Improving stress shielding following total hip arthroplasty by using a femoral stem made of β type Ti-33.6Nb-4Sn with a Young's modulus gradation

Go Yamako*, Dennis Janssen, Shuji Hanada, Thomas Anijs, Kiyohide Ochiai, Koji Totoribe, Etsuo Chosa, Nico Verdonschot

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    11 Citations (Scopus)

    Abstract

    Stress shielding-related bone loss occurs after total hip arthroplasty because the stiffness of metallic implants differs from that of the host femur. Although reducing stem stiffness can ameliorate the bone resorption, it increases stress at the bone–implant interface and can inhibit fixation. To overcome this complication, a novel cementless stem with a gradient in Young's modulus was developed using Ti-33.6Nb-4Sn (TNS) alloy. Local heat treatment applied at the neck region for increasing its strength resulted in a gradual decrease in Young's modulus from the proximal to the distal end, from 82.1 to 51.0 GPa as calculated by a heat transfer simulation. The Young's modulus gradient did not induce the excessive interface stress which may cause the surface debonding. The main purpose of this study was to evaluate bone remodeling with the TNS stem using a strain-adaptive bone remodeling simulation based on finite element analysis. Our predictions showed that, for the TNS stem, bone reduction in the calcar region (Gruen zone 7) would be 13.6% at 2 years, 29.0% at 5 years, and 45.8% at 10 years postoperatively. At 10 years, the bone mineral density for the TNS stem would be 42.6% higher than that for the similar Ti-6Al-4V alloy stem. The stress–strength ratio would be lower for the TNS stem than for the Ti-6Al-4V stem. These results suggest that although proximal bone loss cannot be eliminated completely, the TNS stem with a Young's modulus gradient may have bone-preserving effects and sufficient stem strength, without the excessive interface stress.

    Original languageEnglish
    Pages (from-to)135-143
    Number of pages9
    JournalJournal of biomechanics
    Volume63
    DOIs
    Publication statusPublished - 3 Oct 2017

    Keywords

    • Bone remodeling
    • Finite element analysis
    • Low modulus stem
    • Stress shielding
    • Total hip arthroplasty

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