Influence of microsurgical decompression on segmental stability of the lumbar spine - One-year results in a prospective, consecutive case series using upright, kinetic-positional MRI

Background

Standard procedure in patients with lumbar spinal canal stenosis is decompression to relieve the neural structures. Clinical results generally show superiority compared to nonoperative therapy after an observation period of several years. However, there is still a question of postsurgical segmental stability and correlation to clinical findings. Therefore, the aim of this prospective study was to evaluate the clinical outcome in patients who underwent microsurgical decompression in lumbar spine and particularly to analyze intervertebral movement by use of upright, kinetic-positional magnetic resonance imaging (MRI) over a period of 12 months and then to correlate the clinical and imaging data with each other.

Methods

Complete clinical data of 24 consecutive participants with microsurgical decompression of the lumbar spine were obtained by questionnaires including visual analogue scale (VAS) for back and leg, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), Short-Form-36 (SF-36), walking distance and use of analgesics with assessment preoperatively and after 6 weeks and 12 months. At the same points of time all patients underwent upright, kinetic-positional MRI to measure intersegmental motion of the operated levels with determination of intervertebral angles and translation and to correlate the clinical and imaging data with each other.

Results

VAS for leg, ODI, RMDQ and physical component scale of SF-36 improved statistically significantly without statistically significant differences regarding intersegmental motion and horizontal displacement 6 weeks and 12 months after operation. Regression analysis did not find any linear dependencies between the clinical scores and imaging parameters.

Conclusions

In awareness of some limitations of the study, our results demonstrate no increase of intersegmental movement or even instability after microsurgical decompression of the lumbar spine over a follow-up period of 12 months, which is equivalent to preservation of intervertebral stability. Furthermore, the magnitude of intervertebral range of motion showed no correlation to the clinical score parameters at all three examination points of time.

Effects of standing on lumbar spine alignment and intervertebral disc geometry in young, healthy individuals determined by positional magnetic resonance imaging

BACKGROUND

Most diagnostic imaging of the spine is performed in supine, a relatively unloaded position. Although the spine is subjected to functional loading that changes the spinal alignment and intervertebral disc geometry, little data exists on how healthy spines adapt to standing. This study seeks to quantify the changes of the lumbar spine from supine to standing in young, back-healthy individuals using a positional magnetic resonance imaging system.

METHODS

This is an observational study that examined the changes in the lumbar spine alignment and intervertebral disc geometry between supine and standing of forty participants (19 males/21 females) without a history of low back pain. The regional lumbar spinal alignment was measured by the sagittal Cobb angle. Segmental intervertebral disc measurements included the segmental Cobb angle, anterior-to-posterior height ratio, and intervertebral disc width measured at L1/L2 - L5/S1 levels. Intra-class correlation was performed for intra- and inter-observer measurements.

FINDINGS

The intra-observer intra-class correlation consistency model ranged from 0.76 to 0.98 with the inter-observer correlation ranging from 0.68 to 0.99. The Cobb angle decreased in standing. The L5/S1 segmental Cobb angle decreased in standing. The L2/L3 and L3/L4 anterior-to-posterior height ratios increased and the L5/S1 anterior-to-posterior height ratio decreased in standing. No difference in intervertebral disc widths was observed from supine to standing.

INTERPRETATIONS

We established normative data for a back-healthy population, using a positional magnetic resonance imaging system, that could inform future investigations that examine the standing-induced adaptations of the lumbar spine in individuals with spinal or intervertebral disc pathologies.

MRI findings of lumbar spine instability in degenerative spondylolisthesis

PURPOSE

To find out the factors suggesting lumbar segmental instability in patients with degenerative spondylolisthesis (DS) on conventional magnetic resonance imaging (MRI).

METHODS

Ninety-four patients with DS who underwent decompression surgery with or without fusion were selected. Patient demographics and findings on simple radiographs and MRI were analyzed. We divided patients into two groups by the presence of lumbar instability on simple standing plain radiographs and measured degeneration status of intervertebral discs and facet joints and distance of facet fluid signal on T2 axial MRI on each groups. The data were analyzed to find out the correlation between facet fluid signal and lumbar instability.

RESULTS

Sixty-three patients were confirmed to have lumbar instability (unstable group (UG), 67%), while 31 patients (stable group (SG), 33%) did not have instability on simple radiographs. The mean age was slightly older in SG ( p < 0.05) and SG patients' degeneration status of intervertebral discs and facet joints was advanced than UG patients. Fifty-five of 63 patients had high signal intensity on T2-weighted MR images in the UG, but only 4 of 31 patients had high signal intensity in the SG ( p < 0.001) and UG patients have more larger facet joint distance than SG patients ( p < 0.001).

CONCLUSION

High signal in facet joints on T2 MR images can be a useful factor suggestive of lumbar instability. Thus, the identification of fluid signal in the facet joints on MRI should raise the suspicion for lumbar instability and prompt additional evaluations such as with stress radiographs.

Slump sitting X-ray of the lumbar spine is superior to the conventional flexion view in assessing lumbar spine instability

BACKGROUND CONTEXT

Flexion radiographs have been used to identify cases of spinal instability. However, current methods are not standardized and are not sufficiently sensitive or specific to identify instability.

PURPOSE

This study aimed to introduce a new slump sitting method for performing lumbar spine flexion radiographs and comparison of the angular range of motions (ROMs) and displacements between the conventional method and this new method.

STUDY DESIGN

This study used is a prospective study on radiological evaluation of the lumbar spine flexion ROMs and displacements using dynamic radiographs.

PATIENT SAMPLE

Sixty patients were recruited from a single spine tertiary center.

OUTCOME MEASURE

Angular and displacement measurements of lumbar spine flexion were carried out.

METHOD

Participants were randomly allocated into two groups: those who did the new method first, followed by the conventional method versus those who did the conventional method first, followed by the new method. A comparison of the angular and displacement measurements of lumbar spine flexion between the conventional method and the new method was performed and tested for superiority and non-inferiority.

RESULTS

The measurements of global lumbar angular ROM were, on average, 17.3° larger (p<.0001) using the new slump sitting method compared with the conventional method. They were most significant at the levels of L3-L4, L4-L5, and L5-S1 (p<.0001, p<.0001 and p=.001, respectively). There was no significant difference between both methods when measuring lumbar displacements (p=.814).

CONCLUSION

The new method of slump sitting dynamic radiograph was shown to be superior to the conventional method in measuring the angular ROM and non-inferior to the conventional method in the measurement of displacement.

The use of pMRI to validate the identification of palpated bony landmarks

Accurate palpation of lumbar spinous processes (SPs) is a key component of spinal assessment. It is also vital for the accurate measurement of spinal motion when using external skin marker-based measurement systems, which are being increasingly used to understand low back disorders and their management. The aim was to assess the accuracy of lumbar spinous process (SP) palpation using positional magnetic resonance imagery (MRI) (pMRI). Two experienced manual therapists palpated the L4 SP of nine pain-free participants in standing and prone lying. For each position, an MRI marker was attached over the SP and pMRI scanning was conducted. The position of the marker in relation to L4 on the MRI images was visually inspected, and measurements (mm) of the vertical distance from the superior/inferior aspect of the marker to the superior/inferior aspect of the L4 SP were used to determine palpation accuracy. 71% of Markers were correctly placed over the L4 SP. The magnitude of error for incorrectly placed markers was small, with the largest median distance of 2.7 mm (interquartile range (IQR) 0-3.6) recorded for one of the therapists palpating in prone lying. 100% of markers were correctly placed either on L4 or within one SP in height. pMRI is useful for investigating the accuracy of SP palpation in positions relevant to clinical and research practice.

Imaging‐based planning for spine surgery

The planning of decompressive and reconstructive spine surgery is based on clinical findings and diagnostic imaging. The evaluation of segmental instability, but also of the risk of destabilization following a needed decompression of the spinal canal and/or neural foramina make complex spine surgery a challenge, bearing in mind the risk of failures in case of an inadequate operation. The insufficient correlation between imaging and clinical symptoms originating from the spine and its nerve roots has been frustrating for some decades. This review focuses on the new upright, dynamic-kinetic, i.e., "functional" MRI and its ability to detect load- and motion-dependent disc herniations, stenosis, instabilities, and combinations of these pathologies not seen during recumbent imaging.

The Preoperative Spine: Diagnostic Work up with fMRI

The advantages of the upright, open, multi-positional MRI, i.e. functional MRI (fMRI) are presented with illustrative cases and the literature is reviewed. In cases of not explained and especially in position-dependent spinal and/or neurological pain and/or dysfunction functional or dynamic MRI is able to reveal dynamic compressions/stenosis, as well as segmental dysfunction and instabilities in a noninvasive way. This new technology could become mandatory for the preoperative investigation of unexplained, mainly "dynamic, mobile or unstable" spinal pathologies. Allowing a better correlation of signs and symptoms with the imaging findings and thus a more targeted treatment, fMRI could help to decrease the rate of failed back surgery syndrome in the near future.

An open-access, very-low-field MRI system for posture-dependent 3He human lung imaging

We describe the design and operation of an open-access, very-low-field, magnetic resonance imaging (MRI) system for in vivo hyperpolarized 3He imaging of the human lungs. This system permits the study of lung function in both horizontal and upright postures, a capability with important implications in pulmonary physiology and clinical medicine, including asthma and obesity. The imager uses a bi-planar B(0) coil design that produces an optimized 65 G (6.5 mT) magnetic field for 3He MRI at 210 kHz. Three sets of bi-planar coils produce the x, y, and z magnetic field gradients while providing a 79-cm inter-coil gap for the imaging subject. We use solenoidal Q-spoiled RF coils for operation at low frequencies, and are able to exploit insignificant sample loading to allow for pre-tuning/matching schemes and for accurate pre-calibration of flip angles. We obtain sufficient SNR to acquire 2D 3He images with up to 2.8mm resolution, and present initial 2D and 3D 3He images of human lungs in both supine and upright orientations. 1H MRI can also be performed for diagnostic and calibration reasons.

Posture-dependent human 3He lung imaging in an open-access MRI system: initial results

RATIONALE AND OBJECTIVES

The human lung and its functions are extremely sensitive to orientation and posture, and debate continues as to the role of gravity and the surrounding anatomy in determining lung function and heterogeneity of perfusion and ventilation. However, study of these effects is difficult. The conventional high-field magnets used for most hyperpolarized (3)He magnetic resonance imaging (MRI) of the human lung, and most other common radiologic imaging modalities including positron emission tomography and computed tomography, restrict subjects to lying horizontally, minimizing most gravitational effects.

MATERIALS AND METHODS

In this article, we review the motivation for posture-dependent studies of human lung function and present initial imaging results of human lungs in the supine and vertical body orientations using inhaled hyperpolarized (3)He gas and an open-access MRI instrument. The open geometry of this MRI system features a "walk-in" capability that permits subjects to be imaged in vertical and horizontal positions and potentially allows for complete rotation of the orientation of the imaging subject in a two-dimensional plane.

RESULTS

Initial results include two-dimensional lung images acquired with approximately 4 x 8 mm in-plane resolution and three-dimensional images with approximately 2-cm slice thickness.

CONCLUSIONS

Effects of posture variation are observed, including posture-related effects of the diaphragm and distension of the lungs while vertical.

The response of the nucleus pulposus of the lumbar intervertebral discs to functionally loaded positions

STUDY DESIGN

Asymptomatic volunteers underwent magnetic resonance imaging to investigate how different positions affect lumbar intervertebral discs.

OBJECTIVE

To quantify sagittal migration of the lumbar nucleus pulposus in 6 functional positions.

SUMMARY OF BACKGROUND DATA

Previous studies of the intervertebral disc response in the sagittal plane were limited to imaging of recumbent positions. Developments of upright magnetic resonance imaging permit investigation of functional weight-bearing positions.

METHODS

T2-weighted sagittal scans of the L1-L2 to L5-S1 discs were taken of 11 volunteers in standing, sitting (upright, flexed, and in extension), supine, and prone extension. Sagittal migration of the nucleus pulposus was measured (mm) as distance from anterior disc boundary to peak pixel intensity. Lumbar lordosis (Cobb angle) was measured in each position.

RESULTS

Fifteen comparisons between positions showed significant positional effects (14 at L4-L5, L5-S1, the most mobile segments). Prone extension and supine lying induced significantly less posterior migration than sitting. Flexed and upright sitting, significantly more than standing at L4-L5, as did flexed sitting compared with extended.

CONCLUSION

These results support for the first time the validity of clinical assumptions about disc behavior in functional positions: sitting postures may increase risk of posterior derangement, and prone and supine may be therapeutic for symptoms caused by posterior disc displacement.

Evaluation of intervertebral disc herniation and hypermobile intersegmental instability in symptomatic adult patients undergoing recumbent and upright MRI of the cervical or lumbosacral spines

PURPOSE

The purpose of the study was to determine the difference in findings between recumbent and upright-sitting MRI of the cervical and lumbosacral spine in patients with related sign and symptoms.

MATERIALS AND METHODS

A total of 89 patients were studied (lumbosacral spine: 45 patients; cervical: 44 patients). T1-weighted (TR: 350, TE: 20) fast spin echo and T2-weighted (TR: 2500, TE: 160) fast spin echo images were acquired in the sagittal and axial planes in both the recumbent and sitting-neutral positions. The images were acquired on the Upright MRI unit (Fonar Corporation, Melville, NY). Differences were sought between the recumbent and upright-sitting positions at all levels imaged, in both planes.

RESULTS

The total number of cases of pathology was 68, including instances of posterior disc herniation and anterior and posterior spondylolisthesis. Focal posterior disc herniations were noted in 55 patients (cervical: 31, lumbosacral: 24) [62% of patients]. Six of these herniations (cervical: 4, lumbosacral: 2) [11%] were seen only on the upright-sitting study. Focal posterior disc herniations were seen to comparatively enlarge in size in 35 patients on the upright-seated examination (cervical: 21, lumbosacral: 14) [72%], and reduce in size in 9 patients (cervical: 5, lumbosacral: 4) [18%]. Degenerative anterior (n: 11) and posterior (n: 2) spondylolisthesis was seen in 13 patients (cervical: 0, lumbosacral: 13) [15% of patient total]. Anterior spondylolisthesis was only seen on the upright-seated examination in 4 patients (cervical: 0, lumbosacral: 4) [31%]. Anterior spondylolisthesis was comparatively greater in degree on the upright-seated study in 7 patients (cervical: 0, lumbosacral: 7) [54%]. Posterior spondylolisthesis was comparatively greater in degree on the recumbent examination in 2 patients (cervical: 0, lumbosacral: 2) [15%]. The overall combined recumbent miss rate in cases of pathology was 15% (10/68). The overall combined recumbent underestimation rate in cases of pathology was 62% (42/68). The overall combined upright-seated underestimation in cases of pathology was 16% (11/69).

CONCLUSIONS

Overall, upright-seated MRI was found to be superior to recumbent MRI of the spine in 52 patents (recumbent missed pathology [n: 10]+recumbent underestimated pathology [n: 42]=52/89 total patients: 58%) in cases of posterior disc herniation and anterior spondylolisthesis. This seems to validate the importance of weight-bearing imaging in the spine that might be expected to unmask positional enlarging disc herniations and worsening spondylolisthesis. Overall, recumbent MRI was found to be superior to upright-seated MRI in 11 cases (11/89: 12%). The latter finding was possibly due to the fact that upright seated position is actually partial flexion that might be expected to reduce some cases of hypermobile posterior spondylolisthesis.

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.

Magnetic resonance imaging study of the level of termination of the conus medullaris and the thecal sac: influence of age and gender

STUDY DESIGN

Sequential study of magnetic resonance imaging (MRI) of the spine for assessing the level of termination of the conus medullaris (CMT) and thecal sac (TST).

OBJECTIVES

To determine the variation in CMT and the TST as a function of age and gender in an adult population without spinal deformity and to investigate the relationship between CMT and TST.

SUMMARY OF BACKGROUND DATA

It is generally accepted that the conus medullaris terminates in the lower third of L1; however, a wide range of values has been reported in cadaver studies as well as in MRI studies during life. There have been only a few reports on the influence of gender on the CMT, and the influence of age has not been studied at all. There have been few studies on the range of termination of the thecal sac, and the influence of age and gender remain unexplored.

METHODS

We reviewed the 3-mm sagittal MR images of 635 patients, including 297 women and 338 men, with a mean age of 49.43 years. The CMT and TST were located in relation to spinal levels and assigned numerical values ranging from 0 to 13. Parametric and nonparametric statistical tests were used for the data analysis.

RESULTS

Mean CMT was at the level of the middle third of L1. The range span extended from the lower third of Th11 to the upper third of L3. The CMT displayed a small but significant positive correlation with age and with gender. Mean TST was at the level of the upper third of S2. The range extended from the lower third of L3 to the upper third of S5. The TST was not affected by gender, but age had an effect on TST.

CONCLUSIONS

The CMT and TST displayed a wide range of values in our study. We detected small but systematic influences of gender and age on CMT and of age on TST, as well as a positive correlation between CMT and TST. These effects are small in amplitude, but they met all the criteria for statistical significance and have practical value for clinicians, as well as theoretical value for the medical and biologic community.

Upright, weight-bearing, dynamic-kinetic MRI of the spine: initial results

The potential relative beneficial aspects of upright, weight-bearing (pMRI), dynamic-kinetic (kMRI) spinal imaging over that of recumbent MRI (rMRI) include the revelation of occult spinal disease dependent on true axial loading, the unmasking of kinetic-dependent spinal disease and the ability to scan the patient in the position of clinically relevant signs and symptoms. This imaging unit under study also demonstrated low claustrophobic potential and yielded comparatively high resolution images with little motion/magnetic susceptibility/chemical shift artifact. Overall, it was found that rMRI underestimated the presence and maximum degree of gravity-dependent spinal pathology and missed altogether pathology of a dynamic nature, factors that are optimally revealed with p/kMRI. Furthermore, p/kMRI enabled optimal linkage of the patient's clinical syndrome with the medical imaging abnormality responsible for the clinical presentation, thereby allowing for the first time an improvement at once in both imaging sensitivity and specificity.