95 research outputs found
Assessment of tibial fracture healing using dual energy X-ray absorptiometry
No full textThe assessment of fracture healing is largely a matter of clinical judgement, often based on observing x-rays showing the formation of bridging callus or obscuration of the fracture line and an impression of fracture stiffness obtained by manual loading. In circumstances where these assessment methods are compromised, for example in fractures stabilised using either external fixation or intramedullary nailing, the determination of healing can be problematic. Dual Energy X-ray Absorptiometry (DXA) provides a quick, non-invasive and quantitative method of measuring bone density, which could enable the change in mineral content at a healing site to be monitored. This study evaluated the viability of using DXA to assess the healing of tibial fractures stabilised using intramedullary nails and external fixators. Trials have been undertaken on a Lunar DPX-L scanner situated at South Cleveland Hospital, Middlesbrough. Aluminium and hydroxyapatite phantoms have been used to determine the accuracy, sensitivity and reproducibility of the DXA measurements. Small fracture gaps of less than 0.05 mm were detectable on both simulated transverse and oblique fractures. BMD values which one might expect at a fracture site could be accurately measured down to 0.16 g cm(^-2)14 Patients with tibial fractures (6 with intramedullary nails and 8 with external fixators) have been measured at 4 week intervals following trauma. The bone mineral density (BMD) at regions of interest along the fractured tibial shaft were compared to the non-fractured contra-lateral. Anatomical landmarks were used to relocate the regions of interest between scans and good reproducibility of results (coefficient of variation = 3.36 %) was obtained. After an initial fall in the first month, the BMD at the fracture site gradually increased to the original unfractured value by approximately the fifth month post-fracture. Proximal and distal to the trauma site there was a gradual decrease in BMD in all of the patients, which persisted for about 5 months post-fracture
Laminated veneer lumber hollow cross-sections for temporary soil nailing
No full textAn innovative approach using laminated veneer lumber (LVL) hollow sections for temporary geotechnical slope stabilisation is being presented within this article. The use of circular laminated veneer lumber hollow sections as reinforcement elements in soil nailing walls demands load bearing elements, primarily loaded in tension, with a length up to 10 m. Thus finger-jointing was found to be an efficient method of a longitudinal load-carrying connection in combination with a minimized cross section reduction at the joint. This paper discusses the applicabiltiy of finger jointing on beech wood laminated veneer lumber hollow sections and presents the results of large scaled tensile under variaton of the joint arrangement
Noise source identification and dynamic modeling of a pneumatic nailing device
No full textExposure to hazardous noise levels emitted by pneumatic nailing devices contributes significantly to risk of hearing damage among the construction workers throughout the world. This health problem comes from the lack of appropriate technology such as low noise devices which in turn results from the lack of scientific knowledge about designing reduced noise devices. This study contributes to the design improvement of pneumatic nailing devices through identifying the noise sources and developing the simulation tool required to redesign the pneumatic nailing device.
To identify the noise sources, the study uses a combination of two complementary experimental approaches. The first makes use of time-synchronized data analysis of several variables during the machine operation. This strategy allows identifying the physical processes and provides a detailed separation of the noise generation mechanisms in successive time sequences. However, since multiple noise sources radiate at the same time, this observation approach is not sufficient for noise source identification and ranking. Thus, it is completed by a selective wrapping and muffler procedure. This technique provides overall generated noise associated with each process, as well as ranking of the three major sources: (1) exhaust noise, (2) machine body vibrations, and (3) workpiece vibrations. A special investigation is conducted on this third one with two cases: a workpiece/worktable setup representative of the actual field usage of a nailing device and a workpiece/sandbox setup used in a standardized laboratory test. The study evaluates the efficiency of the workpiece/sandbox setup in reducing the workpiece radiation and obtains a typical workpiece contribution on an actual worksite.
To provide a simulation tool, a dynamic model of the pneumatic nailing device needs to be developed. Dynamic modeling of the nailing device requires mathematical modeling of the physical processes involved in its operation. All of these processes can be described through already existing mathematical relations, except for the penetration resistance force (PRF) imposed on the nails when penetrating the wood.
The PRF depends on various factors. This study follows two approaches in parallel to develop an empirical prediction law for the PRF: quasi-static and high-speed.
The quasi-static approach provides a rapid and precise representation of the law at quasistatic penetration velocities. The law covers the entire displacement range, various nail geometries and sizes, and wood types.
The high-speed approach aims to provide a law which covers a much wider range of penetration velocities. The approach is complicated since it requires a sophisticated test machine to conduct the nail driving tests at high penetration velocities. The study designs and fabricates an advanced test machine to later extend the prediction range of the PRF law.
The last part of this study develops the dynamic model of a nail gun while integrating the quasi-static PRF law. The model includes dynamics of all the air chambers and the moving parts, and interactions and impacts/contacts between different parts. The study integrates a comprehensive experimental validation of the model. Future improvements in the dynamic model precision will be possible by using the extended version of the PRF law
Retrograde tibial nailing of far distal tibia fractures: a biomechanical evaluation of double- versus triple-distal interlocking
No full textGreenfield J, Appelmann P, Wunderlich F, Mehler D, Rommens PM, Kuhn S. Retrograde tibial nailing of far distal tibia fractures: a biomechanical evaluation of double- versus triple-distal interlocking. European Journal of Trauma and Emergency Surgery. 2021.OBJECTIVES: Retrograde tibial nailing using the Distal Tibia Nail (DTN) is a novel surgical option in the treatment of distal tibial fracture. Its unique retrograde insertion increases the range of surgical options in far distal fractures of the tibia beyond the use of plating. The aim of this study was to assess the feasibility of the DTN for far distal tibia fractures where only double rather than triple-distal locking is possible due to fracture localisation and morphology.; METHODS: Six Sawbones were instrumented with a DTN and an AO/OTA 43-A3 fracture simulated. Samples were tested in two configurations: first with distal triple locking, second with double locking by removing one distal screw. Samples were subjected to compressive (350N, 600N) and torsional (±8 Nm) loads. Stiffness construct and interfragmentary movement were quantified and compared between double and triple-locking configurations.; RESULTS: The removal of one distal screw resulted in a 60-70% preservation of compressive stiffness, and 90% preservation of torsional stiffness for double locking compared to triple locking. Interfragmentary movement remained minimal for both compressive and torsional loading.; CONCLUSIONS: The DTN with a distal double locking can, therefore, be considered for far distal tibia fractures where nailing would be preferred over plating. © 2021. The Author(s)
Int J Ind Ergon
No full textA biomechanical model is presented, and combined with measurements of tip press force, to estimate total user hand force associated with two pneumatic nail gun trigger systems. The contact actuation trigger (CAT) can fire a nail when the user holds the trigger depressed first and then "bumps" the nail gun tip against the workpiece. With a full sequential actuation trigger (SAT) the user must press the tip against the workpiece | to activating the trigger. The SAT is demonstrably safer in reducing traumatic injury risk, but increases the duration (and magnitude) of tip force exertion. Time integrated (cumulative) hand force was calculated for a single user from measurements of the tip contact force with the workpiece and transfer time between nails as inputs to a static model of the nail gun and workpiece in two nailing task orientations. The model shows the hand force dependence upon the orientation of the workpiece in addition to the trigger system. Based on standard time allowances from work measurement systems (i.e. Methods-Time Measurement - 1) it is proposed that efficient application of hand force with the SAT in maintaining tip contact can reduce force exertion attributable to the sequential actuation trigger to 2-8% (horizontal nailing) and 9-20% (vertical nailing) of the total hand/arm force. The present model is useful for considering differences in cumulative hand/arm force exposure between the SAT and CAT systems and may explain the appeal of the CAT trigger in reducing the user's perception of muscular effort.CC999999/Intramural CDC HHSUnited States
Does Policy Matter? On Governments’ Attempts to Control Unwanted Migration
No full textPublic policy making on asylum takes place in an environment of intense public scrutiny, strong institutional constraints and international collective action problems. By assessing the relative importance of key pull factors of international migration, this article explains why, even when controlling for their differences in size, some states receive a much larger number of asylum seekers than others. The analysis of 20 OECD countries for the period 1985-1999 further shows that some of the most high profile public policy measures—safe third country provisions, dispersal and voucher schemes—aimed, at least in part, at deterring unwanted migration and at addressing the highly unequal distribution of asylum burdens have often been ineffective. This is because the key determinants of an asylum seeker’s choice of host country are historical, economic and reputational factors that largely lie beyond the reach of asylum policy makers. Finally, the paper argues that the effectiveness of unilateral policy measures will be further undermined by multilateral attempts to harmonise restrictive policies and that current efforts such as those by the European Union will consolidate, rather than effectively address, existing disparities in the distribution of asylum burdens.public policy effectiveness, asylum, migration pull factors, deterrence, burden sharing, collective action problems, international co-operation, European Union
Reform of the EU Sugar Regime: Impacts on Sugar Production in Ireland
No full textThe EU Common Market Organisation has remained largely unchanged since its inception nearly 40 years ago. Reform has become inevitable due to changes to other sectors in the Common Agriculture Policy and pressure arising from international commitments. The current system provides sufficient support for all Member States to produce sugar, regardless of their efficiency. The proposed reform will therefore affect the least efficient producing regions most strongly. This paper examines the case of Ireland in light of the competitive position of its sugar sector in the EU context. Calculation of the likely impact on sugar beet gross margins and farm income suggest that many producers will want to exit sugar beet production. In light of this, the implications and possible strategies for growers and Irish Sugar are discussed.EU sugar policy, Irish agriculture, farm income
Economics of the US - Canada Softwood Lumber Dispute: A Historical Perspective
No full textThis paper reviews the U.S.-Canada softwood lumber dispute over the past two decades by outlining the key developments and critically appraising the arguments put forward by both countries. It also presents a welfare analysis of lumber trade distortions. Given the importance of lumber trade between Canada and the United States, an expeditious resolution of this long-running trade dispute would be beneficial for both countries.antidumping and countervailing duties, lumber, trade distortions, welfare, Resource /Energy Economics and Policy,
A positioning technique for closed intramedullar nailing of tibia fractures
No full textBackground. We described a method of positioning the patient on the standard operation table that enables manual traction and equipment that is available in almost all operating theaters and compared it with regular positioning technique. Methods: Eighty two patients with unstable unilateral tibia fractures were evaluated and treated in the author's clinic between July 2002 and June 2006. The average age of the patients was 40.6 (29-65) years. The surgical indications included uncomplicated closed fractures, fractures in patients with multiple injuries, and inability to maintain a satisfactory closed reduction. Forty-two fractures that were operated with the new technique and meet these criteria's were included in the study. All operations were performed on normal operation tables. Results: There was not any case of failure related with the nailing and the presented positioning technique. Intraoperative reduction was achieved with closed method in all patients. In 10 patients, satisfactory reduction was achieved with the help of polar screws in 2 patients and cable system in 8 patients. Anatomic reduction was obtained in the rest of 32 patients. There were no cases of compartment syndrome diagnosed postoperatively in both injured and uninjured side. There were also no neurologic complications and postoperative infection formation related to surgery. Conclusion: The advantages of this technique is that, it allows precise reduction, control of rotation, and easy imaging access, without increasing operating or screening time and complication
- …
