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  • Creep indentation  (1)
  • titanium  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 23 (1995), S. 697-704 
    ISSN: 1573-9686
    Keywords: Tibiotalar joint ; Articular cartilage ; Material properties ; Creep indentation ; KLM biphasic theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The material properties of normal cadaveric human cartilage in the ankle mortice (tibiotalar articulation) were evaluated to determine a possible etiologic mechanism of cartilage injury of the ankle when an obvious traumatic episode is not present. Using an automated indentation apparatus and the biphasic creep indentation methodology, creep indentation experiments were performed in five sites in the distal tibia, one site in the distal fibula, and eight sites in the proximal talus of 14 human ankles (seven pairs). Results showed significant differences in the mechanical properties of specific human ankle cartilage regions. Topographically, tibial cartilage is stiffer (1. 19 MPa) than talar cartilage (1.06 MPa). Cartilage in the anterior medial portion of the tibia has the largest aggregate modulus (H A =1.34 MPa), whereas the softest tissue was found to be in the posterior lateral (0.92 MPa) and the posterior medial (0.92 MPa) regions of the talus. The posterior lateral ridge of the talus was the thickest (1.45 mm) and the distal fibula was the thinnest (0.95 mm) articular cartilage. The largest Poisson's ratio was found in the distal fibula (0.08). The lowest and highest permeability were found in the anterior lateral regions of the astragalus (0.80 × 10−15 m4N−1sec−1) and the posterior medial region of the tibia (1.79 × 10−15 m4N−1sec−1), respectively. The anterior and posterior regions of the lateral and medial sites of the tibia were found to be 18–37% stiffer than the anatomically corresponding sites in the talus. The biomechanical results may explain clinically observed talar dome osteochondral lesions when no obvious traumatic event is present. Cartilage lesions in a repetitive overuse process in the ankle joint may be related to a disparity of mechanical properties between the articulating surfaces of the tibial and talar regions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 36 (1997), S. 516-521 
    ISSN: 0021-9304
    Keywords: porous-coated ; titanium ; PLA-PGA ; protein release ; degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tissue ingrowth into porous-coated orthopedic and dental implants is commonly used as a means to achieve long-term fixation of these prostheses. However, the degree of tissue ingrowth is often inadequate and inconsistent. If the pores of these implants are impregnated with a controlled drug release system delivering relevant growth factors, then it might be possible to stimulate more tissue ingrowth. The present study introduces such a system based on biodegradable polymers and investigates its protein release profile and polymer degradation characteristics. Porous coated titanium implants were impregnated with a mixture of a 50%-50% polylactic acid-polyglycolic acid copolymer and a model protein, soybean trypsin inhibitor. Control implants contained only the polymer and no protein. The implants were subjected to hydrolytic degradation in phosphate buffered saline at 37°C for periods of 3, 6, and 11 weeks. The protein release and the mass and molecular weight of the polymer were monitored. The results indicate that the protein is released in three distinct phases and the polymer loses almost all its mass and molecular weight by 11 weeks. There was a significant difference in the polymer degradation characteristics between the control and test implants, which might be the result of some complex polymer-protein interactions. © 1997 John Wiley & Sons, Inc. J Biomed Mater Res, 36, 516-521, 1997.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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