Soft tissues modulus

Vascular access ports typically consist of a self-sealing siUcone septum within a rigid housing which is attached to a radiopaque catheter (see Radiopaques). The catheter must be fabricated from a low modulus elastomeric polymer capable of interfacing with both soft tissue and the cardiovascular environment. A low modulus polyurethane-based elastomer is preferred to ensure minimal trauma to the fragile vein. 

The PGS obtained by Wang and coworkers was a kind of thermoset elastomer with the Young s modulus of 0.282 0.025 MPa, a tensile strain of at least 267 zE 59.4%, and a tensUe strength was at least 0.5 MPa. The mechanical properties of PGS were well consisted with that of some common soft tissues. Although PGS is a thermoset polymer, its prepolymer can be processed into various shapes by solving it in common organic solvents such as 1,3-dioxolane, tetrahydrofuran, isopropanol, ethanol, and iV,M-dimethylformamide. Porous scaffolds can be fabricated by salt leaching. 

High modulus or stiffness of cured polymers at soft tissue application sites and associated mechanical incompatibility, which can lead to adhesive joint failure and/or irritation of the surrounding tissue... 

Both perilymph and endolymph have the viscosity and density of water. The bone of the wall and the bony shelf appear to be similar to compact bone, with density approximately twice that of water. The remaining components of the cochlea are soft tissue with density near that of water. The stiffnesses of the components vary over a wide range, as indicated by the values of Young s modulus listed in Table 63.1. These values are taken directly or estimated from many sources, including the stiffness measurements in the cochlea by Bekesy [1960], Gummer and coworkers [1981], Strelioff and Flock [1984], Miller [1985], Zwislocki and Cefaratti [1989], and Olson and Mountain [1994]. 

Some of these pol miers and copolymers do not possess the mechanical properties that are required for certain applications. For example, as implants for soft tissue poly(lactide)s, poly(glycolide)s, PCL, poly(dioxanone) and their copolymers may require increased flexibiUty and a modulus of elasticity that is closer to soft tissue. 

Some hydrogels, due to their water content, provide a more flexible structure that is similar to soft tissue. Therefore, by combining the pol5uners that lack certain required mechanical properties such as a suitable modulus of rigidity or modulus of elasticity with hydrogels, suitable degradation and drug delivery properties are obtainable and an exterior is achieved that has mechanical properties similar to the mechanical properties of soft tissue. 

The paper reports a noninvasive technique to measure the mechanical properties of the bulk soft tissues by a pulsed ultrasonic Doppler system. An ultrasonic transducer was used to measure internal displacement resulting from external acoustical perturbations. Measurements were made at four sites of 8 aboveknee residual limbs. The Young s moduli were found in a range of 53-141 kPa. Superficial tissue had a significantly higher modulus than the tissue beneath. 

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