Initial fixation of a finite element model of an AI-Hip cementless stem evaluated by micromotion and stress.
BACKGROUND
This study investigated issues related to initial stability after stem fixation. Finite element models of the AI-Hip cementless stem were constructed for computer simulation.


METHODS
Analysis was performed after implantation of two types of cementless hip stem for clinical use; and micromotion and stress were then calculated. Boundary and initial conditions were (1) rigid contact of the distal end of the model femur with a rigid base; (2) a stepping load of 1800 N was applied to the proximal top of the stem; (3) a load of 1440 N was pulled from the greater trochanter of the femur as muscle force; (4) a torsion load of 18.9 Nm was applied to the proximal femur as the intrarotation.


RESULTS
Relative micromotion of the AI-Hip cementless stem showed a value as low as that of a conventional stem. The calculated von Mises stress was below the level that would cause destruction of the femur and stem.


CONCLUSIONS
Based on the relative micromotion and von Mises stress level, the AI-Hip cementless stem showed initial stability. The present experimental results should be compared with those obtained in clinical practice.
Department of Biomedical Engineering, School of Allied Health Science, Kitasato University, Sagamihara, Kanagawa, Japan.
Rina
R
Sakai
Yusuke
Y
Sato
Moritoshi
M
Itoman
Kiyoshi
K
Mabuchi
D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D006622:Hip Prosthesis; D006801:Humans; D007593:Joint Instability; D013314:Stress, Mechanical