Translational Center on Biomaterials for Orthopedic and Dental applications

Manufacturing of patient-specific Zirconia toughened Alumina based femoral ball head prototype development

Principal Investigator

Debasish Sarkar
Ceramic Engineering,
National Institute of technology, Rourkela
Email: dsarkar@nitrkl.ac.in
Website

Co-Principal Investigator

Bikramjit Basu, PhD FNAE FNASc FWAST FBAO
Materials Research Centre,
Indian Institute of Science, Bangalore
Email: bikram@mrc.iisc.ernet.in
Website

Co-Investigators

D. C. Sundaresh
M S Ramaiah University of Applied Sciences, Bangalore
Email:
Website
Aroop Kumar Dutta
Excel Matrix Biological Devices Pvt. Ltd., Hyderabad
Email:
Website

Objectives of the Project

The primary objective of the proposed project is to develop a ZTA femoral ball head with high dimensional stability and mirror surface finish from commercially available high purity alumina and zirconia nanopowders, and their detailed invitro and invivo biocompatibility from the clinical perspective.

To optimize the zirconia weight percentage from resultant relative density and grain size of alumina matrix and zirconia particulates.
In the beginning, the green discs (Ø ~ 12 – 25mm) specimens will be prepared with variation of 0 – 20wt% zirconia content and sintered atdifferent sintering schedules to optimize the composition and sintering profile and also to obtain the high density, small grain size, high hardness and high compressive strength. Green ceramic components are subjected to shrinkage during sintering and hence volume shrinkage has to be measured for designing and fabrication of the mold. Response surface method will be utilized to optimize the composition of four variables (zirconia content, MgO, Temperature, time) and five levels. The optimal composition and sintering profile along with shrinkage phenomena and mechanical response as obtained from sintered discs would be utilized to fabricate the proposed femoral head.

To design and fabricate uniaxial compaction of truncated femoral head from commercially available high purity nanopowders and finalize their sintering module.
Four part molds including different accessories will be machined and assembled for both compaction and ejection of green specimens after uniaxial pressing at prerequisite load and dwell time. The depth of the plunger movement is needed to synchronize for the transmission of maximum load and their blind hole depth. Both alumina and zirconia nanoparticles will be mixed in the presence of polyvinyl alcohol (PVA), an organic binder in high-density polyethylene jar and alumina ball. The obtained powders will be dried in hot air oven at 70oC for 2hr. The free flowing powder will be poured into steel mold and uniaxially pressed to produce green truncated femoral ball head compact. The engineering design of the mold is an important step. The green compact will be pre-sintered at predetermined sintering profile to achieve enough strength for machining.

To prepare dimension stable polished femoral head
Pre-sintered total hip replacement (THR) will be machined by computer numerical control (CNC) to achieve dimension stable component. Following that the component will be sintered in chamber furnace at predetermined temperature. Polishing will be conducted to develop a high degree of roundness and mirror finish. This will help in reducing the surface asperities contact in between acetabulum cup during relative motion, and hence formation of resultant debris.

To estimate the mechanical properties including invitro tribological behavior of developed mirror polished femoral head by HIP simulator.
Different physical properties, specifically the relative density, apparent porosity and grain size distribution will be studied to explain the different mechanical properties like hardness, fracture toughness and compressive strength. The invitro tribological study will be carried out on the polished surface against highly cross-linked UHMWPE.

To study the details invitro-invivo biological study in the perspective of clinical application.
As part of the biocompatibility assessment the in vitro cytocompatibility study will be conducted by growing osteoblast cells on ZTA substrate for varying period of upto 7 days. Both the cell viability and cell morphological changes will be investigated. The optimized composition will be further implanted into femoral defects in rabbit animal model. In rabbit animal model, an osseointegration will be quantified using micro CT analysis. After the hip simulator study at CGCRI with femoral ball head against UHMWPE socket for upto 5 million cycles, the cytotoxicity of the wear debris particle will also be analyzed using bone cells.