Bio-Medical Materials and Engineering - Volume 5, issue 1

Authors: Guglielmino, E. | La Rosa, G. | Russo, T.C. | Torrisi, L.

Article Type: Research Article

Abstract: Metallic screws are becoming more and more useful to join bones or for prothesis support in orthopaedic and dental surgery. High biocompatible materials such as titanium alloys and hydroxyapatite ceramics are making possible the realization of stable fixation devices utilizable in load-bearing applications. The mechanical and biological anchorage of metallic screws to the bone depends on many factors: mechanical screws-bone thread matching, use of cements between bone and screw, chemical-physical treatments of screw surface, use of screw coverage films based on osteointegrating ceramics or active bioglasses, use of porous coverage films to induce bone ingrowth into the pore, and so …on. The first step of the research, the aim of the present paper, is the comparison among screws of different shapes and geometric characteristics in order to find the best macromechanical system versus the different load conditions. Static and dynamic tests are applied to the screws mounted on segments of pig spine, in order to measure the mechanical characteristics of the system under tension (pull-out), bending on the principal planes along the axis of the screw and fatigue loads. Physical analysis, obtained using energetic charged particles, such as SEM, RBS, and AES, are used to charactelize the screw surface compositions and morphology. Show more

Keywords: spinal surgery, biocompatible screws, bio-mechanical adhesion

DOI: 10.3233/BME-1995-5101

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 1, pp. 1-7, 1995

Authors: Lin, Shan-Yang | Duan, Kow-Jen | Lin, Tsung-Chien

Article Type: Research Article

Abstract: The structural changes in the lipid of the excised skin of nude mice and the porcine stratum corneum was investigated by in vitro treatment with vitamin C, oleic acid, or DMSO. The CH2 stretching vibrational peaks of lipid near 2920 cm−1 (asymmetric) and 2850 cm−1 (symmetric) shifted to higher wavenumber due to the lipid-disorder after in vitro treatment with above enhancers. The spectral shift of the asymmetric CH2 band was more sensitive than that of the symmetric CH2 band. The higher wavenumber of CH2 stretching bands decreased gradually to the lower region after co-treatment …or posttreatment with pyrrolidone carboxylate sodium (PCA Na). Such a decrease was dependent on the PCA Na concentration and the time of treatment. The higher the concentration of PCA Na used, the lower value of the permeability coefficient of vitamin C through the excised skin and the downward spectral shift of asymmetric CH2 band were obtained. When PCA Na coexisted with vitamin C in the cell donor compartment, a competitive effect between PCA Na and vitamin C was found. The oleic acid was supposed to directly insert it into the lipid structure to form a rigid structure, leading to larger spectral shift of both stretching bands but lesser restoring ability after PCA Na treatment. However, DMSO only displaces water from the lipid head groups and protein domain of skin to indirectly loosen the lipid structure, resulting in lesser spectral shift of the CH2 stretching bands to higher region, which was easier and better restoration after PCA Na application. The PCA Na enabled to restore the disordered lipid structure to order state might be attributed to PCA Na previously penetrated into skin and then absorbed water to directly or indirectly rearrange the disordered lipid bilayer structure. Show more

Keywords: excised nude mice skin, porcine stratum cornum, penetration enhancers, vitamin C, oleic acid, DMSO, pyrrolidone carboxylate sodium, lipid-order, lipid-disorder, stretching vibrational band, scissoring band, permeability coefficient, restoration

DOI: 10.3233/BME-1995-5102

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 1, pp. 9-20, 1995

Authors: Nakamura, Takao | Yamauchi, Yoshiko | Kawahara, Koichi

Article Type: Research Article

Abstract: Influences of lower frequency components of power spectrum calculated from biological rhythm data on the spectral slope were examined and the validity of conventional method to calculate the spectral slope was tested. Heart-beat-period data obtained from the electrocardiogram of rats were cut into two successive data sets, each of them was converted into power spectrum density by the fast Fourier transform, and the power spectra were compared with each other. The results showed that two spectra were overlapped only in the frequency range higher than a frequency about 15 times that of the dominant one, which means that the lower …frequency components are not always the same and thus, the regression line by which the spectral slope is determined is considerably affected by the components. To evaluate the spectral slope, regression lines of spectra were obtained in three methods and their slopes were compared with each other. The methods were: “conventional” method, in which the weight of a frequency component was independent of the frequency (i.e., equal-weight = 1); “weight” method, in which the weight was the wave number included in the rhythm data; and “limited-data” method, where the weight was 1 and lower-frequency components were excluded, The results showed that there was not a large difference between the slopes in cases where the spectrum looked rather linear. However, in cases of considerably curved spectra the difference was large and the “weight” method may be the most reasonable to use, and in cases of short data length the “limited-data” method should be avoided. Show more

Keywords: 1/f fluctuation, fast Fourier transform, power spectrum density, regression line

DOI: 10.3233/BME-1995-5103

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 1, pp. 21-28, 1995

Authors: Grosland, Nicole | Kim, Jeong K. | Park, Joon B.

Article Type: Research Article

Abstract: The longevity of cemented total joint replacements, namely total hip arthroplasty (THA), depends on the integrity of the cement per se and interfaces of the metallic stem-cement and bone-cement, and stress/strain transmission and its distribution. A simple coil made of stainless steel wire was placed around a tapered stem in a simulated cement mantle to counteract the radial- and hoop-stresses created by the stem loading. Two-dimensional axisymmetric finite element analysis was performed to elucidate the level of the stress and its distribution with and without the wire coil. The results suggest that the peak stresses distributed throughout the cement may …be reduced by more than one half, via the incorporation of a wire coil, confirming the mechanical test results, which showed an average fracture load of 3.70 ± 1.13 kN for pure bone cement control and 9.02 ± 1.54 kN for the wire coil reinforced specimens. These results indicate that the reinforcement of the cement mantle with a wire coil in the distal end of the hip stem prosthesis could reduce the hoop-stresses, which may results in reduced stresses in the bone and cement interface. Consequently, loosening of the interfaces of the bone-cement and cement-stem could be reduced due to the enhanced fatigue life of the bone cement mantle with favorable stress distribution at the distal tip of the stem. Show more

Keywords: finite element model, bone cement, fixation, wire coil reinforcement, mechanical properties

DOI: 10.3233/BME-1995-5104

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 1, pp. 29-36, 1995

Authors: Thompson, J.I. | Czernuszka, J.T.

Article Type: Research Article

Abstract: Samples of collagen were cross-linked by two different methods: (a) glutaraldehyde and (b) a combination of dehydrothermal treatment and cyanamide. The elastic modulus, the ultimate tensile strength (fracture stress), strain to failure, work of fracture, and fracture toughness were measured before and after cross-linking in ambient laboratory conditions, and during immersion in water. These tests were all performed over a range of strain rates. For collagen tested in the wet condition, it was found that cross-linking increased the elastic modulus from approximately 25–30 MPa, to between 55 and 60 MPa, but there was little effect on fracture stress, and …strain to failure was reduced. The work of fracture of the collagen decreased on cross-linking. Cross-linking had the same effect on the elastic modulus, fracture stress, and strain to failure of dry collagen, but the work of fracture was unaffected. In conclusion, cross-linking increased the elastic modulus, reduced the strain to failure, and had little effect on the fracture stress of collagen under the present experimental conditions. Show more

Keywords: collagen, cross-linking, mechanical properties

DOI: 10.3233/BME-1995-5105

Citation: Bio-Medical Materials and Engineering, vol. 5, no. 1, pp. 37-48, 1995