Clinical Features and Surgical Outcomes of Lower Lumbar Osteoporotic Vertebral Collapse with Symptomatic Stenosis: A Surgical Strategy from a Multicenter Case Series

Shimizu Takayoshi,Fujibayashi Shunsuke,Masuda Soichiro,Kimura Hiroaki,Ishibe Tatsuya,Ota Masato,Tamaki Yasuyuki,Onishi Eijiro,Ito Hideo,Otsuki Bungo,Murata Koichi,Matsuda Shuichi 대한척추외과학회 2022 Asian Spine Journal Vol.16 No.6

Study Design: A retrospective multicenter case series was conducted.Purpose: This study was designed to investigate the clinical features and surgical outcomes of lower lumbar osteoporotic vertebral collapse (LL-OVC) with symptomatic stenosis based on various surgical procedures and classify them using the newly developed collapse severity criteria.Overview of Literature: The surgical outcomes of LL-OVC with symptomatic stenosis remain unclear.Methods: We investigated patients who underwent surgical intervention for LL-OVC (L3, L4, and/or L5) with symptomatic foraminal and/or central stenosis from eight spine centers. Only patients with a minimum follow-up duration of 1 year were included. We developed new criteria to grade vertebral collapse severity (grade 1, 0%–25%; grade 2, 25%–50%; grade 3, 50%–75%; and grade 4, 75%–100%). The clinical features and outcomes were compared based on the collapse grade and surgical procedures performed (i.e., decompression alone, posterior lateral fusion [PLF], lateral interbody fusion [LIF], posterior/transforaminal interbody fusion [PLIF/TLIF], or vertebral column resection [VCR]).Results: In this study, 59 patients (average age, 77.4 years) were included. The average follow-up period was 24.6 months. The clinical outcome score (Japanese Orthopaedic Association score) was more favorable in the LIF and PLIF/TLIF groups than in the decompression alone, PLF, and VCR groups. The use of VCR was associated with a high rate of revision surgery (57.1%). No significant difference in clinical outcomes was observed between the collapse grades; however, grade 4 collapse was associated with a high rate of revision surgery (40.0%).Conclusions: When treating LL-OVC, appropriate instrumented reconstruction with rigid intervertebral stability is necessary. According to our newly developed criteria, LIF may be a surgical option for any collapse grade. The use of VCR for grade 4 collapse is associated with a high rate of revision.

Numerical Simulation of the Fluvial Processes in the Channels by Sediment Mining

장창래,Yasuyuki Shimizu,이기하 대한토목학회 2015 KSCE Journal of Civil Engineering Vol.19 No.3

This study aims to experimentally and numerically investigate the fluvial processes of channels disturbed through sand or gravelmining. A two-dimensional numerical model is applied to simulate flume experiments. A moving boundary-fitted coordinate systemis used to describe the channel changes. As a numerical scheme, the cubic interpolated pseudoparticle method is used to calculate theflow field and bed changes, which introduces little numerical diffusion. The numerical model is verified with experimental data. Theinflow sediment from the upstream is trapped into a pit and the sediment deposit wedge migrated to the downstream with a steepsubmerged angle of repose. The numerical and experimental results show that the sediment deposit wedge in the pit migrates to thedownstream under the condition of steady state. The adjustment time within the disturbed channels increases as the dimension of thepit is increased. The sediment mining pit migrates with speed in the steep channel. Moreover, the numerical experiments show thatthe migration speed is proportional to the sediment inflow. And the disturbed channels by the sediment mining are affected by thesediment inflow conditions of the upstream and adjusted to the new state of equilibrium.

Numerical Simulation of the Channels with Erodible Banks

장창래(Jang Chang-Lae),Yasuyuki Shimizu,정관수(Jung Kwansue) 대한토목학회 2003 대한토목학회 학술대회 Vol.2003 No.10

Numerical Simulation for Braided Rivers with Erodible Banks

Chang-Lae Jang,Yasuyuki Shimizu 대한토목학회 2005 KSCE journal of civil engineering Vol.9 No.5

안동댐 하류 하천에서 사주의 재현 모의

장창래(Jang Chang-Lae),Shimizu Yasuyuki 대한토목학회 2010 대한토목학회논문집 B Vol.30 No.4B

본 연구에서는 안동댐 하류 하천을 대상으로 댐 건설에 의해 하천의 변화에 미치는 영향을 파악하고, 모래시주의 복원 및 재현 방안을 검토 하였다. 안동댐과 임하댐의 영향으로 댐 하류 하천에서 하상이 저하되고 하상토의 평균 입경이 굵어지는 특성을 보여주고 있으며, 저수로의 수가 증가하였다. 안동댐 건설 후에는 식생의 면적이 약간 증가하고 있으나, 임하댐이 건설되면서부터 식생의 면적이 급격하게 증가되고 있다. 댐 건설에 의해 치수안전도는 재현기간을 비교하여 5에서 10배정도 증가되고, 댐 건설 전과 후의 강턱유량은 2,857 ㎥/s에서 580 ㎥/s로 감소되었다. 또한 평균 하도 폭 및 경사를 이용한 등류조건에서는 댐 건설 전과 후의 강턱유량에 대한 중규모 하상형태의 영역구분은 단열사주와 복렬사주의 중간 영역으로부터 완전한 복렬사주 영역으로 변화하였다. 하상변동 계산에서는 댐 건설 전에 명확한 사주 및 유로가 형성되었고, 댐 건설 후에는 망상유로가 형성되었으며, 댐 건설로 인한 유량의 변화에 의해 사주형상이 변화되는 것을 알 수 있었다. This study examined the physical effects on the river changes downstream of Andong dam and simulated the reproduction of sand bars and the geomorphic changes numerically. The river bed downstream of Aandong dam and Imha dam was decreased and the mean diameter of bed materials was increased, and the number of lower channels was increased. The vegetated area was slightly increased after Andong dam construction. Moreover, the area was abruptly increased after Imha dam construction. The bankfull discharges was estimated to 580 ㎥/s after the dams construction and 2,857 ㎥/s before the dams. A flood mitigation safety by the dams construction considering return period was increased to 5 to 10 times. As a result of meso-scale regime analysis by using banfull discharge, the regime between single bars and multiple row bars before the dams construction was changed to completely the regime of multiple row bars after the dams. The numerical simulation results showed that the sand bars and lower channels were developed before the dams, and braided river was developed after the dams. This meant that the patterns of sand bars was changed by variable discharge due to the dams construction.

Numerical Simulation of Unsteady Cavitation in a High-speed Water Jet

Peng, Guoyi,Okada, Kunihiro,Yang, Congxin,Oguma, Yasuyuki,Shimizu, Seiji Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.1

Concerning the numerical simulation of high-speed water jet with intensive cavitation this paper presents a practical compressible mixture flow method by coupling a simplified estimation of bubble cavitation and a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by URANS for compressible fluid. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow, and the effect of cavitation on the flow turbulence is considered by applying a density correction to the evaluation of eddy viscosity. High-speed submerged water jets issuing from a sheathed sharp-edge orifice nozzle are treated when the cavitation number, ${\sigma}=0.1$, and the computation result is compared with experimental data The result reveals that cavitation occurs initially at the entrance of orifice and bubble cloud develops gradually while flowing downstream along the shear layer. Developed bubble cloud breaks up and then sheds downstream periodically near the sheath exit. The pattern of cavitation cloud shedding evaluated by simulation agrees experimental one, and the possibility to capture the unsteadily shedding of cavitation clouds is demonstrated. The decay of core velocity in cavitating jet is delayed greatly compared to that in no-activation jet, and the effect of the nozzle sheath is demonstrated.

Numerical Simulation of Unsteady Cavitation in a High-speed Water Jet

Guoyi Peng,Kunihiro Okada,Congxin Yang,Yasuyuki Oguma,Seiji Shimizu 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.1

Concerning the numerical simulation of high-speed water jet with intensive cavitation this paper presents a practical compressible mixture flow method by coupling a simplified estimation of bubble cavitation and a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by URANS for compressible fluid. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow, and the effect of cavitation on the flow turbulence is considered by applying a density correction to the evaluation of eddy viscosity. High-speed submerged water jets issuing from a sheathed sharp-edge orifice nozzle are treated when the cavitation number, σ = 0.1, and the computation result is compared with experimental data The result reveals that cavitation occurs initially at the entrance of orifice and bubble cloud develops gradually while flowing downstream along the shear layer. Developed bubble cloud breaks up and then sheds downstream periodically near the sheath exit. The pattern of cavitation cloud shedding evaluated by simulation agrees experimental one, and the possibility to capture the unsteadily shedding of cavitation clouds is demonstrated. The decay of core velocity in cavitating jet is delayed greatly compared to that in no-activation jet, and the effect of the nozzle sheath is demonstrated.