• Journal of Korean Neurosurgical Society
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• v.50 no.4
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• pp.341-347
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• 2011

Objective : The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. Methods : Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle $30^{\circ}$ to $45^{\circ}$ toward the midline in the transverse plane and $40^{\circ}$ to $50^{\circ}$ cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. Results : There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). Conclusion : Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

• Journal of Korean Neurosurgical Society
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• v.59 no.2
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• pp.91-97
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• 2016

Objective : To investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine. Methods : A three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated. Results : The entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine. Conclusion : The newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study.

• Journal of Biomedical Engineering Research
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• v.21 no.6
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• pp.559-566
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• 2000

Methodology for finite element analysis of vertebral column and pedicle screw system, which circumvents the tremendous difficulties in geometric, material, and structural modeling, is proposed. The simplification is focused on the modeling of the cancellous bone in vertebral body the intervertebral disc. and the instrumented internal fixation devices. Each proposed modeling technique is justified to result in reasonable accuracy. These methods are believed to be suitable for the development of pedicle screw systems, not only because modeling itself is much simpler. but also because reliable empirical data for disc stiffness may be incorporated with little additional effort, and presumably frequent design change may be easily reflected on the analysis.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.167-168
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• 1998

The purpose of this study is to verify the biomechanical characteristics of the custom-made(our) pedicle screws which are designed the different types of shape, pitch, and profile. The results of experiments for our pedicle screw were summarized. 1) The screw of larger outer diameter showed greater holding strength. 2) The holding strength of cylindrical shaped screw was superior to that of conical shaped screw. 3) The holding strength of buttress shape of thread profile showed superior to that of V-shape. 4) The pull out and holding strength of our pedicle screws was superior to that of commercialized screw (Diapason and CD) which is widely used.

• Journal of Korean Neurosurgical Society
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• v.52 no.4
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• pp.359-364
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• 2012

Objective : Transpedicular screw fixation has some disadvantages such as postoperative back pain through wide muscle dissection, long operative time, and cephalad adjacent segmental degeneration (ASD). The purposes of this study are investigation and comparison of radiological and clinical results between interspinous fusion device (IFD) and pedicle screw. Methods : From Jan. 2008 to Aug. 2009, 40 patients underwent spinal fusion with IFD combined with posterior lumbar interbody fusion (PLIF). In same study period, 36 patients underwent spinal fusion with pedicle screw fixation as control group. Dynamic lateral radiographs, visual analogue scale (VAS), and Korean version of the Oswestry disability index (K-ODI) scores were evaluated in both groups. Results : The lumbar spine diseases in the IFD group were as followings; spinal stenosis in 26, degenerative spondylolisthesis in 12, and intervertebral disc herniation in 2. The mean follow up period was 14.24 months (range; 12 to 22 months) in the IFD group and 18.3 months (range; 12 to 28 months) in pedicle screw group. The mean VAS scores was preoperatively $7.16{\pm}2.1$ and $8.03{\pm}2.3$ in the IFD and pedicle screw groups, respectively, and improved postoperatively to $1.3{\pm}2.9$ and $1.2{\pm}3.2$ in 1-year follow ups (p<0.05). The K-ODI was decreased significantly in an equal amount in both groups one year postoperatively (p<0.05). The statistics revealed a higher incidence of ASD in pedicle screw group than the IFD group (p=0.029) Conclusion : Posterior IFD has several advantages over the pedicle screw fixation in terms of skin incision, muscle dissection and short operative time and less intraoperative estimated blood loss. The IFD with PLIF may be a favorable technique to replace the pedicle screw fixation in selective case.

• Journal of Korean Neurosurgical Society
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• v.49 no.6
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• pp.351-354
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• 2011

Objective : This investigation was conducted to evaluate a new, safe entry point for the C2 pedicle screw, determined using the anatomical landmarks of the C2 lateral mass, the lamina, and the isthmus of the pars interarticularis. Methods : Fifteen patients underwent bilateral C1 lateral mass-C2 pedicle screw fixation, combined with posterior wiring. The C2 pedicle screw was inserted at the entry point determined using the following method : 4 mm lateral to and 4 mm inferior to the transitional point (from the superior end line of the lamina to the isthmus of the pars interarticularis). After a small hole was made with a high-speed drill, the taper was inserted with a 30 degree convergence in the cephalad direction. Other surgical procedures were performed according to Harm's description. Preoperatively, careful evaluation was performed with a cervical X-ray for C1-C2 alignment, magnetic resonance imaging for spinal cord and ligamentous structures, and a contrast-enhanced 3-dimensional computed tomogram (3-D CT) for bony anatomy and the course of the vertebral artery. A 3-D CT was checked postoperatively to evaluate screw placement Results : Bone fusion was achieved in all 15 patients (100%) without screw violation into the spinal canal, vertebral artery injury, or hardware failure. Occipital neuralgia developed in one patient, but this subsided after a C2 ganglion block. Conclusion : C2 transpedicular screw fixation can be easily and safely performed using the entry point of the present study. However, careful preoperative radiographic evaluation, regardless of methods, is mandatory.

• Journal of Korean Neurosurgical Society
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• v.46 no.1
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• pp.5-10
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• 2009

Objective: The purpose of this study is to evaluate the effectiveness of unilateral decompression and pedicle screw fixation for the unilateral symptomatic foraminal stenosis. Methods: The study group comprises consecutive 16 patients who underwent unilateral decompression and bone cement augmented pedicle screw fixation from May 2003 to January 2006. The patients were evaluated by visual analog scale (VAS) for pain and the scoring system of the Japanese Orthopedic Association (JOA) for low back pain. The result of surgery was also evaluated with McNab's classification. Excellent or good outcome was considered as successful. The patients were followed at postoperative 1 month, 3 month, 6 month, and 1 year with standing AP and lateral films. Results: The average VAS and JOA score of the 16 patients were 7.8(range, 6-9) and 5.8(range, 3 - 10) before surgery and 2.2(range, 0 - 5)and 12.3(range, 9 - 15) at the time of last follow up. Both VAS and JOA score improved significantly after the surgery (p<0.05, t-test). All patients improved after the operation and no revision surgery was required. No metal failure or pseudoarthrosis was observed during the follow-up. The success rate was 87.5%. Conclusion: Our data suggest that unilateral decompression and pedicle screw fixation for the unilateral symptomatic foraminal stenosis is an effect method for obtaining satisfactory clinical outcome. Its possible advantage is shorter operation time and reduced surgical extent. We believe that the reduced stiffness of unilateral fixation was compensated by pedicle screw augmentation and interbody fusion.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1775-1780
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• 2011

In this paper, it is analyzed about the mechanical characteristics of pedicle screw system which is a artificial implant for surgery to treatment serious lumbar vertebra diseases. The disk of lumbar vertebra to be fixed by pedicle screw system shows regressive phenomena. But if flexible rod, to give a flexibility(under 6 degree) to fixable disk is applied, it can protect against the degeneration of disk. This research is carried out a mechanical characteristic of pedicle screw system used flexible rod through finite elements analysis, and then flexible rod system was verified about safe movement through compression, tension and torsion test which is the pedicle screw system official recognition test(ASTM F 1717).

• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.17-26
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• 2002

The purpose of this study was to investigate the important Parameters of the Pedicle screw by estimating the mechanical characteristics of screws under static and dynamic loads. Methodology for estimating Parameters under static load was proposed. It was also shown that the fatigue life of the one-level system could be increased by changing the shape of screws. Load parameters of the single pedicle screw were friction force. bending moment. and holding force. The test results of the one-level system could be inferred from teat results of the sin91e screw under bending force Fatigue life of the one-level system with flexible rod was longer than that of the upper Part test without rod . Considering the drop of flexibility of the rod due to muscles and ligament, fatigue life of the one-level system could be estimated b? that of the single screw.

• Journal of Korean Neurosurgical Society
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• v.63 no.6
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• pp.777-783
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• 2020

Objective : To compare the accuracy and breach rates of freehand (FH) versus navigated (NV) pedicle screws in the thoracic and lumbar spine in patients with metastatic spinal tumors. Methods : A retrospective review of adult patients who underwent pedicle screw fixation in the thoracic or lumbar spine for metastatic spinal tumors between 2012 and 2018 was conducted. Breaches were assessed based on the Gertzbein and Robbins classification and only screws placed >4 mm outside of the pedicle wall (lateral or medial) were considered breached. Results : A total of 62 patients received 547 pedicle screws (average 8 per patient) - 34 patients received 298 pedicle screws in the FH group and 28 patients received 249 screws in the NV group. There were 40/547 breaches, corresponding to a breach and accuracy rate of 7.3% and 92.7%, respectively. The breach rate was 9.7% in the FH group and 4.4% in the NV group (chi-squared test, p=0.017); this corresponded to an accuracy rate of 90.3% and 95.6%, respectively. Only one patient from the overall cohort (in the FH group) required revision surgery due to a medial breach abutting the spinal cord (1.6% of all patients; 2.9% of FH patients); no patient suffered organ, vessel, or neurological injury from screw breaches. Conclusion : Navigated pedicle screw placement in patients with metastatic spinal tumors has a significantly higher radiographic accuracy compared to the FH technique. However, the revision surgery was low and no patient suffered from clinically-relevant breach. Navigation also offers the advantage of real-time localization of spinal tumors and aids in targeting and resection of these lesions.