Loading...

Design and Manufacturing of Gradient Cellular Tibial Stem for Total Knee Replacement

Taheri, Atiyeh | 2022

229 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55303 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Farahmand, Farzam; Bahrami Nasab, Marjan
  7. Abstract:
  8. Loosening of uncemented tibial component is one the most common causes of total knee prosthesis failure which is a result of short-term factors such as instability and incomplete osseointegration as well as long-term factors such as peri-prosthetic stress shielding and bone atrophy. Porous cellular structures for tibial stem have been considered as a solution to this problem. This project is aimed to achieve an optimal gradient porous cellular design of tibial stem that in addition to sufficient mechanical strength, provides a perfect osseointegration and prevents bone resorption by incorporating appropriate porosity size, small micro-motion and favorable stress distribution on bone. A finite element model of bone and tibial component was developed in which the bone and the prosthesis were modeled as non-homogenous (based on Hounsfield values from CT image) and homogenous elastic materials, respectively. At first, while assuming frictional contact, the model was utilized to predict nodal micro-motion at the bone-implant interface. Then, by assuming a perfectly bonded connection at the interface, bone stress distribution was compared with an intact sample to identify most vulnerable elements to remodeling. Results were compared and validated with previously published data. Then, a non-homogenous material was assigned to prosthesis and by minimizing the interface micro-motion and bone resorption though a DOE optimization procedure, an exponential relation (as a function of axial and radial coordinates) was extracted for elastic modulus distribution. At the end, a reversed homogenization relation was used to acquire the optimal porosity distribution in the component. An equivalent cellular gradient structure composed of unit gyroid cells was designed and constructed. Results indicated that compared to dense prosthesis, gradient tibial stem does not contribute much to the number of nodes susceptible for osseointegration but, reduces the bone resorption and remodeling by 11%
  9. Keywords:
  10. Osseointegration ; Micromotion ; Knee Prosthesis ; Knee Joint ; Total Knee Replacement (TKR) ; Unit Gyroid Cells ; Stress Shielding ; Structure Cellular Gradient

 Digital Object List

 Bookmark

No TOC