Numerical investigations of stress shielding in total hip prostheses

Abstract

Aseptic loosening of the prosthesis is still a problem in artificial joint implants. The loosening can be caused by, among other factors, resorption of the bone surrounding the prosthesis owing to stress shielding. In order to find out the influence of the prosthesis type on post-operative stress shielding, a static finite element analysis of a femur provided with the conventional uncemented stem BICONTACT and of one with the femoral neck prosthesis SPIRON was carried out. Strain energy densities and maximal principal strain distributions were calculated and compared with the physiological situation. Here, stress shielding was demonstrated in both periprosthetic femora. To determine the areas of the stress shielding, the bone in each FE model was subdivided into three regions of interest (ROI): proximal, diaphyseal, and distal. The numerical computations show stress shielding in the proximal ROI of both periprosthetic femora. Diaphyseally, the femoral neck prosthesis SPIRON, in contrast to the conventional uncemented long-stem prosthesis BICONTACT, causes no decrease in the strain distribution and thus no stress shielding. Distally, no change in the load distribution of either periprosthetic femur could be found, compared with the physiological situation.

Comparison between simulation results and DEXA investigation of the bone remodelling after implanting a cementless long stem hip prosthesis

“…In general, it can be stated that the numerical model used in [5,6,7] is able to anticipate the bone remodelling with an acceptable deviation.…”

“…1 (a)) in order to achieve an accurate measuring of the BMD and its changings during the study period [4]. The FE-model of the periprosthetic femur used at IFUM in [5,6,7] is used in this comparison applying the same conditions and constraints with the same muscle forces and hip contacts but with the following restrictions:…”

Life Estimation of Hip Joint Prosthesis

“…This number has steadily increased over the past 20 years, and is expected to continue to increase over the next several decades [2]. Failures of hip prosthesis have been reported due to fatigue failure of hip joint stem [3,4], fracture of bone cement [5] and wear caused by sliding present between head and socket [6,7]. In other words fatigue fracture and wear are the basic mechanisms associated with failure of hip prosthesis [8].…”

“…This method is widely used as a time saving and cost efficient computing method in biomedical engineering [4]. In the present research, a prosthesis [9] has been modeled as an assembly of monoblock acetabular cup and monoblock femur (femoral head ?…”

Fatigue design of a mechanically biocompatible lattice for a proof-of-concept femoral stem

“…The advantage of controlling the microarchitecture is twofold. First, the overall implant can be designed to be more compliant, which reduces stress shielding and bone resorption (Behrens et al, 2008;Glassman et al, 2006;Huiskes et al, 1992;Pettersen et al, 2009). …”