Academic literature on the topic 'Lag screw effect'
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Journal articles on the topic "Lag screw effect"
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TZENG, CHUNG-YUH, KUI-CHUO HUANG, YUN-CHE WU, CHU-LING CHANG, KUAN-RONG LEE, and KUO-CHIH SU. "BIOMECHANICAL EFFECT OF DIFFERENT LAG SCREW LENGTHS WITH DIFFERENT BARREL LENGTHS IN DYNAMIC HIP SCREW SYSTEM: A FINITE ELEMENT ANALYSIS STUDY." Journal of Mechanics in Medicine and Biology 17, no. 01 (February 2017): 1750008. http://dx.doi.org/10.1142/s0219519417500087.
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The dynamic hip screw (DHS) system is commonly used to treat intertrochanteric fracture of the hip joint. Breakage of the lag screw was noted in clinical practice and the length of lag screw as well as the length of the side plate in the DHS system appeared to play a role in the risk of breakage. Thus, the aim of this study was to investigate the biomechanical effect of different lag screw lengths and barrel plate lengths in the DHS implant system by finite element analysis (FEA). Four FEA simulation models were created according to different lengths of lag screw (79[Formula: see text]mm and 63[Formula: see text]mm) and different lengths of barrel side plate (43[Formula: see text]mm and 37[Formula: see text]mm). The von Mises stress was used as the observation indicator. The results showed that the maximum tensile stress on the long lag screw was slightly greater than that of the shorter lag screw. Use of a shorter barrel side plate may also cause high stress between the lag screw and the barrel side plate. This finding provides biomechanical reference data that may be of value to orthopedic surgeons with respect to choice of implant size and length in the treatment of intertrochanteric fracture with a DHS system to prevent complications such as implant failure caused by broken lag screws.
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Quinn, Robert, Anna Adrian, Martin Owen, Mark Bush, and Francisco Silveira. "Evaluation of the use of intra-operative radiology for open placement of lag screws for the stabilization of sacroiliac luxation in cats." Veterinary and Comparative Orthopaedics and Traumatology 30, no. 01 (2017): 69–74. http://dx.doi.org/10.3415/vcot-15-12-0201.
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SummaryObjectives: To assess the effect of intra- operative radiology on the quality of lag screw insertion for the management of sacroiliac joint luxations in cats.Methods: In this retrospective single-centre study, the surgical, anaesthetic and imaging records of 40 screws (32 cats) placed with lag effect for management of sacroiliac luxation were reviewed. Postoperative radio-graphs were assessed for sacroiliac joint reduction, screw position, and sacral width purchased by each screw. Cases were divided into two groups according to the use of (IOR) or the absence of intra-operative radiology (NIOR).Results: A total of 23 lag screws were placed with the aid of intra-operative radiology and 17 without. Three of the 23 screws placed in the IOR group exited the sacrum as opposed to eight of 17 screws in the NIOR group (p = 0.03). Mean sacral width purchased by the screws in the IOR group (70.8%) was also significantly higher (p = 0.002) than in the NIOR group (54.6%). Mean general anaesthetic times for unilateral and bilateral screw placement for the IOR group and NIOR group were not significantly different.Clinical significance: The use of intra-operative radiology can significantly improve the quality of lag screw insertion for the stabilization of sacroiliac luxations in cats, which should lead to a reduced incidence of postoperative screw loosening.
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Chang, Ya-Pei, Chi-Yuan Ho, Chao-Chang Chen, and Lih-Seng Yeh. "Biomechanical Comparison between Preloaded Position Screw and Lag Screw Fixations for Their Compressive Effects in a Porcine Rib Fracture Model." Veterinary and Comparative Orthopaedics and Traumatology 31, no. 03 (May 2018): 182–87. http://dx.doi.org/10.1055/s-0038-1639596.
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Objectives The aim of this study was to compare the compressive effect between preloaded position screws and lag screws in fracture fixation. Methods Pairs of semi-cylindrical bone fragments were created on a porcine rib model to simulate fractured bones. The compressive forces of fracture fixation generated by preloaded position screws (P group) and conventional lag screws (L group) were recorded by a film stress sensor. In the P group, a pair of Angus bone holding forceps was used to compress the interfragmentary interface until reaching the preloading force of 1.3 MPa. Similar preloading procedure was applied on lag screw fixations to explore its potential of additional compressive force. Results With 1.3 MPa preloading force and 0.2 Nm screw insertion torque force, the interfragmentary compressive force of P group was similar to that of L group. When the insertion torque force was increased to 0.4 Nm, all screws in the L group failed due to thread stripping. When screws in the P group were installed under 0.4 Nm torque and in the L group under 0.2 Nm torque, the P group generated significantly greater compressive force. With preloading device applied on lag screw installation, it did not further increase the interfragmentary compressive force. Clinical Significance Compared with lag screws, preloaded position screws tolerated greater torque in screw installation and provided greater interfragmentary compressive force. The study suggests the applicability of preloaded position screws in fracture fixation requiring interfragmentary compression.
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Chao, Ching-Kong, Chun-Ching Hsiao, and Po-Quang Chen. "Optimal Distal Screw Alignment in the Gamma Nail." Journal of Mechanics 18, no. 2 (June 2002): 103–8. http://dx.doi.org/10.1017/s1727719100002069.
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AbstractThe effect of stress distribution due to the changes of the distal screw alignment in relation to the Gamma nail and the femoral shaft is thoroughly studied in this paper. Failure of the Gamma nail composite occurs through the cranial aperture of the distal screws and the insertion hole for the lag screw due to nonunion, delayed-union and continued weight-bearing. A three-dimensional finite element model was used to study the fractured femur, the Gamma nail, the lag screw and the distal locking screws. The first and the second distal screws were inserted into the Gamma nail in four different configurations. We found that the stress of the Gamma nail composite was substantially reduced with the two screws configured in the anterior to posterior direction. This alignment can bear greater loading in the more demanding fracture types. In the subtrochanteric fracture or the comminuted fractures at the proximal femur, the optimal alignment of the two distal screws was in the anterior to posterior direction.
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WANG, CHENG-CHI, CHENG-HUNG LEE, KUN-HUI CHEN, CHIEN-CHOU PAN, and KUO-CHIH SU. "EFFECTS OF DIFFERENT LATERAL FEMORAL WALL THICKNESSES IN INTERTROCHANTERIC HIP FRACTURE TREATED WITH DYNAMIC HIP SCREW." Journal of Mechanics in Medicine and Biology 19, no. 02 (March 2019): 1940022. http://dx.doi.org/10.1142/s0219519419400220.
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Dynamic hip screw (DHS) is commonly used for stable-type intertrochanteric hip fractures. The importance of lateral femoral wall has been mentioned while treating intertrochanteric hip fractures with DHS. The aim of this study was mainly to investigate the biomechanical effect of different thickness of lateral femoral wall using finite element analysis (FEA). This study constructed FEA simulation models for five different lateral femoral wall thicknesses, and demonstrated the stress distribution on the femoral bone, the cortical screws, the cancellous bone around the lag screw, and the lag screw. The main results showed that when the DHS is implanted, less stress will be distributed at the implantation site on the femur due to the stress-shielding effect. The stress on the cortical screws will be greater at the junction of the cortical screws and the cortical bone. Intertrochanteric hip fractures with a thinner lateral wall thickness may cause higher stress on the femur after DHS is implanted.
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Wang, Cheng-Chi, Cheng-Hung Lee, Ning-Chien Chin, Kun-Hui Chen, Chien-Chou Pan, and Kuo-Chih Su. "Biomechanical analysis of the treatment of intertrochanteric hip fracture with different lengths of dynamic hip screw side plates." Technology and Health Care 28, no. 6 (November 17, 2020): 593–602. http://dx.doi.org/10.3233/thc-202248.
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BACKGROUND: Dynamic hip screw (DHS) is a common implant used to treat stable-type intertrochanteric hip fractures. There are many factors that can affect the success rate of the surgery, including the length of side plates. It is therefore important to investigate the biomechanical effect of different DHS side plates on bones. OBJECTIVE: In order to reduce the likelihood of an implant failure, the aim of this study was to use finite element analysis (FEA) to investigate and understand the effect of side plates with different lengths in DHS. METHODS: In this FEA study, a 3D model with cortical bone, cancellous bone, side plate, lag screw, and cortical screws to simulate the implantation of DHS with different lengths of side plate (2-hole, 4-hole, and 6-hole) for intertrochanteric hip fractures was constructed. The loading condition was used to simulate the force (400 N) on the femoral head and the stress distribution on the lag screw, side plate, cortical screws, and femur was measured. RESULTS: The highest stress points occured around the region of contact between the screw and the cortical bones. The stress on the femur at the most distal cortical screw was the greatest. The shorter the length of the side plate, the greater the stress on the cortical screws, resulting in an increased stress on the femur surrounding the cortical screws. CONCLUSIONS: The use of DHS with 2-hole side plate may increase the risk of side plate pull-out. The results of this study provide a biomechanical analysis for selection of DHS implant lengths that can be useful for orthopaedic surgeons.
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Sivakumar, Arjun, Dominic Thewlis, Andreas Ladurner, Suzanne Edwards, and Mark Rickman. "Proximal Femoral Nail Unlocked versus Locked (ProFNUL): a protocol for a multicentre, parallel-armed randomised controlled trial for the effect of femoral nail mode of lag screw locking and screw configuration in the treatment of intertrochanteric femur fractures." BMJ Open 10, no. 2 (February 2020): e032640. http://dx.doi.org/10.1136/bmjopen-2019-032640.
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IntroductionIntertrochanteric fractures are common fragility injuries in the elderly. Surgical fixation using intramedullary devices are one of the widely used management options. To date, evidence demonstrating the effects of lag screw configuration and the mode of lag screw locking in these devices is lacking. The purpose of this study is to investigate whether the lag screw configuration (single vs integrated dual interlocking screw) and the mode of lag screw locking (static vs dynamic) of a femoral nail device result in differences in clinical and functional outcomes.Methods and analysisA multicentre, pragmatic, single-blinded randomised controlled trial (RCT) with a three-arm parallel group design is proposed. Nine-hundred patients with intertrochanteric fractures (A1 and A2 AO/OTA) will be randomised to fracture treatment using a Gamma3 nail (Stryker; proximally dynamic) or a Trigen Intertan nail (Smith & Nephew) in a dynamic or static lag screw configuration. The primary outcome measure consists of radiological evidence of construct failure within 6 months following surgery, with failure being defined as breakage of the femoral nail or distal locking screw, a change in tip-apex distance of more than 10 mm or lag screw cut-out through the femoral head. Secondary outcomes include surgical data (operation time, fluoroscopy time), complications (surgical site infection, reoperation, patient death), return to mobility and home circumstances, functional independence, function and pain. Patients who are able to walk independently with or without a mobility aid and are able to answer simple questions and follow instructions will be asked to participate in three dimensional gait analysis at 6 weeks and 6 months to assess hip biomechanics from this cohort. Additional secondary measures of gait speed, hip range of motion, joint contact and muscle forces and gross activity monitoring patterns will be obtained in this subgroup.Ethics and disseminationThe Central Adelaide Local Health Network Human Research Ethics Committee has approved the protocol for this RCT (HREC/17/RAH/433). The results will be disseminated via peer-reviewed publications and presentations at relevant conferences.Trial registration numberACTRN12618001431213.
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Park, Jin, Jung Min Shin, Do Kyung Lee, Sung-Sahn Lee, Seung Ha Paik, and Byung Hoon Lee. "The Effect of Synthetic Osteoconductive Bone Graft Material for Augmentation of Internally Fixed Unstable Trochanteric Fractures." BioMed Research International 2019 (March 19, 2019): 1–8. http://dx.doi.org/10.1155/2019/5879089.
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This study aimed to evaluate whether the augmentation of CaP into the femoral head around the lag screw results in superior clinical and radiological outcomes of treatment of unstable trochanteric fractures using an intramedullary (IM) implant. Fifty-six consecutive patients with unstable trochanteric fractures who had been surgically treated with IM devices between 2014 and 2016 were prospectively reviewed and randomly divided into two groups based on the use of CaP degradable cements: 28 patients were assigned to the CaP group, while the other 28 patients were assigned to the control group (no use of CaP). Clinical evaluations and radiological analyses were conducted during a minimum of 2-year follow-up. No significant differences in the mean visual analogue scale for the hip pain scores and modified Harris Hip Scores were found between the CaP group and the controls at postoperative 2 months and 2 years. However, earlier walker ambulation was possible in the CaP group (10 ± 9 days) compared to the control group (13 ± 12 days) (P = 0.02). In radiological analysis, the CaP group showed significantly lower difference between tip-apex distance measured immediately after surgery and that measured at one-year follow-up compared to the control group (P = 0.012). No screw cut-out occurred in the CaP group, while one patient in the control group was reoperated for screw cut-out. The CaP augmentation into the femoral head around lag screw can reduce lag screw penetration, prevent screw cut-out beyond the femoral head, and facilitate early ambulation in elderly patients with unstable trochanteric fractures.
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Pallis, Mark P., David N. Pressman, Kenneth Heida, Tyler Nicholson, and Susan Ishikawa. "Effect of Ankle Position on Tibiotalar Motion With Screw Fixation of the Distal Tibiofibular Syndesmosis in a Fracture Model." Foot & Ankle International 39, no. 6 (March 30, 2018): 746–50. http://dx.doi.org/10.1177/1071100718759966.
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Background: Anatomic reduction and fixation of the syndesmosis in traumatic injuries is paramount in restoring function of the tibiotalar joint. While overcompression is a potential error, recent work has called into question whether ankle position during fixation really matters in this regard. Our study aimed to corroborate more recent findings using a fracture model that, to our knowledge, has not been previously tested. Methods: Twenty cadaver leg specimens were obtained and prepared. Each was tested for tibiotalar motion under various conditions: intact syndesmosis, intact syndesmosis with lag screw compression, pronation external rotation type 4 (PER-4) ankle fracture with syndesmotic disruption, and single-screw syndesmotic fixation followed by plate and screw fracture and syndesmotic screw fixation. In each situation, the ankle was held in alternating plantarflexion and dorsiflexion when inserting the syndesmotic screw with the subsequent amount of maximal dorsiflexion being recorded following hand-tight lag screw fixation. Results: While ankle range of motion increased significantly with creation of the PER-4 injury, under no condition was there a statistically significant change in maximal dorsiflexion angle. Conclusion: Ankle position during distal tibiofibular syndesmosis fixation did not limit dorsiflexion of the ankle joint. Clinical Relevance: Our findings suggest that maximal dorsiflexion during syndesmotic screw fixation may not be necessary.
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Huang, Tsan-Wen, Tien-Yu Yang, Kuo-Chin Huang, Kuo-Ti Peng, Mel S. Lee, and Robert Wen-Wei Hsu. "Effect of Teriparatide on Unstable Pertrochanteric Fractures." BioMed Research International 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/568390.
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We retrospectively analyzed the radiographic and clinical outcomes of unstable pertrochanteric fractures (AO/OTA 31-A2) in 44 patients who underwent dynamic hip screw (DHS) fixation and compared the results with 29 patients who received teriparatide in addition to DHS fixation. A significantly shorter time for fracture healing was recorded in the teriparatide-treated group than in the control group. Rates of lag screw sliding, femoral shortening, and varus collapse were all significantly reduced in the teriparatide-treated group. There were no significant differences with regard to superficial wound infection, pneumonia, urinary tract infection, mortality, malunion, and cutting of the lag screw. The mean overall mobility scores were significantly better in the teriparatide-treated group at 3 and 6 months (P<0.001andP<0.001, resp.) but not at 12 months or the last follow-up. The pain scores were also significantly better in the teriparatide-treated group at 3 and 6 months (P=0.040andP=0.041, resp.) but not at 12 months or the last follow-up. Teriparatide improves radiographic outcomes and yields better clinical outcomes at 3 and 6 months postoperatively. The improvement in union time may be important for elderly populations with unstable pertrochanteric fractures to enable them to return to daily activities and reduce morbidity and mortality.
Dissertations / Theses on the topic "Lag screw effect"
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Ehlers, Hendrik Petrus. "Lag screw effect on the biomechanical torsion stability in the I.S.I monocortical mandible angle system." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/30368.
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In a recent in vitro biomechanical stability study by F.J. Jacobs, a unique, patented inclined screw insertion (I.S.I.) mandibular angle, intra-oral trauma-plate was evaluated for torsion and compression stability and compared to conventional plating of simulated angle fractures in polyurethane mandibular replicas. This in vitro comparative pilot study is an extension of the above-mentioned study. Similar I.S.I. mini-plates with 45º inclined screw holes in quadrant 3 (Fig 1), were used but in the one sample 13mm-long lag screws were used to transect the fracture lines where in the other group non-lagging screws of similar length were used to fixate simulated mandibular angle fractures in polyurethane mandible replicas. A uniquely designed and manufactured jig, incorporated in a Zwick machine, was utilized to apply torsion forces within clinical relevant load values. The load-displacement values for torsion forces was determined and compared for the two groups. It was established that 5 lag screws significantly improved the torsion stability of the lag-plate group to that of the non-lag group. During the stability testing, two factors were identified, which had a critical influence on the compression generated by the lag screw between the fracture fragments. An adequate amount of bone must be maintained between the first screw hole, directly distal to the fracture line, and the fracture line. All screws must be inserted in the correct sequence in order to insure sufficient compression between the fracture fragments as a result of the lag-effect. AFRIKAANS : In `n onlangse in vitro studie deur F.J. Jacobs, is `n gepatenteerde, unieke geanguleerde miniplate, waarvan die skroefgate geanguleer is, die sg. Inklineerde Skroef Inplasing (I.S.I.) kaak-hoek, intra-orale traumaplaat geevalueer vir torsie en kompressie stabiliteit en vergelyk met konvensionele plate op gesimuleerde kaakhoek frakture in poli-uretaan mandibular replikas. In hierdie in vitro loodstudie, is I.S.I. miniplate met skroefgate wat teen 45º geanguleer is, gebruik in kombinasie met `n enkele 13mm lange grypskroef (“lag screw”) om gesimuleerde kaakhoek frakture in poli-uretaan mandibula replikas te fikseer. Deur gebruik te maak van `n spesiaal ontwerpte en vervaardigde monterings-apparaat wat binne in `n Zwick masjien geïnkorporeer word, is die I.S.I gefikseerde replikas onderwerp aan torsie kragte, binne klinies relevante ladingswaardes. Die verplasings en ladingswaardes is geregistreer en vergelyk met identiese I.S.I miniplate sonder `n grypskroef. Die loodstudie resultate het getoon dat die frakture wat gefikseerd is met die I.S.I. miniplaat-grypskroef kombinasie betekenisvol beter stabiliteit toon as die frakture wat met slegs die miniplaat, sonder `n grypskroef, gefikseerd is vir klinies relevante ladingsen verplasingswaardes. Tydens biomeganiese toetsing van die mandibula replikas, is twee faktore wat `n kardinale rol speel in die stabiliteit wat verkry word deur `n miniplaat grypskroef kombinasie te gebruik, geïdentifiseer. Voldoende hoeveelheid been tussen die eerste skroefgat, direk distaal van die fraktuurlyn, en die fraktuurlyn asook die korrekte volgorde waarin die skroewe geplaas word, moet gehandhaaf word om maksimale kompressie van die fragmente deur die grypskroef te verseker. Deur `n I.S.I miniplaat, met geanguleerde skroefgate van 45º, te kombineer met `n grypskroef, kan die stabiliteit van die gefikseerde mandibulere kaakhoek betekenisvol verbeter word en verleen dit meer stabiliteit wanneer vergelyk word met frakture gereduseer met `n I.S.I miniplaat sonder grypskroef plasing.Dissertation (MSc)--University of Pretoria, 2010.
Maxillo-Facial and Oral Surgery
unrestricted
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Ramskill, Thomas Edward. "Effect of Cracking on Lag Bolt Performance." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28643.
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This dissertation presents the results of testing to determine the load-slip characteristics of single-shear single lag screw connections subjected to monotonic lateral loading parallel to grain. Of particular importance was the comparison of experimental capacity and 5% offset yield load resistances to load resistances as predicted by the American Forest & Paper Association's (AF&PA) publication General Dowel Equations for Calculating Lateral Connection Values, Technical Report 12 (TR-12). Additionally some other tests were conducted, including fracture, tension strength perpendicular-to-grain, lag screw connection inking, dowel embedment, specific gravity and moisture content. The results for the testing program are presented.
Four hundred and forty eight lateral tests were conducted on lag screw connections. Each connection was comprised of a 2 x 6 x 14 in. long wood main member, 1/4 in. thick steel side plate, and a single lag screw. The parameters of interest were specific gravity, lag screw diameter, and pilot hole diameter. Two species of wood, Douglas-fir and spruce-pine-fir, three lag screws diameters, and three pilot hole diameters for each species of wood were implemented.
Models were developed to predict lag screw connection capacity and 5% offset yield and are contained herein. Models were based on results from connection and inking tests and mechanical analysis. Recommendation for ASD and LRFD design values were derived from connection test results for connections that used AF&PA's National Design Specification for Wood Construction (NDSb) specified pilot holes. Using fracture mechanics results, work was performed to determine the effective load required to crack and separate fracture surfaces of wood main members due to the installation of lag screws with varying pilot hole diameters.Ph. D.
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Ehlers, Hendrik Petrus. "Lag screw effect on the biomechanical torsion stability in the I.S.L monocortical mandible angle system." Diss., 2009. http://hdl.handle.net/2263/30368.
Full textAbstract:
In a recent in vitro biomechanical stability study by F.J. Jacobs, a unique, patented inclined screw insertion (I.S.I.) mandibular angle, intra-oral trauma-plate was evaluated for torsion and compression stability and compared to conventional plating of simulated angle fractures in polyurethane mandibular replicas. This in vitro comparative pilot study is an extension of the above-mentioned study. Similar I.S.I. mini-plates with 45º inclined screw holes in quadrant 3 (Fig 1), were used but in the one sample 13mm-long lag screws were used to transect the fracture lines where in the other group non-lagging screws of similar length were used to fixate simulated mandibular angle fractures in polyurethane mandible replicas. A uniquely designed and manufactured jig, incorporated in a Zwick machine, was utilized to apply torsion forces within clinical relevant load values. The load-displacement values for torsion forces was determined and compared for the two groups. It was established that 5 lag screws significantly improved the torsion stability of the lag-plate group to that of the non-lag group. During the stability testing, two factors were identified, which had a critical influence on the compression generated by the lag screw between the fracture fragments. An adequate amount of bone must be maintained between the first screw hole, directly distal to the fracture line, and the fracture line. All screws must be inserted in the correct sequence in order to insure sufficient compression between the fracture fragments as a result of the lag-effect. AFRIKAANS : In `n onlangse in vitro studie deur F.J. Jacobs, is `n gepatenteerde, unieke geanguleerde miniplate, waarvan die skroefgate geanguleer is, die sg. Inklineerde Skroef Inplasing (I.S.I.) kaak-hoek, intra-orale traumaplaat geevalueer vir torsie en kompressie stabiliteit en vergelyk met konvensionele plate op gesimuleerde kaakhoek frakture in poli-uretaan mandibular replikas. In hierdie in vitro loodstudie, is I.S.I. miniplate met skroefgate wat teen 45º geanguleer is, gebruik in kombinasie met `n enkele 13mm lange grypskroef (“lag screw”) om gesimuleerde kaakhoek frakture in poli-uretaan mandibula replikas te fikseer. Deur gebruik te maak van `n spesiaal ontwerpte en vervaardigde monterings-apparaat wat binne in `n Zwick masjien geïnkorporeer word, is die I.S.I gefikseerde replikas onderwerp aan torsie kragte, binne klinies relevante ladingswaardes. Die verplasings en ladingswaardes is geregistreer en vergelyk met identiese I.S.I miniplate sonder `n grypskroef. Die loodstudie resultate het getoon dat die frakture wat gefikseerd is met die I.S.I. miniplaat-grypskroef kombinasie betekenisvol beter stabiliteit toon as die frakture wat met slegs die miniplaat, sonder `n grypskroef, gefikseerd is vir klinies relevante ladingsen verplasingswaardes. Tydens biomeganiese toetsing van die mandibula replikas, is twee faktore wat `n kardinale rol speel in die stabiliteit wat verkry word deur `n miniplaat grypskroef kombinasie te gebruik, geïdentifiseer. Voldoende hoeveelheid been tussen die eerste skroefgat, direk distaal van die fraktuurlyn, en die fraktuurlyn asook die korrekte volgorde waarin die skroewe geplaas word, moet gehandhaaf word om maksimale kompressie van die fragmente deur die grypskroef te verseker. Deur `n I.S.I miniplaat, met geanguleerde skroefgate van 45º, te kombineer met `n grypskroef, kan die stabiliteit van die gefikseerde mandibulere kaakhoek betekenisvol verbeter word en verleen dit meer stabiliteit wanneer vergelyk word met frakture gereduseer met `n I.S.I miniplaat sonder grypskroef plasing.Dissertation (MSc)--University of Pretoria, 2010.
Maxillo-Facial and Oral Surgery
unrestricted
Conference papers on the topic "Lag screw effect"
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Kiapour, A., and V. K. Goel. "Effect of Pedicle Lengthening Screw on Biomechanics of Lumbar Spine." In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19358.
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Lumbar spinal canal stenosis is a common cause of back and leg pain which occurs as the lumbar spinal canal narrows. The current surgical treatment for many patients with spinal stenosis is surgical decompression and spinal fusion with instrumentation. However there are several drawbacks associated with fusion surgeries including degenerative effect at segments adjacent to the fusion in long run [1,2]. Pedicle lengthening device is a new technology which is designed to be applied for treatment of spinal stenosis and replace the traditional fusion techniques.
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Joe, Hang-Eun, Huitaek Yun, Martin B. G. Jun, Yonghyun Cho, Farid Ahmed, and Patrick C. Lee. "Characterization of Long Period Grating With a Screw Shape Fabricated by a Single-Path Scanning of Femtosecond Laser." In ASME 2018 13th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/msec2018-6556.
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We propose a manufacturing process for fabrication of long period grating (LPG) with a screw shape by a single-path scanning of femtosecond laser. The optical fiber was rotating in radial direction and traveled along the fiber-axis simultaneously while femtosecond laser irradiation. Several screw-shaped LPGs were fabricated under different parameters, such as laser power, index change length and grating period, and their transmission characteristics were investigated. Moreover, the screw-shaped LPG with complicated pitches of the screw were fabricated by adjusting the rotating speed and travelling speed. The screw-shaped LPG sensor with complex pitches had reverse bending effect that the transmission dip becomes deeper as bending curvature increases. Consequently, it was found that the screw-shaped LPG with multiple pitches of grating has a potential as the sensors for monitoring of the structural characteristics such as bending or curvature under harsh environment.
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Kuo, Chin-Hsing, and Jian S. Dai. "Structure Synthesis of Parallel Manipulators With Fully Decoupled Projective Motion and Any Degrees of Freedom." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22490.
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Abstract This paper presents the structure synthesis of a special class of parallel manipulators with motion decoupleability. The manipulator is synthesized by grouping a motion constraint leg and a set of constraint-free legs. The desired motion, i.e., the output degrees of freedom (DOFs), of the end-effector is expressed by a projective angle representation. It was found that the fully decoupled design for parallel manipulators with any DOFs is achievable when the output motion is described by the projective angles. A synthesis procedure is proposed based on the reasoning of the screw systems and reciprocal screws of the decoupled motion. Several design examples of fully decoupled 2-, 3-, 4-, 5-, and 6-DOF parallel manipulators are provided.
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Castellucci, Valeria, Markus Eriksson, Rafael Waters, Senad Ferhatovic, and Mats Leijon. "Wireless System for Tidal Effect Compensation in the Lysekil Research Site." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83361.
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This paper describes, firstly, the rope adjustment device for wave energy converters (WECs) to minimize the tidal effect on the electricity production and, secondly, a wireless communication network between point absorbing WECs in the Lysekil Research Site and a computer station at the Department of Engineering Sciences at Uppsala University. The device is driven by a motor that activates when the main water level deviates from the average. The adjustment is achieved through a screw that moves upwards during low tides and downwards during high tides. For the purpose of testing the device in the research site, a wireless connection between the buoy in the sea and a computer on land will be designed. A sensor located close to the research site monitors the sea water level and, every time a significant variation is registered, it sends wirelessly a signal to the data logger that controls the power to the motor. The position of the screw is observed by a second sensor and the measurements are retrieved back to Uppsala via GSM connection. The full scale device is tested in the lab and it is demonstrated to work properly, requiring less than 750 W to lift and lower different loads. Moreover, the wireless communication network is designed and once it will be built, it will allow to recall and store data, send information from one node of the system to another, monitor the proper functioning of the device and modify the control as desired.
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De Agostinis, Massimiliano, Dario Croccolo, Stefano Fini, Giorgio Olmi, Francesco Robusto, and Leonardo Bagnoli. "Finite Element Analysis of Tapped Thread Joints: Setup of a Computationally Efficient Modeling Approach." In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-94066.
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Abstract This contribution deals with the efficient numerical modeling of tapped thread joints. Commercial FE packages provide different strategies to tackle the problem of modeling threaded joints, which is a recurrent one for the design engineer. Different modeling techniques are characterised by how the screw is modeled: either three-dimensional elements (thetra, hexa or wedge) or mono-dimensional elements (beam) can be used. In the case of three-dimensional approaches, the thread helix is seldom modeled: the actual geometry is often replaced by a plain cylinder and a suitable choice of contact settings between the screw and the “threaded” hole. In the case of road vehicles, due to the high number of threaded connections to be modeled, it is paramount to reach a trade-off between modeling accuracy and computational effort. This paper aims at comparing two modeling approaches, namely a three dimensional approach (baseline) and a mono-dimensional one (simplified model). Based on several criteria, such as equivalent stress on the screw shank, pressure distribution at the interface of the plates and in the underhead region, optimal contact settings for the simplified model are suggested. These settings allow replicating the results provided by the three-dimensional approach for given load case. The comparison is carried out on single lap, single screw joints, by the ANSYS R17 software. The methodology can be easily extended to other softwares or joint configurations.
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Zlatanov, Dimiter, Matteo Zoppi, and Rezia Molfino. "Constraint and Singularity Analysis of the Exechon Tripod." In ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-71184.
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The paper discusses mobility and singularities of the Exechon three-degree-of-freedom (dof) parallel mechanism (PM) on which a family of parallel kinematic machines is based. Exechon designs are used by a number of machine-tool makers. A new version of the manipulator has been developed as a component of a mobile self-reconfigurable fixture system within an inter-European project. The PM has two UPR (4-dof) legs, constrained to move in a common rotating plane, and an SPR (5-dof) leg. The paper focuses on the constraint and singularity analysis of the mechanism. The screw systems of end-effector freedoms and constraints are identified. The singular configurations are classified in detail and their geometric interpretation is discussed. The velocity kinematics and the Jacobian operator are formulated via a screw-system approach. A fully parameterized package of Maple tools has been developed and used to visualize singularities and their consequences.
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Tai, Yun, Su-Xia Hou, and Fu-Yu Zhao. "Multiple Models Predictive Control of Once-Through Steam Generator." In 16th International Conference on Nuclear Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/icone16-48641.
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Because of multiphase flow during the heat transfer, OTSG (Once-Through Steam Generator) is a complex nonlinear MIMO (Multiple Input and Multiple Output) system. This article sets the mathematics model of OTSG with internal screw and double tubes, uses the FOROTSG program to simulate OTSG, and identifies the system models of different power levels. Based on this, Multiple Model Predictive Control (MMPC) strategy is proposed, which designs the Model Predictive Controller of each model identified, and then integrates the multiple models by Membership Function Law, to achieve smoothly switch of the multiple models at last. The simulating result indicates the MMPC has the good control effects, and it is an available strategy to solve the problems of the nonlinear system control.
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Shaposhnikov, Valery M., Alexander B. Nesterov, Anatoly V. Aleksandrov, and Evgeniia G. Vasilik. "Safety of LNG Transportation in Arctic Conditions When Using Systems of Various Types." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23439.
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Possible expansion of the LNG sea transportation region to the Russian Arctic makes topical the issue on feasibility of using various types of cargo containment systems for large ice LNG carriers of higher ice class notations. When analyzing safety of LNG transportation in the Arctic conditions in case of using cargo containment systems of various types, both fatigue issues adjusted for ice effects (this is especially topically for membrane containment systems) and consequences of emergency situations shall be studied. To evaluate fatigue of membrane cargo containment systems, a special finite element analysis was performed; at that ice effects on the hull were considered together with vibration caused by screws and engines for the purpose of determining maximum possible excitations occurring during the ice navigation. Static, dynamic and life tests, that permitted to estimate experimentally the fatigue margin of membrane containment system elements’ attachment to the vessel hull, were conducted as well.. The study results permit to conclude that the fatigue of CCS NO96 membrane cargo containment system is quite sufficient for resisting vibration loads, which occur during 40-year service life of large Arctic LNG carriers in severe ice conditions. Another important aspect of LNG transportation safety in Arctic conditions consists in accidental load problems. The following types of emergency situations were considered: • accident collision of vessels (LNG carrier ramming by another vessel); • landing on rock (bottom collision with rock in sea conditions); • hull side impact against an iceberg fragment during turning. Consequences of vessels’ collision and impacts against an iceberg were evaluated with the use of software LS-DYNA. It was ascertained based on the performed analysis that the feasibility of LNG carriers with membrane containment systems is minimal; the feasibility of LNG carriers with SPB containment systems is slightly higher, and the feasibility of LNG carriers with MOSS containment systems is essentially higher than that of LNG carriers with membrane containment systems. It could be explained physically by the fact that MOSS cargo containers approach the outer shell plating near the centerline plane (for the bottom) and in the compartment middle (for the side and bottom) only; when moving off from the centerline plane and the compartment middle the distance between cargo containers and the outer shell plating essentially grows. Nevertheless, development of large Arctic LNG carriers having sufficient accidental load levels is possible on application of any containment system type.
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Matsuoka, Taichi, Katsuaki Sunakoda, Kazuhiko Hiramoto, Issei Yamazaki, Akira Fukukita, Paul N. Roschke, Chin-Hsiung Loh, and Pei-Yang Lin. "Seismic Performance of Vibration Control Device That Generates Power." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77695.
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In a previous paper the authors proposed a semi-active vibration control device (VCD) that generates power. The device utilizes a ball screw, and has inertial and damping forces. The damping coefficient is adjusted by altering resistance at the terminal of the power generator. A small-scale VCD was manufactured for experimental testing. Frequency responses of a small-scale spring mass structure were measured in order to confirm the effects of vibration suppression within a wide range of frequencies. In this paper, as the next step, vibration tests using a benchmark structure with an installed VCD that has a 30 kN capacity are carried out at the National Center for Research on Earthquake Engineering (NCREE) in Taiwan. The benchmark structure has three stories with a 3 m height and a mass of 6 tons at each floor level for a total height and weight of 9 m and 18 tons, respectively. The VCDs are installed between adjacent floors with steel chevron braces. A simple control law that is based on a minimized Lyapunov function and employs bang-bang operation is used as a variable current controller instead of the modifying the resistance level of the VCD. Scaled earthquake motions including the Imperial Valley El Centro north-south component that is normalized to be a peak level of 0.5 m/s2, are applied to the base of the steel framed structure in the horizontal direction by a shaking table. Experimental responses of each floor for the uncontrolled and controlled cases are compared with analytical responses, and effects of vibration suppression for the large-scale model are discussed quantitatively.
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Oberhagemann, Jan, Michael Holtmann, Ould el Moctar, Thomas E. Schellin, and Daewoong Kim. "Stern Slamming of an LNG Carrier." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57385.
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Rational assessment of stern slamming of a large twin screw LNG carrier comprised prediction of hydrodynamic impact loads and their effects on the dynamic global structural behavior of the hull girder. Linear theory obtained regular equivalent waves that caused maximum relative normal velocities at critical locations underneath the ship’s stern. Reynolds-averaged Navier-Stokes (RANS) computations based on the volume of fluid (VOF) method yielded transient (nonlinear) hydrodynamic impact (slamming) loads that were coupled to a nonlinear motion analysis of the ship in waves. At every time step of the transient computation, the finite volume grid was translated and rotated, simulating the actual position of the ship. Hydrodynamic loads acting on the hull were converted to nodal forces for a finite element model of the ship structure. Slamming-induced pressure peaks, typically lasting for about 0.5 s, were characterized by a steep increase and decrease before and after the peak values. Shape and duration agreed favorably with full-scale measurements and model tests carried out on other ships, indicating that computed results captured all essential physical phenomena. Hull girder whipping was analyzed to investigate dynamic amplification of structural stresses. Short-duration impact-related slamming loads excited the ship structure to vibrations in a wide range of frequencies. Excitation of the lowest fundamental eigenmode contributed most to additional stresses caused by hull girder whipping. Although longitudinal and shear stresses caused by quasi-steady wave bending were uncritical, we obtained a significant amplification (up to 25 percent) due to the dynamic structural response.