Home OALib Journal OALib PrePrints Submit Ranking News My Lib FAQ About Us Follow Us+
 Title Keywords Abstract Author All
Search Results: 1 - 10 of 100 matches for " "
 Page 1 /100 Display every page 5 10 20 Item
 Journal of Applied Sciences , 2009, Abstract: This study was carried out to determine the effect of the impregnation process on screw withdrawal strength in some wood materials. In this regard, the samples prepared from the woods are most commonly used in the furniture industry such as Oriental beech (Fagus orientalis lipsky) (I), European oak (Quercus petreae lipsky) (II) and Scotch pine (Pinus sylvestris lipsky) (III) were impregnated with borax (Bx), boric acid (Ba), borax+boric acid (Ba+Bx), Imersol-aqua (Ia) and Timbercare-aqua (Ta) in accordance with ASTM D 1413, TS 344 and TS 345. The screws 3.5x50 mm (S1) and 4x50 mm (S2) that were connected to the cross surfaces of the impregnated samples were subjected to withdrawal test in accordance with TS EN 13446. As a result, the highest screw withdrawal strength was obtained in European oak (3.675 N mm-2) and the lowest in Scotch pine (2.693 N mm-2) for the wood type. The highest screw withdrawal strength was obtained in S2 (3.363 N mm-2) and the lowest in S1 (3.222 N mm-2) in for the screw diameter. The highest screw withdrawal strength was obtained in II + Bx + S1 (4.193 N mm-2) and the lowest in III + Ba + S1 (2.251 N mm-2) for the interaction of wood type, impregnation material and screw diameter. So, the impregnation process increased the screw withdrawal strength. It can be said that, in the applications, where the pieces are impregnated with Bx and connected with V1 at the cross surface shall display the highest strength.
 Coluna/Columna , 2009, DOI: 10.1590/S1808-18512009000100015 Abstract: objective: more detailed anatomical knowledge of the c2 pedicle is required to optimize and minimize the risk of screw placement. the aim of this study was to evaluate the linear and angular dimensions of the true c2 pedicle using axial ct. methods: ninety three patients (47 males, 46 females mean age 48 years) who had cervical spinal ct imaging performed were evaluated for this study. axial images of the c2 pedicle were selected and the following pedicle parameters were determined: pedicle width (pw, the mediolateral diameter of the pedicle isthmus, perpendicular to the pedicle axis) and pedicle transverse angle (pta, that is, the angle between the pedicle axis and the midline of the vertebral body). results: the overall mean pedicle width was 5.8 1.2mm. the mean pedicle width in males (6.01.3mm) was greater than that in the female subjects (5.6 1.1mm). this difference was not found to be statistically significant (p=.6790). the overall mean pedicle transverse angle was 43.93.9 degrees. the mean pta in males was 43.23.8 degrees, while that in females was 44.73.7 degrees. conclusion: preoperative planning is absolutely mandatory, particularly in determining not only screw trajectory, but in analyzing individual patient anatomy and reception to a c2 pedicle screw.
 Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine , 2012, DOI: 10.1186/1757-7241-20-60 Abstract: Object To compare the Sliding with Non-sliding lag screw of a gamma nail in the treatment of A1 and A2 AO-OTA intertrochanteric fractures. Materials and methods 80 patients were prospectively collected. In each group, AO/OTA 31-A were classified into group A. AO/OTA 31-A2.1 was classified as group B. We classified the A2.2 and A2.3 as group C. According to the set-screw locking formation of Gamma-III, the cases were randomly allocated to Sliding subgroup and Non-sliding subgroup in A, B and C groups. Follow-ups were performed 1, 3, 6 and 12 months postoperatively. Results In the Sliding group, the bone healing rate 3, 6, 12 months postoperatively reached 85.00%, 97.50%, 100% in group A, B and C. Meanwhile, in Non-sliding group, postoperatively, bone healing rate were 90.00%, 95.00% and 97.50% in group A, B and C, respectively. Both differences were not significant. Lower limb discrepancy between Sliding and Non-sliding pattern was significantly different in group C which represent fracture types of AO/OTA 31-A2.2 and A2.3 (0.573 ± 0.019 mm in Non-sliding group, 0.955 mm ± 0.024 mm in Sliding group, P < 0.001 ). Difference of sliding distance among the three groups was significant among group A, B and C: 0.48 mm ± 0.04 mm, 0.62 mm ± 0.07 mm and 0.92 mm ± 0.04 mm (P < 0.001). Differences in average healing time and Harris scores also presented no significance in the three groups. Conclusions As a result, we can conclude that the sliding distance is minimal in Gamma nails and it is related to the comminuted extent of the intertrochanteric area in A1 and A2 AO-OTA intertrochanteric fractures. For treating these kinds of fractures, the sliding of the lag screw of an Gamma nail does not improve any clinical results and in certain cases, such as highly comminuted A1 and A2 fractures, can therefore even benefit from a locked lag screw by tightening the set-screw.
 Glasnik ？umarskog Fakulteta , 2006, DOI: 10.2298/gsf0694257p Abstract: This work presents the method for improvement of direct screw connection performance in conventional particleboard (PB) and oriented strand board (OSB). It is conceived on adhesive insertion into the pilot hole prior to embedment of the screw. The tests were carried out on the PB and OSB, both presenting interior boards and with the same nominal thickness of 18 mm. Particleboard screws of the 5 mm in diameter were inserted in the edge of the board. Pilot hole diameters were 2,5 mm and 3,0 mm and the depth of embedment was 30 mm for all tests. The chosen PVAc adhesive (type 3) with the addition of wood flour as consolidator in the range from 3-10% was inserted into pilot-hole. Tests were also obtained after consequent reassembly of the screw connection in order to examine the ratio of loss in withdrawal forces in such case. It was found that the insertion of PVAc adhesive into the pilot hole and the addition of wood flour have the positive effects on the screw withdrawal force in the tested boards.
 Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.510073 Abstract: Introduction: The indications for intramedullary nail fixation of fractures of the femoral shaft have been greatly expanded by techniques of interlocking nailing. However, distal locking screw fixation remains the most technically demanding and problematic portion of the procedure and maybe responsible for as much as one-half of the exposure of the surgeon’s hands to radiation during the procedure. Objective: This biomechanical study was undertaken to compare the stability of using one distal locking cross screw versus two cross screws in femoral fractures fixed with intramedullary nailing (IMN) system. Materials: A composite model made from a stainless steel IMN (12 mm × 1 mm) was connected to a load cell (Instron machine). Axial forces upto 2 kN (3 times body weight) was applied or until a maximum displacement of 1 mm was reached. The distal locking end of the intramedullary nail was secured with stainless steel cylinders of different dimensions 50 mm × 5 mm, 75 mm × 5 mm and 100 mm × 3 mm to represent the proximal femoral diaphysis, diaphyseo-metaphyseal junction and distal femoral metaphyseal respectively. The distal locking end of the intramedullary nail was attached to the cylinder with a dedicated single or two rods (5 mm diameter), made from stainless steel, to represent the distal locking cross screw. Results: In the 50 mm cylinder, the mean stiffness (±standard deviation) of the system using either single or two screws were similar i.e. 3298 ± 144 N/mm. But in the 75 mm and 100 mm cylinders, the mean stiffness of the fracture model with two distal locking cross screws fixation was 2.059 ± 96 N/mm and 0.816 ± 122 N/mm and with single distal locking cross screw fixation were 0.643 ± 142 N/mm and 0.289 ± 88 N/mm respectively. Conclusion: Single distal locking cross screw fixation provide poorer fracture stability compared to two distal locking cross screws when used to fix distal femoral metaphyseal fractures.
 唐晓军,曹奇,陈亮元,唐国军,杨五洲,李严兵 - , 2015, DOI: 10.7507/1002-1892.20150038 Abstract: 目的对成人尸体枢椎干骨标本进行解剖学测量，探索一种简便、精确的植钉方法，为临床枢椎椎弓根螺钉内固定提供解剖学依据。 方法取60具完整且无畸形的成人尸体枢椎干骨标本，以椎弓根内、外侧缘与侧块交界处连线的中点作纵垂线，经横突后支与下关节突外侧缘交界处作水平线，两线交点偏外1～2 mm处为进钉点，经椎弓根植钉，分别测量椎弓根高度及宽度、最大进钉长度、钉道至椎管和横突孔最短距离、进钉角度等解剖参数，评估枢椎椎弓根螺钉植钉的可行性及安全性。 结果椎弓根上缘、中部、下缘宽度分别为（7.35±0.89）、（5.50±1.48）、（3.97±1.01）mm，椎弓根高度为（9.94±1.16）mm。最大进钉长度为（25.91±1.15）mm，进钉方向与冠状面夹角为（26.95±1.88）°、与矢状面夹角为（22.81±1.61）°。钉道至椎管、横突孔的最短距离分别为（2.72±0.83）mm和（1.98±0.26）mm。 结论分别经椎弓根内、外侧缘与侧块的交界处，以及经横突后支与下关节突外侧缘的交界处作为枢椎椎弓根进钉点坐标的定位标志进行植钉，在解剖形态学方面是安全、可行的。ObjectiveTo determine the entry point and screw implant technique in posterior pedicle screw fixation by anatomical measurement of adult dry samples of the axis so as to provide a accurate anatomic foundation for clinical application. MethodsA total of 60 dry adult axis specimens were selected for pedicle screws fixation. The entry point was 1-2 mm lateral to the crossing point of two lines: a vertical line through the midpoint of distance from the junction of pedicle medial and lateral border to lateral mass, and a horizontal line through the junction between the lateral border of inferior articular process and the posterior branch of transverse process. The pedicle screw was inserted at the entry point. The measurement of the anatomic parameters included the height and width of pedicle, the maximum length of the screw path, the minimum distance from screw path to spinal canal and transverse foramen, and the angle of pedicle screw. The data above were provided to determine the surgical feasibility and screw safety. ResultsThe width of upper, middle, and lower parts of the pedicle was (7.35±0.89), (5.50±1.48), and (3.97±1.01) mm respectively. The pedicle height was (9.94±1.16) mm and maximum length of the screw path was (25.91±1.15) mm. The angle between pedicle screw and coronal plane was (26.95±1.88)° and the angle between pedicle screw and transverse plane was (22.81±1.61)°. The minimum distance from screw path to spinal canal and transverse foramen was (2.72±0.83) mm and (1.98±0.26) mm respectively. ConclusionAccording to the anatomic research, a safe entry point for C 2 pedicle screw fixation is determined according to the midpoint of distance from the junction of pedicle medial and lateral border to lateral mass, as well as the junction between the lateral border of inferior articular process and the posterior branch of transverse process, which is confirmed to be effectively and safely performed using the entry point and screw angle of the present study.
 Alper Aytekin International Journal of Molecular Sciences , 2008, DOI: 10.3390/ijms9040626 Abstract: In this study, screw and nail withdrawal resistance of fir (Abies nordmanniana), oak (Quercus robur L.) black pine (Pinus nigra Arnold) and Stone pine (Pinus pinea L.) wood were determined and compared. The data represent the testing of withdrawal resistance of three types of screws as smart, serrated and conventional and common nails. The specimens were prepared according to TS 6094 standards. The dimensions of the specimens were 5x5x15cm and for all of the directions. Moreover, the specimens were conditioned at ambient room temperature and 65±2% relative humidity. The screws and nails were installed according to ASTM-D 1761 standards. Nail dimensions were 2.5mm diameter and 50 mm length, conventional screws were 4x50mm, serrated screws were 4x45mm and smart screws were 4x50mm. Results show that the maximum screw withdrawal resistance value was found in Stone pine for the serrated screw. There were no significant differences between Stone pine and oak regarding screw withdrawal resistance values. Conventional screw yielded the maximum screw withdrawal resistance value in oak, followed by Stone pine, black pine and fir. Oak wood showed the maximum screw withdrawal resistance value for the smart screw, followed by Stone pine, black pine, and fir. Oak wood showed higher nail withdrawal resistances than softwood species. It was also determined that oak shows the maximum nail withdrawal resistance in all types. The nail withdrawal resistances at the longitudinal direction are lower with respect to radial and tangential directions.
 Alper Aytekin International Journal of Molecular Sciences , 2008, Abstract: In this study, screw and nail withdrawal resistance of fir (Abies nordmanniana), oak (Quercus robur L.) black pine (Pinus nigra Arnold) and Stone pine (Pinus pinea L.) wood were determined and compared. The data represent the testing of withdrawal resistance of three types of screws as smart, serrated and conventional and common nails. The specimens were prepared according to TS 6094 standards. The dimensions of the specimens were 5x5x15cm and for all of the directions. Moreover, the specimens were conditioned at ambient room temperature and 65 ±2% relative humidity. The screws and nails were installed according to ASTM-D 1761 standards. Nail dimensions were 2.5mm diameter and 50 mm length, conventional screws were 4x50mm, serrated screws were 4x45mm and smart screws were 4x50mm. Results show that the maximum screw withdrawal resistance value was found in Stone pine for the serrated screw. There were no significant differences between Stone pine and oak regarding screw withdrawal resistance values. Conventional screw yielded the maximum screw withdrawal resistance value in oak, followed by Stone pine, black pine and fir. Oak wood showed the maximum screw withdrawal resistance value for the smart screw, followed by Stone pine, black pine, and fir. Oak wood showed higher nail withdrawal resistances than softwood species. It was also determined that oak shows the maximum nail withdrawal resistance in all types. The nail withdrawal resistances at the longitudinal direction are lower with respect to radial and tangential directions.
 Yoshihiro Nishiyama Statistics , 2011, DOI: 10.1088/1742-5468/2011/08/P08020 Abstract: A length-N spin chain with the \sqrt{N}(=v)-th neighbor interaction is identical to a two-dimensional (d=2) model under the screw-boundary (SB) condition. The SB condition provides a flexible scheme to construct a d\ge2 cluster from an arbitrary number of spins; the numerical diagonalization combined with the SB condition admits a potential applicability to a class of systems intractable with the quantum Monte Carlo method due to the negative-sign problem. However, the simulation results suffer from characteristic finite-size corrections inherent in SB. In order to suppress these corrections, we adjust the screw pitch v(N) so as to minimize the excitation gap for each N. This idea is adapted to the transverse-field Ising model on the triangular lattice with N\le32 spins. As a demonstration, the correlation-length critical exponent $\nu$ is analyzed in some detail.
 Medical Devices: Evidence and Research , 2008, DOI: http://dx.doi.org/10.2147/MDER.S3747 Abstract: anspedicular screw fixation in the thoracic and lumbar spine with a novel cannulated polyaxial screw system Original Research (8756) Total Article Views Authors: Lutz Weise, Olaf Suess, Thomas Picht, Theodoros Kombos Published Date October 2008 Volume 2008:1 Pages 33 - 39 DOI: http://dx.doi.org/10.2147/MDER.S3747 Lutz Weise, Olaf Suess, Thomas Picht, Theodoros Kombos Neurochirurgische Klinik, Charité – Universit tsmedizin Berlin, Berlin, Germany Objective: Transpedicular screws are commonly and successfully used for posterior fixation in spinal instability, but their insertion remains challenging. Even using navigation techniques, there is a misplacement rate of up to 11%. The aim of this study was to assess the accuracy of a novel pedicle screw system. Methods: Thoracic and lumbar fusions were performed on 67 consecutive patients for tumor, trauma, degenerative disease or infection. A total of 326 pedicular screws were placed using a novel wire-guided, cannulated, polyaxial screw system (XIA Precision , Stryker). The accuracy of placement was assessed post operatively by CT scan, and the patients were followed-up clinically for a mean of 16 months. Results: The total medio-caudal pedicle wall perforation rate was 9.2% (30/326). In 19 of these 30 cases a cortical breakthrough of less than 2 mm occurred. The misplacement rate (defined as a perforation of 2 mm or more) was 3.37% (11/326). Three of these 11 screws needed surgical revision due to neurological symptoms or CSF leakage. There have been no screw breakages or dislocations over the follow up-period. Conclusion: We conclude that the use of this cannulated screw system for the placement of pedicle screws in the thoracic and lumbar spine is accurate and safe. The advantages of this technique include easy handling without a time-consuming set up. Considering the incidence of long-term screw breakage, further investigation with a longer follow-up period is necessary.
 Page 1 /100 Display every page 5 10 20 Item