• Journal of Korean Neurosurgical Society
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• v.42 no.3
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• pp.179-183
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• 2007

Objective : Posterior arthrodesis in atlantoaxial instability has been performed using various posterior C1-2 wiring techniques. Recently, transarticular screw fixation (TASF) technique was introduced to achieve significant immediate stability of the C1-2 joint complex. The purpose of this study is to assess the clinical outcomes associated with posterior C1-2 TASF for the patient of atlantoaxial instability. Methods : We retrospectively reviewed data obtained from 17 patients who underwent C1-2 TASF and supplemented Posterior wiring technique (PWT) with graft between 1994 and 2005. There were 8 men and 9 women with a mean age of 43.5 years (range, 12-65 years). An average follow-up was 26 months (range, 15-108 months). Results : Successful fusions were achieved in 16 of 17 (94%). The pain was improved markedly (3 patients) or resolved completely (14 patients). There was no case of neurological deterioration, hypoglossal nerve injury, or vertebral artery injury. Progression of spinal deformity, screw pullout or breakage, and neurological or vascular complications did not occur. Conclusion : The C1-2 TASF with supplemental wiring provided a high fusion rate. Our result demonstrates that C1-2 TASF supplemented by PWT is a safe and effective procedure for atlantoaxial instability. Preoperative evaluation and planning is mandatory for optimal safety.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.114-118
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• 2017

Purpose: The aim of this study was to investigate the effects of a titanium component for the zirconia abutment in the internal connection implant system on screw loosening under thermocycling conditions. Materials and Methods: Internal connection titanium abutments and external connection zirconia abutments with titanium sockets were connected respectively to screw-shaped internal connection type titanium implants with 30 Ncm tightening. These implant-screw-abutment assemblies were divided into two groups of five specimens each; titanium abutments as control and zirconia abutments with titanium sockets as experimental group. The specimens were subjected to 2,000 thermocycles in water baths at $5^{\circ}C$ and $55^{\circ}C$, with 60 seconds of immersion at each temperature. The removal torque values (RTVs) of the abutment screws of the specimen were measured before and after thermocycling. RTVs pre- and post-thermocycling were investigated in statistics. Results: There was not screw loosening identified by tactile and visual inspection in any of the specimens during or after thermocycling. The mean RTV difference for the control group and the experimental group were $-1.34{\pm}2.53Ncm$ and $-1.26{\pm}2.06Ncm$, respectively. Statistical analysis using an independent t-test revealed that no significant differences were found in the mean RTV difference of the groups (P > 0.05). Conclusion: Within the limitations of this in vitro study, the titanium socket for the zirconia abutment did not show a significant effect on screw loosening under thermal stress compared to the titanium abutment in the internal connection implant.

• 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.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.23-26
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• 1995

The objectives of the present study are 1)to find the effect of the diameter of transpedicular screws on their fixational strength in pedicles under static pull-out loading, 2)to determine the biomechanical correlation between the pedicle diameter and the screw diameter, and 3)to find the effects of other factors in the screw design, such as materials, screw pitch, thread height and shape on their fixational strength. Biomechanical tests (Test I) were performed to evaluate the effect of the screw diameter on pull-out strength by using 60 porcine pedicls and six groups of custom-made pedicle screws with different diameters (the major and the minor diameter of the screws used in the testing varied from 4mm upto 9mm and from 3mm upto 8mm, respectively) while all other factors (materials, screw pitch, thread height and shape etc.) were fixed. In Test II, by using 61 porcine pedicles, the relationship between the ratio of the pedicle diameter and the screw diameter(=aspect ratio) of the custum-made screw and the pull-out strength of the screw was investigated. Test III was performed with 94 porcine pedicles and 8 different types of the commercial screws from 6 major productors in order to determine the effect of the screw diameter, pitch and the thread shape on the pull-out strength of the screw, respectively. The results of Test I showed that the axial pull-out resistance of the screw could be increased prportionaly to the screw diameter(P<0.05). But this increase in the pull-out resistance did not found when the screws of 4mm or 9mm in the diameter were employed. It was found from the results of Test II that the screws had its maximum pull-out resistant force when the aspect ratio ranging 40 - 69% (P<0.05). based on the results for the major diameter against the minor diameter of screw, the maximal pull-out resistance was found at 60-65% (P<0.05). According to these biomechanical testing results, it seems that the screw with a moderately large pitch is more desirable and the buttress-shaped screw can provide stronger fixation than the V-shape one can, if other designal factor and conditions were fixed.

• The Korean Journal of Food And Nutrition
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• v.13 no.6
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• pp.547-552
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• 2000

Corn grits spiked with fumonisin B$_1$(FB$_1$) at a level of 5 $\mu$g/g were extrusion cooked in a co-rotating twin screw extruder at different temperatures(140, 160, 18$0^{\circ}C$) and screw speed(80, 100, 120 rpm). About 41~45% of the spiked FB$_1$ was lost when the corn grits were extruded. Both the barrel temperature and the screw speed. however, did not significantly affect the FBI reduction in extruded corn grits. More reduction of FB$_1$ was found in the presence of glucose than with fructose or sucrose when the corn grits were extruded with sugar at 14$0^{\circ}C$, 120 rpm. About 51, 34 and 19% of spiked FB$_1$ were remained in extruded corn grits with glucose at levels of 2.5%, 5%, and 7.5%, respectively.

• Journal of Korean Neurosurgical Society
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• v.42 no.4
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• pp.311-316
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• 2007

Objective : The objective of this study is to investigate the safety, surgical efficacy, and advantages of a polyaxial screw-rod system for posterior occipitocervicothoracic arthrodesis. Methods : Charts and radiographs of 32 patients who underwent posterior cervical fixation between October 2004 and February 2006 were retrospectively reviewed. Posterior cervical polyaxial screw-rod fixation was applied on the cervical spine and/or upper thoracic spine. The surgical indication was fracture or dislocation in 18, C1-2 ligamentous injury with trauma in 5, atlantoaxial instability by rheumatoid arthritis (RA) or diffuse idiopathic skeletal hyperostosis (DISH) in 4, cervical spondylosis with myelopathy in 4, and spinal metastatic tumor in 1. The patients were followed up and evaluated based on their clinical status and radiographs at 1, 3, 6 months and 1 year after surgery. Results : A total of 189 screws were implanted in 32 patients. Fixation was carried out over an average of 3.3 spinal segment (range, 2 to 7). The mean follow-up interval was 20.2 months. This system allowed for screw placement in the occiput, C1 lateral mass, C2 pars, C3-7 lateral masses, as well as the lower cervical and upper thoracic pedicles. Satisfactory bony fusion and reduction were achieved and confirmed in postoperative flexion-extension lateral radiographs and computed tomography (CT) scans in all cases. Revision surgery was required in two cases due to deep wound infection. One case needed a skin graft due to necrotic change. There was one case of kyphotic change due to adjacent segmental degeneration. There were no other complications, such as cord or vertebral artery injury, cerebrospinal fluid leak, screw malposition or back-out, or implant failure, and there were no cases of postoperative radiculopathy due to foraminal stenosis. Conclusion : Posterior cervical stabilization with a polyaxial screw-rod system is a safe and reliable technique that appears to offer several advantages over existing methods. Further biomechanical testings and clinical experiences are needed in order to determine the true benefits of this procedure.

• The Korean Journal of Food And Nutrition
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• v.7 no.2
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• pp.137-143
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• 1994

To optimize extrusion cooking condition of single screw extuder for production of puffed rice extrudate using response surface methodology (RSM), moisture content, barrel temperature and screw speed were determined from contour maps, showing relationship between dependent (hardness, expansion ratio, water absorption index, water solubility Index, degree of gelatinization) and independent variables. Optimum operational conditions for production of puffed rice extrudate with suitable quality properties were moisture content 17%, barrel temperature 1$25^{\circ}C$ and screw speed 210 rpm, respectively.

• Journal of Korean Neurosurgical Society
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• v.37 no.5
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• pp.380-382
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• 2005

We report a case of atlantoaxial subluxation with bilateral high-riding vertebral artery with narrow isthmus. Because of the potential risk of bilateral vertebral artery injury, we performed atlantoaxial fixation using rod and screw instead of transarticular screw fixation. Although postoperative computed tomography reconstruction demonstrated slight breach of bilateral vertebral artery groove, postoperative angiography showed no evidence of vertebral artery injury. Though technically demanding, atlantoaxial fixation using rod and screw can be a one of the treatment options for atlantoaxial instability with bilateral high riding vertebral artery.

• Clinics in Shoulder and Elbow
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• v.2 no.2
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• pp.133-137
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• 1999

Purpose: There are so many different methods with the their own advantages and disadvantages for acute AC dislocation and distal unstable clavicle fracture. We evaluated the usefulness of temporary Bosworth's coracoclavicular fixations using the cannulated screw and reviewed our clinical results. Materials and Methods: We evaluated 34 cases of temporary coracoclavicular fixations with cannulated screw and washer for acute AC dislocation(25cases in the Type V, Ⅲ) and distal unstable clavicle fracture(9cases in the Type ⅡB, Ⅱ+Ⅲ). All cases were fixed by the same techniques, guided cannulated screw under C-arm after the repair of the CC ligament within 1 week. Bases on the regular check, screws were removed at the 6-12 weeks under local anesthesia. The final clinical and radiological results(average 14 months follow-up) were rated with the UCLA scale. Results : All shoulders were gained nearly full ROM passively at the 3-4 weeks. The overall satisfactory resuIts(excellent or good) were achieved 88%(22/25) in the acute AC dislocation and all in the distal unstable clavicle fracture. There were no definite complications except three initial fixations loosening. Conclusion: Temporary Bosworth's coracoclavicular fixation using the cannulated screw with guided pin was simple precedure and provided enough initial stability for acute AC dislocation and distal unstable clavicle fracture.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.157-169
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• 2009

The aim of this study was to evaluate effect of implant abutment screw coating treatment on joint stability, investigating mechanical properties of these. For this study used $ExFeel^{(R)}$ external hexed implant system and $15mm{\times}1mm$ discs. Experimental group was $1{\mu}m$ TiN, TiCN, TiC coated abutment screws and discs. To know mechanical property, i evaluated adhesion strength, surface hardness, using disc, corrosion test using screw. The results were as follows : rotation angle of coated screws increased than that of non-coated screw because of lower friction coefficient, especially TiC coated screw group had the largest value, but removal torque decreased in all coated screws (p<0.05). Torque loss before and after fatigue test was the smallest in TiC-coated screws, and the largest in non-coated screws (p<0.05), and there was no statistically significant difference between dry condition and wet condition of screws because of higher surface hardness and lower friction coefficient. From the above results, TiN, TiCN, TiC coating group had high abrasion resistance, especially TiC coated group which had low torque-consuming, high rotation angle as low friction coefficient will be considered to influence on implant abutment screw joint stability positively.