The narrowing of the lumbar spinal canal during loaded MRI: the effects of the disc and ligamentum flavum

Histopathological Analysis of Ligamentum Flavum in Lumbar Spinal Stenosis and Disc Herniation

Study Design

Histopathological analyses were performed in ligamentum flavum (LF) hypertrophy patients with lumbar spinal stenosis (LSS) and lumbar disc herniation (LDH).

Purpose

The aim of the present study was to evaluate histopathological changes in LF patients with LSS and LDH.

Overview of Literature

LSS is the most common spinal disorder in elderly patients. This condition causes lower back and leg pain and paresis, and occurs as a result of degenerative changes in the lumbar spine, including bulging of the intervertebral discs, bony proliferation of the facet joints, and LF thickening; among these, LF thickening is considered a major contributor to the development of LSS.

Methods

A total of 71 patients operated with the surgical indications of LSS and LDH were included. LF samples were obtained from 31 patients who underwent decompressive laminectomy for symptomatic degenerative LSS (stenotic group) and from 40 patients who underwent lumbar discectomy for LDH (discectomy group). LF materials were examined histopathologically, and other specimens were examined for collagen content, elastic fiber number and array, and presence of calcification.

Results

The stenotic and discectomy groups did not differ with regard to mean collagen concentration or mean elastic fiber number (p=0.430 and p=0.457, respectively). Mean elastic fiber alignment was 2.36±0.99 in the stenotic group and 1.38±0.54 in the discectomy group (p<0.001). Mean calcification was 0.39±0.50 in the stenotic group, whereas calcification was not detected (0.00±0.00) in the discectomy group; a statistically significant difference was detected (p<0.001) between groups.

Conclusions

LF hypertrophy in spinal stenosis may occur as a result of elastic fiber misalignment along with the development of calcification over time. Further studies determining the pathogenesis of LSS are needed.

Tumor Occupation in the Spinal Canal and Clinical Symptoms of Cauda Equina Schwannoma: An Analysis of 22 Cases

STUDY DESIGN

Retrospective, radiological study.

PURPOSE

To determine the relationship between clinical symptoms and the extent of tumor occupation of the spinal canal by cauda equina schwannoma.

OVERVIEW OF LITERATURE

Little is known about the relationship between the size of tumors of the cauda equina and the manifestation of clinical symptoms. We analyzed this relationship by estimating the percentage of tumor occupation (PTO) in the spinal canal in cauda equina schwannomas and by correlating this parameter with the presence and severity of clinical symptoms.

METHODS

Twenty-two patients (9 men and 13 women; age, 19-79 years; mean age, 55.3 years) who were radiologically diagnosed with schwannomas of the cauda equina between April 2004 and July 2014 were retrospectively analyzed. PTO was measured in axial and sagittal magnetic resonance imaging slices in which the cross-sectional area of the tumor was the largest. Data regarding clinical symptoms and results of physical examinations were collected from patient medical records. PTO differences between symptom-positive and -negative groups were analyzed for each variable.

RESULTS

In the 4 cases in which tumor presence was not related to clinical symptoms, PTO was 5%-10% (mean, 9%) in axial slices and 23%-31% (mean, 30%) in sagittal slices. In the 18 cases in which symptoms were associated with the tumor, PTO was 11%-86% (mean, 50%) in axial slices and 43%-88% (mean, 71%) in sagittal slices. PTO in axial slices was significantly higher in the presence of Déjèrine symptoms and/or muscle weakness, a positive straight leg raise test, and a positive Kemp sign.

CONCLUSIONS

PTO >20% in axial slices and >40% in sagittal slices can be an indication of symptomatic cauda equina schwannoma.

The paradoxical relationship between ligamentum flavum hypertrophy and developmental lumbar spinal stenosis

Background

Ligamentum flavum (LF) hypertrophy is a common cause of lumbar spinal stenosis and is thought to be degeneration-driven. Developmental spinal stenosis (DSS) is characterized by pre-existing narrowed spinal canals and is likely a developmental problem that occurs in childhood. In these cases, the LF may demonstrate different characteristics as compared to degeneration-driven stenosis. Thus, this study aimed to investigate the relationship between histological changes of LF and canal size.

Methods

Patients who had surgical decompression for lumbar spinal stenosis were prospectively recruited and divided into three groups (critical DSS, relative DSS and non-DSS) based on previously defined anteroposterior bony spinal canal diameter measurements on MRI. The degree of disc degeneration and LF thickness were also measured from L1 to S1. Surgical LF specimens were retrieved for histological assessment of fibrotic grade and area of fibrosis.

Results

A total of 19 females and 15 males (110 LF specimens) with an overall mean age of 65.9 years (SD ± 9.8 years) were recruited. DSS was found to have a significant negative correlation (p < 0.001) with LF thickness, its fibrotic grade and area of fibrosis (%). Non-DSS exhibited a significant positive relationship with the degree of LF fibrosis. Disc degeneration and LF thickness had no correlation with LF histology.

Conclusions

Our study is the first to definitively note that degeneration is the cause of LF fibrosis in non-DSS patients; however, in contrast, an inverse relationship exists between canal size and LF fibrosis in DSS patients, suggesting a different pathomechanism. Hence, despite a similar degree of LF thickness, DSS patients have LF with less fibrosis compared with non-DSS patients. Further investigation of the cause of LF changes in DSS is necessary to understand this relationship.

Deconstructing Chronic Low Back Pain in the Older Adult-Step by Step Evidence and Expert-Based Recommendations for Evaluation and Treatment. Part VI: Lumbar Spinal Stenosis

OBJECTIVE

. To present the sixth in a series of articles designed to deconstruct chronic low back pain (CLBP) in older adults. This article focuses on the evaluation and management of lumbar spinal stenosis (LSS), the most common condition for which older adults undergo spinal surgery.

METHODS

. The evaluation and treatment algorithm, a table articulating the rationale for the individual algorithm components, and stepped-care drug recommendations were developed using a modified Delphi approach. The Principal Investigator, a five-member content expert panel and a nine-member primary care panel were involved in the iterative development of these materials. The illustrative clinical case was taken from the clinical practice of a contributor's colleague (SR).

RESULTS

. We present an algorithm and supportive materials to help guide the care of older adults with LSS, a condition that occurs not uncommonly in those with CLBP. The case illustrates the importance of function-focused management and a rational approach to conservative care.

CONCLUSIONS

. Lumbar spinal stenosis exists not uncommonly in older adults with CLBP and management often can be accomplished without surgery. Treatment should address all conditions in addition to LSS contributing to pain and disability.

Ablation of porcine ligamentum flavum with Ho:YAG, q-switched Ho:YAG, and quadrupled Nd:YAG lasers

BACKGROUND AND OBJECTIVES

Ligamentum flavum (LF) is a tough, rubbery connective tissue providing a portion of the ligamentous stability to the spinal column, and in its hypertrophied state forms a significant compressive pathology in degenerative spinal stenosis. The interaction of lasers and this biological tissue have not been thoroughly studied. Technological advances improving endoscopic surgical access to the spinal canal makes selective removal of LF using small, flexible tools such as laser-coupled fiber optics increasingly attractive for treatment of debilitating spinal stenosis. Testing was performed to assess the effect of Ho:YAG, Q-switched Ho:YAG, and frequency quadrupled Nd:YAG lasers on samples of porcine LF. The objective was to evaluate the suitability of these lasers for surgical removal of LF.

STUDY DESIGN/MATERIALS AND METHODS

LF was resected from porcine spine within 2 hours of sacrifice and stored in saline until immediately prior to laser irradiation, which occurred within an additional 2 hours. The optical absorbance of a sample was measured over the spectral band from 190 to 2,360 nm both before and after dehydration. For the experiments using the Ho:YAG (λ = 2,080 nm, tp  = 140 µs, FWHM) and Q-Switched Ho:YAG (λ = 2,080 nm, tp  = 260 ns, FWHM) lasers, energy was delivered to the LF through a laser-fiber optic with 600 µm core and NA = 0.39. For the experiment using the frequency quadrupled Nd:YAG laser (λ = 266 nm, tp  = 5 ns FWHM), rather than applying the laser energy through a laser-fiber, the energy was focused through an aperture and lens directly onto the LF. Five experiments were conducted to evaluate the effect of the given lasers on LF. First, using the Ho:YAG laser, the single-pulse laser-hole depth versus laser fluence was measured with the laser-fiber in direct contact with the LF (1 g force) and with a standoff distance of 1 mm between the laser-fiber face and the LF. Second, with the LF remaining in situ and the spine bisected along the coronal plane, the surface temperature of the LF was measured with an IR camera during irradiation with the Ho:YAG laser, with and without constant saline flush. Third, the mass loss was measured over the course of 450 Ho:YAG pulses. Fourth, hole depth and temperature were measured over 30 pulses of fixed fluence from the Ho:YAG and Q-Switched Ho:YAG lasers. Fifth, the ablation rate and surface temperature were measured as a function of fluence from the Nd:YAG laser. Several LF staining and hole-depth measurement techniques were also explored.

RESULTS

Aside from the expected absorbance peaks corresponding to the water in the LF, the most significant peaks in absorbance were located in the spectral band from 190 to 290 nm and persisted after the tissue was dehydrated. In the first experiment, using the Ho:YAG laser and with the laser-fiber in direct contact with the LF, the lowest single-pulse fluence for which LF was visibly removed was 35 J/cm(2) . Testing was conducted at 6 fluences between 35 and 354 J/cm(2) . Over this range the single-pulse hole depth was shown to be near linear (R(2)  = 0.9374, M = 1.6), ranging from 40 to 639 µm (N = 3). For the case where the laser-fiber face was displaced 1 mm from the LF surface, the lowest single-pulse fluence for which tissue was visibly removed was 72 J/cm(2) . Testing was conducted at 4 energy densities between 72 and 180 J/cm(2) . Over this range the single-pulse hole depth was shown to be near linear (R(2)  = 0.8951, M = 1.4), ranging from 31 to 220 µm (N = 3). In the second experiment, with LF in situ, constant flushing with room temperature saline was shown to drastically reduce surface temperature during exposure to Ho:YAG at 5 Hz with the laser-fiber in direct contact with the LF. Without saline, over 1 minute of treatment with a per-pulse fluence of 141 mJ/cm(2) , the average maximum surface temperature measured 110°C. With 10 cc's of saline flushed over 1 minute and a per-pulse laser fluence of 212 mJ/cm(2) , the average maximum surface temperature was 35°C. In the third experiment, mass loss was shown to be linear over 450 pulses of 600 mJ from the Ho:YAG laser (212 J/cm(2) , direct contact, N = 4; 108 J/cm(2) , 1 mm standoff, N = 4). With the laser-fiber in direct contact, an average of 53 mg was removed (R(2)  = 0.996, M = 0.117) and with 1 mm laser-fiber standoff, an average of 44 mg was removed (R(2)  = 0.9988, M = 0.097). In the fourth experiment, 30 pulses of the Ho:YAG and Q-Switched Ho:YAG lasers at 1 mm standoff, and 5 Hz produced similar hole depths for the tested fluences of 9 J/cm(2) (151 and 154 µm, respectively) and 18 J/cm(2) (470 and 442 µm, respectively), though the Ho:YAG laser produced significantly more carbonization around the rim of the laser-hole. The increased carbonization was corroborated by higher measured LF temperature. In all tests with the Ho:YAG and Q-Switched Ho:YAG, an audible photo-acoustic affect coincided with the laser pulse. In the fifth experiment, with the frequency quadrupled Nd:YAG laser at 15 Hz for 450 pulses, ablation depth per pulse was shown to be linear for the fluence range of 0.18 - 0.73 J/cm(2) (R(2)  = 0.989, M = 2.4). There was no noticeable photo-acoustic effect nor charring around the rim of the laser-hole.

CONCLUSION

The Ho:YAG, Q-Switched Ho:YAG, and frequency quadrupled Nd:YAG lasers were shown to remove ligamentum flavum (LF). A single pulse of the Ho:YAG laser was shown to cause tearing of the tissue and a large zone of necrosis surrounding the laser-hole. Multiple pulses of the Ho:YAG and Q-Switched Ho:YAG lasers caused charring around the rim of the laser-hole, though the extent of charring was more extensive with the Ho:YAG laser. Charring caused by the Ho:YAG laser was shown to be mitigated by continuously flushing the affected LF with saline during irradiation. The Nd:YAG laser was shown to ablate LF with no gross visible indication of thermal damage to surrounding LF.

Increased Facet Fluid Predicts Dynamic Changes in the Dural Sac Size on Axial-Loaded MRI in Patients with Lumbar Spinal Canal Stenosis

BACKGROUND AND PURPOSE

Axial-loaded MR imaging, which simulates the spinal canal in a standing position, demonstrates reductions of the dural sac cross-sectional area in patients with lumbar spinal canal stenosis. However, there has been no useful conventional MR imaging finding for predicting a reduction in the dural sac cross-sectional area on axial-loaded MR imaging. Previous studies have shown that increased facet fluid is associated with the spinal instability detected during positional changes. The purpose of this study was to analyze the correlations between facet fluid and dynamic changes in the dural sac cross-sectional area on axial-loaded MR imaging.

MATERIALS AND METHODS

In 93 patients with lumbar spinal canal stenosis, the dural sac cross-sectional area was measured by using axial images of conventional and axial-loaded MR imaging. Changes in the dural sac cross-sectional area induced by axial loading were calculated. The correlation between the facet fluid width measured on conventional MR imaging and the change in dural sac cross-sectional area was analyzed. The change in the dural sac cross-sectional area was compared between the intervertebral levels with and without the facet fluid width that was over the cutoff value determined in this study.

RESULTS

The dural sac cross-sectional area was significantly smaller on axial-loaded MR imaging than on conventional MR imaging. The facet fluid width significantly correlated with the change in the dural sac cross-sectional area (r = 0.73, P < .001). The change in the dural sac cross-sectional area at the intervertebral level with the facet fluid width over the cutoff value was significantly greater than that at the other level.

CONCLUSIONS

The increased facet fluid on conventional MR imaging is highly predictive of the dynamic reduction of dural sac cross-sectional area detected on axial-loaded MR imaging in the clinical assessment of lumbar spinal canal stenosis.

Changes in lumbar spondylolisthesis on axial-loaded MRI: do they reproduce the positional changes in the degree of olisthesis observed on X-ray images in the standing position?

BACKGROUND CONTEXT

Axial-loaded magnetic resonance imaging (MRI) can partially simulate the lumbar spine in patients in a standing position and potentially provides additional imaging findings that cannot be obtained with conventional MRI in the clinical assessment of patients with degenerative lumbar disease. Previous studies have shown that axial-loaded MRI demonstrates a significant reduction in the size of the dural sac compared with conventional MRI. However, there has been no study to compare the degree of olisthesis among conventional MRI, axial-loaded MRI, and upright X-ray imaging in patients with degenerative spondylolisthesis (DS).

PURPOSE

The purpose of the study is to determine whether axial-loaded MRI can demonstrate similar positional changes in lumbar olisthesis as those detected on upright lateral X-ray in patients with DS.

STUDY DESIGN

This is an imaging cohort study.

PATIENT SAMPLE

A total of 43 consecutive patients with DS exhibiting olisthesis of 3 mm or more on X-ray images in the standing position were prospectively evaluated in this study.

OUTCOME MEASURES

The degree of olisthesis, intraclass correlation coefficient (ICC), and percentage of patients exhibiting olisthesis of 3 mm or more on MRI.

METHODS

The degree of olisthesis was measured on conventional MRI, axial-loaded MRI, and lateral X-ray imaging performed in the upright position. The degree of olisthesis was compared among the three imaging techniques. The ICC values for the measurements of olisthesis between X-ray studies and conventional and axial-loaded MRI were calculated and compared. The percentage of patients exhibiting olisthesis of 3 mm or more was compared between conventional MRI and axial-loaded MRI.

RESULTS

The degree of olisthesis on axial-loaded MRI (5.9±2.5 mm) was significantly greater than that observed on conventional MRI (4.4±2.4 mm) (p<.05) although the degrees on conventional and axial-loaded MRI were significantly smaller than that on upright X-ray images (7.1±2.8 mm) (p<.05). The ICC between axial-loaded MRI and X-ray imaging (0.75, 95% confidence interval: 0.58-0.85) was considerably greater than that observed between conventional MRI and X-ray imaging (0.40, 95% confidence interval: 0.11-0.62). The percentage of patients exhibiting olisthesis of 3 mm or more was significantly higher on axial-loaded MRI (91%) than on conventional MRI (63%) (p<.01).

CONCLUSIONS

Axial-loaded MRI demonstrates a significantly larger degree of olisthesis than conventional MRI. In addition, the degree of olisthesis on axial-loaded MRI was found to be more strongly correlated with that observed on X-ray studies in the upright position. Furthermore, the use of axial-loaded MRI significantly reduced the misdiagnosis of olisthesis of 3 mm or more that was detected on X-ray imaging. These results suggest that axial-loaded MRI may be superior to identify the olisthesis of the lumbar spine and show the degrees of olisthesis correlated to those detected on upright X-ray imaging. Further studies should be needed to clarify the actual value of these findings on axial-loaded MRI and provide the evidence to support its clinical significance in the assessment of patients with DS.

Ligamentum flavum hypertrophy in asymptomatic and chronic low back pain subjects

Purpose

To examine ligamentum flavum thickness using magnetic resonance (MR) images to evaluate its association with low back pain symptoms, age, gender, lumbar level, and disc characteristics.

Materials and Methods

Sixty-three individuals were part of this IRB-approved study: twenty-seven with chronic low back pain, and thirty-six as asymptomatic. All patients underwent MR imaging and computed tomography (CT) of the lumbar spine. The MR images at the mid-disc level were captured and enlarged 800% using a bilinear interpolation size conversion algorithm that allowed for enhanced image quality. Ligamentum flavum thickness was assessed using bilateral medial and lateral measurements. Disc height at each level was measured by the least-distance measurement method in three-dimensional models created by CT images taken of the same subject. Analysis of variance and t-tests were carried out to evaluate the relationship between ligamentum flavum thickness and patient variables.

Results

Ligamentum flavum thickness was found to significantly increase with older age, lower lumbar level, and chronic low back pain (p < 0.03). No difference in ligamentum flavum thickness was observed between right and left sided measurements, or between male and female subjects. Disc height and both ligamentum flavum thickness measurements showed low to moderate correlations that reached significance (p < 0.01). Additionally, a moderate and significant correlation between disc degeneration grade and ligamentum flavum thickness does exist (p <0.001).

Conclusion

By measuring ligamentum flavum thickness on MR images at two different sites and comparing degrees of disc degeneration, we found that ligamentum flavum thickness may be closely related to the pathogenesis of pain processes in the spine.

Chondrogenic and fibrotic process in the ligamentum flavum of patients with lumbar spinal canal stenosis

STUDY DESIGN

A histological, biological, and immunohisto-chemical study of human lumbar ligamentum flavum.

OBJECTIVE

To analyze changes in the hypertrophied ligamentum flavum and clarify their etiology.

SUMMARY OF BACKGROUND DATA

Hypertrophy of the ligamentum flavum has been considered a major contributor to the development of lumbar spinal canal stenosis (LSCS). Although previous studies have reported some factors related to ligamentum flavum hypertrophy, its etiology is still unclear.

METHODS

Ligamentum flavum samples were collected from 20 patients with LSCS (LSCS group) and 10 patients with lumbar disc herniation (LDH group) as a control. The thickness of the ligamentum flavum was measured histologically. The amounts of elastic fibers and proteoglycans were assessed by Elastica-Masson staining and alcian blue staining, respectively. Gene and protein expressions related to fibrosis, inflammation, and chondrogenesis were analyzed by quantitative reverse transcription-polymerase chain reaction and immunohistochemistry. The total genes of the 2 groups were compared by DNA microarray analysis.

RESULTS

The ligamentum flavum was significantly thicker in the LSCS group, which had a smaller amount of elastic fibers and a larger amount of proteoglycans. The gene expression related to fibrosis was significantly higher in the LSCS group; however, the immunoreactivities of collagen types I and III were weaker on the dorsal side of the ligamentum flavum in the LSCS group. The gene expression related to chondrogenesis and proteoglycan synthesis was significantly higher in the LSCS group. There was no significant difference in the gene expression related to inflammation between the 2 groups.

CONCLUSION

Synthesis of the collagenous fibers and degradation of the elastic and collagenous fibers are both accelerated in the ligamentum flavum of patient with LSCS, which may be the reason for hypertrophy of the tissue. In addition, chondrogenesis and proteoglycan synthesis may have critical roles in the pathogenesis of the ligamentum flavum hypertrophy.

LEVEL OF EVIDENCE

5.

Microdiskectomy and translaminar approach: minimal invasiveness and flavum ligament preservation

Study Design Retrospective study. Objective The interlaminar approach represents the standard procedure for the surgical treatment of lumbar disk herniation (LDH). In the case of disk herniations in the "hidden zone," it could be necessary to perform laminotomies or laminectomies and partial or total facetectomies to remove the herniated fragment, thus leading to iatrogenic instability. The objective of the study is to evaluate the translaminar approach, in terms of the results, safety, and efficacy compared with the standard approach. Methods Since February 2010, 38 patients (26 men and 12 women; mean age 50.9 years, range 31 to 78 years) with LDH and migration into the hidden zone underwent a microdiskectomy by the translaminar approach. Using a micro-diamond dust-coated burr, a translaminar hole (8 ± 2 mm) was made, with subsequent exposure of the involved root and removal of the fragment. A clinical follow-up was performed at months 1, 3, 6, and 12 using the visual analog scale and the Oswestry Disability Index. All patients were evaluated according to the Spangfort score. Postoperative radiographic evaluations were done at 1, 6, and 12 months (dynamic radiographic studies done at 6 and 12 months). Results In over 60% of cases, L4-L5 was the involved disk. The visualization of the roots was successfully achieved through a translaminar approach. No laminotomies, laminectomies, or partial or total facetectomies were performed. The flavum ligament was always spared. A severe intraoperative bleeding episode occurred in 5% of the cases, due to involvement of the epidural veins, but it did not result in prolonged operative time (mean duration 60 ± 10 minutes). The patients showed a gradual resolution of the back pain and a progressive resolution of the radicular pain and the neurologic deficits. No sign of radiographic instability was documented during the follow-up. No infections, dural tears, or spinal cord injuries occurred. No revision surgery was performed. Conclusion The translaminar approach is the only tissue-sparing technique viable in case of cranially migrated LDH encroaching on the exiting nerve root in the preforaminal zones, for the levels above L2-L3, and in the preforaminal and foraminal zones, for the levels below L3-L4 (L5-S1 included, if a total microdiskectomy is not necessary). The possibility to spare the flavum ligament is one of the main advantages of this technique. According to our experience, the translaminar approach is an effective and safe alternative minimally invasive surgical option.

Comparison between pain at discography and morphological disc changes at axial loaded MRI in patients with low back pain

PURPOSE

Discogenic pain is induced by axial load, but there are no studies evaluating the influence of dynamic MRI in relation to provoked pain at discography. The aim of this study was to investigate the relationship between discography-induced pain and morphological disc changes, occurring during axial loaded MRI (alMRI). A secondary aim was to compare and register the frequency of provoked concordant pain at alMRI and discography.

METHODS

41 patients with assumed discogenic pain were investigated with MRI, alMRI and pressure-controlled discography (PCD) (119 discs). Provoked pain at both discography and alMRI was classified as concordant or discordant with daily pain as reference. A concordant discogram required pain intensity ≥5/10 (numerical rating scale) at ≤50 psi and one negative control disc. A concordant provocation at alMRI required pain intensity ≥5/10. The relationship between concordant pain at discography and morphological disc measures (degeneration, height, bulge, angle, area, and circumference) at MRI/alMRI was investigated.

RESULTS

Changes in the morphological appearance occurred in at least one disc level in all patients when loaded and unloaded MRI were compared. However, no significant differences between concordant and discordant discograms in terms of morphological disc features at conventional MRI or alMRI were found. 78 % of the patients reported concordant provoked pain during the alMRI.

CONCLUSIONS

In the majority of patients with low back pain, discography as well as alMRI provoked concordant pain. Loading of the spine, alMRI, revealed however no clinically useful morphological characteristics in the discs with concordant discograms. Alternative or more sensitive diagnostic methods are needed to understand load-induced discogenic pain.

Can recumbent magnetic resonance imaging replace myelography or computed tomography myelography for detecting lumbar spinal stenosis?

OBJECTIVE

To compare the diagnostic efficacy of recumbent magnetic resonance imaging (MRI), computed tomography myelography (CTM), and myelography, with regard to indications for surgery for lumbar stenosis.

BACKGROUND DATA

In patients with lumbar spinal stenosis-like disorders, small compressions are sometimes observed in magnetic resonance images acquired in the recumbent position, leading to potential misdiagnosis. Few prospective studies have compared the diagnostic accuracy of MRI, myelography, and CTM. Therefore, it is not clear whether myelography is necessary or not.

METHODS

Fifty-four patients fulfilled the criteria. All patients underwent MRI, myelography, and CTM. MRI was performed with the patient in a normal recumbent position, and CTM was performed with the patients in both a recumbent and extended positions. All patients underwent surgery for lumbar spinal stenosis. Findings from visual examinations (sagittal images of MR, axial images of MR, axial reconstruction images of CTM and myelograms) were defined as compression + or -. We analyzed the sensitivity of the different examinations for diagnosis and the relationship among the types of images.

RESULTS

Sensitivity was as follows: CTM 94.4 %, myelography 87.0 %, and MRI 75.9 %. In myelography, the images of 37 patients were worsened by dynamic synthesis (Dyn+). Among patients without compression on MRI, 11 showed compression on myelography. Of these 11, 8 of these patients were Dyn+, and 2 patients showed compression on myelography, but not on CTM and were Dyn+. Thus, some compression can be revealed only with myelography. CTM was more sensitive than axial MRI and showed compression in 12 patients that was not detected by axial MRI.

CONCLUSION

Myelography revealed stenosis that was not detected by MRI. CTM with extension is more sensitive for detecting stenosis than MRI. Recumbent MRI cannot replace myelography or CTM in terms of dynamic findings and sensitivity.

Hypertrophy of the ligamentum flavum in lumbar spinal canal stenosis is associated with increased bFGF expression

PURPOSE

A prospective study was undertaken to investigate basic fibroblast growth factor (bFGF) expression in hypertrophic ligamentum flavum (LF) from patients with lumbar spinal canal stenosis (LSCS) and to determine whether there was a correlation of bFGF expression with LF thickness.

METHODS

Twenty patients with lumbar spinal canal stenosis were enrolled in this study. bFGF mRNA and protein expressions in LF were analyzed using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA), respectively. The thickness of LF was measured by axial T1-weighted magnetic resonance imaging.

RESULTS

Expression of bFGF was substantially higher in the hypertrophic LF group than in the control group (P < 0.001) as quantified by quantitative real-time PCR. In immunohistochemical study, bFGF was positively stained on the fibroblasts within hypertrophic LF compared to nonpathologic LF of controls. Subsequent ELISA analysis revealed that bFGF concentration in the hypertrophic LF group was remarkably higher than that in the control group (P = 0.003). The thickness of LF in the hypertrophic LF was significantly greater than that in the control group (P < 0.001). LSCS patients with greater severity of LF hypertrophy had significantly higher bFGF levels in the LF tissues (P < 0.001). Furthermore, the bFGF concentration exhibited a positive correlation with the LF thickness (r = 0.974, P < 0.001).

CONCLUSIONS

These findings suggest that the increased expression of bFGF is associated with the hypertrophy of ligamentum flavum in patients with LSCS.

Minimally invasive lumbar decompression for the treatment of spinal stenosis of the lumbar spine

SUMMARY Lumbar spinal stenosis is one of the most common degenerative diseases of the elderly population, and a major cause of debilitating pain and decreased function. Lumbar spinal stenosis is almost always associated with neurogenic claudication characterized as pain worsened by standing or walking and relieved by lumbar flexion or sitting. While initial treatment of lumbar spinal stenosis may involve conservative therapies, as patients become more symptomatic the traditional treatment path has generally led to open laminectomy and other invasive, potentially destabilizing, procedures. More recently, less invasive alternatives to wide laminectomy have been developed. This article describes a new method of percutaneous lumbar decompression for treatment of neurogenic claudication secondary to lumbar spinal stenosis, the minimally invasive lumbar decompression procedure. We review the steps of successfully decompressing the hypertrophic ligamentum flavum and lamina, thereby alleviating pressure on neural structures. This is a major innovation in patient care and a step to reduce risks while minimizing costs.

Imaging of spinal stenosis: neurogenic intermittent claudication and cervical spondylotic myelopathy

Spinal stenosis in either the cervical or lumbar spinal segments is one of the most common indications for spine imaging and intervention, particularly among the elderly. This article examines the pathophysiology and imaging of the corresponding clinical syndromes, cervical spondylotic myelopathy or neurogenic intermittent claudication. The specificity fault of spine imaging is readily evident in evaluation of spinal stenosis, as many patients with anatomic cervical or lumbar central canal narrowing are asymptomatic. Imaging also may be insensitive to dynamic lesions. Those imaging features that identify symptomatic patients, or predict response to interventions, are emphasized.

Dynamic changes in the dural sac cross-sectional area on axial loaded MR imaging: is there a difference between degenerative spondylolisthesis and spinal stenosis?

BACKGROUND AND PURPOSE

Axial loaded MR imaging, which can simulate the spinal canal of patients in a standing position, demonstrates a significant reduction of the DCSA compared with conventional MR imaging and provides valuable imaging findings in the assessment of the lumbar spinal canal. The purpose of this study was to compare the DCSA on axial loaded MR imaging between patients with DS and SpS.

MATERIALS AND METHODS

Eighty-eight consecutive patients were divided into DS and SpS groups. DCSA on conventional MR imaging and axial loaded MR imaging and changes in the DCSA induced by axial loading were compared between DS and SpS groups. The prevalence of a significant change (>15 mm(2)) in the DCSA was compared between the 2 groups.

RESULTS

Axial loaded MR imaging demonstrated significantly smaller DCSA in the DS group (35 ± 22 mm(2)) than in the SpS group (50 ± 31 mm(2)), though conventional MR imaging did not show any differences between the 2 groups. The change in the DCSA induced by axial loading was significantly larger in the DS group (17 ± 12 mm(2)) compared with the SpS group (8 ± 8 mm(2)). The prevalence of a >15-mm(2) change in the DCSA was significantly higher in the DS group (62.5%) than in the SpS group (16.7%) (odds ratio, 8.33; 95% confidence interval, 3.09-22.50).

CONCLUSIONS

Axial loaded MR imaging demonstrated significantly larger changes in the DCSA in patients with DS compared those with SpS. A significant change in the DCSA was more frequently observed in patients with DS. Axial loaded MR imaging may therefore be a more useful tool to decrease the risk of underestimating the spinal canal narrowing in patients with DS than in those with SpS.

Dynamic change of dural sac cross-sectional area in axial loaded magnetic resonance imaging correlates with the severity of clinical symptoms in patients with lumbar spinal canal stenosis

STUDY DESIGN

Cross-sectional registry and imaging cohort study. OBJECTIVE.: To examine whether the dural sac cross-sectional area (DCSA) in axial loaded magnetic resonance imaging (MRI) correlates with the severity of clinical symptoms in patients with lumbar spinal canal stenosis (LSCS).

SUMMARY OF BACKGROUND DATA

Many studies have analyzed the relationship between DCSA on conventional MRI and the severity of symptoms in LSCS, but the link is still uncertain. Recently, axial loaded MRI, which can stimulate the spinal canal of patients in the upright position, has been developed. Axial loaded MRI demonstrates significant reduction of DCSA and provides valuable radiologic findings in the assessment of LSCS. However, there has been no study of the correlation between DCSA in axial loaded MRI and the severity of symptoms in LSCS.

METHODS

In 88 patients with LSCS, DCSA in conventional MRI, axial loaded MRI, and changes in the DCSA were determined at the single most constricted intervertebral level. The severity of symptoms was evaluated on the basis of the duration of symptoms, walking distance, visual analogue scale of leg pain/numbness, and Japanese Orthopaedic Association score. Spearman correlations of the DCSA in conventional MRI, axial loaded MRI, and changes in the DCSA with the severity of symptoms were analyzed. In addition, the severity of symptoms and DCSA in conventional and axial loaded MRI were compared, respectively, between patients with and without significant (>15 mm) changes in the DCSA.

RESULTS

The DCSA in axial loaded MRI had good correlations with walking distance and Japanese Orthopaedic Association score (rs = 0.46 and 0.45, respectively; P < 0.001). In addition, the change in the DCSA significantly correlated to walking distance, visual analogue scale of leg numbness, and Japanese Orthopaedic Association score (rs = 0.59, 0.44, and 0.54, respectively; P < 0.001). Furthermore, the symptoms were significantly worse in patients with more than 15 mm change in the DCSA (P < 0.001). Axial loaded MRI, but not conventional MRI, showed a significantly smaller DCSA in patients with more than 15 mm change in the DCSA (P < 0.05).

CONCLUSION

DCSA in axial loaded MRI significantly correlated with the severity of symptoms. Axial loaded MRI demonstrated that changes in the DCSA significantly correlated with the severity of symptoms, which conventional MRI could not detect. Thus, MRI with axial loading provides more valuable information than the conventional MRI for assessing patients with LSCS.

Pedicle-screw-based dynamic implants may increase posterior intervertebral disc bulging during flexion

Abstract Posterior disc bulging may lead to nerve root compression and radicular pain, and in extreme cases to a local pressure on the dural sac and thus to back pain. Compared to when standing, posterior disc bulging is increased during extension and decreased during flexion, in an uninstrumented spine. The aim of this study was to determine the effect of a pedicle-screw-based dynamic implant on posterior disc bulging. A finite element model of the lumbosacral spine was used to calculate posterior disc bulging before and after implantation of a dynamic implant for different loading cases. The elastic modulus of the longitudinal rod was varied, and the influence of distraction of the bridged segment on disc bulging was also determined. In addition, the centre of rotation (CoR) was determined. Due to a dynamic implant, the magnitude of posterior disc bulging was reduced compared to that for "standing without an implant" during extension, lateral bending, and axial rotation. During flexion, however, disc bulging was usually increased. With increasing stiffness of the dynamic implant, the CoR moved towards the longitudinal rod. This posterior shift of the CoR led to a compression of the entire intervertebral disc during flexion and thus to an increase of disc bulging.

Matrix metalloproteinase 13 in the ligamentum flavum from lumbar spinal canal stenosis patients with and without diabetes mellitus

BACKGROUND

Lumbar spinal canal stenosis (LSCS) is one of the most common spinal disorders in the elderly, and ligamentum flavum (LF) hypertrophy is an important cause of LSCS. Matrix metalloproteinase 13 (MMP13) can degrade fibrillar collagens and elastic microfibrils, and is involved in inflammation and fibrosis. The purpose of this study was to compare the expression of MMP13 in the LF from LSCS patients with diabetes mellitus [DM (+)] with that in the LF from patients without DM [DM (-)] and to analyze the relationship among DM, MMP13 expression, and LF hypertrophy.

METHODS

LFs from 11 DM (+) and 24 DM (-) LSCS patients were analyzed in this study. Histology analysis using hematoxylin and eosin and Masson's trichrome stain was performed for each LF. The expression of MMP13 was analyzed by quantitative real-time PCR. The thickness of LF was measured by CT.

RESULTS

In the LF from DM (+) LSCS patients, the elastic fibers were more disorganized and had lower volumes than in the LF from DM (-) LSCS patients, while more fibrotic tissue was observed in the LF from DM (+) than from DM (-) LSCS patients. MMP13 expression was significantly higher in the LF from DM (+) LSCS patients (0.46 ± 0.61 vs. 0.05 ± 0.09, P = 0.002). The LF from the DM (+) LSCS patients was significantly thicker than that from the DM (-) LSCS patients (5.0 ± 0.9 vs. 3.1 ± 0.8 mm, P < 0.01), and the thickness was correlated with the expression of MMP13 (correlation coefficient = 0.43, P = 0.01, Pearson's correlation test).

CONCLUSION

DM-related MMP13 expression can be one of the factors contributing to fibrosis and hypertrophy of the LF. Further research on the mechanism of this process may lead to new therapies for LF hypertrophy.

Measurement of occlusion of the spinal canal and intervertebral foramen by intervertebral disc bulge

Background

Disc protrusion has been proposed to be a possible cause of both pain and stenosis in the lower spine. No previous study has described the amount of disc occlusion of the spinal canal and intervertebral foramen that occurs under different loading conditions. The objective of this study was to quantitatively assess the percent occlusion of the spinal canal and intervertebral foramen by disc bulge under different loading conditions.

Methods

Spinal canal depth and foraminal width were measured on computed tomography–scanned images of 7 human lumbar spine specimens. In vitro disc bulge measurements were completed by use of a previously described method in which single functional spinal units were subjected to 3 separate load protocols in a spine test machine and disc bulge was recorded with an optoelectric motion system that tracked active light-emitting diodes placed on the posterior and posterolateral aspects of the intervertebral disc. Occlusion was defined as percentage of encroachment into area of interest by maximum measured disc bulge at corresponding point of interest (the spinal canal is at the posterior point; the intervertebral foramen is at the posterolateral point).

Results

The mean spinal canal depth and mean foraminal width were 19 4 ± mm and 5 ± 2 mm, respectively. Mean spinal canal occlusion under a 250-N axial load, ± 2.5 Nm of flexion/extension, and ± 2.5 Nm of lateral bend was 2.5% ± 1.9%, 2.5% ± 1.6%, and 1.5% ± 0.8%, respectively. Mean intervertebral foramen occlusion under a 250-N axial load, ± 2.5 Nm of flexion/extension, and ± 2.5 Nm of lateral bend was 7.8% ± 4.7%, 9.5% ± 5.7%, and 11.3% ± 6.2%, respectively.

Conclusion

Percent occlusion of the spinal canal and intervertebral foramen is dependent on magnitude and direction of load. Exiting neural elements at the location of the intervertebral foramen are the most vulnerable to impingement and generation of pain.

Ligamentum flavum thickness in normal and stenotic lumbar spines

STUDY DESIGN

A descriptive computed tomography (CT) study of the ligamentum flavum (LF) thickness in individuals with normal and stenotic lumbar spines.

OBJECTIVE

To establish standards for normal and pathologic range of LF thickness and its asymmetry as indicated in CT images and to examine its association with vertebral body size, age, and gender.

SUMMARY OF BACKGROUND DATA

LF lines a considerable part of the posterior and lateral walls of the spinal canal and is a major role contributor to spinal canal stenosis. Due to methodologic deficiencies (e.g., small sample size, lack of control for vertebral body size, gender, and age), the normal range of LF thickness is still controversial. Furthermore, data on important aspect of LF thickness such as left-right differences are missing.

METHODS

Two groups of individuals were studied. The first group included 65 individuals with lumbar spinal stenosis (LSS) (mean age: 66 +/- 9.7 years) and the second, 150 individuals (mean age: 52 +/- 19 years) without LSS-related symptoms. LF thickness was measured on CT images (Philips Brilliance 64), obtained from axial plane scan at the intervertebral disc level. Measurements were performed at the levels of L3-L4, L4-L5, and L5-S1. Analysis of variance and t test were carried out to evaluate the association between LF thickness and demographic factors.

RESULTS

Absolute and relative LF thickness were significantly greater in the LSS group at the levels of L3-L4 and L4-L5 on both sides, compared to control group (P < 0.05). LF thickness was independent of gender (absolute and relative thickness). Even though LF thickness at all levels significantly increases with age, significant changes after the age of 60 occurred only at L3-L4. Significant asymmetry in LF thickness was found at L3-L4 (2.9 +/- 0.90 mm on the right vs. 2.76 +/- 0.90 mm on the left) and L5-S1 (3.42 +/- 1.1 mm on the right vs. 3.22 +/- 1.22 mm on the left) (P < 0.05).

CONCLUSION

LF thickness is an age-dependent and gender-independent phenomenon. LF is significantly thicker on the right side. The borderline between normal and pathologic LF thickness should not be set at 4 mm.