Axial load—dependent cervical spinal alterations during simulated upright posture: a comparison of healthy controls and patients with cervical degenerative disease

Evaluation and management of orthostatic headache in hypermobility disorders

Headache is a frequent symptom among patients with hypermobility spectrum disorders. This mini review focuses specifically on a challenging aspect of headache evaluation in all patients, but especially those with hypermobility - the orthostatic headache. While the differential for an orthostatic headache is overall limited, patients with hypermobility disorders have risk factors for all of the most commonly encountered orthostatic headache disorders. The most common conditions to produce orthostatic headaches are discussed - spontaneous intracranial hypotension, cervicogenic headache, and postural orthostatic tachycardia syndrome. Less common etiologies of orthostatic headache pertinent to any patient are presented in table format.

Cervical Foraminal Changes in Patients with Intermittent Arm Radiculopathy Studied with a New MRI-Compatible Compression Device

Diagnosing cervical foraminal stenosis with intermittent arm radiculopathy is challenging due to discrepancies between MRI findings and symptoms. This can be attributed to the fact that MRI images are often obtained in a relaxed supine position. This study aims to evaluate the feasibility of the Dynamic MRI Compression System (DMRICS) and to assess possible changes in cervical foramina, with both quantitative measurements and qualitative grading systems, with MRI during a simulated Spurling test. Ten patients (five women and five men, ages 29-45) with previously confirmed cervical foraminal stenosis underwent MRI scans using DMRICS. MRI images were acquired in both relaxed and provoked states. A radiologist assessed 30 foramina (C4-C7) on the symptomatic side in both patient positions. Quantitative and qualitative measures were performed, including the numeric rating scale (NRS) and the Park and Kim grading systems. The provoked state induced concordant neck and arm pain in 9 of 10 patients. Significant shifts in Park and Kim foraminal gradings were noted: 13 of 27 Park gradings and 9 of 27 Kim gradings escalated post provocation. No quantitative changes were observed. This pilot study indicates that the DMRICS device has the potential to improve diagnostic accuracy for cervical radiculopathy, demonstrating induced cervical foraminal changes during a simulated Spurling test while performing MRI.

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

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

Simulating upright cervical lordosis in the supine position

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

Cord compression defined by MRI is the driving factor behind the decision to operate in Degenerative Cervical Myelopathy despite poor correlation with disease severity

OBJECTIVES

The mainstay treatment for Degenerative Cervical Myelopathy (DCM) is surgical decompression. Not all cases, however, are suitable for surgery. Recent international guidelines advise surgery for moderate to severe disease as well as progressive mild disease. The goal of this study was to examine the factors in current practice that drive the decision to operate in DCM.

STUDY DESIGN

Retrospective cohort study.

METHODS

1 year of cervical spine MRI scans (N = 1123) were reviewed to identify patients with DCM with sufficient clinical documentation (N = 39). Variables at surgical assessment were recorded: age, sex, clinical signs and symptoms of DCM, disease severity, and quantitative MRI measures of cord compression. Bivariate correlations were used to compare each variable with the decision to offer the patient an operation. Subsequent multivariable analysis incorporated all significant bivariate correlations.

RESULTS

Of the 39 patients identified, 25 (64%) were offered an operation. The decision to operate was significantly associated with narrower non-pathological canal and cord diameters as well as cord compression ratio, explaining 50% of the variance. In a multivariable model, only cord compression ratio was significant (p = 0.017). Examination findings, symptoms, functional disability, disease severity, disease progression, and demographic factors were all non-significant.

CONCLUSIONS

Cord compression emerged as the main factor in surgical decision-making prior to the publication of recent guidelines. Newly identified predictors of post-operative outcome were not significantly associated with decision to operate.

Dynamic Cervical Radiographs in Patients with Hirayama Disease: An Unneglectable Factor on the Choice of Surgery Options

OBJECTIVE

To evaluate the cervical spine alignment and range of motion (ROM) of neck flexion in patients with Hirayama disease.

METHODS

Fifty male patients were included, with dynamic radiographs and magnetic resonance imaging (MRI) analyzed retrospectively. The Cobb angles for the entire cervical spine (C2-C7) and each level (C2/3-C6/7) were measured, and the neck flexion ROM was defined as the neutral Cobb angle minus the flexion Cobb angle. Paired t tests and Wilcoxon signed-rank tests were used to compare the Cobb angles and ROM between radiographs and MRI.

RESULTS

The neutral and flexion Cobb angles decreased from C2/3 to C5/6 but increased at C6/7 on radiographs and MRI. The neutral Cobb angle of C2-C7 from radiographs was significantly larger than that seen on MRI (5.27° vs. -3.26°; P < 0.0001). Neck flexion ROM seen with MRI tended to be lower than those of corresponding levels on radiographs. The ROM of C2-C7, C3/4, and C6/7 on radiographs was significantly larger than that seen with MRI (37.86° vs. 26.59°, P < 0.0001; 7.46° vs. 5.10°, P = 0.0071; and 10.45° vs. 7.03°, P = 0.0023, respectively). For the lower cervical levels, the largest and second largest ROM were seen in C5/6 and C6/7 on the radiographs but C5/6 and C4/5 on MRI.

CONCLUSIONS

The cervical spine alignment and neck flexion ROM in Hirayama disease differed between radiographs and MRI. Both imaging techniques should be examined comprehensively when planning an operation.

The Assessment of Upright Cervical Spinal Alignment Using Supine MRI Studies

STUDY DESIGN

This is a prospective, single-centre study.

OBJECTIVE

The purpose of this study is researching whether there is a correlation or not between the cervical alignment in the examinations of magnetic resonance imaging (MRI) in lying position and the alignment in the cervical direct radiography and whether the cervical alignment in standing position could be estimated or not through MRI measurements in the supine position.

SUMMARY OF BACKGROUND DATA

Cervical spinal alignment is a parameter required for deciding the surgical procedure particularly in patients with cervical myelopathy and deformity. However, cervical alignment angles change according to lying and standing positions. Therefore, the direct standing radiograph is taken as basis for this examination.

METHODS

Cervical alignments were measured with 3 different methods with the standing lateral radiographies and lying MRI of 51 patients with cervical disorder.

RESULTS

A high correlation was found between the measurements in standing and lying positions for the spinal alignments measured through the Cobb angle and posterior tangent method. It was found that standing Cobb angle (in plain graphy)=Cobb angle (in MRI)×0.489+7.13 and posterior tangent angle (in plain graphy)=posterior tangent angle (in MRI)×0.54+9.37.

CONCLUSIONS

It is possible to estimate the spinal alignment in standing position with the measurements of cervical spinal alignment in the MRI at supine position. And this may render having cervical graphy in standing position unnecessary.

Adolescent Disc Degeneration - No Headache Association

The objective of the study was to determine whether adolescents with headache have more disc degeneration in the cervical spine than headache-free controls. This study is part of a population-based follow-up study of adolescents with and without headache. At the age of 17 years, adolescents with headache at least three times a month ( N = 47) and adolescents with no headache ( N = 22) participated in a magnetic resonance imaging (MRI) study of the cervical spine. Of the 47 headache sufferers, 17 also had weekly neck pain and 30 had neck pain less than once a month. MRI scans were interpreted independently by three neuroradiologists. Disc degeneration was found in 67% of participants, with no difference between adolescents with and without headache. Most of the degenerative changes were located in the lower cervical spine. In adolescence, mild degenerative changes of the cervical spine are surprisingly common but do not contribute to headache.

Kinematic analysis of the cervical cord and cervical canal by dynamic neck motion

STUDY DESIGN

Normal cervical sagittal length patterns were measured by magnetic resonance imaging (MRI).

PURPOSE

The aim of this study was to evaluate the relationship of sagittal length patterns between the cervical cord and the cervical canal in flexion-extension kinematics.

OVERVIEW OF LITERATURE

Cervical dynamic factors sometimes cause a cervical spondylotic myelopathy in elderly subjects and an overstretching myelopathy in juvenile subjects. Previous studies showed the length changing of the cervical cord in flexion and extension. However, there is no detailed literature about the relationship between cervical vertebral motion and cord distortion yet.

METHODS

Sixty-two normal subjects (28 male and 34 female, 42.1±8.5 years old) without neck motion disturbances and abnormalities on cervical X-ray and MRI were enrolled in this study.

RESULTS

The cervical cord length was significantly longer in flexion and significantly shorter in extension in all cervical cord sagittal lines. The cervical canal length pattern was also the same as the cervical cord. The elongation of the cervical cord and canal was the largest at the site of the posterior cervical canal and the shortest at the anterior canal site. The positions of the cerebellar tonsils were verified at each neck position.

CONCLUSIONS

The posterior elements of the cervical canal were most affected by neck motion. Movement directions of the upper cervical cord were verified among the various neck positions.

Adolescent cervical disc degeneration in MRI does not predict adult headache or neck pain: A 5-year follow-up of adolescents with and without headache

AIM

The impact of early degenerative changes of the cervical spine on pain in adulthood is unknown. The objective was to determine whether degeneration in adolescence predicts headache or neck pain in young adulthood.

METHODS

As part of a follow-up of schoolchildren with and without headache, 17-year-old adolescents with headache at least three times a month (N = 47) and adolescents with no headache (N = 22) participated in a magnetic resonance imaging (MRI) study of the cervical spine. The same adolescents were re-examined by phone interview at the age of 22 years (N = 60/69, 87%).

RESULTS

Mild disc degeneration at the age of 17 years was common, but was not associated with either frequent or intensive headache or neck pain at the age of 22 years. Conclusion: Mild degenerative changes of the cervical spine in 17-year-old adolescents cannot be regarded as a cause of future headache or neck pain.

Three-dimensional kinematic stress magnetic resonance image analysis shows promise for detecting altered anatomical relationships of tissues in the cervical spine associated with painful radiculopathy

For some patients with radiculopathy a source of nerve root compression cannot be identified despite positive electromyography (EMG) evidence. This discrepancy hampers the effective clinical management for these individuals. Although it has been well-established that tissues in the cervical spine move in a three-dimensional (3D) manner, the 3D motions of the neural elements and their relationship to the bones surrounding them are largely unknown even for asymptomatic normal subjects. We hypothesize that abnormal mechanical loading of cervical nerve roots during pain-provoking head positioning may be responsible for radicular pain in those cases in which there is no evidence of nerve root compression on conventional cervical magnetic resonance imaging (MRI) with the neck in the neutral position. This biomechanical imaging proof-of-concept study focused on quantitatively defining the architectural relationships between the neural and bony structures in the cervical spine using measurements derived from 3D MR images acquired in neutral and pain-provoking neck positions for subjects: (1) with radicular symptoms and evidence of root compression by conventional MRI and positive EMG, (2) with radicular symptoms and no evidence of root compression by MRI but positive EMG, and (3) asymptomatic age-matched controls. Function and pain scores were measured, along with neck range of motion, for all subjects. MR imaging was performed in both a neutral position and a pain-provoking position. Anatomical architectural data derived from analysis of the 3D MR images were compared between symptomatic and asymptomatic groups, and the symptomatic groups with and without imaging evidence of root compression. Several differences in the architectural relationships between the bone and neural tissues were identified between the asymptomatic and symptomatic groups. In addition, changes in architectural relationships were also detected between the symptomatic groups with and without imaging evidence of nerve root compression. As demonstrated in the data and a case study the 3D stress MR imaging approach provides utility to identify biomechanical relationships between hard and soft tissues that are otherwise undetected by standard clinical imaging methods. This technique offers a promising approach to detect the source of radiculopathy to inform clinical management for this pathology.

Simulation of inhomogeneous rather than homogeneous poroelastic tissue material properties within disc annulus and nucleus better predicts cervical spine response: a C3-T1 finite element model analysis under compression and moment loadings

STUDY DESIGN

A finite element (FE) modeling of homogeneous and inhomogeneous poroelastic tissue material properties within disc anulus fibrosus (AF) and nucleus pulposus (NP).

OBJECTIVE

To test the hypothesis that simulation of inhomogeneous poroelastic tissue material properties within AF and NP quadrants, rather than homogeneous properties within regions of AF and NP without quadrants, would better predict the cervical spine biomechanics.

SUMMARY OF BACKGROUND DATA

In order to represent tissue swelling and creep deformation behavior more physiologically in FE models, disc poroelastic tissue material properties should be modeled appropriately. Past studies show an existence of inhomogeneous rather than homogeneous nature of the tissue properties in various quadrants of AF and NP, and this has been simulated in a single-segment FE lumbar model with only compression analysis. This article simulated these tissue properties in a multisegmental cervical spine and reported the results of both compression and moment loads.

METHODS

Two three-dimensional FE models of a C3-T1 segment were developed. Model I included homogeneous poroelastic tissue properties in AF and NP, whereas Model II included inhomogeneous poroelastic tissue properties in AF and NP quadrants. Biomechanical responses of the FE models under diurnal compression and moment loads were compared with corresponding in vivo published studies.

RESULTS

Model II with disc quadrant-based inhomogeneous poroelastic tissue properties predicted better, mainly in flexion and extension, than the Model I with homogeneous tissue properties when compared with the corresponding in vivo results, thereby confirming the current study hypothesis. Inhomogeneous tissue properties govern segmental behavior mainly during sagittal plane motions, with a root-mean-square difference of nearly 50% across the motion segments.

CONCLUSION

The current data justify the need to simulate inhomogeneous tissue properties within disc quadrants for any FE model analysis. Model II can be further used to understand the biomechanical effects of quadrant-based degenerative poroelastic tissue properties on cervical spine behavior. Future experiments are necessary to support the current study results.

Relative contributions of strain-dependent permeability and fixed charged density of proteoglycans in predicting cervical disc biomechanics: a poroelastic C5-C6 finite element model study

Disc swelling pressure (P(swell)) facilitated by fixed charged density (FCD) of proteoglycans (P(fcd)) and strain-dependent permeability (P(strain)) are of critical significance in the physiological functioning of discs. FCD of proteoglycans prevents any excessive matrix deformation by tissue stiffening, whereas strain-dependent permeability limits the rate of stress transfer from fluid to solid skeleton. To date, studies involving the modeling of FCD of proteoglycans and strain-dependent permeability have not been reported for the cervical discs. The current study objective is to compare the relative contributions of strain-dependent permeability and FCD of proteoglycans in predicting cervical disc biomechanics. Three-dimensional finite element models of a C5-C6 segment with three different disc compositions were analyzed: an SPFP model (strain-dependent permeability and FCD of proteoglycans), an SP model (strain-dependent permeability alone), and an FP model (FCD of proteoglycans alone). The outcomes of the current study suggest that the relative contributions of strain-dependent permeability and FCD of proteoglycans were almost comparable in predicting the physiological behavior of the cervical discs under moment loads. However, under compression, strain-dependent permeability better predicted the in vivo disc response than that of the FCD of proteoglycans. Unlike the FP model (least stiff) in compression, motion behavior of the three models did not vary much from each other and agreed well within the standard deviations of the corresponding in vivo published data. Flexion was recorded with maximum P(fcd) and P(strain), whereas minimum values were found in extension. The study data enhance the understanding of the roles played by the FCD of proteoglycans and strain-dependent permeability and porosity in determining disc tissue swelling behavior. Degenerative changes involving strain-dependent permeability and/or loss of FCD of proteoglycans can further be studied using an SPFP model. Future experiments are necessary to support the current study results.

Reduction in segmental flexibility because of disc degeneration is accompanied by higher changes in facet loads than changes in disc pressure: a poroelastic C5-C6 finite element investigation

BACKGROUND CONTEXT

Nerve fiber growth inside the degenerative intervertebral discs and facets is thought to be a source of pain, although there may be several other pathological and clinical reasons for the neck pain. It, however, remains difficult to decipher how much disc and facet joints contribute to overall degenerative segmental responses. Although the biomechanical effects of disc degeneration (DD) on segmental flexibility and posterior facets have been reported in the lumbar spine, a clear understanding of the pathways of degenerative progression is still lacking in the cervical spine.

PURPOSE

To test the hypothesis that after an occurrence of degenerative disease in a cervical disc, changes in the facet loads will be higher than changes in the disc pressure.

STUDY DESIGN

To understand the biomechanical relationships between segmental flexibility, disc pressure, and facet loads when the C5-C6 disc degenerates.

METHODS

A poroelastic, three-dimensional finite element (FE) model of a normal C5-C6 segment was developed and validated. Two degenerated disc models (moderate and severe) were built from the normal disc model. Biomechanical responses of the three FE models (normal, moderate, and severe) were further studied under diurnal compression (at the end of the daytime activity period) and moment loads (at the end of 5 seconds) in terms of disc height loss, angular motions, disc pressure, and facet loads (average of right and left facets).

RESULTS

Disc deformation under compression and segmental rotational motions under moment loads for the normal disc model agreed well with the corresponding in vivo studies. A decrease in segmental flexibility because of DD is accompanied by a decrease in disc pressure and an increase in facet loads. Biomechanical effects of degenerative disc changes are least in flexion. Segmental flexibility changes are higher in extension, whereas changes in disc pressure and facet loads are higher in lateral bending and axial rotation, respectively.

CONCLUSIONS

The results of the present study confirmed the hypothesis of higher changes in facet loads than in disc pressure, suggesting posterior facets are more affected than discs because of a decrease in degenerative segmental flexibility. Therefore, a degenerated disc may increase the risk of overloading the posterior facet joints. It should be clearly noted that only after degeneration simulation in the disc, we recorded the biomechanical responses of the facets and disc. Therefore, our hypothesis does not suggest that facet joint osteoarthritis may occur before degeneration in the disc. Future cervical spine-based experiments are warranted to verify the conclusions presented in this study.

Patterns of height changes in anterior and posterior cervical disc regions affects the contact loading at posterior facets during moderate and severe disc degeneration: a poroelastic C5-C6 finite element model study

STUDY DESIGN

Biomechanical roles of anterior and posterior portions of the disc (AD and PD, respectively) in governing posterior facets (PF) behavior of a C5-C6 motion segment.

OBJECTIVE

To understand how height patterns (loss and gain) at AD and PD affects the PF contact loading during moderate and severe grades of cervical disc degeneration (DD).

SUMMARY OF BACKGROUND DATA

PF overloading and degeneration after degenerative disc height loss is a clinical concern. This may occur because of a decrease in facet joints space, causing elevated PF contact forces. During a physiologic motion, axial disc height patterns at AD and PD affects the spacing and overlapping of articulating PF surfaces. The question arises as to what percentage of deformation and/or elongation at AD and PD is contributing to a corresponding increase and/or decrease in PF contact loading.

METHODS

A poroelastic, three-dimensional finite element model of a C5-C6 segment with a normal (grade I) disc was used after validation. Two degenerated disc models were developed from the normal disc model: moderate (combined effect of Thompson disc grades II and III) and severe (combined effect of Thompson disc grades IV and V). The models were analyzed under compression, flexion, and extension. Height patterns (loss and gain) at AD and PD, and PF loading were calculated for each model.

RESULTS

PF loading increased with PD height loss, and further increased with AD height gain. In moderate DD, PF loading was more affected by PD height loss than AD height gain, whereas in severe DD, it was more affected by AD height gain than PD height loss.

CONCLUSION

The current study conclusions suggest a possible mechanism for PF loading through loss and gain in the AD and PD heights during moderate and severe grades of DD. Further cervical spine based biomechanical investigations are suggested to verify our findings.

The length of the cervical cord: effects of postural changes in healthy volunteers using positional magnetic resonance imaging

STUDY DESIGN

The length of the cervical cord in healthy volunteers was measured in the supine and erect position using positional magnetic resonance imaging (MRI).

OBJECTIVE

To assess the relationship between the length of the cervical cord and cervical posture in healthy volunteers.

SUMMARY OF BACKGROUND DATA

A number of detailed descriptions of the normal morphologic features of the cervical cord have been published. However, to our knowledge, there is no report to compare the relationship between the length of the cervical cord and cervical posture in healthy volunteers using positional MRI.

METHODS

This study was performed on 20 healthy volunteers using positional MRI. The subjects were studied in the supine and erect positions. The recumbent series consisted of 3 positions: neutral, flexion, and extension. The erect series consisted of 3 positions: neutral, flexion, and extension. On the midsagittal image, the length of the cervical cord from C1 to C7 was measured at the anterior, middle, and posterior line. The angle of the lower-endplate of C2 and C7 was measured. The results were compared with each series.

RESULTS

In the recumbent and erect series, the mean length of the cervical cord in flexion was longer than in neutral and extension at the anterior, middle, and posterior line. There were significant differences between the length of the cervical cord in flexion, neutral, and extension. The mean length of the cervical cord in extension was shorter than in neutral and flexion at the anterior, middle, and posterior line. There were significant differences between length of the cervical cord in extension, neutral, and flexion.

CONCLUSIONS

We found posture-dependent differences of the length of the cervical cord in the recumbent and erect series. These results may be important when assessing the dynamic factor in cervical spondylotic myelopathy.