13th International Conference on Fracture June 16–21, 2013, Beijing, China -1- Study of the Mechanical Properties of Bones Under Fracture Healing Conditions with Specific Medical Treatments, Using 4 Point Bending Tests and Ultra-Micro Indentation Techniques Soraya Diego1, Estela Ruiz1, José A. Casado1, Diego Ferreño1, Manuel Redondo1, María I. Pérez2, José A. Riancho2, Isidro Carrascal1, Claudia Demian1, Federico Gutiérrez-Solana1 and Christopher Vilupillai1 1 Department of Materials Science University of Cantabria. 39005 Santander (Cantabria). Spain 2 Universitary Hospital Marqués de Valdecilla. Avda. Valdecilla s/n, 39008 Santander (Cantabria), Spain * Corresponding author: jose.casado@unican.es Abstract This paper aims to compare the effectiveness of two medical treatments in healing an induced pseudoarthrosis (bone fracture without direct contact thus driving a callus formation) on the right femurs of Sprague Dawley laboratory rats. To further understand and quantify the mechanical effects of each treatment, the bone mechanical properties were analysed in terms of the following parameters: hardness and elastic modulus using ultra-micro indentation tests, and maximum force, energy absorbed up to maximum force and rigidity using four point bending tests. To assess the effectiveness of the treatments in terms of mechanical performance, the results were compared against a control group and a regular bone fracture (direct contact between broken bone parts without a gap). Both treatments were successful in restoring properties similar to the control group in terms of overall hardness (in both cortical and trabecular bone tissues) and rigidity. However, one of them appears to provide higher values of maximum force, energy absorbed and bone hardness. The results provide information that can be extrapolated to further understand the treatment of human bone fractures in terms of mechanical properties. The data enables the comparison of the outcomes that both treatments have on the biomechanical functioning of bone fractures. Keywords pseudoarthrosis, four point bending test, ultra-micro indentation test, osseous callus 1. Introduction Since the 1990s, several studies have been trying to transfer engineering methods to analyze biological materials [1-5]. This gave rise to one of the fundamental principles of biomechanics: the reaction of a tissue of an organism to stimuli, obeys the same laws that govern the behavior of typical “engineering” materials. Thus making applicable the methods used to measure engineering material properties to biological tissues, such as bones for example. In order to understand human bone tissues it is usual to study animal bones, as they provide an ideal biomechanical model due to their size and rudimentary functioning, simplifying the analysis of mechanical properties. This paper compares the effectiveness of two medical treatments, “A” and “B”, on a subtraction osteotomy of Sprague Dawley rat femurs against a control group and a normal fracture. The aim of the paper is to study the effect of “A” and “B” on the healing of a subtraction osteotomy, by applying methods used for calculating engineering material properties. This investigation is complemented with other studies about biological parameters which haven´t been finished yet; for this reason it is necessary to maintain the confidentiality of the name of the treatments considered until the whole study is completed. Results were acquired through 4 point bending tests on the bone sample shafts (diaphysis) and ultra-micro indentation tests on the bone sample extremities (lower and upper extremities). The 4PBTs provided maximum force, energy absorbed up to maximum force and rigidity. The UMI tests enabled the determination of the cortical and trabecular bone hardness and elastic modulus. The data were obtained by using the left and right femurs of twelve
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