Orthonotes
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Metals: stainless steel (316L), cobalt‑chrome, titanium alloys; differences in modulus, corrosion resistance, MRI artifacts. Polymers: UHMWPE (arthroplasty bearings), PMMA (bone cement), PEEK (spacers). Ceramics: alumina/zirconia (bearings), hydroxyapatite/tricalcium phosphate (coatings, bone graft substitutes). Surface engineering: porous coatings, grit‑blast, plasma spray HA for osseointegration. Failure modes: wear (PE oxidation), corrosion (fretting, crevice, galvanic), fatigue fracture, osteolysis.
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Biomaterials are materials used to replace, augment, or support biological structures of the musculoskeletal system. In orthopaedics, biomaterials are used in implants, prostheses, fixation devices, bone substitutes and joint replacements.
An ideal orthopaedic biomaterial must possess appropriate mechanical strength, corrosion resistance, biocompatibility and long-term durability. Because orthopaedic implants often bear significant mechanical loads, the material properties must match the mechanical demands of the skeleton while also remaining biologically compatible with surrounding tissues.
Orthopaedic biomaterials are commonly classified based on their chemical composition and mechanical properties.
| Category | Examples | Common Uses |
|---|---|---|
| Metals | Stainless steel, titanium alloys, cobalt-chrome | Plates, screws, nails |
| Ceramics | Hydroxyapatite, alumina | Bone substitutes, joint bearings |
| Polymers | Polyethylene, PMMA | Joint prostheses, bone cement |
| Composites | Carbon fiber reinforced materials | Advanced implants |
Metals are the most commonly used biomaterials in orthopaedic surgery because of their high mechanical strength and durability. They are widely used in fracture fixation devices such as plates, screws and intramedullary nails.
| Material | Properties | Applications |
|---|---|---|
| Stainless Steel | Strong, inexpensive | Plates, screws |
| Titanium Alloy | Biocompatible, corrosion resistant | Joint prostheses |
| Cobalt Chrome | High wear resistance | Joint replacement components |
Ceramics are brittle materials but have excellent biocompatibility and wear resistance. They are often used in joint replacement bearings and bone graft substitutes.
Hydroxyapatite closely resembles the mineral component of bone and promotes osteointegration.
Polymers are lightweight materials commonly used in joint replacement and bone cement.
| Polymer | Use |
|---|---|
| Ultra-high molecular weight polyethylene | Joint prosthesis bearings |
| PMMA | Bone cement |
Biocompatibility refers to the ability of a biomaterial to perform its intended function without producing harmful effects on surrounding tissues.
Corrosion refers to the degradation of metallic implants due to chemical reactions within the body.
| Type | Description |
|---|---|
| Galvanic corrosion | Occurs between different metals |
| Crevice corrosion | Occurs in small spaces |
| Pitting corrosion | Localized damage |
Stress shielding occurs when a rigid implant carries most of the mechanical load, resulting in reduced stress on the surrounding bone. According to Wolff law, reduced mechanical stress leads to bone resorption.
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