Influence of the Lattice Structures on the Mechanical Behavior of Hip Endoprostheses

Rapid Prototyping technologies allow fabrication of lattice structures made of biocompatible materials. The natural stress distribution in the femur is altered after total hip arthroplasty (THA) because the hip end prosthesis will assume a part of the load causing a reduction of stresses in some regions of the bone. This phenomenon is known as stress shielding and it results in a loss of bone mass. The bone will become less dense and weaker and the endprosthesis can become loosening. This study explores the assumption that insertion of a certain lattice structure into the hip endoprosthesis stem will lead to a more flexible endoprosthesis, but strong enough to support the natural hip joint forces. A more flexible end prosthesis will stimulate the bone to a correct remodeling. This structure can also offer a better osteointegration than the existing end prostheses. The presented study considers five different types of lattice structures that are inserted into a large area of the implant stem. There was analyzed both the possibility of using one type of lattice structure and a combination of two different types. The paper also presents some design aspects of the lattice structures and results of the numerical analyses performed in order to evaluate the mechanical behavior of the proposed end prostheses. The comparison of the results obtained by Finite Element Analysis (FEA) highlights the influence of the lattice structures type on the mechanical behavior of hip end prostheses.