Numerical modeling by finite element method offers valuable information and details on the mechanical behavior of the prosthesis in terms of stress and strain distribution, load transfer, stress intensity factors, etc. An explicit analysis conducted on the behavior of microcavity and cracking in PMMA surgical cement (polymethyl methacrylate) used for a total hip prosthesis (THP) is of great importance in collecting information about the nature of the loosening phenomenon of the cement application. The rupture of orthopedic cement is practically the main cause of this loosening. Understanding the different failure mechanisms provides a significant advance in the cemented total prostheses. To do this, a numerical analysis by 3D finite element method (FEM) model of the total hip prosthesis was carried out in order to evaluate the stress levels in the different components. We focused on the effect of the microcavity rotation and the semi-elliptical crack position on the stress distribution in THP elements and on the orthopedic cement, which represents the weakest link of the prosthesis. We concluded that the two mechanical defects (Microcavity, semi-elliptical crack) exhibit more intense stresses in the THP components and record a very intense stress level and stress intensity factor KI. These mechanical defects causing damage to the PMMA around the tip of the bone debris increase the loosening state of the total hip prosthesis.