6. Judet brothers- heat curved acrylic femoral head
prosthesis-fragmentation of acrylic with wear- severe
tissue reaction-bone destruction
Thompson and Moore – metallic endoprosthesis with
medullary stems- erosion of bone on pelvic side
7. Metal on metal
Urist, Ring and McKee Farrar
Friction metal wear
High incidence of loosening and pain.
8. Sir John Charnley
-Low friction torque arthroplasty
-Surgical alteration of hip biomechanics
-Lubrication
-Material design
-Operating room environment
-PMMA
9. 1 st Charnley prosthesis
Moore prosthesis stainless steel femoral component
Thin polytetrafluroethylene shell for acetabulum
12. Adhesive wear
Adhesion during contact of opposing bearing
surfaces
Sliding breaks these contacts
Strength of adhesion exceeds strength of material
Particles are pulled from the material
44. Biologic effectsCoC MoM MoHCLUH
WPE
Cell
toxicity
No Yes No
Local
tissue
reaction
Low Low Low
Chromo.
changes
NR R NR
Hypersensi
tivity
NR R NR
Carcin. NR * NR
47. Next generation polyethylenes
1. Sequential irradiation and annealing
2. Irradiation and solid state deformation by extrusion
below melting temperature
3. Vit E antioxidant containing polyethylene
48. Metal on metal
Increase in femoral head size –greater sliding velocity
and increased probability of fluid film lubrication –
decrease in wear
Reduced risk of impingement and dislocation
32 mm and bigger
49. Ceramic on metal
Alumina head
Cobalt chromium alloy cup
Reduced wear rate 100 fold
Clinical studies underway
51. Take home message
There is no 100 % ideal bearing surface
Hard/hard and hard/soft
Tribology –friction, lubrication and wear
Wear causes osteolysis
52. Modern bearings: - all have low wear
Young and active patients Hard/hard bearings will
produce less wear debris but noise remains a
problem
53. For hard on hard bearings cup placement is
important to reduce risk of impingement, excessive
wear and fracture.
Metal on metal bearings release metal ions and
corrosion products and probably should not be
used for patients with impaired kidney function or
women of child bearing age.