STP953

    Effect of Press Fit on Lateral Stem Stresses and the Integrity of Porous-Coated Femoral Prostheses: An In Vitro Strain Gage Study

    Published: Jan 1987


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    Abstract

    A strain gage analysis was performed to determine the stresses generated on the lateral surface of two types of porous-coated femoral prostheses. One type of prosthesis was made of wrought titanium (Ti-6Al-4V) alloy with a porous polysulfone coating; the other was a porous-coated alloy meeting the requirements of the ASTM Specification for Cast Cobalt-Chromium-Molybdenum Alloy for Surgical Implant Applications (F 75–82). Various degrees of fit were evaluated, ranging from a loose fit to one in which the stem was cemented into the femoral canal. The results showed that modeling pressfit porous-coated stems using cemented conditions can produce peak stresses on the lateral surface of the stem significantly lower than those for noncemented stems. Based on the fatigue strength of the stem material, the authors show that assessing stem integrity with the assumption that the cemented stem represents a complete bone ingrowth condition may lead to a design evaluation of the femoral stem that is overoptimistic for in vivo fatigue load conditions.

    Keywords:

    porous implants, porous-coated femoral prostheses, femoral stem stresses, fatigue integrity, press fit, titanium alloy, cobalt F 75 alloy


    Author Information:

    Davidson, JA
    Materials research director, research engineer, and engineering manager of reconstructive products, Richards Medical Co., MemphisTN,

    Bushelow, M
    Research engineer, Howmedica Corp., Rutherford, NJ

    Gavens, AJ
    Materials research director, research engineer, and engineering manager of reconstructive products, Richards Medical Co., MemphisTN,

    DeMane, MF
    Materials research director, research engineer, and engineering manager of reconstructive products, Richards Medical Co., MemphisTN,


    Paper ID: STP25238S

    Committee/Subcommittee: F04.93

    DOI: 10.1520/STP25238S


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