Bio-Medical Materials and Engineering - Volume 6, issue 6

Authors: Trochu, F. | Brailovski, V. | Meunier, M.-A. | Terriault, P. | Qian, Y.Y.

Article Type: Research Article

Abstract: Shape memory alloys (SMA) are being increasingly used in various industrial applications as actuators, connectors, or damping materials. In the medical field, superelastic devices such as eyeglass frames, stents or guide catheters have come to market in the recent years. The design of SMA devices has usually been based on trial and error, since until recently no general simulation model was available to assist application engineers. The purpose of this article is to describe the computational methodology developed, validated and used for several industrial projects at École Polytechnique of Montréal to simulate the therrnomechanical behavior of shape memory materials. This …new approach includes three main stages: experimental characterization, construction of a nonlinear material law based on dual kriging interpolation and finally, calculation of the thermomechanical response of SMA devices. For complex geometry, finite element analysis is used, but for simple devices such as springs or electrically activated SMA wires, simplified calculation methods are satisfactory. Validation results recently obtained will also be presented, and examples of industrial applications briefly reviewed. Show more

DOI: 10.3233/BME-1996-6601

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 389-403, 1996

Authors: Kikuchi, Masanori | Yamazaki, Astsushi | Akao, Masaru | Aoki, Hideki

Article Type: Research Article

Abstract: Barium hydroxyapatite (Ba10 (PO4 )6 (OH)2 , Ba-HAp) was synthesized by a wet method using Ba(OH)2 ·8H2 O and (NH4 )2 HPO4 as starting materials. The Ba-HAp obtained had a Ba/P atomic ratio of 1.76 and contained CO3 groups. The Ba-HAp was sintered at 1073 K for 12 hours. The sintered Ba-HAp had a three point bending strength of 29 MPa and Young's modulus of 27 GPa. Cytotoxicity of the sintered bodies and particles was tested using L-cells. The sintered Ba-HAp showed no cytotoxicity, and the cells were closely in contact with the surfaces of sintered Ba-HAp. Morphological …observation of the cell around the Ba-HAp particles also showed no cytotoxicity. However, cell growth was inhibited by Ca adsorption on the Ba-HAp particles. These results suggested that the Ba-HAp had no cytotoxicity and can be applied as a bioactive X-ray opaque material. Show more

Keywords: Barium hydroxyapatite, mechanical strength, cytotoxicity, Ca adsorption, cell growth inhibition

DOI: 10.3233/BME-1996-6602

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 405-413, 1996

Authors: Chan, Francis H.Y. | So, Albert T.P. | Lam, F.K.

Article Type: Research Article

Abstract: To visualise non-invasively human organs in their true form and shape has intrigued mankind for centuries. Three-dimensional (3D) imaging is one recent development that has brought us closer to fulfilling the age-old quest of non-invasive visualisation so that diagnoses by doctors can be efficiently enhanced. Nowadays, 3D CT and MRI images have been very popular. Thermography is an important medical imaging technique that displays the temperature distribution on the surface of a human organ and it has been proved to be significant in offering a unique physiological reflection of pathology that may confirm or enhance the anatomic findings of other …diagnostic imaging modalities. It is the only imaging modality that can evaluate pain whereas plain radiographs, CT and MRI, etc. can only depict structural anatomic abnormalities that may not always coincide with patients' clinical complaints. It is against this background that 3D thermograms have been developed. A set of comprehensive calibration procedures for the 3-camera system have been designed based on different models for the optical and infrared cameras. The accuracy of the results is high enough to produce 3D thermograms that can be used to correlate with the 3D images from other medical imaging modalities. One important achievement of the system is that the resultant 3D images are absolutely dimensioned and hence, it is particularly favourable for fully autonomous applications with robots. The system can also provide an overall picture of both the structural abnormalities and nervous responses of patients. Show more

Keywords: 3D imaging, thermography, camera calibration, image reconstruction

DOI: 10.3233/BME-1996-6603

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 415-428, 1996

Authors: Frigstad, John R. | Park, Joon B.

Article Type: Research Article

Abstract: The changes in the mechanical response of a bone cement reinforcement, comprised of a continuous stainless steel coil imbedded within the PMMA bone cement matrix surrounding the distal tip of the total hip arthroplasty, was investigated. To achieve this, a 3D finite element model depicting two and one half rotations of the coil imbedded within the cement at the distal tip was constructed. Ideally, the wire coil should reduce the radial, and to a greater extent, the hoop stresses developing within the cement and at the cement-stem interface. As a means of comparison, a control model of only bone cement …was also built. For the radial stresses, the control had about 4.5 times the compressive stress of the reinforced models (0.039 (± 0.00065) MPa vs. 0.0087 (± 0.0012) MPa) at the cement-stem interface. The tensile hoop stresses were also 4.5 times higher (4.272 (± 0.0147) MPa and 0.95 (± 0.0052) MPa) for the control than for the reinforced models. This indicates that the wire coil reinforcement is effective in reducing the cement mantle's radial and, more importantly, the hoop stresses which may lead to the failure of both the cement and the implant as a whole. Show more

Keywords: Finite element model, stainless steel wire reinforcement, bone cement, fixation, hoop stress, radial stress

DOI: 10.3233/BME-1996-6604

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 429-439, 1996

Authors: Ohashi, Minako | Tomita, Naohide | Ikada, Yoshito | Ikeuchi, Ken | Motoike, Toshio

Article Type: Research Article

Abstract: Ultra high molecular weight polyethylene (UHMWPE) has been used in artificial joints for a few decades, and wear of UHMWPE has been one of the main problems. Though many other materials have been tested over the years, the best clinical results are still achieved with UHMWPE. This makes the study of UHMWPE, especially in relation to artificial joints, very important. Frequently, more severe wear can be observed in artificial knee joints than in artificial hip joints especially when the flaking-like wear occurs. This flaking-like wear can lead to significant destruction of the artificial knee joint. Macroscopically, artificial knee joints have …combinational movements of rolling and sliding in order to simulate the motion of the normal knee joint. The components of motion are separated to make study easier. Fatigue tests of UHMWPE under the rolling contact condition were performed in this study. Three ceramic spheres were rolled over the UHMWPE specimen using 37°C distilled water as a lubricant. The UHMWPE specimen was observed by the scanning acoustic tomography, microscopy, and SEM. Some subsurface defects could be observed by SAT even before experiments. Although the apparent wear is not observed on the surface, there was an increase in the number of observable subsurface cracks in the UHMWPE specimen. This shows that cracks occur under the surface after a 107 rolling contact loading, which is very close to the cyclic loading and unloading with very little friction compared to the sliding contact. Show more

Keywords: Fatigue, wear, UHMWPE, SAT, artificial knee joint

DOI: 10.3233/BME-1996-6605

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 441-451, 1996

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

Article Type: Research Article

Abstract: The longevity of the cemented total hip joint replacement depends on the integrity of the cement fixation with respect to the interfaces of the metal stem and bone, and stress/strain transmission and its distribution. A simple stainless steel wire coil was placed around a tapered stem in a simulated cement mantle to counteract radial- and hoop-stress and dynamic compression-compression tests were performed. The results showed that the wire coil reinforced cement group had a higher fatigue (30%) and strength (35%) up to 105 loading cycles. The amount of stem subsidence during fatigue tests of the wire reinforced group was …significantly reduced (2.5 times) compared with the control group. Show more

Keywords: Wire coil, total hip joint replacement, bone cement, fatigue test, reinforcement, subsidence, creep

DOI: 10.3233/BME-1996-6606

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 453-462, 1996

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 463-466, 1996

Article Type: Other

Citation: Bio-Medical Materials and Engineering, vol. 6, no. 6, pp. 467-468, 1996