Optimization of distribution of porosity of a short metaphyseal femoral stem with respect to the strain field and the micromotion
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Date
2024-12-19
Authors
Σώλου, Κωνσταντίνα
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Abstract
Introduction: Short-stem total hip arthroplasty is a treatment method for hip osteoarthritis, but long-term complications such as stress shielding and aseptic loosening can lead to hardware failure. Stems with increased porosity toward the distal end were discovered to be effective at reducing stress shielding; however, there is a lack of research on customized porous distributions in stem coatings. This study aimed to optimize the porous distribution of the coat of a metaphyseal femoral stem, aiming to reduce stress shielding in the proximal area.
Materials and Methods: A finite element analysis model of an implanted, titanium alloy short-tapered wedge stem featuring a porous coating made of titanium was designed to simulate a static structural analysis of the femoral stem's behavior under axial loading in Analysis System Mechanical Software, with the coefficients of friction in nine areas of the coat as variables and providing information on the strain distribution. For computational feasibility, 500 combinations of coefficients of friction were randomly sampled.
Results: The 17 models achieved increased strains in the proximal medial areas (M1, M2) and in the proximal lateral area (L1) and decreased strains in the distal medial and lateral areas (M5, M6, M7, L4, L6 and L7). An increased coefficient of friction was observed for the lateral porous coating and proximal medial porous coating. The coefficients of friction in the distal lateral porous coating (O4 and O5) strongly influenced the mid-distal medial femoral area (M3, M4 and M5), the proximal and mid-lateral femoral areas (L1, L2 and L3) and the distal lateral femoral area (L5). An increase in the coefficients of friction in the proximal lateral porous coating (O2) and in the distal lateral porous coating (O5) and a decrease in the coefficients of friction in the mid-distal porous coatings (O4, I3 and I4) resulted in increased strains proximally and decreased strains distally.
Conclusions: We found that increased coefficients of friction in proximal and distal lateral porous coatings and decreased coefficients of friction in mid-distal porous coatings could result in strains biomechanically closer to intact bone. A customized porous distribution could reduce stress shielding in short femoral stems.
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Keywords
Orthopedics, Hip arthroplasty, Femoral prosthesis, Metaphyseal prosthesis, Biomechanical study, Stress shielding effect, Finite element analysis