Bio-Medical Materials and Engineering - Volume 7, issue 4

Authors: Kumaresan, Srirangam | Yoganandan, Narayan | Pintar, Frank A.

Article Type: Research Article

Abstract: The present study investigated the external and the internal biomechanical responses of anterior cervical discectomy coupled with fusion. Five different types of interbody fusion materials were used: titanium core, titanium cage, tricortical iliac crest, tantalum core, and tantalum cage. Two different types of surgical procedures were analyzed: Smith-Robinson and Bailey-Badgley. A validated three-dimensional anatomically accurate finite element model of the human cervical spine was used in the study. The finite element model was exercised in compression, flexion, extension, and lateral bending for the intact case and for the two surgical procedures with five implant materials. The external response in terms …of the stiffness and angular rotation, and the internal response in terms of the disc and the vertebral stresses were determined. The Smith-Robins on technique resulted in the highest increase in external response under all modes of loading for all implant materials. In contrast, the Bailey-Badgley technique produced a higher increase in the disc and the vertebral body stresses than the Smith-Robinson technique. As experimental human cadaver tests can only determine the external response of the non-fused spine simulating immediate post-operative structure, the present finite element studies assist in the understanding of biomechanics of interbody fusion by delineating the changes in the extrinsic and intrinsic characteristics of the cervical spine components due to surgery. Show more

Keywords: Biomaterial, cervical spine, finite element analysis, fusion, discectomy, titanium and tantalum implants

DOI: 10.3233/BME-1997-7401

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 221-230, 1997

Authors: Lewis, Gladius | Shaw, Kevin M.

Article Type: Research Article

Abstract: Uniaxial quasi-static tensile stress, σ, versus strain, ε, data were obtained from 29 cadaveric Achilles tendons (donor ages: 36 to 100 years), at a strain rate of either 10 or 100%/s. These results were then used in modeling the elastic component of the tensile deformational behavior of this tissue. Two approaches were taken. In the first, it was shown that the following constitutive relation provided an excellent fit to the elastic section of the σ−ε curve, σ=Cεexp[Dε+Fε2 ], with C, D and F being material constants, whose values for the present dataset were found to be C = …2.00 ± 0.99, D = 0.089 ± 0.087 and F = −0.0047 ± 0.0095. The values of these coefficients were not statistically significantly affected by either donor age or test strain rate. In the second approach, the value of the modulus of elasticity of a filamentary polymer matrix composite material was computed as a function of various combinations of values of the modulus of elasticity of the fiber, the modulus of elasticity of the matrix, and angle of orientation of the principal material axes with respect to the reference coordinate axes (θ) for a fiber volume fraction of 0.6 and a material Poisson's ratio of 0.4. By comparing these results with the experimentally-obtained values of the tangent modulus of elasticity of the tendons (defined as the slope of the linear section of the post-toe zone in the σ−ε plot), and assuming that the tendon may be idealized as a filamentary polymer matrix composite material, the suggestion is made that the winding angle of the fibers (collagen fibrils) in the tendon (taken to be equal to θ) is about 6°. Show more

Keywords: Achilles tendon, constitutive relation, composite material

DOI: 10.3233/BME-1997-7402

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 231-244, 1997

Authors: Frigstad, John R. | Kang, Yoon H. | Park, Joon B.

Article Type: Research Article

Abstract: The hoop and axial strains present due to loading after femoral stem implantation in canine femurs, implanted with and without a wire coil surrounding the distal tip were investigated. One stem served as the control without wire coil while the other was experimental reinforced with a wire coil. Both stems were implanted by identical methods. Ideally, the wire coil should serve to reduce the hoop and axial strains present in the distal tip of the arthroplasty. The strains were measured using 90° rosette strain gages. Though the coil's position was altered slightly during implantation usable results were still obtained. At …a maximum load of 44.5 N there were 32 and 19% reduction in the hoop and axial strains for the reinforced stem and the control, respectively. This experiment presents a striking difference between the control and reinforced hip arthroplasties. Equally important is that this study confirms the trends in hoop and axial strain behavior demonstrated in other works utilizing a wire coil reinforcement scheme. The simple method of applying a continuous wire coil may help to reduce the loosening of femoral stem of total hip arthroplasty by reducing strains at the tip of the stem due to the strengthening of the cement mantle. Show more

DOI: 10.3233/BME-1997-7403

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 245-251, 1997

Authors: Kim, Tae-In | Han, Jun-Hyun | Lee, In-Seok | Lee, Kyu-Hwan | Shin, Myung-Chul | Choi, Boo-Byung

Article Type: Research Article

Abstract: Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals.

Keywords: Dental implant, mechanical properties, corrosion, Ti-based alloys, cytotoxicity

DOI: 10.3233/BME-1997-7404

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 253-263, 1997

Authors: Zuccari, A.G. | Oshida, Y. | Okamura, M. | Paez, C.Y. | Moore, B.K.

Article Type: Research Article

Abstract: Articulating paper/film is a sheet strip that is coated with ink- or dye-containing wax and is used for marking occlusal contacts and monitoring the results. New types of occlusal film systems have been developed recently, which are capable of being computer-interfaced to identify the occlusal contact points and digitize the occlusal force. The mechanical ductility and thickness of these occlusal sheets constitute some of their important properties. The objective of this study was to evaluate seven different occlusal sheets and compare their bulge ductility and thickness. A custom-designed photo-sensing bulge tester was used. Three paper-based sheets (BAP, BET and SFA), …two plastic-based sheets (ACF and AOS), and advanced systems (TSS and FDP) were tested. The specimen size was 20 mm square. Fifteen samples were tested for each material. The sheet film thickness with coated layers was as follows: BAP, 62 μm; BET, 46μm; SFA, 133 μm; ACF, 23 μm; AOS, 14 μm; TSS, 134 μm; and FDP, 82μm. Ductility (standard deviation) was as follows: BAP, 2.10 (0.006)%; BET, 2.14 (0.008)%; SFA, 5.19 (0.57)%; ACF, 8.68 (0.05)%; AOS, 5.61 (0.05)%; TSS, 16.26 (0.41)%; and FDP, 6.37 (0.09)%. One-way ANOVA analysis indicated that (1) there in no statistical difference between BAP and BET (p > 0.001), (2) there is a statistical difference (p < 0.001) among all the rest of the tested occlusal sheets, and (3) bulge ductility appears to be linearly related to film thickness, its correlation depending upon types of base materials. Show more

Keywords: Occlusal films/papers, elongation, bulge ductility, occlusal contacts, film thickness

DOI: 10.3233/BME-1997-7405

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 265-270, 1997

Authors: Kim, Kyo-Han | Choi, Man-Young | Kishi, Teruo

Article Type: Research Article

Abstract: The fracture behavior of cast two types of pure Ti and Ti-6A1-4V alloy was understood by acoustic emission (AE) analysis during a fracture toughness test. Specimens for test were cast by the lost wax method using a specially designed Ti casting machine of pressure-different method for dental use. A fatigue crack was inserted from the machined notch tip into the body of a specimen in the range of 0.45–0.55 a/W. Acoustic emission signals released during the fracture toughness test were detected by two sensors attached to both ends of the specimen. Then the signals were recorded and analysed by the …PAC 3000/3104 system. From the early stage of the fracture toughness test, AE signals started to be released in all types of specimens tested. A reaction layer with the investment materials of about 50–100 μm was thought to be the result of the AE release from an early stage of the fracture toughness test. A microfracture behavior of the cast pure Ti and Ti alloys was proposed based on the results obtained from the AE releasing pattern and fracture surface findings. Show more

Keywords: Pure Ti, Ti-6A1-4V alloy, fracture toughness, acoustic emission (AE)

DOI: 10.3233/BME-1997-7406

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 271-276, 1997

Authors: Duda, Georg N. | Elias, John J. | Valdevit, Antonio | Chao, Edmund Y.S.

Article Type: Research Article

Abstract: Mechanical testing has been performed to characterize the locking strength of Morse taper locks used for reconstruction of large bone defects. Taper joint pairs were locked with a series of compressive loads increasing from 500 to 3500 N. Following each load application the taper locks were distracted with either an axial load or a torsional load. Additional tapers were loaded with 2 million cycles of axial compression or 2 million cycles of cantilever bending combined with axial compression, followed by axial distraction. The torsional and axial distraction loads increased linearly with the compressive load. Compared to a single compressive load …application, cyclic axial loading had little influence on the joint strength, while a combination of axial loading and bending increased the joint strength. Based on these results, in vivo loading should increase the locking strength of Morse taper locks used for bone defect reconstruction. Show more

Keywords: Taper lock, segmental prosthesis, mechanical testing, joint strength, bone defect

DOI: 10.3233/BME-1997-7407

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 4, pp. 277-284, 1997