scholarly journals Method for Orthogonal Edge Routing of Directed Layered Graphs with Edge Crossings Reduction

2021 ◽  
Author(s):  
Jordan Raykov
Keyword(s):  
Heuristic Algorithm ◽  
Flow Direction ◽  
Shortest Paths ◽  
Design Tool ◽  
Adjacent Segment ◽  
Rectangular Grid ◽  
Line Segments ◽  
Graph Design ◽  
Adjacent Segments ◽  
Edge Crossings

This paper presents a method for automated orthogonal edge routing of directed layered graphs using the described edge crossings reduction heuristic algorithm. The method assumes the nodes are pre-arranged on a rectangular grid composed of layers across the flow direction and lanes along the flow direction. Both layers and lanes are separated by rectangular areas defined as pipes. Each pipe has associated segment tracks. The edges are represented as orthogonal polylines consisting of line segments and routed along the shortest paths. Each segment is assigned to a pipe and to a segment track in it. The edge crossings reduction uses an iterative algorithm to resolve crossings between segments. Conflicting segments are reassigned to adjacent segment tracks, either by swapping with adjacent segments, or by inserting new tracks and calculating the shortest paths of edges. The algorithm proved to be efficient and was implemented in an interactive graph design tool.

scholarly journals TELD with limited foraminoplasty has potential biomechanical advantages over TELD with large annuloplasty: an in-silico study

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Jingchi Li ◽  
Chen Xu ◽  
Xiaoyu Zhang ◽  
Zhipeng Xi ◽  
Mengnan Liu ◽  
...  
Keyword(s):  
Risk Factors ◽  
Postoperative Complications ◽  
Poor Prognosis ◽  
Adjacent Segment Degeneration ◽  
Iatrogenic Injury ◽  
Adjacent Segment ◽  
Fe Model ◽  
High Grade ◽  
Endoscopic Lumbar Discectomy ◽  
Adjacent Segments

Abstract Background Facetectomy, an important procedure in the in–out and out–in techniques of transforaminal endoscopic lumbar discectomy (TELD), is related to the deterioration of the postoperative biomechanical environment and poor prognosis. Facetectomy may be avoided in TELD with large annuloplasty, but iatrogenic injury of the annulus and a high grade of nucleotomy have been reported as risk factors influencing poor prognosis. These risk factors may be alleviated in TELD with limited foraminoplasty, and the grade of facetectomy in this surgery can be reduced by using an endoscopic dynamic drill. Methods An intact lumbo-sacral finite element (FE) model and the corresponding model with adjacent segment degeneration were constructed and validated to evaluate the risk of biomechanical deterioration and related postoperative complications of TELD with large annuloplasty and TELD with limited foraminoplasty. Changes in various biomechanical indicators were then computed to evaluate the risk of postoperative complications in the surgical segment. Results Compared with the intact FE models, the model of TELD with limited foraminoplasty demonstrated slight biomechanical deterioration, whereas the model of TELD with large annuloplasty revealed obvious biomechanical deterioration. Degenerative changes in adjacent segments magnified, rather than altered, the overall trends of biomechanical change. Conclusions TELD with limited foraminoplasty presents potential biomechanical advantages over TELD with large annuloplasty. Iatrogenic injury of the annulus and a high grade of nucleotomy are risk factors for postoperative biomechanical deterioration and complications of the surgical segment.

scholarly journals Biomechanical Evaluation of Different Surgical Approaches for the Treatment of Adjacent Segment Diseases After Primary Anterior Cervical Discectomy and Fusion: A Finite Element Analysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Wencan Ke ◽  
Chao Chen ◽  
Bingjin Wang ◽  
Wenbin Hua ◽  
Saideng Lu ◽  
...  
Keyword(s):  
Finite Element ◽  
Revision Surgery ◽  
Anterior Cervical Discectomy ◽  
Surgical Approaches ◽  
Adjacent Segment ◽  
Fe Model ◽  
Element Analysis ◽  
Cervical Discectomy ◽  
Computed Tomography Images ◽  
Adjacent Segments

Symptomatic adjacent segment disease (ASD) is a common challenge after anterior cervical discectomy and fusion (ACDF). The objective of this study was to compare the biomechanical effects of a second ACDF and laminoplasty for the treatment of ASD after primary ACDF. We developed a finite element (FE) model of the C2-T1 based on computed tomography images. The FE models of revision surgeries of ACDF and laminoplasty were simulated to treat one-level and two-level ASD after primary ACDF. The range of motion (ROM) and intradiscal pressure (IDP) of the adjacent segments, and stress in the cord were analyzed to investigate the biomechanical effects of the second ACDF and laminoplasty. The results indicated that revision surgery of one-level ACDF increased the ROM and IDP at the C2–C3 segment, whereas two-level ACDF significantly increased the ROM and IDP at the C2–C3 and C7-T1 segments. Furthermore, no significant changes in the ROM and IDP of the laminoplasty models were observed. The stress in the cord of the re-laminoplasty model decreased to some extent, which was higher than that of the re-ACDF model. In conclusion, both ACDF and laminoplasty can relieve the high level of stress in the spinal cord caused by ASD after primary ACDF, whereas ACDF can achieve better decompression effect. Revision surgery of the superior ACDF or the superior and inferior ACDF after the primary ACDF increased the ROM and IDP at the adjacent segments, which may be the reason for the high incidence of recurrent ASD after second ACDF.

Impact of Cervical Artificial Disc Implantation on the Biomechanical Function of Adjacent Segments

2013 ◽  
Vol 748 ◽  
pp. 358-364
Author(s):  
Wen Zhi Zhao ◽  
Bin Li ◽  
Bing Zhi Chen ◽  
Sheng Wei He ◽  
Jin Su ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Intervertebral Disc ◽  
Interbody Fusion ◽  
Element Model ◽  
Cervical Disc ◽  
Adjacent Segment ◽  
Artificial Disc ◽  
Range Of Movement ◽  
Fusion Surgery ◽  
Adjacent Segments

The range of movement(ROM) of adjacent segments and the change of intervertebral disc stress after implanting artificial cervical disc are investigated. The contact problem for bio-modeling is introduced. A normal cervical spine finite element model is proposed. The bone graft and fusion between C5 and C6 and C5/6 artificial disc implantation were simulated. The range of movement on adjacent segment and the change of intervertebral disc’s stress in such two cases are analyzed. Computational results show that the model includes the ligaments, joint capsule and other soft tissue structures, which is real, fine and high accuracy. When the adjacent intervertebral ROM was increased after interbody fusion surgery, the stress of corresponding intervertebral disc was increased obviously and the stress of upper segment of nucleus pulposus and annulus fibrosus were also increased about 70% ,besides the next-bit segments was increased about 40%. There were no differences among cervical spine ROM except extension (p> 0.05) after the implantation of artificial disc, and the stress on adjacent segments was increased less than 10%. The implantation of artificial cervical disc can release the stress on adjacent segments in a certain extent, and resume cervical activities at the same time.

scholarly journals Analysis of the influence parameters spine-pelvic balance on the risk of development degeneration and degenerative disease of adjacent segments after lumbar spine rigid fixation

2021 ◽  
pp. 24-30
Author(s):  
A. V. Spiridonov ◽  
Yu. Ya. Pestryakov ◽  
A. A. Kalinin ◽  
V. A. Byvaltsev
Keyword(s):  
Lumbar Spine ◽  
Lumbar Lordosis ◽  
Degenerative Disease ◽  
Adjacent Segment ◽  
Rigid Fixation ◽  
Inclusion Criteria ◽  
Biomechanical Stress ◽  
Lumbar Stabilization ◽  
Adjacent Segments

Introduction An increase in the load on adjacent segments causes changes in the parameters of the spinal-pelvic balance and, as a consequence, the development of the so-called biomechanical «stress». Such pressures are a key link in the pathogenesis of degeneration, and in the presence of clinical and neurological manifestations of the latter and adjacent segment degenerative disease (ASD/ASDd).Objective of this study was to assess the effect of the parameters of the spinal pelvic balance on the risk of developing ASD/ASDd after dorsal decompression-stabilizing interventions (DDSI).Material and Methods The study included medical records of patients who underwent DDSI for lumbar spine degenerative diseases. Clinical and instrumental parameters were assessed.Results Based on the inclusion criteria, 98 patients (48 with signs of ASD/ASDd and 50 without) were included in the study. The average postoperative follow-up period for the respondents was 46.6 ± 9.8 months. If PI/ LL parameters were <10 and the ratio of segmental and global lumbar lordosis (LIV-SI/LI-SI) was 50% or more, the incidence of ASD/ASDd was significantly lower in patients who underwent rigid lumbar stabilization surgery.Conclusion The values of PI/LL parameters and the ratio of segmental and global lumbar lordosis are obvious risk factors for the development of ASD/ASDd after rigid lumbar spine DDSI.

scholarly journals Are Congenital Cervical Block Vertebrae a Risk Factor for Adjacent Segment Disease? A Retrospective Cross-Sectional CT and MR Imaging Study

Diagnostics ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 90
Author(s):  
Cornelius Jung ◽  
Patrick Asbach ◽  
Stefan M. Niehues
Keyword(s):  
Mr Imaging ◽  
Imaging Study ◽  
Cross Sectional Study ◽  
Mean Value ◽  
Degenerative Changes ◽  
Adjacent Segment Disease ◽  
Adjacent Segment ◽  
Cross Sectional ◽  
Sum Score ◽  
Adjacent Segments

Adjacent segment disease (ASDI) is a well-described complication of spinal fusion surgery that may ultimately lead to spinal stenosis and repeated surgical intervention. Although congenital block vertebrae also present with degenerative changes in the adjacent segments, this has not yet been systematically investigated. The aim of this study was to assess the presence and degree of ASDI in congenital cervical block vertebrae. Methods: A total of 51 patients with congenital vertebral fusion in one cervical segment were analysed in this IRB-approved retrospective cross-sectional study using available CT/MR imaging. Exclusion criteria were prior spinal surgery and the presence of additional hereditary abnormalities. We assessed the severity of degenerative changes using a sum score. The sum score for adjacent and non-adjacent segments was then divided by the highest possible degeneration score, which resulted in a ratio of severity for adjacent and remaining segments (ranging from 0 to 1). Results: Overall, 35 of 51 patients (68.6%) showed evidence of ASDI, and 34 of 51 patients (66.7%) also showed degenerative changes in the remaining segments. The severity score was significantly higher (p = 0.025) in the segments adjacent to the congenital block vertebrae (mean value 0.307) compared to the non-adjacent segments (mean value 0.188). Conclusions: Our results suggest that ASDI is also caused by congenital block vertebrae of the cervical spine.

scholarly journals Clinical effect analysis and radiographic outcomes of Isobar TTL system for two-segmental lumbar degenerative disease: a retrospective study

2019 ◽  
Author(s):  
zhisheng ji ◽  
Zhi-Sheng Ji ◽  
Hua Yang ◽  
Yu-Hao Yang ◽  
Shao-Jin Li ◽  
...  
Keyword(s):  
Clinical Effect ◽  
Degenerative Disease ◽  
Adjacent Segment ◽  
Intervertebral Space ◽  
Lumbar Degenerative Disease ◽  
Effect Analysis ◽  
Radiographic Outcomes ◽  
Adjacent Segments ◽  
Rigid Group

Abstract Background: Non-fusion fixation is an effective way to treat lumbar degeneration. The present study evaluated the clinical effect analysis and radiographic outcomes of Isobar TTL system for two-segmental lumbar degenerative disease. Method: Forty-one patients with two-segmental lumbar degenerative disease who underwent surgical treatment by Isobar TTL dynamic stabilization system (n=20) and rigid system (n=21) from January 2013 to June 2017. The mean follow-up period was 23.6 (range 15–37) months. Clinical outcomes were evaluated by oswestry dysfunction index (ODI), visual analogue score (VAS) and modified Macnab. Radiographic evaluations included the height of intervertebral space and range of motion (ROM) of the operative segments and proximal adjacent segment. The intervertebral disc signal change was classified by the modified Pfirrmann grade and University of California at Los Angeles (UCLA) system. Results: The clinical outcomes including the ODI and VAS were significantly improved in two groups after operation, but the difference between two groups was not significant. In addition, the clinical efficacy of modified Macnab in two groups was similar too. Radiologic outcomes include height of intervertebral space, lumbar mobility and intervertebral disc signal. The height of intervertebral space of upper adjacent segments of L2/3 in the rigid group were significantly lower than those in the Isobar TTL group at the last follow-up. Furthermore, the number of fixed segment ROM of L3/4 in Isobar TTL group was significantly lower than pre-operation, suggesting that fixed segment ROMs in Isobar TTL group were limited. And, the ROM of upper adjacent segments of L2/3 in the last follow-up of rigid group increased significantly, while the ROM of L2/3 in Isobar TTL group haven’t changed after operation. At last, the incidence of adjacent segment degeneration was significantly greater in the rigid group than the Isobar TTL group according to modified Pfirrmann grading system and the UCLA system. Conclusion: Isobar TTL system could get a good clinical effect for treatment of two-segmental lumbar degenerative disease. Compared with rigid fixation, Isobar TTL system can get better radiographic outcomes and maintain the mobility of the stabilized segments with less influence on the proximal adjacent segment.

A Computational and Experimental Investigation Into Biomechanics of Lumbar Spine Stabilized With a Novel Posterior Dynamic Stabilization System

2009 ◽  
Author(s):  
Ali Kiapour ◽  
Vijay K. Goel ◽  
Manoj Krishna ◽  
Sarath Koruprolu ◽  
Rachit Parikh ◽  
...  
Keyword(s):  
Spinal Stenosis ◽  
Adjacent Segment ◽  
Facet Joints ◽  
Fusion Procedure ◽  
Severe Back Pain ◽  
Posterior Dynamic Stabilization ◽  
Dynamic Stabilizer ◽  
Lumbar Spinal ◽  
Adjacent Segments

Lumbar spinal stenosis is a progressive degenerative condition due to arthritic facet joints. Arthritic facets become inflamed and often develop osteophytes, leading to nerve compression and persistent severe back pain. When conservative treatment fails to reduce pain, surgical management may be pursued to improve the patient’s quality of life. Spinal decompression and fusion is one of the most common surgical procedures for treatment of spinal stenosis. However, fusion may result in accelerated degeneration of the adjacent motion segments and morbidity [1]. Motion preservation instrumentation is being developed to preserve motion at the involved and adjacent segments, as opposed to fusion procedure [2]. In this study, we used experimental and finite element (FE) techniques to assess and compare the biomechanics of intact spines and spines implanted with a novel posterior dynamic stabilizer device (TrueDyn™, Disc Motion Technologies, Boca Raton, FL). The effects on the adjacent segment, including motion and intra-discal pressure were analyzed.

scholarly journals Correction of adult scoliosis via a posterior-only approach

2003 ◽  
Vol 14 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Caleb R. Lippman ◽  
Caple A. Spence ◽  
A. Samy Youssef ◽  
David W. Cahill
Keyword(s):  
Posterior Instrumentation ◽  
Posterior Lumbar Interbody Fusion ◽  
Adult Scoliosis ◽  
Adjacent Segment ◽  
Anterior Release ◽  
Second Procedure ◽  
Single Posterior Approach ◽  
Upper Thoracic ◽  
Coronal Malalignment ◽  
Adjacent Segments

Object Adult scoliosis is a pathologically different entity from adolescent idiopathic scoliosis. The curves are more rigid, and rotational deformity and multilevel sagittal vertebral slippages compound the coronal malalignment. To correct these deformities, a surgical anterior release procedure is usually required, as well as posterior instrumentation-assisted fusion. This exposes the patient to the risks of a second procedure and of a thoracotomy or laparotomy. To decrease these risks, the authors have performed an anterior release, posterior release, and reduction via a posterior-only approach. The purpose of this study was to analyze quantitatively the degree of pre- and postoperative coronal deformity, the extent of correction, and related complications. Methods Data obtained in 20 patients with adult scoliosis were retrospectively studied. Patients presented with persistent back or lower-extremity pain, progressive deformity, or progressive neurological deficit. Sixteen patients underwent Gill-type laminectomy, radical discectomy (including fracture of any anterior and lateral osteophytes), and posterior lumbar interbody fusion (PLIF) of all apical and adjacent segments. One to four anterior release procedures were performed in each patient. Posterior instrumentation was placed over three to 15 levels. Autograft was obtained from the laminectomy sites and posterior iliac crest for fusion. There were no deaths; all patients were followed for a minimum of 1 year. The mean coronal Cobb angle improved from 36° to 14.7°. All spondylolisthetic lesions were reduced to at least Grade I. At the most recent follow-up examination, evidence of fusion was demonstrated in all patients. Reoperation for adjacent-segment failure, cephalad to the highest level of fusion, was required in two cases. Conclusions In many cases of adult scoliosis, a satisfactory multiplanar correction may be obtained via a single posterior approach and by using extended PLIF techniques. Cephalad adjacent-segment failure remains a significant problem in patients with osteoporosis, and routine extension of posterior instrumentation to the upper thoracic spine should be considered in these cases.

Effect of Container Stack Arrangements on the Power Optimization of a Container Ship

2012 ◽  
Vol 28 (01) ◽  
pp. 10-19
Author(s):  
Khairul Hassan ◽  
Maurice F. White ◽  
Cosmin Ciorta
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Aerodynamic Resistance ◽  
Computational Fluid Dynamic Simulation ◽  
Design Tool ◽  
Optimal Arrangement ◽  
Power Requirement ◽  
Air Resistance ◽  
Propulsion Power

When considering the design of a ship, an important objective is to always try and develop one that allows for maximum cargo capacity with the lowest propulsion power requirement while providing a sufficient amount of strength and stability for its safe operation. The ship with the lowest propulsion power consumes the least amount of fuel and produces the lowest amount of exhaust gas that may be harmful to the environment. In some cases, the aerodynamic resistance can be neglected, but for a high speed vessel such as a modern containership, the air resistance can be in the range of 2% to 10% of the total resistance. Aerodynamic resistance can therefore have a significant effect on power requirements and is strongly influenced by the height, breadth, and the number of container stacks on the deck. The freeboard, beam of the ship, deck house design, ship speed, wind speed, and water flow direction will also contribute significantly to a ship's resistance and required propulsive power. This paper outlines the application of computational fluid dynamic simulation as a design tool to find a strategy for the optimal arrangement of the container stacks on deck so that the vessel uses the lowest effective propulsion power to achieve a fuel efficient ship. It is deduced that an optimal stack arrangement can reduce air resistance by about 30%.

Abstract 13030: Post-systolic Shortening and Early Systolic Lengthening in the Ischemic Segment are Affected by the Contractility in its Adjacent Segment

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Daisuke Sakurai ◽  
Toshihiko Asanuma ◽  
Kasumi Masuda ◽  
Masamichi Oka ◽  
Koichiro Kotani ◽  
...  
Keyword(s):  
Coronary Artery ◽  
Circumferential Strain ◽  
Left Ventricular ◽  
Frame Rate ◽  
In Vivo Model ◽  
Adjacent Segment ◽  
The Difference ◽  
Adjacent Segments ◽  
Ischemic Segment

Background: Post-systolic shortening (PSS) and early systolic lengthening (ESL) are sensitive markers of acute myocardial ischemia and the magnitude of these deformation is considered proportional to the severity of ischemia. Theoretical and mathematical models have suggested these deformation is caused by the difference of contractility between the ischemic and its adjacent normal segments. However, it has not been fully confirmed in an in vivo model yet. The aim of the study was to investigate whether PSS and ESL are affected by the contractility of its adjacent segment in an animal model which underwent left anterior descending coronary artery (LAD) occlusion (ischemic segment) followed by left circumflex coronary artery (LCx) occlusion (adjacent segment). Methods: In 6 open-chest dogs, left ventricular short-axis images with frame rate of over 90 fps (GE Vivid E9) and hemodynamics data were acquired at 3 conditions: (1) at baseline, (2) during LAD occlusion, and (3) during both LAD and LCx occlusion. Circumferential strain was analyzed in the LAD and LCx segments by speckle tracking software. End-systolic strain (ε ES ) and the amplitude of PSS and ESL (ε PSS and ε ESL ) were measured. Results: During LAD occlusion, ε PSS and ε ESL in the LAD segment significantly increased compared with baseline (ε PSS , 1.2 ± 1.1% vs. 9.5 ± 2.7%, p<0.05; ε ESL , 1.3 ± 1.0% vs. 8.5 ± 4.2%, p<0.05). During both LAD and LCx occlusion, ε ES in the LCx segment decreased, and both ε PSS and ε ESL in the LAD segment significantly decreased compared with during LAD occlusion (ε PSS , 9.5 ± 2.7% vs. 2.8 ± 1.3%, p<0.05; ε ESL , 8.5 ± 4.2% vs. 2.3 ± 1.9%, p<0.05) (figure). Conclusions: PSS and ESL diminished with the decrease of contractility in its adjacent segment. This suggests PSS and ESL occur based on the interplay of contraction between ischemic and adjacent segments and do not always reflect the severity of ischemia.

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