Mechanical Aspects of Self-Alignment Mechanism in Hip Bipolar Hemiarthroplasty

Abstract

The paper proposes a mechanical study of the self-centering mechanism of the bipolar prosthesis. This represents the fundamental principle of the bipolar construction, and relays on the offset between the inner and outer center of rotations of the bipolar head. In the paper, the kinematical aspects of the construction were recorded and explained by using five different offset values and keeping constant the femoral head diameter and the acetabular diameter. The simulations were conducted by imposing to the femoral head a linear movement in the vertical direction, similar to a reaction force that occurs when an implanted patient stands up. Two initial conditions were used for each geometric offset: one ideal, no friction and another more realistic by implementing friction coefficients at the sliding interfaces.