The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Dennis E. Anderson - One of the best experts on this subject based on the ideXlab platform.
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The rib cage stiffens the thoracic spine in a cadaveric model with body weight Load under dynamic moments.
Journal of The Mechanical Behavior of Biomedical Materials, 2018Co-Authors: Erin M. Mannen, Elizabeth A. Friis, Benjamin M. Wong, Hadley L. Sis, Eileen S. Cadel, Dennis E. AndersonAbstract:Abstract The thoracic spine presents a challenge for biomechanical testing. With more segments than the lumbar and cervical regions and the integration with the rib cage, experimental approaches to evaluate the mechanical behavior of cadaveric thoracic spines have varied widely. Some researchers are now including the rib cage intact during testing, and some are incorporating Follower Load techniques in the thoracic spine. Both of these approaches aim to more closely model physiological conditions. To date, no studies have examined the impact of the rib cage on thoracic spine motion and stiffness in conjunction with Follower Loads. The purpose of this research was to quantify the mechanical effect of the rib cage on cadaveric thoracic spine motion and stiffness with a Follower Load under dynamic moments. It was hypothesized that the rib cage would increase stiffness and decrease motion of the thoracic spine with a Follower Load. Eight fresh-frozen human cadaveric thoracic spines with rib cages (T1–T12) were Loaded with a 400 N compressive Follower Load. Dynamic moments of ± 5 N m were applied in lateral bending, flexion/extension, and axial rotation, and the motion and stiffness of the specimens with the rib cage intact have been previously reported. This study evaluated the motion and stiffness of the specimens after rib cage removal, and compared the data to the rib cage intact condition. Range-of-motion and stiffness were calculated for the upper, middle, and lower segments of the thoracic spine. Range-of-motion significantly increased with the removal of the rib cage in lateral bending, flexion/extension, and axial rotation by 63.5%, 63.0%, and 58.8%, respectively (p
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Effect of Follower Load on motion and stiffness of the human thoracic spine with intact rib cage.
Journal of Biomechanics, 2016Co-Authors: Hadley L. Sis, Erin M. Mannen, Dennis E. Anderson, Benjamin M. Wong, Eileen S. Cadel, Mary L. Bouxsein, Elizabeth A. FriisAbstract:Abstract Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive Follower preLoad. However, dynamic mechanical testing using both the rib cage and Follower Load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive Follower preLoads was performed. The objective was to characterize the motion and stiffness of the thoracic spine with intact rib cage and Follower preLoad. The hypotheses tested for all modes of bending were (i) range of motion, elastic zone, and neutral zone will be reduced with a Follower Load, and (ii) neutral and elastic zone stiffness will be increased with a Follower Load. Eight human cadaveric thoracic spine specimen (T1–T12) with intact rib cage were subjected to 5 Nm pure moments in lateral bending, flexion/extension, and axial rotation under Follower Loads of 0–400 N. Range of motion, elastic and neutral zones, and elastic and neutral zone stiffness values were calculated for functional spinal units and segments within the entire thoracic section. Combined segmental range of motion decreased by an average of 34% with Follower Load for every mode. Application of a Follower Load with intact rib cage impacts the motion and stiffness of the human cadaveric thoracic spine. Researchers should consider including both aspects to better represent the physiologic implications of human motion and improve clinically relevant biomechanical thoracic spine testing.
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effects of Follower Load and rib cage on intervertebral disc pressure and sagittal plane curvature in static tests of cadaveric thoracic spines
Journal of Biomechanics, 2016Co-Authors: Erin M. Mannen, Elizabeth A. Friis, Dennis E. Anderson, Hadley L. Sis, Eileen S. Cadel, Mary L. Bouxsein, Benjamin M WongAbstract:The clinical relevance of mechanical testing studies of cadaveric human thoracic spines could be enhanced by using Follower preLoad techniques, by including the intact rib cage, and by measuring thoracic intervertebral disc pressures, but studies to date have not incorporated all of these components simultaneously. Thus, this study aimed to implement a Follower preLoad in the thoracic spine with intact rib cage, and examine the effects of Follower Load, rib cage stiffening and rib cage removal on intervertebral disc pressures and sagittal plane curvatures in unconstrained static conditions. Intervertebral disc pressures increased linearly with Follower Load magnitude. The effect of the rib cage on disc pressures in static conditions remains unclear because testing order likely confounded the results. Disc pressures compared well with previous reports in vitro, and comparison with in vivo values suggests the use of a Follower Load of about 400N to approximate Loading in upright standing. Follower Load had no effect on sagittal plane spine curvature overall, suggesting successful application of the technique, although increased flexion in the upper spine and reduced flexion in the lower spine suggest that the Follower Load path was not optimized. Rib cage stiffening and removal both increased overall spine flexion slightly, although with differing effects at specific spinal locations. Overall, the approaches demonstrated here will support the use of Follower preLoads, intact rib cage, and disc pressure measurements to enhance the clinical relevance of future studies of the thoracic spine.
Hansjoachim Wilke - One of the best experts on this subject based on the ideXlab platform.
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the effect of Follower Load on the intersegmental coupled motion characteristics of the human thoracic spine an in vitro study using entire rib cage specimens
Journal of Biomechanics, 2018Co-Authors: Christian Liebsch, Nicolas Graf, Hansjoachim WilkeAbstract:Abstract The mechanical coupling behaviour of the thoracic spine is still not fully understood. For the validation of numerical models of the thoracic spine, however, the coupled motions within the single spinal segments are of importance to achieve high model accuracy. In the present study, eight fresh frozen human thoracic spinal specimens (C7-L1, mean age 54 ± 6 years) including the intact rib cage were Loaded with pure bending moments of 5 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) with and without a Follower Load of 400 N. During Loading, the relative motions of each vertebra were monitored. Follower Load decreased the overall ROM (T1-T12) significantly (p
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IN VITRO TESTING OF CADAVERIC SPECIMENS
Biomechanics of the Spine, 2018Co-Authors: Fabio Galbusera, David Volkheimer, Hansjoachim WilkeAbstract:Abstract In vitro testing is employed to investigate various aspects of the biomechanical response of spinal specimens as a whole as well as of its individual components and for the preclinical assessment of novel implants and surgical techniques. The golden standard for in vitro testing is to use fresh/fresh frozen human specimens; the suitability of embalmed and animal specimens should be checked with respect to the specific research question. A biomechanical investigation conducted on a spinal specimen should aim to replicate the complex Loading and constraint conditions acting in vivo, which are determined by the combination of gravity and the action of the trunk muscles. However, a simplified Loading environment, such as pure moments with or without a compressive Follower Load, is preferred in most cases because the exact Loads applied are not known. This chapter describes various test approaches that have been developed to simulate such Loading conditions, as well as other relevant aspects such as the measurement of the intradiscal pressure, the simulation of a repetitive Loading scenario such as the spinal Loads acting in daily activities, as well as the assessment of fluid exchange between the spine and the surrounding environment.
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influence of a Follower Load on intradiscal pressure and intersegmental rotation of the lumbar spine
Spine, 2001Co-Authors: A Rohlmann, S Neller, Lutz Claes, G Bergmann, Hansjoachim WilkeAbstract:STUDY DESIGN Intradiscal pressure and intersegmental rotation of human lumbar spines were measured in vitro. OBJECTIVES To determine the effect of a Follower Load on mechanical behavior at all levels of the lumbar spine. SUMMARY OF BACKGROUND DATA Different Loads have been proposed for studying the mechanical behavior of the lumbar spine. The influence of a Follower Load on intradiscal pressure at the different levels is unknown. METHODS Ten human cadaveric lumbar spines were Loaded in the three main anatomic planes with pure moments of 3.75, 7.5, and 7.5 Nm plus a Follower Load of 280 N. Intradiscal pressure and intersegmental rotation were measured at all levels. RESULTS An additional Follower Load increased the intradiscal pressure, slightly reduced the intersegmental rotation for axial rotation, and hardly affected intersegmental rotation for lateral bending and flexion-extension. CONCLUSIONS A superimposed Follower Load renders spinal Loading with pure moments more physiologic.
Heow Pueh Lee - One of the best experts on this subject based on the ideXlab platform.
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Damping effects on the dynamic stability of a rod subjected to intermediate Follower Loads
Computer Methods in Applied Mechanics and Engineering, 1996Co-Authors: Heow Pueh LeeAbstract:Abstract The equation of motion in matrix form of an Euler beam of uniform cross-section including the effect of internal damping subjected to an intermediate subtangential Follower Load is presented. The effect of slight damping on the critical Follower Load with respect to variation in the location of application of the Follower Load and the parameter for subtangentiality is examined for a specific example of a clamped-free rod. The modes of instability in the form of flutter or divergence without damping are found to be unaffected by the presence of slight damping although there may be a sharp decrease in the first critical Load for instability by flutter.
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Effects of damping on the dynamic stability of a rod with an intermediate spring support subjected to Follower forces
Computers & Structures, 1996Co-Authors: Heow Pueh LeeAbstract:The equation of motion in matrix form of an Euler beam, including the effect of internal damping subjected to non-conservative Follower forces, is formulated based on Lagrangian approach and the assumed mode method. The beam is assumed to rest on an intermediate spring support of large stiffness modeling a rigid support. The effect of slight damping on the jump phenomenon for the critical Follower Load with respect to variation in the support location is examined for a specific example of a simply supported-free rod. For some cases, the modes of instability in the form of flutter or divergence without damping are found to be unaffected by the presence of slight damping, although there may be a sharp decrease in the first critical Load for instability by flutter. However, for specific locations of the intermediate spring support, the presence of a small amount of damping may change the mode of instability from divergence to flutter with a sharp decrease in the critical Follower Load. An interesting finding is that this mode of instability by flutter only occurs for an isolated and narrow range of Follower Loads.
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divergence and flutter of a cantilever rod with an intermediate spring support
International Journal of Solids and Structures, 1995Co-Authors: Heow Pueh LeeAbstract:Abstract The equation of motion in matrix form of a cantilever Euler beam subject to a tipconcentrated Follower force at the free end is formulated based on the Lagrangian approach and the assumed mode method. The non-conservative nature of the system is identified by the non-symmetric matrix in the equation of motion. The beam is assumed to rest on an intermediate spring support. Jump phenomenon for the critical Follower Load is found to occur for both variations in the support location as well as the stiffness of the spring support. Detailed history of the changes in the Load-frequency diagram due to variation in the support location and the stiffness of the spring support is presented to explain the occurrence of the jump phenomenon. An interesting finding is that the rod is found to be extremely unstable for a certain combination of spring stiffness and support location for a cantilever rod.
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Dynamic stability of a rod with an intermediate spring support subject to subtangential Follower forces
Computer Methods in Applied Mechanics and Engineering, 1995Co-Authors: Heow Pueh LeeAbstract:Abstract The equation of motion in matrix form of an Euler beam subject to a tip-concentrated subtangential Follower force is formulated based on Lagrangian approach and the assumed mode method. The beam is assumed to rest on an intermediate spring support. The critical flutter Load is first computed for a simply supported-free rod on an intermediate spring support of large stiffness modeling a rigid support. Convergence of the smallest critical Load is found to be fast with just five terms for the assumed deflection function. Jump phenomenon for the critical Follower Load is found to occur for both variations in the support location, the stiffness of the spring support, as well as the parameter for subtangentiality. Detailed history of the changes in the Load-frequency curves due to variation in these parameters is presented to explain the occurrence of the jump phenomenon. In respect of changes in the parameter for subtangentiality for a rod on an intermediate spring support, it is found that the rod can undergo multiple transition from divergence to flutter, and then back to divergence when the subtangentiality changes from zero to unity.
Mary L. Bouxsein - One of the best experts on this subject based on the ideXlab platform.
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Effect of Follower Load on motion and stiffness of the human thoracic spine with intact rib cage.
Journal of Biomechanics, 2016Co-Authors: Hadley L. Sis, Erin M. Mannen, Dennis E. Anderson, Benjamin M. Wong, Eileen S. Cadel, Mary L. Bouxsein, Elizabeth A. FriisAbstract:Abstract Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive Follower preLoad. However, dynamic mechanical testing using both the rib cage and Follower Load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive Follower preLoads was performed. The objective was to characterize the motion and stiffness of the thoracic spine with intact rib cage and Follower preLoad. The hypotheses tested for all modes of bending were (i) range of motion, elastic zone, and neutral zone will be reduced with a Follower Load, and (ii) neutral and elastic zone stiffness will be increased with a Follower Load. Eight human cadaveric thoracic spine specimen (T1–T12) with intact rib cage were subjected to 5 Nm pure moments in lateral bending, flexion/extension, and axial rotation under Follower Loads of 0–400 N. Range of motion, elastic and neutral zones, and elastic and neutral zone stiffness values were calculated for functional spinal units and segments within the entire thoracic section. Combined segmental range of motion decreased by an average of 34% with Follower Load for every mode. Application of a Follower Load with intact rib cage impacts the motion and stiffness of the human cadaveric thoracic spine. Researchers should consider including both aspects to better represent the physiologic implications of human motion and improve clinically relevant biomechanical thoracic spine testing.
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effects of Follower Load and rib cage on intervertebral disc pressure and sagittal plane curvature in static tests of cadaveric thoracic spines
Journal of Biomechanics, 2016Co-Authors: Erin M. Mannen, Elizabeth A. Friis, Dennis E. Anderson, Hadley L. Sis, Eileen S. Cadel, Mary L. Bouxsein, Benjamin M WongAbstract:The clinical relevance of mechanical testing studies of cadaveric human thoracic spines could be enhanced by using Follower preLoad techniques, by including the intact rib cage, and by measuring thoracic intervertebral disc pressures, but studies to date have not incorporated all of these components simultaneously. Thus, this study aimed to implement a Follower preLoad in the thoracic spine with intact rib cage, and examine the effects of Follower Load, rib cage stiffening and rib cage removal on intervertebral disc pressures and sagittal plane curvatures in unconstrained static conditions. Intervertebral disc pressures increased linearly with Follower Load magnitude. The effect of the rib cage on disc pressures in static conditions remains unclear because testing order likely confounded the results. Disc pressures compared well with previous reports in vitro, and comparison with in vivo values suggests the use of a Follower Load of about 400N to approximate Loading in upright standing. Follower Load had no effect on sagittal plane spine curvature overall, suggesting successful application of the technique, although increased flexion in the upper spine and reduced flexion in the lower spine suggest that the Follower Load path was not optimized. Rib cage stiffening and removal both increased overall spine flexion slightly, although with differing effects at specific spinal locations. Overall, the approaches demonstrated here will support the use of Follower preLoads, intact rib cage, and disc pressure measurements to enhance the clinical relevance of future studies of the thoracic spine.
Elizabeth A. Friis - One of the best experts on this subject based on the ideXlab platform.
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The rib cage stiffens the thoracic spine in a cadaveric model with body weight Load under dynamic moments.
Journal of The Mechanical Behavior of Biomedical Materials, 2018Co-Authors: Erin M. Mannen, Elizabeth A. Friis, Benjamin M. Wong, Hadley L. Sis, Eileen S. Cadel, Dennis E. AndersonAbstract:Abstract The thoracic spine presents a challenge for biomechanical testing. With more segments than the lumbar and cervical regions and the integration with the rib cage, experimental approaches to evaluate the mechanical behavior of cadaveric thoracic spines have varied widely. Some researchers are now including the rib cage intact during testing, and some are incorporating Follower Load techniques in the thoracic spine. Both of these approaches aim to more closely model physiological conditions. To date, no studies have examined the impact of the rib cage on thoracic spine motion and stiffness in conjunction with Follower Loads. The purpose of this research was to quantify the mechanical effect of the rib cage on cadaveric thoracic spine motion and stiffness with a Follower Load under dynamic moments. It was hypothesized that the rib cage would increase stiffness and decrease motion of the thoracic spine with a Follower Load. Eight fresh-frozen human cadaveric thoracic spines with rib cages (T1–T12) were Loaded with a 400 N compressive Follower Load. Dynamic moments of ± 5 N m were applied in lateral bending, flexion/extension, and axial rotation, and the motion and stiffness of the specimens with the rib cage intact have been previously reported. This study evaluated the motion and stiffness of the specimens after rib cage removal, and compared the data to the rib cage intact condition. Range-of-motion and stiffness were calculated for the upper, middle, and lower segments of the thoracic spine. Range-of-motion significantly increased with the removal of the rib cage in lateral bending, flexion/extension, and axial rotation by 63.5%, 63.0%, and 58.8%, respectively (p
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Effect of Follower Load on motion and stiffness of the human thoracic spine with intact rib cage.
Journal of Biomechanics, 2016Co-Authors: Hadley L. Sis, Erin M. Mannen, Dennis E. Anderson, Benjamin M. Wong, Eileen S. Cadel, Mary L. Bouxsein, Elizabeth A. FriisAbstract:Abstract Researchers have reported on the importance of the rib cage in maintaining mechanical stability in the thoracic spine and on the validity of a compressive Follower preLoad. However, dynamic mechanical testing using both the rib cage and Follower Load has never been studied. An in vitro biomechanical study of human cadaveric thoracic specimens with rib cage intact in lateral bending, flexion/extension, and axial rotation under varying compressive Follower preLoads was performed. The objective was to characterize the motion and stiffness of the thoracic spine with intact rib cage and Follower preLoad. The hypotheses tested for all modes of bending were (i) range of motion, elastic zone, and neutral zone will be reduced with a Follower Load, and (ii) neutral and elastic zone stiffness will be increased with a Follower Load. Eight human cadaveric thoracic spine specimen (T1–T12) with intact rib cage were subjected to 5 Nm pure moments in lateral bending, flexion/extension, and axial rotation under Follower Loads of 0–400 N. Range of motion, elastic and neutral zones, and elastic and neutral zone stiffness values were calculated for functional spinal units and segments within the entire thoracic section. Combined segmental range of motion decreased by an average of 34% with Follower Load for every mode. Application of a Follower Load with intact rib cage impacts the motion and stiffness of the human cadaveric thoracic spine. Researchers should consider including both aspects to better represent the physiologic implications of human motion and improve clinically relevant biomechanical thoracic spine testing.
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effects of Follower Load and rib cage on intervertebral disc pressure and sagittal plane curvature in static tests of cadaveric thoracic spines
Journal of Biomechanics, 2016Co-Authors: Erin M. Mannen, Elizabeth A. Friis, Dennis E. Anderson, Hadley L. Sis, Eileen S. Cadel, Mary L. Bouxsein, Benjamin M WongAbstract:The clinical relevance of mechanical testing studies of cadaveric human thoracic spines could be enhanced by using Follower preLoad techniques, by including the intact rib cage, and by measuring thoracic intervertebral disc pressures, but studies to date have not incorporated all of these components simultaneously. Thus, this study aimed to implement a Follower preLoad in the thoracic spine with intact rib cage, and examine the effects of Follower Load, rib cage stiffening and rib cage removal on intervertebral disc pressures and sagittal plane curvatures in unconstrained static conditions. Intervertebral disc pressures increased linearly with Follower Load magnitude. The effect of the rib cage on disc pressures in static conditions remains unclear because testing order likely confounded the results. Disc pressures compared well with previous reports in vitro, and comparison with in vivo values suggests the use of a Follower Load of about 400N to approximate Loading in upright standing. Follower Load had no effect on sagittal plane spine curvature overall, suggesting successful application of the technique, although increased flexion in the upper spine and reduced flexion in the lower spine suggest that the Follower Load path was not optimized. Rib cage stiffening and removal both increased overall spine flexion slightly, although with differing effects at specific spinal locations. Overall, the approaches demonstrated here will support the use of Follower preLoads, intact rib cage, and disc pressure measurements to enhance the clinical relevance of future studies of the thoracic spine.