Flexibility / Kink Resistance

Ability of the device to bend in order to accommodate the predetermined clinically relevant radius or angle it will be required to negotiate during access and delivery.

Also known as Kink diameter or Kink radii.

Test Procedure

There are 2 main methods to study the kink radius:

1) Using a cone mandrel with decreasing diameter to determine when the kink occurs (without measure of sample diameter).

2) Using several decreasing diameter gauges successively to determine when the kink occurs and measuring the diameter of sample and residual angles.

Test is performed on the location(s) defined in the protocol. If required in protocol, guide wire is inserted inside the tested sample.

The sample is wrapped (over 180°) around a cone-shaped mandrel with successively smaller radii until the device kinks or the lumen collapses. When the device is kinked, the test advancement is stopped and the diameter of cone-shaped (where the kink occurs) is measured with a caliper to determine the kink radius.

This method can also be used to determine the kink radius of a stent in a mock vessel. The stent is deployed in a straight silicone tube, the assembly is wrapped around the mandrels as described above. The test proceeds until the stent kinks or exhibits a diameter reduction of more than 50% and recovers to the original geometry after being released.


Test Sample Preconditioning (If applicable)

Balloons should undergo accelerated and real-time aging.



  • Graduated cone-shaped mandrel
  • Calibrated Pin Gauges
  • Calibrated Contactless optical measurement system
  • Calibrated Caliper
  • Temperature controlled test chamber
  • Calibrated thermometer

Measured Parameters

Kink Diameter

Kink Location

Stent Diameter



  • PTA, PTCA, coronary and peripheral stent delivery systems – functional performance during simulated use
  • TAVI and TMVR delivery systems – functional performance during simulated use
  • Thrombectomy devices — functional performance during simulated use
  • Guidewires testing – functional performance during simulated use
  • Endoscopic devices – functional performance during simulated use
  • RF ablation catheters testing – functional performance during simulated use
  • Any interventional delivery systems – functional performance during simulated use

Service Levels

Applicable Standards

  • ISO 25539-2:2020
    Cardiovascular implants — Endovascular devices — Part 2: Vascular stents

  • FDA-1545
    FDA Guidance: Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems – Guidance for Industry and FDA Staff

  • FDA-1608
    FDA Guidance: Certain Percutaneous Transluminal Coronary Angioplasty (PTCA) Catheters – Class II Special Controls Guidance for Industry and FDA

  • FDA-1658
    FDA Guidance: Coronary and Carotid Embolic Protection Devices – Premarket Notification [510(k)] Submissions

Related Tests

OLE0810, OLE1413

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