• Journal of Korean Neurosurgical Society
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• 제63권6호
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• pp.767-776
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• 2020

Objective : The aim of this study is to evaluate the feasibility of posterior cervical foraminotomy (PCF) for adjacent segmental disease (ASD) after anterior cervical fusion (ACF). As ACF is accepted as the standard treatment for cervical spondylosis, many studies have been conducted to evaluate the efficacy of various surgical techniques to overcome symptomatic ASD after the previous surgery. Herein, PCF was performed for the treatment of symptomatic ASD and the feasibility of the surgery was evaluated. Methods : Forty nine patients who underwent PCF due to symptomatic ASD from August 2008 to November 2017 were identified. For demographic and perioperative data, the sex, age, types of previous surgery, ASD levels, operation times, and bleeding amount were recorded. The clinical outcome was assessed using the visual analogue scale for the neck and arm, the modified Odom's criteria as well as neck disability index. Radiologic evaluations were performed by measuring disc softness, disc height, the cervical 2-7 sagittal vertical axis, cervical cobb angle, and facet violation. Results : Thirty-seven patients were enrolled in this study. The patients were divided into two groups based on the location of the pathology; paracentral (group P) or foramina (group F). Both groups showed significant clinical improvement (p<0.05). The proportion of calcified disc and facet violations was significantly larger in group F (p<0.05). The minimal disc height decrease with mild improvement on sagittal alignment and cervical lordosis was radiologically measured without statistical significance in both groups (p>0.05). Conclusion : PCF showed satisfactory clinical and radiologic outcomes for both paracentral and foraminal pathologies of ASD after ACF. Complications related to anterior revision were also avoided. PCF can be considered a feasible and safe surgical option for ASD after ACF.

• Journal of Korean Neurosurgical Society
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• 제46권4호
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• pp.292-299
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• 2009

Objective : Clinical and radiological results of posterior dynamic stabilization using interspinous U (ISU, $Coflex^{TM}$, Paradigm Spine $Inc.^{(R)}$, NY, USA) were analyzed in comparison with posterior lumbar interbody fusion (PLIF) in degenerative lumbar spinal stenosis (LSS). Methods : A retrospective study was conducted for a consecutive series of 61 patients with degenerative LSS between May 2003 and December 2005. We included only the patients completed minimum 24 months follow up evaluation. Among them, 30 patients were treated with implantation of ISU after decompressive laminectomy (Group ISU) and 31 patients were treated with wide decompressive laminectomy and posterior lumbar interbody fusion (PLIF; Group PLIF). We evaluated visual analogue scale (VAS) and Oswestry Disability Index (ODI) for clinical outcomes (VAS, ODI), disc height ratio disc height (DH), disc height/vertebral body length ${\times}100$), static vertebral slip (VS) and depth of maximal radiolucent gap between ISU and spinous process) in preoperative, immediate postoperative and last follow up. Results : The mean age of group ISU ($66.2{\pm}6.7$ years) was 6.2 years older than the mean age of group PLIF ($60.4{\pm}8.1$ years; p=0.003). In both groups, clinical measures improved significantly than preoperative values (p<0.001). Operation time and blood loss was significantly shorter and lower in group ISU than group PLIF (p<0.001). In group ISU, the DH increased transiently in immediate postoperative period ($15.7{\pm}4.5%{\rightarrow}18.6{\pm}5.9%$), however decreased significantly in last follow up ($13.8{\pm}6.6%$, p=0.027). Vertebral slip (VS) of spondylolisthesis in group ISU increased during postoperative follow-up ($2.3{\pm}3.3{\rightarrow}8.7{\pm}6.2$, p=0.040). Meanwhile, the postoperatively improved DH and VS was maintained in group PLIF in last follow up. Conclusion : According to our result, implantation of ISU after decompressive laminectomy in degenerative LSS is less invasive and provides similar clinical outcome in comparison with the instrumented fusion. However, the device has only transient effect on the postoperative restoration of disc height and reduction of slip in spondylolisthesis. Therefore, in the biomechanical standpoint, it is hard to expect that use of Interspinous U in decompressive laminectomy for degenerative LSS had long term beneficial effect.

• Journal of Korean Neurosurgical Society
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• 제64권3호
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• pp.437-446
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• 2021

Objective : To investigate the radiographic characteristics of the uppermost instrumented vertebrae (UIV) and UIV+1 compression fractures that are predictive of revision surgery following long-segment spinal fixation. Methods : A total 27 patients who presented newly developed compression fracture at UIV, UIV+1 after long segment spinal fixation (minimum 5 vertebral bodies, lowest instrumented vertebra of L5 or distal) were reviewed retrospectively. Patients were divided into two groups according to following management : revisional surgery (group A, n=13) and conservative care (group B, n=14). Pre- and postoperative images, and images taken shortly before and after the occurrence of fracture were evaluated for radiologic characteristics Results : Despite similar degrees of surgical correction of deformity, the fate of the two groups with proximal junctional compression fractures differed. Immediately after the fracture, the decrement of adjacent disc height in group A (32.3±7.6 mm to 23.7±8.4 mm, Δ=8.5±6.9 mm) was greater than group B (31.0±13.9 mm to 30.1±15.5 mm, Δ=0.9±2.9 mm, p=0.003). Pre-operative magnetic resonance imaging indicated that group A patients have a higher grade of disc degeneration adjacent to fractured vertebrae compared to group B (modified Pfirrmann grade, group A : 6.10±0.99, group B : 4.08±0.90, p=0.004). Binary logistic regression analysis indicated that decrement of disc height was the only associated risk factor for future revision surgery (odds ratio, 1.891; 95% confidence interval, 1.121-3.190; p=0.017). Conclusion : Proximal junctional vertebral compression fractures with greater early-stage decrement of adjacent disc height were associated with increased risk of future neurological deterioration and necessity of revision. The condition of adjacent disc degeneration should be considered regarding severity and revision rate of proximal junctional kyphosis/proximal junction failures.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.442-445
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• 2003

The use of a single UWB antenna which covers a wide range of frequencies is very desirable for future wireless communications system. In this paper, we propose a novel wide band printed elliptic monopole antenna for UWB(Ultra wide Band). Wideband planar monopole disc antenna have been recently studied. The proposed antenna can cover UWB frequencies from 3.5GHz to 12GHz. it is determined from 10dB return loss. The antenna consists of the printed elliptical monopole disc with microstrip-line feed. Elliptic disc of antenna and ground height operate important to matching. The results of measurement are almost similar to those of simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.694-699
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• 2002

As the demand for slim laptops requires ion'-height optical disc drives, vibration problems of optical disc drives are of great concern. Additionally, with the decrease of a track width and a depth of focus in high density drives, studies on vibration resonance between mechanical parts become more important. From the vibration point of view, the performance of optical disc drives is closely related with the relative displacement between a disc and an objective lens which is controlled by servo mechanism. In other words, to read and write data properly, the relative displacement between an optical disc and an objective lens should be within a certain limit. The relative displacement is dependent on not only an anti-vibration mechanism design but also servo control capability. Good servo controls can make compensation for poor mechanisms, and vice versa. In a usual development process, robustness of the anti-vibration mechanism is always verified with the servo control of an objective lens. Engineers partially modify servo gain margin in case of a data reading error. This modification cannot correct the data reading error occasionally and the mechanism should be redesigned more robustly. Therefore it is necessary to verify a mechanism with respect to the possible servo gain plot. In this study we propose the experimental verification method far anti-vibration mechanism with respect to the existing servo gain plot. This method verifies axial vibration characteristics of optical disc drives on the basis of transmissibility. Using this method, we verified our mechanism and modified the mechanism for better anti-vibration characteristics.

• 한국소음진동공학회논문집
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• 제12권11호
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• pp.833-839
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• 2002

As the demand for slim laptops requires low-height optical disc drives, vibration problems of optical disc drives are of great concern. Additionally, with the decrease of a track width and a depth of focus in high density drives, studies on vibration resonance between mechanical parts become more important. From the vibration point of view, the performance of optical disc drives is closely related with the relative displacement between a disc and an objective lens which is controlled by servo mechanism. In other words, to read and write data properly, the relative displacement between an optical disc and an objective lens should be within a certain limit. The relative displacement is dependent on not only an anti-vibration mechanism design but also servo control capability. Good servo controls can make compensation for poor mechanisms, and vice versa. In a usual development process, robustness of the anti-vibration mechanism is always verified with the servo control of an objective lens. Engineers partially modify servo gain margin in case of a data reading error. This modification cannot correct the data reading error occasionally and the mechanism should be redesigned more robustly. Therefore it is necessary to verify a mechanism with respect to the possible servo gain plot. In this study we propose the experimental verification method for anti-vibration mechanism with respect to the existing servo gain plot. Thismethod verifies axial vibration characteristics of optical disc drives on the basis of transmissibility. Using this method, we verified our mechanism and modified the mechanism for better anti-vibration characteristics.

• 산업경영시스템학회지
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• 제20권43호
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• pp.197-204
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• 1997

Torques on each joint, the compression on L5/S1 disc, the force on hand of a rider are estimated using a static biomechnic model. Forces that the rider applies to the pedals, saddle and handle during starting and speeding are estimated using static mechanics. Physical stress is considered accroding to handle height and horizontal distance between handle and pedal. When handle height is higher in normal speeding, the force on handle and sum of torques on each joint decreases.

• 해부∙생물인류학
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• 제31권4호
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• pp.151-158
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• 2018

척추사이구멍은 인접한 두 척추뼈와 그 사이의 척추사이원반으로 구성된다. 이전의 척추사이구멍에 대한 연구들은 다양한 방법으로 수행이 되었다. 이번 연구에서는 실리콘 주형을 이용해서 척추사이구멍의 특징을 알아보았다. 시신18구를 해부하여 허리의 척추사이구멍을 해부하였다. 첫째로는 척수신경의 위치를 측정하였다. 둘째로는 척추사이구멍을 덮고있는 모든 조직을 제거하여 척추사이구멍 단면의 가장 좁은 부위를 측정하였다. 조직이 제거된 척추사이구멍은 실리콘주형으로 채워졌다. 실리콘주형이 굳어진 다음에는 구멍에서 분리되었다. 단면으로 잘린 실리콘주형을 종이 위에 도장처럼 찍고, 그것을 컴퓨터에 저장하였다. 척추사이구멍의 주형의 면적, 둘레, 높이, 폭이 컴퓨터에서 분석되었다. 허리의 다섯 개 척추사이구멍에서 면적과 둘레는 통계학적인 차이를 보이지 않았다. 하지만 둘째에서 다섯째 허리뼈에 걸쳐서 높이는 낮아지는 경향, 폭은 넓어지는 경향을 보였다. 또한 높이와 폭은 다섯째 구멍에서 유의미한 차이가 있었다. 높이는 다른 구멍들 중에서 가장 낮았고, 폭은 가장 넓었다. 척수신경은 첫째에서 넷째허리뼈에서는 척추사이원반 근처를 지나갔고, 다섯째허리뼈에서는 척추사이원반 아래쪽으로 지나갔다. 이번 연구는 척추사이구멍의 3차원적 입체 구조를 실리콘주형으로 확인하였다. 기존의 평면적 연구에서 관찰되지 않았던 다른 성질들을 확인할 수 있었다. 즉, 허리척추뼈에서 척추사이구멍의 면적과 둘레는 일정하였으나 높이와 폭은 전체적으로 변화하는 양상을 보였다.

• Journal of Korean Neurosurgical Society
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• 제55권6호
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• pp.343-347
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• 2014

Objective : To evaluate the relationship between postoperative increase in intervertebral disc space height (IVH) and posterior axial neck in cases of degenerative cervical disease treated with anterior cervical discectomy and fusion (ACDF). Methods : A total of 155 patients who underwent ACDF with more than 1 year follow up were included. Radiologically, IVH and interfacet distance (IFD) of the operated segment were measured preoperatively and postoperatively. We clinically evaluated neck and arm pains according to visual analogue scale (VAS) scores and assessed neck disability index (NDI) scores preoperatively, postoperatively, at 3 months, 6 months, and 1 year postoperatively. The relationship between radiological parameters, and clinical scores were analyzed using a regression analysis. Results : The mean increase in IVH was 2.62 mm, and the mean increase in IFD was 0.67 mm. The VAS scores for neck pain preoperatively, postoperatively, and at 3 months, 6 months, 1 year postoperatively were 4.46, 2.11, 2.07, 1.95, and 1.29; those for arm pain were 5.89, 3.24, 3.20, 3.03, and 2.18. The NDI scores were improved from 18.52 to 7.47. No significant relationship was observed between the radiological evaluation results regarding the increase in intervertebral height or interfacet distance and clinical changes in VAS or NDI scores. Conclusion : The increase in intervertebral space or interfacet distance by the insertion of a large graft material while performing ACDF for the treatment of degenerative cervical disease was not related with the change in VAS scores for neck and arm pains and NDI scores postoperatively and during the follow-up period.

• Journal of Korean Neurosurgical Society
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• 제58권2호
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• pp.119-124
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• 2015

Objective : We compared the clinical and radiographic outcomes of stand-alone polyetheretherketone (PEEK) cage and Zero-Profile anchored spacer (Zero-P) for single level anterior cervical discectomy and fusion (ACDF). Methods : We retrospectively reviewed 121 patients who underwent single level ACDF within 2 years (Jan 2011-Jan 2013) in a single institute. Total 50 patients were included for the analysis who were evaluated more than 2-year follow-up. Twenty-nine patients were allocated to the cage group (m : f=19 : 10) and 21 for Zero-P group (m : f=12 : 9). Clinical (neck disability index, visual analogue scale arm and neck) and radiographic (Cobb angle-segmental and global cervical, disc height, vertebral height) assessments were followed at pre-operative, immediate post-operative, post-3, 6, 12, and 24 month periods. Results : Demographic features and the clinical outcome showed no difference between two groups. The change between final follow-up (24 months) and immediate post-op of Cobb-segmental angle (p=0.027), disc height (p=0.002), vertebral body height (p=0.033) showed statistically better outcome for the Zero-P group than the cage group, respectively. Conclusion : The Zero-Profile anchored spacer has some advantage after cage for maintaining segmental lordosis and lowering subsidence rate after single level anterior cervical discectomy and fusion.