the group 70-74 years to 4.1° in the group over 75 years. 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.

CONCLUSIONS

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.

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

STUDY DESIGN

A retrospective study.

OBJECTIVES

To assess the validity and reliability of cervical sagittal alignment parameters from multipositional magnetic resonance imaging (MRI) and dynamic cervical radiography.

SETTING

Hospital in Suzhou, China.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Analysis of Sagittal Thoracic Inlet Measures in Relation to Anterior Access to the Cervicothoracic Junction

STUDY DESIGN

Retrospective radiographic study.

OBJECTIVE

The aim of this study was to define the association between thoracic inlet measures in relation to anterior access to the cervicothoracic junction.

METHODS

Trauma CT scans in patients >16 years were analyzed. The projection angle (PA), defined as the angle subtended by a line along the superior endplate of the vertebral body and the line from the anterosuperior corner of the vertebral body to the manubrium, was measured at C7, T1 and T2; angles were positive if the projection was above the manubrium. Thoracic inlet angle (TIA), thoracic inlet distance (TID) and pelvic incidence (PI) were measured.

RESULTS

65 scans were assessed (33 males; mean age 47.7 years (s.d. 8.7)). The mean TIA 79.9° (s.d. 13.4°; range 52.6° - 112.2°), mean TID 66.1 mm (s.d. 6.6 mm) and mean PI was 50.5° (s.d. 10.2°). Mean values for the projection angles at C7, T1 and T2 were 24.2°, 7.6° and -8.3° respectively. PA were positive in 95% at C7, 73% at T1 and 30% at T2. PA at each level correlated significantly with age (mean r=-0.371; P = .015) and TIA (mean r=-0.916; P < .001) but neither TID nor PI. TIA correlated with age (r = 0.328; P = .008).

CONCLUSIONS

The projection angles of the CTJ vertebrae are influenced by thoracic inlet angle and a lesser degree age. Understanding sagittal spinal parameters in the CTJ can aid in planning surgical strategy and approach.

Changes in intervertebral sagittal alignment of the cervical spine from supine to upright

Cervical sagittal alignment is a critical component of successful surgical outcomes. Unrecognized differences in intervertebral alignment between supine and upright positions may affect clinical outcomes; however, these differences have not been quantified. Sixty-four patients scheduled to undergo one or two-level cervical arthrodesis for symptomatic pathology from C4-C5 to C6-C7, and forty-seven controls were recruited. Upright sagittal alignment was obtained through biplane radiographic imaging and measured using a validated process with accuracy better than 1° in rotation. Supine alignment was obtained from computed tomography scans. Coordinate systems used to measure supine and upright alignment were identical. Distances between adjacent bony endplates were measured to calculate disc height in each position. For both patients and controls, the C1-C2, C2-C3, and C3-C4 motion segments were in more lordosis when upright as compared with supine (all p < 0.001). However, the C4-C5, C5-C6, and C6-C7 motion segments were in less lordosis when upright as compared with supine (all p ≤ 0.004). There was an interaction between group and position at the C1-C2 (p = 0.002) and C2-C3 (p = 0.001) motion segments, with the controls demonstrating a greater increase in lordosis at both motion segments when moving from supine to upright. The results indicate that cervical motion segment alignment changes between supine and upright positioning, those changes differ among motion segments, and cervical pathology affects the magnitude of these changes. Clinical Significance: Surgeons should be mindful of the differences in alignment between supine and upright imaging and the implications they may have on clinical outcomes.

Does cervical curvature affect neurological outcome after incomplete spinal cord injury without radiographic abnormality (SCIWORA): 1-year follow-up

Background

At present, surgery is the primary clinical treatment for SCIWORA patients, but conservative treatment still plays an important role in patients with incomplete spinal cord injury. As an important index of cervical spine degeneration, cervical curvature has an impact on the prognosis of spinal cord injury patients. This paper studied the prognosis of conservatively treated patients with SCIWORA and the correlation between cervical curvature and neurological prognosis.

Methods

A retrospective study was conducted in all the patients with SCI admitted to the Third Affiliated Hospital of Hebei Medical University between January 2017 and June 2020. Data were recorded in 106 eligible patients, including sex, age, injury factors, Cobb angle, CCI, CSA, and ASIA motor and sensory scores. The Wilcoxon sign rank sum test was used to analyze the data postinjury and at the 1-year follow-up. Pearson correlation analysis was performed for the Cobb angle, CCI and CSA. Simple linear regression analysis and multiple linear regression analysis were performed for each group of variables.

Results

The Wilcoxon signed rank sum test confirmed that the Cobb angle, the CCI and the CSA of the patients were not significantly different at the 1-year follow-up when compared with the postinjury values, and the ASIA motor and sensory scores were significantly improved. The Pearson correlation analysis showed correlations among the Cobb angle, the CCI and the CSA. Simple linear regression analysis and multiple linear regression analysis showed that the nerve recovery rate was negatively correlated with age and was positively correlated with the Cobb angle.

Conclusion

Conservative treatment of incomplete SCIWORA can achieve a good prognosis. There is a clear correlation between the Cobb angle, CCI and CSA, and the Cobb angle, as an important influencing factor, needs to be considered. For SCIWORA patients undergoing nonsurgical treatment, improving cervical curvature is beneficial to the prognosis of patients. Age negatively affects the neurological prognosis.

Simulating upright cervical lordosis in the supine position

Cervical alignment or lordosis evolution is still attained by direct radiography in standing position because an ideal cervical curvature is essential to maintain a horizontal gaze with minimal energy consumption. However, upright cervical lordosis changes in supine position. Anterior fusion surgery and more sophisticated radiological examinations, such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), are performed in lying position. Therefore, if upright cervical alignment can be simulated in the supine position, true (upright) cervical lordosis can be demonstrated on CT and MRI and also a more proper anterior cervical fusion can be performed in operation with better surgical outcomes. Forty-nine (49) adult patients underwent radiological examinations, including upright cervi- cal radiography and three session of supine MRI in different positions. MRI was performed in (1) conventional neutral supine position, (2) supine posi- tion with a 5-cm-high pillow, and (3) supine position with a 10-cm-high pillow under the shoulders. MRI results were analyzed. Wilcoxon, Kolmogorov-Smir- nov, and Spearman correlation tests were used to analyze MRI the validity in compared with those of cervical radiography. Cervical lordosis (C2-C7 Cobb angle) of the radiography group was similar to that of supine MRI group using a 5-cm-high pillow, and they have a strong correlation. The T-1 slope from radiography group was similar to and correlated with that of supine MRI groups with both pillows. Cranial tilt measurements of radiography group were different but correlated with the MRI group using a 5-cm-high pillow. Simulating upright cervical lordosis in the supine position is possible by adding a 5-cm- high pillow under the shoulders of the patients. This simulation reduces the need for direct radiography. Anterior cervical fusion surgery performed in this position can provide better surgical results.

Differences in Demographic and Radiographic Characteristics between Patients with Visible and Invisible T1 Slopes on Lateral Cervical Radiographic Images

Introduction: The T1 slope is important for cervical surgical planning, and it may be invisible on radiographic images. The prevalence of T1 invisible cases and the differences in demographic and radiographic characteristics between patients whose T1 slopes are visible or invisible remains unexplored. Methods: This pilot study aimed to evaluate the differences in these characteristics between outpatients whose T1 slopes were visible or invisible on radiographic images. Patients (n = 60) who underwent cervical radiography, whose T1 slope was confirmed clearly, were divided into the visible (V) group and invisible (I) group. The following radiographic parameters were measured: (1) C2-7 sagittal vertical axis (SVA), (2) C2-7 angle in neutral, flexion, and extension positions. Results: Based on the T1 slope visibility, 46.7% of patients were included in group I. The I group had significantly larger C2-7 SVA than the V group for males (p < 0.05). The C2-7 SVA tended to be larger in the I group, without significant difference for females (p = 0.362). Discussion: The mean C2-7 angle in neutral and flexion positions was not significantly different between the V and I groups for either sex. The mean C2-7 angle in the extension position was greater in the V group. The T1 slope was invisible in males with high C2-7 SVA.

The Effect of Seat Back Inclination on Spinal Alignment in Automotive Seating Postures

Experimental studies have demonstrated a relationship between spinal injury severity and vertebral kinematics, influenced by the initial spinal alignment of automotive occupants. Spinal alignment has been considered one of the possible causes of gender differences in the risk of sustaining spinal injuries. To predict vertebral kinematics and investigate spinal injury mechanisms, including gender-related mechanisms, under different seat back inclinations, it is needed to investigate the effect of the seat back inclination on initial spinal alignment in automotive seating postures for both men and women. The purpose of this study was to investigate the effect of the seat back inclination on spinal alignments, comparing spinal alignments of automotive seating postures in the 20° and 25° seat back angle and standing and supine postures. The spinal columns of 11 female and 12 male volunteers in automotive seating, standing, and supine postures were scanned in an upright open magnetic resonance imaging system. Patterns of their spinal alignments were analyzed using Multidimensional Scaling presented in a distribution map. Spinal segmental angles (cervical curvature, T1 slope, total thoracic kyphosis, upper thoracic kyphosis, lower thoracic kyphosis, lumbar lordosis, and sacral slope) were also measured using the imaging data. In the maximum individual variances in spinal alignment, a relationship between the cervical and thoracic spinal alignment was found in multidimensional scaling analyses. Subjects with a more lordotic cervical spine had a pronounced kyphotic thoracic spine, whereas subjects with a straighter to kyphotic cervical spine had a less kyphotic thoracic spine. When categorizing spinal alignments into two groups based on the spinal segmental angle of cervical curvature, spinal alignments with a lordotic cervical spine showed significantly greater absolute average values of T1 slope, total thoracic kyphosis, and lower thoracic kyphosis for both the 20° and 25° seat back angles. For automotive seating postures, the gender difference in spinal alignment was almost straight cervical and less-kyphotic thoracic spine for the female subjects and lordotic cervical and more pronounced kyphotic thoracic spine for the male subjects. The most prominent influence of seatback inclination appeared in Total thoracic kyphosis, with increased angles for 25° seat back, 8.0° greater in spinal alignments with a lordotic cervical spine, 3.2° greater in spinal alignments with a kyphotic cervical spine. The difference in total thoracic kyphosis between the two seatback angles and between the seating posture with the 20° seat back angle and the standing posture was greater for spinal alignments with a lordotic cervical spine than for spinal alignments with a kyphotic cervical spine. The female subjects in this study had a tendency toward the kyphotic cervical spine. Some of the differences between average gender-specific spinal alignments may be explained by the findings observed in the differences between spinal alignments with a lordotic and kyphotic cervical spine.

Physiologic Cervical Alignment Change between Cervical Spine X-ray and Computed Tomography

Objective

The purpose of this study was to investigate the correlations among various radiological parameters used to determine cervical alignment from cervical spine radiographs (X-CS) and cervical spine computed tomography (CT-CS), both within and between modalities.

Methods

This study included 168 patients (≤60 years old) without a definite whole spine deformity who underwent CT-CS and X-CS. We measured occipital slope (O-s), C1 slope, C2 slope, C7 slope, sella turcica - C7 sagittal vertical axis (StC7-SVA), spinocranial angle, T1 slope, and C27-SVA. We calculated the O-C2 angle, O-C7 angle, and C2-7 angle from the measured parameters and conducted correlation analyses among multiple parameters.

Results

The intrinsic correlation features among multiple cervical parameters were very similar for both X-CS and CT-CS. The two SVA parameters (C27-SVA and StC7-SVA) were mainly influenced by the upper cervical slope parameters (r=|0.13–0.74|) rather than the lower slope cervical parameters (r=|0.08–0.13|). The correlation between X-CS and CT-CS for each radiological parameter was statistically significant (r=0.26–0.44) except for O-s (r=0.10) and StC7-SVA (r=0.11).

Conclusion

The correlation patterns within X-CS and CT-CS were very similar in this study. The correlation between X-ray and CT was statistically significant for most radiological parameters, and the correlation score increased when the horizontal gaze was consistently maintained. The lower cervical parameters were not statistically associated with translation-related parameters (C2-7 SVA and StC7-SVA). Therefore, the upper cervical segment may be a better predictor for determining head and neck translation.

Spino Cranial Angle and Degenerative Cervical Spondylolisthesis

OBJECTIVE

The purpose of our study was to analyze and compare the spino cranial angle (SCA) in patients with degenerative cervical spondylolisthesis (DCS) and asymptomatic controls and to determine whether SCA could help diagnose DCS.

METHODS

We enrolled 50 patients diagnosed with DCS (4.3%) from among 1168 patients and the same number of asymptomatic participants as the control group by using cervical radiographs. Both groups underwent cervical radiographs and computed tomography at the same time. Various sagittal parameters were measured on computed tomography in a standardized supine position and compared with the asymptomatic control group. The Spearman correlation coefficient was applied to test the correlation among the sagittal parameters in the DCS group. Multivariate logistic regression analysis and receiver operating characteristic curve analysis were performed to determine whether SCA could help predict DCS.

RESULTS

Fifty patients were enrolled in the DCS group, and 50 asymptomatic participants were included in the control group. The SCA was significantly lower for the DCS group than for the control group (76.84 ± 7.48 degrees vs. 82.47 ± 8.06 degrees, P < 0.001), and the T1 slope (T1s) was significantly greater for the DCS group than for the control group (27.29 ± 7.84 degrees vs. 22.28 ± 6.43 degrees, P = 0.001). Except for SCA and T1s, no other parameters showed significant differences. The SCA on the computed tomography scan was significantly correlated with the values of the T1s (r = -0.890, P < 0.001), cervical lordosis (r = -0.437, P = 0.002), C2-C7 sagittal vertical axis (r = 0.397, P = 0.004), and thoracic inlet angle (r = -0.565, P < 0.001). Multivariate logistic regression analysis and receiver operating characteristic curve analysis showed that both a lower SCA and a higher T1s could be risk factors for DCS, and an SCA of <79.1 degrees demonstrated significant diagnostic value for the detection of DCS.

CONCLUSIONS

Patients in the DCS group had a lower SCA and a higher T1s. Both a lower SCA and a higher T1s could be risk factors for DCS, and an SCA of <79.1 degrees demonstrated significant diagnostic value for the detection of DCS.

Correlation of supine MRI and standing radiographs for cervical sagittal balance in myelopathy patients: a cross-sectional study

PURPOSE

Cervical sagittal alignment is correlated with myelopathy severity and used by spinal surgeons for surgical planification. Magnetic resonance imaging (MRI) is the gold standard for the evaluation of cervical myelopathy but may not be for the assessment of cervical sagittal balance compared to X-rays. The objective of this study was to assess the correlation of cervical alignment between supine MRI and standing radiographs in patients with cervical spondylotic myelopathy (CSM).

METHODS

Cobb, Jackson and Harrison methods were used to measure cervical sagittal alignment on supine MRI and standing radiographs of CSM adults. Cervical alignment was divided based on Cobb angle values on lordotic (> 4°), kyphotic (< - 4°) and rectitude (- 4° to 4°). Correlations between radiographic and MRI measurements were determined. Intra- and interobserver reliability were assessed and MRI and X-Ray-measured angles were compared.

RESULTS

One hundred and thirty patients with CSM were reviewed. Correlations of cervical lordosis measures between radiographs and MRI were strong using the Cobb (0.65) and Jackson (0.63) methods, and moderate using the Harrison (0.37) method. Mean cervical lordosis angle was significantly lower on supine MRI compared to standing radiographs for all methods (Cobb 11.6 Rx vs. 9.2 MRI, Jackson 14.6 vs. 11.6, Harrison 23.5 vs. 19.9). Eighteen patients (15.4%) without lordosis on supine MRI presented lordosis on standing radiographs.

CONCLUSION

A substantial proportion of patients has sagittal alignment discrepancies between supine MRI and standing radiographs. Therefore, standing radiographs of the cervical spine should always be included in surgical planning of CSM patients.

[Relationship between O-EA angle and lower cervical curvature in patients with anterior atlantoaxial dislocation before and after occipitocervical fusion]

Objective

To investigate the relationship between O-EA angle and lower cervical curvature in patients with anterior atlantoaxial dislocation undergoing occipitocervical fusion, and to analyze the effect of O-EA angle on lower cervical curvature.

Methods

The clinical data of 61 patients with anterior atlantoaxial dislocation undergoing occipitocervical fusion who were admitted between April 2010 and July 2018 and met the selection criteria were retrospectively analyzed. There were 32 males and 29 females, with an age of 14-76 years (mean, 50.7 years). The fixed segment included 19 cases of C ₀-C ₂, 27 cases of C ₀-C ₃, 14 cases of C ₀-C ₄, and 1 case of C ₀-C ₅. The O-EA angle, C _2-7 Cobb angle, and T ₁ tilt angle were measured before operation and at last follow-up. According to the O-EA angle measured at last follow-up, the patients were divided into <95° group (group A), 95°-105° group (group B), and >105° group (group C), and compared the differences of gender, age, fixed segment (short segment was at C ₃ and above, long segment was beyond C ₃), and C _2-7 Cobb angle. Correlation analysis between the O-EA angle and C _2-7 Cobb angle before operation and at last follow-up, as well as the changes of O-EA angle and C _2-7 Cobb angle between before operation and at last follow-up were analyzed.

Results

All 61 patients were followed up 12-24 months, with an average of 22.4 months. There was no significant difference in O-EA angle, C _2-7 Cobb angle, and T ₁ tilt angle before operation and at last follow-up ( P>0.05). According to the last follow-up O-EA angle grouping, there were 14 cases in group A, 29 cases in group B, and 18 cases in group C. There was no significant difference in age, gender composition, and fixed segment composition among the three groups ( P>0.05); the differences in C _2-7 Cobb angles among the three groups were significant ( P<0.05), groups A, B, and C showed a gradually increasing trend. The O-EA angle was positively correlated with C _2-7 Cobb angle before operation and at last follow-up ( r=0.572, P=0.000; r=0.618, P=0.000); O-EA angle change at last follow-up was also positively correlated with C _2-7 Cobb change ( r=0.446, P=0.000).

Conclusion

The O-EA angle of patients with anterior atlantoaxial dislocation is positively correlated with C _2-7 Cobb angle. Too large O-EA angle should be avoided during occipitocervical fixation, otherwise it may accelerate the degeneration of the lower cervical spine.

Age-related Changes in T1 and C7 Slope and the Correlation Between Them in More Than 300 Asymptomatic Subjects

STUDY DESIGN

A cross-sectional analysis using T1 slope (T1S) and C7 slope (C7S) in asymptomatic individuals.

OBJECTIVE

The aim of this study was to identify normative values, ranges of motion (ROMs), age-related changes in T1S and C7S, and correlation between the two slopes.

SUMMARY OF BACKGROUND DATA

Few studies have reported age-related changes in the T1S and C7S angles. Additionally, studies investigating the effects of cervical position on these slopes are limited.

METHODS

A total of 388 asymptomatic subjects (162 males and 226 females) for whom T1S measurement was performed on radiographs were enrolled in the study. The T1S and C7S angles were measured using neutral radiography of the cervical spine. ROMs were assessed by measuring the difference in alignment in the neutral position, flexion, and extension.

RESULTS

The mean C7S and T1S angles were 19.6° (22.2° in males, 17.9° in females) and 24.0° (26.7° in men and 22.1° in women), respectively. The T1S angle was significantly greater than the C7S angle. Both the C7S and T1S angles significantly increased with age. The flexion ROM of C7S was higher than that of T1S, whereas no significant difference was detected between the extension ROMs of the two slopes. The flexion ROMs of the two slopes did not change, whereas the extension ROMs significantly increased with age. A significant positive correlation was observed between the C7S and T1S angles (r2 = 0.75).

CONCLUSION

The normative values and age-related changes in C7S and T1S were analyzed. Both the C7S and T1S angles increased with age. The C7S angle was strongly correlated with the T1S angle, suggesting that C7S can substitute T1S on radiographic images.Level of Evidence: 3.

Sagittal balance of the cervical spine: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to compare the cervical sagittal parameters between patients with cervical spine disorder and asymptomatic controls.

METHODS

Two independent authors systematically searched online databases including Pubmed, Scopus, Cochrane library, and Web of Science up to June 2020. Cervical sagittal balance parameters, such as T1 slope, cervical SVA (cSVA), and spine cranial angle (SCA), were compared between the cervical spine in healthy, symptomatic, and pre-operative participants. Where possible, we pooled data using random-effects meta-analysis, by CMA software. Heterogeneity and publication bias were assessed using the I-squared statistic and funnel plots, respectively.

RESULTS

A total of 102 studies, comprising 13,802 cases (52.7% female), were included in this meta-analysis. We used the Newcastle-Ottawa Scale (NOS) to evaluate the quality of studies included in this review. Funnel plot and Begg's test did not indicate obvious publication bias. The pooled analysis reveals that the mean (SD) values were: T1 slope (degree), 24.5 (0.98), 25.7 (0.99), 25.4 (0.34); cSVA (mm), 18.7 (1.76), 22.7 (0.66), 22.4 (0.68) for healthy population, symptomatic, and pre-operative assessment, respectively. The mean value of the SCA (degree) was 79.5 (3.55) and 75.6 (10.3) for healthy and symptomatic groups, respectively. Statistical differences were observed between the groups (all P values < 0.001).

CONCLUSION

The findings showed that the T1 slope and the cSVA were significantly lower among patients with cervical spine disorder compared to controls and higher for the SCA. Further well-conducted studies are needed to complement our findings.

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 significance of cervical sagittal alignment for nonrecovery after whiplash injury

BACKGROUND CONTEXT

Whiplash-associated disorder is a common cause of chronic neck pain. Several radiological cervical angular variables are suggested to have constitutional characteristics, that is, them being minimally influenced by body positioning. However, the association between these variables and pain conditions remains poorly understood. To our knowledge, no previous studies have investigated the association between constitutional angular variables and the outcome after whiplash trauma.

PURPOSE

Our objectives were (1) to study the inter-rater agreement of sagittal radiologic variables between 2 raters and (2) to investigate any association between these variables and self-perceived nonrecovery after whiplash injury.

STUDY DESIGN

Prospective cohort study.

PATIENT SAMPLE

Forty-six patients aged 16 to 70 years, attending an emergency department after a motor vehicle accident resulting in neck pain were recruited.

OUTCOME MEASURES

Self-perceived nonrecovery (yes/no) was the primary outcome measure. The secondary outcome measure was pain level on a numeric rating scale.

METHODS

The participants underwent computed tomography scans in a supine position. Sagittal alignment variables (T1 slope, neck tilt, thoracic inlet angle [TIA], and C2-C7 angle) on the computed tomography scans were measured by 2 independent raters. Inter-rater agreement was tested with a paired sample t test and Bland-Altman plots for each variable. The patients were followed up after 6 months.

RESULTS

No systematic differences for the assessed variables were found between the 2 raters. The overall nonrecovery rate was 28%. For the group with low neck tilt, the nonrecovery rate was 50% (95% CI: 36%-78%) and for the group with high neck tilt, 8% (95% CI: 3%-25%). The nonrecovery rate for the group low TIA was 50% (95% CI 29%-72%) and for those with high TIA 14% (95% CI 4%-26%). The associations remained significant after adjustments for possible confounders. The inter-rater analysis shows satisfactory agreement without proportional bias.

CONCLUSIONS

This study indicates the existence of an association between the constitutional sagittal alignment of the cervical spine and the outcome after whiplash injuries.

Factors predicting loss of cervical lordosis following cervical laminoplasty: A critical review

Background:

Laminoplasty is a method of posterior cervical decompression which indirectly decompresses the spinal column. Unfortunately, many patients undergoing laminoplasty develops postoperative loss of cervical lordosis (LCL) or kyphotic alignment of cervical spine even though they have sufficient preoperative lordosis which results in poor surgical outcome.

Objective:

We would like to highlight the relationship between various radiological parameters of cervical alignment and postoperative LCL in patients undergoing laminoplasty.

Methods:

We performed extensive literature search using PubMed, Google Scholar, and Web of Science for relevant articles that report factors affecting cervical alignment following laminoplasty.

Results:

On reviewing the literature, patients with high T1 slope have more lordotic alignment of cervical spine preoperatively. They also have more chances of LCL following laminoplasty. C2–C7 sagittal vertical axis (SVA) has no role in predicting LCL following laminoplasty though patients with low T1 slope (≤20°) and high C2–C7 SVA (>22 mm) had correction of kyphotic deformity following laminoplasty. C2–C7 lordosis, Neck Tilt, cervical range of motion, and thoracic kyphosis has no predictive value for LCL. Lower value of T1 slope (T1S-CL) and CL/T1S has more incidence of developing LCL following laminoplasty. The role of C2–C3 disc angle has not yet been evaluated in patients undergoing laminoplasty. Dynamic extension reserve determines the contraction reserve of SPMLC and lower dynamic extension reserve is associated with higher chances of LCL following laminoplasty.

Conclusions:

Cervical lordotic alignment is important in maintaining cervical sagittal balance which ultimately is responsible for global spinal sagittal balance and horizontal gaze. Among various radiological parameters, T1 Slope has been reported to be the most important factor affecting cervical alignment following laminoplasty.

Correlation between C7 slope and cervical lordosis in patients after expansive open-door laminoplasty

Purpose of the article: To investigate the correlation between C₇ slope and cervical lordosis in patients after expansive open-door laminoplasty (EOLP).Material and methods: We retrospectively analyzed 57 patients who underwent EOLP between June 2013 and January 2017 in the Department of Spinal Surgery of our hospital. The operation time, intraoperative blood loss and follow-up time were recorded. The C₇ slope, C_2-7 sagittal vertical axis, and C_2-7 Cobb angle were measured anteroposterior radiograph of the cervical spine preoperatively and postoperatively. All patients were divided into two groups according to the preoperative C₇ slope (C₇ slope ≤20° group and C₇ slope >20° group).Results: The amount of intraoperative bleeding was 220.2 ± 180.9ml, and the operation time was 143.4 ± 51.2min. The average follow-up time was 24.9 ± 10.3months (range12-48 months). The C_2-7 Cobb angle was 13.49 ± 10.46°at the final follow-up, which was significantly lower than that preoperatively (p = .026). But, The C₇ slope and C_2-7 sagittal vertical axis showed no significant difference between preoperatively and postoperatively. Preoperative and postoperative C₇ slope and C_2-7 Cobb angle were positively correlated to age and significant difference was observed. In the group of C₇ slope >20°, significant difference was observed in term of the change of the C_2-7 Cobb angle and C_2-7SVA postoperatively (p = .009 and p= .020). However, there was no statistically significant difference detected in these two parameters in the group of C₇ slope ≤20°.Conclusion: This study indicated that C₇ slope could be used as an indicator of the change in the curvature of the cervical spine after EOLP. The loss of cervical curvature after surgery was prone to occur when C₇ slope was greater than 20°, which should be noted in clinical practice.

Analysis of a radiographic parameter K-line tilt following adjacent two-level anterior cervical discectomy and fusion: a retrospective study

BACKGROUND

T1s, C2-7 lordosis, and C2-7 sagittal vertical axis (SVA) are the three most important sagittal parameters in the cervical spine. This study was conducted to investigate the relationships between classical sagittal alignment parameters and a new parameter, K-line tilt, and to study the impact of K-line tilt.

MATERIAL AND METHODS

A total of 72 patients who underwent adjacent two-level anterior cervical discectomy and fusion (ACDF) were retrospectively analyzed. Radiographic measurements included T1 slope (T1s), C2-7 lordosis, segment angle (SA), C2-7 SVA, and K-line tilt. The Neck Disability Index (NDI) scores were used to evaluate the clinical prognosis. Pearson correlation coefficients were calculated between radiographic measures. Linear regression analysis was used to analyze the relationship between follow-up K-line tilt and NDI.

RESULTS

ΔNDI was positively correlated with ΔT1s (r = 0.620, p < 0.05), ΔC2-7 SVA (r = 0.645, p < 0.05), and ΔK-line tilt (r = 0.702, p < 0.01); ΔK-line tilt was positively correlated with ΔT1s (r = 0.650, p < 0.05), ΔSA (r = 0.269, p < 0.05), and ΔC2-7 SVA (r = 0.293, p < 0.05); ΔT1s was positively correlated with ΔC2-7 lordosis (r = 0.428, p < 0.05), ΔSA (r = 0.631, p < 0.01), and ΔC2-7 SVA (r = 0.235, p < 0.05); ΔC2-7 lordosis was positively correlated with ΔSA (r = 0.666, p < 0.05) and negatively correlated with ΔC2-7 SVA (r = - 0.467, p < 0.01). The preoperative and postoperative K-line tilt values were statistically significant (p < 0.01), increasing from (7.50 ± 6.48)° to (9.95 ± 5.09)°. Preoperative NDI was positively correlated with preoperative C2-7 SVA (r = 0.639, p = 0.011) and K-line tilt (r = 0.516, p = 0.026); follow-up NDI was positively correlated with follow-up T1s (r = 0.664, p = 0.038), C2-7 SVA (r = 0.756, p = 0.004), and K-line tilt (r = 0.832, p = 0.006). The linear regression model showed that when the follow-up K-lint tilt was > 23.75°, NDI scores were > 25 (R² = 0.737, p = 0.000).

CONCLUSION

This study showed that the K-line tilt was strongly correlated with the C2-C7 SVA, indicating that the K-line tilt can be used as another cervical parameter to evaluate cervical alignment in adjacent two-level ACDF. K-line tilt is an important parameter similar to the classical parameter C2-C7 SVA. In particular, a K-line tilt greater than 23.75 corresponded to a worse clinical prognosis, which was defined as an NDI score greater than 25.

Can C7 Slope Be Used as a Substitute for T1 Slope? A Radiographic Analysis

STUDY DESIGN

Retrospective radiographic study.

OBJECTIVES

T1 slope is an important parameter of sagittal spinal balance. However, the T1 superior endplate can be difficult to visualize on radiographs due to overlying anatomical structures. C7 slope has been proposed as a potential substitute for T1 slope when the T1 superior endplate is not well visualized. The objective of this study was 2-fold: (1) to assess the correlation between C7 and T1 slopes on upright cervical spine radiographs and (2) to evaluate the interrater reliability of C7 slope.

METHODS

Cervical spine radiographs taken between December 2017 and June 2018 at a single institution were reviewed. Two observers measured upper C7 slope, lower C7 slope, and T1 slope. The correlations between upper and lower C7 slope and T1 slope were evaluated, and linear regression analyses were performed. Interrater reliability of C7 slope was also assessed.

RESULTS

In this cohort of 152 patients, there was a strong correlation between upper C7 slope and T1 slope (r = 0.91, P < .001), as well as between lower C7 slope and T1 slope (r = 0.90, P < .001). T1 slope could be estimated from the linear regression equation, T1 slope = 0.87 × C7 slope + 7, with an overall model fit of R ² = 0.8. There was strong interrater reliability for upper (intraclass correlation coefficient [ICC] = 0.95, P < .001) and lower C7 slope (ICC = 0.96, P < .001).

CONCLUSIONS

Both the upper and lower C7 slope are strongly correlated with T1 slope and can be used as a substitute to estimate T1 slope when the superior endplate of T1 is not well visualized.

Magnetic Resonance Imaging Research of Thoracic Inlet Parameters in the Cervical and Cervicothoracic Spine in Degenerative Cervical Spondylosis

OBJECTIVE

The purpose of this study was to examine the thoracic inlet angle (TIA) and its related parameters in the cervical and cervical-thoracic vertebrae in patients with degenerative cervical spondylosis (DCS) and explore the association of the TIA, tilt angle of the neck, and tilt angle of the first thoracic spine with the cervical degeneration score.

METHODS

Patients with DCS were included from January 2014 to December 2017. The relevant parameters were assessed on T2-weighted magnetic resonance imaging. The association of cervical parameters with the cervical degeneration score was examined by multiple linear regression model.

RESULTS

A total of 204 patients (126 men) were eligible and enrolled, with a mean age of 55-56 years. Men had significantly higher thoracic inlet parameters than women (all P < 0.05). Thoracic inlet parameters were positively correlated with age (all P < 0.05). After adjustment for age and sex, the significant association between the TIA and cervical or cervical-thoracic spine degeneration scores was not observed in all vertebrae. Meanwhile, men had higher vertebral height (VH) and intervertebral disk height (IVDH) than women. Only the VHs of C7, T1, and T2 and the IVDHs of C6-7, T1-2, and T2-3 were significantly and positively associated with the TIA (all P < 0.05).

CONCLUSIONS

Age was positively correlated with thoracic inlet parameters in patients with DCS. Men had significantly higher thoracic inlet parameters than women because the men had higher VHs and IVDHs. However, the TIA was not associated with the level of cervical disk degeneration. The clinical relevance of these findings has not been established.

Correlation of cervical and thoracic inlet sagittal parameters by MRI and radiography in patients with cervical spondylosis

To investigate the relationship between cervical and thoracic sagittal alignment parameters measured by magnetic resonance imaging (MRI) and x-ray in patients with cervical spondylosisData from 120 symptomatic patients who presented with cervical spondylosis between April 2015 and January 2016 were retrospectively analyzed. Patients received both a cervical MRI and a cervical radiograph during a single visit. The thoracic inlet angle (TIA), T1 slope (T1S), neck tilt (NT), C2-C7 angle (C2-C7), and C2-C7 sagittal vertical axis (C2-7 SVA) were assessed. Pearson correlation coefficient, paired t test, and linear regression models were used to analyze parameters obtained by cervical MRI and radiography.The difference in mean thoracic inlet angle x-ray (TIAX) and thoracic inlet angle MRI (TIAM) (TIAM-TIAX) (0.72 ± 5.82°) was not significant (P > .05). There were significant differences in mean T1 slope x-ray (T1SX) and T1 slope MRI (T1SM) (T1SM-T1SX) (-2.55 ± 6.14°), mean neck tilt x-ray (NTX) and neck tilt MRI (NTM) (NTM-NTX) (3.26 ± 6.01°), mean C2-C7 angle x-ray (C2-7X) and C2-C7 angle MRI (C2-7 M) (C2-7M-C2-7X) (-3.57 ± 10.00°), and mean C2-C7 sagittal vertical axis X ray (C2-7 SVAX) and C2-C7 sagittal vertical axis MRI (C2-7 SVAM) (C2-7 SVAM-C2-7 SVAX) (-4.50 ± 1.26 mm) (all P ≤ .001). There were positive correlations between TIAM and TIAX (r = 0.807), T1SM and T1SX (r = 0.581), NTM and NTX (r = 0.759), cervical loidosis MRI and cervical loidosis x-ray (r = 0.666), and SVAM and SVAX (r = 0.226).MRI may be useful to evaluate thoracic inlet and sagittal alignment parameters in patients with cervical spondylosis. Patients with cervical spondylosis may have a relatively low capacity for compensation in the cervical region.

What is a Right Distal Fusion Level for Prevention of Sagittal Imbalance in Multilevel Posterior Cervical Spine Surgery: C7 or T1?

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

To evaluate the sagittal alignment and T1 slope after multilevel posterior cervical fusion surgery depending on the distal fusion level; C7 or T1, and find out the appropriate distal fusion level.

SUMMARY OF BACKGROUND DATA

The sagittal balance of the cervical spine is known to be affected by cervical lordosis and T1 slope. However, T1 slope is not a constant parameter that can be frequently changed after the surgery. Furthermore, useful studies to help guide surgeons in decision-making as to the most appropriate distal level of fusion for cervical sagittal balance are very limited.

MATERIALS AND METHODS

From 2014 to 2015, 50 patients who underwent multilevel posterior cervical fusion surgery were evaluated and followed up for >2 years. Group 1 was composed of 29 patients whose distal fusion level was C7. Group 2 was composed of 21 patients whose distal fusion level was T1. C1-C2 lordosis, C2-C7 lordosis, C2-C7 sagittal vertical axis (SVA), and T1 slope were measured on preoperative and the last follow-up.

RESULTS

In group 1, C2-C7 SVA (23.1→30.4 mm, P=0.043) was worsened, and T1 slope (22.3→32.9 degrees, P=0.001) was increased after the surgery. In group 2, no significant change occurred in C2-C7 SVA after the surgery (25.3 →23.6 mm, P=0.648). The last follow-up T1 slope was similar with preoperative T1 slope (22.7→21.8 degrees, P=0.04) in group 2.

CONCLUSIONS

This study showed that sagittal alignment became worse after the multilevel posterior cervical surgery when distal fusion level was stopped at C7, which was associated with increase of T1 slope. However, when we extended the distal fusion level to T1, T1 slope was not changed after the surgery. Therefore, sagittal alignment was maintained after the surgery. On the basis of the results of this study, we recommend distal fusion extends to T1.

LEVEL OF EVIDENCE

Level III.

Measurement of Cervical Sagittal Alignment Parameters on X-Ray Films of Adults without Severe Spinal Deformity Whose Shoulder Hides the Lower Cervical Column

OBJECTIVE

The Cobb angle between the lower endplate of C2 and C7 (C2L-C7L angle) is a traditional parameter used for the assessment of the cervical alignment. However, when the lower cervical column is masked by the shoulder, measurements are difficult. In the present study, we inspected 191 X-ray films, measured the Cobb angle between C2L and the endplates at the several levels of the lower cervical column, and assessed their usefulness of such measurements for the determination of cervical sagittal alignment.

METHODS

We obtained X-ray films on 191 patients ranging in age from 20 to 93 years. The Cobb angle between C2L and the C7 upper (C7U), the C6 lower (C6L), the C6 upper (C6U), and the C5 lower endplate (C5L) was measured and compared with the C2L-C7L angle.

RESULTS

C7L was identified in 116 of 191 patients (60.7%). Except for C2L-C7U angle (P = 0.55), the difference in the mean between C2L-C7L angle and the angle between C2L and the other endplates was statistically significant (P < 0.05). There was a very strong correlation between C2L-C7L angle and C2L-C7U angle (r = 0.99), C2L-C6L angle (r = 0.96), C2L-C6U angle (r = 0.94), and C2L-C5L angle (r = 0.86).

CONCLUSIONS

To measure the C2L-C7L angle on unclear X-ray films, C7U can be substituted for C7L. Our measurement data for the C6 and C5 endplates were statistically different; however, the correlation between the C2L-C7L angle and C2L-C6U angle, C2L-C6L angle or C2L-C5L angle was very strong. In patients with unclear lower vertebral bodies, cervical sagittal alignment can be predicted by using adjacent endplates.

Cervical lordosis in asymptomatic individuals: a meta-analysis

Background

Cervical lordosis has important clinical and surgical implications. Cervical spine curvature is reported with considerable variability in individual studies. The aim of this study was to examine the existence and extent of cervical lordosis in asymptomatic individuals and to evaluate its relationship with age and gender.

Methods

A comprehensive literature search was conducted in several electronic databases. Study selection was based on pre-determined eligibility criteria. Random effects meta-analyses were performed to estimate the proportion of asymptomatic individuals with lordosis and the effect size of cervical lordotic curvature in these individuals which followed metaregression analysis to examine the factors affecting cervical lordosis. Data from 21 studies (15,364 asymptomatic individuals, age 42.30 years [95% confidence interval 36.42, 48.18], 54.2% males) were used in the present study.

Results

In this population, 63.99% [95% confidence interval 44.94, 83.03] individuals possessed lordotic curvature. Degree of lordotic curvature differed by method of measurement; 12.71° [6.59, 18.84] with Cobb C2–C7 method and 18.55° [14.48, 22.63] with posterior tangent method. Lordotic curvature was not significantly different between symptomatic and asymptomatic individuals but was significantly higher in males in comparison with females. Age was not significantly associated with lordotic cervical curvature.

Conclusion

Majority of the asymptomatic individuals possesses lordotic cervical curvature which is higher in males than in females but have no relationship with age or symptoms.

The K-line in the cervical ossification of the posterior longitudinal ligament is different on plain radiographs and CT images

BACKGROUND

The K-line, which is a virtual line between the midpoints of the antero-posterior canal diameter at C2 and C7, can be useful for determination of surgical procedures for cervical ossification of the posterior longitudinal ligament (OPLL). Although K-line is originally measured with plain radiogram, computed tomography multiplanar reconstruction (CT-MPR) is applied for K-line measurement by several surgeons. The purpose of the present study was to analyze whether there is a difference in K-lines obtained from radiographs of standing patients and those obtained from CT-MPR images of supine patients.

METHODS

The present study included 65 patients with cervical OPLL underwent surgical treatment. We investigated the K-line (+ or -) before surgery, measured from lateral cervical spine radiographs taken in standing patients in a neutral position (X-P-based K-line) and CT-MPR mid-sagittal images obtained in supine patients (CT-based K-line). The X-P-based and CT-based K-lines were compared and differences between them were assessed.

RESULTS

The-X-P-based K-line was found to be (+) in 35 patients and (-) in 30 patients. Four of 35 patients with an X-P-based K-line (11%) showed a change from K-line (+) to (-) in CT-based K-line measurements. One of 30 patients with an X-P-based K-line (3%) showed a change from (-) to (+) in CT-based measurements.

CONCLUSIONS

The K-line should be measured with plain radiogram of standing patients because X-P-based K-line and CT-based K-line can be different.

Cervical sagittal balance parameters after single-level anterior cervical discectomy and fusion: Correlations with clinical and functional outcomes

Background:

Normal sagittal cervical alignment has been associated with improved outcome after anterior cervical discectomy and fusion (ACDF).

Objective:

The aim of this study is to identify alterations of cervical sagittal balance parameters after single-level ACDF and assess correlations with postoperative functionality.

Methods:

A retrospective chart review was performed between January 2010 and January 2014 to identify adult patients with no previous cervical spine surgery who underwent ACDF at any one level between C2 and C7 for the single-level degenerative disease. Tumor, infection, and trauma cases were excluded from the study. For the included cases, the following data were recorded preoperatively and 6 months–1 year after surgery: sagittal balance-marker measurements of the C1–C2 angle, C2–C7 angle, C7 slope, segmental angle at the operated level, and sagittal vertical axis (SVA) distance between C2 and C7, as well as the neck disability index and visual analog scale of pain.

Results:

The present study included 47 patients (average age: 51.2 years; range: 28–86 years). A moderate negative correlation between a smaller C2–C7 angle and the presence of right arm pain before treatment was found (P = 0.0281). Postoperatively, functionality scores significantly improved in all patients. C1–C2 angle increased with statistical significance (P = 0.0255). C2–C7 angle, segmental angle, C7 slope, and SVA C2–C7 distance did not change with statistical significance after surgery. C7 slope significantly correlated with overall cervical sagittal balance (P < 0.05).

Conclusions:

Single-level ACDF significantly increases upper cervical lordosis (C1–C2) without significantly changing lower cervical lordosis (C2–C7). The C7 slope is a significant marker of overall cervical sagittal alignment (P < 0.05).

Thoracic Inlet Parameters for Degenerative Cervical Spondylolisthesis Imaging Measurement

Background

The aim of this study was to explore the diagnostic value of sagittal measurement of thoracic inlet parameters for degenerative cervical spondylolisthesis (DCS).

Material/Methods

We initially included 65 patients with DCS and the same number of health people as the control group by using cervical radiograph evaluations. We analyzed the x-ray and computer tomographic (CT) data in prone and standing position at the same time. Measurement of cervical sagittal parameters was carried out in a standardized supine position. Multivariate logistic regression analysis was performed to evaluate these parameters as a diagnostic index for DCS.

Results

There were 60 cases enrolled in the DCS group, and 62 cases included in the control group. The T1 slope and thoracic inlet angle (TIA) were significantly greater for the DCS group compared to the control group (24.33±2.85º versus 19.59±2.04º, p=0.00; 76.11±9.82º versus 72.86±7.31º, p=0.03, respectively). We observed no significant difference for the results of the neck tilt (NT), C2–C7 angle in the control and the DSC group (p>0.05). Logistic regression analysis and receiver operating characteristic (ROC) curve revealed that preoperative T1 slope of more than 22.0º showed significantly diagnostic value for the DCS group (p<0.05).

Conclusions

Patients with preoperative sagittal imbalance of thoracic inlet have a statistically significant increased risk of DCS. T1 slope of more than 22.0º showed significantly diagnostic value for the incidence of DCS.

Can C7 Slope Substitute the T1 slope?: An Analysis Using Cervical Radiographs and Kinematic MRIs

STUDY DESIGN

Retrospective analysis of consecutive 45 radiographs and 120 kinematic magnetic resonance images (kMRI) OBJECTIVE.: The aim was to assess the visibility of C7 and T1 endplates on radiographs, and to verify the correlation between C7 or T1 slope and cervical balance parameters using kMRI.

SUMMARY OF BACKGROUND DATA

Because the T1 slope is not always visible due to the anatomical interference, several studies have used C7 slope instead of T1. However, it is still unclear whether the C7 endplate is more visible on radiographs than T1, and if C7 slope has similarity with T1 slope.

METHODS

The endplate visibility was determined using weight-bearing radiography. Subsequently, using weight-bearing MR images, the C7 slope of upper and lower endplate, T1 slope, C1 inclination, C2 slope, atlas-dens interval (ADI), C2-C7 lordotic angle, cervical sagittal vertical axis (cSVA), cervical tilt, cranial tilt, neck tilt, thoracic inlet angle (TIA) were measured, for the analysis of correlation between three types of slopes and cervical balance parameters.

RESULTS

82% of the upper C7, and 18% of T1 endplate were clearly visible. The upper C7 endplate was significantly visible, whereas T1 endplate was significantly invisible (residual analysis, P < 0.01). Linear regression analysis showed correlation between the upper C7 slope and T1 slope (R = 0.818, P < 0.01) and, lower C7 slope and T1 slope (R = 0.840, P < 0.01). T1 slope significantly correlated with neck tilt, TIA, C2-C7 angle, cSVA, cervical and cranial tilt, but not with the C1 inclination, C2 slope, and ADI. Upper and lower C7 slopes showed the close resemblance with T1 slope in terms of correlation with those parameters.

CONCLUSION

Both, upper and lower C7 slope correlated strongly with T1 slope and showed similar relationship with cervical balance parameters as T1 slope. Therefore, C7 slope could potentially substitute T1 slope, especially upper C7 slope due to the good visibility.

LEVEL OF EVIDENCE

3.

Cervical Spine Deformity-Part 1: Biomechanics, Radiographic Parameters, and Classification

Cervical spine deformities can have a significant negative impact on the quality of life by causing pain, myelopathy, radiculopathy, sensorimotor deficits, as well as inability to maintain horizontal gaze in severe cases. Many different surgical options exist for operative management of cervical spine deformities. However, selecting the correct approach that ensures the optimal clinical outcome can be challenging and is often controversial. We aim to provide an overview of cervical spine deformity in a 3-part series covering topics including the biomechanics, radiographic parameters, classification, treatment algorithms, surgical techniques, clinical outcome, and complication avoidance with a review of pertinent literature.

Diagnostic Value of T1 Slope in Degenerative Cervical Spondylotic Myelopathy

Background

To explore the diagnostic value of sagittal measurement of thoracic inlet parameters for degenerative cervical spondylotic myelopathy (DCSM).

Material/Methods

Sixty patients with DCSM (study group) and the same number of normal subjects (control group) were initially enrolled in the study. All data from X-ray in the standing position and computed tomography (CT) in the supine position were collected and carefully analyzed. Cervical sagittal parameters, including C2–C7 angle, C2–C7 sagittal vertical axis (C2–C7 SVA), T1 slope, thoracic inlet angle (TIA), and neck tilt (NT), were measured at the lateral radiographs by using standard X-rays and CT. Univariate analysis and multivariate logistic regression analysis were carried out to explore the diagnostic value of cervical sagittal parameters for the DCSM.

Results

All the enrolled patients in the study and control groups completed the follow-up, and the mean follow-up periods were 35.8 months in the study group and 36.3 months in the control group. The DCSM group had smaller T1 slope and TIA when compared with that of the control group (18.14±2.67° vs. 24.16±3.7°, p=0.00; 66.42±12.36° vs. 70.42±10.21°, p=0.01). Logistic regression analysis and receiver operating characteristic (ROC) curve revealed that preoperative T1 slope of less than 18.5° had significant diagnostic value for the incidence of DCSM (p<0.05).

Conclusions

Patients with sagittal imbalance of thoracic inlet parameters have higher risk of DCSM, while T1 slope of less than 18.5° showed significant diagnostic value for the incidence of DCSM.

[Correlation analysis of preoperative T 1 slope in MRI and physiological curvature loss after expansive open-door laminoplasty]

Objective

To investigate whether preoperative T ₁ slope (T ₁S) in MRI can predict the changes of cervical curvature after expansive open-door laminoplasty (EOLP) in patients with cervical spondylotic myelopathy, so as to make up for the shortcomings of difficult measurement in X-ray film.

Methods

The clinical data of 36 patients with cervical spondylotic myelopathy who underwent EOLP were retrospectively analysed. There were 21 males and 15 females with an average age of 55.8 years (range, 37-73 years) and an average follow-up time of 14.3 months (range, 12-24 months). The preoperative X-ray films at dynamic position, CT, and MRI of cervical spine before operation, and the anteroposterior and lateral X-ray films at last follow-up were taken out to measure the following sagittal parameters. The parameters included C ₂-C ₇ Cobb angle and C ₂-C ₇ sagittal vertical axis (C ₂-C ₇ SVA) in all patients before operation and at last follow-up; preoperative T ₁S were measured in MRI, and the patients were divided into larger T ₁S group (T ₁S>19°, group A) and small T ₁S group (T ₁S≤19°, group B) according to the median of T ₁S, and the preoperative T ₁S, C ₂-C ₇ Cobb angle, C ₂-C ₇ SVA, and the C ₂-C ₇ Cobb angle and C ₂-C ₇ SVA at last follow-up, difference in axial distance (the difference of C ₂-C ₇ SVA before and after operation), postoperative curvature loss (the difference of C ₂-C ₇ Cobb angle before and after operation), the number of patients whose curvature loss was more than 5° after operation, and the number of patients whose kyphosis changed (C ₂-C ₇ Cobb angle was less than 0° after operation).

Results

The C ₂-C ₇ Cobb angle at last follow-up was significantly decreased when compared with preoperative value ( t=8.000, P=0.000), but there was no significant difference in C ₂-C ₇ SVA between pre- and post-operation ( t=-1.842, P=0.074). The preoperative T ₁S was (19.69±3.39)°; there were 17 cases in group A and 19 cases in group B with no significant difference in gender and age between 2 groups ( P>0.05). The preoperative C ₂-C ₇ Cobb angle in group B was significantly lower than that in group A ( t=-2.150, P=0.039), while there was no significant difference in preoperative C ₂-C ₇ SVA between 2 groups ( t=0.206, P=0.838). At last follow-up, except for the curvature loss after operation in group B was significantly lower than that in group A ( t=-2.723, P=0.010), there was no significant difference in the other indicators between 2 groups ( P>0.05).

Conclusion

Preoperative larger T ₁S (T ₁S>19°) in MRI had a larger preoperative lordosis angle, but more postoperative physiological curvature was lost; preoperative T ₁S in MRI can not predict postoperative curvature loss, but preoperative larger T ₁S may be more prone to kyphosis.

Comparative Analysis of Three Imaging Modalities for Evaluation of Cervical Sagittal Alignment Parameters: A Validity and Reliability Study

STUDY DESIGN

This was a radiologic validity and reliability study.

OBJECTIVE

We aimed to assess the validity and reliability of measurements from standing lateral cervical radiography (XR), reconstructed midsagittal images of supine cervical computerized tomography (CT) scans, and supine magnetic resonance imaging (MRI) for evaluating C2-C7 distance (C27 SVA), C2-C7 Cobb angle (CL), T1 slope (T1S), thoracic inlet angle (TIA), and neck tilt (NT).

SUMMARY OF BACKGROUND DATA

XR is the criterion standard imaging modality for measuring cervical sagittal alignment parameters. However, overlapping bony structures and soft tissue often make the upper end of the manubrium and cervicothoracic junction indiscernible. CT and MRI can overcome this limitation, but their reliability and validity have not been fully elucidated.

METHODS

Fifty sets of three examinations from our database have been randomly selected. Three experienced spinal surgeons independently measured C27 SVA, CL, T1S, TIA, and NT. Paired t test and Pearson correlation were used to analyze the validity of CT and MRI in comparison with that of XR. Interobserver and intraobserver reliability were assessed by using the intraclass correlation coefficient (ICC).

RESULTS

The paired t test confirmed the similarities of all CT (except C27 SVA) and MR parameters (except C27 SVA and CL) to the XR parameters (all P > 0.05). All parameters except C27 SVA were correlated (Pearson correlation coefficient, 0.523-0.913). Correlation was highest between CT and MRI and lowest between CT and XR. All three imaging modalities had excellent intraobserver and interobserver reliability (ICC range: 0.770-0.999). Intraobserver and interobserver reliability were highest with MRI and lowest with XR.

CONCLUSION

CT and especially MRI were more reliable than XR for evaluating cervical sagittal alignment parameters. Considering the reliability and radiation exposure, MRI is a good alternative to XR for measuring cervical sagittal alignment parameters, especially thoracic inlet alignment.

LEVEL OF EVIDENCE

4.

Is high T-1 slope a significant risk factor for developing interlaminar bony fusion after cervical laminoplasty? A retrospective cohort study

OBJECTIVE

Several investigators have reported the occurrence of interlaminar bony fusion after cervical laminoplasty, which is reportedly associated with reduced postoperative cervical range of motion (ROM). However, to the authors’ knowledge, no previous study has investigated the characteristics of patients who were likely to develop interlaminar bony fusion after cervical laminoplasty. Therefore, the objective of this study was to investigate the risk factors for interlaminar bony fusion in patients with cervical spondylotic myelopathy (CSM) following cervical laminoplasty and to investigate the effect of interlaminar bony fusion on surgical outcomes.

METHODS

The authors retrospectively reviewed data from 92 patients with CSM (63 men and 29 women) after cervical laminoplasty. The presence of interlaminar bony fusion was evaluated by functional radiographs 2 years after surgery. The patients were divided into 2 groups according to the presence of postoperative interlaminar bony fusion: a fusion group (at least 1 new postoperative interlaminar bony fusion) and a nonfusion group (no new interlaminar bony fusion). Potential risk factors for postoperative interlaminar bony fusion were assessed, including diabetes mellitus, smoking status, whether the C-2 lamina was included in the surgical treatment, C2–7 Cobb angle in each cervical position, preoperative cervical ROM, and T-1 slope. The differences in each variable were compared between the fusion and nonfusion groups. Thereafter, multivariate logistic regression analysis was performed to identify the risk factors for postoperative interlaminar bony fusion. For surgical outcomes, the recovery rate based on Japanese Orthopaedic Association scores and the reduction rate of cervical ROM were evaluated 2 years after surgery.

RESULTS

Interlaminar bony fusion was observed in 60 cases, 52 of which were observed at the C2–3 level. Patients in the fusion group were significantly older, had a significantly larger C2–7 angle in flexion, and had a significantly lower preoperative cervical ROM than those in the nonfusion group. A high T-1 slope was significantly more frequent in the fusion group. Multivariate analysis revealed that the significant risk factors for postoperative interlaminar bony fusion were high T-1 slope (odds ratio 4.81; p = 0.0015) and older age (odds ratio 1.05; p = 0.025). The Japanese Orthopaedic Association recovery rate in patients with interlaminar bony fusion did not differ significantly from those without bony fusion (45% vs 48%; p = 0.73). However, patients with bony fusion showed significantly reduced postoperative cervical ROM compared with those without bony fusion (50% vs 25%; p < 0.001).

CONCLUSIONS

High T-1 slope and older age were significant risk factors for developing interlaminar bony fusion after cervical laminoplasty in patients with CSM. Interlaminar bony fusion was associated with reduced postoperative cervical ROM, but it did not affect neurological outcomes.

MRI kinematic analysis of T1 sagittal motion between cervical flexion and extension positions in 145 patients

PURPOSE

Although the T1 vertebra is considered as an important factor of cervical balance, little is known about its motion between flexion and extension. The purpose of present study was to analyze the T1 sagittal motion using kinematic magnetic resonance imaging (kMRI), and to identify factors that relate to T1 sagittal motion.

METHODS

We retrospectively analyzed 145 kMR images taken in weight-bearing neutral, flexion and extension positions. Cervical balance parameters were evaluated in each position. The degree of T1 sagittal motion was defined as [(T1 slope at extension) - (T1 slope at flexion)]. All patients were divided into three groups: Positive group (T1 followed the head motion, T1 sagittal motion > 5°), Stable group (5 ≥, ≥ - 5) and Negative group (T1 moved in the opposite direction from the head motion, > - 5). The groups were compared and multivariate logistic regression analysis was calculated.

RESULTS

There were 57 (40%) patients in the positive, 56 (39%) in the stable and 32 (22%) in the negative group. The positive group had the largest C2-7 sagittal vertical axis in flexion (p < 0.001) and the shortest in the extension (p = 0.023). Similar trends were seen in cranial tilt and cervical tilt. The value of T1 height < 27 mm was a significant independent factor for the negative group (p = 0.008, adjusted odds ratio = 5.958).

CONCLUSION

Based on T1 sagittal motion, 40% of the patients were classified in positive group (the T1 vertebra followed the head motion in flexion and extension), and 20% were classified in the negative group (the T1 vertebra moved in the opposite direction from the head motion). T1 height < 27 mm was a potential predictor of negative group.

Preoperative cervical sagittal alignment parameters and their impacts on myelopathy in patients with cervical spondylotic myelopathy: a retrospective study

Background

Cervical sagittal alignment plays an important role in the pathogenesis of cervical spondylotic myelopathy (CSM), but there are limited studies on the cervical sagittal parameters in CSM patients and their correlations with myelopathy. The aim of this study is to investigate the correlations among the preoperative cervical sagittal alignment parameters and their correlations with the development of myelopathy in patients with CSM.

Methods

We retrospectively collected 212 patients with CSM who underwent surgical interventions. Gender, age, modified Japanese Orthopedic Association score (mJOA), cervical lordosis (CL), C2–C7 sagittal vertical axis (C2–C7 SVA), T1 slope (T1S), neck tilt (NT) and thoracic inlet angle (TIA) were collected before operation. Interobserver and intraobserver reliability were calculated for all measurements (intraclass correlation coefficient, ICC). Data were analyzed with Pearson and Spearman correlation tests and multiple linear regression analysis.

Results

A total of 212 patients with CSM were included in this study (male: 136, female: 76) with an average age of 54.5 ± 10.1 years old. Intraobserver and interobserver reliability for all included radiographic parameters presented good to excellent agreement (ICC > 0.7). No significant differences in demographic and radiological parameters have been observed between males and females (P > 0.05). We found statistically significant correlations among the following parameters: age with CL (r = 0.135, P = 0.049), age with T1S (r = 0.222, P = 0.001), CL with T1S (r = 0.291, P < 0.001), CL with C2-C7 SVA (r =  − 0.395, P < 0.001), mJOA with age (r =  − 0.274, P < 0.001), mJOA with C2–C7 SVA (r =  − 0.219, P < 0.001) and mJOA with T₁S(r =  − 0.171, p = 0.013). Linear regression analysis showed that C2–C7 SVA was the predictor of CL (adjusted R² = 0.152, P < 0.001) and multiple linear regression showed that age combined with C2–C7 SVA was a sensitive predictor of mJOA (adjusted R² = 0.106, P < 0.001).

Discussion

There were significant correlations among certain preoperative cervical sagittal parameters in CSM patients. CL was the only predictor of C2–C7 SVA. Age combined with C2–C7 SVA could predict the severity of myelopathy.

There is no increased risk of adjacent segment disease at the cervicothoracic junction following an anterior cervical discectomy and fusion to C7

BACKGROUND CONTEXT

Anterior cervical discectomy and fusion (ACDF) is a very common operative intervention for the treatment of cervical spine degenerative disease in those who have failed non-operative measures. However, studies examining long-term follow-up on patients who underwent ACDF reveal evidence of radiographic and clinical degenerative disc disease at the levels adjacent to the fusion construct. Consistent with other junctional regions of the spine, the cervicothoracic junction (CTJ) has significant morphologic variations. As a result, the CTJ undergoes significant static and dynamic stress. Given these findings, there has been some thought that ACDF down to C7 may experience additional risks for adjacent segment degeneration/disease (ASD) when compared with ASDFs that are cephalad to C7.

PURPOSE

The goal of this study is to evaluate the rate of radiographic and clinical ASD in patients who have undergone single- or multilevel ACDF, down to C7.

STUDY DESIGN

This is a retrospective cohort study.

PATIENT SAMPLE

The sample included consecutive patients from a single orthopedic surgeon at one quaternary referral medical center who underwent an ACDF between January 2008 and November 2014. Indications for surgery included radiculopathy, myelopathy, or myeloradiculopathy in the setting of failed conservative treatments. Patients were excluded if they had an ACDF of which the caudal level was cephalad to C7 or if they had undergone a previous cervical fusion.

OUTCOME MEASURES

Radiographic diagnosis of ASD was determined by the presence of disc space narrowing >50%, new or enlarged osteophytes, end plate sclerosis, or increased calcification of the anterior longitudinal ligament (ALL). Postoperatively, data were collected on the presence of new radicular or myelopathic symptoms indicative of pathology at C7-T1, indicating a diagnosis of clinical ASD.

METHODS

Demographic information was collected for all patients, which included age, sex, body mass index, smoking status, and Charleston Comorbidity Index (CCI). Several radiographic parameters were measured preoperatively, immediately postoperatively, and at the last follow-up: C2-C7 lordosis, sagittal vertical axis (SVA), thoracic inlet angle (TIA), and T1 slope C2-C7 lordosis were measured using the Cobb angle between the inferior end plate of C2 to the inferior end plate of C7. Radiographic and clinical factors associated with ASD were analyzed postoperatively.

RESULTS

Four patients (4.8%) presented with clinical evidence of ASD, all of whom also showed signs of radiographic ASD and improved with conservative measures. No patients underwent reoperation for ASD at the C7-T1 junction. Thirty patients (36.1%) presented radiographic evidence of ASD. These were generally older (54.4 vs. 48.4 years; p=.014). There were neither significant differences in radiographic parameters nor between single- versus multilevel ACDFs and the development of ASD.

CONCLUSIONS

The cervicothoracic junction may present with vulnerability to ASD given the junctional biomechanics. However, this study provides evidence that an ACDF with the caudal level of C7 does not incur additional risk of ASD, showing similar outcomes to ACDFs at other levels.

Magnetic resonance imaging: A possible alternative to a standing lateral radiograph for evaluating cervical sagittal alignment in patients with cervical disc herniation?

BACKGROUND AND OBJECTIVES

Convincing evidence supporting the use of magnetic resonance imaging (MRI) as an effective tool for evaluating cervical sagittal alignment is lacking. This study aims to analyze the differences and correlations between cervical sagittal parameters on x-ray and MRI in patients with cervical disc herniation and to determine whether MRI could substitute for cervical x-ray for measurement of cervical sagittal parameters.

METHODS

One hundred forty-three adults with cervical disc herniation were recruited. Each patient had both an x-ray and MRI examination of the cervical spine. The cervical sagittal parameters were measured and compared on x-ray and MRI including: C2-C7 Cobb angle, C2-C7 sagittal vertical axis (C2-C7 SVA), cervical tilt (CT), T1 Slope (T1S), and neck tilt (NT). The data were analyzed using a paired-samples t test, a Pearson correlation test, and linear regression.

RESULTS

The values of C2-C7 Cobb angle, C2-C7 SVA, CT and T1S on X-ray were larger than those on MRI (P < .05) and NT on X-ray was smaller than that on MRI (P < .05). Each of the cervical sagittal parameters had a significant correlation with the corresponding one on MRI (r = 0.699, 0.585, 0.574, 0.579 and 0.613, respectively) (C2-C7 Cobb MRI = 0.957 + 0.721 C2-C7 Cobb X, C2-C7 SVA MRI = 6.423 + 0.500 C2-C7 SVAX, CT MRI = 3.121 + 0.718 CTX, T1S MRI = 7.416 + 0.613 T1SX, NT MRI = 22.548 + 0.601 NTX).

CONCLUSION

Although MRI and x-ray measurements of cervical sagittal parameters were different, there were significant correlations between the results. MRI could be used to evaluate the sagittal balance of the cervical spine with great reliability.

Modic changes of the cervical spine: T1 slope and its impact on axial neck pain

Background

The purpose of the research was to evaluate cervical sagittal parameters on magnetic resonance imaging (MRI) in patients with Modic changes and its impact on axial neck pain.

Methods

This study consisted of 266 consecutive asymptomatic or symptomatic patients with Modic changes, whose average age was 50.9±12.6 years from January 2015 to December 2016. Cervical sagittal parameters included sagittal alignment of the cervical spine (SACS), T1 slope, thoracic inlet angle (TIA), and neck tilt (NT). The Modic changes group was compared with an asymptomatic control group of 338 age- and gender-matched adults.

Results

In the Modic changes group, T1 slope was significantly higher (25.8°±6.3°) compared with that in the control group (22.5°±6.8°) (P=0.000). However, there was no significant difference of the NT, TIA, and SACS between the two groups. Patients in the Modic changes group were more likely to have experienced historical axial neck pain compared with the control group (P=0.000). With regard to the disc degeneration, it indicated that the disc in the Modic changes group had more severe disc degeneration (P=0.032).

Conclusion

T1 slope in the Modic changes group was significantly higher compared to that of the control group. The findings suggested that a higher T1 slope with broken compensation of cervical sagittal mechanism may be associated with the development of Modic changes in the cervical spine.

Characteristics of Modic changes in cervical kyphosis and their association with axial neck pain

BACKGROUND

The purpose of this study was to evaluate characteristics of Modic changes in cervical kyphosis (CK) and their association with axial neck pain.

METHODS

Study participants included 286 asymptomatic or symptomatic patients with CK (mean age = 54.2 ± 12.2 years) who were consecutively enrolled from March 2009 to October 2015. Clinical and radiographic evaluations were performed at a university outpatient department. CK was classified as global type, reverse sigmoid type, or sigmoid type.

RESULTS

There were 138 participants with global type CK, 103 with reverse sigmoid type CK, and 45 with sigmoid type CK. Of the 286 participants, 102 had Modic changes (Modic-1 in 38 segments and Modic-2 in 75 segments). Spinal cord compression grade and disc degeneration occurred more frequently in the group with axial neck pain compared to the group without pain. Angular motion was decreased in those with axial neck pain (mean ± standard deviation [SD] 7.8°±4.6°) compared to those who were asymptomatic (mean ± SD 8.9°±5.1°; P<0.001). In multivariate logistic regression analysis, Modic changes were associated with axial neck pain (odds ratio =5.356; 95% confidence interval =1.314-12.800; P<0.001).

CONCLUSION

Modic changes occur most commonly in association with CK global type and less commonly with reverse sigmoid type and sigmoid type. Modic changes are associated with axial neck pain in patients with CK.

Cervical lordosis: the effect of age and gender

BACKGROUND CONTEXT

Cervical lordosis is of great importance to posture and function. Neck pain and disability is often associated with cervical lordosis malalignment. Surgical procedures involving cervical lordosis stabilization or restoration must take into account age and gender differences in cervical lordosis architecture to avoid further complications.

PURPOSE

Therefore, the purpose of the present study was to evaluate differences in cervical lordosis between males and females from childhood to adulthood.

STUDY DESIGN

This is a retrospective descriptive study.

PATIENT SAMPLE

A total of 197 lateral cervical radiographs of patients aged 6-50 years were examined. These were divided into two age groups: the younger group (76 children aged 6-19; 48 boys and 28 girls) and the adult group (121 adults aged 20-50; 61 males and 60 females). The retrospective review of the radiographs was approved by the institutional review board.

METHODS

On each radiograph, six lordosis angles were measured including total cervical lordosis (FM-C7), upper (FM-C3; C1-C3) and lower (C3-C7) cervical lordosis, C1-C7 lordosis, and the angle between foramen magnum and the atlas (FM-C1). Wedging angles of each vertebral body (C3-C7) and intervertebral discs (C2-C3 to C6-C7) were also measured. Vertebral body wedging and intervertebral disc wedging were defined as the sum of the individual body or disc wedging of C3 to C7, respectively. Each cervical radiograph was classified according to four postural categories: A-lordotic, B-straight, C-double curve, and D-kyphotic.

RESULTS

The total cervical lordosis of males and females was similar. Males had smaller upper cervical lordosis (FM-C3) and higher lower cervical lordosis (C3-C7) than females. The sum of vertebral body wedging of males and females is kyphotic (anterior height smaller than posterior height). Males had more lordotic intervertebral discs than females. Half of the adults (51%) had lordotic cervical spine, 41% had straight spine, and less than 10% had double curve or kyphotic spine. Children had similar total cervical lordosis (FM-C7) to adults. The sum of vertebral body wedging for children was more kyphotic-by 7°-than that of adults, whereas the sum of intervertebral disc wedging in children was more lordotic-by11°-than that of adults. Seventy-one percent of the children had lordotic cervical spine, 23% had straight spine, and less than 6% had double curve spine. Gender differences are already apparent in children as girls had higher upper cervical lordosis (FM-C3; C1-C3) than boys do.

CONCLUSIONS

Although the total cervical lordosis (FM-C7) did not change between age groups, and between males and females, the internal architecture of the cervical lordosis changed significantly. Practitioners before neck stabilization procedures or correction and restoration should therefore take into account the gender and age differences in cervical lordosis.

[Analysis of cervical sagittal parameters on MRI in patients with cervical spondylotic myelopathy]

Objective

To analyse the correlation between cervical sagittal parameters of cervical spondylotic myelopathy in different sagittal curvature so as to find out representative cervical sagittal alignment parameters by measuring on MRI.

Methods

A retrospective analysis was made on the clinical data of 88 patients with cervical spondylotic myelopathy between July 2015 and January 2016. The C ₂-C ₇ Cobb angle, T ₁ slope (T ₁S), and C ₂-C ₇ sagittal vertical axis (C ₂-C ₇ SVA) were measured on T2-weight MRI. According to C ₂-C ₇ Cobb angle, the patients were divided into lordosis group (≥10° Cobb angle, 48 cases) and straightened group (0-10° Cobb angle, 40 cases). Intraclass correlation coefficient (ICC) was used for the reliability of measured data, Pearson correlation analysis for correlation between cervical sagittal parameters.

Results

ICC was 0.858-0.946, indicating good consistency of measurement parameters. The C ₂-C ₇ Cobb angle, T ₁S, and C ₂-C ₇ SVA were (5.6±2.4)°, (22.2±6.7)°, and (10.2±5.4) mm in straightened group, and were (20.1±8.2)°, (23.4±8.9)°, and (8.2±4.6) mm in lordosis group respectively. There was no correlation between the 3 parameters in straighten group ( r=0.100, P=0.510 for T ₁S and C ₂-C ₇ Cobb angle; r=-0.100, P=0.500 for T ₁S and C ₂-C ₇ SVA; r=0.080, P=0.610 for C ₂-C ₇ Cobb angle and C ₂-C ₇ SVA). There was positive correlation between T ₁S and C ₂-C ₇ Cobb angle ( r=0.540, P=0.000), negative correlation between T ₁S and C ₂-C ₇ SVA ( r=-0.450, P=0.001), and no correlation between C ₂-C ₇ Cobb angle and C ₂-C ₇ SVA ( r=-0.003, P=0.980).

Conclusion

For cervical spondylotic myelopathy in patients with cervical lordosis, only T ₁S measurement on MRI can be used as the main parameter to judge the sagittal curvature, but in patients with straightened cervical Cobb angle, measurements of T ₁S, C ₂-C ₇ Cobb angle, and C ₂-C ₇ SVA should be taken for the comprehensive evaluation of cervical sagittal curvature.