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Hans-joachim Wilke - One of the best experts on this subject based on the ideXlab platform.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

M Shariyat - One of the best experts on this subject based on the ideXlab platform.

  • dynamic buckling of suddenly Loaded imperfect hybrid fgm cylindrical shells with temperature dependent material properties under thermo electro mechanical Loads
    International Journal of Mechanical Sciences, 2008
    Co-Authors: M Shariyat
    Abstract:

    Abstract Only static buckling of the hybrid functionally graded material (FGM) cylindrical shells has been investigated so far. In the present paper, dynamic buckling of imperfect FGM cylindrical shells with integrated surface-bonded sensor and actuator layers subjected to some complex Combinations of thermo-electro-mechanical Loads is investigated. The general form of Green's strain tensor in curvilinear coordinates and a high-order shell theory proposed earlier by the author are used. The complicated nonlinear governing equations are solved using the finite-element method. Buckling Load is detected by a modified Budiansky's criterion proposed earlier by the author. Effects of temperature dependency of material properties, volume fraction index, Load Combination, and initial geometric imperfections on thermo-electro-mechanical post-buckling behavior are evaluated. Results reveal that the volume fraction index, temperature gradient, layer sequence, and the adaptive feedback control somewhat may affect the buckling Load.

  • dynamic thermal buckling of suddenly heated temperature dependent fgm cylindrical shells under combined axial compression and external pressure
    International Journal of Solids and Structures, 2008
    Co-Authors: M Shariyat
    Abstract:

    Abstract FGM components are constructed to sustain high temperature gradients. There are many applications where the FGM components are vulnerable to transient thermal shocks. If a component is already under compressive external Loads (e.g. under a Combination of axial compression and external pressure), the mentioned thermal shocks will cause the component to exhibit dynamic behavior and in some cases may lead to buckling. On the other hand, a preheated FGM component may undergo dynamic mechanical Loads. Only static thermal buckling investigations were developed so far for the FGM shells. In the present paper, dynamic buckling of a pre-stressed, suddenly heated imperfect FGM cylindrical shell and dynamic buckling of a mechanically Loaded imperfect FGM cylindrical shell in thermal environment, with temperature-dependent properties are presented. The general form of Green’s strain tensor in curvilinear coordinates and a high order shell theory proposed already by the author are used. Instead of using semi-analytical solutions that rely on the validity of the separation of variables concept, the complicated nonlinear governing equations are solved using the finite element method. Buckling Load is detected by a modified Budiansky criterion proposed by the author. The effects of temperature-dependency of the material properties, volume fraction index, Load Combination, and initial geometric imperfections on the thermo-mechanical post-buckling behavior of a shell with two constituent materials are evaluated. The results reveal that the volume fraction index and especially, the differences between the thermal stresses created in the outer and the inner surfaces may change the buckling behavior. Furthermore, temperature gradient and initial imperfections have less effect on buckling of a shell subjected to a pure external pressure.

Frank Heuer - One of the best experts on this subject based on the ideXlab platform.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

Hendrik Schmidt - One of the best experts on this subject based on the ideXlab platform.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

Laurence Claes - One of the best experts on this subject based on the ideXlab platform.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.

  • a new laser scanning technique for imaging intervertebral disc displacement and its application to modeling nucleotomy
    Clinical Biomechanics, 2008
    Co-Authors: Frank Heuer, Hendrik Schmidt, Laurence Claes, Hans-joachim Wilke
    Abstract:

    BACKGROUND: Nucleotomy is a standard procedure for treating disc prolapse. It can reduce intervertebral disc height, flattening and displacing the disc, which could lead to a painful narrowing of the foramina due to nerve root compression. The purpose of this study was to investigate the disc displacement of a complete spinal segment with and without nucleotomy. We hypothesized that a nucleotomy under a certain Load Combination might amplify disc displacement. METHODS: A laser scanner was developed for recording three-dimensional disc displacement of six Loaded L4-5 specimens for three conditions: intact, disc with vertebral bodies and subsequent nucleotomy. Specimens were exposed to pure moments of 7.5 N m in the three principal anatomical directions. Disc displacement was obtained at maximal deflection. A finite element model was validated and subsequently utilized to determine disc displacement. The task of the finite element model was to provide supplemental data for the posterolateral region, which could not be measured from intact specimens. FINDINGS: Disc displacement measurements of intact specimens were limited to the anterior part of discs, whereas the finite element model was able to provide the missing data of the dorsal disc region. The simulation of Load Combinations showed that the highest disc displacement was 1.9 mm at the lateral or posterolateral region. The nucleotomy increased the disc displacement up to 2.1mm, whereas the displacement zenith migrated posterolaterally. INTERPRETATION: These results could be a possible explanation for disadvantages of nucleotomy as a treatment. With the methodology presented here, we would be able to assess the performance of nucleus implants by determining the disc displacement map. This could also give us appropriate information of the annular deformation, which is needed for the development of motion preserving implants.