Characteristics of Cervical Spine Motion in Different Types of Cervical Alignment: Kinematic MRI Study

A New Index for Cervical Curvature Evaluation - Relative Cervical Curvature Area

OBJECTIVE

To put forward a new index of cervical curvature evaluation - relative cervical curvature area, and a new classification of cervical spine was proposed according to the relative cervical curvature area.

METHODS

A total of 167 subjects with cervical spondylosis were included in the study. Firstly, 119 subjects were selected to measure C2-C7 lordosis angle by Cobb angle method, Harrison posterior tangent method, and Jackson physiological stress line method, and then their relative cervical curvature area, C1-C7 Cobb angle, C7 slope, and T1 slope were measured. The correlation between relative cervical curvature area and 3 measurement methods and common sagittal parameters was analyzed. According to the angle classification method, we calculated the diagnostic boundary value of the relative cervical curvature area classification, and selected 48 subjects to evaluate its diagnostic efficacy. Finally, 119 subjects were re-evaluated according to the diagnostic threshold and the number of intersections to verify the feasibility of the new classification.

RESULTS

The results showed that the relative cervical curvature area index had good intraobserver and interobserver repeatability. Relative cervical curvature area was correlated with Harrison posterior tangent method (r = 0.930), Cobb angle method (r = 0.886), and Jackson physiological stress line method (r = 0.920), and correlated with C1-C7 Cobb angle, C7 slope, and T1 slope. The relative cervical curvature area has a good diagnostic performance for distinguishing patients with lordosis, straightening, and kyphosis. According to the new classification of cervical spine, 119 subjects were divided into 57 simple lordosis, 11 simple straightening, 4 simple kyphosis, 26 S-type, and 21 RS-type.

CONCLUSIONS

The relative cervical curvature area uses the area parameter instead of the original angle parameter and distance parameter to incorporate the change of segmental curvature, which makes up for the shortcomings of the Cobb angle method that only evaluates the curvature of 2 vertebrae, and better reflects the cervical curvature. Studies have shown that relative cervical curvature area has good repeatability and diagnostic value, and found that it has a good correlation with common cervical sagittal parameters. The new classification of cervical spine makes up for the disadvantage that the angle classification method cannot distinguish between S-type and RS-type, and initially proposes to use the number of intersections and the relative absolute value area to reflect the severity of S-type.

Quantitatively assessing the effect of cervical sagittal alignment on dynamic intervertebral kinematics by video-fluoroscopy technique

BACKGROUND

Cervical sagittal alignment is crucial for distributing the head load to lower cervical segments and maintaining normal cervical spine function, but its biomechanical effect on the cervical spine was not fully elucidated.

OBJECTIVE

To investigate the effect of cervical sagittal alignment on dynamic intervertebral kinematics.

DESIGN

Cross-sectional study.

METHODS

Healthy participants without neck pain were recruited and divided into lordosis, straight and kyphosis groups according to the C2-C7 Cobb angle at the neutral position. The anti-directional and total joint motions were extracted across 10 epochs of dynamic cervical flexion and extension movements.

RESULTS

/findings: The overall anti-directional joint motion during flexion is larger in the kyphosis group when compared with the lordosis group (p = 0.021), while the range of flexion is smaller in the kyphosis group than that in the lordosis group (p = 0.017). The C2/C3 anti-directional joint motion during extension in the straight group is larger than that in the lordosis group (p = 0016). The range of extension in the kyphosis group (p < 0.001) and the straight group (p = 0.002) are larger than that in the lordosis group. The increased range of extension in the kyphosis and straight groups were mainly from the C3/C4, C4/C5, and C5/C6 joints(p < 0.05).

CONCLUSION

Changes in cervical sagittal alignment alter both the quality and quantity of the individual joint motions. More adjustments are required by the cervical joints to complete neck movements with the loss of lordosis. The lordotic curvature is a relatively effort-saving mode for the cervical spine from a biomechanical perspective.

The Impact of Upper Cervical Spine Alignment on Patient-reported Outcome Measures in Anterior Cervical Decompression and Fusion

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

To determine the extent to which the upper cervical spine compensates for malalignment in the subaxial cervical spine, and how changes in upper cervical spine sagittal alignment affect patient-reported outcomes.

SUMMARY OF BACKGROUND DATA

Previous research has investigated the relationship between clinical outcomes and radiographic parameters in the subaxial cervical spine following anterior cervical discectomy and fusion (ACDF). However, limited research exists regarding the upper cervical spine (occiput to C2), which accounts for up to 40% of neck movement and has been hypothesized to compensate for subaxial dysfunction.

MATERIALS AND METHODS

Patients undergoing ACDF for cervical radiculopathy and/or myelopathy at a single center with minimum 1-year follow-up were included. Radiographic parameters including cervical sagittal vertical axis, C0 angle, C1 inclination angle, C2 slope, Occiput-C1 angle (Oc-C1 degrees), Oc-C2 degrees, Oc-C7 degrees, C1-C2 degrees, C1-C7 degrees, and C2-C7 degrees cervical lordosis (CL) were recorded preoperatively and postoperatively. Delta (Δ) values were calculated by subtracting preoperative values from postoperative values. Correlation analysis as well as multiple linear regression analysis was used to determine relationships between radiographic and clinical outcomes. Alpha was set at 0.05.

RESULTS

A total of 264 patients were included (mean follow-up 20 mo). C2 slope significantly decreased for patients after surgery (Δ=-0.8, P =0.02), as did parameters of regional cervical lordosis (Oc-C7 degrees, C1-C7 degrees, and C2-C7 degrees; P <0.001, <0.001, and 0.01, respectively). Weak to moderate associations were observed between postoperative CL and C1 inclination ( r =-0.24, P <0.001), Oc-C1 degrees ( r =0.59, P <0.001), and C1-C2 degrees ( r =-0.23, P <0.001). Increased preoperative C1-C2 degrees and Oc-C2 degrees inversely correlated with preoperative SF-12 Mental Composite Score (MCS-12) scores ( r =-0.16, P =0.01 and r =-0.13, P =0.04). Cervical sagittal vertical axis was found to have weak but significant associations with Short Form-12 (SF-12) Physical Composite Score (PCS-12) ( r =-0.13, P =0.03) and MCS-12 ( r =0.12, P =0.05).

CONCLUSION

No clinically significant relationship between upper cervical and subaxial cervical alignment was detected for patients undergoing ACDF for neurological symptoms. Upper cervical spine alignment was not found to be a significant predictor of patient-reported outcomes after ACDF.

LEVEL OF EVIDENCE

Level III.

Cervical spine alignment and clinical outcomes after multilevel anterior cervical decompression and fusion with or without plate: A minimal 5-year follow-up of a CONSORT-compliant article

It was reported imperative on cervical sagittal alignment reconstruction after anterior multilevel procedures with self-locked stand-alone cage (SSC) or anterior cage-with-plate (ACP) system multilevel while there was little knowledge about the relationship on cervical alignment and clinical outcomes.To identify the importance of cervical sagittal alignment after 3-level anterior cervical discectomy and fusion on cervical spondylotic myelopathy with SSC and ACP system.Seventy-seven patients with SSC system (SSC group) and 52 cases with ACP system (ACP group) from February 2007 to September 2013 were enrolled with well-matched demographics. Cervical alignment included C2-7 lordosis (CL), operated-segment cervical lordosis (OPCL), upper and lower adjacent-segment cervical lordosis, range of motion of upper and lower adjacent segment at preoperation, immediate postoperation, and the final follow-up. Clinical outcomes contained the neck disability index (NDI), the Japanese Orthopaedic Association (JOA) score, visual analogous scale (VAS) of arm and neck and adjacent segment degeneration (ASD). Patients were then divided into CL improved subgroup (IM subgroup) and non-improved subgroup (NIM subgroup).There were improvements on CL and OPCL in both groups. The change of CL and OPCL larger in ACP group (P < .05) but upper adjacent-segment cervical lordosis/lower adjacent-segment cervical lordosis and range of motion of upper adjacent segment/range of motion of lower adjacent segment were of no significance. NDI, JOA, and VAS got improvement in both groups at immediate postoperation and the final follow-up while ASD was in no difference between SSC and ACP group. A total of 80 patients (39 vs 41) acquired CL improvement with a larger population in ACP group. There were no differences on the rate of ASD, NDI, JOA, VAS, and their change between IM and NIM subgroup. The changes of CL were not correlated to NDI, JOA, VAS, and their change.SSC and ACP group both provide improved OPCL and efficacy on 3-level cervical spondylotic myelopathy with little impact on adjacent segment. The change of CL is not correlated to clinical outcomes.

Analysis and evaluation of the systems used for the assessment of the cervical spine function: a systematic review

Neck injuries and pathologies are widespread and cause disability. Clinicians use different tools to measure the cervical spine' mobility to diagnose different disorders. There are many reliable assessment methods for this purpose, but their benefits have not been deeply investigated and compared, as well as their measurement results. This review aims to summarise the advantages, accuracy, and reliability, of measurement tools and devices used in studies or trails related to the neck and cervical spine evaluation, to evidence the use of inertial sensors and compare them, to highlight the best assessment systems and their characteristics. A literature review has been performed in a range of five years, to obtain information about cervical spine evaluation. Studies that met the established inclusion criteria were selected and classified according their pathology studied, objectives and methodologies followed when evaluating the cervical spine functionality. Studies were described chronologically highlighting the tools employed, where the motion capture systems and cervical range of motion devices stood out as the most used and reliable methods. Cervical spine assessment studies employing systems with inertial sensors as an accurate method, is not evidenced in the sample. However, they are widely tested and different studies validate these systems for their clinical area use, obtaining high reliability and repeatability. Thereby, this review argues that inertial sensors have proven to be a portable, and easy to use tool for the evaluation of neck and its related pathologies, with a great accuracy level.

Impact of cervical sagittal balance and cervical spine alignment on craniocervical junction motion: an analysis using upright multi-positional MRI

PURPOSE

To evaluate the effect of cervical sagittal alignment on craniocervical junction kinematic.

METHODS

We retrospectively reviewed 359 patients (119 cervical lordosis, 38 cervical sagittal imbalances, 111 cervical straight, and 91 cervical kyphosis) who underwent cervical spine multi-positional magnetic resonance imaging (mMRI). The C2-7 angle, disc degeneration grading and cSVA were analyzed in neutral position. The C3-5 OCI, O-C2 angle, and OCD were analyzed in neutral, flexion, and extension position. The Kruskal-Wallis test was used to detect difference among four groups. The post hoc analysis was performed by Mann-Whitney U test.

RESULTS

The cervical sagittal imbalance, cervical straight, and cervical kyphosis groups had significantly more lordosis angle in C3 and C4 OCI and O-C2 angle than the cervical lordosis group (p < 0.0125). Head motion in relation to C2, C3, and C4 (O-C2 angle, C3-4 OCI) in the kyphosis group was significantly greater than in the cervical lordosis group (p < 0.0125). The cervical sagittal imbalance group showed significantly increased O-C2 angle than the cervical lordosis group (p = 0.008). Regression analysis showed that an increase in O-C2 angle by one unit had a relative risk of 4.3% and 3.5% for a patient to be in the cervical sagittal imbalance and cervical kyphosis groups, respectively.

CONCLUSIONS

Cervical sagittal alignment affected craniocervical junction motion with the head exhibiting greater extension and motion in the cervical sagittal imbalance and cervical kyphosis groups. Motion of the head in relation to C2 can be used to predict the cervical sagittal alignment.

Cervical Range of Motion after Anterior Corpectomy and Fusion versus Laminoplasty for Multilevel Cervical Spondylotic Myelopathy: A Three-Dimensional Comparison Based on the Coda Motion System

OBJECTIVE

To compare the change in cervical range of motion (CROM) after the 2 most widely used techniques for multilevel cervical spondylotic myelopathy (CSM): anterior cervical corpectomy and fusion (ACCF) and laminoplasty.

METHODS

Patients with multilevel CSM treated in our hospital between 2014 and 2018 were divided into an ACCF group and a laminoplasty (LAMP) group according to the treatment received. Their demographic data, preoperative and postoperative Japanese Orthopedic Association (JOA) scores, and CROM, measured using the Coda Motion system, were analyzed and compared.

RESULTS

A total of 53 patients were enrolled, including 29 patients in the ACCF group and 24 patients in the LAMP group. Age, sex, duration of follow-up, and preoperative and postoperative JOA scores were comparable in the 2 groups. Compared with preoperative measurements, ACCF group lost an average of 9.8%, 28.5%, 8.9%, 9.9%, 10.6%, and 7.8% of their CROM in flexion, extension, left and right lateral flexion, and left and right rotation, respectively, at the latest follow-up. For the LAMP group, these average losses were 3.5%, 16.4%, 3.2%, 6.3%, 7.0%, and 5.7%, respectively. Thus, the ACCF group exhibited greater average CROM loss than the LAMP group in all directions at the latest follow-up.

CONCLUSIONS

Both ACCF and laminoplasty cause significant CROM loss in patients with multilevel CSM. The laminoplasty technique preserved more CROM than ACCF in all 6 directions after at least 1 year of follow-up. These results can be used when counseling patients undergoing surgery.