- Discussion:
    - see bone ingrowth 
    - most important factor for initial success of cementless THR;
    - reduces micromotion between implant and bone along entire length of implant;
    - pore size:
            - porous ingrowth surfaces w/ beads or wires that create pore-interconnection sizes in range of 150-400-  micrometers are optimum;
            - references: Biologic fixation of porous-coated implants.        
    - types of coating surfaces: 
         - titanium beads; 
         - sintered beads; 
         - hydroxyapatie coating: 
                - the outcome studies on this have generally been poor, with the exception of hydroxyapatite threaded implants;
                - in the study by Manley et al 1998, 11% of hydroxyapatite cups had been revised by 5 years;
                       - these authors concluded that the hydroxapatite surface could not stand the tensile forces at the cup bone interface;
                       - it is important to point out that 99% of threaded hydroxyapatite cups were stable at 5 years; 
         - grit-blasted surfaces:
                   - process textures the metal surface with a pressurized spray of aluminum oxide grit or stainless steel shot which creates an irregular surface (between 3-8 micrometers in depth); 
          - titanium plasma spray: (see titanium)
                   - plasma spray can be applied to the implant without having to heat the implant (less weakening); 
                   - titanium exposed to air/blood creates a titanium oxide surface conducive to bone ingrowth;
                   - the rougher the surface, the greater the surface area for creation of titanium oxide layer;
                   - goal after fixation is creation of increased bone density along the stem;
                   - references:
                         - Plasma spray-coated Ti femoral component for cementless total hip arthroplasty.
                         - Press-fit stability of uncemented hemispheric acetabular components: a comparison of three porous coating systems.
                         - Effect of circumferential plasma-spray porous coating on the rate of femoral osteolysis after total hip arthroplasty.
                         - Osseointegration of sintered porous-surfaced and plasma spray-coated implants: An animal model study of early postimplantation healing response and mechanical stability. 
                         - Influence of various structure treatments on histological fixation of titanium implants.
                         - Primary cementless hip arthroplasty with a titanium plasma sprayed prosthesis.

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- references: 

The influence of surface-blasting on the incorporation of titanium-alloy implants in a rabbit intramedullary model. 

Biologic fixation of porous-coated implants

         - Cementless total joint arthroplasty prostheses with titanium-alloy articular surfaces. A human retrieval analysis.
         - Clinical performances of ingrowth surfaces.
         - Primary total hip reconstruction with a titanium fiber-coated prosthesis inserted without cement. 
         - The influence of surface-blasting on the incorporation of titanium-alloy implants in a rabbit intramedullary model.
         - Periprosthetic bone loss in total hip arthroplasty. Polyethylene wear debris and the concept of the effective joint space.