Effect of cervical kyphotic deformity type on the motion characteristics and dynamic spinal cord compression

Impact of cervical kyphosis on segmental motion and symptomatic adjacent segment degeneration: a long-term follow-up data of more than 5 years

PURPOSE

This study was performed to assess the impact of cervical kyphosis on the locations of average center of rotation (COR) of each level preoperatively and to investigate whether uncorrected cervical kyphosis increases the incidence of symptomatic adjacent segment degeneration (ASD) after anterior cervical decompression and fusion (ACDF).

METHODS

We retrospectively analyzed all patients surgically treated for cervical myelopathy, radiculopathy, or deformity at a single institution from 2012 to 2018. They were divided into cervical kyphosis and cervical lordosis cohorts. Propensity score matching was performed. Preoperative cervical segmental and postoperative adjacent segment CORs were measured. Development of symptomatic ASD in all patients was assessed after > 5 years of follow-up.

RESULTS

Among 412 patients with cervical lordosis and 47 patients with S-type cervical kyphosis, we established 37 matched pairs before and after surgery. In total, 368 COR locations were measured. Uncorrected kyphosis was identified in seven patients. The CORs of the cervical spine were located farther forward and upward in the cervical kyphosis group than in the control group (p < 0.05). At 1-year visit after ACDF, the locations of the adjacent COR showed no significant differences between the cervical postoperative lordosis group and control group. The incidence of symptomatic ASD was significantly higher in the uncorrected kyphosis group than in the corrected kyphosis group (42.9% vs. 2.5%, p = 0.001) and lordosis group (42.9% vs. 1.9%, p < 0.001).

CONCLUSIONS

Cervical kyphosis can impact the locations of COR and increase the incidence of symptomatic ASD. Kyphosis correction is needed during ACDF in patients with cervical kyphosis.

Differences in cervical sagittal parameters and muscular function among subjects with different cervical spine alignments: a surface electromyography-based cross-sectional study

Background

We analyzed cervical sagittal parameters and muscular function in different cervical kyphosis types.

Methods

This cross-sectional study enrolled subjects with cervical spine lordosis (cervical curvature < -4°) or degenerative cervical kyphosis (cervical curvature > 4°), including C-, S-, and R-type kyphosis. We recorded patients' general information (gender, age, body mass index), visual analog scale (VAS) scores, and the Neck Disability Index (NDI). Cervical sagittal parameters including C2-C7 Cobb angle (Cobb), T1 slope (T1S), C2-C7 sagittal vertical axis (SVA), spino-cranial angle (SCA), range of motion (ROM), and muscular function (flexion-relaxation ratio (FRR) and co-contraction ratio (CCR) of neck/shoulder muscles on surface electromyography). Differences in cervical sagittal parameters and muscular function in subjects with different cervical spine alignments, and correlations between VAS scores, NDI, cervical sagittal parameters, and muscular function indices were statistically analyzed.

Results

The FRR of the splenius capitis (SPL), upper trapezius (UTr), and sternocleidomastoid (SCM) were higher in subjects with cervical lordosis than in subjects with cervical kyphosis. FRRSPL was higher in subjects with C-type kyphosis than in subjects with R- and S-type kyphosis (P < 0.05), and was correlated with VAS scores, Cobb angle, T1S, and SVA. FRRUTr was correlated with NDI, SCA, T1S, and SVA. FRRSCM was correlated with VAS scores and Cobb angle. CCR was correlated with SCA and SVA.

Conclusion

Cervical sagittal parameters differed among different cervical kyphosis types. FRRs and CCRs were significantly worse in R-type kyphosis than other kyphosis types. Cervical muscular functions were correlated with cervical sagittal parameters and morphological alignment.

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.

Do key measurement parameters derived from specific cervical vertebral segments differ between lordotic and non-lordotic cervical spine alignments? A study of asymptomatic young adults

BACKGROUND

Measurement parameters derived from specific cervical vertebral segments (e.g., C2 slope) can provide clinicians with important information on cervical sagittal balance and guide pre- and post-surgical decision-making processes. It is unclear however, what constitutes typical values for these types of measurements in an asymptomatic population of young adults, whether values change depending upon the classification of the cervical spine's global alignment, and if any non-lordotic cervical subtypes display values that are comparable to those reported for pre-surgery patients.

METHODS

Neutral lateral cervical radiographs of 150 asymptomatic participants (18-30 years) were taken. Global cervical alignment was classified as lordotic or one of four non-lordotic subtypes using a multi-method subtyping protocol. Four key measurement parameters - the anterior translation of the head measure (ATHM), C0-C2 angle, C2 slope, and C7 slope - were derived from specific cervical segments. Independent samples t-tests were used to compare lordotic and non-lordotic groups.

RESULTS

There was considerable variation in the four key measurement parameters amongst this asymptomatic population of young adults. Thirty-four percent of the sample were classified as lordotic and 66% were classified as non-lordotic. There was a significant difference (p ≤ 0.0125) between lordotic and non-lordotic groups for the C0-C2 angle, C2 slope and C7 slope. There was no difference between groups for the ATHM (p ≥ 0.0125). Within the non-lordotic group, the global-kyphotic (GK) subtype had the largest mean C2 slope, largest mean C0-C2 angle, and smallest mean C7 slope.

CONCLUSIONS

Long term prospective investigations are required to determine whether possible biomarkers (alignment parameters/radiological measurements) for spinal degenerative changes can be identified so that early interventions can be put in place to try and reduce the impact of neck pain on society.

Determinants of spinal cord stress and strain in degenerative cervical myelopathy: a patient-specific finite element study

Degenerative cervical myelopathy (DCM) is the commonest cause of spinal cord dysfunction in older adults and is characterized by chronic cervical spinal cord compression. Spinal cord stress and strain during neck motion are also known contributors to the pathophysiology of DCM, yet these factors are not routinely assessed for surgical planning. The aim of this study was to measure spinal cord stress/strain in DCM using patient-specific 3D finite element models (FEMs) and determine whether spinal cord compression is the primary determinant of spinal cord stress/strain. Three-dimensional patient-specific FEMs were created for six DCM patients (mild [n = 2], moderate [n = 2] and severe [n = 2]). Flexion and extension of the cervical spine were simulated with a pure moment load of 2 Nm. Segmental spinal cord von Mises stress and maximum principal strain were measured. Measures of spinal cord compression and segmental range of motion (ROM) were included in a regression analysis to determine associations with spinal cord stress and strain. Segmental ROM in flexion-extension and axial rotation was independently associated with spinal cord stress (p < 0.001) and strain (p < 0.001), respectively. This relationship was not seen for lateral bending. Segmental ROM had a stronger association with spinal stress and strain as compared to spinal cord compression. Compared to the severity of spinal cord compression, segmental ROM is a stronger determinant spinal cord stress and strain. Surgical procedures that address segmental ROM in addition to cord compression may best optimize spinal cord biomechanics in DCM.

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.

Imaging and Electrophysiology for Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 9]

STUDY DESIGN

Narrative review.

OBJECTIVE

The current review aimed to describe the role of existing techniques and emerging methods of imaging and electrophysiology for the management of degenerative cervical myelopathy (DCM), a common and often progressive condition that causes spinal cord dysfunction and significant morbidity globally.

METHODS

A narrative review was conducted to summarize the existing literature and highlight future directions.

RESULTS

Anatomical magnetic resonance imaging (MRI) is well established in the literature as the key imaging tool to identify spinal cord compression, disc herniation/bulging, and inbuckling of the ligamentum flavum, thus facilitating surgical planning, while radiographs and computed tomography (CT) provide complimentary information. Electrophysiology techniques are primarily used to rule out competing diagnoses. However, signal change and measures of cord compression on conventional MRI have limited utility to characterize the degree of tissue injury, which may be helpful for diagnosis, prognostication, and repeated assessments to identify deterioration. Early translational studies of quantitative imaging and electrophysiology techniques show potential of these methods to more accurately reflect changes in spinal cord microstructure and function.

CONCLUSION

Currently, clinical management of DCM relies heavily on anatomical MRI, with additional contributions from radiographs, CT, and electrophysiology. Novel quantitative assessments of microstructure, perfusion, and function have the potential to transform clinical practice, but require robust validation, automation, and standardization prior to uptake.

Unexplained back pain and sciatica: the added value of upright dynamic MRI of the lumbar spine in cases of clinical/radiological mismatch

Background

Degenerative disease of the lumbar spine is one of the most prevalent pathologies worldwide, and MRI is the gold standard imaging modality that helps to assess soft tissue and bony abnormalities and elicit causes of neural compression. It is not uncommon in the daily practice to have patients presenting with neurological symptoms during standing or walking while MRI fails to detect lesion that explains their clinical picture. The aim of this study was to detect changes that appear on dynamic weight-bearing MRI of the lumbar spine that was hidden on conventional supine MRI and to correlate them with the clinical situation.

Methodology

Ninety patients with back pain were enrolled in the study, they did conventional and dynamic MRI of the lumbar spine. We compared findings in both modalities as regard alignment, ligamentum flavum buckling, foraminal narrowing and neural compression.

Results

Dynamic MRI showed neural compression in 87% of patients in comparison to supine MRI, ligamentum flavum buckling was reported in 80%, neural foraminal narrowing was seen in 24%, exaggeration of the lumbar lordoisis in 10% and exaggeration of the already existing disc protrusion was documented in 60% of the included patients.

Conclusions

Upright dynamic MRI has added to supine MRI in problem solving cases with clinical radiological mismatch. The results indicated changes in the spine alignment, neural compression and spinal canal stenosis. Since the examination is non-invasive, it could be used in the preoperative planning of patients with degenerative lumbar spine disease.

Cervical Spine Alignment in the Sagittal Axis: A Review of the Best Validated Measures in Clinical Practice

STUDY DESIGN

Review of the best-validated measures of cervical spine alignment in the sagittal axis.

OBJECTIVE

Describe the C2-C7 Cobb Angle, C2-C7 sagittal vertical axis, chin-brow to vertical angle, T1 slope minus C2-C7 lordosis, C2 slope, and different types of cervical kyphosis.

METHODS

Search PubMed for recent technical literature on radiograph-based measurements of the cervical spine.

RESULTS

Despite the continuing use of measures developed many years ago such as the C2-C7 Cobb angle, there are new radiographic parameters being published and utilized in recent years, including the C2 slope. Further research is needed to compare older and newer measures for cross-validation. Utilizing these measures to determine the degree of correction intraoperatively and postoperatively will enable surgeons to optimize patient-level outcomes.

CONCLUSION

Cervical spinal deformity can be a debilitating condition characterized by cervical spinal misalignment that affects the elderly more commonly than young populations. Many of these validated measures of cervical spinal alignment are useful in clinical settings due to their ease of implementation and correlations with various postoperative and health-related quality of life outcomes.

Variation patterns of cervical alignment in ankylosing spondylitis-related thoracolumbar kyphosis following pedicle subtraction osteotomy in the sitting position: an EOS-based investigation

OBJECTIVE

Both unchanged upper cervical lordosis combined with decreased lower cervical lordosis and decreased upper cervical lordosis combined with decreased lower cervical lordosis have been reported to occur after correction surgery for adult spinal deformity. However, variations in cervical alignment after correction surgery in patients with ankylosing spondylitis (AS) have not been investigated. The current study aimed to investigate the variations in cervical alignment following the correction surgery in AS patients with thoracolumbar kyphosis.

METHODS

Patients with AS who underwent pedicle subtraction osteotomy (PSO) for thoracolumbar kyphosis from June 2016 to June 2019 with a minimum of 1-year follow-up were reviewed. Patients were grouped according to the presence (ossified group) and absence (non-ossified group) of total ossification of the anterior longitudinal ligament (ALL) in the lower cervical spine. Radiographic parameters, including thoracolumbar, craniocervical, and global radiographic parameters, were measured on lateral sitting EOS images.

RESULTS

Thirty-two patients (27 males and 5 females) with a mean follow-up of 1.5 years were identified. There were 21 patients in the non-ossified group and 11 patients in the ossified group. After PSO, both groups showed a decrease in the occiput-C7 angle (p < 0.001 for both). In the non-ossified group, the C2-7 angle decreased significantly (p < 0.001), while the occiput-C2 angle remained unchanged (p = 0.570). In the ossified group, the occiput-C2 angle decreased significantly (p < 0.001), while C2-7 angle remained unchanged (p = 0.311). In addition, the change in occiput-C2 was correlated with the osteotomy angle in the ossified group (R = 0.776, p = 0.005).

CONCLUSIONS

The variation patterns of cervical alignment following correction surgery for AS-related thoracolumbar kyphosis were different based on patients with or without total ossification of ALL in the lower cervical spine. When planning PSO for patients in the ossified group, restoration of the physiological upper cervical lordosis angle could be achieved by adjusting the osteotomy angle.

Toward the Development of a Comprehensive Clinically Oriented Patient Profile: A Systematic Review of the Purpose, Characteristic, and Methodological Quality of Classification Systems of Adult Spinal Deformity

BACKGROUND

Existing adult spinal deformity (ASD) classification systems are based on radiological parameters but management of ASD patients requires a holistic approach. A comprehensive clinically oriented patient profile and classification of ASD that can guide decision-making and correlate with patient outcomes is lacking.

OBJECTIVE

To perform a systematic review to determine the purpose, characteristic, and methodological quality of classification systems currently used in ASD.

METHODS

A systematic literature search was conducted in MEDLINE, EMBASE, CINAHL, and Web of Science for literature published between January 2000 and October 2018. From the included studies, list of classification systems, their methodological measurement properties, and correlation with treatment outcomes were analyzed.

RESULTS

Out of 4470 screened references, 163 were included, and 54 different classification systems for ASD were identified. The most commonly used was the Scoliosis Research Society-Schwab classification system. A total of 35 classifications were based on radiological parameters, and no correlation was found between any classification system levels with patient-related outcomes. Limited evidence of limited quality was available on methodological quality of the classification systems. For studies that reported the data, intraobserver and interobserver reliability were good (kappa = 0.8).

CONCLUSION

This systematic literature search revealed that current classification systems in clinical use neither include a comprehensive set of dimensions relevant to decision-making nor did they correlate with outcomes. A classification system comprising a core set of patient-related, radiological, and etiological characteristics relevant to the management of ASD is needed.

CERVICAL SPONDYLOTIC MYELOPATHY: IS A COMBINED APPROACH NECESSARY?

ABSTRACT Objective: Cervical spondylotic myelopathy (CSM) is the main cause of spinal dysfunction in adults. The type of surgical approach to treatment is not well defined in the literature. The objective is to report the results obtained through isolated posterior decompression in patients with a previous indication of the combined approach for the treatment of cervical spondylotic myelopathy. Methods: This is a therapeutic study with level of evidence II, according to the Oxford classification table. Ten patients who underwent isolated posterior approach surgery for the treatment of cervical spondylotic myelopathy were evaluated through imaging and questionnaires (visual analog scale, mJOA-Br scale – Brazilian Portuguese version of the Modified Japanese Orthopedic Association Scale, and Neck Disability Index (NDI)), comparing pre- and postoperative results. Results: Late evaluation of the 10 patients was performed in the period ranging from 24 to 36 months (mean of 30.3 months ± 7.25) following surgery. The comparison of the clinical and radiological parameters in all patients showed a statistical difference in relation to the preoperative scales applied and to the degree of cervical lordosis (p <0.05), evidencing improvement after decompression and posterior fixation of the cervical spine. Conclusions: The isolated posterior approach (decompression, fixation and arthrodesis) allowed the clinical and radiological improvement of patients with cervical spondylotic myelopathy and who had an indication of the complementary anterior approach. Level of evidence II; Retrospective study.

The Impact of Anterior Spondylolisthesis and Kyphotic Alignment on Dynamic Changes in Spinal Cord Compression and Neurological Status in Cervical Spondylotic Myelopathy: A Radiological Analysis Involving Kinematic CT Myelography and Multimodal Spinal Cord Evoked Potentials

STUDY DESIGN

A retrospective study of prospectively collected data.

OBJECTIVE

This study aimed to examine how radiological parameters affect dynamic changes in the cross-sectional area of the spinal cord (CSA) in cervical spondylotic myelopathy (CSM) patients and how they correlate with the severity of myelopathy, by evaluating multi-modal spinal cord evoked potentials (SCEPs).

SUMMARY OF BACKGROUND DATA

Appropriate assessments of dynamic factors should reveal hidden spinal cord compression and provide useful information for choosing surgical procedures.

METHODS

Seventy-nine CSM patients were enrolled. They were examined with kinematic CT myelography (CTM), and the spinal levels responsible for their CSM were determined via SCEP examinations. The C2-7 angle, C2-7 range of motion, and percentage of slip were measured on the midsagittal view during flexion and extension, and the CSA was measured on the axial view in each neck position using kinematic CTM. The patients who exhibited the smallest CSA values during extension and flexion were classified into Groups E and F, respectively.

RESULTS

Fifty-two (65.8%) and 27 (34.2%) cases were included in Groups E and F, respectively. The preoperative JOA score did not differ significantly between the groups; however, the preoperative lower-limb JOA score of Group F was significantly lower than that of Group E (2.24 ± 0.82 vs. 2.83 ± 1.09, P = 0.016). In the multiple logistic regression analysis, a small C2-7 angle during extension (β = 5°, odds ratio: 0.69, 95% confidence interval [CI]: 0.54-0.90) and the slip percentage during flexion (β = 5%, odds ratio: 1.42, 95% CI: 1.09-1.85) were identified as significant predictors of belonging to Group F.

CONCLUSION

Exhibiting more severe spinal cord compression during neck flexion was associated with a small C2-7 angle and anterior spondylolisthesis. The neurological status of the patients in Group F was characterized by severe lower limb dysfunction because of a disturbed blood supply to the anterior column.Level of Evidence: 4.

Feasibility and Safety of Cervical Kinematic Magnetic Resonance Imaging in Patients with Cervical Spinal Cord Injury without Fracture and Dislocation

Objective

To evaluate the feasibility and safety of cervical kinematic MRI (KMRI) in patients with cervical spinal cord injury without fracture and dislocation (CSCIWFD).

Methods

This was a single‐institution case‐only study. Patients with CSCIWFD were enrolled in our institution from February 2015 to July 2019. Cervical radiography and CT were performed first to exclude cervical tumors, and major fracture or dislocation. Then neutral static and kinematic (flexion and extension) MRI was performed for patients who met the inclusion criteria under the supervision of a spinal surgeon. Any adverse events during the KMRI examination were recorded. Patients received surgical or conservative treatment based on the imaging results and patients’ own wishes. The American Spinal Injury Association impairment scale (AIS) grade and the Japanese Orthopedic Association (JOA) score were evaluated on admission, before KMRI examination, and after KMRI examination. For the surgical patients, AIS grade and JOA score were evaluated again 1 week after the operation. The JOA scores were compared among different time points using the paired t‐test.

Results

A total of 16 patients (12 men and 4 women, mean age: 51.1 [30–73] years) with CSCIWFD were included in the present study. Clinical symptoms included facial trauma, neck pain, paraplegia, paresthesia, hyperalgesia, sensory loss or weakness below the injury level, and dyskinesia. On admission, AIS grades were B for 2 cases, C for 5, and D for 9. A total of 14 patients underwent neutral, flexion, and extension cervical MRI examination; 2 patients underwent neutral and flexion examination because they could not maintain the position for a prolonged duration. No patient experienced deterioration of neurological function after the examinations. The AIS grades and JOA scores evaluated post‐examination were similar to those evaluated pre‐examination (P > 0.05) and significantly higher than those on admission (P < 0.05). A total of 12 patients received surgical treatment, 11 of whom underwent anterior cervical discectomy and interbody fusion and 1 underwent posterior C3/4 fusion with lateral mass screws. The remaining 4 patients were offered conservative therapy. None of the patients experienced any complications during the perioperative period. The AIS grade did not change in most surgical patients, except that 1 patient changed from grade C to D 1 week after the operation. The JOA score 1 week after surgery was significantly higher than those on admission and around examination for the surgical patients (P < 0.05).

Conclusion

Cervical KMRI is a safe and useful technique for diagnosis of CSCIWFD, which is superior to static cervical MRI for therapeutic decision‐making in patients with CSCIWFD.

Impact of cervical sagittal parameters on axial neck pain in patients with cervical kyphosis

Background

Cervical sagittal alignment (CSA) is closely related with cervical disk degeneration and impacts the spinal function, especially in the setting of cervical kyphosis (CK). In this study, we evaluated the influence of cervical sagittal parameters on the development of axial neck pain (ANP) in patients with CK.

Methods

Data pertaining to 263 patients with CK who visited the outpatient department of our hospital between January 2012 and December 2018 were retrospective analyzed. The most common symptoms of ANP were neck pain, stiffness, or dullness. Visual analog scale (VAS) was used to evaluate ANP. The following radiographic parameters were evaluated: CK types, C2-7 sagittal vertical axis (SVA), thoracic inlet angle (TIA), T1 slope, neck tilt (NT), cranial tilt, and cervical tilt. Sagittal alignment of CK was classified into 2 types: global and regional type. Multivariate logistic regression analysis was performed to identify risk factors for ANP.

Results

Patients who complained of ANP were categorized as ANP group (VAS score ≥ 3; n = 92), while those without ANP were categorized as non-ANP group (VAS score < 3; n = 171). There was no significant between-group difference with respect to age (P = 0.196), gender (P = 0.516), TIA (P = 0.139), NT (P = 0.676), CK type (P = 0.533), cranial tilt (P = 0.332), cervical tilt (P = 0.585), or cervical disk degeneration (P = 0.695). The T1 slope and C2-7 SVA in the ANP group were significantly greater than that in the non-ANP group (P < 0.05). On multivariate logistic regression, C2-7 SVA [

odds ratio (OR) 2.318, 95% confidence interval 1.373–4.651, P = 0.003) and T1 slope (OR 2.563, 95% CI 1.186–4.669, P = 0.028) were identified as risk factors for ANP.

Conclusions

Our findings suggest a significant effect of cervical sagittal parameters on the occurrence of ANP in patients with CK. Greater T1 slope and larger C2-7 SVA may lead to the development of neck pain.

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.

The morphology of cervical deformities: a two-step cluster analysis to identify cervical deformity patterns

OBJECTIVE

Cervical deformity (CD) is difficult to define due to the high variability in normal cervical alignment based on postural- and thoracolumbar-driven changes to cervical alignment. The purpose of this study was to identify whether patterns of sagittal deformity could be established based on neutral and dynamic alignment, as shown on radiographs.

METHODS

This study is a retrospective review of a prospective, multicenter database of CD patients who underwent surgery from 2013 to 2015. Their radiographs were reviewed by 12 individuals using a consensus-based method to identify severe sagittal CD. Radiographic parameters correlating with health-related quality of life were introduced in a two-step cluster analysis (a combination of hierarchical cluster and k-means cluster) to identify patterns of sagittal deformity. A comparison of lateral and lateral extension radiographs between clusters was performed using an ANOVA in a post hoc analysis.

RESULTS

Overall, 75 patients were identified as having severe CD due to sagittal malalignment, and they formed the basis of this study. Their mean age was 64 years, their body mass index was 29 kg/m2, and 66% were female. There were significant correlations between focal alignment/flexibility of maximum kyphosis, cervical lordosis, and thoracic slope minus cervical lordosis (TS-CL) flexibility (r = 0.27, 0.31, and -0.36, respectively). Cluster analysis revealed 3 distinct groups based on alignment and flexibility. Group 1 (a pattern involving a flat neck with lack of compensation) had a large TS-CL mismatch despite flexibility in cervical lordosis; group 2 (a pattern involving focal deformity) had focal kyphosis between 2 adjacent levels but no large regional cervical kyphosis under the setting of a low T1 slope (T1S); and group 3 (a pattern involving a cervicothoracic deformity) had a very large T1S with a compensatory hyperlordosis of the cervical spine.

CONCLUSIONS

Three distinct patterns of CD were identified in this cohort: flat neck, focal deformity, and cervicothoracic deformity. One key element to understanding the difference between these groups was the alignment seen on extension radiographs. This information is a first step in developing a classification system that can guide the surgical treatment for CD and the choice of fusion level.

McGregor's slope and slope of line of sight: two surrogate markers for Chin-Brow vertical angle in the setting of cervical spine pathology

BACKGROUND CONTEXT

Chin-Brow Vertical Angle (CBVA) is not routinely measured on radiographs even though it is a strong assessor of horizontal gaze.

STUDY DESIGN

Retrospective cohort study of patients with full-body stereoradiographs and a primary cervical diagnosis at the time of presentation.

PURPOSE

Assess the utility of McGregor's Slope (McGS) and Slope of Line of Sight (SLS) as surrogate markers for the CBVA in cervical spine pathology.

METHODS

A retrospective review of patients with full-body stereoradiographs was performed. Patients were ≥18 years of age with a primary cervical diagnosis. Analysis of CBVA, McGS, and SLS was conducted as markers of horizontal gaze. Sagittal alignment was characterized by: pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), T1-pelvic angle (TPA), sagittal vertical axis (SVA), T2-T12 thoracic kyphosis, C2-C7 SVA (cSVA), C2-C7 Cervical lordosis, T1-Slope minus Cervical Lordosis (TS-CL), and C2-Slope (C2S). A subgroup analysis was performed in patients with cervical deformity. Independent sample t tests and paired t tests compared radiographic alignment. Pearson correlations characterized linear relationships. Linear regression analysis identified relationships between the parameters.

RESULTS

In all, 329 patients were identified with primary cervical spine diagnoses. Chin-Brow Vertical Angle was visible in 171 patients (52.0%), McGS in 281 (85.4%), and SLS in 259 (78.7%). Of the 171 patients with visible CBVA, the mean CBVA was 2.30±7.7, mean McGS was 5.02±8.1, and mean SLS was -1.588±2.03. Chin-Brow Vertical Angle strongly correlated with McGS (r=0.83) and SLS (r=0.89) with p<.001. McGregor's Slope positively correlated with SLS (r=0.89, p=.001).

CONCLUSIONS

This study demonstrates that McGS and SLS serve as strong, positive correlates for CBVA. The reported mean differences between these measurements provide a useful conversion, broadening CBVA's use as a radiographic assessment of horizontal gaze.

Multivariate analysis of poor outcome after anterior surgery in multilevel cervical spondylotic myelopathy patients with heterotopic ossification and preoperative kyphotic alignment

Objective

The aim of this study was to evaluate the risk factors for poor outcome in patients who underwent multi-segmental anterior surgery, and analyze postoperative complications.

Methods

We retrospectively reviewed 158 patients after anterior surgery due to multilevel cervical spondylotic myelopathy (m-CSM) between June 2008 and June 2016. Adjusted ORs and 95% CIs were determined by multivariate logistic regression analysis. Cutoff values and the area under the curve for continuous risk factors were calculated through receiver operating characteristic curve analysis. The chi-squared test was performed for the comparison of complications among the three surgical groups.

Results

By analyzing 105 patients with good outcome and 53 patients with poor outcome, we established that the risk factors for poor outcome were advanced age (OR =1.12, P=0.003), longer duration of symptoms (OR =1.07, P=0.028), and bigger kyphotic angle at final follow-up (OR =1.29, P< 0.001). The optimal cutoff values for age, duration of symptoms, and kyphotic angle at final follow-up were 63.1 years, 15.5 months, and 5.3 angle. Postoperative complications occurred in 21 patients (13.3%). The incidence of dysphagia and cerebrospinal fluid leakage were higher in multilevel anterior cervical discectomy and fusion (m-ACDF) group than in other groups (P< 0.05).

Conclusion

Advanced age, longer duration of symptoms, and bigger kyphotic angle at final follow-up were the risk factors for poor postoperative outcome in patients with m-CSM. The complications after hybrid approach and m-ACDF approach were less than after anterior cervical corpectomy and fusion approach.

The most appropriate cervical vertebra for the measurement of occipitocervical inclination parameter: a validation study of C3, C4, and C5 levels using multi-positional magnetic resonance imaging

PURPOSE

To evaluate which cervical level is the most appropriate level to measure occipitocervical inclination (OCI).

METHODS

Sixty-two patients with multi-positional MRI: 24 males and 38 females, who had cervical lordosis and had a disk degeneration grade of 3 or less were included. We measured patient's OCI at C3, C4, and C5, occipitocervical angle (OCA), occipitocervical distance (OCD), C2-7 angle, and cervical sagittal vertical axis (cSVA) in neutral, flexion, and extension position. The correlation between OCI and OCA, OCD, C2-7 angle, and cSVA on each cervical level in all three positions was tested using Pearson's correlation coefficient test. The difference between OCIs at each cervical level was tested by Wilcoxon signed-rank test. p value of less than 0.05 was set as a statistically significant level.

RESULTS

C5 OCI showed statistically significant correlation with OCA, OCD, C2-7 angle, and cSVA in all three positions (p < 0.05, r = 0.214-0.525). C3 OCI in flexion (p = 0.393, r = 0.081) and C4 OCI in neutral and flexion (neutral p = 0.275, r 0.104; flexion p = 0.987, r = 0.002) did not show significant correlation with C2-7 angle. There was a statistically significant difference between C3, C4, and C5 OCIs in neutral and extension position (p < 0.05). At the same time, OCI showed statistically strong correlation between adjacent cervical levels (p < 0.001, r = 0.627-0.822).

CONCLUSION

C5 cervical level is the most appropriate level for OCI measurement. OCI should be measured at the same cervical level at all time. C4 OCI can reliably substitute C5 OCI in case C5 which is invisible on radiographic image. These slides can be retrieved under Electronic Supplementary Material.

Changes in the Sagittal Cranio-Cervical Posture Following a 12-Week Intervention Using a Simple Spinal Traction Device

STUDY DESIGN

Non-controlled clinical trial.

OBJECTIVE

To assess the efficacy of a simple home spinal traction device on sagittal cranio-cervical posture and related symptoms.

SUMMARY OF BACKGROUND DATA

Forward head protraction (FHP) and cranio-cervical malalignment were shown to be consequential in the development adverse musculoskeletal radiographic findings and symptoms in that region.

METHODS

Participants (n = 13, 18-36-year-old) were drawn from a mildly symptomatic population, all presented with cranio-cervical malalignment and considerable FHP. Participants used a simple home spinal traction device for 12 weeks, 10 min/d. Sagittal cervical radiographs and the SF36 health survey were obtained pre/post intervention and guideline compliance was recorded. Radiographic evaluation included typical measurements of sagittal cranio-cervical alignment and FHP (e.g., atlas plane line, vertical axis line, sagittal cranial angle, absolute rotation angle). Standard paired samples t tests, chi-squared, and effect size analyses were used to assess pre- and post-intervention changes.

RESULTS

Each of the key radiographic variables recorded significant moderate to very large positive changes as a result of the intervention. Similarly, Chi-squared analyses indicated that saggital cervical spine configuration tended to become more lordotic (P = 0.007), with four participants shifting from a kyphotic to a lordotic presentation. SF36 health survey data demonstrated mostly significant positive changes throughout all tested domains, and moderate positive changes were recorded across all radiographic cranio-cervical mesured paramenters (e.g., decreased FHP, increased cervical lordosis, and cranial extention). Participants indicated high level of protocol compliance.

CONCLUSION

This study has demonstrated that the unsupervised daily use of a simple home spinal traction device (Thoracic Pillow) proved effective in bringing positive plastic changes to the sagittal cranio-cervical alignment and reduction in symptoms in the tested population during a short intervention period.

LEVEL OF EVIDENCE

3.

High risk twin pregnancy complicated with severe rachiterata and huge dorsal mass suffering from refractory infection: A case report

RATIONALE

Severe rachiterata is rarely described as a complication of pregnancy, and it was assumed as a contraindication to pregnancy. We first report a case of severe spinal deformity associated both with scoliosis and kyphosis in pregnancy.

PATIENT CONCERNS

A 38-year-old pregnant woman [28+1 weeks of twin pregnancy, gravida 3, para 2 (G3P2)] was admitted to the emergency department with complaints of persistent productive cough, with increased expectoration, dyspnea, dizziness, fatigue, and irregular abdominal pain. She had obvious spinal protrusion of lateral bending deformity and kyphosis with "S" type distortion, and had a huge dorsal mass with refractory infection. In the third trimester of pregnancy, the anatomical changes resulted in thoracic cavity deformation, unmanageable pulmonary infections, and serious skin infections on the surface of the dorsal mass.

DIAGNOSIS

Single chorionic twin pregnancy with severe rachiterata and a huge dorsal mass.

INTERVENTIONS

Management was focused on treating pulmonary and skin infections and promoting fetal lung maturation. Appropriate timing of pregnancy termination and manner of delivery were decided through a multidisciplinary discussion. The patient was placed in a special position and assisted by a professional midwife during delivery.

OUTCOMES

The patient and her children survived after careful care and treatment.

LESSONS

Severe spinal deformities are not contraindications for pregnancy, but the changes in the thoracic cavity caused by these deformities can result in respiratory function decline, which becomes more apparent in the third trimester, which could likely cause pulmonary infection that is difficult to treat. In the future, studies investigating prenatal care procedures, timing of pregnancy termination, and appropriate delivery method are warranted.

Can C2-6 Cobb Angle Replace C2-7 Cobb Angle?: An Analysis of Cervical Kinetic Magnetic Resonance Images and X-rays

STUDY DESIGN

Retrospective study of consecutive 113 cervical kinetic magnetic resonance images (kMRIs) and 57 radiographs.

OBJECTIVE

To elucidate the relationship between C2-6 or C2-7 Cobb angle and cervical sagittal alignment parameters using kMRI, and evaluate the visibility of C6 and C7 inferior endplates on cervical radiographs.

SUMMARY OF BACKGROUND DATA

Several studies have used C2-6 Cobb angle instead of C2-7 Cobb angle as C7 inferior endplate is not always visible because of overlying shadows. However, the relationship between C2-6 or C2-7 Cobb angle and cervical sagittal alignment parameters remains unclear. Moreover, visibility of C6 inferior endplate remains unknown.

METHODS

C2-6 Cobb angle, C2-7 Cobb angle, occiput-C2 angle, Atlas-dens interval (ADI), narrowest oropharyngeal airway space (nPAS), cervical sagittal vertical axis (cSVA), cervical tilt, cranial tilt, neck tilt, thoracic inlet angle (TIA), and T1 slope were measured using kMRI, and analyzed for their relationship with C2-6 or C2-7 Cobb angle. Visibility rates of C6 or C7 inferior endplates were evaluated using cervical radiographs.

RESULTS

Linear regression analysis showed high association between C2-6 and C2-7 Cobb angle (R = 0.696, P < 0.01). C2-6 Cobb angle was significantly correlated with occiput-C2 angle, TIA, T1 slope, neck tilt, cSVA, and cervical tilt; but not with nPAS, ADI, and cranial tilt. C2-7 Cobb angle resembled C2-6 Cobb angle regarding the relationships with other parameters. In our study, 94.7% C6 and 50.9% C7 inferior endplate were clearly visible; 1.8% C6 and 24.6% C7 inferior endplate were invisible. Chi-square test and residual analysis showed significant difference between the two groups (P < 0.01).

CONCLUSION

C2-6 Cobb angle highly resembled C2-7 Cobb angle regarding its relationships with parameters of craniovertebral, cervical and thoracic inlet alignment. C2-6 Cobb angle could be an alternative to C2-7 Cobb angle because of its significantly higher visibility rate.

LEVEL OF EVIDENCE

3.

Dynamic Cervical Cord Compression Post-laminectomy Visualized by Flexion-extension Magnetic Resonance Imaging: Case Report

Flexion-extension magnetic resonance imaging (MRI) in the cervical spine is not universally used in cervical spine surgery. However, flexion-extension MRIs can identify previously undetected spinal stenosis, improve surgical decision-making, and maybe a better tool to evaluate postoperative outcomes. One uncommon complication after laminectomy, to treat cervical spinal stenosis, is muscle weakness due to subsequent dynamic cord compression by posterior paraspinal musculature. We present a case of a 41-year-old male who underwent posterior cervical decompression and developed subsequent neurological deficits and muscle weakness. MRI with neutral cervical positioning did not show spinal stenosis necessitating surgical intervention. However, given the patient’s increasing tetraparesis, flexion-extension MRI was performed and it revealed significant spinal stenosis in both flexion and extension positions due to spondylosis and compression from paraspinal muscles. This case demonstrates the utility of flexion-extension MRI in identifying pathologies such as cord compression by paraspinal muscles. Exclusive use of a neutral-position MRI scan may not be sufficient to provide proper diagnoses for cervical spine pathologies. Flexion-extension MRI should be considered when the degree of neurological symptoms outweighs minimal or absent pathology seen on neutral-position sagittal MRI.

Strain behavior of malaligned cervical spine implanted with metal-on-polyethylene, metal-on-metal, and elastomeric artificial disc prostheses - A finite element analysis

BACKGROUND

Postoperative alterations in cervical spine curvature (i.e. loss of lordotic angle) are frequently observed following total disc replacement surgery. However, it remains unclear whether such changes in lordotic angle are due to preoperative spinal deformities and/or prostheses design limitations. The objective of the study is to investigate strain and segmental biomechanics of the malaligned cervical spine following total disc replacement.

METHODS

Three disc prostheses were chosen, namely a metal-on-polyethylene, a metal-on-metal, and an elastomeric prosthesis, which feature different geometrical and material design characteristics. All discs were modelled and implanted into multi-segmental cervical spine finite element model (C3-C7) with normal, straight and kyphotic alignments. Comparative analyses were performed by using a hybrid protocol.

FINDINGS

The results indicated that as the spine loses lordotic alignment, the prosthesis with elastomeric core tends to produce significantly larger flexion range of motion (difference up to 6.1°) than metal-on-polyethylene and metal-on-metal prostheses. In contrast, when the treated spine had normal lordotic alignment, the range of motion behaviors of different prostheses are rather similar (difference within 1.9°). Large localized strains up to 84.8% were found with the elastomeric prosthesis, causing a collapsed anterior disc space under flexion loads.

INTERPRETATION

Changes in cervical spinal alignments could significantly affect the surgical-level range of motion behaviors following disc arthroplasty; the in situ performance was largely dependent on the designs of the artificial disc devices in particular to the material properties.

Kinematic evaluation of thoracic spinal cord sagittal diameter and the space available for cord using weight-bearing kinematic magnetic resonance imaging

STUDY DESIGN

Retrospective kinematic MRI (kMRI) study.

OBJECTIVE

To evaluate the dynamic changes of thoracic anterior and posterior space available for cord (SAC), and thoracic spinal cord in the dural sac in three positions.

SETTING

Expert MRI, Bellflower California; and University of Southern California, in Los Angeles, USA.

METHODS

A total of 118 patients (66 males and 52 females, mean age ( ± SD) of 45.6 ± 10.6 years) who underwent thoracic spine kMRI were evaluated from T4-5 to T11-12 in flexion, neutral, and extension positions. The anterior SAC, posterior SAC, and mid-sagittal thoracic cord diameter were measured at each level from T4-5 to T11-12. Inter- and intraobserver agreements were analyzed.

RESULTS

The anterior SAC was significantly narrower in flexion position compared with other positions at T8-9 to T11-12 levels (p < 0.01). The T8-9 level had significantly wider posterior SAC in flexion and extension positions compared with the neutral position (p < 0.005). However, the posterior SAC at T9-10 was narrower in extension than the neutral position (p = 0.002). Thoracic spinal cord diameter significantly increased in flexion position when compared with the neutral position at T8-9, T9-10, and T11-12 levels (p < 0.005).

CONCLUSIONS

Thoracic spinal cord had dynamic changes with positions. In flexion position, the thoracic cord at T8-9 and below tended to move anteriorly, getting closer to the vertebral body and intervertebral disc. The mid-sagittal diameter of the thoracic cord increased in flexion position at the levels below T8-9. In the presence of lesions in anterior epidural space, the risk of spinal cord compression is higher in flexion position, especially at levels below T8-9.

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

STUDY DESIGN

Retrospective study.

OBJECTIVE

To evaluate how each type of sagittal cervical alignment affects the motion of the upper and subaxial cervical spine using kinematic magnetic resonance imaging.

SUMMARY OF BACKGROUND DATA

The sagittal malalignment of the cervical spine from degeneration in the subaxial cervical spine reflects a disruption in the kinematic properties of the cervical spine and affects the motion of adjacent segments. Changes in the sagittal parameters and kinematics of the upper cervical spine and upper thoracic spine due to the kyphosis are unknown.

METHODS

Kinematic magnetic resonance imaging of the cervical spine in neutral position from 311 patients, including 90 lordotic, 90 straight, 90 global kyphotic, and 41 segmental kyphotic were analyzed. The lordotic angle at the upper and lower cervical spine, and T1 slope were measured in the neutral position and again in flexion and extension for dynamic analysis.

RESULTS

The number of levels with significant disk degeneration was higher in the global kyphosis group. In the global kyphosis group, neutral sagittal parameters showed some characteristics of compensation to the malalignment. Compared with the lordotic group, patients with global kyphosis demonstrated significantly higher lordotic angle of the upper cervical spine and more horizontal T1 slope. The dynamic evaluation showed greater range of motion of the entire cervical spine and subaxial cervical spine in younger patients. However, we still found greater range of motion of the occipito-atlanto-axial complex in global kyphosis, even when controlling for age and number of levels with significant disk degeneration.

CONCLUSION

Sagittal malalignment of the cervical spine affects all parts of the cervical motion complex. The global kyphotic alignment of subaxial cervical spine affects the kinematic properties of the occipito-atlanto-axial complex and upper thoracic spine to compensate for the alteration of cervical alignment. These differences are not seen in straight and segmental kyphosis.

LEVEL OF EVIDENCE

Level 3.

Dynamic MRI in the evaluation of the spine: state of the art

INTRODUCTION

Degenerative disease of the spine is a generic term encompassing a wide range of different disease processes, which leads to spinal instability; traumatic/neoplastic events can accelerate this aging process. Therefore, the dynamic nature of the spine and its mobility across multiple segments is difficult to depict with any single imaging modality.

METHODS

A review of PubMed databases for articles published about kMRI in patients with cervical and lumbar spinal desease was performed. We focused on the physiopathological changes in the transition from supine to upright position in spine instability.

DISCUSSION

Until a few years ago, X-ray was the only imaging modality for the spine in the upright position. Of the imaging techniques currently available, MRI provides the greatest range of information and the most accurate delineation of soft-tissue and osseous structures. Conventional MRI examinations of the spine usually are performed in supine position, in functional rest, but the lumbar spine instability is often shown only by upright standing. This can result in negative findings, even in the presence of symptoms. Regardless, the final result is distorted. To overcome this limitation, Kinetic MRI (kMRI) can image patients in a weight-bearing position and in flexed and extended positions, thus revealing abnormalities that are missed by traditional MRI studies.

CONCLUSION

Despite some limitations, the upright MRI can be a complementary investigation to the traditional methods when there are negative results in conventional MRI in symptomatic patients or when surgical therapy is scheduled.

Incidence and risk factors of poor clinical outcomes in patients with cervical kyphosis after cervical surgery for spinal cord injury

Objective

This retrospective study investigated the incidence and risk factors of poor clinical outcomes after cervical surgery for cervical spinal cord injury in a large population of patients with global or segmental cervical kyphosis.

Methods

The clinical and radiological evaluation results of 269 patients with cervical kyphosis who underwent either anterior or posterior surgery between 2008 and 2013 were collected, preoperatively and at each follow-up after surgery.

Results

All patients were followed for an average of 2.5 years. Outcomes were classified as good or poor (n=156 and 113 patients, respectively), based on the Japanese Orthopedic Association (JOA) recovery ratios. The rates of patients with good or poor outcomes were statistically comparable with regard to gender ratio, type of injury, history of diabetes or cardiovascular disease, interval between injury and surgery, and follow-up time. The multivariate logistic regression analysis indicated that the following were independent predictors of poor improvement: patient age (P=0.016, odds ratio [OR] =1.0261); preoperative JOA scores (P=0.003, OR =0.1932); and cervical instability (P=0.004, OR =2.1562).

Conclusion

This study showed that advanced age, low preoperative JOA score, and cervical instability are closely associated with a poor surgical outcome in patients with cervical kyphosis. However, these results do not suggest that the type of cervical kyphosis influences the clinical outcome of surgery.

Space Available for Cord, Motion, and disc degeneration at the adjacent segments level of degenerative cervical spondylolisthesis using kinematic MRI

The objective was to evaluate motion, disc degeneration and Space Available for Cord (SAC) at the adjacent segments of degenerative cervical spondylolisthesis (DCS) using kinematic Magnetic Resonance Imaging (kMRI). The cervical spine kMRI of sixty-one DCS spinal levels (38 anterolisthesis and 23 retrolisthesis) were analyzed at the listhesis level and its adjacent segments in three position using kMRI. MRAnalyzer3 was used to analyze translation, angular motion and SAC. The caudad level had significantly less translation motion than the listhesis level in overall DCS or grade 2 anterolisthesis group (P<0.05). The cephalad level had significant more translational motion than the caudad level in overall DCS or grade 1 retrolisthesis group (P<0.05). For disc degeneration, the cephalad level had the least disc degeneration and showed significant difference with the listhesis level in overall DCS or overall anterolisthesis or overall retrolisthesis or grade 2 anterolisthesis or grade 1 or 2 retrolisthesis (P<0.05). For SAC, the listhesis level had the narrowest space in overall DCS groups. In neutral position, grade 1 anterolisthesis had significantly larger SAC at the listhesis and the cephalad level than grade 1 retrolisthesis (P<0.05). In conclusion, DCS affected cervical spine motion and kinematics. Grade 1 retrolisthesis showed tendency of narrower SAC at the cephalad level more than the same grade anterolisthesis. The likelihood of the adjacent segment disease and spinal cord compression are higher in both grade 2 anterolisthesis and retrolisthesis.

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.

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

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

The efficacy of sagittal cervical spine subtyping: Investigating radiological classification methods within 150 asymptomatic participants

Aims:

The aim of this study is to (1) compare and contrast cervical subtype classification methods within an asymptomatic population, and (2) identify inter-methodological consistencies and describe examples of inconsistencies that have the potential to affect subtype classification and clinical decision-making.

Methods:

A total of 150 asymptomatic 18–30-year-old participants met the strict inclusion criteria. An erect neutral lateral radiograph was obtained using standard procedures. The Centroid, modified Takeshima/Herbst methods and the relative rotation angles in cases of nonagreement were used to determine subtype classifications. Cohen's kappa coefficient (κ) was used to assess the level of agreement between the two methods.

Results:

Nonlordotic classifications represented 66% of the cohort. Subtype classification identified the cohort as, lordosis (51), straight (37), global kyphosis (30), sigmoidal (13), and reverse sigmoidal (RS) (19). Cohen's kappa coefficient indicated that there was only a moderate level of agreement between methods (κ = 0.531). Methodological agreement tended to be higher within the lordotic and global kyphotic subtypes whereas, straight, sigmoidal, and RS subtypes demonstrated less agreement.

Conclusion:

This is the first study of its type to compare and contrast cervical classification methods. Subtypes displaying predominantly extended or flexed segments demonstrated higher levels of agreement. Our findings highlight the need for establishing a standardized multi-method approach to classify sagittal cervical subtypes.

Influence of T1 Slope on the Cervical Sagittal Balance in Degenerative Cervical Spine: An Analysis Using Kinematic MRI

STUDY DESIGN

A retrospective kinematic magnetic resonance imaging (kMRI) study.

OBJECTIVE

To evaluate the utility of kMRI in determining the relationship between cervical sagittal balance and TI alignment.

SUMMARY OF BACKGROUND DATA

Thoracic inlet parameters play an important role in cervical spine sagittal balance. However, most of the literature is based on lower resolution cervical X-rays or CT scans in the supine position.

METHODS

Cervical spine kMRI of 83 patients with degenerative cervical spine conditions (20-68 yr of age) was analyzed for: (1) cervical spine parameters: C2-C7 angle, C2-C7 sagittal vertical axis (SVA), cranial tilt, and cervical tilt; and (2) T1 parameters: thoracic inlet angle (TIA), T1 slope, and neck tilt (NT). Multiple logistic regression analysis and Pearson correlation coefficients were performed.

RESULTS

The mean TIA, T1 slope, and NT were 78.0, 33.2, and 44.8°, respectively. The mean C2-7 angle, SVA of C2-C7, cervical tilt, and cranial tilt were -15.4°, 22.0 mm, 18.1°, and 15.1°, respectively. The ratio of cervical:cranial tilt was maintained as 55:45%. A significant correlation was found between the C2-C7 angle and T1 slope (r = 0.731), TIA and C2-C7 angle (r = 0.406), cervical tilt with C2-C7 angle (r = 0.671), T1 slope with TIA (r = 0.429), TIA with neck tilt (r = 0.733), TIA with cervical tilt (r = 0.377), SVA C2-C7 with cervical tilt (r = -0.480), SVA C2-C7 with cranial tilt (r = 0.912), and C2-7 SVA with the ratio of cranial tilt to cervical tilt (r = 0.694).

CONCLUSION

An individual with a large T1 slope required large cervical lordosis to preserve physiologic sagittal balance of the cervical spine. Cranial tilt was the cervical parameter most strongly correlated with SVA C2-C7, and thus may be a good parameter to assess decompensation of cervical sagittal balance.

LEVEL OF EVIDENCE

3.

Kinetic magnetic resonance imaging analysis of spinal degeneration: a systematic review

OBJECTIVE

To evaluate the clinical use of kinetic magnetic resonance imaging (kMRI) in spinal degenerative diseases.

METHODS

A systematic search of PubMed, EMBASE and ISI databases for articles that had been published between January 1978 and February 2013 concerning patients who had undergone kMRI for spinal problems was performed. All selected patients had undergone kMRI in neutral, flexion, and extension weight-bearing positions. Evaluation of cervical and lumbar degeneration by kMRI was analyzed. kMRI showed significant reduction of mobility in cervical segments of patients with severe disc degeneration; in addition, it was more severely reduced in patients with severe cord compression than in those without it. In the cervical spine, it was found that although disc height, translational motion, and angular variation were significantly affected at the level of disc herniation, no significant changes were apparent in adjacent segments. kMRI also showed that lumbar degeneration is closely associated with disc degeneration, facet joint osteoarthritis and the pathological characteristics of the interspinous ligaments, ligamentum flavum and paraspinal muscles.

RESULTS

Eleven articles (4162 patients) fulfilled the inclusion criteria and were reviewed. It was found that kMRI is more specific and sensitive than conventional MRI regarding relating patients' symptoms to objective findings on imaging that demonstrate pathology and biomechanics. In the kinetic position, kMRI improves detection of disc herniation by 5.78%-19.46% and thus provides a new means of studying the biomechanical mechanism(s) in degenerative spines.

CONCLUSION

Kinetic MRI is effective for diagnosing, evaluating, and managing degenerative disease within the spine; however, it still has some limitations.

The evaluation of cervical spine mobility without significant spondylosis by kMRI

STUDY DESIGN

Retrospective analysis of kinetic magnetic resonance images (kMRI).

OBJECTIVE

To analyse the kinematics of cervical spine inpatients without significant spondylosis and to understand the normal movement of the cervical spine as reference for future comparison.

SUMMARY OF BACKGROUND DATA

Although some studies have been conducted to describe the normal mobility of the cervical spine, prior studies did not establish a relationship between the kinematics of cervical spine and disc degeneration. Only a few studies of the kinematics of the non-degenerated cervical spine have been reported; however, they focused on single level and not all the levels of cervical spine.

METHODS

468 symptomatic patients underwent upright cervical kMRI, and cervical disc degeneration was evaluated with a new grading system. This grading system consists of four grades (0-III), and the cervical spines with grade 0 and grade I discs were included in this study. Finally, 61 symptomatic patients were studied 34 male and 27 female with an average age of 41.9 years. kMRI was used to define the normal mobility of the cervical spine by calculating the translation motion, angular variation and percentage angular contribution to the total cervical spine.

RESULTS

The translation motion of the cervical spine at each level was 0.85 ± 1.22 mm at C2/3, 1.05 ± 1.19 mm at C3/4, 0.63 ± 1.19 mm at C4/5, 0.57 ± 0.91 mm at C5/6, 0.16 ± 0.86 mm at C6/7 and -0.11 ± 0.81 at C7/T1. In general, the translation motion decreased from proximal segment to distal segment. The angular variation of the cervical spine at each level was 5.58 ± 3.86° at C2/3, 8.26 ± 4.81° at C3/4, 9.11 ± 4.87° at C4/5, 10.05 ± 5.26° at C5/6, 8.31 ± 4.30° at C6/7 and 4.87 ± 3.28° at C7/T1. The angular variation at C2/3 and C7/T1 was significantly lower compared to other levels (P < 0.05). The contribution of each cervical level to the total angular mobility of cervical spine was the greatest at C5/6 (21.68 ± 10.31%) and least at C7/T1 (11.11 ± 7.60%) (P < 0.05).

CONCLUSION

This study demonstrates the normal cervical segmental mobility for the entire cervical spine using kMRI. These results will be helpful to understand the normal mobility of the cervical spine and for understanding the relationship between kinematics of the cervical spine and disc degeneration for future comparisons.

Degenerative Cervical Myelopathy: Epidemiology, Genetics, and Pathogenesis

STUDY DESIGN

Review.

OBJECTIVE

To formally introduce "degenerative cervical myelopathy" (DCM) as the overarching term to describe the various degenerative conditions of the cervical spine that cause myelopathy. Herein, the epidemiology, pathogenesis, and genetics of conditions falling under this hypernym are carefully described.

SUMMARY OF BACKGROUND DATA

Nontraumatic, degenerative forms of cervical myelopathy represent the commonest cause of spinal cord impairment in adults and include cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, and degenerative disc disease. Unfortunately, there is neither a specific term nor a specific diagnostic International Classification of Diseases, Tenth Revision code to describe this collection of clinical entities. This has resulted in the inconsistent use of diagnostic terms when referring to patients with myelopathy due to degenerative disease of the cervical spine.

METHODS

Narrative review.

RESULTS

The incidence and prevalence of myelopathy due to degeneration of the spine are estimated at a minimum of 41 and 605 per million in North America, respectively. Incidence of cervical spondylotic myelopathy-related hospitalizations has been estimated at 4.04/100,000 person-years, and surgical rates seem to be rising. Pathophysiologically, myelopathy results from static compression, spinal malalignment leading to altered cord tension and vascular supply, and dynamic injury mechanisms. Occupational hazards, including transportation of goods by weight bearing on top of the head, and other risk factors may accelerate DCM development. Potential genetic factors include those related to MMP-2 and collagen IX for degenerative disc disease, and collagen VI and XI for ossification of the posterior longitudinal ligament. In addition, congenital anomalies including spinal stenosis, Down syndrome, and Klippel-Feil syndrome may predispose to the development of DCM.

CONCLUSION

Although DCMs can present as separate diagnostic entities, they are highly interrelated, frequently manifest concomitantly, present similarly from a clinical standpoint, and seem to be in part a response to compensate and improve stability due to progressive age and wear of the cervical spine. The use of the term "degenerative cervical myelopathy" is advocated.

LEVEL OF EVIDENCE

5.