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Load distribution between cephalic screws in a dual lag screw trochanteric nail

BACKGROUND: It has been observed clinically that the Z-effect is a potential cause of failure of an intramedullary nail with two cephalic screws. It describes the migration behavior of the cephalic screws in the femoral head. The primary objective was to examine different cephalic screw configuratio...

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Autores principales: Henschel, Julia, Eberle, Sebastian, Augat, Peter
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818857/
https://www.ncbi.nlm.nih.gov/pubmed/27039374
http://dx.doi.org/10.1186/s13018-016-0377-y
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author Henschel, Julia
Eberle, Sebastian
Augat, Peter
author_facet Henschel, Julia
Eberle, Sebastian
Augat, Peter
author_sort Henschel, Julia
collection PubMed
description BACKGROUND: It has been observed clinically that the Z-effect is a potential cause of failure of an intramedullary nail with two cephalic screws. It describes the migration behavior of the cephalic screws in the femoral head. The primary objective was to examine different cephalic screw configurations and test the load distribution between them as a function of their relative placement and their relative movement in the nail. It has been hypothesized that different cephalic screw positions may have an influence on the stress in the implant and bone and therefore on implant failures, such as the Z-effect. METHODS: To quantify the load distribution of a dual cephalic screw intramedullary femoral nail (Citieffe, Calderara di Reno, BO, Italy), a finite element model of the femur, focusing on the loading of the cephalic screws, was prepared. Four different screw lengths (90–105 mm) were examined. The investigation considered the stresses and strains in the bone and implant as well as the relative movement of the screws. RESULTS: If the inferior cephalic screw had a shorter length, then the superior one and the femoral nail had to bear higher loads. In that case, the “equivalent von Mises stress” increased up to 10 % at the superior cephalic screw and up to 5 % at the femoral nail. The analysis of the relative movement showed that sliding of the inferior cephalic screw occurred in the nail. The total movement ranged from 0.47 to 0.73 mm for the different screw configurations. CONCLUSIONS: The stresses were distributed more equally between the two cephalic screws in the bone and the implant if a longer inferior screw was used. The stresses in the bone and implant were reduced with a longer inferior cephalic screw. Therefore, a configuration using a longer inferior cephalic screw is preferable for trochanteric fracture fixation with a dual cephalic screw intramedullary device.
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spelling pubmed-48188572016-04-04 Load distribution between cephalic screws in a dual lag screw trochanteric nail Henschel, Julia Eberle, Sebastian Augat, Peter J Orthop Surg Res Research Article BACKGROUND: It has been observed clinically that the Z-effect is a potential cause of failure of an intramedullary nail with two cephalic screws. It describes the migration behavior of the cephalic screws in the femoral head. The primary objective was to examine different cephalic screw configurations and test the load distribution between them as a function of their relative placement and their relative movement in the nail. It has been hypothesized that different cephalic screw positions may have an influence on the stress in the implant and bone and therefore on implant failures, such as the Z-effect. METHODS: To quantify the load distribution of a dual cephalic screw intramedullary femoral nail (Citieffe, Calderara di Reno, BO, Italy), a finite element model of the femur, focusing on the loading of the cephalic screws, was prepared. Four different screw lengths (90–105 mm) were examined. The investigation considered the stresses and strains in the bone and implant as well as the relative movement of the screws. RESULTS: If the inferior cephalic screw had a shorter length, then the superior one and the femoral nail had to bear higher loads. In that case, the “equivalent von Mises stress” increased up to 10 % at the superior cephalic screw and up to 5 % at the femoral nail. The analysis of the relative movement showed that sliding of the inferior cephalic screw occurred in the nail. The total movement ranged from 0.47 to 0.73 mm for the different screw configurations. CONCLUSIONS: The stresses were distributed more equally between the two cephalic screws in the bone and the implant if a longer inferior screw was used. The stresses in the bone and implant were reduced with a longer inferior cephalic screw. Therefore, a configuration using a longer inferior cephalic screw is preferable for trochanteric fracture fixation with a dual cephalic screw intramedullary device. BioMed Central 2016-04-01 /pmc/articles/PMC4818857/ /pubmed/27039374 http://dx.doi.org/10.1186/s13018-016-0377-y Text en © Henschel et al. 2016 Open AccessThis 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.
spellingShingle Research Article
Henschel, Julia
Eberle, Sebastian
Augat, Peter
Load distribution between cephalic screws in a dual lag screw trochanteric nail
title Load distribution between cephalic screws in a dual lag screw trochanteric nail
title_full Load distribution between cephalic screws in a dual lag screw trochanteric nail
title_fullStr Load distribution between cephalic screws in a dual lag screw trochanteric nail
title_full_unstemmed Load distribution between cephalic screws in a dual lag screw trochanteric nail
title_short Load distribution between cephalic screws in a dual lag screw trochanteric nail
title_sort load distribution between cephalic screws in a dual lag screw trochanteric nail
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4818857/
https://www.ncbi.nlm.nih.gov/pubmed/27039374
http://dx.doi.org/10.1186/s13018-016-0377-y
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