The Experts below are selected from a list of 345 Experts worldwide ranked by ideXlab platform
Andrew A. Amis - One of the best experts on this subject based on the ideXlab platform.
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The Ability of Medial Patellofemoral Ligament Reconstruction to Correct Patellar Kinematics and Contact Mechanics in the Presence of a Lateralized Tibial Tubercle
The American journal of sports medicine, 2015Co-Authors: Joanna M. Stephen, Andy Williams, Punyawan Lumpaopong, Alexander L Dodds, Deiary F. Kader, Andrew A. AmisAbstract:Background:Tibial tubercle (TT) transfer and medial patellofemoral ligament (MPFL) reconstruction are used after patellar dislocations. However, there is no objective evidence to guide surgical decision making, such as the ability of MPFL reconstruction to restore normal behavior in the presence of a lateralized TT.Hypothesis:MPFL reconstruction will only restore joint contact mechanics and patellar kinematics for TT–trochlear groove (TG) distances up to an identifiable limit.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees (mean TT-TG distance, 10.4 mm) were placed on a Testing Rig. Individual quadriceps heads and the iliotibial band were loaded with 205 N in physiological directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film and an optical tracking system. The MPFL attachments were marked. TT osteotomy was performed, and a metal T-plate ...
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the capsular ligaments provide more hip rotational restraint than the acetabular labrum and the ligamentum teres an experimental study
Journal of Bone and Joint Surgery-british Volume, 2015Co-Authors: R Van Arkel, Andrew A. Amis, J Cobb, Jonathan R T JeffersAbstract:In this in vitro study of the hip joint we examined which soft tissues act as primary and secondary passive rotational restraints when the hip joint is functionally loaded. A total of nine cadaveric left hips were mounted in a Testing Rig that allowed the application of forces, torques and rotations in all six degrees of freedom. The hip was rotated throughout a complete range of movement (ROM) and the contributions of the iliofemoral (medial and lateral arms), pubofemoral and ischiofemoral ligaments and the ligamentum teres to rotational restraint was determined by resecting a ligament and measuring the reduced torque required to achieve the same angular position as before resection. The contribution from the acetabular labrum was also measured. Each of the capsular ligaments acted as the primary hip rotation restraint somewhere within the complete ROM, and the ligamentum teres acted as a secondary restraint in high flexion, adduction and external rotation. The iliofemoral lateral arm and the ischiofemoral ligaments were primary restraints in two-thirds of the positions tested. Appreciation of the importance of these structures in preventing excessive hip rotation and subsequent impingement/instability may be relevant for surgeons undertaking both hip joint preserving surgery and hip arthroplasty.
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the effect of tibial tuberosity medialization and lateralization on patellofemoral joint kinematics contact mechanics and stability
American Journal of Sports Medicine, 2015Co-Authors: Joanna M. Stephen, Andy Williams, Punyawan Lumpaopong, Alexander L Dodds, Andrew A. AmisAbstract:Background:Tibial tuberosity (TT) transfer is a common procedure to treat patellofemoral instability in patients with elevated TT–trochlear groove (TG) distances. However, the effects of TT lateralization or medialization on patellar stability, kinematics, and contact mechanics remain unclear.Hypothesis:Progressive medialization and lateralization will have increasingly adverse effects on patellofemoral joint kinematics, contact mechanics, and stability.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees were placed on a Testing Rig, with a fixed femur and tibia mobile through 90° of flexion. Individual quadriceps heads and the iliotibial band were separated and loaded with 205 N in anatomic directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film behind the patella and an optical tracking system. The intact knee was measured with and without a ...
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the effect of femoral tunnel position and graft tension on patellar contact mechanics and kinematics after medial patellofemoral ligament reconstruction
American Journal of Sports Medicine, 2014Co-Authors: Joanna M. Stephen, Punyawan Lumpaopong, Deiary Kaider, David J Deehan, Andrew A. AmisAbstract:Background:An incorrect femoral tunnel position or inappropriate graft tensioning during medial patellofemoral ligament (MPFL) reconstruction may cause altered patellofemoral joint kinematics and contact mechanics, potentially resulting in pain and joint degeneration.Hypothesis:Nonanatomic positioning of the tunnel or graft overtensioning during MPFL reconstruction will have an adverse effect on patellar tracking and patellofemoral joint contact mechanics.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees were placed on a customized Testing Rig, with the femur fixed and the tibia mobile through 90° of flexion. Individual heads of the quadriceps muscle and the iliotibial band were separated and loaded with 205 N in anatomic directions using a system of cables and weights. Patellofemoral contact pressures and patellar tracking were measured through the flexion range at 10° intervals using Tekscan pressure-sensitive film inserted between the patella and trochlea and an optica...
M G Gee - One of the best experts on this subject based on the ideXlab platform.
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effects of microstructure on the thermo mechanical fatigue response of hardmetals using a new miniaturized Testing Rig
International Journal of Refractory Metals & Hard Materials, 1999Co-Authors: F C Dary, B Roebuck, M G GeeAbstract:Abstract High thermo-mechanical fatigue (TMF) resistance is essential for hardmetal materials used for milling, interrupted-cutting or even mining and construction applications. The National Physical Laboratory has developed a miniaturized electrothermo-mechanical test Rig which offers considerable potential over conventional Testing frames for thermo-mechanical Testing of hardmetals. The present study has investigated the effects of microstructural parameters on the thermo-mechanical fatigue behavior of WC–Co hardmetals. Clearly identifiable trends were observed as each microstructural features were changed. Regardless of the temperature/loading scheme used, the fatigue resistance was found to increase when the Co mean free path, WC grain size, cobalt content or carbon content were decreased, or when the solid solution cubic content was increased. Incidentally, the Rig potential both in terms of discrimination capacity when Testing parameters or microstructural features are changed, and in terms of degree of reproducibility between repeated tests were explored. The discrimination potential was remarkable and the reproducibility was adequate for fatigue Testing.
Minhao Zhu - One of the best experts on this subject based on the ideXlab platform.
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impact fretting wear behavior of 304 stainless steel thin walled tubes under low velocity
Tribology International, 2017Co-Authors: Zhenbing Cai, Haida Guan, Zhiqiang Chen, Hao Qian, Lichen Tang, Zhongrong Zhou, Minhao ZhuAbstract:Abstract This study aimed to investigate the impact fretting wear behavior of thin-walled tubes under different support interfaces with a novel impact wear Testing Rig. A tube/cylindrical contact model was used, and V-shaped fixtures with varied angles were applied. The 304 stainless steel tubes with varied lengths and a GCr15 bearing steel roller were used as the test materials. The interface deformation, impact energy absorption, and damage behavior were investigated in terms of the influence of the support angle, tube length, and the initial impact energy. After the test, the wear mechanism of the tube was investigated. The results showed that under the same lengths, when the support angle increased, the deformation displacement increased, but the contact peak force, energy absorption, and the area of worn scars decreased. The increasing length increased the contact force, energy absorption ratio, and serious damage but reduced the deformation. The increasing kinetic energy of the initial impact will decrease the energy absorption ratio. Contact fatigue spalling and oxidation are the wear mechanisms of the impact fretting wear of 304 stainless steel.
Bogdan Burduhos - One of the best experts on this subject based on the ideXlab platform.
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Design and experimental optimisation of a novel flat plate solar thermal collector with trapezoidal shape for facades integration
Applied Thermal Engineering, 2015Co-Authors: Ion Visa, Macedon Moldovan, Anca Duta, Mihai Comsit, Daniela Ciobanu, Radu Saulescu, Bogdan BurduhosAbstract:Abstract For developing solar–thermal facades, new efficient flat plate solar thermal collectors are required, fulfilling the prerequisites of efficiency and architectural acceptance, with new shapes and/or new colours. A new flat plate solar–thermal collector, with isosceles trapeze shape was developed and stepwise optimised focussing on the insulation, the bonding between the tubes and the absorber plate, the meander tube length and diameter, and the glazing. The results show that the improved contact between the tubes and the absorber plate has a significant effect on the experimental conversion efficiency, as also the tubes with larger diameters have. A self-cleaning coating applied on the outer side of the glazing, deposited through a simple cold-spraying process has a beneficial effect on the collector's functionality, without significant efficiency losses. To support architectural integration, a concept of a multi-coloured absorber plate is formulated and tested. Eight types of solar thermal collectors were tested and the optimised version reached a 60.7% efficiency on an indoor Testing Rig, corresponding to a 62.38% maximum conversion efficiency estimated based on steady-state experimental conditions. Outdoor Testing of the optimal collector is reported for a sunny day that includes 2 h with solar radiation in the same range as on the indoor Testing Rig when efficiencies of 61.85% were obtained.
Joanna M. Stephen - One of the best experts on this subject based on the ideXlab platform.
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The Ability of Medial Patellofemoral Ligament Reconstruction to Correct Patellar Kinematics and Contact Mechanics in the Presence of a Lateralized Tibial Tubercle
The American journal of sports medicine, 2015Co-Authors: Joanna M. Stephen, Andy Williams, Punyawan Lumpaopong, Alexander L Dodds, Deiary F. Kader, Andrew A. AmisAbstract:Background:Tibial tubercle (TT) transfer and medial patellofemoral ligament (MPFL) reconstruction are used after patellar dislocations. However, there is no objective evidence to guide surgical decision making, such as the ability of MPFL reconstruction to restore normal behavior in the presence of a lateralized TT.Hypothesis:MPFL reconstruction will only restore joint contact mechanics and patellar kinematics for TT–trochlear groove (TG) distances up to an identifiable limit.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees (mean TT-TG distance, 10.4 mm) were placed on a Testing Rig. Individual quadriceps heads and the iliotibial band were loaded with 205 N in physiological directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film and an optical tracking system. The MPFL attachments were marked. TT osteotomy was performed, and a metal T-plate ...
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the effect of tibial tuberosity medialization and lateralization on patellofemoral joint kinematics contact mechanics and stability
American Journal of Sports Medicine, 2015Co-Authors: Joanna M. Stephen, Andy Williams, Punyawan Lumpaopong, Alexander L Dodds, Andrew A. AmisAbstract:Background:Tibial tuberosity (TT) transfer is a common procedure to treat patellofemoral instability in patients with elevated TT–trochlear groove (TG) distances. However, the effects of TT lateralization or medialization on patellar stability, kinematics, and contact mechanics remain unclear.Hypothesis:Progressive medialization and lateralization will have increasingly adverse effects on patellofemoral joint kinematics, contact mechanics, and stability.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees were placed on a Testing Rig, with a fixed femur and tibia mobile through 90° of flexion. Individual quadriceps heads and the iliotibial band were separated and loaded with 205 N in anatomic directions using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film behind the patella and an optical tracking system. The intact knee was measured with and without a ...
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the effect of femoral tunnel position and graft tension on patellar contact mechanics and kinematics after medial patellofemoral ligament reconstruction
American Journal of Sports Medicine, 2014Co-Authors: Joanna M. Stephen, Punyawan Lumpaopong, Deiary Kaider, David J Deehan, Andrew A. AmisAbstract:Background:An incorrect femoral tunnel position or inappropriate graft tensioning during medial patellofemoral ligament (MPFL) reconstruction may cause altered patellofemoral joint kinematics and contact mechanics, potentially resulting in pain and joint degeneration.Hypothesis:Nonanatomic positioning of the tunnel or graft overtensioning during MPFL reconstruction will have an adverse effect on patellar tracking and patellofemoral joint contact mechanics.Study Design:Controlled laboratory study.Methods:Eight fresh-frozen cadaveric knees were placed on a customized Testing Rig, with the femur fixed and the tibia mobile through 90° of flexion. Individual heads of the quadriceps muscle and the iliotibial band were separated and loaded with 205 N in anatomic directions using a system of cables and weights. Patellofemoral contact pressures and patellar tracking were measured through the flexion range at 10° intervals using Tekscan pressure-sensitive film inserted between the patella and trochlea and an optica...
