The Experts below are selected from a list of 67539 Experts worldwide ranked by ideXlab platform
Teruhisa Mihata - One of the best experts on this subject based on the ideXlab platform.
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a biomechanical cadaveric study comparing superior capsule reconstruction using fascia lata allograft with human dermal allograft for irreparable rotator cuff tear
Journal of Shoulder and Elbow Surgery, 2017Co-Authors: Teruhisa Mihata, Christopher N H Bui, Masaki Akeda, Matthew A Cavagnaro, Michael Kuenzler, Alexander B Peterson, Michelle H Mcgarry, Yasuo Itami, Orr Limpisvasti, Masashi NeoAbstract:Background Biomechanical and clinical success of the superior capsule reconstruction (SCR) using fascia lata (FL) grafts has been reported. In the United States, human dermal (HD) allograft has been used successfully for SCRs; however, the biomechanical characteristics have not been reported. Methods Eight cadaveric shoulders were tested in 5 conditions: (1) intact; (2) irreparable supraspinatus tear; (3) SCR using FL allograft with anterior and posterior suturing; (4) SCR using HD allograft with anterior and posterior suturing; and (5) SCR using HD allograft with posterior suturing. Rotational range of motion, superior translation, glenohumeral Joint Force, and subacromial contact were measured at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane. Graft dimensions before and after testing were also recorded. Biomechanical parameters were compared using a repeated-measures analysis of variance with Tukey post hoc test, and graft dimensions were compared using a Student t-test (P Results Irreparable supraspinatus tear significantly increased superior translation, superior glenohumeral Joint Force, and subacromial contact pressure, which were completely restored with the SCR FL allografts. Both SCR HD allograft repairs partially restored superior translation and completely restored subacromial contact and superior glenohumeral Joint Force. The HD allografts significantly elongated by 15% during testing, whereas the FL allograft lengths were unchanged. Conclusions Single-layered HD SCR allografts partially restored superior glenohumeral stability, whereas FL allograft SCR completely restored the superior glenohumeral stability. This may be due to the greater flexibility of the HD allograft, and the SCR procedure used was developed on the basis of FL grafts.
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superior capsule reconstruction to restore superior stability in irreparable rotator cuff tears a biomechanical cadaveric study
American Journal of Sports Medicine, 2012Co-Authors: Teruhisa Mihata, Michelle H Mcgarry, Joseph M Pirolo, Mitsuo Kinoshita, Thay Q LeeAbstract:Background:There have been many clinical reports of patch graft surgery for irreparable rotator cuff tears. However, the retear rate of the patch graft is relatively high because of the lack of superior stability, causing subacromial abrasions.Purpose:To compare superior stability among 3 types of patch grafting for simulated irreparable rotator cuff tears.Study Design:Controlled laboratory study.Methods:Eight cadaveric shoulders were tested in a custom shoulder testing system. Superior translation of the humerus, subacromial contact pressure, and glenohumeral Joint Force were quantified in the following 5 conditions: (1) when the rotator cuff was intact, (2) after cutting the supraspinatus tendon, (3) after the patch graft to reconstruct the supraspinatus tendon, (4) after the patch graft to reconstruct the superior capsule, and (5) after the patch graft to reconstruct both the supraspinatus tendon and superior capsule. While the graft was sutured to the torn tendon in condition 3, the graft was attached...
G Bergmann - One of the best experts on this subject based on the ideXlab platform.
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analysis of the influence of disc degeneration on the mechanical behaviour of a lumbar motion segment using the finite element method
Journal of Biomechanics, 2006Co-Authors: A Rohlmann, Thomas Zander, Hendrik Schmidt, Hansjoachim Wilke, G BergmannAbstract:Abstract Compared to a healthy intervertebral disc, the geometry and the material properties of the involved tissues are altered in a degenerated disc. It is not completely understood how this affects the mechanical behaviour of a motion segment. In order to study the influence of disc degeneration on motion segment mechanics a three-dimensional, nonlinear finite element model of the L3/L4 functional unit was used. Different grades of disc degeneration were simulated by varying disc height and bulk modulus of the nucleus pulposus. The model was loaded with pure moments of 10 N m in the three main anatomic planes. The finite element model predicted the same trends for intersegmental rotation and intradiscal pressure as described in the literature for in vitro studies. A comparison between calculated intersegmental rotation and experimental data showed a mean difference of 1.9° while the mean standard deviation was 2.5°. A mildly degenerated disc increases intersegmental rotation for all loading cases. With further increasing disc degeneration intersegmental rotation is decreased. For axial rotation the decrease takes place in the final stage. Intradiscal pressure is lower while facet Joint Force and maximum von Mises stress in the annulus are higher in a degenerated compared to a healthy disc.
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analysis of the influence of disc degeneration on the mechanical behaviour of a lumbar motion segment using the finite element method
Journal of Biomechanics, 2006Co-Authors: A Rohlmann, Thomas Zander, Hendrik Schmidt, Hansjoachim Wilke, G BergmannAbstract:Compared to a healthy intervertebral disc, the geometry and the material properties of the involved tissues are altered in a degenerated disc. It is not completely understood how this affects the mechanical behaviour of a motion segment. In order to study the influence of disc degeneration on motion segment mechanics a three-dimensional, nonlinear finite element model of the L3/L4 functional unit was used. Different grades of disc degeneration were simulated by varying disc height and bulk modulus of the nucleus pulposus. The model was loaded with pure moments of 10Nm in the three main anatomic planes. The finite element model predicted the same trends for intersegmental rotation and intradiscal pressure as described in the literature for in vitro studies. A comparison between calculated intersegmental rotation and experimental data showed a mean difference of 1.9 degrees while the mean standard deviation was 2.5 degrees . A mildly degenerated disc increases intersegmental rotation for all loading cases. With further increasing disc degeneration intersegmental rotation is decreased. For axial rotation the decrease takes place in the final stage. Intradiscal pressure is lower while facet Joint Force and maximum von Mises stress in the annulus are higher in a degenerated compared to a healthy disc.
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hip endoprosthesis for in vivo measurement of Joint Force and temperature
Journal of Biomechanics, 1999Co-Authors: F Graichen, G Bergmann, A RohlmannAbstract:Friction between the prosthetic head and acetabular cup increases the temperature in hip implants during activities like walking. A hip endoprosthesis was instrumented with sensors to measure the Joint contact Forces and the temperature distribution along the entire length of the titanium implant. Sensors and two inductively powered telemetry units are placed inside the hip implant and hermetically sealed against body fluids. Each telemetry unit contains an integrated 8-channel telemetry chip and a radio frequency transmitter. Force, temperature and power supply data are transmitted at different frequencies by two antennas to an external twin receiver. The inductive power supply is controlled by a personal computer. Force and temperature are monitored in real time and all data are stored on a video tape together with the patient's images. This paper describes the design and accuracy of the instrumented implant and the principal function of the external system components.
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influence of shoes and heel strike on the loading of the hip Joint
Journal of Biomechanics, 1995Co-Authors: G Bergmann, H Kniggendorf, F Graichen, A RohlmannAbstract:The Forces and moments acting at the hip Joint influence the long-term stability of the fixation of endoprostheses and the course of coxarthrosis. These loads may depend on the kind of footwear and the walking or running style. These factors were investigated in a patient with instrumented hip implants. He wore different sports shoes, normal leather shoes, hiking boots and clogs and walked barefoot with soft, normal and hard heel strikes. The loads were lowest while walking and jogging without shoes. All shoes increased the Joint Force and the bending moment at the implant slightly, but the torsional moment rose by up to 50%. No relation was found between the different type of shoes and the load increase, only shoes with very hard soles were clearly disadvantageous. Soft heels, soles or insoles did not offer advantages. Gait stability seems to play the most important role in increasing the Joint loading and should be the criterion for the choice of footwear. Smooth gait patterns with soft heel strikes are the only means to reduce Joint loading during slow jogging.
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evaluation of ischial weight bearing orthoses based on in vivo hip Joint Force measurements
Clinical Biomechanics, 1994Co-Authors: G Bergmann, A Rohlmann, Correa M Da Silva, G Neff, F GraichenAbstract:Abstract The reduction of hip Joint Forces by ischial weight-bearing orthoses, used for the treatment of Legg-Perthes and other Joint diseases, was measured in vivo in a patient with two instrumented endoprostheses. Three different types of orthoses reduced hip Joint loading by about 30%, independent of their cuff design and the position in which the femur was held. The direction of the Joint Forces was changed in such a way that the size of the load-carrying Joint areas decreased by up to 3.4% with two conventional orthoses. With the third model with improved containment of the femoral head this area increased by up to 8.2%. All the orthoses studied support the pelvis too close to the affected Joint, leading to insufficient load reduction. A design concept is proposed which prevents tilting of the pelvis in the frontal plane and may improve the Force reduction at the hip Joint.
A Rohlmann - One of the best experts on this subject based on the ideXlab platform.
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analysis of the influence of disc degeneration on the mechanical behaviour of a lumbar motion segment using the finite element method
Journal of Biomechanics, 2006Co-Authors: A Rohlmann, Thomas Zander, Hendrik Schmidt, Hansjoachim Wilke, G BergmannAbstract:Abstract Compared to a healthy intervertebral disc, the geometry and the material properties of the involved tissues are altered in a degenerated disc. It is not completely understood how this affects the mechanical behaviour of a motion segment. In order to study the influence of disc degeneration on motion segment mechanics a three-dimensional, nonlinear finite element model of the L3/L4 functional unit was used. Different grades of disc degeneration were simulated by varying disc height and bulk modulus of the nucleus pulposus. The model was loaded with pure moments of 10 N m in the three main anatomic planes. The finite element model predicted the same trends for intersegmental rotation and intradiscal pressure as described in the literature for in vitro studies. A comparison between calculated intersegmental rotation and experimental data showed a mean difference of 1.9° while the mean standard deviation was 2.5°. A mildly degenerated disc increases intersegmental rotation for all loading cases. With further increasing disc degeneration intersegmental rotation is decreased. For axial rotation the decrease takes place in the final stage. Intradiscal pressure is lower while facet Joint Force and maximum von Mises stress in the annulus are higher in a degenerated compared to a healthy disc.
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analysis of the influence of disc degeneration on the mechanical behaviour of a lumbar motion segment using the finite element method
Journal of Biomechanics, 2006Co-Authors: A Rohlmann, Thomas Zander, Hendrik Schmidt, Hansjoachim Wilke, G BergmannAbstract:Compared to a healthy intervertebral disc, the geometry and the material properties of the involved tissues are altered in a degenerated disc. It is not completely understood how this affects the mechanical behaviour of a motion segment. In order to study the influence of disc degeneration on motion segment mechanics a three-dimensional, nonlinear finite element model of the L3/L4 functional unit was used. Different grades of disc degeneration were simulated by varying disc height and bulk modulus of the nucleus pulposus. The model was loaded with pure moments of 10Nm in the three main anatomic planes. The finite element model predicted the same trends for intersegmental rotation and intradiscal pressure as described in the literature for in vitro studies. A comparison between calculated intersegmental rotation and experimental data showed a mean difference of 1.9 degrees while the mean standard deviation was 2.5 degrees . A mildly degenerated disc increases intersegmental rotation for all loading cases. With further increasing disc degeneration intersegmental rotation is decreased. For axial rotation the decrease takes place in the final stage. Intradiscal pressure is lower while facet Joint Force and maximum von Mises stress in the annulus are higher in a degenerated compared to a healthy disc.
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hip endoprosthesis for in vivo measurement of Joint Force and temperature
Journal of Biomechanics, 1999Co-Authors: F Graichen, G Bergmann, A RohlmannAbstract:Friction between the prosthetic head and acetabular cup increases the temperature in hip implants during activities like walking. A hip endoprosthesis was instrumented with sensors to measure the Joint contact Forces and the temperature distribution along the entire length of the titanium implant. Sensors and two inductively powered telemetry units are placed inside the hip implant and hermetically sealed against body fluids. Each telemetry unit contains an integrated 8-channel telemetry chip and a radio frequency transmitter. Force, temperature and power supply data are transmitted at different frequencies by two antennas to an external twin receiver. The inductive power supply is controlled by a personal computer. Force and temperature are monitored in real time and all data are stored on a video tape together with the patient's images. This paper describes the design and accuracy of the instrumented implant and the principal function of the external system components.
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influence of shoes and heel strike on the loading of the hip Joint
Journal of Biomechanics, 1995Co-Authors: G Bergmann, H Kniggendorf, F Graichen, A RohlmannAbstract:The Forces and moments acting at the hip Joint influence the long-term stability of the fixation of endoprostheses and the course of coxarthrosis. These loads may depend on the kind of footwear and the walking or running style. These factors were investigated in a patient with instrumented hip implants. He wore different sports shoes, normal leather shoes, hiking boots and clogs and walked barefoot with soft, normal and hard heel strikes. The loads were lowest while walking and jogging without shoes. All shoes increased the Joint Force and the bending moment at the implant slightly, but the torsional moment rose by up to 50%. No relation was found between the different type of shoes and the load increase, only shoes with very hard soles were clearly disadvantageous. Soft heels, soles or insoles did not offer advantages. Gait stability seems to play the most important role in increasing the Joint loading and should be the criterion for the choice of footwear. Smooth gait patterns with soft heel strikes are the only means to reduce Joint loading during slow jogging.
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evaluation of ischial weight bearing orthoses based on in vivo hip Joint Force measurements
Clinical Biomechanics, 1994Co-Authors: G Bergmann, A Rohlmann, Correa M Da Silva, G Neff, F GraichenAbstract:Abstract The reduction of hip Joint Forces by ischial weight-bearing orthoses, used for the treatment of Legg-Perthes and other Joint diseases, was measured in vivo in a patient with two instrumented endoprostheses. Three different types of orthoses reduced hip Joint loading by about 30%, independent of their cuff design and the position in which the femur was held. The direction of the Joint Forces was changed in such a way that the size of the load-carrying Joint areas decreased by up to 3.4% with two conventional orthoses. With the third model with improved containment of the femoral head this area increased by up to 8.2%. All the orthoses studied support the pelvis too close to the affected Joint, leading to insufficient load reduction. A design concept is proposed which prevents tilting of the pelvis in the frontal plane and may improve the Force reduction at the hip Joint.
Pierre Olivier Vandanjon - One of the best experts on this subject based on the ideXlab platform.
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A new closed-loop output error method for parameter identification of robot dynamics
IEEE Transactions on Control Systems Technology, 2013Co-Authors: Maxime Gautier, Alexandre Janot, Pierre Olivier VandanjonAbstract:Off-line robot dynamic identification methods are mostly based on the use of the inverse dynamic model, which is linear with respect to the dynamic parameters. This model is sampled while the robot is tracking reference trajectories that excite the system dynamics. This allows using linear least-squares techniques to estimate the parameters. The efficiency of this method has been proved through the experimental identification of many prototypes and industrial robots. However, this method requires the Joint Force/torque and position measurements and the estimate of the Joint velocity and acceleration, through the bandpass filtering of the Joint position at high sampling rates. The proposed new method requires only the Joint Force/torque measurement. It is a closed-loop output error method where the usual Joint position output is replaced by the Joint Force/torque. It is based on a closed-loop simulation of the robot using the direct dynamic model, the same structure of the control law, and the same reference trajectory for both the actual and the simulated robot. The optimal parameters minimize the 2-norm of the error between the actual Force/torque and the simulated Force/torque. This is a non-linear least-squares problem which is dramatically simplified using the inverse dynamic model to obtain an analytical expression of the simulated Force/torque, linear in the parameters. A validation experiment on a 2 degree-of-freedom direct drive robot shows that the new method is efficient.
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a new closed loop output error method for parameter identification of robot dynamics
IEEE Transactions on Control Systems and Technology, 2013Co-Authors: Maxime Gautier, Alexandre Janot, Pierre Olivier VandanjonAbstract:Offline robot dynamic identification methods are mostly based on the use of the inverse dynamic model, which is linear with respect to the dynamic parameters. This model is sampled while the robot is tracking reference trajectories that excite the system dynamics. This allows using linear least-squares techniques to estimate the parameters. The efficiency of this method has been proved through the experimental identification of many prototypes and industrial robots. However, this method requires the Joint Force/torque and position measurements and the estimate of the Joint velocity and acceleration, through the bandpass filtering of the Joint position at high sampling rates. The proposed new method called DIDIM requires only the Joint Force/torque measurement, which avoids the calculation of the velocity and acceleration by bandpass filtering of the measured position. It is a closed-loop output error method where the usual Joint position output is replaced by the Joint Force/torque. It is based on a closed-loop simulation of the robot using the direct dynamic model, the same structure of the control law, and the same reference trajectory for both the actual and the simulated robot. The optimal parameters minimize the 2-norm of the error between the actual Force/torque and the simulated Force/torque. This is a nonlinear least-squares problem which is dramatically simplified using the inverse dynamic model to obtain an analytical expression of the simulated Force/torque, linear in the parameters. A validation experiment on a two degree-of-freedom direct drive rigid robot shows that the new method is efficient.
David C Ackland - One of the best experts on this subject based on the ideXlab platform.
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Modulation of shoulder muscle and Joint function using a powered upper-limb exoskeleton.
Journal of biomechanics, 2018Co-Authors: Justin Fong, Vincent Crocher, Peter Vee Sin Lee, Denny Oetomo, Ying Tan, David C AcklandAbstract:Abstract Robotic-assistive exoskeletons can enable frequent repetitive movements without the presence of a full-time therapist; however, human-machine interaction and the capacity of powered exoskeletons to attenuate shoulder muscle and Joint loading is poorly understood. This study aimed to quantify shoulder muscle and Joint Force during assisted activities of daily living using a powered robotic upper limb exoskeleton (ArmeoPower, Hocoma). Six healthy male subjects performed abduction, flexion, horizontal flexion, reaching and nose touching activities. These tasks were repeated under two conditions: (i) the exoskeleton compensating only for its own weight, and (ii) the exoskeleton providing full upper limb gravity compensation (i.e., weightlessness). Muscle EMG, Joint kinematics and Joint torques were simultaneously recorded, and shoulder muscle and Joint Forces calculated using personalized musculoskeletal models of each subject’s upper limb. The exoskeleton reduced peak Joint torques, muscle Forces and Joint loading by up to 74.8% (0.113 Nm/kg), 88.8% (5.8%BW) and 68.4% (75.6%BW), respectively, with the degree of load attenuation strongly task dependent. The peak compressive, anterior and superior glenohumeral Joint Force during assisted nose touching was 36.4% (24.6%BW), 72.4% (13.1%BW) and 85.0% (17.2%BW) lower than that during unassisted nose touching, respectively. The present study showed that upper limb weight compensation using an assistive exoskeleton may increase glenohumeral Joint stability, since deltoid muscle Force, which is the primary contributor to superior glenohumeral Joint shear, is attenuated; however, prominent exoskeleton interaction moments are required to position and control the upper limb in space, even under full gravity compensation conditions. The modeling framework and results may be useful in planning targeted upper limb robotic rehabilitation tasks.
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muscle and Joint contact loading at the glenohumeral Joint after reverse total shoulder arthroplasty
Journal of Orthopaedic Research, 2011Co-Authors: David C Ackland, Sasha Roshanzamir, Martin Richardson, Marcus G PandyAbstract:The purposes of this study were to determine the contributions of each shoulder muscle to glenohumeral Joint Force during abduction and flexion in both the anatomical and post-operative shoulder and to identify factors that may contribute to the incidence of glenoid component loosening/failure and Joint instability in the shoulder after reverse shoulder arthroplasty (RSA). Eight cadaveric upper extremities were mounted onto a testing apparatus. Muscle lines of action were measured, and muscle Forces and muscle contributions to glenohumeral Joint Forces were determined during abduction and flexion of the pre-operative anatomical shoulder and of the shoulder after arthroplasty. Muscle Forces in the middle deltoid during abduction and those in the middle and anterior deltoid during flexion were significantly lower in the reverse shoulder than the pre-operative shoulder (p < 0.017). The resultant glenohumeral Joint Force in the reverse shoulder was significantly lower than that in the pre-operative shoulder; however, the superior shear Force acting at the glenohumeral Joint was significantly higher (p < 0.001). Reverse total shoulder arthroplasty reduces muscle effort in performing lifting and pushing tasks; however, reduced Joint compressive Force has the potential to compromise Joint stability, while an increased superior Joint shear Force may contribute to component loosening/failure. Because greater superior shear Force is generated in flexion than in abduction, care should be taken to avoid excessive shoulder loading in this plane of elevation. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1850–1858, 2011
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muscle and Joint contact loading at the glenohumeral Joint after reverse total shoulder arthroplasty
Journal of Orthopaedic Research, 2011Co-Authors: David C Ackland, Sasha Roshanzamir, Martin Richardson, Marcus G PandyAbstract:The purposes of this study were to determine the contributions of each shoulder muscle to glenohumeral Joint Force during abduction and flexion in both the anatomical and post-operative shoulder and to identify factors that may contribute to the incidence of glenoid component loosening/failure and Joint instability in the shoulder after reverse shoulder arthroplasty (RSA). Eight cadaveric upper extremities were mounted onto a testing apparatus. Muscle lines of action were measured, and muscle Forces and muscle contributions to glenohumeral Joint Forces were determined during abduction and flexion of the pre-operative anatomical shoulder and of the shoulder after arthroplasty. Muscle Forces in the middle deltoid during abduction and those in the middle and anterior deltoid during flexion were significantly lower in the reverse shoulder than the pre-operative shoulder (p < 0.017). The resultant glenohumeral Joint Force in the reverse shoulder was significantly lower than that in the pre-operative shoulder; however, the superior shear Force acting at the glenohumeral Joint was significantly higher (p < 0.001). Reverse total shoulder arthroplasty reduces muscle effort in performing lifting and pushing tasks; however, reduced Joint compressive Force has the potential to compromise Joint stability, while an increased superior Joint shear Force may contribute to component loosening/failure. Because greater superior shear Force is generated in flexion than in abduction, care should be taken to avoid excessive shoulder loading in this plane of elevation.
