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      Improving stability of elastic stable intramedullary nailing in a transverse midshaft femur fracture model: biomechanical analysis of using end caps or a third nail


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          Elastic stable intramedullary nailing (ESIN) is accepted widely for treatment of diaphyseal femur fractures in children. However, complication rates of 10 to 50 % are described due to shortening or axial deviation, especially in older or heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with end caps or a third nail could significantly improve the stability in comparison to classical elastic stable intramedullary nailing in a transverse femur fracture model.


          We performed biomechanical testing in 24 synthetic adolescent femoral bone models (Sawbones®) with a transverse midshaft (diaphyseal) fracture. First, in all models, two nails were inserted in a C-shaped manner (2 × 3.5 mm steel nails, prebent), then eight osteosyntheses were modified by using end caps and another eight by adding a third nail from the antero-lateral (2.5-mm steel, not prebent). Testing was performed in four-point bending, torsion, and shifting under physiological 9° compression.


          The third nail from the lateral showed a significant positive influence on the stiffness in all four-point bendings as well as in internal rotation comparing to the classical 2C configuration: mean values were significantly higher anterior-posterior (1.04 vs. 0.52 Nm/mm, p < 0.001), posterior-anterior (0.85 vs. 0.43 Nm/mm, p < 0.001), lateral-medial (1.26 vs. 0.70 Nm/mm, p < 0.001), and medial-lateral (1.16 vs. 0.76 Nm/mm, p < 0.001) and during internal rotation (0.16 vs. 0.11 Nm/°, p < 0.001). The modification with end caps did not improve the stiffness in any direction.


          The configuration with a third nail provided a significantly higher stiffness than the classical 2C configuration as well as the modification with end caps in this biomechanical model. This supports the ongoing transfer of the additional third nail into clinical practice to reduce the axial deviation occurring in clinical practice.

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          Epidemiology of fractures in children and adolescents

          Background and purpose Fractures are most common in youth and in the elderly, with differences in incidence over time and between regions. We present the fracture pattern in a population of youths ≤ 19 years of age, who were seen at Umeå University Hospital, Sweden. Material and methods All injuries seen at the hospital have been recorded in a database since 1993. The data include variables such as age, sex, date, type of injury, mechanism of injury, and treatment. For the period 1993–2007, there were 10,203 injury events that had resulted in at least 1 fracture. Results The incidence for the whole period was 201/104 person years. The incidence increased by 13% during the period 1998–2007, when we were able to control for registration errors. The most common fracture site was the distal forearm. The most common type of injury mechanism was falling. The peak incidence occurred at 11–12 years in girls and at 13–14 years in boys, with a male-to-female incidence ratio of 1.5. We found variations in mechanisms and activities at injury with age, and over time. Interpretation Fractures are caused by a combination of intrinsic and extrinsic factors that vary with age. We believe the increase in incidence is partly explained by changes in children's activity patterns over time. Further research may help to identify preventive measures to reduce the number of fractures, in particular those involving hospital care, surgical treatment, and—most importantly—long-term impairment.
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            Mechanical validation of whole bone composite femur models.

            Composite synthetic models of the human femur have recently become commercially available as substitutes for cadaveric specimens. Their quick diffusion was justified by the advantages they offer as a substitute for real femurs. The present investigation concentrated on an extensive experimental validation of the mechanical behaviour of the whole bone composite model, compared to human fresh-frozen and dried-rehydrated specimens for different loading conditions. First, the viscoelastic behaviour of the models was investigated under simulated single leg stance loading, showing that the little time dependent phenomena observed tend to extinguish within a few minutes of the load application. The behaviour under axial loading was then studied by comparing the vertical displacement of the head as well as the axial strains, by application of a parametric descriptive model of the strain distribution. Finally, a four point bending test and a torsional test were performed to characterize the whole bone stiffness of the femur. In all these tests, the composite femurs were shown to fall well within the range for cadaveric specimens, with no significant differences being detected between the synthetic femurs and the two groups of cadaveric femurs. Moreover, the interfemur variability for the composite femurs was 20-200 times lower than that for the cadaveric specimens, thus allowing smaller differences to be characterized as significant using the same simple size, if the composite femurs are employed.
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              Decreasing incidence and changing pattern of childhood fractures: A population-based study.

              Fractures are common in children, and some studies suggest an increasing incidence. Data on population-based long-term trends are scarce. In order to establish fracture incidence and epidemiologic patterns, we carried out a population-based study in Helsinki, Finland. All fractures in children aged 0 to 15 years were recorded from public health care institutions during a 12-month period in 2005. Details regarding patient demographics, fracture site, and trauma mechanism were collected. All fractures were confirmed from radiographs. Similar data from 1967, 1978, and 1983 were used for comparison. In 2005, altogether 1396 fractures were recorded, 63% in boys. The overall fracture incidence was 163 per 10,000. Causative injuries consisted of mainly falls when running or walking or from heights less than 1.5 m. Fracture incidence peaked at 10 years in girls and 14 years in boys. An increase in fracture incidence was seen from 1967 to 1983 (24%, p < .0001), but a significant decrease (18%, p < .0001) was seen from 1983 to 2005. This reduction was largest in children between the ages of 10 and 13 years. Despite the overall decrease and marked decrease in hand (-39%, p < .0001) and foot (-48%, p < .0001) fractures, the incidence of forearm and upper arm fractures increased significantly by 31% (p < .0001) and 39% (p = .021), respectively. Based on these findings, the overall incidence of childhood fractures has decreased significantly during the last two decades. Concurrently, the incidence of forearm and upper arm fractures has increased by one-third. The reasons for these epidemiologic changes remain to be elucidated in future studies. Copyright © 2010 American Society for Bone and Mineral Research.

                Author and article information

                0049 - 451-500-2127 , kaiser@uni-luebeck.de
                J Orthop Surg Res
                J Orthop Surg Res
                Journal of Orthopaedic Surgery and Research
                BioMed Central (London )
                25 June 2015
                25 June 2015
                : 10
                : 96
                [ ]Department of Paediatric Surgery, Hospital of Kassel, Mönchebergstr. 41-43, 34125 Kassel, Germany
                [ ]Department of Paediatric Surgery, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
                [ ]Department of Biomechatronics and Academic Orthopaedics, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
                © Rapp et al. 2015

                Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                : 10 March 2015
                : 14 June 2015
                Research Article
                Custom metadata
                © The Author(s) 2015

                elastic stable intramedullary nailing,biomechanical testing,femur fracture,end caps,third nail


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