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Biomaterials & Biomechanics - Coggle Diagram
Biomaterials & Biomechanics
Basic Principles
Definition
Requirements
Biocompatibility
Mechanical Properties
Chemical Stability/Corrosion Resistance
Osseointegration
Manufacturability/Sterilizability
Radiolucency/Imaging Compatibility
Historical Evolution
Early Attempts (Wood, Ivory)
Generations
First Generation (Bioinert)
Philosophy: Minimize Interaction
Examples: Stainless Steel, Co-Cr, Titanium, Alumina, Pt, PMMA
Second Generation (Bioactive/Biodegradable)
Philosophy: Active/Beneficial Interaction
Bioactive: Calcium Phosphates, Bioactive Glasses
Biodegradable: PLA, PGA, Magnesium Alloys
Third Generation (Tissue Regeneration)
Philosophy: Stimulate Cellular Response
Combines Bioactivity/Biodegradability
Linked to Tissue Engineering
Metallic Biomaterials
Overview
Advantages: Strength, Fatigue Life, Fabrication, Corrosion Resistance
Disadvantages: Stress Shielding, Corrosion/Ion Release, Wear Debris, Poor Bioactive Adherence, Imaging Artifacts
Stainless Steel (316L)
Composition: Fe, C, Ni, Mo, Low Carbon
Properties: High Modulus, Ductility, Corrosion Resistance (Passivity)
Historical Use: Plates, Screws, Nails
Disadvantages: Ni/C Allergy, Localized Corrosion, High Stiffness (Stress Shielding), Poor Wear Resistance
Cobalt-Chromium (Co-Cr) Alloys
Composition: Co, Cr, Mo
Properties: Excellent Wear Resistance, High Strength, High Modulus, Excellent Corrosion Resistance (Passivity)
Applications: Joint Replacing (Hip/Knee), Dental Implants
Disadvantages: Ion Release (Co, Cr, Ni), Hypersensitivity, Cytotoxicity, A1TR Modelling, High Stiffness, Stress Shielding, Cost
Titanium (Ti) and Alloys (Ti-6Al-4V)
Properties: Excellent Biocompatibility, Corrosion Resistance (TiO₂ Passive Layer), High Specific Strength, Lower Modulus than SS/Co-Cr
Forms: CP-Ti (Dental), Ti-6Al-4V (Surgical)
Applications: Hip/Knee Stems, Plates, Screws, Spinal Implants, Dental Implants
Disadvantages: Poor Wear Resistance, Wear Particle Generation (“Particle Disease”), Osteolysis, Al/V Toxicity Concerns, Notch Sensitivity
Tantalum (Ta)
Forms: Primarily Porous Tantalum
Properties: Excellent Biocompatibility, Corrosion Resistance (Ta₂O₅), AMF Compatible, High Radiopacity
Forms have Properties: Interconnected Structure, Lower Elastic Modulus (3–5 GPa), Promotes Bone Ingrowth/Osseointegration
Applications: Acetabular Cups/Augments, Spinal Cages, Bone Void Fillers
Advantages: Reduced Stress Shielding, Enhanced Osseointegration
Disadvantages: Manufacturing Difficulty/Cost, Limited Long-term Data, Brittleness (Bulk)
Nitinol (NiTi)
Class: Shape Memory Alloy (SMA)
Properties: Shape Memory Effect (SME), Superelasticity (SE), Good Biocompatibility (Passivity), Corrosion Resistance, Excellent Fatigue Resistance, Lower Modulus (30–40 GPa)
Mechanism: Martensitic Phase Transformation (Austenite ↔ Martensite)
Applications: Compression Staples, Spinal Correctors, Internal Fixators
Advantages: Adaptive Compression, Dynamic Stabilization, Reduced Stress Shielding
Disadvantages: Nickel Ion Release, Cost, Manufacturing Complexity, Limited Stiffness (Some Uses)
Polymeric Biomaterials
Overview
Advantage: Versatility, Low Density, Ease of Fabrication, Biocompatibility, Modulus Matching (PEEK), Radiolucency
Disadvantages: Lower Mechanical Strength, Wear and Creep, Sterilization Challenges, Water Absorption/Protein Adsorption, Degradation Byproducts
Ultra-High Molecular Weight Polyethylene (UHMWPE)
Structure: Long Molecular Chains
Properties: High Density/Toughness, Impact Strength, Low Friction, Low Moisture Abs., Excellent Bulk Biocompatibility
Applications: Joint Bearings (Hip/Knee liners)
Primary Failure: Wear and Wear Particle Generation
Wear Consequences: Inflammation, Osteolysis, Aseptic Loosening
Advancements: Crosslinking (Radiation), Thermal Treatments (Annealing, Remelting), Antioxidants (Vitamin E)
Challenges: Oxidation (Free Radicals), Brittleness (with over-crosslinking), Creep
Polymethyl Methacrylate (PMMA)
Common Name: Bone Cement
Form: Two-component (Powder+Liquid)
Properties: Amorphous, Good Compressive Strength, Brittle, Low Tensile/Shear Strength, Exothermic Polymerization
Applications: Anchoring Prosthesis (Hip/Knee), Vertebroplasty, Bone Defect Filling, Antibiotic Delivery (ALBC)
Advantages: Immediate Fixation, Fills Cavities, Stress Distribution, Antibiotic Loading
Disadvantages: Monomer Toxicity (MMA), Exothermic Heat (Thermal Necrosis), Brittleness/Failure, Debris Generation (Osteolysis), Lack of Biological Integration (Mechanical Interface)
Polyetheretherketone (PEEK)
Class: High-Performance Thermoplastic (HPK)
Properties: Semi-Crystalline, Chemical/Thermal Stability, Bioinert, Elastic Modulus Closer to Bone (~4 GPa), Radiolucent, Lightweight
Applications: Spinal Fusion Cages, Fracture Fixation (CF-PEEK), Suture Anchors, Patient-Specific Implants
Advantages: Reduced Stress Shielding, Clear Imaging, Good Biocompatibility (Bioinert)
Disadvantages: Bioinertness (Lack of Osseointegration), Wear Properties (Bioinert), Cost/Complexity, Brittleness (CF-PEEK), Surface Modification Needs
Biodegradable Polymers
Rationale: Temporary Support, Avoid Removal Surgery, Gradual Load Transfer
Types (Aliphatic Polyesters): PLA, PGA, PLGA, PCL, PDO
Degradation: Hydrolysis (Ester Bonds)
Applications: Fracture Fixation Screws, Pins, Sutures, Drug Delivery, Tissue Engineering Scaffolds
Advantages: No Removal Surgery, Load Transfer, Reduced Stress Shielding, Radiolucency
Disadvantages: Inflammatory Response (Acidic Hydrolysis), Premature Strength Loss, Inconsistent Degradation, Poor Cell Affinity
Ceramic Biomaterials
Overview
Categories: Bioinert (Alumina, Zirconia), Bioactive/Bioresorbable (CaP, Bioactive Glass)
General Properties: High Hardness, Compressive Strength, Wear Resistance, Biocompatibility, Corrosion Resistance
Advantages: Superior Wear, Biocompatibility/Inertness, Bioactivity/Osteointegration, Bioresorbability
Disadvantages: Brittleness (Low Fracture Toughness), High Stiffness, Manufacturing Difficulty, Potential for Noise (Squeaking)
Alumina (Al₂O₃) and Zirconia (ZrO₂)
Alumina: High Purity, Bioinert, Excellent Wear Resistance, Brittle (Low Toughness); Applications: Joint Bearings
Zirconia (Y-TZP): Bioinert, Higher Fracture Toughness/Strength, Susceptible to Low-Temp Degradation (Aging); Applications: Joint Bearings
Alumina/Zirconia Composites (ZTA, BIOLOXdelta): Combine Hardness & Toughness; Improved Resistance, Low Infection Risk, Squeaking Risk
Calcium Phosphates (CaPs)
Similarity to Bone Mineral
Hydroxyapatite (HA): Stable, Very Slow Resorption, Osteoconductive, Bioinert; Uses: Coatings, Grafts, Scaffolds
β-Tricalcium Phosphate (β-TCP): Higher Resorption, Osteoconductive, Bioactive, Brittle; Uses: Grafts, Scaffolds
BCPs (HA/TCP): Tunable Resorption, Stability vs Resorbability; Uses: Grafts
Advantages: Biocompatibility, Bioactivity, Resorbability
Disadvantages: Brittleness, Low Strength, Unpredictable Resorption
Bioactive Glasses
Type: Surface-Reactive Glass-Ceramics
Key Feature: Forms HA Layer (Bonds to Bone)
Mechanism: Ion Exchange, Dissolution, BCA Formation
Properties: Highly Bioactive, Degradable, Ion Release (Angiogenesis), Antibacterial (S53P4), Matches Bone Modulus
Compositions: 45S5 (Bioglass), S53P4 (Biosilicate)
Applications: Grafts/Fillers, Coatings, Dental, Composites
Advantages: High Bioactivity, Strong Bonding, Osteointegration, Ion Release
Disadvantages: Weak/Brittle, Degradation Control
Composite Biomaterials
Design Principles
Selection of Constituents (Matrix + Reinforcement)
Rationale: Overcome Limitations of Monolithic Materials, Mimic Bone
Control of Reinforcement (Type, Size, Vol. Fraction, Orientation)
Matrix–Reinforcement Interface (Strong Bond)
Biocompatibility and Biodegradation
Manufacturing Process