Modifying and Expanding the Simulation of Wear in the Spherical Joint With a Polymeric Component of the Total Hip Prosthesis

Abstract

Abstract. The existing model of wear, based on the classical

Simulation of Wear in a Spherical Joint With a Polymeric Component of the Total Hip Replacement Considering Activities of Daily Living

“…[27,28], contains a solid femoral ball head of cobalt-chromium alloy or ceramics (alumina or zirconia) with widely used standard diameters of 32 mm employed against a soft (UHMWPE) acetabular cup. The radial clearance between them is of 0.15 mm.…”

“…where σ(θ,φ,t i ) is a normal contact pressure between the counter-face surfaces at the same point of time instant t i of the gait cycle; ΔS(θ,φ,t i ) is an increment of the arc sliding [27,28] distance between the adjacent measuring points under the same conditions; k w is a wear factor which depends on the material, nature of the surface and, as was found, the nominal contact pressure. A modified formula for determining the depth of wear is presented in [28], considering the change in the wear factor as a function of the contact pressure.…”

“…A modified formula for determining the depth of wear is presented in [28], considering the change in the wear factor as a function of the contact pressure.…”

“…Kinematic waveforms of the angular displacements of the femoral joint component are used to determine the increment of arc sliding distance ΔS(θ,φ,t i ), and in determining normal contact pressure σ(θ,φ,t i ) by solving the contact problem, the change in magnitude of the applied force vector during the step cycle is taken into account. The calculation algorithm is presented in detail in [27,28], where the parameters of wear are studied during the level walking in two versions: according to the demands of ISO 14242-1, as well as for profiles of angular femoral positions, measured by Jonhston and Smidt, and for patterns of the applied force, measured by Paul [31]. In fact, the patient, in addition to level walking, daily performs other motor actions, the consideration of which allows determining the wear parameters closer to the real ones.…”

“…The first one is that all ADL listed above are lined up in a predetermined order with a preset duration of motor task for the one simulation cycle: 44% -level walking, 24% -stair ascending-stair descending, 12% -chair sitting, 12% -chair rising, and 8% -deep squatting. In order to follow the approximate number of gait steps at which the correction of the supporting surface of the cup geometry is performed by moving the nodes to the value of the obtained linear wear [28], their minimal number of 500,000 is taken.…”