title: Effect of torsional loading on compressive fatigue behaviour of trabecular bone.
abstract: The present study reports the effects of combined torsional and compressive cyclic loading on trabecular bone in order to mimic true physiological conditions and thereby provides improved data that represents clinical and real life conditions. However, only compressive behaviour is evaluated in most previous studies of bone mechanics. From the monotonic evaluation, it is observed that lower stress is needed for the onset of microcrack in the sample under torsional loading, compared to the stress needed in compression. Trabecular bone samples were subjected to a combination of torsion and compression fatigue at different stress levels during which they were compared to compressive axial fatigue. The stress levels were determined by considering the monotonic strength at 25-50% for both compressive and shear stresses. Significant decrease in fatigue lifetime is observed in between samples of pure compression fatigue and those with superpositioned torsional loading (p<0.05). The reduction in fatigue lifetime became more evident at a high torsional stress level. In this case, the failure of the sample is said to be 'torsional dominant'. Fatigue behaviour of bovine trabecular bone begins with plastic deformation, followed by strain accumulation and modulus reduction. As the strain rate increases, more energy dissipates and the sample finally failed. Further, the analysis of fractograph revealed something on the trabeculae by bending in sample with superpositioned torsional loading. In conclusion, torsional loading decreases the quality of the trabecular properties in terms of stiffness, life and structural integrity. It is hoped that results from this study will improve the understanding of the behaviour of trabecular bone under combined fatigue and help to develop future assessments of trabecular failure.
authors.affiliation: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia.
authors.forename: S J
authors.initials: SJ
authors.lastname: Fatihhi
authors.affiliation: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia.
authors.forename: A A R
authors.initials: AA
authors.lastname: Rabiatul
authors.affiliation: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia; Sport Innovation and Technology Centre (SITC), Institute Human Centred Engineering (IHCE), Universiti Teknologi Malaysia, Johor, Malaysia.
authors.forename: M N
authors.initials: MN
authors.lastname: Harun
authors.affiliation: Medical Devices and Technology Group (Mediteg), Faculty of Biomedical Engineering and Health Science, Universiti Teknologi Malaysia, Johor, Malaysia.
authors.forename: Mohammed Rafiq Abdul
authors.initials: MR
authors.lastname: Kadir
authors.affiliation: Tissue Engineering Group, NOCERAL, Department of Orthopaedic Surgery, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: T
authors.initials: T
authors.lastname: Kamarul
authors.affiliation: Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia; Sport Innovation and Technology Centre (SITC), Institute Human Centred Engineering (IHCE), Universiti Teknologi Malaysia, Johor, Malaysia. Electronic address: ardiyans@gmail.com.
authors.forename: Ardiyansyah
authors.initials: A
authors.lastname: Syahrom
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002417:Cattle; D019245:Compressive Strength; D005269:Femur / Q000502:physiology*; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D016474:Weight-Bearing
keywords: Combined loading; Effect of torsion; Fatigue; Multiaxial; Trabecular bone