Application of Electronic Speckle Pattern Interferometry for Evaluation of the Static Stiffness of a Complex Orthopedic Implant

Abstract

The paper presents a comparative analysis of the results of experimental and numerical evaluation of static stiffness of extendable tumor knee joint prosthesis for children. Electronic speckle pattern interferometry and finite element method were used for experimental and computational research, respectively. The procedure of experimental tests shows that the stiffness of the joint prosthesis can be determined experimentally by means of electronic speckle pattern interferometry, but the quantitative result of such a procedure cannot be captured directly in a finite element method model. The values of static stiffness calculated numerically do not fall within the range of experimental results. The discrepancy grows as the extension of the endoprosthesis increases and the value of relative difference between numerical and experimental results reaches the value of 54%. The inconsistency of results can be explained by the involvement of the joint linking the body of the implant to the moving part. While effective in the case of traditional, one-piece constructions, finite element method modeling does not yield satisfactory results in the case of such an elementary parameter as is the static stiffness of the implant, due to the difficulty in estimating the stiffness of the joint present in the sliding node. The use of the experimental method makes it possible to estimate the degree of this inconsistency.

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