Musculoskeletal System Flashcards
What is osteoarthritis?
Progressive degeneration of joint cartilage and underlying bone. Causes pain and stiffness.
What conclusions have been made regarding regenerative knee therapies?
Not sufficient evidence to recommend a single method for treating knee cartilage defects.
What is the primary reason for revision surgery in joint replacements?
Aseptic lossening.
What is tribology?
Study of friction, wear, lubrication and the design of bearings. The science of interacting surfaces in relative motion.
What material choices are their for replacement joint materials?
Typically use combinations of metal, plastic (UHMWPE) or ceramic for cup and head.
What are the three main lubrication regimes and the lambda values associated with them?
- Boundary lubrication (lambda < 1)
- Mixed lubrication (1 < lambda < 3)
- Hydrodynamic/fluid film lubrication (lambda > 3)
Based on the film thickness equation for elastohydrodynamic lubrication, how can increased possibility of fluid film lubrication (lambda > 3) be achieved?
Increasing head radius, R, to increase the minimum film thickness h_min.
What is elastohydrodynamic lubrication?
A lubrication regime in which significant elastic deformation of the surfaces takes place. Deformations exceed film thickness.
Alters the shape and thickness of the lubricant film in the contact.
Why are large diameter MoM hips no longer used?
Large metal head with reduced stem taper created mechanically assisted crevice corrosion (MACC) at taper junction.
What can be learned from the failure of MoM hips?
- Need appropriate pre-clinical testing.
- Phased introduction.
- Need detailed post-market surveillance.
- Balance commercial pressures with patient safety.
