Journal of Biomechanical Science and Engineering
Online ISSN : 1880-9863
ISSN-L : 1880-9863
Volume 4, Issue 4
Special Issue on Mechanical Behavior of Soft Tissues and their Substitutes
Displaying 1-11 of 11 articles from this issue
Special Issue on Mechanical Behavior of Soft Tissues and their Substitutes
Review(Special Issue)
  • Hazel R.C. SCREEN
    2009 Volume 4 Issue 4 Pages 481-499
    Published: 2009
    Released on J-STAGE: November 10, 2009
    JOURNAL FREE ACCESS
    Using the basic building blocks of collagens, elastins and proteoglycans, the human body is capable of manufacturing our large range of different structural tissues. Understanding how these structural components combine to create such widely varying tissues with diverse mechanical characteristics is a topic of interest for a range of research areas. However, probing the sub-structural mechanics to investigating these structure-function relationships is complex, as the series of hierarchical levels in connective tissues range in size from the Angstrom to millimeter level. Tendon has received considerable interest, as its simple aligned structure provides a promising route for investigating structure-function relationships. Tendon is an aligned, multi-level fibre composite structure, built predominantly from the collagen molecule to make a material with excellent tensile strength. The paper reviews the current state of research relating to tendon structure-function behaviour throughout the tendon hierarchy, building from the collagen molecule at the nano scale to the complete tendon.
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Papers(Special Issue)
  • Yutaku KANETA, Hisashi OHKAWA, Yushi SUZUKI, Toshiaki HARA, Yoshihiro ...
    2009 Volume 4 Issue 4 Pages 500-509
    Published: 2009
    Released on J-STAGE: November 10, 2009
    JOURNAL FREE ACCESS
    The liver is one of the injury regions impacted by the steering wheel during a traffic accident. Therefore, in the field of impact biomechanics, the study of the liver has attracted considerable interest. We consider the case of abdominal compression by a steering wheel and perform quasi-static compression tests using a full-scale porcine liver that is not shaped into a cylinder or a cube in order to determine the basic mechanical properties of an unaltered liver. A human liver and a porcine liver have different structures; the former is divided into two regions (right and left lobe), while the latter is divided into four regions (right medial, right lateral, left medial, and left lateral lobe). Therefore, we compared the compressive properties of the four regions of the porcine liver using a cylindrical indenter to simulate the effect of the steering wheel of a passenger car. No significant differences were observed among the four porcine liver regions. Next, we compared the differences in mechanical properties, behaviors, and injury patterns of the porcine liver by using four compressive indenter profiles. The indenters were made from an acrylic resin. Although the injury patterns were different, yield loads were observed under an approximately constant compressive ratio regardless of the compressive indenter profile.
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  • Eijiro MAEDA, Julia C. SHELTON, Dan L. BADER, David A. LEE
    2009 Volume 4 Issue 4 Pages 510-517
    Published: 2009
    Released on J-STAGE: November 10, 2009
    JOURNAL FREE ACCESS
    Intermittent pattern of mechanical stimulation has been demonstrated to possess different regulatory effects on cell metabolism in many connective tissues, but little is known about tenocyte responses. A previous study has shown that the application of a small number of continuous cyclic strain inhibited collagen synthesis by tenocytes in explants, whereas a large number of strain cycles upregulated the synthesis. Thus, the present study tested the hypothesis that collagen synthesis is influenced by cyclic tensile strain provided in an intermittent manner. A total of 43,200 cycles of tensile strain, with a 3% amplitude superimposed on a 2% static strain was provided in four different intermittent patterns with different strain/unstrain periods: 10 minutes, 1 hour, 6 hours, and 12 hours. The amount of newly synthesised collagen, both those retained in strained fascicles and released into culture media, were not significantly altered by the application of different patters of intermittent cyclic strain. The present findings may suggest that, unlike other connective tissue cells, tenocyte responses are predominantly regulated by the total number of strain cycles.
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  • Takeo MATSUMOTO, Tomohiro FUKUI, Toshihiro TANAKA, Naoko IKUTA, Toshir ...
    2009 Volume 4 Issue 4 Pages 518-529
    Published: 2009
    Released on J-STAGE: November 10, 2009
    JOURNAL FREE ACCESS
    Mechanical properties of human aortic aneurysm tissues were measured with a biaxial tensile tester. Fifteen-mm-square specimens were obtained from thoracic aortic aneurysms of various origins and from undilated aortas adjacent to the aneurysms during aneurysmectomy, and were stored frozen until the measurement. Each specimen was stretched biaxially in physiological saline at room temperature at the rate of ∼0.2 mm/sec. Although the ordered displacement was set equal for both directions, real strain applied to the specimens was not equibiaxial. The stress-strain curves under equibiaxial stretch were obtained by fitting measured curves with a strain energy function considering material anisotropy. Effects of freezing and ambient temperature on the mechanical properties were evaluated with porcine thoracic aortas. The mechanical properties of the frozen-stored specimens at 23°C were almost similar to those of the fresh specimens at 37 °C. Elastic modulus at zero load averaged for both directions Hmi = (Hxi+Hyi)/2 was higher (P < 0.01) in the aneurysm tissues (1450 ± 250 kPa, mean ± SEM, n = 26) than in the undilated tissues (650 ± 140 kPa, n = 10). Anisotropy index K = |Hxi-Hyi|/Hmi was not significantly different between the aneurysm (20 ± 3%) and the undilated tissues (12 ± 3%) for all specimens. For the specimens whose elastic modulus Hmi was smaller than 1 MPa, however, the index K was significantly higher (P < 0.05) in the aneurysm specimens (23.1 ± 5.3%, n = 14) than the undilated tissues (9.5 ± 2.5%, n = 8). These results indicate aneurysm tissues are not only stiffer but also more anisotropic than the nonaneurysmal tissues.
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  • Noritaka YAMAMOTO, Takashi OTA
    2009 Volume 4 Issue 4 Pages 530-538
    Published: 2009
    Released on J-STAGE: November 10, 2009
    JOURNAL FREE ACCESS
    The mechanical and morphological properties of patellar tendons were in vivo measured during isometric knee extension contractions in ten male subjects using ultrasonography. The subjects were accustomed to various exercise and training. The stiffness, cross-sectional area, and tangent modulus of the patellar tendons were positively correlated with the quadriceps strength. The enhancement of contractile forces induced by exercise and training increases the quadriceps strength. Since the primary role of patellar tendons is the transmission of contractile forces from quadriceps to tibia, the contractile forces are directly applied to the patellar tendons. Therefore, in the subjects with the larger quadriceps strength, the forces applied to the patellar tendons during exercise and training may be larger, and the force enhancement may induce the increases in the stiffness, cross-sectional area, and tangent modulus of the patellar tendons.
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  • Ei YAMAMOTO, Kousuke OHTA
    2009 Volume 4 Issue 4 Pages 539-549
    Published: 2009
    Released on J-STAGE: November 10, 2009
    JOURNAL FREE ACCESS
    Incomplete or subfailure injuries of tendons occur more frequently than their complete ruptures. However, the mechanical behavior of the incompletely injured tissues is poorly understood. In the present study, we quantified the mechanical properties, microstructure, and ultrastructure of rabbit patellar tendons subjected to non-destructive overloading. No significant changes in the mechanical properties were observed in the tendon specimens which were applied a subfailure stretch equivalent to 80% of the failure stress of the control tendons at a low strain rate (1.67 %/sec). There was a significant decrease not in the tensile strength but in the tangent modulus of the specimens when they were subjected to 90% of the control failure stress at the low rate. For the same level of overloading at a high strain rate (16.7 %/sec), both the modulus and strength of the overloaded specimens were significantly lower than those of the control ones. Microstructually, irrespective of the strain rate, crimped collagen fibers in the overloaded tendons were straightened by the 90% overloading. In contrast, adverse alterations in the ultrastructure were induced by the 90% overloading only at the high rate. These results indicate that tendinous tissues have potential capacities to maintain the original strength if a relatively high overload is monotonically applied at lower strain rates. However, it is possible that subfailure overloads delivered at higher strain rates produce more severe changes in the properties and structures of the tissues.
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Papers
  • Yoshihiro TAKAO, Junpei TAKAHASHI, Masahiko TERAJIMA, Wen-Xue WANG, Ak ...
    2009 Volume 4 Issue 4 Pages 550-561
    Published: 2009
    Released on J-STAGE: November 20, 2009
    JOURNAL FREE ACCESS
    In recent years, the number of patients with mandibular defects is increasing, and the orthognathic surgery of mandible has become a common treatment for re-establishing functional and aesthetic anatomy by repositioning displaced skeletal elements. To decrease a heavy burden and high risk of the surgery falling on the patients and clinicians, the present authors have developed a mechanical support system for orthognathic surgery. An easy, quick and patient-specific mesh generation including the periodontal ligament is essential. First, a mandible template was obtained manually, which requests the small number of elements. It is composed of 7 different materials and could reproduce the original shape of each material pretty well with a reduced number of elements. Next the template of around 6600 nodes is mapped by a simple formula in a moment of time to fit the patient's mandible polygonal image obtained from an individual CT image. The calculation with the resulted patient-specific mesh by a 3D FEM code is also performed successfully.
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  • Yasuju TAKANO, Masaru UENO, Kazuo KIGUCHI, Syuya IDE, Masaaki MAWATARI ...
    2009 Volume 4 Issue 4 Pages 562-575
    Published: 2009
    Released on J-STAGE: December 02, 2009
    JOURNAL FREE ACCESS
    To evaluate motions and joint reaction forces of the total knee prosthesis during deep knee flexion such as kneeling and sitting straight, a simulator that reproduces the passive motion of the knee has been developed. The main feature of the simulator is that the knee joint is accurately and repeatedly moved from 0° to 180° flexion angle in six degrees of freedom. Moreover, the tibiofemoral and patellofemoral motion and joint reaction forces can be continuously measured. Assuming that muscular force is mainly generated with a quadriceps femoris muscle, the similar force vector is produced by two motors. The custom-designed posterior stabilized type total knee prosthesis which can be flexed to 180° has been inserted in the bone model and used for the evaluation. As a result, it was confirmed that this simulator was able to measure the motion and joint reaction force of the knee with high repetition accuracy. The experimental results showed the same tendency with those in the previously performed cadaveric experiment until 120° flexion. Hereafter, cadaver knee can be used for the evaluation of the knee prosthesis using the proposed simulator with high accuracy.
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  • - A Mechanical Analogy Method -
    Seishin TAKAO, Shigeru TADANO, Hiroshi TAGUCHI, Hiroki SHIRATO
    2009 Volume 4 Issue 4 Pages 576-588
    Published: 2009
    Released on J-STAGE: December 04, 2009
    JOURNAL FREE ACCESS
    A new simulation method was developed that considered a tumor as a solid body and therapeutic response as deformation of the tumor using mechanical analogy. As radiation exposure to the tumor was related to the external force to the solid body, the geometrical change of the tumor could be estimated from fundamental equations in solid mechanics. A change in tumor volume was calculated using finite element (FE) method. The FE models were constructed from CT images of patients before the radiotherapy. The initial radiotherapeutic parameters of tumor radioresistance and repopulation rate were determined based on a linear-quadratic model and then revised by the comparison with actual tumor volume change. Three patients with uterine cervix carcinoma were applied in this method. Simulation results well showed tendencies of tumor volume changes with radiotherapy. In addition, this method could provide the appropriate value of radiotherapeutic parameters for individual case. In conclusion, our approach could calculate three-dimensional tumor deformation during the course of radiotherapy and will provide useful information for more effective treatment.
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  • Satoshi TERAMURA, Hideyuki SAKODA, Tomohiro TERAO, Kunihiko FUJIWARA, ...
    2009 Volume 4 Issue 4 Pages 589-596
    Published: 2009
    Released on J-STAGE: December 24, 2009
    JOURNAL FREE ACCESS
    Accelerated ageing was conducted on UHMWPE with and without vitamin E (D, L-α tocopherol, VE). Wear performance was investigated using a knee simulator and wear debris was analysed. Aged UHMWPE with VE showed significantly lower wear volume than that of aged virgin UHMWPE and showed approximately similar wear volume as non-aged virgin UHMWPE. There were no significant differences among the materials as far as shape factor of the debris is concerned.
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