The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Hans-joachim Wilke - One of the best experts on this subject based on the ideXlab platform.
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In vitro comparison of personalized 3D printed versus standard expandable titanium vertebral body replacement implants in the mid-thoracic spine using entire rib cage specimens.
Clinical biomechanics (Bristol Avon), 2020Co-Authors: Christian Liebsch, Viktor Aleinikov, Talgat Kerimbayev, Serik Akshulakov, Tugrul Kocak, Morten Vogt, Jan Ulrich Jansen, Hans-joachim WilkeAbstract:Expandable titanium implants have proven their suitability as vertebral body replacement device in several clinical and biomechanical studies. Potential stabilizing features of personalized 3D printed titanium devices, however, have never been explored. This in vitro study aimed to prove their equivalence regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine including the entire rib cage. Six fresh frozen human thoracic spine specimens with Intact rib cages were loaded with pure moments of 5 Nm while performing optical motion tracking of all vertebrae. Following testing in Intact Condition (1), the specimens were tested after inserting personalized 3D printed titanium vertebral body replacement implants (2) and the two standard expandable titanium implants Obelisc™ (3) and Synex™ (4), each at T6 level combined with posterior pedicle screw-rod fixation from T4 to T8. No significant differences (P < .05) in primary and secondary T1-T12 ranges of motion were found between the three implant types. Compared to the Intact Condition, slight decreases of the range of motion were found, which were significant for Synex™ in primary flexion/extension (-17%), specifically at T3-T4 level (-46%), primary lateral bending (-18%), and secondary lateral bending during primary axial rotation (-53%). Range of motion solely increased at T8-T9 level, while being significant only for Obelisc™ (+35%). Personalized 3D printed vertebral body replacement implants provide a promising alternative to standard expandable devices regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine due to the stabilizing effect of the rib cage. Copyright © 2020. Published by Elsevier Ltd.
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Two-piece ALIF cage optimizes the bone–implant interface in a 360° setting
European Spine Journal, 2017Co-Authors: Hans-joachim Wilke, David Volkheimer, Bruce Robie, Finn B. ChristensenAbstract:Introduction Clinical research has documented that cage subsidence and the loss of balance correction is a significant complication related to spinal fusion. Subsidence is a multifactorial complication, where implant design is one important element. The aim of the study is to compare the rigidity and bone–implant relative motion of segments treated with either a conventional one-piece ALIF cage versus a two-piece ALIF cage, which adapts in situ and permits 7°–21° of lordosis. Methods Seven lumbosacral (L3-S1) human cadaver specimens were tested in a universal spine tester in the Intact Condition, the specimens instrumented with a two-piece ALIF cage (Statur^®-L, FBC Device, Denmark) and a one-piece ALIF cage (Pezo™-A, Ulrich GmbH & Co. KG., Germany), both supplemented with a pedicle screw system using pure moments of ±7.5 Nm in three principal motion directions. For assessment of the bone–implant interface, fluoroscopic videos were captured during motion and 3D motion was measured using an optical motion capturing system. Results Significantly less motion at the implant–endplate interface was found for the two-piece cage (1.0° ± 0.6°) in comparison to the one-piece cage (4.2° ± 1.7°) in flexion/extension. No significant differences in segment rigidity were found between the one-piece and two-piece cages in the 360° setup, while both configurations significantly reduced the range of motion compared to the Intact Condition ( p
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The rib cage stabilizes the human thoracic spine: An in vitro study using stepwise reduction of rib cage structures.
PLOS ONE, 2017Co-Authors: Christian Liebsch, Nicolas Graf, Konrad Appelt, Hans-joachim WilkeAbstract:: The stabilizing effect of the rib cage on the human thoracic spine is still not sufficiently analyzed. For a better understanding of this effect as well as the calibration and validation of numerical models of the thoracic spine, experimental biomechanics data is required. This study aimed to determine (1) the stabilizing effect of the single rib cage structures on the human thoracic spine as well as the effect of the rib cage on (2) the flexibility of the single motion segments and (3) coupled motion behavior of the thoracic spine. Six human thoracic spine specimens including the entire rib cage were loaded quasi-statically with pure moments of ± 2 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) using a custom-built spine tester. Motion analysis was performed using an optical motion tracking system during load application to determine range of motion (ROM) and neutral zone (NZ). Specimens were tested (1) in Intact Condition, (2) after removal of the intercostal muscles, (3) after median sternotomy, after removal of (4) the anterior rib cage up to the rib stumps, (5) the right sixth to eighth rib head, and (6) all rib heads. Significant (p < 0.05) increases of the ROM were found after dissecting the intercostal muscles (LB: + 22.4%, AR: + 22.6%), the anterior part of the rib cage (FE: + 21.1%, LB: + 10.9%, AR: + 72.5%), and all rib heads (AR: + 5.8%) relative to its previous Condition. Compared to the Intact Condition, ROM and NZ increased significantly after removing the anterior part of the rib cage (FE: + 52.2%, + 45.6%; LB: + 42.0%, + 54.0%; AR: + 94.4%, + 187.8%). Median sternotomy (FE: + 11.9%, AR: + 21.9%) and partial costovertebral release (AR: + 11.7%) significantly increased the ROM relative to its previous Condition. Removing the entire rib cage increased both monosegmental and coupled motion ROM, but did not alter the qualitative motion behavior. The rib cage has a strong effect on thoracic spine rigidity, especially in axial rotation by a factor of more than two, and should therefore be considered in clinical scenarios, in vitro, and in silico.
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EUROSPINE 2016 FULL PAPER AWARD: Wire cerclage can restore the stability of the thoracic spine after median sternotomy: an in vitro study with entire rib cage specimens
European Spine Journal, 2017Co-Authors: Christian Liebsch, Nicolas Graf, Hans-joachim WilkeAbstract:Purpose The influence of the anterior rib cage on the stability of the human thoracic spine is not completely known. One of the most common surgical interventions on the anterior rib cage is the longitudinal median sternotomy and its fixation by wire cerclage. Therefore, the purpose of this in vitro study was to examine, if wire cerclage can restore the stability of the human thoracic spine after longitudinal median sternotomy. Methods Six fresh frozen human thoracic spine specimens (C7–L1, 56 years in average, range 50–65), including the Intact rib cage without intercostal muscles, were tested in a spinal loading simulator and monitored with an optical motion tracking system. While applying 2 Nm pure moment in flexion/extension (FE), lateral bending (LB), and axial rotation (AR), the range of motion (ROM) and neutral zone (NZ) of the functional spinal units of the thoracic spine (T1–T12) were studied (1) in Intact Condition, (2) after longitudinal median sternotomy, and (3) after sternal closure using wire cerclage. Results The longitudinal median sternotomy caused a significant increase of the thoracic spine ROM relative to the Intact Condition (FE: 12° ± 5°, LB: 18° ± 5°, AR: 25° ± 10°) in FE (+12 %) and AR (+22 %). As a result, the sagittal cut faces of the sternum slipped apart visibly. Wire cerclage fixation resulted in a significant decrease of the ROM in AR (−12 %) relative to Condition after sternotomy. ROM increased relative to the Intact Condition, in AR even significantly (+8 %). The NZ showed a proportional behavior compared to the ROM in all loading planes, but it was distinctly higher in FE (72 %) and in LB (82 %) compared to the ROM than in AR (12 %). Conclusions In this in vitro study, the longitudinal median sternotomy resulted in a destabilization of the thoracic spine and relative motion of the sternal cut faces, which could be rectified by fixation with wire cerclage. However, the stability of the Intact Condition could not be reached. Nevertheless, a fixation of the sternum should be considered clinically to avoid instability of the spine and sternal pseudarthrosis.
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Two-piece ALIF cage optimizes the bone-implant interface in a 360° setting.
European Spine Journal, 2017Co-Authors: Hans-joachim Wilke, David Volkheimer, Bruce Robie, Finn B. ChristensenAbstract:Clinical research has documented that cage subsidence and the loss of balance correction is a significant complication related to spinal fusion. Subsidence is a multifactorial complication, where implant design is one important element. The aim of the study is to compare the rigidity and bone–implant relative motion of segments treated with either a conventional one-piece ALIF cage versus a two-piece ALIF cage, which adapts in situ and permits 7°–21° of lordosis. Seven lumbosacral (L3-S1) human cadaver specimens were tested in a universal spine tester in the Intact Condition, the specimens instrumented with a two-piece ALIF cage (Statur®-L, FBC Device, Denmark) and a one-piece ALIF cage (Pezo™-A, Ulrich GmbH & Co. KG., Germany), both supplemented with a pedicle screw system using pure moments of ±7.5 Nm in three principal motion directions. For assessment of the bone–implant interface, fluoroscopic videos were captured during motion and 3D motion was measured using an optical motion capturing system. Significantly less motion at the implant–endplate interface was found for the two-piece cage (1.0° ± 0.6°) in comparison to the one-piece cage (4.2° ± 1.7°) in flexion/extension. No significant differences in segment rigidity were found between the one-piece and two-piece cages in the 360° setup, while both configurations significantly reduced the range of motion compared to the Intact Condition (p
Christian Liebsch - One of the best experts on this subject based on the ideXlab platform.
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In vitro comparison of personalized 3D printed versus standard expandable titanium vertebral body replacement implants in the mid-thoracic spine using entire rib cage specimens.
Clinical biomechanics (Bristol Avon), 2020Co-Authors: Christian Liebsch, Viktor Aleinikov, Talgat Kerimbayev, Serik Akshulakov, Tugrul Kocak, Morten Vogt, Jan Ulrich Jansen, Hans-joachim WilkeAbstract:Expandable titanium implants have proven their suitability as vertebral body replacement device in several clinical and biomechanical studies. Potential stabilizing features of personalized 3D printed titanium devices, however, have never been explored. This in vitro study aimed to prove their equivalence regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine including the entire rib cage. Six fresh frozen human thoracic spine specimens with Intact rib cages were loaded with pure moments of 5 Nm while performing optical motion tracking of all vertebrae. Following testing in Intact Condition (1), the specimens were tested after inserting personalized 3D printed titanium vertebral body replacement implants (2) and the two standard expandable titanium implants Obelisc™ (3) and Synex™ (4), each at T6 level combined with posterior pedicle screw-rod fixation from T4 to T8. No significant differences (P < .05) in primary and secondary T1-T12 ranges of motion were found between the three implant types. Compared to the Intact Condition, slight decreases of the range of motion were found, which were significant for Synex™ in primary flexion/extension (-17%), specifically at T3-T4 level (-46%), primary lateral bending (-18%), and secondary lateral bending during primary axial rotation (-53%). Range of motion solely increased at T8-T9 level, while being significant only for Obelisc™ (+35%). Personalized 3D printed vertebral body replacement implants provide a promising alternative to standard expandable devices regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine due to the stabilizing effect of the rib cage. Copyright © 2020. Published by Elsevier Ltd.
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The rib cage stabilizes the human thoracic spine: An in vitro study using stepwise reduction of rib cage structures.
PLOS ONE, 2017Co-Authors: Christian Liebsch, Nicolas Graf, Konrad Appelt, Hans-joachim WilkeAbstract:: The stabilizing effect of the rib cage on the human thoracic spine is still not sufficiently analyzed. For a better understanding of this effect as well as the calibration and validation of numerical models of the thoracic spine, experimental biomechanics data is required. This study aimed to determine (1) the stabilizing effect of the single rib cage structures on the human thoracic spine as well as the effect of the rib cage on (2) the flexibility of the single motion segments and (3) coupled motion behavior of the thoracic spine. Six human thoracic spine specimens including the entire rib cage were loaded quasi-statically with pure moments of ± 2 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) using a custom-built spine tester. Motion analysis was performed using an optical motion tracking system during load application to determine range of motion (ROM) and neutral zone (NZ). Specimens were tested (1) in Intact Condition, (2) after removal of the intercostal muscles, (3) after median sternotomy, after removal of (4) the anterior rib cage up to the rib stumps, (5) the right sixth to eighth rib head, and (6) all rib heads. Significant (p < 0.05) increases of the ROM were found after dissecting the intercostal muscles (LB: + 22.4%, AR: + 22.6%), the anterior part of the rib cage (FE: + 21.1%, LB: + 10.9%, AR: + 72.5%), and all rib heads (AR: + 5.8%) relative to its previous Condition. Compared to the Intact Condition, ROM and NZ increased significantly after removing the anterior part of the rib cage (FE: + 52.2%, + 45.6%; LB: + 42.0%, + 54.0%; AR: + 94.4%, + 187.8%). Median sternotomy (FE: + 11.9%, AR: + 21.9%) and partial costovertebral release (AR: + 11.7%) significantly increased the ROM relative to its previous Condition. Removing the entire rib cage increased both monosegmental and coupled motion ROM, but did not alter the qualitative motion behavior. The rib cage has a strong effect on thoracic spine rigidity, especially in axial rotation by a factor of more than two, and should therefore be considered in clinical scenarios, in vitro, and in silico.
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EUROSPINE 2016 FULL PAPER AWARD: Wire cerclage can restore the stability of the thoracic spine after median sternotomy: an in vitro study with entire rib cage specimens
European Spine Journal, 2017Co-Authors: Christian Liebsch, Nicolas Graf, Hans-joachim WilkeAbstract:Purpose The influence of the anterior rib cage on the stability of the human thoracic spine is not completely known. One of the most common surgical interventions on the anterior rib cage is the longitudinal median sternotomy and its fixation by wire cerclage. Therefore, the purpose of this in vitro study was to examine, if wire cerclage can restore the stability of the human thoracic spine after longitudinal median sternotomy. Methods Six fresh frozen human thoracic spine specimens (C7–L1, 56 years in average, range 50–65), including the Intact rib cage without intercostal muscles, were tested in a spinal loading simulator and monitored with an optical motion tracking system. While applying 2 Nm pure moment in flexion/extension (FE), lateral bending (LB), and axial rotation (AR), the range of motion (ROM) and neutral zone (NZ) of the functional spinal units of the thoracic spine (T1–T12) were studied (1) in Intact Condition, (2) after longitudinal median sternotomy, and (3) after sternal closure using wire cerclage. Results The longitudinal median sternotomy caused a significant increase of the thoracic spine ROM relative to the Intact Condition (FE: 12° ± 5°, LB: 18° ± 5°, AR: 25° ± 10°) in FE (+12 %) and AR (+22 %). As a result, the sagittal cut faces of the sternum slipped apart visibly. Wire cerclage fixation resulted in a significant decrease of the ROM in AR (−12 %) relative to Condition after sternotomy. ROM increased relative to the Intact Condition, in AR even significantly (+8 %). The NZ showed a proportional behavior compared to the ROM in all loading planes, but it was distinctly higher in FE (72 %) and in LB (82 %) compared to the ROM than in AR (12 %). Conclusions In this in vitro study, the longitudinal median sternotomy resulted in a destabilization of the thoracic spine and relative motion of the sternal cut faces, which could be rectified by fixation with wire cerclage. However, the stability of the Intact Condition could not be reached. Nevertheless, a fixation of the sternum should be considered clinically to avoid instability of the spine and sternal pseudarthrosis.
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EUROSPINE 2016 FULL PAPER AWARD: Wire cerclage can restore the stability of the thoracic spine after median sternotomy: an in vitro study with entire rib cage specimens
European Spine Journal, 2016Co-Authors: Christian Liebsch, Nicolas Graf, Hans-joachim WilkeAbstract:The influence of the anterior rib cage on the stability of the human thoracic spine is not completely known. One of the most common surgical interventions on the anterior rib cage is the longitudinal median sternotomy and its fixation by wire cerclage. Therefore, the purpose of this in vitro study was to examine, if wire cerclage can restore the stability of the human thoracic spine after longitudinal median sternotomy. Six fresh frozen human thoracic spine specimens (C7–L1, 56 years in average, range 50–65), including the Intact rib cage without intercostal muscles, were tested in a spinal loading simulator and monitored with an optical motion tracking system. While applying 2 Nm pure moment in flexion/extension (FE), lateral bending (LB), and axial rotation (AR), the range of motion (ROM) and neutral zone (NZ) of the functional spinal units of the thoracic spine (T1–T12) were studied (1) in Intact Condition, (2) after longitudinal median sternotomy, and (3) after sternal closure using wire cerclage. The longitudinal median sternotomy caused a significant increase of the thoracic spine ROM relative to the Intact Condition (FE: 12° ± 5°, LB: 18° ± 5°, AR: 25° ± 10°) in FE (+12 %) and AR (+22 %). As a result, the sagittal cut faces of the sternum slipped apart visibly. Wire cerclage fixation resulted in a significant decrease of the ROM in AR (−12 %) relative to Condition after sternotomy. ROM increased relative to the Intact Condition, in AR even significantly (+8 %). The NZ showed a proportional behavior compared to the ROM in all loading planes, but it was distinctly higher in FE (72 %) and in LB (82 %) compared to the ROM than in AR (12 %). In this in vitro study, the longitudinal median sternotomy resulted in a destabilization of the thoracic spine and relative motion of the sternal cut faces, which could be rectified by fixation with wire cerclage. However, the stability of the Intact Condition could not be reached. Nevertheless, a fixation of the sternum should be considered clinically to avoid instability of the spine and sternal pseudarthrosis.
Jeonghwan Jang - One of the best experts on this subject based on the ideXlab platform.
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development and field application of a nonlinear ultrasonic modulation technique for fatigue crack detection without reference data from an Intact Condition
Smart Materials and Structures, 2016Co-Authors: Suyoung Yang, Hoon Sohn, Jeonghwan JangAbstract:In this study, a fatigue crack detection technique, which detects a fatigue crack without relying on any reference data obtained from the Intact Condition of a target structure, is developed using nonlinear ultrasonic modulation and applied to a real bridge structure. Using two wafer-type lead zirconate titanate (PZT) transducers, ultrasonic excitations at two distinctive frequencies are applied to a target inspection spot and the corresponding ultrasonic response is measured by another PZT transducer. Then, the nonlinear modulation components produced by a breathing-crack are extracted from the measured ultrasonic response, and a statistical classifier, which can determine if the nonlinear modulation components are statistically significant in comparison with the background noise level, is proposed. The effectiveness of the proposed fatigue crack detection technique is experimentally validated using the data obtained from aluminum plates and aircraft fitting-lug specimens under varying temperature and loading Conditions, and through a field testing of Yeongjong Grand Bridge in South Korea. The uniqueness of this study lies in that (1) detection of a micro fatigue crack with less than 1 μm width and fatigue cracks in the range of 10–20 μm in width using nonlinear ultrasonic modulation, (2) automated detection of fatigue crack formation without using reference data obtained from an Intact Condition, (3) reliable and robust diagnosis under varying temperature and loading Conditions, (4) application of a local fatigue crack detection technique to online monitoring of a real bridge.
Nicolas Graf - One of the best experts on this subject based on the ideXlab platform.
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The rib cage stabilizes the human thoracic spine: An in vitro study using stepwise reduction of rib cage structures.
PLOS ONE, 2017Co-Authors: Christian Liebsch, Nicolas Graf, Konrad Appelt, Hans-joachim WilkeAbstract:: The stabilizing effect of the rib cage on the human thoracic spine is still not sufficiently analyzed. For a better understanding of this effect as well as the calibration and validation of numerical models of the thoracic spine, experimental biomechanics data is required. This study aimed to determine (1) the stabilizing effect of the single rib cage structures on the human thoracic spine as well as the effect of the rib cage on (2) the flexibility of the single motion segments and (3) coupled motion behavior of the thoracic spine. Six human thoracic spine specimens including the entire rib cage were loaded quasi-statically with pure moments of ± 2 Nm in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) using a custom-built spine tester. Motion analysis was performed using an optical motion tracking system during load application to determine range of motion (ROM) and neutral zone (NZ). Specimens were tested (1) in Intact Condition, (2) after removal of the intercostal muscles, (3) after median sternotomy, after removal of (4) the anterior rib cage up to the rib stumps, (5) the right sixth to eighth rib head, and (6) all rib heads. Significant (p < 0.05) increases of the ROM were found after dissecting the intercostal muscles (LB: + 22.4%, AR: + 22.6%), the anterior part of the rib cage (FE: + 21.1%, LB: + 10.9%, AR: + 72.5%), and all rib heads (AR: + 5.8%) relative to its previous Condition. Compared to the Intact Condition, ROM and NZ increased significantly after removing the anterior part of the rib cage (FE: + 52.2%, + 45.6%; LB: + 42.0%, + 54.0%; AR: + 94.4%, + 187.8%). Median sternotomy (FE: + 11.9%, AR: + 21.9%) and partial costovertebral release (AR: + 11.7%) significantly increased the ROM relative to its previous Condition. Removing the entire rib cage increased both monosegmental and coupled motion ROM, but did not alter the qualitative motion behavior. The rib cage has a strong effect on thoracic spine rigidity, especially in axial rotation by a factor of more than two, and should therefore be considered in clinical scenarios, in vitro, and in silico.
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EUROSPINE 2016 FULL PAPER AWARD: Wire cerclage can restore the stability of the thoracic spine after median sternotomy: an in vitro study with entire rib cage specimens
European Spine Journal, 2017Co-Authors: Christian Liebsch, Nicolas Graf, Hans-joachim WilkeAbstract:Purpose The influence of the anterior rib cage on the stability of the human thoracic spine is not completely known. One of the most common surgical interventions on the anterior rib cage is the longitudinal median sternotomy and its fixation by wire cerclage. Therefore, the purpose of this in vitro study was to examine, if wire cerclage can restore the stability of the human thoracic spine after longitudinal median sternotomy. Methods Six fresh frozen human thoracic spine specimens (C7–L1, 56 years in average, range 50–65), including the Intact rib cage without intercostal muscles, were tested in a spinal loading simulator and monitored with an optical motion tracking system. While applying 2 Nm pure moment in flexion/extension (FE), lateral bending (LB), and axial rotation (AR), the range of motion (ROM) and neutral zone (NZ) of the functional spinal units of the thoracic spine (T1–T12) were studied (1) in Intact Condition, (2) after longitudinal median sternotomy, and (3) after sternal closure using wire cerclage. Results The longitudinal median sternotomy caused a significant increase of the thoracic spine ROM relative to the Intact Condition (FE: 12° ± 5°, LB: 18° ± 5°, AR: 25° ± 10°) in FE (+12 %) and AR (+22 %). As a result, the sagittal cut faces of the sternum slipped apart visibly. Wire cerclage fixation resulted in a significant decrease of the ROM in AR (−12 %) relative to Condition after sternotomy. ROM increased relative to the Intact Condition, in AR even significantly (+8 %). The NZ showed a proportional behavior compared to the ROM in all loading planes, but it was distinctly higher in FE (72 %) and in LB (82 %) compared to the ROM than in AR (12 %). Conclusions In this in vitro study, the longitudinal median sternotomy resulted in a destabilization of the thoracic spine and relative motion of the sternal cut faces, which could be rectified by fixation with wire cerclage. However, the stability of the Intact Condition could not be reached. Nevertheless, a fixation of the sternum should be considered clinically to avoid instability of the spine and sternal pseudarthrosis.
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EUROSPINE 2016 FULL PAPER AWARD: Wire cerclage can restore the stability of the thoracic spine after median sternotomy: an in vitro study with entire rib cage specimens
European Spine Journal, 2016Co-Authors: Christian Liebsch, Nicolas Graf, Hans-joachim WilkeAbstract:The influence of the anterior rib cage on the stability of the human thoracic spine is not completely known. One of the most common surgical interventions on the anterior rib cage is the longitudinal median sternotomy and its fixation by wire cerclage. Therefore, the purpose of this in vitro study was to examine, if wire cerclage can restore the stability of the human thoracic spine after longitudinal median sternotomy. Six fresh frozen human thoracic spine specimens (C7–L1, 56 years in average, range 50–65), including the Intact rib cage without intercostal muscles, were tested in a spinal loading simulator and monitored with an optical motion tracking system. While applying 2 Nm pure moment in flexion/extension (FE), lateral bending (LB), and axial rotation (AR), the range of motion (ROM) and neutral zone (NZ) of the functional spinal units of the thoracic spine (T1–T12) were studied (1) in Intact Condition, (2) after longitudinal median sternotomy, and (3) after sternal closure using wire cerclage. The longitudinal median sternotomy caused a significant increase of the thoracic spine ROM relative to the Intact Condition (FE: 12° ± 5°, LB: 18° ± 5°, AR: 25° ± 10°) in FE (+12 %) and AR (+22 %). As a result, the sagittal cut faces of the sternum slipped apart visibly. Wire cerclage fixation resulted in a significant decrease of the ROM in AR (−12 %) relative to Condition after sternotomy. ROM increased relative to the Intact Condition, in AR even significantly (+8 %). The NZ showed a proportional behavior compared to the ROM in all loading planes, but it was distinctly higher in FE (72 %) and in LB (82 %) compared to the ROM than in AR (12 %). In this in vitro study, the longitudinal median sternotomy resulted in a destabilization of the thoracic spine and relative motion of the sternal cut faces, which could be rectified by fixation with wire cerclage. However, the stability of the Intact Condition could not be reached. Nevertheless, a fixation of the sternum should be considered clinically to avoid instability of the spine and sternal pseudarthrosis.
Suyoung Yang - One of the best experts on this subject based on the ideXlab platform.
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development and field application of a nonlinear ultrasonic modulation technique for fatigue crack detection without reference data from an Intact Condition
Smart Materials and Structures, 2016Co-Authors: Suyoung Yang, Hoon Sohn, Jeonghwan JangAbstract:In this study, a fatigue crack detection technique, which detects a fatigue crack without relying on any reference data obtained from the Intact Condition of a target structure, is developed using nonlinear ultrasonic modulation and applied to a real bridge structure. Using two wafer-type lead zirconate titanate (PZT) transducers, ultrasonic excitations at two distinctive frequencies are applied to a target inspection spot and the corresponding ultrasonic response is measured by another PZT transducer. Then, the nonlinear modulation components produced by a breathing-crack are extracted from the measured ultrasonic response, and a statistical classifier, which can determine if the nonlinear modulation components are statistically significant in comparison with the background noise level, is proposed. The effectiveness of the proposed fatigue crack detection technique is experimentally validated using the data obtained from aluminum plates and aircraft fitting-lug specimens under varying temperature and loading Conditions, and through a field testing of Yeongjong Grand Bridge in South Korea. The uniqueness of this study lies in that (1) detection of a micro fatigue crack with less than 1 μm width and fatigue cracks in the range of 10–20 μm in width using nonlinear ultrasonic modulation, (2) automated detection of fatigue crack formation without using reference data obtained from an Intact Condition, (3) reliable and robust diagnosis under varying temperature and loading Conditions, (4) application of a local fatigue crack detection technique to online monitoring of a real bridge.