HealthMap

Nickel-Titanium Shape Memory Alloy (Nitinol) in Stents

Overview of Nitinol

• Composition: Approximately 50% nickel and 50% titanium (NiTi)
• Primary Properties: Exceptional shape memory and superelasticity (pseudoelasticity)
• Biocompatibility: Generally well-tolerated by human tissues, forming a protective titanium oxide surface layer

Why Nitinol is Used in Stents

• Superelasticity: Allows the stent to undergo large deformations and return to its original shape without permanent damage
• Constant Radial Force: Provides continuous, gentle outward pressure on blood vessels or other tubular structures to keep them open
• Kink Resistance: Withstands the dynamic movements and bending stresses within the human body (e.g., in the superficial femoral artery)

Types of Nitinol Stents

• Self-Expanding Stents: Compressed into a delivery catheter and deploy automatically upon release due to the material's superelastic properties
• Shape Memory Stents: Expand to their predetermined functional size when exposed to body temperature (thermo-mechanical activation)

Clinical Considerations

• Nickel Sensitivity: Patients with a documented, severe hypersensitivity to nickel may experience adverse immunological or inflammatory reactions
• Surface Modifications: Often treated with specialized passivated coatings to minimize direct tissue contact with free nickel ions