Abstract
Finite element stress analysis has been applied to examine the stress patterns in a prosthesis requiring fixation in the medullary shaft of a long bone. No specific prosthesis is considered but rather a generally applicable geometry has been chosen. This consists of a cylindrical section of cortical bone within which is implanted a prosthesis composed of a solid central rod surrounded by a porous coating. The finite element analysis utilized an axisymmetric model to determine the distribution of stresses throughout the system. The effect of changes in length of prosthesis, thickness of porous coating, depth and type of tissue ingrowth, and type of porous coating material were studied under conditions of axisymmetric loading. The results indicate that with complete bone ingrowth, the maximum shear stress and the distance necessary for load transfer are both independent of implant length. However, with incomplete ingrowth, increasing implant length reduces shear. Incomplete growth also produces lower shear stresses but higher shear strains in areas without ingrowth. In addition, a porous polyethylene coating gives a more even load transfer and lower shear than a porous coating of a high modulus material.
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Anand, S.C., John, K.R.S., Moyle, D.D. et al. Stress distribution in porous surfaced medullary implants. Ann Biomed Eng 5, 410–420 (1977). https://doi.org/10.1007/BF02367319
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DOI: https://doi.org/10.1007/BF02367319