Theory of particle transport phenomena during fatigue and time-dependent fracture of materials based on mesoscale dynamics and their practical applications.

In this work, the mesoscale mechanics of metals, which links their microscopic physics and macroscopic mechanics, was established. For practical applications, the laws for quantitatively predicting life of cycle and time-dependent fracture behavior such as fatigue, hydrogen embrittlement, and high-temperature creep were derived using particle transport phenomena theories such as dislocation group dynamics, hydrogen diffusion, and vacancy diffusion. Furthermore, these concepts were also applied for estimating the degree of viscoelastic deterioration of blood vessel walls, which is dominated by a time-dependent mechanism, and for the diagnosis of aneurysm accompanied by the viscoelastic deterioration of the blood vessel wall.

Pre-clinical assessment of a prototype non-invasive diagnostic device to detect aortic aneurysms.

We have developed a non-invasive diagnostic device for treating thoracic aortic aneurysm that can be applied at a peripheral artery. This study aimed to examine how configuration and size of an aneurysm as well as endoluminal pressure affect our diagnostic device's ability to detect an aneurysm, using a pulsatile mock circulation. We created three different-sized (12, 16, and 20 mm) saccular and fusiform aneurysm models using silicone and incorporated them in a pulsatile perfusion circuit to evaluate vertical vessel wall velocity wave form at a location apart from the aneurysm.

Tight medial knot tying may increase retearing risk after transosseous equivalent repair of rotator cuff tendon.

Background: Retearing mechanism after transosseous equivalent (TOE) rotator cuff repair has not been fully clarified yet.

Objective: The purposes of this study were to compare the stress distribution pattern in the tendon stump between knotted and knotless TOE repair and to investigate the role of suture tension applied during medial knot tying using a 3-dimensional finite element (3D-FE) method.

Methods: Both knotted and knotless TOE repairs were simulated on the 3D-FE human rotator cuff tear model.

Predicting failures of suture anchors used for rotator cuff repair: a CT-based 3-dimensional finite element analysis.

Background: Failure of inserted anchors has been recognized as one of the major pathomechanisms of re-tearing after rotator cuff repair.

Objective: To predict the inserted anchor failure using CT-based 3-dimensional finite element method (CT/3D-FEM).

Methods: Among twenty patients who underwent rotator cuff repair, 5 had anchor failure (failed anchor group) and 15 had no anchor failure (stable anchor group).

Viscoelastic Deterioration of the Carotid Artery Vascular Wall is a Possible Predictor of Coronary Artery Disease.

Aim: The viscoelastic properties of the artery are known to be altered in patients with vascular diseases. However, few studies have evaluated the viscoelasticity of the vascular wall in humans. We sought to investigate the degree of viscoelastic deterioration of the carotid artery and assess its clinical implications.

Correlation between the characteristics of acceleration and visco elasticity of artery wall under pulsatile flow conditions (physical meaning of I* as a parameter of progressive behaviors of atherosclerosis and arteriosclerosis).

Previously, I* parameter has been proposed to diagnose noninvasively the progressive degree of atherosclerosis which is considered to concern the discrimination of the progressive degree of visco elasticity of blood vessel wall. However, the detailed physical meaning of this parameter has not yet been clarified. In this paper, the theoretical analysis and experiments were conducted and the detailed physical meaning of I* parameter was clarified.

Frequency response of blood vessel wall with atherosclerosis and aneurysm.

This research was conducted to investigate frequency response of blood vessel wall. The principal frequency of blood vessel wall, f1 was found to decrease with progression of atherosclerosis and irregularity of the vibration trajectory of blood vessel wall was found to increase. When an aneurysm appeared, a new vibration wave was found to appear in the high frequency region, f2.

The analysis and diagnosis of unstable behavior of the blood vessel wall with an aneurysm based on noise science.

Previously, one of the authors developed a noninvasive measurement method of acceleration and deceleration during the expansion process of the blood vessel wall under pulsatile pressure flow by measuring the strain rate of the blood vessel wall using a supersonic Doppler effect sensor aided by computer analysis (DPC method). In this paper, on the basis of the analysis of chaos theory, that is, the complexity of science, the unstable behavior of the blood vessel wall with an aneurysm was investigated by identifying the characteristic DPC wave forms induced by the onset and progression of aneurysm. These results showed that unstable dynamic behavior of the blood vessel wall occurs due to the progression of the aneurysm.

The proposal of noninvasive quantitative diagnostic method of the atherosclerosis and the clarification of organ correlation of atherosclerosis and oxygen metabolism.

The proposal of noninvasive diagnostic method of mechanical degradation of vascular wall is clinically useful and it will be correlated with noninvasive diagnostic method of atherosclerosis. Supersonic Doppler effect sensor has been used to measure blood flow velocity as a noninvasive measuring method. However, it is remain problem whether the output from the Doppler effect sensor really detects the pure blood flow velocity.

The effect of diameter ratio between vascular substitute and blood vessel on anastomosis.

It is necessary to maintain mechanical compatibility between a blood vessel and a vascular substitute to promote encapsulation around the anastomosed part. From this point of view, using linear elastic theory, we had previously performed stress analyses at the part anastomosed by tissue adhesion, in order to propose some methods of preventing stress concentration at this junction. In this study, based on the previous analyses, we have attempted to develop a concept that can be applied under the conditions of operation.

Osteogenic differentiation of cultured marrow stromal stem cells on surface of microporous hydroxyapatite based mica composite and macroporous synthetic hydroxyapatite.

In order to investigate the significance of hydroxyapatite based microporous composite (HA/mica composite) surfaces and a macroporous synthetic hydroxyapatite, rat marrow cell culture, which shows osteogenic differentiation, was carried out on six different culture substrata (two control culture dishes, two identical HA/mica composites, and two identical macroporous synthetic hydroxyapatites). A culture period of two weeks in the presence of beta-glycerophosphate (BGP), ascorbic acid, and dexamethasone resulted in abundant mineralized nodule formations that were positive for alkaline phosphatase (ALP) stain. The stain on the macroporous synthetic hydroxyapatite and the HA/mica composites were intense, the enzyme activity being about double that of control culture dishes.

Use of porous hydroxyapatite graft containing recombinant human bone morphogenetic protein-2 for cervical fusion in a caprine model.

Object: The efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2) for enhancing anterior cervical spine interbody fusion when added to a porous hydroxyapatite (HA) graft was investigated.

Methods: Fourteen mature goats underwent three-level anterior discectomies after induction of endotracheal anesthesia. Porous HA grafts that contained 0, 5, and 50 microg of rhBMP-2 were placed concurrently with anterior cervical spine plates to achieve interbody fusion.

Osteogenesis mechanism based on kinetic theory.

In our earlier studies, we considered osteogenesis to be a nucleation mechanism accompanied by preliminary diffusion and showed the optimum mechanical conditions for promoting this ionic diffusion. In this study, we performed an analysis of the nucleation mechanism of hydroxyapatite (HA) in areas with a high concentration of transported Ca and PO4 ions in the pore region along the collagen alignment. We derived the equation of the HA nucleation rate as a function of hydrostatic tensile stress, sigma P and surface energy change (gamma-lambda), where gamma is the surface energy of the HA particle and lambda is the decreasing factor of gamma during HA nucleation.

Fracture toughness of hydroxyapatite/mica composite, packed hydroxyapatite, alumina ceramics, silicon nitride and -carbide.

By using the fracture toughness estimation method based on two-dimensional map, it was found that the ductility of the high porosity hydroxyapatite/mice composite was comparable with silicon carbide. It was measured to be higher than that of packed hydroxyapatite. Alumina ceramics with more than 96% aluminium oxide showed a higher fracture toughness than the composite material.

Microscopical imaging of hydroxyapatite/mica composite and packed hydroxyapatite structure--an atomic force microscopy investigation.

A fine grained hydroxyapatite/mica composite material was studied by the atomic force microscopy method and the results were compared with results of atomic force microscopy studies of very five grained hydroxyapatite. In the investigation it was found that the fractal dimension diagram from the atomic force microscopy studies is a tool by which mechanical properties on the surface of the material can be predicted. The two investigated materials were found to show self-similarity properties, i.

Biomechanical evaluation of hydroxyapatite intervertebral graft and anterior cervical plating in a porcine cadaveric model.

The biomechanical properties of a porous hydroxyapatite (HA) intervertebral graft with or without anterior cervical plating were evaluated in cadaveric porcine cervical spine model using C3-4 discectomy and dissection of the posterior longitudinal ligament to cause instability. The experimental groups were intact (n = 11), instability (n = 11), autogenous bone implant (n = 6), HA graft implant (n = 5), autogenous bone with plating (n = 6), and HA graft with plating (n = 5). Porous HA with 40% porosity and scapular bone were used as grafts.

Theory of osteogenesis behavior based on calcium diffusion theory.

Osteogenesis is completed by the nucleation mechanism on crystal nuclei formation and growth after amorphous calcium phosphate accretion to collagen fibers. For nuclei formation, it is necessary to have preliminary ionic diffusion such as that of Ca2+ and PO4(3-) ions to this part. Therefore, promotion of ionic diffusion to this part is the first essential condition for osteogenesis.

Mechanical test method on the estimation of the lubricant performance by hyaluronic acid.

Cases with loss of articular cartilage or lowering of articular lubricant performance are frequent among patients afflicted by various gonarthropathies or those fitted with prosthetic joints. The management of such cases has necessitated evaluation studies on the clinical efficacy of using high molecular weight hyaluronic acid as an artificial synovial fluid with a view to improving articular lubricant performance. The proper implementation of such evaluation studies on lubrication performance requires testing methods capable of assessing basic lubricant performance not only with respect to articular cartilage alone but also with respect to various other combinations of materials, i.

Mechanical test methods for biomedical membranes.

It is important to estimate the mechanical characteristics and strength of biomedical membrane. For this purpose, previously we have proposed several mechanical test methods for biomedical membranes. To establish the safety design for biomedical membrane, such as cellophane membrane for hemodialysis, it is important to estimate the viscoelastic characteristics of these materials.

The mechanical behavior and morphological structure of callus in experimental callotasis.

Experimental callotasis was made in rabbit femurs. In order to compare mechanical behaviors and morphological structure of callus in callotasis, mechanical tests and histological examination were performed. Twenty Japanese white male rabbits were used.

CAE software for the noninvasive diagnosis method on the atherosclerosis by ultrasonic Doppler effect.

Previously, we developed the noninvasive estimation method on the viscoelastic deterioration of the blood vessel and related materials by using Ultrasonic Doppler Effect Sensor and we presented its theoretical foundation. Furthermore, we applied this method to discriminate the human blood vessels with atherosclerosis from normal blood vessels, as the viscoelastic deterioration under in vitro condition and proposed the algorithm for its diagnosis. In the present paper, we propose the software for personal computer (AORTA) for clinical diagnosis on the atherosclerosis within a few minutes by using Ultrasonic Doppler Effect Sensor based on this algorithm.

Algorithm of the noninvasive diagnosis method on the atherosclerosis by ultrasonic Doppler effect.

Previously we proposed Acoustical Imaging and Processing Method to measure the viscoelastic property of the blood vessels of a canine and the related materials using Ultrasonic Doppler Effect Measurement. Furthermore, its theoretical foundation was presented. In this paper, this method is applied to measure the viscoelastic mechanical property, that is, the mechanical degradation of human blood vessels by a percutaneous noninvasive method.