Week 6 Flashcards
What are the 5 characteristics of an arthrotic hip joint?
- Sclerosis (=tissue hardening)
- Subchondral cysts (= fluid-filled space inside a joint)
- Joint space narrowing (=the cartilage no longer keeps the bones a normal distance apart)
- Osteophyte formation (bone spurs)
- Cartilage damage (> pain)
What is a Total Hip Arthroplasty (THA)?
Arthroplasty is a surgical procedure to restore the function of a joint.
Is is a successful operation: outcome is normal walking (unassisted), >90% patients no pain, 90% still functional after 10y.
3 types of hip implants?
1 Cemented implant
2 Uncemented implant
3 Resurfacing implants
Characteristics of cemented implants:
- type of cement
- problems
- Use PMMA cement to fit the stem in the bone.
- problems:
1 Implant fracture
2 Loosening: stem-cement movement > cracks > wear particles (osteolysis= bone resorption) > loosening of the bone cement interface. This is the main problem.
3 Cement is exotherm; gets hot in patient, kills cell
Characteristics of uncemented implants
- use of coating
- problem
- Use some sort of coating to bone the stem to the bone: porous bead coating, plasma flame spray coating, hydroxyapatite coating.
- Problems:
1 ingrowth failure; fibrous tissue formation, migration/ subsidence and bone formation.
2 Bone resorption due to ‘stress-shielding’; uncemented implants bigger & stiffer than cemented implants.
Bone loss quantified per area; Gruen zone
Characteristics of resurfacing implants
- Only the articular surface is replaced.
- Can be either cemented or uncemented
- less stress shielding, other problems similar.
What are the 3 major failure scenarios regarding implants?
- Bone loss related to stress shielding; makes revision difficult, higher risk of fracture due to a fall.
- Implant loosening; leads to migration/ fractures.\
- Wear induced osteolysis (resorption); leads to loosening.
What is RSA?
RadioStereometric Analysis:
- is a technique used to predict long-term implant stability by studying its early behavior.
- small tantalum beads placed in bone around implant > compare if beads are moving (not bad perse).
- enables the calculation of translation/ rotation of implant relative to the bone in 3D.
- highly accurate.
What is SPECT/PET imaging?
- inject radioactive tracers that are taken up by the bone.
- Reveal bone remodeling activity at the implant surface, thus successful ingrowth.
What is wear induced osteolysis?
What does wear induced osteolysis depends on?
= the process by which prosthetic debris mechanically released from the surface of prosthetic joints induces an immune response that favors bone catabolism, resulting in loosening of prostheses with eventual failure or fracture.
Material
Particle size
Particle morphology shape/form
Wear rate
Wear can also result from stem/cement movement; damage accumulation. What are the steps that are involved?
Cyclic loading prosthesis 1. loosening stem-cement interface 2. crack formation in cement 3. micro-movement stem 4. formation of wear particles 5. bone resorption around cement/implant failure
What 3 types of animal models are there?
- Normal animals
- Animals with defect - naturally occurring
- Animals with defect - experimentally induced
3 causes for Animals with deficits – naturally occurring
Animals with deficits – naturally occurring:
o Old animals, spontaneously occurring conditions or spontaneously occurring mutations.
o Genetic lines: inbred strains and their crossings.
o Selected extremes from a particular animal population.
3 causes for Animals with deficits – experimentally induced
Animals with deficits – experimentally induced:
o Transgenic and knock-out animals.
o Selection lines resulting from selective breeding.
o Animals with induced disruptions (manually, electronically, pharmaceutically).
What are the 3 R’s for legal requirement for animal experiments?
Replacement
Reduction
Refinement
