Strain Analysis in Cementless Hip Femoral Prosthesis using the Finite Element Method - Influence of the Variability of the Angular Positioning of the Implant.

Objective  The present study aims to evaluate the influence of different positioning of the hip femoral prosthesis on the stress and strain over this implant. Methods  A femoral prosthesis (Taper - Víncula, Rio Claro, SP, Brazil) was submitted to a stress and strain analysis using the finite element method (FEM) according to the International Organization for Standardization (ISO) 7206-6 Implants for surgery - Partial and total hip joint prostheses - Part 6: Endurance properties testing and performance requirements of neck region of stemmed femoral components standard. The analysis proposed a branch of the physical test with a +/- 5° angle variation on the standard proposed for α and β variables. Results  The isolated +/- 5° variation on the α angle, as well as the association of +/- 5° variation on the α and β angles, presented significant statistical differences compared with the control strain ( p  = 0.027 and 0.021, respectively). Variation on angle β alone did not result in a significant change in the strain of the prosthesis ( p  = 0.128). The stem positioning with greatest implant strain was α = 5° and β = 14° ( p  = 0.032). Conclusion  A variation on the positioning of the prosthetic femoral stem by +/- 5° in the coronal plane and/or the association of a +/- 5° angle in coronal and sagittal planes significantly influenced implant strain.