Femoral hip stem prosthesis made of graded elastic modulus metastable β Ti Alloy

Abstract Ti alloys are frequently used in the manufacture of femoral stems for total hip arthroplasty. Although low elastic modulus stems minimize bone stress shielding, they also may produce micromotions at the bone/implant interface, leading to excessive interfacial mechanical stress at the proximal region. This phenomenon may lead to the growth of fibrous tissues and, eventually, implant failure. To address both restrictions simultaneously, stems with adjustable rigidity may be used. Considering that the rigidity of β Ti alloys can be controlled by heat treatments, this paper introduces a new concept for a femoral stem with a graded elastic modulus using metastable β Ti alloy. The combination of solution heat treatment, water-quenching, and aging heat treatments allows the mechanical behavior of the metastable β Ti alloys to be tailored and, in particular, be used to construct a graded elastic modulus femoral hip stem. The results obtained revealed that it is feasible to design biomedical implants from metastable β Ti alloys with hybrid mechanical behavior. The specific mechanical behavior is obtained by focusing only on heat treatments. A stem with an elastic modulus varying from 65 GPa to 110 GPa was obtained.