Wear and Friction Properties of PVA/PVP Hydrogels as Synthetic Articular Cartilage

• Main Author: Katta, Jayanth K
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2003
• Subjects: Bioengineering; Biomedical engineering
• ISBN: 9798380401067

An unsolved clinical problem in orthopedics today continues to be the young and middle-aged patients with osteoarthritis and other pathological conditions leading to degeneration of articular cartilage. Total joint replacement is successful, but is associated with significant morbidity, costs, and failure of replacement components due to wear and osteolysis. As an alternative approach, many hydrogels (soft bearing materials) have been proposed as a replacement for articular cartilage. Any joint bearing material including cartilage undergoes wear and it is thus imperative to assess the wear and friction characteristics of any such artificial bearing surface in vitro before it can be used for in vivo purposes.In the present study, Poly(vinyl alcohol)/Poly(vinyl pyrrolidone) (PVA/PVP) hydrogels have been investigated as potential cartilage replacements. A three-factor variable-level experiment was designed to study the wear and friction characteristics of PVA/PVP hydrogels in a pin-on-disk setup under physiologic loading conditions. Factors studied were (a) Polymer Content of PVA/PVP hydrogels, (b) Load, and (c) Lubrication. Twelve tests were conducted for 100,000 wear cycles against Co-Cr pins. A novel method involving dry polymer mass loss was tested successfully to quantify wear of hydrogels in terms of weight loss.Friction characteristics were found to depend significantly on lubrication and the interactions between load and lubrication, load and polymer content. The average coefficient of friction for synovial fluid lubrication was a low 0.035 compared to 0.1 for bovine serum lubrication. Frictional behavior of PVA/PVP hydrogels does not follow Amonton’s law of friction. Load, polymer content, and interactions between load and polymer content, and load and lubrication had significant effects on the wear of hydrogels. Higher polymer content significantly reduced the wear of hydrogels. An increase in load from 100N to 125N decreased the wear of hydrogels, but further increase in load from 125N to 150N caused an increase in the wear. The results suggest a complex mix of various lubrication mechanisms involving the hydrogels and that PVA/PVP hydrogels can be fabricated to replace cartilage with low friction and wear in synovial fluid lubrication.