Risk factors for missed dynamic canal stenosis in the cervical spine

Dynamic Cervical Spinal Canal Stenosis: Identifying Imaging Risk Factors in Extended Positions

STUDY DESIGN

A retrospective study at a single academic institution.

PURPOSE

This study aimed to identify imaging risk factors for stenosis in extended neck positions undetectable in preoperative neutral magnetic resonance imaging (MRI) and improving decompression strategies for cervical spine disorders.

OVERVIEW OF LITERATURE

Cervical disorders are influenced by various dynamic factors, with spinal stenosis appearing during neck extension. Despite the diagnostic value of dynamic cervical MRI, standard practice often uses neutral-position MRI, potentially influencing surgical outcomes.

METHODS

This study analyzed 143 patients who underwent decompression surgery between 2012 and 2014, who had symptomatic cervical disorders and MRI evidence of spinal cord or nerve compression but had no history of cervical spine surgery. Patient demographics, disease type, Japanese Orthopedic Association score, and follow-up periods were recorded. Spinal surgeons conducted radiological evaluations to determine stenosis levels using computed tomography myelography or MRI in neutral and extended positions. Measurements such as dural tube and spinal cord diameters, cervical alignment, range of motion, and various angles and distances were also analyzed. The residual space available for the spinal cord (SAC) was also calculated.

RESULTS

During extension, new stenosis frequently appeared caudal to the stenosis site in a neutral position, particularly at C5/C6 and C6/C7. A low SAC was identified as a significant risk factor for the development of new stenosis in both the upper and lower adjacent disc levels. Each 1-mm decrease in SAC resulted in an 8.9- and 2.7-fold increased risk of new stenosis development in the upper and lower adjacent disc levels, respectively. A practical SAC cutoff of 1.0 mm was established as the threshold for new stenosis development.

CONCLUSIONS

The study identified SAC narrowing as the primary risk factor for new stenosis, with a clinically relevant cutoff of 1 mm. This study highlights the importance of local factors in stenosis development, advocating for further research to improve outcomes in patient with cervical spine disorders.

Favorable cervical extension capacity preventing loss of cervical lordosis after laminoplasty due to spontaneous restoration of initial lordosis

BACKGROUND CONTEXT

Cervical laminoplasty is a common approach for the treatment of multilevel cervical spondylotic myelopathy (CSM). Postoperative loss of cervical lordosis (LCL) was associated with lower extension motion of the cervical spine before laminoplasty.

PURPOSE

To analyze the possible causes of preoperative cervical extension capacity affecting LCL after laminoplasty by evaluating the changes in cervical lordosis (CL) at different stages.

STUDY DESIGN/SETTING

Retrospective study.

PATIENT SAMPLE

Seventy-two patients undergoing laminoplasty due to multilevel CSM.

OUTCOME MEASURES

Radiographic parameters included CL, extension CL (eCL), flexion CL (fCL), range of motion (ROM), extension ROM (eROM), flexion ROM (fROM) and LCL. Clinical outcomes were assessed using the Japanese Orthopedic Association (JOA) and neck disability index (NDI) score.

METHODS

The data were recorded before surgery and at 3- and 24-month follow-up. All patients completed a cervical extension test preoperatively. A receiver operating characteristic (ROC) curve of eROM was constructed to discriminate the patients with and without postoperative kyphotic deformity.

RESULTS

According to the optimal cut-off value of eROM, the patients were divided into two groups: extension group (eROM≥9.3°) and control group (eROM<9.3°). The radiographic outcomes demonstrated no significant differences in CL, eCL, fCL and ROM between the two groups. Both eROM and fROM were significantly different in the two groups. There was a significant change in CL in the extension group at 3-month follow-up and in the control group at 24-month follow-up. The extension group exhibited significantly lower LCL compared with the control group at follow-up. No significant difference between the two groups was noted in the JOA recovery rate, while the NDI score was significantly different at 24-month follow-up. The positivity ratio of the extension test was significantly greater in the extension group than that in the control group.

CONCLUSIONS

eROM in patients with favorable preoperative cervical extension capacity (eROM≥9.3°) consisted of the actual extension capacity and compensatory flexion. The cervical alignment would be spontaneously restored to its initial lordosis in the short term after laminoplasty. These patients had no substantial LCL at 24-month follow-up and would be good candidates for laminoplasty.

Giant Anomalous Cervical Spinous Process Causing Dynamic Cord Compression: An Unusual Cause for Myelopathy: A Case Report

CASE

A 47-year-old male patient presented with progressively worsening gait instability caused by a giant anomalous, free-floating C5 spinous process resulting in dynamic cord compression and myelopathy. The patient was successfully managed with a C5 laminectomy and total excision of the anomalous spinous process with a good functional outcome at the final follow-up.

CONCLUSION

Anomalies of the posterior arch of the subaxial cervical spine are relatively uncommon and asymptomatic. This case is being reported for its rarity and to highlight the role of dynamic imaging in patients presenting with congenital anomalies of the cervical spine presenting with compressive myelopathy.

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.

High reliability and accuracy of dynamic magnetic resonance imaging in the diagnosis of cervical Spondylotic myelopathy: a multicenter study

BACKGROUND

Cervical spondylotic myelopathy (CSM) is a critical condition that results in significant neurologic deterioration. An accurate diagnosis is essential for determining its outcome and prognosis. The pathology is strongly associated with dynamic factors; therefore, dynamic magnetic resonance (MR) image could be crucial to accurately detect CSM. However, very few studies have evaluated the reliability and accuracy of dynamic MR in CSM. In this study, we aimed to compare intra- and interobserver reliabilities and accuracy of dynamic MR in detecting CSM using sagittal MR scans of the neck in the flexed, neutral, and extended position.

METHODS

Out of 131 patients who underwent surgical treatments for CSM, 107 were enrolled in this study. The patient underwent three-types of sagittal MR scans that were obtained separately in different neck positions (neutral, flexion, and extension postures). The MR scans of the cervical spine were evaluated independently by three spine professionals, on the basis of tabled questionnaires. For accuracy, we performed a receiver operator characteristic analysis, and the overall discriminating ability of each method was measured by calculating the area under the ROC curve. The Cohen's kappa coefficient and the Fleiss-generalized kappa coefficient was used to the inter- and intra-observer reliabilities.

RESULTS

The intraobserver reliability (using the Cohen's kappa coefficient) and interobserver reliability (using the Fless kappa coefficient) were respectively 0.64 and 0.52 for the neutral sagittal MR. The accuracy of neutral sagittal MR in detecting CSM was 0.735 (95% CI, 0.720 to 0.741) while that of extension sagittal MRI was 0.932 (96% CI, 0.921 to 0.948).

CONCLUSIONS

Dynamic MR significantly showed better diagnostic reliability and accuracy in detecting CSM compared to conventional MR. In particular, extension MR scans could provide a more accurate diagnosis than other images.

Patients with degenerative cervical myelopathy exhibit neurophysiological improvement upon extension and flexion: a retrospective cohort study with a minimum 1-year follow-up

Background

Cervical extension and flexion are presumably harmful to patients with degenerative cervical myelopathy (DCM) because they worsen medullary compression visible on dynamic magnetic resonance imaging (MRI). Dynamic somatosensory evoked potentials (SSEPs) are an objective tool to measure the electrophysiological function of the spinal cord at different neck positions. In contrast to previous hypotheses, a considerable proportion of patients with DCM present improved SSEPs upon extension and flexion compared to a neutral position.

Methods

Patients with DCM who underwent preoperative dynamic SSEP examinations and subsequent decompression surgeries between 2015 and 2019 were retrospectively evaluated. We compared extension and flexion SSEPs with neutral SSEPs in each patient and classified them into extension-improved (EI) or extension-nonimproved (EN) and flexion-improved (FI) or flexion-nonimproved (FN) groups. Preoperative clinical evaluations, decompression surgical methods and one-year follow-up clinical data were recorded. Cervical spondylolisthesis and cervical alignment types were evaluated on plain cervical lateral radiographs. The number of stenotic segments, Mühle stenosis grade and disc degeneration stage of the most severe segment, and presence of ligamentum flavum hypertrophy and intramedullary T2 weighted imaging (T2WI) hyperintensity were evaluated on lateral and axial MRI. Data were compared between the EN and EN groups or FI and FN groups with T-tests, chi-square tests or Kruskal-Wallis tests. Prediction criteria were determined with logistic regression analyses.

Results

Forty-nine patients were included, and 9 (18.4%) and 11 (22.4%) showed improved extension and flexion SSEPs compared to their own neutral SSEPs, respectively. Interestingly, EI or FI patients had significantly better one-year postoperative mJOA recoveries than EN or FN patients (T-test, P < 0.001). Moreover, the disease duration (T-test, P = 0.024), involved segment number (Kruskal-Wallis test, P < 0.001), and cervical alignment type (chi-square test, P = 0.005) varied significantly between the EI and EN groups. The FI group presented a significantly higher Mühle stenosis grade than the FN group (Kruskal-Wallis test, P = 0.038). Furthermore, ≤ 2 involved segments and straight or sigmoid cervical alignment were significant criteria predicting improved extension SSEPs (probability: 85.7%), while Mühle stenosis Grade 3 and disease duration ≤6 months were significant criteria predicting improved flexion SSEPs (probability: 85.7%).

Conclusions

Our findings provide evidence for neurophysiological improvement in patients with DCM at extension and flexion and its significance in predicting prognoses. Moreover, certain clinical and radiographic criteria may help predict neurophysiological improvement upon extension or flexion.

Trial registration

“[2020]151”. Retrospectively registered on April 30, 2020.

Finite Element Analysis of Spinal Cord Stress in a Single Segment Cervical Spondylotic Myelopathy

Background

Spinal cord ischemia is largely caused by cervical spondylotic myelopathy (CSM), which has a corresponding biomechanical basis. Finite element analysis of spinal cord stress in diseased segments of CSM was performed to provide a biomechanical basis for the pathogenesis of CSM.

Methods

A single segment (C4-5) in a patient with CSM was selected for mechanical simulation of three-dimensional (3D) computed tomography scanning, and a 3D finite element model of the cervical vertebra was constructed. Based on the patient's age, sex, height, weight, and other parameters, a finite element analysis model of an individual with healthy cervical vertebrae in our hospital was selected as the control to compare the stress changes between the patient and control groups in the analysis of the cervical vertebrae under anterior flexion, posterior extension, lateral flexion, and rotating load in the diseased spinal cord segment.

Results

In the CSM patient, the diseased segment was C4-5. Under loading conditions of forward flexion, posterior extension, left flexion, right flexion, left rotation, and right rotation, the maximum stress on the spinal cord in the control group was 0.0044, 0.0031, 0.00017, 0.00014, 0.0011, and 0.001 MPa, respectively, whereas those in the spinal cord in the CSM group were 0.039, 0.024, 0.02, 0.02, 0.0194, and 0.0196 MPa, respectively.

Conclusion

The maximum stress on the diseased segments of the spinal cord in the CSM group was higher than that in the control group, which contributed to verifying the imaging parameters associated with spinal cord compression stress.

Degenerative Cervical Myelopathy: Development and Natural History [AO Spine RECODE-DCM Research Priority Number 2]

STUDY DESIGN

Narrative review.

OBJECTIVES

To discuss the current understanding of the natural history of degenerative cervical myelopathy (DCM).

METHODS

Literature review summarizing current evidence pertaining to the natural history and risk factors of DCM.

RESULTS

DCM is a common condition in which progressive arthritic disease of the cervical spine leads to spinal cord compression resulting in a constellation of neurological symptoms, in particular upper extremity dysfunction and gait impairment. Anatomical factors including cord-canal mismatch, congenitally fused vertebrae and genetic factors may increase individuals' risk for DCM development. Non-myelopathic spinal cord compression (NMSCC) is a common phenomenon with a prevalence of 24.2% in the healthy population, and 35.3% among individuals >60 years of age. Clinical radiculopathy and/or electrophysiological signs of cervical cord dysfunction appear to be risk factors for myelopathy development. Radiological progression of incidental Ossification of the Posterior Longitudinal Ligament (OPLL) is estimated at 18.3% over 81-months and development of myelopathy ranges between 0-61.5% (follow-up ranging from 40 to 124 months between studies) among studies. In patients with symptomatic DCM undergoing non-operative treatment, 20-62% will experience neurological deterioration within 3-6 years.

CONCLUSION

Current estimates surrounding the natural history of DCM, particularly those individuals with mild or minimal impairment, lack precision. Clear predictors of clinical deterioration for those treated with non-operative care are yet to be identified. Future studies are needed on this topic to help improve treatment counseling and clinical prognostication.

Optimizing the Application of Surgery for Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 10]

STUDY DESIGN

Literature Review (Narrative).

OBJECTIVE

To introduce the number 10 research priority for Degenerative Cervical Myelopathy: Individualizing Surgery.

METHODS

This article summarizes the current recommendations and indications for surgery, including how known prognostic factors such as injury time, age, disease severity, and associated comorbidities impact surgical outcome. It also considers key areas of uncertainty that should be the focus of future research.

RESULTS

While a small proportion of conservatively managed patients may remain stable, the majority will deteriorate over time. To date, surgical decompression is the mainstay of treatment, able to halt disease progression and improve neurologic function and quality of life for most patients. Whilst this recognition has led to recommendations on when to offer surgery, there remain many uncertainties including the type of surgery, or timing in milder and/or asymptomatic cases. Their clarification has the potential to transform outcomes, by ensuring surgery offers each individual its maximum benefit.

CONCLUSION

Developing the evidence to better guide surgical decision-making at the individual patient level is a research priority for Degenerative Cervical Myelopathy.

Risk factors for the development of degenerative cervical myelopathy: a review of the literature

Degenerative cervical myelopathy (DCM) encompasses various pathological conditions causing spinal cord (SC) impairment, including spondylosis (multiple level degeneration), degenerative disc disease (DDD), ossification of the posterior longitudinal ligament (OPLL), and ossification of the ligamentum flavum (OLF). It is considered the most common cause of SC dysfunction among the adult population. The degenerative phenomena of DDD, spondylosis, OPLL and OLF, is likely due to both inter-related and distinct factors. Age, cervical alignment, and range of motion, as well as congenital factors such as cervical cord-canal mismatch due to congenital stenosis, Klippel-Feil, Ehler-Danlos, and Down syndromes have been previously reported as potential factors of risk for DCM. The correlation between some comorbidities, such as rheumatoid arthritis and movement disorders (Parkinson disease and cervical dystonia) and DCM, has also been reported; however, the literature remains scare. Other patient-specific factors including smoking, participation in contact sports, regular heavy load carrying on the head, and occupation (e.g. astronauts) have also been suggested as potential risk of myelopathy development. Most of the identified DCM risk factors remain poorly studied however. Further researches will be necessary to strengthen the current knowledge on the subject, especially concerning physical labors in order to identify patients at risk and to develop an effective treatment strategy for preventing this increasing prevalent disorder.

Asymptomatic Spinal Cord Compression: Is Surgery Necessary to Return to Play

Advising athletes with asymptomatic cervical canal stenosis on their return to active play is a topic of considerable debate, with no definitive guidelines in place. Once cervical canal stenosis is identified, often through imaging following other injuries, it is difficult to predict the risk of future injury upon return to play in both contact and collision sports. Consequently, the decision can be a complicated one for the athlete, family, and physician alike. In this article, we identify radiographical and magnetic resonance imaging (MRI)-based criteria that may distinguish athletes "at-risk" for more severe consequences due to asymptomatic cervical canal stenosis from those who are safe to return to play. Using a Torg-Pavlov ratio <0.7 and MRI metrics, namely a minimal disc-level canal diameter <8 mm, a cord-to-canal area ratio >0.8, or space available for the cord <1.2 mm, can help when making these difficult decisions. Counseling can be a critical asset to patients with cervical stenosis who have had a previous episode of cervical cord neuropraxia, especially when they are involved in high-risk sports such as American football and rugby. We believe that while this remains an area of continued concern and controversy, improved MRI criteria will be a useful springboard for further studies, especially in the elite athlete population.

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.

Cervical arteriosclerosis is associated with preoperative clinical symptoms in patients with cervical spondylotic myelopathy

PURPOSE

This study aims to clarify the association between cervical spondylotic myelopathy (CSM) and cervical arteriosclerosis using ultrasonography that comprehensively includes spinal cord stenosis.

METHODS

Eighty-two consecutive patients aged over 60 years who underwent spine surgery were divided into those with CSM (n = 31; CSM group) and those with lumbar spinal stenosis without cervical myelopathy (n = 51; LSS group). Maximum spinal cord compression (MSCC) was evaluated for cervical stenosis severity using magnetic resonance (MR) images. The intima-media thickness (IMT) of the common carotid artery (CCA) and pulsatility index (PI) of the bilateral internal carotid artery (ICA) and vertebral artery (VA) were evaluated for cervical arteriosclerosis using pulsed-wave Doppler ultrasonography. Symptom severity was evaluated using the Japanese Orthopaedic Association (JOA) score. Spearman's correlation coefficient was used to determine the relationship between the JOA score and MSCC or IMT and PI in each group. Stepwise multiple linear regression analyses were conducted with the JOA score as a dependent variable and age, sex, body mass index, cervical arteriosclerosis assessment, and MSCC as independent variables.

RESULTS

Bilateral IMT and left-side ICA-PI were significantly negatively correlated with JOA scores in the CSM group (Right-CCA-IMT: R =  - 0.412, Left-IMT: R =  - 0.549, Left-ICA -PI: R =  - 0.205, P < 0.05), but not in the LSS group. Multiple linear regression analyses showed that CCA-IMT was the strongest independent factor associated with the preoperative JOA score.

CONCLUSIONS

Cervical arteriosclerosis was associated with preoperative clinical symptoms in CSM patients.

Clinical and Radiologic Features of Degenerative Cervical Myelopathy Depending on the Presence of Cord Signal Change

BACKGROUND

Cord signal change (CSC) on magnetic resonance (MR) imaging is an important radiologic feature of degenerative cervical myelopathy (DCM). Occasionally, DCMs correlate with clinical symptoms with no CSC. The aim of this study was to evaluate clinical and radiologic features, depending on the presence of CSC in DCM.

METHODS

This retrospective study included 73 patients who underwent cervical laminoplasty for DCM. They were divided into 2 groups based on the presence of CSC on static MR imaging (positive CSC in group A and negative CSC in group B). Preoperative radiologic parameters on lateral radiographs and the severity of canal stenosis on MR imaging were analyzed. The functional outcomes were evaluated using the modified Japanese Orthopedic Association score and Nurick grade.

RESULTS

Group A showed more deteriorated canal stenosis (P < 0.001) and kyphotic change than did group B. C2-7 sagittal vertical axis (P = 0.003) of group A and C2-7 range of motion (C27ROM; P < 0.001) of group B were greater than in the opposite groups, respectively. In a multivariate analysis, greater width of the cervical canal (P = 0.002) and increased C27ROM (P = 0.002) were statistically significant radiologic parameters related to negative CSC. Group B showed better functional outcomes until 6 months postoperatively, with statistical significance.

CONCLUSIONS

DCM with negative CSC can be caused by a well-preserved cervical ROM, even with less deteriorated canal stenosis and kyphosis. C27ROM may be a helpful radiologic parameter in diagnosing DCM before CSC appears.

Clinical Impact of Cervical Imbalance on Surgical Outcomes of Laminoplasty: A Propensity Score-Matching Analysis

STUDY DESIGN

This is a retrospective cohort study.

OBJECTIVE

The objective of this study was to identify the impact of preoperative cervical sagittal balance on the 2-year surgical outcomes of laminoplasty.

SUMMARY OF BACKGROUND DATA

The cervical imbalance is considered associated with poor health-related quality of life and poor outcomes for cervical deformity surgery. However, the influences of cervical imbalance on the clinical outcomes of laminoplasty for cervical spondylotic myelopathy (CSM) patients are unclear.

MATERIALS AND METHODS

A total of 277 consecutive CSM patients who underwent laminoplasty were analyzed. From the last consecutive 136 patients, matched control group [cervical sagittal vertical axis (cSVA)<40 mm, n=30] and matched imbalance group (≥40 mm, n=30) were selected based on their propensity score adjusted for age, sex, cervical alignment, and preoperative Japanese Orthopaedic Association (JOA) score. Change in clinical outcomes and radiographic parameters at 2 years postoperatively were compared between the 2 matched groups using mixed-effects model. For the validation of the primary results, factors that correlated with the recovery rate of JOA score of another 141 patients were analyzed using multiple linear regression analysis.

RESULTS

There was no significant interaction between the 2 matched groups in all clinical outcomes, including the severity of myelopathy, patient-oriented health-related quality of life score, physical and mental status, physical functions, and pain score. Regarding the radiographic evaluation, change in cSVA showed significant differences (P=0.038); cSVA was kept stable in the matched control group, whereas its value significantly decreased in the matched imbalance group. Multiple linear regression models demonstrated that preoperative cSVA is not significantly related to the recovery rate of JOA score at 2 years postoperatively (P=0.114).

CONCLUSIONS

Preoperative cervical imbalance did not significantly affect the 2-year surgical outcomes of laminoplasty. Furthermore, cervical imbalance improved after surgery. These results can suggest physicians consider laminoplasty as a treatment for CSM patients regardless of their cervical balance.

LEVEL OF EVIDENCE

Level III-treatment benefits: nonrandomized controlled cohort/follow-up study.

Dynamic Cord Compression Causing Cervical Myelopathy

Due to the highly mobile nature of the cervical spine, and the fact that most magnetic resonance imagings (MRIs) and computed tomography scans are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis. We performed a literature review on dynamic cord compression in the context of cervical spondylotic myelopathy (CSM), with particular emphasis on the role of dMRI. Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Dynamic MRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI is more sensitive in detecting stenosis in patients with CSM than in those with ossification of the posterior longitudinal ligament (OPLL), likely because OPLL patients often have a more limited range of motion than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM.

Spinal sagittal alignment and trapezoidal deformity in patients with degenerative cervical spondylolisthesis

Degenerative cervical spondylolisthesis (DCS) is a cervical deformity arising from regressive changes where trapezoidal deformity characterized by hypertrophic osteophytes of spinal elements is often observed. There is a paucity of literature about the spinal contour of DCS and trapezoidal vertebrae. We conducted this research to clarify the relationship between spinal sagittal alignment and trapezoidal deformity in DCS. Total seventy-nine patients with cervical spondylosis were enrolled. Twenty-four patients who exhibited cervical spondylolisthesis were classified into DCS group. Other patients were classified into a control group. Measurements of radiographic parameters and trapezoidal deformity were made. DCS was found mostly in C3-C4 and C4-C5 (16 and 10 cases, respectively). T1S and T1-T4 TK was larger in the DCS group than in the control (T1S: 29.9 ± 2.3° vs. 23.7 ± 1.5°, T1-T4 TK: 14.9 ± 2.1° vs. 9.0 ± 1.4°). C2-C7A was smaller in DCS (3.5 ± 3.6° vs. 11.9 ± 2.3°). Trapezoidal deformity was apparent in the vertebra below the slipped segment. Among sagittal parameters, T1S and T1-T4 TK were positively correlated with DCS (r = 0.523 and r = 0.438, respectively). For these correlations with DCS, both logistic and linear regression models predicted threshold values of approximately 30° for T1S and 15° for T1-T4 TK responsible for DCS. DCS was mostly found in the middle cervical region. Among sagittal parameters, enlarged T1S and T1-T4 TK, which were strongly correlated with amount of slippage, was considered affected to DCS. Cervical kyphosis and trapezoidal deformity also exhibited strong correlations with DCS, and were considered responsible for clinical instability.

Kinematic characteristics of patients with cervical imbalance: a weight-bearing dynamic MRI study

STUDY DESIGN

It is a retrospective analysis of 1806 consecutive cervical magnetic resonance images taken in weight-bearing flexion, neutral, and extension positions.

OBJECTIVE

The aim was to identify the kinematic characteristics of patients with cervical imbalance. Additionally, factors were analysed in the neutral position that could predict the characteristics. Little is known about the kinematic characteristics during cervical flexion and extension positions of the patient with cervical imbalance (cervical sagittal vertical axis (cSVA) in neutral position ≥ 40 mm).

METHODS

After evaluating the whole images, cervical imbalance group (cSVA ≥ 40 mm, n = 43) and matched control group (< 40 mm, n = 43) were created using propensity score adjusting for age, gender, and cervical alignment. They were compared for cervical motion, changes in disc bulge, and ligamentum flavum (LF) bulge from flexion to extension. Multinomial logistic regression analysis and receiver operating characteristic curve analysis were calculated to verify the predictive factors and cut-off value of the identified characteristics.

RESULTS

There were no significant differences in range of motion and the change in bulged discs. There was significant difference in the presence of LF bulge from flexion to extension (p = 0.023); the incidence of LF bulge increased sharply from neutral to extension in imbalance group, while there was linear increase in control group. The canal diameter (odds ratio = 0.61, p = 0.002) and disc height (odds ratio = 1.60, p = 0.041) showed significant relationship with the segments with LF bulge observed in extension but not in neutral position in the imbalance group; the cut-off values were 10.7 mm for canal diameter (sensitivity 82.5%, specificity 66.7%) and 7.1 mm for disc height (70.8%, 58.5%).

CONCLUSION

Patients with cervical imbalance had a stark increase in LF bulge from the neutral to extension position. Canal diameter < 10.7 mm and disc height > 7.1 mm on neutral images may predict the segments with LF bulge observed in extension, but not in the neutral position.

LEVEL OF EVIDENCE

II (Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding). These slides can be retrieved from Electronic Supplementary Material.

Dynamic changes in the reflex exam of patients with sub-axial cervical stenosis

Though dynamic changes in the physical exam of patients being evaluated for cervical spine pathology have been reported, there is limited information on the prevalence and clinical features associated with reflex changes in a population undergoing surgical evaluation for cervical spine pathology. Fifty-one patients with at least grade 1 cervical stenosis on MRI underwent initial surgical evaluation for cervical spine pathology. All patients received complete neurologic examinations including dynamic reflex testing in three positions (neck neutral, extended, and flexed) by 2 spine surgeons. The average age was 58.7 years (range, 34-80), with 28 (55%) patients being male. Stenosis at the symptomatic levels was grade 1 in 18 patients (35%), grade 2 in 11 (21%), and grade 3 in 22 (43%). Twenty-one patients (41%) had a dynamic change in reflex exam. The most common change in reflex exam was seen in the Hoffman's reflex with 14 patients (28%). Patients with grade 3 stenosis were more likely to have a static Hoffman's reflex (64%) compared with grade 1 (17%) and grade 2 (18%) (p < 0.05). Patients with grade 3 stenosis had a higher rate of either a static or dynamic Hoffman's reflex (82%) compared with grade 1 (44%) (p < 0.05), but there was no difference between grade 3 and grade 2 (64%) (Table 2). Dynamic changes in reflex exam are commonly seen in patients being evaluated for symptomatic cervical stenosis. The routine neurologic exam can be supplemented with dynamic reflex testing, especially in cases where clinical history or imaging is concerning for cervical myelopathy.

A Dynamic Magnetic Resonance Imaging Study of Changes in Severity of Cervical Spinal Stenosis in Flexion and Extension

Objective

To evaluate changes in the severity of cervical spinal stenosis (CSS) in flexion and extension and determine whether the rate of change with motion varied with severity.

Methods

The study included 92 symptomatic patients with a mean age of 57.80±10.41, who underwent cervical spine dynamic magnetic resonance imaging. The severity of stenosis was evaluated using a semi-quantitative CSS score, ranging from 0 (no spinal stenosis) to 18 (severe stenosis). Radiological evaluation included flexion, neutral, and extension measurements, as determined by the C2–C7 Cobb angle. The severity of stenosis was represented by the total CSS score. The total CSS score in flexion, neutral, and extension positions was compared using repeated measures one-way analysis of variance. The change rate of stenosis per angle motion (CRSPAM) was defined as change in total CSS score divided by change in Cobb angle. The correlation of CRSPAM with severity of stenosis, represented by total CSS score in neutral position, was evaluated using Pearson correlation analysis.

Results

The total CSS score was significantly higher in extension (6.04±2.68) than in neutral position (5.25±2.47) (p<0.001), and significantly higher in neutral than in flexion position (4.40±2.45) (p<0.001). The CRSPAM was significantly and positively correlated with total CSS score in neutral position in the flexion-extension range (r=0.22, p=0.04) and flexion-neutral range (r=0.27, p=0.01).

Conclusion

In symptomatic CSS patients, the radiological severity of stenosis increases with extension and decreases with flexion. In patients with CSS, the rate of variation in spinal stenosis increases with increased severity.

Kinematic analysis of the space available for cord and disc bulging of the thoracic spine using kinematic magnetic resonance imaging (kMRI)

BACKGROUND CONTEXT

The thoracic spine was previously known as a relatively stable region in human spine. Several studies reported that the motion of the thoracic spine and changes in the cross-sectional area of the spinal cord changed with positions in the sagittal plane. The kinematic relationship between the thoracic disc and the space available for cord (SAC) with the positional change is still not well investigated.

PURPOSE

The objective of this study was to evaluate the kinematic change of the intervertebral disc and space available for the spinal cord of the thoracic spine using kinematic magnetic resonance imaging (kMRI).

STUDY DESIGN

This is a retrospective study.

PATIENT SAMPLE

The patient sample included 105 patients who underwent thoracic spine kMRI.

OUTCOME MEASUREMENT

Disc bulging and the SAC were evaluated from T4-T5 to T11-T12 in flexion, neutral, and extension positions.

METHODS

MRAnalyzer3 (TrueMRI Corporation, Bellflower, CA, USA) was used to analyze disc bulging and SAC from T4-T5 to T11-T12. The Friedman test was used to analyze the differences in disc bulging and SAC between neutral, flexion, and extension positions at each segment. The Wilcoxon signed-rank test was used for post hoc analysis for the significant levels from the Friedman test.

RESULTS

The mean value of the thoracic intervertebral disc area from T4-T5 to T11-T12 tended to be larger in flexion than in extension. Initial analysis with the Friedman test revealed a significant difference in disc bulging at T8-T9, T9-T10, and T11-T12 among the three positions (p<.05). Post hoc analysis showed that disc bulging was only significant at T8-T9 between flexion and extension (p<.001), at T9-T10 between neutral and flexion (0.003), and at T9-T10 between flexion and extension (p=.004). The SAC from T4-T5 to T11-T12 tended to be widest in extension and narrowest in flexion. Only T5-T6 exhibited a statistically significant difference in SAC between flexion and extension (p=.002).

CONCLUSIONS

The thoracic discs and the SAC from T4-T5 to T11-T12 showed kinematic changes from flexion to extension. The thoracic spinal canal tended to be narrowest in flexion and widest in the extension. Thus, kyphotic deformities could be one of the etiologies for neurogenic deterioration in patients with thoracic myelopathy.

Modic changes in the cervical endplate of patients suffering from cervical spondylotic myelopathy

Background

The distribution and related factors of Modic changes (MC) in the lumbar spine has been evaluated. In the present study, the MC in the cervical endplate of patients with cervical spondylotic myelopathy (CSM) was investigated.

Methods

A total of 6422 cervical endplates of 539 patients suffered from CSM (259 males and 280 females) with mean age of 46 ± 5.2 years. All patients underwent MRI scans and X-ray for evaluating the distribution of MC. The clinical information were recorded.

Results

It was observed that 13.0% of patients and 2.4% of endplates showed MC. There were 3.7, 7.6, and 1.7% of cases diagnosed as types I, II, and III, respectively, suggesting MC were corrected with disc degeneration. The incidence rates of MC were 0, 0.3, 0.6, 0.9, 0.7, and 0.2%, respectively, in different intervertebral disc segments C_2–3, C_3–4, C_4–5, C_5–6, C_6–7, and C₇T₁. Disc degeneration, segment, disease course, and age were statistically related to the MC. Patients over the age of 40 more easily suffered from MC.

Conclusions

MCs manifested as type II mainly in patients with CSM. The incidence was highest in the C_5–6 segment. Disc degeneration greatly contributed to the occurrence of MC.

The Role of Dynamic Magnetic Resonance Imaging in Cervical Spondylotic Myelopathy

Dynamic spinal cord compression has been investigated for several years, but until the advent of open MRI, the use of dynamic MRI (dMRI) did not gain popularity. Several publications have shown that cervical cord compression is both static and dynamic. On many occasions the evaluation of cervical spondylotic myelopathy (CSM) is straightforward, but patients are frequently encountered with a significantly worse clinical examination than would be suggested by radiological images. In this paper, we present an extensive review of the literature in order to describe the importance of dMRI in various settings and applications. A detailed literature review was performed in the Medline and Pubmed databases using the terms “cervical spondylotic myelopathy”, “dynamic MRI”, “kinetic MRI”, and “myelomalalcia” for the period of 1980-2016. The study was limited to English language, human subjects, case series, retrospective studies, prospective reports, and clinical trials. Reviews, case reports, cadaveric studies, editorials, and commentaries were excluded. The literature search yielded 180 papers, 19 of which met inclusion criteria. However, each paper had evaluated results and outcomes in different ways. It was not possible to compile them for meta-analysis or pooled data evaluation. Instead, we evaluated individual studies and present them for discussion. We describe a number of parameters evaluated in 2661 total patients, including dynamic changes to spinal cord and canal dimensions, transient compression of the cord with changes in position, and the effects of position on the intervertebral disc. dMRI is a useful tool for understanding the development of CSM. It has found several applications in the diagnosis and preoperative evaluation of many patients, as well as certain congenital dysplasias and Hirayama disease. It is useful in correlating symptoms with the dynamic changes only noted on dMRI, and has reduced the incidence of misdiagnosis of myelopathy.

Increased Segmental Range of Motion Is Correlated With Spondylolisthesis in the Cervical Spine After Laminoplasty

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to determine the incidence of increased segmental range of motion (ROM) after laminoplasty and to clarify whether increased ROM is associated with spondylolisthesis. Finally, we explored the effect of increased segmental ROM on clinical results.

SUMMARY OF BACKGROUND DATA

Cervical laminoplasty for cervical spondylotic myelopathy causes reduced ROM, possibly due to the unintended contracture of the facet joint or a bony union. Although it is rarely studied, ROM may also increase following laminoplasty. Thus far, there are no reports describing the correlation between increased segmental ROM and segmental spondylolisthesis after laminoplasty.

METHODS

We evaluated 187 segments from 39 cervical spondylotic myelopathy patients who underwent bilateral open door laminoplasty from C2 to C7. The segmental ROM and spondylolisthesis were measured using dynamic radiographs that were obtained preoperatively and 2 years postoperatively. The Japanese Orthopedic Association (JOA) score was used for clinical evaluation. To compare the clinical results, we compared the cases with increased ROM in at least one segment with the remaining cases.

RESULTS

Increased segmental ROM (i.e., ≥5° increase) was observed in 25 of 187 segments (13.4%) from 14 cases. There was a strong correlation between increased ROM and spondylolisthesis. A high preoperative disc height was associated with increased segmental ROM 2 years postoperation. Regardless of the correlation with spondylolisthesis, there was no statistically significant correlation between increased segmental ROM and JOA score.

CONCLUSION

The decrease in segmental ROM after laminoplasty was not uniform. Approximately 13.4% of all segments showed increased ROM. The preoperative disc height might influence the risk for increased segmental ROM. Furthermore, increased ROM was correlated with spondylolisthesis in the segment, though it was not correlated with clinical results.

LEVEL OF EVIDENCE

4.

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.

Kinematic Magnetic Resonance Imaging for Evaluation of Disc-Associated Cervical Spondylomyelopathy in Doberman Pinschers

BACKGROUND

The dynamic component of disc-associated cervical spondylomyelopathy (DA-CSM) currently is evaluated using traction magnetic resonance imaging (MRI), which does not assess changes in flexion and extension of the cervical vertebral column. In humans with cervical spondylotic myelopathy, kinematic MRI is used to identify dynamic compressions.

HYPOTHESIS/OBJECTIVES

To evaluate the feasibility and utility of kMRI in Doberman Pinschers with DA-CSM using a novel positioning device. We hypothesized that kMRI would identify compressive lesions not observed with neutral positioning and change the dimensions of the spinal cord and cervical vertebral canal.

ANIMALS

Nine client-owned Doberman Pinschers with DA-CSM.

METHODS

Prospective study. After standard MR imaging of the cervical spine confirmed DA-CSM, dogs were placed on a positioning device to allow imaging in flexion and extension. Morphologic and morphometric assessments were compared between neutral, flexion, and extension images.

RESULTS

Flexion was associated with improvement or resolution of spinal cord compression in 4/9 patients, whereas extension caused worsening of compressions in 6/9 patients. Extension identified 6 new compressive lesions and was significantly associated with dorsal and ventral compression at C5-C6 (P = .021) and C6-C7 (P = .031). A significant decrease in spinal cord height occurred at C6-C7 from neutral to extension (P = .003) and in vertebral canal height at C5-C6 and C6-C7 from neutral to extension (P = .011 and .017, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results suggest that kMRI is feasible and provides additional information beyond what is observed with neutral imaging, primarily when using extension views, in dogs with DA-CSM.

Kinematic relationship between missed ligamentum flavum bulge and degenerative factors in the cervical spine

BACKGROUND CONTEXT

Bulging of ligamentum flavum can happen with the aging process and can lead to compression of the spinal cord and nerves. However, the distribution and the risk factors associated with a missed ligamentum flavum bulge (LFB) are unknown.

PURPOSE

The aim was to evaluate the distribution and risk factors associated with missed LFB in the cervical spine.

STUDY DESIGN

This was a retrospective analysis of kinematic magnetic resonance images (kMRI).

PATIENT SAMPLE

Patients diagnosed with symptomatic neck pain or radiculopathy between March 2011 and October 2012 were included.

OUTCOME MEASURES

The outcome measures were missed LFB and degenerative factors.

METHODS

A total of 200 patients (1,000 cervical segments) underwent upright kMRI in neutral, flexion, and extension postures. The LFB, sagittal cervical angles, disc herniation, disc degeneration, disc height, angular motion, translational motion, age, and gender were recorded. After excluding segments with LFB in neutral and flexion position, Pearson and Spearman correlation coefficients were used to evaluate the relation between the risk factors and missed LFB in the extension position.

RESULTS

The average depth of LFB was 0.24±0.71 mm at C2-C3, 1.02±1.42 mm at C3-C4, 1.65±1.48 mm at C4-C5, 2.13±1.37 mm at C5-C6, and 1.05±1.54 mm at C6-C7. The distribution of LFB was the most frequent at C5-C6 level (76.58%) followed by C4-C5 (63.06%). Disc herniation, disc degeneration, angular variation, and translational motion were significantly correlated with missed LFB at C4-C5 andC5-C6. Disc degeneration was the only factor significantly correlated with missed LFB at all cervical segments.

CONCLUSIONS

Occurrence and depth of missed LFB was the highest at C4-C5 and C5-C6 compared with other cervical levels. Disc degeneration, disc herniation, angular variation, and translational motion could play a role in the development of LFB at C4-C5 andC5-C6.

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.