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PubMed2001

A prospective study of factors predicting clinically occult spinal cord compression in patients with metastatic prostate carcinoma.

BACKGROUND: The objective of this study was to identify clinical parameters that predict occult subarachnoid space or spinal cord (SAS/SC) compression, as determined by magnetic resonance imaging (MRI), in patients with metastatic prostate carcinoma. METHODS: A prospective study was performed in which 68 patients with bone metastases from prostate carcinoma and a normal neurologic examination underwent MRI of the entire spine after documentation of clinical, X-ray, and bone scan parameters potentially predictive of occult SAS/SC compression. RESULTS: Occult SAS/SC compression was diagnosed in 22 patients (32%) using MRI. Nine patients (13%) had compressions at two discontinuous spinal levels. Extensive disease on bone scan, the duration of continuous hormonal therapy prior to study entry, and hemoglobin concentration were found to predict SAS/SC compression by univariate analysis. The extent of disease on bone scan and the duration of continuous hormonal therapy were independent predictors of SAS/SC compression by multivariate analysis (P = 0.02 and P = 0.04, respectively). The risk of occult SAS/SC compression increased from 32% to 44% in patients with a bone scan that showed > 20 metastases as the duration on hormones increased from 0 to 24 months. The risk in patients with fewer metastases increased from 11% to 17% over the same interval. The presence or absence of back pain was not predictive of SAS/SC compression. CONCLUSIONS: Patients who are at high risk for occult SAS/SC compression can be identified using clinical parameters and readily available diagnostic tests. These high-risk patients should undergo MRI screening with the aim of diagnosing and treating spinal cord compression before the development of neurologic deficits that may be irreversible.

Aged↗

PubMed1984

Role of stenosis of spinal canal in L4-L5 nerve root compression assessed by flexion-extension myelography.

Myelographic flexion-extension studies were performed in four groups of 10 patients each, with (A) normal myelogram; (B) bilateral nerve root compression at L4-L5; (C) unilateral nerve root compression at L4-L5 and (D) nerve root compression at L5-S1. The aim of the investigation was to assess the role of spinal stenosis in contributing to nerve root compression. The results indicate that a form of stenosis of the spinal canal plays an important role in bilateral nerve root compression at L4-L5, and to a lesser extent in unilateral nerve root compression at L4-L5. It does not appear to play a role in L5-S1 nerve root compression (stenosis of the lateral recess left aside). It is advocated that in myelographic L4-L5 nerve root compression additional flexion-extension studies should be performed in order to evaluate the possible role of stenosis of the spinal canal contributing to this compression. Even in nerve root compression by disc extrusion, concomitant spinal stenosis may necessitate additional decompressive laminectomy.

Humans↗

PubMed1989

Effects of spinal cord compression on repetitive impulse conduction of the ascending fibers of the dorsal column.

The effects of spinal cord compression on conduction of compound action potentials (CAPs) in the dorsal column fibers at various stimulus frequencies were analysed in pentobarbital anesthetised cats. The L 6 posterior root was given 1 to 500 Hz stimuli, and the CAPs were recorded from the L 2 posterior column. The 100th CAP was recorded at 100, 200 and 500 Hz. The L 4 cord segment was compressed by stepped increments (0.5 mm/5 min.) with a plastic plate (4 x 10 mm) until the responses at 1 Hz disappeared, then the compression was released. Before compression, each CAP at all frequencies showed almost uniform amplitudes and latencies. During compression, the CAPs were not altered significantly at any frequency until the spinal cord was compressed 2.5-4.0 mm. Further compression produced a progressive decrease in amplitude and increase in latency of the CAPs. At 500 Hz, however, the conduction block (amplitude loss, latency increase) was much severer than that produced at lower frequencies. After release of compression, the CAPs at all frequencies recovered progressively, and became almost stable after about 1 hour. The recovery rate of amplitude was only about 30% compared to the amplitude before compression at 500 Hz, and about 50% at 1 and 200 Hz. However, the recovery rate of amplitude at 100 Hz (65%) exceeded those at 1 and 200 Hz. To observe the difference in recovery rates among them, all the trains of CAPs were analyzed. Before compression, the amplitudes were almost uniform at stimulus frequencies as high as 500 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed2006

Improving diagnostic quality of MR images through controlled lossy compression using SPIHT.

This paper attempts to improve the diagnostic quality of magnetic resonance (MR) images through application of lossy compression as a noise-reducing filter. The amount of imaging noise present in MR images is compared with the amount of noise introduced by the compression, with particular attention given to the situation where the compression noise is a fraction of the imaging noise. A popular wavelet-based algorithm with good performance, Set Partitioning in Hierarchical Trees (SPIHT), was employed for the lossy compression. Tests were conducted with a number of MR patient images and corresponding phantom images. Different plausible ratios between imaging noise and compression noise (ICR) were considered, and the achievable compression gain through the controlled lossy compression was evaluated. Preliminary results show that at certain ICR's, it becomes virtually impossible to distinguish between the original and compressed-decompressed image. Radiologists presented with a blind test, in certain cases, showed preference to the compressed image rather than the original uncompressed ones, indicating that under controlled circumstances, lossy image compression can be used to improve the diagnostic quality of the MR images.

Algorithms↗

PubMed2002

Changes of wide dynamic range neuronal responses to mechanical cutaneous stimuli following acute compression of the rat sciatic nerve.

To investigate the changes in central neuronal activity in response to cutaneous stimulation following acute nerve compression, the responses of wide dynamic range dorsal horn neurons (n = 13) to graded mechanical cutaneous stimuli (brush, press, pinch, and squeeze) were recorded in anesthetized male Sprague-Dawley rats before and during compression, and after the release of the compression. A small vascular clip (pinching force, 120 g) was applied to compress the sciatic nerve for 30 min. In 12 neurons, background activities increased transiently for 1.5 to 4 min after nerve compression. Similarly, after the release of the compression, 7 neurons showed a transient increase in background activities. The responses to brush, press, and pinch were inhibited significantly 10 min after the nerve compression. The responses to press and pinch recovered gradually after the release of the compression. Responses to squeeze were little affected throughout the experimental period. Acute compression of the rat sciatic nerve can cause short periods of continuous increased spontaneous firing and can attenuate the dorsal horn neuronal responses to cutaneous stimuli. In particular, the neuronal responses to innocuous stimuli were more susceptible to compression of the nerve than the responses to noxious stimuli.

Acute Disease↗

PubMed1987

Morphologic changes in nerve cell bodies induced by experimental graded nerve compression.

The effects of experimental nerve fiber compression on the morphology of nerve cell bodies were studied. Rabbit cervical vagus nerves were crushed or subjected to compression at 0 (sham compression), 30, 200, or 400 mm Hg for 2 h. Morphometric measurements and light microscopical evaluation of the nerve cell bodies in the nodose ganglion were carried out 7 days after the injury on the injured and control sides. Crush and compression at 30, 200, or 400 mm Hg induced a slight decrease in total cell profile area compared with the control side, but it was not related to degree of injury. There was a marked decrease in the ratio between nuclear and total cell profile area (nuclear volume density) after compression at 200 and 400 mm Hg, as well as after crush, and to a lesser extent after compression at 30 mm Hg. Compression at 30, 200, or 400 mm Hg as well as crush of the vagus nerve induced migration of the nucleus to the periphery and dispersion of Nissl substance in the cytoplasm of the nerve cell bodies. Sham compression induced no obvious changes in total cell profile area, nuclear volume density, or migration of nucleus. There was a somewhat increased percentage of cells showing dispersion of Nissl substance in sham-compressed animals than in controls. The results show that nerve fiber compression induced pronounced reactive changes in nerve cell bodies, even at low pressures, corresponding to those found in human carpal tunnel syndrome. Such pressures are known to induce reversible inhibition of fast axonal transport as well as inhibition of retrograde axonal transport. The nerve cell body changes in the nodose ganglion may thus be a reaction to disturbances in axonal transport.

Animals↗

PubMed2003

Evaluation of the compression characteristics and physical properties of the newly invented one-step dry-coated tablets.

This study was conducted in order to clarify the compression characteristics, and to confirm the superiority of the physical properties, of the newly invented One-Step DRy-Coated tablets (OSDRC). We compared both the compression characteristics and the physical properties of OSDRC with those of physical-mixture tablets (PM) that were prepared with the same ingredients, quantity, and compression pressures. We selected potassium chloride (KCl) and acetaminophen (AAP) as the model drugs, since the former is known for its appropriate compression characteristics and the latter for its brittleness. The advantage of OSDRC is that they are capable of maintaining any kind of drug in their core, because the core is tightly surrounded by the outer layer, even when the drugs in the core have poor compression characteristics, which causes difficulties in forming a solid core tablet using conventional dry-coated tablet methods. The radial tensile strength of OSDRC was the same as, or superior to, that of PM containing of AAP. The results were in accordance with the compression process analysis performed according to Kawakita's equation. The friability of OSDRC was also superior to that of PM. These preferable characteristics were attributable to the high intensity of the OSDRC outer layer surface in comparison to that of PM. It was difficult to clarify the difference between OSDRC and PM in their physical properties when KCl was applied, since the tabletability of the whole tablet was high due to KCl's physical properties. The OSDRC containing AAP in their cores showed a controlled release pattern, though no other materials that have been known to influence drug release was present. It was considered that this controlled release pattern was caused by a reduced AAP particle surface area due to compression. It was confirmed with these experiments that the compression characteristics and the physical properties of AAP-OSDRC were superior to those of PM. These results indicated that it is possible to produce tablets that have materials with poor compression characteristics in the core portion, and high tabletability materials for the outer layers. In other words, it is possible to produce capsule-like tablets using the OSDRC compression method.

Acetaminophen↗

PubMed2005

Anisotropy, inhomogeneity, and tension-compression nonlinearity of human glenohumeral cartilage in finite deformation.

The tensile and compressive properties of human glenohumeral cartilage were determined by testing 120 rectangular strips in uniaxial tension and 70 cylindrical plugs in confined compression, obtained from five human glenohumeral joints. Specimens were harvested from five regions across the articular surface of the humeral head and two regions on the glenoid. Tensile strips were obtained along two orientations, parallel and perpendicular to the split-line directions. Two serial slices through the thickness, corresponding to the superficial and middle zones of the cartilage layers, were prepared from each tensile strip and each compressive plug. The equilibrium tensile modulus and compressive aggregate modulus of cartilage were determined from the uniaxial tensile and confined compression tests, respectively. Significant differences in the tensile moduli were found with depth and orientation relative to the local split-line direction. Articular cartilage of the humeral head was significantly stiffer in tension than that of the glenoid. There were significant differences in the aggregate compressive moduli of articular cartilage between superficial and middle zones in the humeral head. Furthermore, tensile and compressive stress-strain responses exhibited nonlinearity under finite strain, while the tensile modulus differed by up to two orders of magnitude from the compressive aggregate modulus at 0% strain, demonstrating a high degree of tension-compression nonlinearity. The complexity of the mechanical properties of human glenohumeral cartilage was exposed in this study, showing anisotropy, inhomogeneity, and tension-compression nonlinearity within the same joint. The observed differences in the tensile properties of human glenohumeral cartilage suggest that the glenoid may be more susceptible to cartilage degeneration than the humeral head.

Aged↗

PubMed2003

Comparison of the compression characteristics between new one-step dry-coated tablets (OSDRC) and dry-coated tablets (DC).

One-step dry-coated tablets (OSDRC) were prepared using materials which are generally used in pharmaceutical tablets. The radial tensile strength of OSDRC was measured for various compression pressures and core porosities before the final compression to compare with that of conventional dry-coated tablets (DC). Furthermore, stress relaxation in the compression process was investigated. Radial tensile strength and stress relaxation profiles of OSDRC were the same as those of conventional DC. X-ray computerized tomography (CT) of the tablets showed that the density distribution of both tablets was also the same. Thus, we concluded that OSDRC and conventional DC have the same compression characteristics and physical properties. The OSDRC-system was executed by the use of upper and lower punches, which had a double structure, a center punch, and an outer punch surrounding the center punch. The OSDRC process consists of three compressions to make the lower-outer layer (1st-outer layer), the core, and the whole tablet including the upper-outer and side-outer layers (2nd-outer layer). At first, the powder for the 1st-outer layer fills a space, which is made by the lower-center punch and lower-outer punch, and is pre-compressed by the upper-center punch. Then, while the upper-center punch pushes the pre-compressed 1st-outer layer, the lower-center punch is slid down. The upper-center punch is then pulled away to make a space, which is filled with the powder for the core. This is then pre-compressed by the upper-center punch. Finally, the lower-outer punch is slid downward and the powder for the 2nd-outer layer fills and surrounds the pre-compressed core/1st-outer layer completely. The core/1st-outer layer and the 2nd-outer layer complex is then compressed by the upper and lower punches in which the center punches are unified with the outer punches, respectively. This system can be assembled onto the turn table of a rotary tableting machine, and can make a dry-coated tablet in a single turn.

Ascorbic Acid↗

PubMed2001

A new rabbit model for the study on cervical compressive myelopathy.

Development process and pathology of myelopathy due to chronic spinal cord compression have not been fully elucidated. This study was conducted in order to establish an experimental model which can efficiently produce myelopathy and be useful in the studies on myelopathy due to chronic spinal cord compression. Under electrophysiological monitoring of the spinal cord, anterior compression was produced on C5 using a plastic screw. Two weeks later, a plastic plate was inserted under the C5 arch. For the subsequent 10 months on average, walking pattern and MR images were periodically monitored. Before the sacrifice, electrophysiological test was performed and then histopathological examination was done. Palsy appeared at 5 months on average after the addition of posterior compression. Mean compression ratio of the spinal cord calculated on MR images was 34%. All animals with compression showed a high intramedullary signal intensity, and the mean contrast-to-noise ratio (CNR) in the compressed area was 49%. Electrophysiological test showed a significant decrease in the amplitude of spinal cord evoked potentials (SCEPs) at the given compression level. Histology showed flattening of the anterior horn, disappearance and necrosis of anterior horn cells in the gray matter; and demyelination and axonal degeneration in the white matter. The antero-posterior compression produces the condition of spinal canal stenosis. Repeated antero-posterior compression to the spinal cord is important in establishing myelopathy. The present animal model was evaluated to be useful in the studies on myelopathy.

Animals↗

PubMed1998

Compression forces of haptics of freely rotating posterior chamber intraocular lenses.

PURPOSE: To measure the compressive forces of the haptics of 28 intraocular lens (IOL) models for different modes of compression and compare the results of two types of measurements. SETTING: Department of Ophthalmology, Central Hospital of Central Finland, Jyväskylä, Finland. METHODS: The haptics of 28 types of IOLs were compressed to a diameter of 9.0 mm between curved anvils. The compression forces in the plane of compression (i.e., in the plane of the optics) were measured at 0.5 mm intervals. During compression, the optics and the haptics were free to rotate with respect to the anvils. The results were compared with those of earlier measurements in which the optics were held fixed during compression. Perpendicular forces were measured at 0.4 mm intervals. RESULTS: The measured forces in the plane of the optics varied between 114 and 659 mg at a diameter of 10.0 mm and 192 and 1047 mg at a diameter of 9.0 mm. When compressed to 10.0 mm in diameter, the forces were 1 to 75% lower than when lens rotation was not possible. The forces perpendicular to the optic varied between 0 and 96 mg at a 10.0 mm diameter and correlated with the forces in the plane of the optic. CONCLUSION: The compression forces of the lens haptics were generally lower when the lenses were allowed to rotate during compression. The orders of stiffness of the haptics in these two measurements were similar. The perpendicular forces were generally small and correlated significantly with the forces measured in the plane of the optic.

Compressive Strength↗

PubMed1989

Spinal cord compression in small cell lung cancer: a retrospective study of 610 patients.

The records of 610 consecutive patients with small cell lung cancer, treated on a common protocol in a multicentre trial, were reviewed and 24 (4%) cases of spinal cord compression identified. Five hundred patients had isotope bone scans performed at presentation, and in 131 (26%) there was abnormal isotope uptake in the spinal column; only 7% of these patients developed spinal cord compression. However, of the 24 patients who presented with back pain and had a positive bone scan affecting the spine, 36% developed cord compression. Cerebral metastases occurred at some stage in 19.5% of all patients and in 45% of patients with cord compression. The combination of cerebral metastases and a positive bone scan gave a 25% chance of developing spinal cord compression. There were two distinct forms of clinical presentation. Six patients (group A) presented with cord compression: All had back pain and positive bone scans, five out of six had sphincter disturbance, and median survival from cord compression was 30 weeks. Eighteen patients (group B) developed cord compression while on treatment: 28% had positive initial bone scans, 44% back pain and 61% sphincter disturbance, and median survival from cord compression was 4 weeks. Spinal cord compression is an important cause of morbidity and mortality in small cell lung cancer. We suggest that it may be possible to select patients who should receive radiotherapy to the spine to try to prevent the development of this complication.

Adult↗

PubMed2000

The potent role of increased sympathetic tone in pathogenesis of essential hypertension with neurovascular compression.

OBJECTIVE: To study the role of increased sympathetic tone in pathogenesis of hypertension in patients with essential hypertension with neurovascular compression. METHODS: Twenty-three patients with essential hypertension, 13 patients with secondary hypertension, and 46 normotensive subjects were investigated. Neurovascular compression was evaluated by MRT. The power spectral components of heart rate variability as indices of autonomic nerve tone were determined to investigate the possibility that sympathetic tone mediates the neurovascular compression-induced increase in blood pressure. RESULTS: Neurovascular compression of the rostral ventrolateral medulla (RVLM) was observed in 70% of essential hypertension group, none of secondary hyperension group and 16% of normotensive group (P < 0.001). The age-adjusted low-frequency power spectral density (A-PSD) (0.04 to 0.15 Hz), which is an index of sympathetic tone, was significantly higher in patients with essential hypertension (139.5 +/- 6.7%) with neurovascular compression than in essential hypertension patients without neurovascular compression (92.2 +/- 6.8%), normotensive subjects with (102.8 +/- 13.0%) and without neurovascular compression (100.1 +/- 4.1%), and patients with secondary hypertension (95.7 +/- 10.2%) (P < 0.001). There was no significant difference in the high-frequency A-PSD (0.15 to 0.40 Hz), which is an index of vagal tone, among groups. CONCLUSIONS: Neurovascular compression was not always associated with an increase in sympathetic nerve tone. Hypertension was present in subjects with neurovascular compression, who had increased sympathetic tone but not in those with normal sympathetic tone. An increase in sympathetic tone may mediate the neurovascular compression-induced increase in blood pressure. Journal of Human Hypertension (2000) 14, 807-811

Adult↗

PubMed2004

Morphologic change and astrocyte response to unilateral spinal cord compression in rabbits.

In myelopathy, unilateral compression of the spinal cord in cases of disc herniation would be expected to produce Brown-Séquard syndrome. However, a transverse lesion syndrome occurs in most clinical cases. In order to reveal the mechanism by which unilateral compression induces transverse damage to the spinal cord, damage of the gray and white matter in each half of the spinal cord were evaluated quantitatively to determine the density of GFAP-positive astrocytes. The cervical spinal cord in rabbits was unilaterally compressed with a small screw. The area of each half of the damaged cord and the density of GFAP-positive astrocytes of the compressed and contralateral halves were investigated one week after the surgery. No apparent paralysis was observed during the period of observation. As the compression increased, the area of the compressed half of the spinal cord decreased significantly compared to the contralateral half. The densities of GFAP-positive astrocytes in the gray matter and the anterior funiculus increased significantly in the compressed half. There were no significant differences in the densities at the lateral and dorsal funiculi between the compressed and contralateral halves. The tissue damage in the gray matter of the compressed half was markedly higher. No significant difference between the two halves in damage was seen in the lateral funiculus, where in the lateral pyramidal and the dorsal spinocerebellar tracts are found. These findings provide evidence of the mechanistic basis for the spinal cord damage that leads to transverse lesion syndrome in unilateral compression myelopathy.

Animals↗

PubMed1995

Astrocytic reaction after graded spinal cord compression in rats: immunohistochemical studies on glial fibrillary acidic protein and vimentin.

The relation between the degree of spinal cord compression and the extent of early posttraumatic reaction of astrocytes was investigated in rats using the blocking-weight technique to induce a spinal cord compression at the level of the Th8-9. Immunohistochemistry was used to detect changes in the expression of glial fibrillary acidic protein (GFAP) and vimentin up to 24 h after injury. A mild compression, which did not cause any measurable neurological deterioration, induced a mild increase of GFAP immunoreactivity at 4 h and a more marked and widespread immunoreactivity at 24 h. The greatest increase of GFAP immunoreactive astrocytes occurred in rats with moderate compression of the cord causing reversible paraparesis and in animals with severe compression leading to paraplegia. The increase of GFAP immunoreactivity was present already 4 h after injury in virtually all the segments investigated (Th5-6-Th11-12) and was most marked at 24 h. Vimentin immunoreactivity of control rats was present in the ependymal cells of the central canal, the leptomeninges, and walls of a few intramedullary vessels. Occasional astrocytes were stained. In rats surviving 24 h after moderate and severe compression vimentin immunoreactivity was increased in the walls of intramedullary blood vessels including capillaries of one rostral and one caudal segment. Many macrophages with immunoreactivity appeared and occasional glial cells with astrocyte shape were stained. This investigation shows that within 24 h after compression of the spinal cord a widespread astrocyte reaction occurs. Even a mild compression that does not produce any signs of motor dysfunction can induce widespread astrocyte alterations in the spinal cord. This astrocyte response is more marked in rats with more severe compression leading to more pronounced neurological deterioration. The increase in vimentin immunoreactivity of blood vessels is more localized and occurs in moderate and severe compression of the cord.

Animals↗

PubMed2000

Effect of implant design and endplate preparation on the compressive strength of interbody fusion constructs.

STUDY DESIGN: A human cadaveric study on the compressive strength of different lumbar interbody fusion implants and endplate preparation techniques was performed. OBJECTIVES: To assess the axial compressive strength of an implant with peripheral endplate contact as opposed to full surface contact, and to assess whether removal of the central bony endplate affects the axial compressive strength. SUMMARY OF BACKGROUND DATA: The compressive strength of interbody fusion constructs has been compared between implants and bone grafts. Neither implant design nor endplate preparation has been shown to affect strength. Removal of the central bony endplate for bone grafts was noted to improve graft incorporation but also to facilitate subsidence. METHODS: A total of 44 vertebrae were tested in four experimental groups by combining two interbody implants (full-surface vs peripheral surface support) with two endplate preparation techniques (intact bony endplate vs removal of the central bony endplate). Specimens were tested to ultimate compressive failure using a 50 N/second ramped load. Yield strength and ultimate compressive strength were compared between groups using two-factor analysis of covariance. A P value less than 0.05 was considered significant. Stepwise linear regressions assessed the predictive power of age, bone mineral content, and the implant's normalized endplate coverage on yield strength and ultimate compressive strength. RESULTS: Neither implant design nor endplate preparation technique affected yield strength or ultimate compressive strength. Age, bone mineral content, and the normalized endplate coverage were strong predictors of yield strength (P < 0. 0001; r2 = 0.459) and ultimate compressive strength (P < 0.0001; r2 = 0.510). CONCLUSIONS: An implant with only peripheral support resting on the apophyseal ring offers axial mechanical strength similar to that of an implant with full support. Neither supplementary struts nor a solid implant face has any additional mechanical advantage, but reduces graft-host contact area. Removal of the central bony endplate is recommended because it does not affect the compressive strength and promotes graft incorporation.

Adolescent↗

PubMed2003

Effects of a cervical compression plate on graft forces in an anterior cervical discectomy model.

STUDY DESIGN: An ex vivo biomechanical study using an instrumented distractor and load cells in a cadaveric multilevel discectomy construct was conducted. OBJECTIVE: To demonstrate that a dynamic cervical plate can be used to increase compressive load on interbody grafts in a multilevel discectomy specimen. SUMMARY OF BACKGROUND DATA: Cervical plating is used to decrease pseudarthrosis, graft extrusion, and graft subsidence in multilevel anterior discectomy procedures. Plating may shield a graft as it resorbs and may reverse normal loading mechanics. METHODS: Preoperative disc height was measured in five cadaveric spines. A three-level discectomy was performed. The disc spaces were opened with a distractor instrumented with strain gauges to allow the introduction of spacers fixed rigidly to subminiature load cells. Distraction was removed, and immediate compressive forces were measured by the load cells. An external compressor was applied followed by a cervical plate. The specimen then was placed in a loading frame, and final compressive forces were measured. RESULTS: A mean 116.5 N distractive force was required to insert grafts into all three levels. No significant relation between preoperative disc height and distractive or compressive forces was noted. Release of the distractor yielded an immediate compressive load on each graft. The compressor significantly increased graft compression. After plate application, the external compressor was removed. Graft compression did not significantly decrease. In the loading frame, an increase in compressive load was noted. CONCLUSIONS: Preoperative disc height was not related to the compressive force on the graft. Compressive force can be increased and maintained with a dynamic plating system.

Aged↗

PubMed2005

Effect of lumbar nerve root compression on primary sensory neurons and their central branches: changes in the nociceptive neuropeptides substance P and somatostatin.

STUDY DESIGN: This study examined the effect of lumbar nerve root compression on nociceptive neuropeptides in the axonal flow using an in vivo model. OBJECTIVES: The aim was to investigate changes in axonal flow after nerve root compression by using immunohistochemical techniques to detect substance P (SP) and somatostatin (SOM), which is thought to be involved in temperature and pain sensation. SUMMARY OF BACKGROUND DATA: Disturbance of intraradicular blood flow and nerve fiber deformation caused by mechanical compression are thought to be involved in the pathophysiology of diseases characterized by radicular symptoms, such as lumbar disc herniation and lumbar canal stenosis. However, little research has been conducted into the changes of axonal flow associated with nerve root compression. METHODS: In dogs, the lumbar nerve roots were compressed using four types of clips with different pressures. Changes of SP and SOM levels in the spinal dorsal horn, dorsal root, and dorsal root ganglions were examined immunohistochemically after compression for 24 hours or 1 week. RESULTS: After compression for 24 hours, axonal flow in the dorsal root was impaired, accumulation of SP and SOM was observed distal to the site of compression, and there was a decrease in the number of dorsal root ganglion cells showing positively for these neurotransmitters. Compression for 1 week resulted in a decrease in the number of SP- and SOM-positive fibers in the spinal dorsal horn. CONCLUSION: Change of axonal flow resulting from direct nerve compression could affect the metabolism of neurotransmitters that flow inside the axons and may be a primary cause of the decline in nerve function.

Animals↗