- Beads give a better coating, but bonding is more of a problem with many thousands of interfaces
- Co/Cr gives better bonding of beads than Ti
- Bonding of a fibre mesh is better than beads, as it is a single unit which is bonded to the prosthesis stem
- It is best to keep porousity under 50% of implant surface
- Optimal pore size from animal studies indicates no ingrowth into porous less than 30 micron
- Ideal pore size is 100 – 200 micron and the industrial variation is 100 – 500 micron
- Optimal bone-cement gap should be less than 50 micron if bone ingrowth is to occur
- A good prosthesis cortical contact with <50 microns of motion protects against stress shielding, i.e. failure of proximal fit and fill is the cause of stress shielding
