摘要:

Study Design.An electrophysiologic study to examine responses of dorsal horn neurons in the rat L5 spinal cord to noxious stimuli after disc herniation or application of the nucleus pulposus to the L5 nerve root.Objectives.To investigate the pathogenic role of nucleus pulposus in the neural mechanism underlying sciatica and low back pain.Summary of Background Data.Application of the nucleus pulposus to the lumbar nerve root induced morphologic, vascular, and functional changes in the nerve root, suggesting that some factors in the nucleus pulposus may be implicated in the pathogenesis of chronic changes. However, it has not been studied whether the epidural application of nucleus pulposus enhances nociresponses of pain-processing neurons in the superficial dorsal horn of the spinal cord.Methods.Extracellular recordings were made from the L5 dorsal horn neurons in 20 Wistar rats. The wide-dynamic-range (WDR) neurons activated by electric stimulation of the ipsilateral footpad of hindpaw were selected, and their responses to noxious and innocuous stimulation were examined after L5–L6 disc herniation onto the L5 nerve root (Group A) and application of the autologous nucleus pulposus (Group B) or fat tissues (Groups C and D).Results.The herniation of the nucleus pulposus (Group A) and application of the autologous nucleus pulposus (Group B) to the nerve root remarkably enhanced responses of WDR neurons to noxious stimuli for hours, whereas application of fat tissue scarcely enhanced nociresponses (Groups C and D).Conclusions.Results suggest that somewhat pathogenic factors in the nucleus pulposus may have a crucial role in the induction of hyperalgesia. This may help to elucidate the reason why a severe pain is sometimes induced without a visually identified protrusion.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.Electrophysiologic recordings were obtained from a lumbar paraspinal nerve or muscle in the anesthetized cat while electrically stimulating a paraspinal nerve or facet capsule in an adjacent lumbar segment. A variety of approaches were used to demonstrate the reflex nature of both the nerve and the muscle response.Objective.The primary purpose of this study was to seek electrophysiologic evidence for the presence of intersegmental reflexes between adjacent lumbar vertebral segments. A second purpose of this study was to confirm a previous procedure used to evoke paraspinal reflexes. This previous work had shown that electrical stimulation of the L1–L2 facet joint capsule elicits electromyographic activity from multifidus muscle one to two vertebral segments caudal to the stimulated facet in a porcine preparation.Summary of Background Data.Biomechanical approaches have stressed the need for spinal stability to avoid conditions that could give rise to low back dysfunction. It seems reasonable to believe that reflex interactions between vertebral segments contribute to the sensorimotor integration of lumbar paraspinal tissues. It also seems reasonable to believe that alterations or abnormal elicitation of these reflexes could contribute to biomechanical changes associated with low back pain and paraspinal muscle spasm.Methods.Experiments were performed on 23 &agr;-chloralose anesthetized adult cats. In eight cats the L3, L4, and L5 medial branch from each dorsal ramus was exposed and placed on a bipolar hook electrode. In six cats the L4 medial branch was stimulated and a compound action potential was recorded from the L3 medial branch. In three of the six cats the L5 medial branch was stimulated and a compound action potential was recorded from the L3 medial branch. In one cat the L4 medial branch was stimulated and a compound action potential was recorded from the L5 medial branch. In one cat the L3 medial branch was stimulated and a compound action potential was recorded from the L5 medial branch. At the end of each protocol the medial branch was cut just proximal to the stimulating electrode to confirm that the compound action potential was reflexive in nature and not initiated by volume conduction. In 15 cats three approaches were used to confirm that multifidus electromyographic activity evoked by electrical stimulation of a lumbar facet capsule was reflexive in nature: 1) by anesthetizing the site of the sensory endings,i.e., the facet capsule, 2) by injecting lidocaine intrathecally to block neural conduction centrally,i.e., within the spinal canal, or 3) by cutting the afferent pathway,i.e., the medial branch of the dorsal ramus.Results.Electrical stimulation of the medial branch of the dorsal ramus innervating the medial-most lumbar paraspinal tissues evoked a compound action potential in the medial branch innervating the medial-most paraspinal tissues one and two segments away. Stimulating voltages between 2 and 70 V were necessary to evoke the compound action potential. Each compound action potential was reflexive in nature because cutting the lumbar medial branch proximal to its contact with the stimulating electrode abolished each compound action potential. The conduction velocity of the reflex ranged from 3.5 to 6.1 m/sec. Electrical stimulation of a lumbar facet capsule evoked lumbar multifidus muscle electromyographic activity. However, injecting lidocaine intrathecally or transecting the medial branch of the dorsal ramus had no effect on electromyographic activity. Injecting lidocaine into the facet or into the multifidus muscle around the facet joint (near the stimulating electrode) significantly decreased the magnitude of the multifidus electromyography.Conclusion.These results indicate that afferent impulses conveyed by the medial branch of the dorsal ramus reflexly altered efferent activity to an adjacent lumbar segment. This intersegmental paraspinal reflex may span at least one or two vertebral segments. The data suggest that electrical stimulation of the facet joint capsule may not have reflexly elicited multifidus activity because neither chemical interruption (intrathecal lidocaine) nor physical interruption (nerve transection) of the presumed reflex pathway diminished or abolished the electromyographic response. Volume conduction of the stimulating currents likely elicited multifidus activity during electrical stimulation of the facet capsule. When using electrical stimulation of neural paraspinal tissues to evoke reflex muscle activity, appropriate control experiments must be performed to clearly demonstrate the reflexive nature of the response.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.Anin vitrohuman cadaveric study comparing the effects of anterior and posterior sequential destabilization conditions on thoracic functional unit mechanics was studied.Objectives.To investigate the biomechanical properties of the human thoracic spine.Summary of Background Data.Few studies have addressed the mechanical role of the costovertebral joints under torsion in the stability of the human thoracic spine.Methods.Sixteen functional spinal units with intact costovertebral joints were obtained from six human cadavers and randomized into two groups based on destabilization procedures: Group 1, anterior to posterior sequential resection; and Group 2, posterior to anterior sequential destabilization. Biomechanical testing was performed after each destabilization procedure, and the range of motion under maximum load was calculated.Results.Group 1: Under flexion–extension, lateral bending, and axial rotation loading, discectomy increased the range of motion by 193%, 74%, and 111%, respectively. Moreover, subsequent right rib head resection further increased the range of motion by 81%, 84%, and 72%, respectively. Group 2: Under all loading conditions laminectomy + medial facetectomy resulted in a 22–30% increase in range of motion. Subsequent total facetectomy led to an additional 15–28% increase in range of motion.Conclusion.The rib head joints serve as stabilizing structures to the human thoracic spine in the sagittal, coronal, and transverse planes. In anterior scoliosis surgery additional rib head resection after discectomy may achieve greater curve and rib hump correction. The lateral portion of the facet joints plays an important role in providing spinal stability and should be preserved to minimize postoperative kyphotic deformity and segmental instability when performing decompressive wide laminectomy.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.Repeated-measures analysis of variance: within-subject study using six adult subjects with varying degrees of scoliosis.Objectives.To develop methodology to measure the effects of axial spinal unloading using the LTX3000 Lumbar Rehabilitation System (Spinal Design International Inc., Minneapolis, MN) over a 3-month period on subjects with idiopathic scoliosis. To look for sustained treatment benefits, thus measuring the duration of changes induced on lateral scoliotic curves over the 3-month period after intervention with the LTX3000 Lumbar Rehabilitation System.Summary of Background Data.Current treatments for idiopathic scoliosis have shown mixed results in managing curve progression. Little research has been done to show the effectiveness of axial spinal unloading in changing the curvature of the spine.Methods.Baseline data were obtained from four radiographs (two frontal plane, two sagittal plane), surface electromyograms, and back range of motion measurements. Data were collected at four laboratory sessions (baseline, 3 months, 4 months, and 6 months), and the intervention was given between baseline and the 3-month sessions. The intervention phase consisted of axial unloading, two treatments a day for 10 minutes per session, using the LTX3000 Lumbar Rehabilitation System.Results.Static change of Cobb angle values over time showed statistical significance (P= 0.02, &agr; = 0.05). Dynamic change of Cobb angle values within sessions showed statistical significance (P= 0.036, &agr; = 0.05).Conclusions.Results from this study showed a significant decrease in Cobb angle measurements in the lumbar curvature during the intervention phase. Once the home intervention program was terminated, the lateral lumbar curvature reverted to baseline values (pre-intervention).

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.Case reports of ruptured cervical disc after spinal manipulation therapy.Objectives.To present the rare cases of ruptured cervical disc temporally related to spinal manipulation therapy.Summary of Background Data.The complication of ruptured cervical disc was rare in the literature.Methods.Two patients developed cervical myelopathy or radiculopathy after spinal manipulation therapy, and magnetic resonance imaging showed herniated cervical discs at C4–C5 and C6–C7, respectively.Results.Anterior cervical discectomy was performed, and ruptured disc fragments were removed in these two patients. Both patients had good neurologic recovery after operation, and no neurologic deficits were noted after 15 and 6 months of follow-up, respectively.Conclusions.The experience of these two patients reminds us that cervical disc rupture can occur during a course of cervical spinal manipulation. Full neurologic recovery is achievable if accurate diagnosis and prompt surgical treatment are done.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.In Study 1 the authors measured the vertical and sagittal dimensions of the intervertebral foramen in dried lumbar vertebrae. In Study 2 the dimensions of the intervertebral foramen were measured in fresh cadaveric spines in which the soft tissues forming the foraminal walls were preserved.Objectives.To investigate whether disc narrowing, or other factors related to the morphometry of lumbar vertebrae, may predispose to foraminal stenosis.Summary of Background Data.Predisposing factors to foraminal stenosis have been little investigated. Previous studies suggested that narrowing of the disc space might cause a reduction in the foraminal dimensions; however, it is not clear whether such a reduction is to such an extent as to compress the nerve root within the foramen.Methods.In Study 1 the vertical and sagittal dimensions of 160 intervertebral foramens were measured on dried white spines. Measurements were performed in the presence of a normal height of the disc space, obtained using a silicone rubber disc, and repeated in the same specimen after disc removal. Foraminal dimensions were then related to the sagittal diameter of the spinal canal and the pedicle length. In Study 2, the authors evaluated the dimensions of 50 intervertebral foramens of fresh cadaveric spines, in which the soft tissues forming the foraminal walls and the nerve root were preserved. In specimens showing normal or slightly decreased disc height, the foraminal dimensions were measured before and after disc excision.Results.In Study 1 the reduction in the foraminal height after disc removal was, on average, 6.5 mm (P< 0.0001). In both Studies 1 and 2 the sagittal dimensions of the foramen were not significantly reduced after disc removal. No significant difference was found in Study 1 in the sagittal dimensions of the foramen between specimens showing normal or degenerated facet joints. In Study 2 a compression of the nerve root within the foramen was found in one specimen, showing a concomitant central stenosis at multiple levels. A significant correlation was found between the sagittal diameters of the foramen and the sagittal diameter of the spinal canal and the pedicle length.Conclusions.Narrowing of the disc space significantly reduces the vertical diameter of the foramen but has no significant effects on its sagittal dimensions. In contrast, the sagittal dimensions of the foramen are strictly related to the sagittal diameter of the spinal canal and the pedicle length. These results suggest that in patients with developmental or combined stenosis of the central spinal canal, a concomitant foraminal stenosis is likely to be present, or at least should be suspected.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.This report is composed of two studies, one cross-sectional and one prospective cohort study, that analyze the radiologic features of disc degeneration in the sand rat (Psammomys obesus).Objectives.To statistically assess progressive disc degeneration in this useful animal model in terms of a cross-sectional study and a prospective monthly evaluation of individual animals.Summary of Background Data.P. obesusis an attractive small rodent model for spontaneous age-related disc degeneration. Because disc degeneration is spontaneous, the model avoids use of chemonucleolysis or surgical injury to cause disc degeneration. Little is understood, however, about specific details of the progressive disc deterioration.Methods.This study statistically assessed 158 animals in a cross-sectional study and 22 animals in a longitudinal study, which followed individual animals to 12 months of age. Radiologic features involving irregular disc margins, disc wedging, disc narrowing, endplate calcification, subchondral sclerosis, ligament calcification, and osteophyte formation were studied.Results.Significant age-related cross-sectional changes were present for all features (P≤ 0.005). Males showed a statistically greater incidence of wedging at 6 and 12 months, wedging at 2 and 6 months, and endplate calcification at 2 months than did females. By 6 months of age, however, endplate calcification had a higher incidence in females than in males. Prospective analysis showed that wedging, narrowing, endplate calcification, and irregular disc margins were more common at 12 months of age than at 2 months (P= 0.0001). By the age of 12 months, all lumbar sites of both males and females showed endplate calcification and the majority of animals showed narrowing and wedging.Conclusions.Radiographic signs of degeneration were evident by age 2 months; wedging, narrowing, irregular disc margins, and endplate calcification were the most common degenerative changes in older animals. These data show that the sand rat provides a reliable, useful model of spontaneous disc degeneration.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.Anin vitrobiomechanical study.Objective.To examine disc integrity at levels adjacent and next adjacent to the fractured vertebra and to determine if the disc injury can be revealed by radiographs.Summary of Background Data.Thoracolumbar burst fracture is one of the most common spinal injuries. A fractured vertebra is easy to recognize, but the associated disc injuries are less well known. The disc injury may not be apparent in radiographic images. Quantitative discomanometry, which measures disc pressure and the injected volume, has been found to detect disc injury.Methods.Nine specimens (T11–L3) with L1 burst fracture included adjacent discs (T12–L1 and L1–L2) and next-adjacent discs (T11–T12 and L2–L3) and were examined with radiographs and quantitative discomanometry, before and after the burst fracture. Statistical analyses were used to determine if the nine quantitative discomanometry parameters, in each of the four discs, were changed by the burst fracture and if the two next adjacent discs sustained different injuries.Results.After the burst fracture both the adjacent discs were shown to be injured by both radiographic and quantitative discomanometry examinations. Whereas both next-adjacent discs were found to be uninjured by radiograph examination, the quantitative discomanometry found the lower next-adjacent disc (L2–L3) to be injured.Conclusions.Quantitative discomanometry was successful in finding disc injury, where the radiographs found none. The lower level, next adjacent disc is susceptible to injury during the burst trauma.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.Ten cervical spine trauma subjects were studied during halovest treatment. Each subject wore each of three different vests.Objectives.To compare the effect of vest design on loads between halo and vest during various activities.Summary of Background Data.Complications during halovest use may be related to vest design, a variety of which are available. Loads between halo and vest have been shown to vary with activity type, but no comparison between vest types has been reported previously.Methods.Loads between the halo and the vest were measured during performance of activities of daily living and during load application to the halo, using custom-built four-channel transducers and a PC-based data acquisition system.Results.Substantial variations between subjects exist in loads between the halo and the vest. At rest, neck distraction loads were significantly greater for the supine posture than for either the sitting or standing postures. Loads applied to the halo by the investigators are carried by the neck and not by the structure connecting the halo to the vest. During activities of daily living all four measured load components are generally nonzero. During activities of daily living substantial differences in loads occurred between vest types. For all activities of daily living combined, the relative neck distraction load values were as follows: 4PAD 100%, Bremer 159%, and PMT 180%.Conclusions.Previous evidence supports a connection between certain complications of halovest wear (such as pin loosening) and loads on the pins. This study shows that different halovests are associated with quite different loads between the vest and the halo (and thus loads on the pins and the neck). This is encouraging for prospective, clinical comparison of different halovests and for improvements in clinical performance through halovest design improvements.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Study Design.A radiographic analysis of the cervical spine in healthy young adults.Objectives.To investigate the size correlations among the vertebral height, the anteroposterior diameter of the vertebral body, and the anteroposterior diameter of the spinal canal and to investigate the sex discrepancy of the canal/body ratio.Summary of Background Data.Narrow spinal canal, large vertebral body, and male gender have been thought to be risk factors for cervical myelopathy. However, the association among those risk factors has been seldom analyzed.Methods.The height and the anteroposterior diameter of the vertebral body as well as the anteroposterior diameter of the spinal canal were measured on the lateral radiographs of healthy young adults (105 men and 114 women) using a distance-measuring tool of computer software. The canal/body ratio was compared between men and women.Results.The height and the anteroposterior diameter of the vertebral body were both larger in males than in females throughout C3–C7, but the anteroposterior diameter of the spinal canal was similar for both sexes. The height of the vertebral body was not correlated with the spinal canal size at any measured segment in both sexes, whereas the anteroposterior diameter of the vertebral body was significantly correlated with the size of the spinal canal in males but not in females. The canal/body ratio was significantly larger in women than in men.Conclusions.A significantly small canal/body ratio in men may implicate the male prevalence of cervical myelopathy.

ISSN:0362-2436    

出版商:OVID    

年代:2002

数据来源: OVID