Effect of axial loading on neural foramina and nerve roots in the lumbar spine

MR imaging differentiating features between lytic and degenerative lumbosacral spondylolisthesis

Spondylolisthesis is characterized by the displacement of one vertebral body in relation to the adjacent vertebra. It is commonly observed in the lower lumbar region and can be caused by a variety of factors, including spondylolysis (a fracture in the pars interarticularis) or degenerative disease. Magnetic resonance imaging (MRI) is becoming increasingly popular as the primary modality for evaluation of low back pain and is often used in the absence of radiographs or Computed Tomography. However, it can be challenging for radiologists to differentiate between the two types of spondylolisthesis based on MRI alone. The goal of this article is to identify key imaging features on MRI that can aid radiologists in differentiating between spondylolysis and degenerative spondylolisthesis on MRI. Five key concepts are discussed: the "step-off" sign, the "wide canal" sign, T2 cortical bone signal on MRI, epidural fat interposition, and fluid in the facet joints. The utility, limitations and potential pitfalls of these concepts are also discussed to provide a comprehensive understanding of their use in differentiating between the two types of spondylolisthesis on MRI.

Mechanism Underlying Painful Radiculopathy in Patients with Lumbar Disc Herniation

BACKGROUND

Painful lumbar radiculopathy is a neuropathic pain condition, commonly attributed to nerve root inflammation/compression by disc herniation. The present exploratory study searched for associations between pain intensity and inflammatory markers, herniated disc size, infection, psychological factors and pain modulation in patients with confirmed painful lumbar radiculopathy scheduled for spine surgery.

METHODS

Prior to surgery, 53 patients underwent the following evaluation: pain intensity measured on a 0-10 numeric rating scale (NRS) and the Short-Form McGill Pain Questionnaire; sensory testing (modified DFNS protocol); pain processing including temporal summation and conditioned pain modulation (CPM); neurological examination; psychological assessment including Spielberger's Anxiety Inventory, Pain Sensitivity Questionnaire and the Pain Catastrophizing Scale. Pro-inflammatory cytokine levels (IL-1b, IL-6, IL-8, IL-17, TNFα, IFNg) and microbial infection (ELISA and rt-PCR) in blood and disc samples obtained during surgery. MRI scans assessments for disc herniation size/volume (MSU classification/ three-dimensional volumetric analysis).

RESULTS

Complete data was available from 40 (75%) patients (15 female) aged 44.8±16.3 years. Pain intensity (NRS) positively correlated with pain catastrophizing and CPM (r=0.437, P=0.006; r=0.421, P=0.007; respectively), but not with disc/blood cytokine levels, bacterial infection or MRI measures. CPM (P=0.001) and gender (P=0.029) were associated with average pain intensity (adjusted R2=0.443).

CONCLUSIONS

This exploratory study suggests that pain catastrophizing, CPM and gender, seem to contribute to pain intensity in patients with painful lumbar radiculopathy. The role of mechanical compression and inflammation in determining the intensity of painful radiculopathy remains obscure.

Use of machine learning to select texture features in investigating the effects of axial loading on T2-maps from magnetic resonance imaging of the lumbar discs

BACKGROUND

Recent advances in texture analysis and machine learning offer new opportunities to improve the application of imaging to intervertebral disc biomechanics. This study employed texture analysis and machine learning on MRIs to investigate the lumbar disc's response to loading.

METHODS

Thirty-five volunteers (30 (SD 11) yrs.) with and without chronic back pain spent 20 min lying in a relaxed unloaded supine position, followed by 20 min loaded in compression, and then 20 min with traction applied. T₂-weighted MR images were acquired during the last 5 min of each loading condition. Custom image analysis software was used to segment discs from adjacent tissues semi-automatically and segment each disc into the nucleus, anterior and posterior annulus automatically. A grey-level, co-occurrence matrix with one to four pixels offset in four directions (0°, 45°, 90° and 135°) was then constructed (320 feature/tissue). The Random Forest Algorithm was used to select the most promising classifiers. Linear mixed-effect models and Cohen's d compared loading conditions.

FINDINGS

All statistically significant differences (p < 0.001) were observed in the nucleus and posterior annulus in the 135° offset direction at the L4-5 level between lumbar compression and traction. Correlation (P_2-Offset, P_4-Offset) and information measure of correlation 1 (P_3-Offset, P_4-Offset) detected significant changes in the nucleus. Statistically significant changes were also observed for homogeneity (P_2-Offset, P_3-Offset), contrast (P_2-Offset), and difference variance (P_4-Offset) of the posterior annulus.

INTERPRETATION

MRI textural features may have the potential of identifying the disc's response to loading, particularly in the nucleus and posterior annulus, which appear most sensitive to loading.

LEVEL OF EVIDENCE

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

The effects of axial loading on the morphometric and T2 characteristics of lumbar discs in relation to disc degeneration

BACKGROUND

Intervertebral disc degeneration affects the morphology, biomechanics and biochemistry of the disc. The study aimed to compare the effects of compression and traction on lumbar discs measurements in relation to degeneration.

METHODS

Thirty-five volunteers (30 (SD 11) yrs.) with and without chronic back pain rested supine 15 min before an unloaded T₂-mapping MRI, were then loaded 20 min with 50% body weight with imaging during the last 5 min, and then repeated this process under traction. For lumbar discs, height, angle, width, mean-T₂, and T₂-weighted centroid locations were calculated. A repeated measure ANCOVA and Cohen's d compared loading conditions. Relations between measurement changes between conditions and degeneration assessed by Pfirrmann ratings were examined graphically.

FINDINGS

From compression to traction, we observed significant: decrease in L1-2 mean-T₂ (Effect size = -0.35); inferior and posterior shift in L4-5 (0.4, 0.14) and L5-S1 (0.25, 0.33) T₂-weighted centroid. From unloaded to compression, we observed a significant: increase in L5-S1 width (Effect Size = 0.22); anterior shift in L1-2 T₂-weighted centroid (0.39); and L3-4 (mean 2.1°) and L4-5 (1.8°) extension angle. More degeneration was graphically related with larger changes from Compression to Traction (more superior and, anterior position of the T₂-weighted centroid, increased height, reduced extension of segmental angle) and from Unloaded to Compression larger changes in inferior displacement of the T_2-weighted centroid, decrease in height) but less anterior displacement of the centroid and less change in segmental angles.

INTERPRETATION

The largest loading responses were at lower levels, generally with more degeneration. T₂-weighted centroid locations, angle and disc height detected the largest loading response.

Human Thoracolumbar Spine Tolerance to Injury and Mechanisms From Caudo-Cephalad Loading: A Parametric Modeling Study

The aims of this investigation were to delineate the internal biomechanics of the spine under vertical impact vector and assess the probability of injury. Male and female whole-body human finite element models were used. The restrained occupants were positioned on the seat, and caudo-cephalad impacts were applied to the base. Different acceleration-time profiles (50-200 ms pulse durations, 11-46 g peak accelerations) were used as inputs in both models. The resulting stress-strain profiles in the cortical and cancellous bones were evaluated at different vertebral levels. Using the peak transmitted forces at the thoracolumbar disc level as the response variable, the probability of injury for the male spine was obtained from experimental risk curves for the various pulses. Results showed that the shorter pulse durations and rise times impart greater loading on the thoracolumbar spine. The analysis of von Mises stress and strain distributions showed that the compression-related fractures are multifaceted with contributions from both the cortical and cancellous bony components of the body. Profiles are provided in the paper. The intervertebral disc may be involved in the fracture mechanism, because it acts as a medium of load transfer between adjacent vertebrae. Injury risks for the shortest pulse was 63%, and for the widest pulse it was close to zero, and injury probabilities for other pulses are given. The present modeling study provides insights into the mechanisms of internal load transfer and describes injury risk levels from caudal to cephalad impacts.

Prevalence and Risk Factors of Peripheral Arterial Disease in Patients with Lumbar Spinal Stenosis and Intermittent Claudication: CT Angiography Study

BACKGROUND

It can be difficult to differentiate between vascular and neurogenic intermittent claudication. The exact diagnosis often cannot be made on clinical evidence and ultimately requires imaging. Perioperative screening for peripheral arterial disease (PAD) in lumbar spinal stenosis (LSS) patients is important because untreated PAD increases the risk of severe vascular events. The aims of this study were to study the prevalence of PAD in LSS patients with symptoms of intermittent claudication, and to study the independent risk factors for PAD. We specified the cases where it was necessary to perform computed tomography angiography (CTA) as a preoperative screening tool in surgery for spinal stenosis.

METHODS

This study involved a retrospective analysis of 186 consecutive subjects with radiographic evidence of LSS and symptoms of intermittent claudication, who underwent 3D CTA of the lower extremities at our institution during a three-year period. More than 50% luminal narrowing on CT angiograms was determined to be clinically significant and placed in the PAD group.

RESULTS

Thirty-two subjects were diagnosed with PAD and referred to the general vascular team in our hospital, where they received treatment for PAD. In the non-PAD group (154 subjects), 117 underwent definitive surgery for spinal stenosis such as posterior lumbar interbody fusion and a further 37 underwent conservative treatment. Only hypertension, diabetes, and men gender were found to be statistically significant predictors of PAD.

CONCLUSION

The current study showed that man gender, diabetes and hypertension were the greatest risk factors for PAD. We conclude that man patients with diabetes and/or hypertension should be put under serious consideration for routine CTA examination when under evaluation for LSS and intermittent claudication.

Diagnostic Importance of Axial Loaded Magnetic Resonance Imaging in Patients with Suspected Lumbar Spinal Canal Stenosis

OBJECTIVE AND BACKGROUND

To study the efficacy of lumbar (AL) magnetic resonance imaging (MRI) in patients with suspected lumbar spinal stenosis (LSS), with and without AL compression. Supine MRI is used in the assessment of patients with LSS. However, MRI findings may poorly correlate with neurologic findings because of the morphologic changes of the lumbar spinal canal between upright standing and supine positions. In patients without significant stenosis in routine lumbar MRI, by applying AL, MRI can show significant LSS.

METHODS

This study included 103 consecutive patients (188 disc levels) who presented with neurogenic claudication with and without low back pain. AL was performed using a nonmagnetic compression device for 5 minutes. T1- and T2-weighted axial and sagittal sequences were obtained during AL applied to the spine. The dural sac cross-sectional area (DSCA) appeared to be narrow at each disc level of L4-5 to L5-S1 in all patients and was measured using T2-weighted images in routine supine and AL images.

RESULTS

The groups included patients with a reduction in the DSCA (>15 mm²) according to patient age and DSCA in routine spine MRI. The mean DSCA of the disc levels without and with AL were 138 mm² and 123 mm², with a mean difference of 15 mm² at L4-5, 134 mm² and 125 mm² and a mean difference of 9 mm² at L5-S1, respectively.

CONCLUSIONS

The use of AL MRI in patients with clinically suspected LSS could reduce the risk of misdiagnosis of stenosis, leading to inappropriate treatment.

Correlation of lumbar lateral recess stenosis in magnetic resonance imaging and clinical symptoms

AIM

To assess the correlation of lateral recess stenosis (LRS) of lumbar segments L4/5 and L5/S1 and the Oswestry Disability Index (ODI).

METHODS

Nine hundred and twenty-seven patients with history of low back pain were included in this uncontrolled study. On magnetic resonance images (MRI) the lateral recesses (LR) at lumbar levels L4/5 and L5/S1 were evaluated and each nerve root was classified into a 4-point grading scale (Grade 0-3) as normal, not deviated, deviated or compressed. Patient symptoms and disability were assessed using ODI. The Spearman’s rank correlation coefficient was used for statistical analysis (P < 0.05).

RESULTS

Approximately half of the LR revealed stenosis (grade 1-3; 52% at level L4/5 and 42% at level L5/S1) with 2.2% and 1.9% respectively reveal a nerve root compression. The ODI score ranged from 0%-91.11% with an arithmetic mean of 34.06% ± 16.89%. We observed a very weak statistically significant positive correlation between ODI and LRS at lumbar levels L4/5 and L5/S1, each bilaterally (L4/5 left: rho < 0.105, P < 0.01; L4/5 right: rho < 0.111, P < 0.01; L5/S1 left: rho 0.128, P < 0.01; L5/S1 right: rho < 0.157, P < 0.001).

CONCLUSION

Although MRI is the standard imaging tool for diagnosing lumbar spinal stenosis, this study showed only a weak correlation of LRS on MRI and clinical findings. This can be attributed to a number of reasons outlined in this study, underlining that imaging findings alone are not sufficient to establish a reliable diagnosis for patients with LRS.

La TC con carico assiale nella instabilità del rachide lombo-sacrale

La diagnosi di instabilità del rachide lombo-sacrale è, a tutt'oggi, fondamentalmente clinica.

Anche le più sofisticate tecniche di diagnostica radiologica consentono infatti solo una valutazione statica di questa entità nosologica (che, per definizione si manifesta durante la deambulazione e con la stazione eretta) la cui definizione dinamica è campo pressochè esclusivo della radiologia convenzionale. Presentiamo i risultati di uno studio condotto attraverso l'uso di uno strumento originale progettato per sviluppare un carico assiale variabile e riproducibile in un paziente supino: il Compressore assiale. Con questo strumento, compatibile con l'esecuzione di esami TC, sono stati valutati 24 pazienti con forte sospetto clinico-radiologico di instabilità lombare.

La metodica di studio, denominata Axial Loaded - Computed Tomography (AL-CT) si basa sull'acquisizione successiva di esami TC basali e con carico assiale (AL), che vengono poi comparati. Il confronto avviene sia sulle scansioni assiali che su immagini ricostruite su piani sagittali e con «rendering» tridimensionale (3D-TC). La valutazione comparativa prevede sia l'uso di immagini statiche che l'organizzazione in sequenze cine (cine AL-CT) delle immagini 2D e 3D ottenute. Tutti i procedimenti di rielaborazione sono indispensabili nella valutazione dei risultati.

I risultati mostrano con chiarezza reperti (numerosi e spesso simultanei) a carico di tutte le component le unità funzionali spinali; fra questi meritano una segnalazione: l'incremento o la accentuazione di protrusioni discali sotto carico; la scomparsa del vacuum discale e/o intraarticolare durante la compressione («segno del vacuum»); l'accentuazione della listesi sotto carico; la ottimale ed originale visualizzazione dell' ipermobilità delle faccette articolari.

Proponiamo AL-CT e cine AL-CT come metodiche di scelta nello studio dell'instabilità lombare.

Functional Evaluation of the Lumbar Spine with Axial Loaded Computed Tomography (AL-CT) and Cine AL-CT

This study reports a personal experience in the functional study of the lumbar spine with original diagnostic techniques called Axial Loaded Computed Tomography (AL-CT) and Cine AL-CT, based on the use of the Axial Loader, a device that develops a variable and reproducible axial load in a supine patient during computed tomography or magnetic resonance investigation3,4.

We built a non ferromagnetic, X-ray transparent bed (the Axial Loader), with double blocking rests for shoulders and feet, that can be used during CT and MR spine studies. The inferior block is a platform that moves continuously in a longitudinal direction, with a micrometric mechanism. A dynamometer placed between the inferior platform and the patient's feet can measure the load applied.

We studied 75 patients, with a clinical and diagnostic suspicion of lumbar spine instability. The examinations were performed on a conventional CT unit (GE Sytec 3000, General Electric, Milwaukee) with a “volumetric” approach to the lumbar spine.

In conclusion, AL-CT and Cine AL-CT is currently the only diagnostic modality that can give dynamic information on the differents UFSs in all their components in one mildy invasive, easily reproducible diagnostic examination.

Factors affecting dynamic foraminal stenosis in the lumbar spine

BACKGROUND CONTEXT

Lumbar foraminal stenosis is a common clinical problem and a significant cause of lower extremity radiculopathy. Minimal in vivo data exists quantifying changes in foraminal area (FA) as the spine moves from flexion to extension in the lumbar spine or on the relationship between FA and lumbar segmental angular motion, translational motion (TM), or disc bulge migration.

PURPOSE

To use kinetic magnetic resonance imaging (kMRI) to evaluate changes in dimensions of lumbar neural foramina during weight bearing in neutral, flexion, and extension positions. To evaluate the relationship between foraminal stenosis and lumbar segmental angular motion, TM, and disc bulge migration.

STUDY DESIGN

A retrospective radiographic study.

PATIENT SAMPLE

Forty-five patients with a mean age of 44 years undergoing kMRI for symptoms of low back pain or radiculopathy.

OUTCOME MEASURES

Magnetic resonance imaging measurements of FA, angular motion, TM, and disc bulge migration.

METHODS

Kinetic magnetic resonance imaging of the lumbar spine was reviewed in 45 patients with low back pain or radiculopathy, and parasagittal images were evaluated for changes in neural foraminal dimensions in various degrees of motion with weight bearing. The changes in foraminal dimension were correlated to the amount of segmental angular motion, TM, and disc bulge migration at each level. Neural foramina were also assessed qualitatively by Wildermuth criteria. Only those foramina that were clearly visualized with well-defined anatomic boundaries in all three positions were taken into consideration. Patients with previous surgery, tumor, and scoliosis were excluded from the study.

RESULTS

There was a significant decrease in the FA from flexion to neutral (p<.05) at all levels except L5-S1 and from neutral to extension at all levels (p<.05). The average percent decrease in FA was 30.0% with the greatest decrease from flexion to extension occurring at L2-L3 (167-107 mm(2)) and the smallest change occurring at L5-S1 (135-106 mm(2)) (p<.05). The magnitude of change in FA increased as angular motion at a segment increased. The mean change in FA was 32.3 mm(2) when angular motion was less than 5° and was 75.16 mm(2) when angular motion exceeded 15°. The extent of disc bulging posteriorly in the neural foramen was also correlated with the reduction in the FA from flexion to extension, but TM had no effect.

CONCLUSIONS

Foraminal area decreased significantly in extension compared with flexion and neutral on MRI. Lumbar disc bulge migration and angular motion at each level contributed independently to the decrease in FA in extension, whereas TM had no effect on FA.

Axial loading during magnetic resonance imaging in patients with lumbar spinal canal stenosis: does it reproduce the positional change of the dural sac detected by upright myelography?

STUDY DESIGN

We compared the sizes of the dural sac among conventional magnetic resonance imaging (MRI), axial loaded MRI, and upright myelography in patients with lumbar spinal canal stenosis (LSCS).

OBJECTIVE

To determine whether axial loaded MRI can demonstrate similar positional changes of the dural sac size as were detected by upright myelography in LSCS.

SUMMARY OF BACKGROUND DATA

In patients with LSCS, constriction of the dural sac is worsened and symptoms are aggravated during standing or walking. To disclose such positional changes, upright myelography has been widely used. Recently, axial loaded MRI, which can simulate a standing position, has been developed. However, there has been no study to compare the dural sac size between axial loaded MRI and upright myelography.

METHODS

Forty-four patients underwent conventional MRI, axial loaded MRI, and myelography. Transverse and anteroposterior diameters and the cross-sectional areas of the dural sac from L2-L3 to L5-S1 were compared. Pearson correlations of the diameters between the MRIs and the myelograms were analyzed. On the basis of the myelograms, all disc levels were divided into severe and nonsevere constriction groups. In each group, the diameters and the cross-sectional areas were compared. Sensitivity and specificity to detect severe constriction were calculated for the conventional and axial loaded MRI.

RESULTS

Transverse and anteroposterior diameters at L4-L5 in the axial loaded MRI and myelogram were significantly smaller than those observed in the conventional MRI (P < 0.001). Cross-sectional areas in the axial loaded MRI were significantly smaller than those in the conventional MRI at L2-L3, L3-L4, and L4-L5 (P < 0.001). Between the axial loaded MRI and the myelography, Pearson correlation coefficients of the transverse and anteroposterior diameters were 0.85 and 0.87, respectively (P < 0.001), which were higher than those for conventional MRI. Reductions of the dural sac sizes in the axial loaded MRI were more evident in the severe constriction group. The axial loaded MRI detected severe constriction with a higher sensitivity (96.4%) and specificity (98.2%) than the conventional MRI.

CONCLUSION

The axial loaded MRI demonstrated a significant reduction in the dural sac size and significant correlations of the dural sac diameters with the upright myelogram. Furthermore, the axial loaded MRI had higher sensitivity and specificity than the conventional MRI for detecting the severe constriction observed in the myelogram. Therefore, the axial loaded MRI can be used to represent positional changes of the dural sac size detected by the upright myelography in patients with LSCS.

The validity of ankle-brachial index for the differential diagnosis of peripheral arterial disease and lumbar spinal stenosis in patients with atypical claudication

PURPOSE

Claudication is a typical symptom of peripheral arterial disease (PAD) and lumbar spinal stenosis (LSS). Differential diagnosis of PAD and LSS is often difficult due to the subjective natures of symptoms and atypical signs. The authors aimed to determine the usefulness of ankle-brachial index (ABI) measurement for the differential diagnosis of PAD and LSS when the etiology of claudication is uncertain.

METHODS

Forty-two consecutive patients who had been referred by spine surgeons to a lower extremity vascular surgeon for atypical claudication were retrospectively analyzed. Atypical claudication was defined as claudication not caused by PAD, as determined by clinical manifestations, or by LSS, as determined by MR imaging. A final diagnosis of PAD was established by CT angiography (CTA) and of LSS by excluding PAD. Diagnostic validity of ABI for PAD in atypical presentation was assessed.

RESULTS

Sixty-two legs of 42 atypical claudication patients were analyzed. Mean patient age was 65.8 ± 8.2 years (38-85) and 29 (69.0%) had diabetes mellitus. Mean ABI was 0.73 ± 0.14 (0.53-0.94) in the PAD group and 0.92 ± 0.18 (0.52-1.10) in the LSS group (P < 0.001). Of the 33 legs with a low ABI (ABI < 0.9), 29 legs were diagnosed as true positives for PAD by CTA and 4 were false positives, and of the 29 legs with a high ABI, 5 were false negatives and 24 were true negatives. The sensitivity and specificity of ABI for the diagnosis of PAD in patients with atypical claudication were 85.3 and 85.7%, respectively, and its positive and negative predictive values were 87.9 and 82.8%.

CONCLUSIONS

ABI is a recommended screening test for the differential diagnosis of lower leg claudication when clinical symptoms are atypical.

Biomechanics of intervertebral disk degeneration

Degenerative changes in the material properties of nucleus pulposus and anulus fibrosus promote changes in viscoelastic properties of the whole disc. Volume, pressure and hydration loss in the nucleus pulposus, disk height decreases and fissures in the anulus fibrosus, are some of the signs of the degenerative cascade that advances with age and affect, among others, spinal function and its stability. Much remains to be learned about how these changes affect the function of the motion segment and relate to symptoms such as low back pain and altered spinal biomechanics.

The "Dehydrated" Lumbar Intervertebral Disk on MR, its Anatomy, Biochemistry and Biomechanics

MR imaging of the lumbar spine often is requested to identify the cause of back or radicular pain. Official reports of lumbar spine images tend to focus on changes in the disk margin that may cause nerve root compression. The potential role of the dark disk, in back pain has not been adequately emphasized. The purpose of this review is to discuss the dark disk that has not produced nerve root compression. On T2-weighted images, a disk that has diminished signal intensity is called a dark disk or a dehydrated disk. It corresponds to a stage III disk in the Pfirrmann or the Thompson scale. Such a disk has specific morphologic, chemical and biomechanical properties, which will be reviewed in this presentation. The goal is to suggest the clinical significance of finding a dark disk on an MR image.

Experience with coflex interspinous implant

A first generation of Coflex implant for non-rigid stabilization of lumbar spine was presented by Samani (Study of a semi-rigid interspinous U fixation system. Spinal Surgery, Child Orthopaedics: 1707, 2000).We started to treat patients with this Coflex device in 2004 and since then more than 600 patients have been operated in our Neurosurgical Department. We are reporting 156 patients treated between December 2004 and 2006 with complete follow-up. The clinical trials of this and other implants provide evidence that this interspinous non-rigid stabilization is useful against low-back pain due to degenerative instability and without serious complications.

Changes in the lumbar spine of athletes from supine to the true-standing position in magnetic resonance imaging

STUDY DESIGN

Case-control observational study.

OBJECTIVE

Determination of dimensional changes in the lumbar spines of athletes between supine and stand-up position in MRI, concerning the lordosis, spinal canal cross-sectional area (SCCA), dural sac cross-sectional area (DSCA), sagittal dural sac diameter (SDSD), the lateral recess and the neural foramina.

SUMMARY OF BACKGROUND DATA

The development of positional MRI allows the examination of spine segments under a true weight-bearing situation.

METHODS

About 35 athletes (20m/15f, Ø: 28a) were examined using a 0.25 T open MRI-Scanner (G-Scan, ESAOTE, Italy). In all cases, axial and sagittal SE-T1 + SSE-T2 images were recorded in supine and true standing position. All measurements were performed using MEDIMAGE software (Vepro AG, Germany). The blinded measurements were performed 3 times by 2 independent examiners. Sagittal images were used to determine the lordosis and the narrowing of the left/right foramen at all levels between L1/2 and L5/S1. Axial images were used to determine the SDSD, the SCCA and the DSCA at L3/4, L4/5, L5/S1, and narrowing of the left/right recessus lateralis of L4, L5 and S1.

RESULTS

The lordosis showed a significant increase of 6.3 degrees (14%) from supine to true standing position (P < 0.001). The SDSD is significantly smaller in true standing position, than in supine position at the level of L3/4 and L4/5 (P < 0.001). Narrowing of the foramen occurred in true standing position in 13.4% at L4/L5 and in 26.7% at level L5/S1. No significant differences were observed at the recessus lateralis, the SCCA and the DSCA.

CONCLUSION

The measurement method in supine and true standing position is excellent for depicting the anatomical regions relevant for spinal canal stenosis in healthy individuals. Measuring the lumbar lordosis angle in both positions is an important requirement for interpreting the relevant anatomical regions. Of particular importance here is the DSCA and the SDSD.

Adjacent double-nerve root contributions in unilateral lumbar radiculopathy

BACKGROUND AND PURPOSE

Image-guided selective nerve root block/steroid injection is commonly performed for lumbar radiculopathy. The purpose of this study was to evaluate the clinical/imaging characteristics and injection response of adjacent double-root contributions to unilateral lumbar radiculopathy in a typical interventional spine practice.

MATERIALS AND METHODS

In 132 of 350 patients (37.7%) with unilateral radiculopathy, adjacent double-nerve root block/steroid injection was performed on the basis of preprocedural clinical/imaging characteristics. Clinical presentation (pain pattern, VAS), response to injection, and imaging features of potential root compression/irritation (disk protrusion, subarticular/foraminal stenosis) were tabulated.

RESULTS

Clinically, a subset of patients with both L4+L5 and L5+S1 radiculopathy presented with proximal sciatica only in addition to those with typical L4, L5 or S1 radicular patterns. Preprocedural imaging demonstrated evidence of adjacent double-root abnormality in 56 of 79 (71%) patients without prior surgery (single-level disease, 32; 2-level disease, 24) and in all 53 patients with prior lumbar surgery (scar, 42; separate-level root abnormality, 13). Adjacent double-level replication of the patient's familiar pain was present in 82 of 132 (62%) patients, with single-root replication in 37 (28%) and no response in 13 (10%). Typical sciatica was encountered by injection at L4 (15%-33%), likely reflecting furcal nerve lumbar plexus contribution from L5. Sensations from each injected root usually replicated separate recognizable portions of the patient's radiculopathy, with marked or complete pain improvement reported in most patients.

CONCLUSIONS

Adjacent double-level contributions to lumbar radiculopathy are common, and clinical/imaging clues should be assessed to ensure optimum nerve root block/steroid injection treatment response.

The effect of body position and axial load on spinal canal morphology: an MRI study of central spinal stenosis

STUDY DESIGN

A method comparison study.

OBJECTIVE

To investigate the effect of body position and axial load of the lumbar spine on disc height, lumbar lordosis, and dural sac cross-sectional area (DCSA). SUMMARY OF BACKGROUND DATA.: The effects of flexion and extension on spinal canal diameters and DCSA are well documented. However, the effects of axial loading, achieved by upright standing or by a compression device, are still unclear.

METHODS

Patients with lumbar spinal stenosis were examined in 2 separate studies, including 16 and 20 patients, respectively. In section 1, magnetic resonance imaging (MRI) scans were performed during upright standing and supine positions with and without axial load. In section 2, MRI scans were performed exclusively in supine positions, one with flexion of the lumbar spine (psoas-relaxed position), an extended position (legs straight), and an extended position with applied axial loading. Disc height, lumbar lordosis, and DCSA were measured and the different positions were compared.

RESULTS

In section 1, the only significant difference between positions was a reduced lumbar lordosis during standing when compared with lying (P = 0.04), most probably a consequence of precautions taken to secure immobility during the vertical scans. This seemingly makes our standing posture less valuable as a standard of reference. In section 2, DCSA was reduced at all 5 lumbar levels after extension, and further reduced at 2 levels after adding compression (P < 0.05). Significant reductions of disc height were found at 3 motion segments and of DCSA at 11 segments after compression, but these changes were never seen in the same motion segment.

CONCLUSION

Horizontal MRI with the patient supine and the legs straightened was comparable to vertical MRI whether axial compression was added or not. Extensionwas the dominant cause rather than compression in reducing DCSA. Axial load was not considered to have a clinically relevant effect on spinal canal diameters.

Changes in the lumbar foramen following anterior interbody fusion with tapered or cylindrical cages

BACKGROUND CONTEXT

Anterior lumbar interbody fusion (ALIF) using both cylindrical and tapered threaded interbody cages has been shown to restore disc height, reduce segmental motion, and relieve low back pain. The effectiveness of these stand-alone cage designs in restoration and maintenance of intervertebral foraminal dimensions has received little attention.

PURPOSE

To investigate the effects of anterior implantation of cylindrical and tapered interbody cages on morphologic changes of the lumbar neuroforamen and maintenance of foraminal dimensions under dynamic loading.

STUDY DESIGN/SETTING

A biomechanical study using bovine calf spine model to compare the deformation of foraminal space after ALIF with either tapered cages or cylindrical cages.

METHODS

Sixteen fresh calf spines were randomly assigned to undergo ALIF at the L3-L4 level using either two threaded cylindrical or two tapered cages. Lumbar spines were subjected to unconstrained loading in flexion, extension, and lateral bending. Rotation of the L3-L4 segment and dynamic deformation in foraminal height were obtained through a motion analysis system, and compared between the two cage groups. Foraminal dimensions were assessed before and after tapered or cylindrical cage implantation with digitized measurement of bilateral foraminal molds.

RESULTS

Regardless of cage design, anterior implantation of cages increased neuroforaminal area by 17% (p=.0005) and increased the foraminal height by 9% (p=.0004) in the neutral unloaded position. In dynamic loading conditions, foraminal height was significantly stabilized in all loading directions by the cylindrical cages (p=.01) and on both sides during lateral bending by the tapered cages (p<.03). Foraminal stabilization provided by either cage was most prominent in the direction of lateral bending (26-37% of the intact values), while cylindrical cages also provided substantial stabilization in flexion (26% of the intact value). Significant linear relationships were found between foraminal height and residual fusion segment motion under dynamic loading conditions.

CONCLUSION

Results from this bovine model biomechanical study indicate that stand-alone anterior interbody fusion cages with either tapered or cylindrical design are effective in restoring neuroforaminal height and stabilize the spine to withstand foraminal deformation during daily loading. The degree of stabilization was influenced substantially by the loading direction, to a lesser degree by the cage type, and was strongly dependent on the segment mobility. Although bovine lumbar spine is widely accepted for comparative studies, direct clinical interpretation should be made with caution owing to the anatomical differences from human.

Positional lumbar imaging using a positional device in a horizontally open-configuration MR unit - initial experience

PURPOSE

To evaluate whether positional MR images of the lumbar spine, obtained with a horizontally open-configuration MR unit, demonstrate positional changes of the dural sac, and to assess whether there are significant differences in positional changes between healthy volunteers and patients with chronic low back pain.

MATERIALS AND METHODS

The study population consisted of 15 patients with chronic low back pain and 14 healthy volunteers. MR images were obtained using a horizontally open-configuration 0.4-T MR unit. After conventional lumbar MR examinations, images were obtained in the flexion, neutral, and extension positions, using a positioning device. The anteroposterior diameter of the dural sac at the level of each lumbar disk was measured in the three positions and quantitative data were compared.

RESULTS

Our MR protocol was tolerated by all patients. In both patients and volunteers, the mean anteroposterior diameter of the dural sac was smaller in the extension positions than in the flexion positions. In the mean rate of change (RC) in the dural sac diameter at the site of the degenerated disks, the difference between the volunteers and patients was significant (P < 0.05). There was no significant difference in the mean RC between patients and volunteers without degenerative disks.

CONCLUSION

Using a horizontally open-configuration MR unit, positional MR imaging provided position-dependent change of the dural sac. Positional changes at the site of the degenerated disks may be different in patients with and without chronic low back pain.

The MR Imaging Features and Clinical Correlates in Low Back Pain–Related Syndromes

Several distinct clinical syndromes can accompany low back pain in patients with lumbar spine abnormality. Developmental factors and any superimposed degenerative changes determine the size and configuration of the spinal canal, lateral recess, and neural foramen, and can affect the nerve roots. Somatic or referred pain may develop depending on the involved anatomic site and underlying pathology. Many times, but not always, MR imaging findings correlate with the clinical presentation. Combined analysis of the imaging and clinical findings may provide a more accurate and concise approach to the patient with low back pain.

The distended facet sign: an indicator of position-dependent spinal stenosis and degenerative spondylolisthesis

BACKGROUND CONTEXT

Symptoms of spinal stenosis are position-dependent. Stand up magnetic resonance imaging (MRI) and myelography can demonstrate further dynamic components of spinal stenosis that may go unrecognized on supine MRI.

PURPOSE

To describe a radiographic finding seen on standard supine MRI that is an indicator for dynamic spinal stenosis and degenerative spondylolisthesis.

STUDY DESIGN/SETTING

Case series.

PATIENT SAMPLE

Six patients.

OUTCOMES MEASURES

Radiographic observation.

METHODS

Six patients with classic neurogenic claudication but equivocal supine MRI findings were evaluated with myelography. The imaging findings were reviewed and compared.

RESULTS

All patients had severe position-dependent spinal stenosis upon upright myelographic imaging with grade I or II spondylolisthesis. The MRI showed very minimal to no spondylolisthesis. These dynamic slips reduced when supine, causing the vertebral bodies to appear aligned with adequate canal space, whereas the irregular facet joints became distended. Hypertrophic and fluid-filled facets at the dynamic slip level were seen in all patients, giving the appearance of a distended joint.

CONCLUSIONS

MRI may not demonstrate significant stenosis in patients with neurogenic claudication caused by dynamic degenerative spondylolisthesis. However, the presence of large fluid-filled facet joints indicates the likelihood of positional translation at that level which could be further confirmed by upright imaging.

Measuring CSF Flow in Chiari I Malformations

Cardiac-gated Phase Contrast MR (PC MR) is used in the evaluation of the Chiari I malformation to assess the CSF flow though the foramen magnum. Images may show reduced CSF flow posterior to the spinal cord in patients with a Chiari I malformation. MR images however do not differentiate with sufficient accuracy between symptomatic and asymptomatic Chiari I malformations. In the presence of the Chiari I malformation, CSF velocities are elevated. Measuring the velocity of flow and determining the degree of inhomogeneity in CSF flow aid in the detection of clinically significant flow abnormalities.

Dynamic MR and Quantitative MR Applied to the Study of Intervertebral Disk Degeneration

MR and CT demonstrate morphological changes in intervertebral disks. However the images do not provide an effective means to document interval changes in the disk due to degeneration, aging or healing. Functional imaging that may assesses the biomechanical or the biochemical integrity of the disk, may provide a measure of changes in the disk over time. To study the biomechanical function of the disk, translation and rotation of spinal vertebrae can be measured with CT or MR as the spine is subjected to a specific load or torque. Biochemical integrity of the disk can be assessed by the estimation of the water content from a measurement of the T2 relaxation time of disk tissue.

An Interspinous Process Distractor (X STOP) for Lumbar Spinal Stenosis in Elderly Patients

BACKGROUND

Lumbar spinal stenosis (LSS) is often a position-dependent condition that is aggravated in extension and relieved in flexion.

METHODS

Ten consecutive elderly patients with LSS were assessed postoperatively by magnetic resonance imaging and the Swiss Spinal Stenosis Questionnaire. Cross-sectional areas of the dural sac and intervertebral foramina at the stenotic level were measured postoperatively and compared with the preoperative values.

RESULTS

Postoperatively the cross-sectional area of the dural sac increased 16.6 mm2 or 22.3% and intervertebral foramina increased 22 mm2 or 36.5%. The intervertebral angle and the posterior disc height changed significantly. Seventy percent of the patients were satisfied with the surgical outcome.

CONCLUSION

This new surgical method is effective in elderly LSS patients.

Axial loaded MRI of the lumbar spine

Magnetic resonance imaging is established as the technique of choice for assessment of degenerative disorders of the lumbar spine. However, it is routinely performed with the patient supine and the hips and knees flexed. The absence of axial loading and lumbar extension results in a maximization of spinal canal dimensions, which may in some cases, result in failure to demonstrate nerve root compression. Attempts have been made to image the lumbar spine in a more physiological state, either by imaging with flexion-extension, in the erect position or by using axial loading. This article reviews the literature relating to the above techniques.

Neuroradiology of spine degenerative diseases

Degenerative disease of the spine is one of the most common clinical entities and affects the intervertebral discs, including opposing vertebral endplates, the intervertebral posterior joints and the ligaments. The most severe primary spinal degenerative changes are found in the lower cervical and lumbar spine regions. The spine contains three different types of joints, each of which presents its own pattern of degenerative disease: (i) cartilaginous joints, represented by the intervertebral disc or, more specifically, the functional unit defined as the 'vertebro-disc connection'; (ii) synovial joints, represented by the posterior intervertebral joints, sacro-iliac and costovertebral joints; (iii) fibrous joints, mainly found in the principal ligaments such as the posterior longitudinal ligament and the yellow ligaments. With regard to radicular pain, root compression alone does not fully account for root pain following disc-root conflict, but it is, nevertheless, considered to be the main cause of pain. We will try to explain that the origin of pain is multi-factorial and that inflammation probably predominates over merely mechanical mechanisms. To conclude, we will consider whether vertebral arthrosis can be construed as the body's decision to favour the spine's static function over its dynamic role when joint 'hypermobility' linked to chronic load in old age could cause severe structural damage to the bony vertebral structures. This hypothesis should also embrace a further concept: ageing of the spine is not merelychronological. Themostaccurate interpretation tha tcan account for similar degenerative phenomena encountered in the young is that of abnormal static and dynamic loading stress.

Morphologic changes in the lumbar intervertebral foramen due to flexion-extension, lateral bending, and axial rotation: an in vitro anatomic and biomechanical study

STUDY DESIGN

A biomechanical and anatomic study with human cadaveric lumbar spine.

OBJECTIVES

The purpose of this study is to examine the morphologic changes in the intervertebral foramen during flexion, extension, lateral bending, and axial rotation of the lumbar spine and to correlate these changes with the flexibility of the spinal motion segments.

SUMMARY OF BACKGROUND DATA

Previous studies showed morphologic changes in the intervertebral foramen during flexion and extension; however, those changes during lateral bending and axial rotation were not well known.

METHODS

There were 81 motion segments obtained from 39 human cadaveric lumbar spines (mean age 69 years). The motion segments were imaged with CT scanner with 1-mm thick consecutive sections. For biomechanical testing each motion segment was applied with incremental pure moments of flexion, extension, lateral bending, and axial rotation. Rotational movements of the motion segment were measured using VICON cameras. After application of the last load, the specimens were frozen under load, and then CT was performed with the same technique described above. Six parameters of the intervertebral foramen were measured, including foraminal width (maximum and minimum), foraminal height, disc bulging, thickness of ligamentum flavum, and cross-sectional area of the foramen.

RESULTS

Flexion increased the foraminal width (maximum and minimum), height, and area significantly while significantly decreasing the disc bulging and thickness of ligamentum flavum (P < 0.05). However, extension decreased the foraminal width (maximum and minimum), height, and area significantly. Lateral bending significantly decreased the foraminal width (maximum and minimum), height, and area at the bending side, whereas lateral bending significantly increased the foraminal width (minimum), height, and area at the opposite side of bending. Likewise, axial rotation decreased the foraminal width (minimum) and area at the rotation side significantly while significantly increasing the foraminal height and foraminal area at the opposite side. The percent change in the foraminal area was found significantly correlated with the amount of segmental spinal motion except for the extension motion.

CONCLUSIONS

This study showed that the intervertebral foramen of the lumbar spine changed significantly not only on flexion-extension but also on lateral bending and axial rotation. The percent change in cross-sectional foraminal area was correlated with the amount of segmental motion except for extension motions. Further studies are needed to assess the morphologic changes in the intervertebral foramen in vivo and to correlate clinically.

The relationship between disc degeneration and flexibility of the lumbar spine

BACKGROUND CONTEXT

A relationship between degenerative changes of the intervertebral disc and biomechanical functions of the lumbar spine has been suggested. However, the exact relationship between the grade of disc degeneration and the flexibility of the motion segment is not known.

PURPOSE

To investigate the relationship between degenerative grades of the intervertebral disc and three-dimensional (3-D) biomechanical characteristics of the motion segment under multidirectional loading conditions.

STUDY DESIGN/SETTING

A biomechanical and imaging study of human cadaveric spinal motion segments.

METHODS

One hundred fourteen lumbar motion segments from T12-L1 to L5-S1 taken from 47 fresh cadaver spines (average age at death, 68 years; range, 39 to 87 years) were used in this study. The severity of degeneration (grades I to V according to Thomson's system) was determined using magnetic resonance (MR) images and cryomicrotome sections. Pure unconstrained moments with dead weights were applied to the motion segments in six load steps. The directions of loading included flexion, extension, right and left axial rotation, and right and left lateral bending.

RESULTS

When the MR images were graded, 2 segments had grade I disc degeneration; 45, grade II; 20, grade III; 26, grade IV; and 21, grade V. When the cryomicrotome sections were graded, 14 segments had grade I disc degeneration; 31, grade II; 22, grade III; 26, grade IV; and 21, grade V. Segments from the upper lumbar levels (T12-L1 to L3-4) tended to have greater rotational movement in flexion, extension, and axial rotation with disc degeneration up to grade IV, whereas the motion decreased when the disc degenerated to grade V. In the lower lumbar spine at L4-5 and L5-S1, motion in axial rotation and lateral bending was increased in grade III.

CONCLUSIONS

These results suggest that kinematic properties of the lumbar spine are related to disc degeneration. Greater motion generally was found with disc degeneration, particularly in grades III and IV, in which radial tears of the annulus fibrosus are found. Disc space collapse and osteophyte formation as found in grade V resulted in stabilization of the motion segments.

Lumbar spine imaging. Normal variants, imaging pitfalls, and artifacts

Accurate recognition and reporting of spine abnormalities on MRI requires knowledge of normal anatomy and its variants. This article deals with common normal variants, points out pitfalls which may be sources of errors in interpretation and describes imaging artifacts which are essential to be recognized and not mistaken for true pathologies.

Positional MR imaging of the lumbar spine: does it demonstrate nerve root compromise not visible at conventional MR imaging?

PURPOSE

To evaluate whether positional magnetic resonance (MR) images of the lumbar spine demonstrate nerve root compromise not visible on MR images obtained with the patient in a supine position (conventional MR images).

MATERIALS AND METHODS

Thirty patients with chronic low back pain unresponsive to nonsurgical treatment and with disk abnormalities but without compression of neural structures were included. Positional MR images were obtained by using an open-configuration, 0.5-T MR imager with the patients seated and with flexion and extension of their backs. The disk and nerve root were related to the body position. Nerve root compression and foraminal size were correlated with the patient's symptoms, as assessed with a visual analogue scale.

RESULTS

Nerve root contact without deviation was present in 34 of 152 instances in the supine position, in 62 instances in the seated flexion position, and in 45 instances in the seated extension position. As compared with the supine position, in the seated flexion position nerve root deviation decreased from 10 to eight instances; in the seated extension position, it increased from 10 to 13 instances. Nerve root compression was seen in one patient in the seated extension position. Positional pain score differences were significantly related to changes in foraminal size (P =.046) but not to differences in nerve root compromise.

CONCLUSION

Positional MR imaging more frequently demonstrates minor neural compromise than does conventional MR imaging. Positional pain differences are related to position-dependent changes in foraminal size.

Functional MRI of the lumbar spine in erect position in a superconducting open-configuration MR system: preliminary results

The purpose of this study was to determine the feasibility of obtaining, and findings in, functional MRI of the lumbar spine in an erect position and with flexion and extension. Thirty subjects (including 5 volunteers) were imaged in a sitting position and while performing flexion and extension. The alternations in posterior disk margin, size of neural foramina, and central canal were evaluated. In addition, routine supine imaging was accomplished in 15 of these subjects. The foraminal size and posterior disk margins did not change appreciably from supine to upright position. With extension, there was an increased disk bulge in 27% of disks (40% of those with desiccation). Central canal size (50%) and foraminal size (27%) decreased with extension, especially at levels with disk desiccation. Images obtained with our open-configuration MR unit were diagnostically adequate, although of inferior quality compared with those obtained with a conventional unit. Our preliminary results show the feasibility of obtaining diagnostic images of the erect lumbar spine with flexion and extension. The results are in agreement with those obtained with cadaveric studies. The utility of this method in diagnostic imaging of patients with low back pain remains to be determined.

The stiffness of lumbar spinal motion segments with a high-intensity zone in the anulus fibrosus

STUDY DESIGN

Biomechanical and anatomic study of human cadaveric spinal motion segments.

OBJECTIVES

To measure the stiffness of spinal motion segments by disc type and by load type (flexion, extension, axial rotation, or lateral bending). To compare stiffness in motion segments with and without a high-intensity zone or radial tear in the anulus fibrosus.

SUMMARY OF BACKGROUND DATA

The high-intensity zone, that is a linear zone of high-intensity on T2-weighted magnetic resonance images corresponding to a radial tear in the anulus fibrosus, is a marker for a painful disc at discography. The high-intensity zone is hypothetically associated with diminished stiffness of the motion segment.

METHODS

Human cadaveric lumbar spinal motion segments with normal disc morphology or a high-intensity zone of the anulus fibrosus were selected on the basis of magnetic resonance imaging. The motion segments were subjected to incremental flexion, extension, rotation, and lateral bending torques. Rotation was measured with a kinematic system. Torque-rotation curves and stiffness were calculated for each motion segment and for each torque. The motion segments were sectioned on a cryomicrotome to verify the disc morphology as normal or as that of a radial tear.

RESULTS

In four motion segments with normal discs, stiffness was greater in axial rotation (8.4 Nm/degree) than in lateral bending (2.3 Nm/degree), flexion (1.8 Nm/degree), or extension (2.6 Nm/degree). In 16 motion segments with a high-intensity zone, stiffness was 2.4 Nm/degree in axial rotation, and less severely reduced in lateral bending, flexion, and extension. Stiffness in motion segments with a high-intensity zone was significantly less with smaller than with larger axial rotation loads.

CONCLUSIONS

The presence of a high-intensity zone in the intervertebral disc is associated with reduced stiffness of motion segments. The reduction is greater in axial rotation than in other torques. The reduction is more in smaller than in larger axial torques.

Lumbosacral spine imaging: physioanatomic method

Noninvasive evaluation of low back and leg pain has progressed rapidly over the past decade. The development of computed tomography, single-photon emission-computed tomographic bone scan, and magnetic resonance imaging has markedly increased diagnostic accuracy in detecting pathologic conditions. With this increased accuracy has come recognition of a 50% prevalence of underlying abnormalities in patients between 20 and 60 years old who have no symptoms. When such patients have a back injury, subsequent imaging will show in half of the population studied abnormalities that are not related to an acute injury. Degeneration of the spine progresses in all patients throughout their lifetime, and nearly all of the population will have back discomfort at some time. Political- and judicial-based compensation for back injuries related to accidents and on-the-job injuries provides an incentive for patients not to improve on therapy and to exaggerate symptoms, further complicating the clinical evaluation of their condition. The goal of physioanatomic noninvasive and invasive imaging evaluation presented in the following chapters is to increase specificity by differentiating pain generators from asymptomatic underlying pathologic conditions. When used with intensive conservative management and psychologic testing, this physioanatomic approach has resulted in much better treatment outcomes in our experience. The physioanatomic approach is quite simple, consisting of rigorous correlation of pathologic changes demonstrated by noninvasive imaging modalities (computed tomography, single-photon emission-computed tomographic bone scan, and magnetic resonance), or invasive modalities (diskography-enhanced computed tomography, nerve root block and facet block) with the patient's symptoms to evaluate whether the symptoms and the pathologic lesion are concordant or discordant. Patient symptoms and history are evaluated by use of a pain drawing and information sheet. The patient's pain pattern is categorized into a nonspecific pattern or into one of four recognizable pathway patterns (radicular, dorsal ramus, polyneuropathy, and sympathetic). Because each spinal lesion is typically manifested primarily via one of the four symptom pathways, the distribution of expected symptoms from each pathologic feature can be compared with the patient's pain drawing, and an assessment of the significance of imaged lesions can be made. The patient's presenting symptoms are also used to determine the most cost-effective and efficacious use of initial diagnostic imaging evaluation. In a minority of patients the findings on noninvasive imaging either will not correlate with the patient's symptoms or will demonstrate multiple abnormalities that could account for the patient's symptoms. In these patients, invasive techniques are extremely helpful in defining a pain generator or pain generators.(ABSTRACT TRUNCATED AT 400 WORDS)