Document Type
Thesis
Date of Award
8-31-1991
Degree Name
Master of Science in Mechanical Engineering - (M.S.)
Department
Mechanical and Industrial Engineering
First Advisor
Michael Pappas
Second Advisor
David S. Kristol
Third Advisor
Rong-Yaw Chen
Abstract
A three-dimensional finite element model of a collar-type hip stem and both the cortical and cancellous bones is used to investigate the stress distributions on an implanted femoral stem, adjacent bone, and specifically at the bone/implant interface for various amounts of porous coating and different stem materials. The finite element model consists of 909 nodes comprising 536 linear eight-node solid brick elements and 176 two-node interface elements. The finite element analysis code employed is SUPERTAB from SDRC. The interface elements consist of coincident-node spring elements and gap elements which model the rigidly bonded and loose interfaces respectively. Local coordinate systems are defined at the bone/implant interface to represent interface normal stresses. A nonhomogeneous isotropic distribution of elastic constants is used to account for the varying material properties in the model. Four different loading conditions (4%, 9%, 41% and 52%) of the normal walking cycle are analysed. The hip joint reaction force, abductor muscle force and adductor muscle force are applied to the collar of stem and the greater and lesser trochanters.
The resulting stress distributions indicate that for the fully porous coated inhomogeneous model, the proximal bone region is highly relieved of stresses. The proximally coated model generates more interface compression and higher bone stresses in the proximal region. The laterally coated model exhibits similar stress pattern to that of proximally coated. However, when compared to the proximally coated, the slanted coated model has a higher proximal bone stress and higher interface stress values at the bone/implant interface. Thus, the laterally coated stem is the most effective at loading the proximal femur and reducing the loading bypass mechanism in the region. The effects of cobalt-chromium-molybdenum(CoCrMo) and titanium as the stem materials are also assessed. The titanium stems demonstrate more favorable results than the CoCrMo stems. Therefore, the use of laterally coated titanium stem appears to be the optimal alternative in the total hip replacement system.
Recommended Citation
Yau, Siu-For, "A three-dimensional finite element stress analysis of interface conditions in porous coated hip prosthesis" (1991). Theses. 2681.
https://digitalcommons.njit.edu/theses/2681
