What is an Artificial hip made of?
What is an Artificial hip made of?
A titanium or cobalt-chrome stem, a ceramic or metal ball, and a crosslinked polyethylene socket liner that is the wear surface.
The joint does not usually fail because the metal breaks; it fails because of what the wear particles do. Polyethylene debris provokes an immune response that resorbs the bone around the implant — osteolysis — loosening it, which is why reducing wear has driven every material change for thirty years. Highly crosslinked polyethylene, introduced around 2000, cut wear rates by roughly an order of magnitude. Metal-on-metal bearings were adopted in the 2000s to avoid plastic wear entirely, and produced a serious failure of their own: cobalt and chromium ions caused local tissue reactions and revision, leading to the 2010 ASR recall and a wholesale retreat from the design.
Component by component
| Part | Material | Why that material |
|---|---|---|
| femoral stem | titanium alloy (Ti-6Al-4V) or cobalt-chromium | Titanium's stiffness is closer to bone than steel, so it transfers load into the femur instead of shielding it and letting it thin. |
| head | cobalt-chrome, or alumina and zirconia-toughened alumina ceramic | Ceramic is extremely hard and smooth, so it wears the plastic liner far more slowly, at a very small risk of fracture. |
| acetabular shell | titanium with a porous or plasma-sprayed surface | Bone grows into the roughened surface and fixes the cup biologically, which lasts better than cement in younger patients. |
| liner | highly crosslinked ultra-high-molecular-weight polyethylene, often vitamin E stabilised | This is the bearing surface and the life-limiting part; crosslinking cut wear dramatically, and vitamin E stops the crosslinked plastic oxidising. |
| fixation | polymethyl methacrylate bone cement, where used | Cement gives immediate stability, which matters in older bone that will not grow into a porous surface reliably. |
Other medical and personal care objects
- Condom Dipped natural rubber latex, or synthetic polyisoprene or polyurethane for latex allergy — plus silicone lubricant.
- Surgical mask Three layers of polypropylene, of which only the electrostatically charged middle one does the filtering.
- Diaper (nappy) A superabsorbent polymer that holds many times its own weight in fluid, sandwiched between nonwoven plastic layers.
- Contact lens A water-swollen polymer gel — and the whole design problem is getting oxygen through it to the cornea.
- Dental filling Either a mercury-silver amalgam or a light-cured resin packed with glass — and the resin shrinks as it sets.
- Tampon Compressed cotton, rayon or a blend, with a withdrawal cord and either a cardboard or plastic applicator.
- Eyeglass lens Almost never glass — usually CR-39, polycarbonate or a high-index plastic, under several thin coatings.
- Adhesive bandage (plaster) A plastic or fabric backing with pressure-sensitive adhesive, and a pad faced with a film that will not stick to the wound.
- Syringe A polypropylene barrel and plunger with a rubber tip seal, and a stainless steel needle on a standard taper.
Common questions
- What is an Artificial hip made of?
- A titanium or cobalt-chrome stem, a ceramic or metal ball, and a crosslinked polyethylene socket liner that is the wear surface.
- What is the femoral stem of an Artificial hip made of?
- Titanium alloy (Ti-6Al-4V) or cobalt-chromium. Titanium's stiffness is closer to bone than steel, so it transfers load into the femur instead of shielding it and letting it thin.
- What is the head of an Artificial hip made of?
- Cobalt-chrome, or alumina and zirconia-toughened alumina ceramic. Ceramic is extremely hard and smooth, so it wears the plastic liner far more slowly, at a very small risk of fracture.
Related pages
- Condom Dipped natural rubber latex, or synthetic polyisoprene or polyurethane for latex allergy — plus silicone lubricant.
- Surgical mask Three layers of polypropylene, of which only the electrostatically charged middle one does the filtering.
- Diaper (nappy) A superabsorbent polymer that holds many times its own weight in fluid, sandwiched between nonwoven plastic layers.
- Contact lens A water-swollen polymer gel — and the whole design problem is getting oxygen through it to the cornea.
- Dental filling Either a mercury-silver amalgam or a light-cured resin packed with glass — and the resin shrinks as it sets.
- Tampon Compressed cotton, rayon or a blend, with a withdrawal cord and either a cardboard or plastic applicator.
- Eyeglass lens Almost never glass — usually CR-39, polycarbonate or a high-index plastic, under several thin coatings.
- Adhesive bandage (plaster) A plastic or fabric backing with pressure-sensitive adhesive, and a pad faced with a film that will not stick to the wound.
- Pencil Stationery and paper
- Tennis ball Sport and games
- Banknote Around the house
- Golf ball Sport and games
- Paper Stationery and paper
- Glass Building materials
Sources
- Official vendor product documentation — At One Place