ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

Reconstruction of a human ligamentous lumbar spine using CT images — A three-dimensional finite element mesh generation (1991)

Breau, C. ; Shirazi-Adl, A. ; Guise, J.

Springer

Annals of biomedical engineering 19 (1991), S. 291-302

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ISSN: 1573-9686

Keywords: Lumbar spine ; Geometry ; Finite element mesh ; CT scanner ; Reconstruction

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: Abstract Detailed investigation on biomechanics of a complex structure such as the human lumbar spine requires the use of advanced computer techniques for both the geometric reconstruction and the stress analysis. In this study, an automated scheme is developed to generate the required three-dimensional finite element grid of a human ligamentous lumbar spine. The computer-based medical images (CT-scans) of a cadaveric lumbar spine are used to automatically reconstruct the geometry and the grid of the tissues. The data are then transferred to a mainframe computer in a format suitable for an existing nonlinear finite element code. The process has been designed to allow for a number of user-defined parameters such as the number of elements representing the intervertebral discs and the degree of smoothing of the facet articulating surfaces. This finite element mesh can be used for a detailed stress analysis of the human lumbar spine to understand its mechanical function in both normal and perturbed states. The developed interactive system is also helpful from a diagnostic point of view.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00000004

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2

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A parametric axisymmetric model study on the interface motions in porous-surfaced tibial implants (1989)

Shirazi-Adl, A. ; Ahmed, A. M.

Springer

Annals of biomedical engineering 17 (1989), S. 411-421

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ISSN: 1573-9686

Keywords: Axisymmetric finite element ; Interface motion ; Porous tibial implant

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine , Technology

Notes: Abstract The effects of a number of variables on the interface relative motions in poroussurfaced tibial implants are investigated using a simplified axisymmetric finite element model. The parameters considered are contact or link spacing, height of the central metal stem, presence of a circumferential metal flange, presence of a UHMWP articular plate resting freely on or fixed to the metal base, resting of the prosthesis edge on the cortical shell, and type of the metal alloy. In order to represent the immediate post-surgical situation with no bone ingrowth, the interface between the bone and porous-surfaced metal is modelled by frictionless rigid links oriented normal to the interface. Cases are also studied in which the horizontal interface is assumed to be fixed while the vertical interface remains frictionless. The magnitudes of the interface motion are negligibly affected by the variation in the link spacing from 0.3 mm to about 3.0 mm. The interface relative motion is predicted to decrease in cases with a shorter central metal stem, with the addition of a circumferential metal flange, with the use of more rigid prosthesis, and with the addition of a UHMWP articular plate.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02368059

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3

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Effect of a cement-bone composite layer and prosthesis geometry on stresses in a prosthetically resurfaced tibia (1982)

Shrivastava, S. C. ; Ahmed, A. M. ; Shirazi-Adl, A. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 16 (1982), S. 929-949

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: A comparative study of stress distributions in the component materials of a number of models of a prosthetically resurfaced tibia is presented. Although the geometry is idealized to be axisymmetric, the loadings for which the finite element analyses are performed are considered to be nonaxisymmetric, simulating more realistically the loading conditions in vivo. The different models are chosen with the view of determining the influence of changes in the prosthesis design on the induced stress distribution in the component materials. The changes considered are in the thickness of the cement and the cement-bone composite layers, and in the shape of the prosthesis. Experimentally measured values of strains are compared with the analytically predicted values to check the validity of the assumptions used in the finite element modeling. The comparison of induced stresses in the different materials reveals the desirability, from a mechanical behavior point of view, of introducing a cement-bone composite layer and using a prosthesis with domed subsurface in the fixation system. It is shown that for a model incorporating these features, considerable reduction of stresses in the cement, in its bulk and at its interface with the prosthesis plate, is achieved. The reduced stresses can be expected to have beneficial effects on the long-term behavior of the cement and its interfaces in the fixation system.

Additional Material: 15 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820160616

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4

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Friction properties of the interface between porous-surfaced metals and tibial cancellous bone (1990)

Rancourt, D. ; Shirazi-Adl, A. ; Drouin, G. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 24 (1990), S. 1503-1519

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: Friction tests between cancellous bone cubes and porous-surfaced metal plates were conducted in order to determine the mechanical properties of the interface in a knee porous-surfaced metal implant. Bone specimens were obtained from fresh frozen amputated tibiae and three metal plates were chosen: titanium bead porous-surfaced, titanium fiber mesh porous-surfaced, and smooth stainless steel. Results show that the friction curve is highly nonlinear. Friction coefficients measured vary between 0.3 and 1.3. The friction coefficient of the interface is independent of the excision site of the bone cubes and of the magnitude of the rate of relative displacement at the interface. The friction coefficient appears to vary slightly with the normal contact pressure for all the metal surface. Both porous surfaces have statistically a higher friction coefficient than the smooth surface. This is likely due to the presence of surface asperities whereby the metal ploughs the bone surface. However, no significant difference is observed between bead and fiber mesh types.

Additional Material: 11 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820241107

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5

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Bidirectional friction study of cancellous bone-porous coated metal interface (1996)

Hashemi, A. ; Shirazi-Adl, A. ; Dammak, M.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 33 (1996), S. 257-267

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: Bidirectional friction tests between cancellous bone cubes and a porous-coated metal plate were performed to determine the mechanical properties of the interface required in 3-dimensional (3-D) finite element model studies of cementless implants. Bone specimens were obtained from different proximal regions of four resurfaced cadaveric tibiae. A beaded porous-surfaced plate similar to those used in implants was used. Tangential loads in perpendicular directions with different magnitudes were applied at the interface in the presence of constant normal pressure, and the displacements were monitored in the same directions. Measured results showed that the interface load-displacement curve is highly nonlinear with significant coupling between two perpendicular directions. The interface friction coefficient (defined as the ratio of the maximum resultant tangential force divided by the normal load) was found to remain nearly unchanged with the relative magnitude of tangential stresses and the bone location. Moreover, bidirectional tests suggested that the load-displacement relation when evaluated for resultant values is similar to that obtained in a unidirectional testing condition. Constitutive equations that account for the cross-stiffness coupling terms between perpendicular directions were also developed. These relations were used in a 3-D finite element model study of preceding bidirectional friction tests. The influence of the coupling terms on results was investigated by comparison of predictions with measurement results. A satisfactory agreement was found between the results of the experiments with those of finite element studies confirming the constitutive relations as well as the importance of coupling terms. © 1996 John Wiley & Sons, Inc.

Additional Material: 10 Ill.

Type of Medium: Electronic Resource

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6

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Friction properties at the bone-metal interface: Comparison of four different porous metal surfaces (1997)

Dammak, M. ; Shirazi-Adl, A. ; Schwartz, M. ; [et al.]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 35 (1997), S. 329-336

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: Detailed friction load-displacement response of four distinct metallic surfaces [one beaded porous metal (CTR) and three cast Co-Cr alloy ingrowth mesh surfaces, nonplanar mesh (INX), cast mesh 1 (CM1), and cash mesh 2 (CM2)] on polyurethane and cancellous bone specimens of six tibiae were measured under different normal stresses (0.1, 0.15, or 0.025 MPa). Bone cubes were obtained from different proximal regions of resurfaced cadaveric tibiae. Both monotonic and cyclic fatigue loadings of up to 4000 cycles at 1 Hz were considered. Comparison of measured results indicated that the friction coefficient was not affected by the magnitude of normal stress and the bone excision site (medial, lateral, anterior, posterior, and central). The CM2 surface showed significantly greater resistance with friction coefficients of more than 0.9 for the bone and 0.8 for the polyurethane. The INX surface yielded the second largest resistance followed by CMI and CTR surfaces. No significant difference was found between these latter two surfaces. Fatigue tests up to 4000 loading-unloading cycles showed about 10% reduction in friction coefficient for CTR and INX surfaces, while negligible reduction was found for CM1 and CM2 surfaces. © 1997 John Wiley & Sons, Inc.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

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7

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Experimental determination of friction characteristics at the trabecular bone/porous-coated metal interface in cementless implants (1993)

Shirazi-Adl, A. ; Dammak, M. ; Paiement, G.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 27 (1993), S. 167-175

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ISSN: 0021-9304

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine , Technology

Notes: An apparatus was developed to measure loaddisplacement friction properties at the cancellous bone/porous-coated metal plate interface. Bone cubes were obtained from different proximal regions of four resurfaced cadaveric tibiae. Three different poroussurfaced metal plates (one fiber mesh and two bead) and a smooth-surfaced metal plate were used. In the presence of a constant normal contact pressure (0.10, 0.15, or 0.25 MPa), a variable tangential load up to the maximum resistance of the interface was applied and both relative normal and tangential displacements were recorded. Repetitive and fatigue loadings were also considered. Measured results show that the interface friction curve is highly nonlinear, exhibiting large relative tangential displacements in the range of 50-400 μm before the maximum load is reached. Relative displacements in the normal direction remain below 10 μm. The maximum resistance in friction is independent of the bone excision site, type of porous-surfaced metal plate, magnitude of normal load, placement of bone cubes on metal plates or vice versa, repetition of applied load, and conservation period of bone cubes in saline solution. The smoothsurfaced metal plate has significantly smaller friction resistance than porous-coated ones. The fatigue loading of up to 4000 cycles at 1 Hz, in the presence of 0.25 MPa contact pressure, slightly decrease the interface friction coefficient. Finally, the initial secant stiffness of the interface at 75% of the maximum resistance load is found to be larger for the bone cubes from the lateral and medial regions and for the metal plate with smooth surface. © 1993 John Wiley & Sons, Inc.

Additional Material: 7 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/jbm.820270205

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