The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
Ichiro Sekiya - One of the best experts on this subject based on the ideXlab platform.
-
effect of initial graft tension on knee stability and graft tension pattern in double bundle anterior cruciate ligament reconstruction
Arthroscopy, 2015Co-Authors: Hideyuki Koga, Takeshi Muneta, Kazuyoshi Yagishita, Toshifumi Watanabe, Tomoyuki Mochizuki, Masafumi Horie, Tomomasa Nakamura, Koji Otabe, Ichiro SekiyaAbstract:Purpose To determine the initial minimal tension for restoring knee stability during double-bundle anterior cruciate ligament (ACL) reconstruction in vivo. Methods Patients who underwent primary double-bundle ACL reconstruction with an autologous semitendinosus tendon during 2012 were included. The bundles were fixed to a graft-Tensioning System during surgery. Initial graft tensions were set to the following tensions per 6 mm in graft diameter: (1) 30 N, (2) 25 N, and (3) 20 N. Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. In addition, anterior knee laxity was measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA), and the pivot-shift test was evaluated. Results Sixty patients were evaluated. The tension curves of both bundles among different initial tension settings were significantly different ( P P = .019). The tension of the posterolateral bundle graft was significantly lower than that of the anteromedial bundle graft in response to the anterior load at all settings ( P = .0017, P = .0019, and P = .0021 at 30° in the 30-N, 25-N, and 20-N settings, respectively, and P Conclusions In double-bundle ACL reconstruction, initial tension could be set as low as 25 N; however, initial tension of 20 N is not recommended because it might result in residual pivot shift in some cases, although the pivot-shift difference was not significant. Level of Evidence Level IV, therapeutic case series.
-
effect of posterolateral bundle graft fixation angles on graft tension curves and load sharing in double bundle anterior cruciate ligament reconstruction using a transtibial drilling technique
Arthroscopy, 2013Co-Authors: Hideyuki Koga, Takeshi Muneta, Kazuyoshi Yagishita, Tomoyuki Mochizuki, Masafumi Horie, Tomomasa Nakamura, Atsushi Okawa, Ichiro SekiyaAbstract:Purpose To evaluate the effect of posterolateral bundle (PLB) graft fixation angles on graft tension curves and load sharing between the anteromedial bundle (AMB) and the PLB in double-bundle anterior cruciate ligament (ACL) reconstruction. Methods Twenty-four patients who underwent double-bundle ACL reconstruction were included in this study. AMB and PLB were provisionally fixed to a graft Tensioning System during surgery. The graft fixation settings were as follows: (1) AMB at 20° and PLB at 0° (A20P0), (2) AMB at 20° and PLB at 20° (A20P20), and (3) AMB at 20° and PLB at 45° (A20P45). Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. A pivot-shift test, as well as factors affecting the residual pivot-shift, was also evaluated. Results A20P45 created reciprocal tension curves and load sharing, in which the tension in both bundles was equivalent during flexion-extension and during each loading test at 30°. In A20P0, the tension of the AMB was constantly higher than that of the PLB. Seven patients showed grade 1 pivot-shift phenomenon in A20P0, whereas no patient showed a positive pivot-shift at other settings. Larger tension reduction of the PLB between 0° and 30° and smaller load sharing of the PLB were significant factors affecting residual pivot-shift. Conclusions In double-bundle ACL reconstruction, fixation of the AMB at 20° and the PLB at 45° created reciprocal tension curves and load sharing between the bundles. Fixation of the AMB at 20° and the PLB at 0° led to insufficient tension in the PLB, resulting in a residual pivot-shift phenomenon in 7 of 24 patients. Level of Evidence Level IV, therapeutic case series.
Felix Suarezriestra - One of the best experts on this subject based on the ideXlab platform.
-
long span wooden structural floors with self Tensioning System performance under asymmetrical loads
Advances in Materials Science and Engineering, 2016Co-Authors: Javier Estevezcimadevila, Dolores Oterochans, Emilio Martingutierrez, Felix SuarezriestraAbstract:This study analyzes the performance of wooden structural floors equipped with the self-Tensioning System patented by the authors, consisting of a force multiplying mechanism connected to a self-Tensioning tendon, which is activated automatically when the load is applied to the structural element. The paper describes the System’s difficulties when the structural floor is subjected to asymmetrical loads. The proposed solution consists of anchoring the tendon by an adhesive connection in the central part of the piece yielding a favorable redistribution of the bending moments and an effective performance in terms of deformations. The comparative study focuses on π-shape cross section pieces with spans of 12 m and 15 m, using sections without prestressing and with initial prestressing and self-Tensioning System.
-
self Tensioning System for long span wooden structural floors
Construction and Building Materials, 2016Co-Authors: Javier Estevezcimadevila, Dolores Oterochans, Emilio Martingutierrez, Felix SuarezriestraAbstract:Abstract A patented self-Tensioning System for long-span wooden structural floors is described that increases the performance of the deflected sections in terms of both resistance and deformation. The System is based on a force multiplier mechanism composed by two connecting rods which are secured to a post-stressing tendon. The mechanical device is activated by the transmission of the load from the structural element to the supports, causing an elongation and stressing the tendon. This transmission comes with a slight vertical displacement of the supports. Throughout this System, the intensity of the Tensioning force varies with the applied load; thus, a more favorable bending moment distribution from the load is obtained, and the relative deformations of the different sections of the piece are reduced. This article presents a comparative study of the structural behavior of π-shape cross section wooden structural floors with spans from 9 m to 18 m, comparing sections with and without pre-stress, and sections with the self-Tensioning System.
Donogh Lang - One of the best experts on this subject based on the ideXlab platform.
-
modelling of marine riser tensioner load variations and implications for minimum top tension settings in drilling risers
ASME 2012 31st International Conference on Ocean Offshore and Arctic Engineering, 2012Co-Authors: Conor Gallagher, Dara Williams, Donogh LangAbstract:As the pace of deepwater oil and gas exploration continues to grow, so too does demand for modern drilling vessels with equipment capable of operating in water depths of 10,000ft or greater. These greater water depths place significant demands on the drilling riser and the riser Tensioning System. Modern riser tensioners are complex hydro-pneumatic Systems and far from applying a constant top tension, the stiffness and damping characteristics associated with the tensioner mean that the applied tension can vary substantially as the tensioner strokes in response to vessel heave. As a result it is critical that the riser tensioner System response be captured in sufficient detail when evaluating the loads on the drilling riser.Riser tensioner Systems for deepwater drilling must be capable of supplying the required tension to satisfy the minimum stability tension requirement, as per API RP 16Q; however this recommended practice does not adequately account for dynamic tensioner load variation, which can be up to 50% of the nominal tension. For deepwater drilling riser Systems, where riser load limits are being approached, accurate modeling of the tensioner System load variation is required to ensure that the riser does not experience compression or excessive stresses. Furthermore, as the dynamic tension variations are largely velocity dependent, they can be relatively independent of water depth. Thus larger percentage variations in tension are experienced at low tensions when compared to higher tensions. This is an important consideration when calculating minimum top tensions for deepwater drilling rigs in shallower water depths.This paper presents a comparison of the response of a direct-acting riser tensioner (DAT) System for a range of environments. The comparison is based on results from detailed tensioner models that include the individual hydraulic and pneumatic components of the tensioner System and that are fully integrated with a non-linear 3D structural FE analysis tool [1]. The FE model is based on a widely-validated-non-linear software tool [3]. The detailed tensioner model has been validated against manufacturer performance data for existing in-service tensioner Systems. The detailed tensioner model has also been used as part of a drilling riser recoil analysis study [1] which provided a good comparison of recoil analysis results against a published recoil test case. The impact on the global riser response of accurately modeling the tensioner System behavior is demonstrated, while the implications for the calculation of minimum top tension are also discussed.Copyright © 2012 by ASME
Hideyuki Koga - One of the best experts on this subject based on the ideXlab platform.
-
effect of initial graft tension on knee stability and graft tension pattern in double bundle anterior cruciate ligament reconstruction
Arthroscopy, 2015Co-Authors: Hideyuki Koga, Takeshi Muneta, Kazuyoshi Yagishita, Toshifumi Watanabe, Tomoyuki Mochizuki, Masafumi Horie, Tomomasa Nakamura, Koji Otabe, Ichiro SekiyaAbstract:Purpose To determine the initial minimal tension for restoring knee stability during double-bundle anterior cruciate ligament (ACL) reconstruction in vivo. Methods Patients who underwent primary double-bundle ACL reconstruction with an autologous semitendinosus tendon during 2012 were included. The bundles were fixed to a graft-Tensioning System during surgery. Initial graft tensions were set to the following tensions per 6 mm in graft diameter: (1) 30 N, (2) 25 N, and (3) 20 N. Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. In addition, anterior knee laxity was measured with the KT-1000 arthrometer (MEDmetric, San Diego, CA), and the pivot-shift test was evaluated. Results Sixty patients were evaluated. The tension curves of both bundles among different initial tension settings were significantly different ( P P = .019). The tension of the posterolateral bundle graft was significantly lower than that of the anteromedial bundle graft in response to the anterior load at all settings ( P = .0017, P = .0019, and P = .0021 at 30° in the 30-N, 25-N, and 20-N settings, respectively, and P Conclusions In double-bundle ACL reconstruction, initial tension could be set as low as 25 N; however, initial tension of 20 N is not recommended because it might result in residual pivot shift in some cases, although the pivot-shift difference was not significant. Level of Evidence Level IV, therapeutic case series.
-
effect of posterolateral bundle graft fixation angles on graft tension curves and load sharing in double bundle anterior cruciate ligament reconstruction using a transtibial drilling technique
Arthroscopy, 2013Co-Authors: Hideyuki Koga, Takeshi Muneta, Kazuyoshi Yagishita, Tomoyuki Mochizuki, Masafumi Horie, Tomomasa Nakamura, Atsushi Okawa, Ichiro SekiyaAbstract:Purpose To evaluate the effect of posterolateral bundle (PLB) graft fixation angles on graft tension curves and load sharing between the anteromedial bundle (AMB) and the PLB in double-bundle anterior cruciate ligament (ACL) reconstruction. Methods Twenty-four patients who underwent double-bundle ACL reconstruction were included in this study. AMB and PLB were provisionally fixed to a graft Tensioning System during surgery. The graft fixation settings were as follows: (1) AMB at 20° and PLB at 0° (A20P0), (2) AMB at 20° and PLB at 20° (A20P20), and (3) AMB at 20° and PLB at 45° (A20P45). Bundle tension was recorded during knee flexion-extension and in response to anterior or rotatory loads. A pivot-shift test, as well as factors affecting the residual pivot-shift, was also evaluated. Results A20P45 created reciprocal tension curves and load sharing, in which the tension in both bundles was equivalent during flexion-extension and during each loading test at 30°. In A20P0, the tension of the AMB was constantly higher than that of the PLB. Seven patients showed grade 1 pivot-shift phenomenon in A20P0, whereas no patient showed a positive pivot-shift at other settings. Larger tension reduction of the PLB between 0° and 30° and smaller load sharing of the PLB were significant factors affecting residual pivot-shift. Conclusions In double-bundle ACL reconstruction, fixation of the AMB at 20° and the PLB at 45° created reciprocal tension curves and load sharing between the bundles. Fixation of the AMB at 20° and the PLB at 0° led to insufficient tension in the PLB, resulting in a residual pivot-shift phenomenon in 7 of 24 patients. Level of Evidence Level IV, therapeutic case series.
Javier Estevezcimadevila - One of the best experts on this subject based on the ideXlab platform.
-
long span wooden structural floors with self Tensioning System performance under asymmetrical loads
Advances in Materials Science and Engineering, 2016Co-Authors: Javier Estevezcimadevila, Dolores Oterochans, Emilio Martingutierrez, Felix SuarezriestraAbstract:This study analyzes the performance of wooden structural floors equipped with the self-Tensioning System patented by the authors, consisting of a force multiplying mechanism connected to a self-Tensioning tendon, which is activated automatically when the load is applied to the structural element. The paper describes the System’s difficulties when the structural floor is subjected to asymmetrical loads. The proposed solution consists of anchoring the tendon by an adhesive connection in the central part of the piece yielding a favorable redistribution of the bending moments and an effective performance in terms of deformations. The comparative study focuses on π-shape cross section pieces with spans of 12 m and 15 m, using sections without prestressing and with initial prestressing and self-Tensioning System.
-
self Tensioning System for long span wooden structural floors
Construction and Building Materials, 2016Co-Authors: Javier Estevezcimadevila, Dolores Oterochans, Emilio Martingutierrez, Felix SuarezriestraAbstract:Abstract A patented self-Tensioning System for long-span wooden structural floors is described that increases the performance of the deflected sections in terms of both resistance and deformation. The System is based on a force multiplier mechanism composed by two connecting rods which are secured to a post-stressing tendon. The mechanical device is activated by the transmission of the load from the structural element to the supports, causing an elongation and stressing the tendon. This transmission comes with a slight vertical displacement of the supports. Throughout this System, the intensity of the Tensioning force varies with the applied load; thus, a more favorable bending moment distribution from the load is obtained, and the relative deformations of the different sections of the piece are reduced. This article presents a comparative study of the structural behavior of π-shape cross section wooden structural floors with spans from 9 m to 18 m, comparing sections with and without pre-stress, and sections with the self-Tensioning System.
