1,881 research outputs found
Asymptomatic stenosis in the cervical and thoracic spines of patients with symptomatic lumbar stenosis
Study DesignâRetrospective study. ObjectiveâStudies on age-related degenerative changes causing concurrent stenoses in the cervical, thoracic, and lumbar spines (triple stenosis) are rare in the literature. Our objectives were to determine: (1) the incidence of asymptomatic radiologic cervical and thoracic stenosis in elderly patients with symptomatic lumbar stenosis, (2) the incidence of concurrent radiologic spinal stenosis in the cervical and thoracic spines, and (3) the radiologic features of cervical stenosis that might predict concurrent thoracic stenosis. MethodsâWhole-spine T2 sagittal magnetic resonance images of patients older than 80 and diagnosed with lumbar spinal stenosis between January 2003 and January 2012 were evaluated retrospectively. We included patients with asymptomatic spondylotic cervical and thoracic stenosis. We measured the anteroposterior diameters of the vertebral body, bony spinal canal, and spinal cord, along with the Pavlov ratio and anterior or posterior epidural stenosis at the level of the disk for each cervical and thoracic level. We compared the radiologic parameters between the subgroups of cervical stenosis with and without thoracic stenosis. ResultsâAmong the 460 patients with lumbar stenosis, 110 (23.9%) had concurrent radiologic cervical stenosis and 112 (24.3%) had concurrent radiologic thoracic stenosis. Fifty-six patients (12.1%) had combined radiologic cervical and thoracic stenosis in addition to their symptomatic lumbar stenosis (triple stenosis). Anterior epidural stenosis at C7âT1 was associated with a high prevalence of thoracic stenosis. ConclusionsâIt appears that asymptomatic radiologic cervical and thoracic stenosis is common in elderly patients with symptomatic lumbar stenosis
Surgical anatomy of the uncinate process and transverse foramen determined by computer tomography
Study DesignâComputed tomographyâbased cohort study. ObjectiveâAlthough there are publications concerning the relationship between the vertebral artery and uncinate process, there is no practical guide detailing the dimensions of this region to use during decompression of the intervertebral foramen. The purpose of this study is to determine the anatomic parameters that can be used as a guide for thorough decompression of the intervertebral foramen. MethodsâFifty-one patients with three-dimensional computed tomography scans of the cervical spine from 2003 to 2012 were included. On axial views, we measured the distance from the midline to the medial and lateral cortices of the pedicle bilaterally from C3 to C7. On coronal reconstructed views, we measured the minimum height of the uncinate process from the cranial cortex of the pedicle adjacent to the posterior cortex of vertebral body and the maximal height of the uncinate process from the cranial cortex of the pedicle at the midportion of the vertebral body bilaterally from C3 to C7. ResultsâThe mean distances from midline to the medial and lateral cortices of the pedicle were 10.1â±â1.3âmm and 13.9â±â1.5âmm, respectively. The mean minimum height of the uncinate process from the cranial cortex of the pedicle was 4.6â±â1.6âmm and the mean maximal height was 6.1â±â1.7 mm. ConclusionsâOur results suggest that in most cases, one can thoroughly decompress the intervertebral foramen by removing the uncinate out to 13âmm laterally from the midline and 4âmm above the pedicle without violating the transverse foramen
One-dimensional broadband phononic crystal filter with unit cells made of two non-uniform impedance-mirrored elements
A one-dimensional finite-sized phononic crystal(PC) made of a specially-configured unit cell is proposed to realize broad bandpass, high-performance filtering. The unit cell is specially-configured with two elements having mirrored impedance distributions of each other. One element has a non-uniform impedance distribution that is so engineered as to maximize wave transmission in the pass band and to minimize transmission in the adjacent stop band while the other, exactly the mirrored distribution. The mirroring approach naturally yields the overall impedance contrast within the resulting unit cell, necessary to form stop bands in a PC of the unit cells. More importantly, the good transmission performance of the orginally-engineered element can be preserved by the approach because no additional impedance mismatch is introduced along the interface of the two impedance-mirrored elements. Extraordinary performance of the PC filter made of the proposed unit cell, such as high transmission, large bandwidth and sharp roll-off, is demonstrated by using one-dimensional longitudinal elastic wave problems. Copyright 2013 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4790638ope
Zero-frequency Bragg gap by spin-harnessed metamaterial
The Bragg gap that stops wave propagation may not be formed from zero or a very low frequency unless the periodicity of a periodic system is unrealistically large. Accordingly, the Bragg gap has been considered to be inappropriate for low frequency applications despite its broad bandwidth. Here, we report a new mechanism that allows formation of the Bragg gap starting from a nearly zero frequency. The mechanism is based on the finding that if additional spin motion is coupled with the longitudinal motion of a mass of a diatomic mechanical periodic system, the Bragg gap starting from a nearly zero frequency can be formed. The theoretical analysis shows that the effective mass and stiffness at the band gap frequencies are all positive, confirming that the formed stop band is a Bragg gap. The periodic system is realized by a spin-harnessed metamaterial which incorporates unique linkage mechanisms. The numerical and experimental validation confirmed the formation of the low-frequency Bragg gap. The zero-frequency Bragg gap is expected to open a new way to control hard-to-shield low-frequency vibration and noise
Age-related changes in cervical sagittal range of motion and alignment
Study DesignâRetrospective cohort study. ObjectiveâTo compare sagittal cervical range of motion (ROM) and alignment in young versus middle-aged adults. MethodsâOne hundred four asymptomatic adults were selected randomly out of 791 subjects who underwent lateral cervical radiographs in neutral, flexion, and extension positions. They were divided into two groups: young (age 20 to 29, 52 people) and middle-aged adults (age 50 to 59, 52 people). We determined the ROMs of upper cervical (occipitalâC2 angle), midcervical (C2âC7 angle), and cervicothoracic spine (cervicosternal angle). We compared the alignment differences of the two groups by calculating the distances between C2 and C7 plumb lines, and C2 central-offset distance. ResultsâIn neutral position, there was no significant difference between young and middle-aged adults. However, in flexion, C2âC7 angle, distance between C2âC7 plumb lines, and C2 central-offset distance decreased with age. In extension, C2âC7 angle and C2 central-offset distance decreased with age. During flexion and extension, midcervical ROM and the range of C2 central-offset distance decreased in the middle-aged group. However, there was no difference between the two age groups in the ROM of the upper cervical and the cervicothoracic regions during flexion and extension. ConclusionâWe found that, despite of the presence of age-related cervical alignment changes, the only difference between the two groups was in the sagittal ROM of the midcervical spine during flexion and extension. Only the ROM of the midcervical spine appears to change significantly, consistent with findings that these levels are most likely to develop both symptomatic and asymptomatic degenerative changes
Radiographic comparison between cervical spine lateral and whole-spine lateral standing radiographs
Study DesignâRetrospective radiologic study. ObjectiveâThe sagittal alignment of the cervical spine can be evaluated using either a lateral cervical radiograph or a whole-spine lateral view on which the cervical spine is included. To our knowledge, however, no report has compared the two. The purpose of this work is to identify the difference in radiographic parameters between the cervical spine lateral view and the whole-spine lateral view. MethodsâWe retrospectively analyzed 59 adult patients suffering from neck pain with cervical spine lateral radiographs and whole-spine lateral radiographs from November 2007 to December 2011. The radiographs were measured using standard techniques to obtain the following parameters from the two different radiographs: occipitalâC2 angle, C2âC7 angle, C7âsternal angle, sternal slope, T1 slope, C2 central offset distance, the distance between C2 and C7 plumb lines, C4 anteroposterior (AP) diameter, the ratio of C2 central off distance to C4 AP diameter, the ratio of plumb lines' distance to C4 AP diameter. ResultsâWe found that the occipitalâC2 angle, sternal slope, and C4 AP diameter were similar, but the C2âC7 angle, C7âsternal angle, T1 slope, C2 central offset distance, distance between C2 and C7 plumb lines, ratio of C2 central off distance to C4 AP diameter, and ratio of plumb lines' distance to C4 AP diameter were different. However, the error of measurement was greater than the small angular and linear differences between the two views. ConclusionsâMost numerical values of the measured radiographic parameters appear to be different between the two views. However, the two views are comparable because the numerical differences were smaller than the errors of measurement
Delayed surgical intervention in central cord syndrome with cervical stenosis
Study DesignâReview of the literature. ObjectiveâIt is generally accepted that surgical treatment is necessary for central cord syndrome (CCS) with an underlying cervical stenosis. However, the surgical timing for decompression is controversial in spondylotic cervical CCS. The purpose of this study is to review the results of early and delayed surgery in patients with spondylotic cervical CCS. MethodsâMEDLINE was searched for English-language articles on CCS. There were 1,653 articles from 1940 to 2012 regarding CCS, 5 of which dealt with the timing of surgery for spondylotic cervical CCS. ResultsâAll five reports regarding the surgical timing of spondylotic cervical CCS were retrospective. Motor improvement, functional independence measures, and walking ability showed similar improvement in early and late surgery groups in the studies with follow-up longer than 1 year. However, greater improvement was seen in the early surgery group in the studies with follow-up shorter than 1 year. The complication rates did not show a difference between the early and late surgery groups. However, there are controversies regarding the length of intensive care unit stay or hospital stay for the two groups. ConclusionsâThere was no difference in motor improvement, functional independence, walking ability, and complication rates between early and late surgery for spondylotic cervical CCS
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