Preclinical analysis of a novel short hip-stem design: A finite element model-based investigation

Abstract

This study proposes a novel uncemented short hip stem, adapted from a long stem design to reduce strain shielding and bone resorption and improve osseointegration. It consists of a central core of Ti alloy with buttresses (inner solid and outer porous) protruding radially outwards. The slots between the buttresses are filled with bone substitute material. The present study investigated the short-stem's mechanical behaviour, focusing on strain shielding and bone remodelling in short and long terms, respectively. The results were compared to those of the solid counterpart with overall same geometry. Computer Tomography (CT) based 3D FE models of an intact and reconstructed femur were used. The models were solved for two static loading cases: normal walking and stair climbing. Strain shielding was observed across all the Gruen Zones with both the stems; however, to a much lesser extent ($\sim 44\%,$on average) with the porous stem. Subsequent bone resorption was also predicted to be of much lesser degree ($\sim 42\%,$on average) with the porous stem. Furthermore, strain concentration in the bone around the porous stem tip was less prominent than the solid stem, indicating lower risk of thigh pain. The porous short stem design offers promising results, both in short and long terms.