摘要:

A well-controlled experimental model for analysis of compression-induced functional changes of the porcine cauda equina is presented. The model allows for electrophysiologic investigation of a variety of neurophysiologic changes induced by nerve root deformation. At an acute pressure threshold of 50-75 mm Hg, changes in both afferent and efferent conduction are induced. With higher compression pressure, a differential recovery in afferent and efferent conduction is seen.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Postlaminectomy deformities were simulated in the cervical or cervicothoracic spine by the use of a displacement incremental method based on finite-element analysis combined with composite material and spanning element theory. The simulation analyses revealed that the primary cause of postlaminectomy deformity was the resection of one or more spinous processes and/or posterior ligaments (ie, ligamenta flava, supraspinous, and interspinous ligaments). After their removal, the tensile stresses that were preoperatively distributed through the posterior ligaments were transferred to the facets. This led to an imbalance of the stresses on the spinal bodies, causing deformity. The gravitational center of the head determined whether the deformity would develop as a kyphosis or increasing lordosis. As the elastic modulus of the soft tissue composites (eg, end plates, ligaments, and facets) increased, a kyphotic deformity changed gradually from swan-neck deformity, to extreme kyphotic deformity with a large curvature, and finally to a straightening deformity. Progressive kyphotic deformity is found only in children.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The influence of the ultrasonic surgical aspirator on the dura and underlying spinal cord was examined. Spinalcord-evoked potential was simultaneously recorded. In a test of identical time, the degree of influence on the dura, the pia mater, and the spinal cord increased according to the increase of energy of the ultrasonic surgical aspirator. With 60% energy at 20 seconds and 80% energy at both 10 and 20 seconds, spinal-cord-evoked potential showed wave changes. In light of these results, it is suggested that in using the ultrasonic surgical aspirator on the dura, the electrohistologic safety limit be set at 60% energy and the maximum time duration at one point less than 10 seconds.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In a cadaver-derived skeletal collection of 1,384 thoracolumbar spinal columns, 103 (7.4%) individuals with vertebral changes of Scheuermann's kyphosis were identified. Anterior extension of the vertebral specimens was noted in 94% of affected specimens. No evidence of osteoporosis was noted by single-photon absorptiometric analysis in the affected sample compared with a normal control group. Biopsy specimens from two immature patients obtained at surgery suggested disorganized endochondral ossification similar to that noted in Blount's disease. It was concluded that increased pressure on the anterior margin of the centrum is responsible for histologic and morphologic changes of Scheuermann's kyphosis.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

This study was designed to determine the validity and reliability of a new electrogoniometer devised and developed for the measurement of sagittal dorsolumbar movements (T8-S1). The validity was measured in 10 normal subjects by comparison of the angle values obtained with the electrogoniometer with those obtained with the twoinclinometer method previously validated with x-ray measurements. The total range of movement was divided into 5° steps, and the angle value obtained with both methods was recorded at each of these steps. The testing procedure was repeated (retest) after removal and reattachment of the electrogoniometer. Because the potentiometer of the electrogoniometer measures angular changes indirectly from changes in the curvature of a flexible slat, a special individual calibration procedure was applied, and computation of the electrogoniometric angles (Ec) representing the dorsolumbar movement was made by software. Regression analysis of Ec in relation to corresponding inclinometric angles gave a slope of 1.03 and a Pearson's correlation coefficient of 0.97, indicating a high concurrent validity between the two methods. The intraclass correlation coefficient between test and retest (ICC = 0.982) confirmed the high reproducibility of the measurement procedures. The length of the slat can be changed to adapt the electrogoniometric system to different statures. Under standardized conditions, this new electrogoniometer can provide continuous measurements of sagittal dorsolumbar movements that are reproducible with an accuracy comparable to that obtained with the two-inclinometer method.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

This study deals with age changes in the anulus fibrosus of the lumbar intervertebral discs of human individuals 21-83 years of age. The anular laminas from individuals less than 40 years of age consisted of obliquely orientated collagen fibers exhibiting a pennate arrangement. These fibers were intensely argyrophilic after silver nitrate impregnation. The fibers and surrounding substance appeared light pink after exposure to the periodicacid- Schiff (PAS) reaction and blue with alcian blue complex. Beginning during middle age and continuing into the eighth decade, there was a progressive degeneration of the laminas. The breakdown of the intact laminas was characterized by the fraying, splitting, and loss of collagen fibers. The newly formed spaces became filled with intense PAS-positive material. In addition, there was a continual deposition of chondroid substance in the anuluses of the aging discs. This phenomenon was not seen in the young disc. These age related changes lead to a loss of integrity to the disc, which may be a factor in disc pathology.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The lumbar intervertebral foramens of 20 isolated cadaveric spines were investigated by the use of a molding technique to assess their dimensions accurately and how intervertebral disc pathology altered their configuration. Oval foramens predominated over auricularly shaped foramens when the disc was normal, but when the disc was abnormal, the converse was true. Foraminal size varied from 40 to 160 mm2but showed great variation even at individual levels; these were not accurately reflected by simple radiologic measurements.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In this study, the relationship between facet geometry (joint angle and tropism) and disc degeneration was analyzed. Magnetic resonance imaging and computed tomographic scans of 46 subjects less than 50 years of age were evaluated. Magnetic resonance imaging was used to determine disc degeneration, and computed tomography was used to measure facet joint angles and determine tropism. Subjects with tropism had a significantly higher prevalence of disc degeneration at all three lumbar levels examined (L3-4, L4-5, L5-S1). The average facet angles increased from L3-4 to L4-5 and further to the L5-S1 level. There was no statistically significant relationship between the magnitude of the angle and the presence of disc degeneration at any of the three levels. It was concluded that the risk of disc degeneration is increased in the presence of facet joint tropism.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

In this study, the contact loads and regions on facets of a lumbar motion segment are quantitatively determined. The analysis accounts for both material and geometric nonlinearities and treats the facet articulation as a frictionless, nonlinear, moving contact problem. The loadings consist of axial torque and lateral bending acting alone or in combination with axial compression force. Complex loadings simulating symmetric and nonsymmetric liftings are also considered. Under identical magnitude of rotation, axial torque generates the largest contact forces, followed by extension, flexion, and lateral bending. Contact forces under loads simulating heavy symmetric lifting are as large as, or even larger than, those under large extension and axial torque loadings. The presence of axial and lateral rotations during forward flexion significantly increases the loads transmitted through the compression facet. The tension facet, in this case, became nearly unloaded. The large loads on the facets, predicted especially under nonsymmetric, combined flexion loadings, are likely to play a role in the observed disorders of the facet joints. Under various loadings, the transfer of forces from one facet to the adjacent one occurs through three distinct areas, namely, extension-type, flexion-type, and torsion-type contact areas. The relative magnitude of different components of the transmitted forces are also predicted to vary considerably, depending on these regions of contact.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

A minority of industrial-back-sprain claimants account for most of the cost of industrial back sprain: those whose disability persists into “chronicity,” which is defined as 90 days or more off work. The data in this study demonstrate the effects of socioeconomic factors on chronicity. This analysis is based on State of Washington industrial insurance claims for back sprain. For both men and women, three socioeconomic factors significantly affect the risk of chronicity: age, wage, and the family status of being either widowed or divorced with no children. In addition, the Nam-Powers Socioeconomic Index is significant for men. Wage compensation ratio cannot be shown to be a factor in chronicity.

ISSN:0362-2436    

出版商:OVID    

年代:1991

数据来源: OVID