ABSTRACT
SUMMARY: Biomechanical factors are important factors in inducing intervertebral disc degeneration, in this paper, the nonlinear viscoelastic mechanical properties of degenerated intervertebral discs were analyzed experimentally. Firstly, the loading and unloading curves of intervertebral discs before and after degeneration at different strain rates were compared to analyze the changes of their apparent viscoelastic mechanical properties; The internal stress/strain distribution of the disc before and after degeneration was then tested by combining digital image technology and fiber grating technology. The results show that the intervertebral disc is strain-rate- dependent whether before or after degeneration; The modulus of elasticity and peak stress of the degenerated disc are significantly reduced, with the modulus of elasticity dropping to 50 % of the normal value and the peak stress decreasing by about 55 %; Degeneration will not change the distribution of the overall internal displacement of the intervertebral disc, but has a greater impact on the superficial and middle AF; The stress in the center of the nucleus pulposus decreases, and the stress in the outer AF increases after degeneration. Degeneration has a great impact on the nonlinear viscoelastic mechanical properties of intervertebral disc, which has reference value for the mechanism, treatment and prevention of clinical degenerative diseases.
RESUMEN: Los factores biomecánicos son importantes en la inducción de la degeneración del disco intervertebral. En este estudio se analizaron experimentalmente las propiedades mecánicas viscoelásticas no lineales de los discos intervertebrales degenerados. En primer lugar se compararon las curvas de carga y descarga de los discos intervertebrales, antes y después de la degeneración, a diferentes velocidades de deformación para analizar los cambios aparentes de sus propiedades mecánicas viscoelásticas. La distribución interna de tensión/deformación del disco antes y después de la degeneración se probó luego combinando tecnología de imagen digital y tecnología de rejilla de fibra. Los resultados mostraron que el disco intervertebral depende de la velocidad de deformación antes o después de la degeneración; El módulo de elasticidad y la tensión máxima del disco degenerado se reducen significativamente, cayendo el módulo de elasticidad al 50 % del valor normal y la tensión máxima disminuyendo en aproximadamente un 55 %; La degeneración no cambiará la distribución del desplazamiento interno general del disco intervertebral, pero tiene un mayor impacto en la FA superficial y media; El estrés en el centro del núcleo pulposo disminuye y el estrés en el FA externo aumenta después de la degeneración. La degeneración tiene un gran impacto en las propiedades mecánicas viscoelásticas no lineales del disco intervertebral, que tiene valor de referencia para el mecanismo, tratamiento y prevención de enfermedades clínicas degenerativas.
Subject(s)
Stress, Mechanical , Viscosity , Nonlinear Dynamics , Intervertebral Disc Degeneration , Biomechanical Phenomena , Elastic Modulus , Models, BiologicalABSTRACT
Coronary artery diseases (CAD) have always been serious threats to human health. The measurement, constitutive modeling, and analysis of mechanical properties of the blood vessel wall can provide a tool for disease diagnosis, stent implantation, and artificial artery design. The vessel wall has both active and passive mechanical properties. The passive mechanical properties are mainly determined by elastic and collagen fibers, and the active mechanical properties are determined by the contraction of vascular smooth muscle cells (VSMC). Substantial studies have shown that, the two-layer model of the vessel wall can feature the mechanical properties well, and the circumferential, axial and radial strain and stress are of great significance in arterial wall mechanics. This study reviewed recent investigations of mechanical properties of the vessel wall. Challenges and opportunities in this area are discussed relevant to the clinical treatment of coronary artery diseases.
Subject(s)
Humans , Biomechanical Phenomena , Coronary Vessels , Models, Cardiovascular , Myocytes, Smooth Muscle , Stress, MechanicalABSTRACT
BackgroundIt has been proved that,after being forced,the biological soft tissue has stable biomechanical characteristics.However,there is rare study on corneal biomechanics.Rabbit is a main animal for experimental study in ophthalmology.But the biomechanical study of cornea in normal rabbit has not been reported.ObjectiveThis study was to investigate the biomechanical properties of normal rabbit central cornea and acquire the parameter. Methods Ten rabbits were sacrificed and the whole corneas were obtained and 20 central cornea specimens with 7 mm×5 mm of rabbit were prepared and tested on BOSE electroforce 3220-AT biomechanics machine under the room temperature and suitable humidity environment.Uniaxial tension,stress between strain,relaxation and creep were performed and the curves were drawn.The data was collected by wintest system to evaluate the biomechanical parameters of rabbit corneal tissue. ResultsThe maximum distortion intension of rabbit cornea was (7.7432±0.6099)MPa.After three cyclic loading,the stress gradually attenuated and the stress and strain flattened as the time change with the relaxation rate 30.33％.The deformation of the specimens enhanced with time decrease with the creep rate 24.33％. ConclusionsThe biomechanical characteristics of normal rabbit cornea are revealed in this study,which offer the basis for the experimental research of rabbit model aimed at corneal disease.