Time dependent flow of biolubricant and suspended particles behavior within total hip replacement

• Main Author: Safari, Alaleh
• Other Authors: Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Ginebra Molins, Maria Pau, Emami, Nazanin, Cervantes, Michel José
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universitat Politècnica de Catalunya 2017
• Subjects: Àrees temàtiques de la UPC::Enginyeria dels materials; Luleå
• Online Access: http://hdl.handle.net/2117/107958; http://hdl.handle.net/10803/405947; https://doi.org/10.5821/dissertation-2117-107958

Cotutela Universitat Politècnica de Catalunya i Luleå University of Technology http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-61756 Total hip replacement (THR) has been one of the most successful surgeries in the 21st century. Ultra-high-molecular-weight-polyethylene (UHMWPE) shows favorable mechanical and tribological properties when used as a bearing surface material in THR. However, produced UHMWPE wear particles challenge increasing the THR lifetimes. Bone loss (osteolysis) initiated by these wear particles is a major cause of total joint arthroplasty failure in both hip and knee prosthesis. In addition to improving the wear resistance of bearing surfaces to reduce wear, wear debris distribution mechanisms within the joint gap must also be thoroughly investigated. These particles distribute within lubricant and across the implant gap. Synovial fluid (SF) lubricates natural joints which is a viscoelastic non-Newtonian shear thinning fluid. The non-Newtonian behavior of SF is attributed to its hyaluronic acid (HA) content which is a linear biopolymer. The distribution patterns of wear particles within total joint replacement are affected by the special rheological behaviors of the SF, geometrical parameters, particle size and shape distribution and particle-fluid interactions. Therefore, understanding wear particles distribution pattern is pivotal to understand the mechanism and eventually minimizing third-body wear of the UHMWPE acetabular liner in THR. According to fluid mechanics forces, the size and density of wear particles suggests that wear particles follow lubricant movements. However, over a matter of hours, such particles show specific behaviors within viscoelastic fluid (not visible in Newtonian fluid) such as particle migration and string formation along the flow direction. The main aim of this project was to develop and validate an experimental method for assessing characteristics of HA and artificial SF solutions and behaviors of wear particles in a viscoelastic fluid flow. The effects of ...