Overview
ISO 16402:2008 specifies a standardized laboratory procedure for flexural fatigue testing of acrylic resin cements used in orthopaedics. The standard applies to resin cements based on poly(methacrylic acid esters) and defines specimen preparation, environmental conditioning, test apparatus and the two main fatigue test methods (Wöhler S/N curve method and the low stress method). NOTE: ISO 16402:2008 does not cover clinical or user safety hazards associated with cement use.
Keywords: ISO 16402, acrylic resin cement, flexural fatigue testing, bone cement, orthopaedics, four‑point bend test, S/N curve.
Key topics and requirements
- Scope: Applies to polymerized acrylic resin cements based on poly(methacrylic acid esters).
- Specimen geometry: Rectangular bars, nominally 75 × 10 × 3.3 mm (length × width × thickness), finished with 400‑grade emery paper.
- Conditioning: Specimens stored in Ringer’s solution at 37 ± 1 °C for 4 weeks prior to testing (per ISO 16428).
- Test rig and loading:
- Four‑point bend test configuration (outer span 60 ±1 mm, inner span 20 ±1 mm) with rolling loading points.
- Bend machine capable of up to 200 N, cyclic sinusoidal loading at 5 ± 0.5 Hz, load‑controlled; minimum force 5 N.
- Quasi‑static test: increase load at 90 ± 10 N/min to fracture.
- Fatigue methods:
- S/N (Wöhler) method: typically 5 specimens per stress level, up to 5 million cycles, starting at ~80% of quasi‑static strength and stepping down.
- Low stress method: 10 specimens per level; specified stress levels 35 MPa, 25 MPa and 20 MPa; up to 5 million cycles.
- Data and reporting: Required items include cement identity (batch/lot), quasi‑static bending strength (mean ± SD), S/N diagram, fatigue strength at 5 million cycles, fatigue/quasi‑static ratio, and median lifetimes for low stress tests.
Applications and users
- Orthopaedic device manufacturers validating bone cement performance for implants.
- Materials and biomechanics laboratories performing comparative fatigue testing and QA.
- Regulatory and conformity assessment bodies reviewing mechanical durability data for submissions.
- R&D teams optimizing cement formulations and comparing to control (commercial) bone cements using the same test methods.
Practical value: ISO 16402 provides reproducible, comparable metrics (quasi‑static strength, S/N curves, fatigue life at clinical stress levels) used for material selection, quality control and regulatory evidence of long‑term mechanical behaviour.
Related standards
- ISO 5833:2002 - Implants for surgery - Acrylic resin cements (referenced for test rig details)
- ISO 16428 - Test solutions and environmental conditions for static and dynamic corrosion tests on implantable materials and medical devices (for Ringer’s solution conditioning)
For implementation, follow ISO 16402:2008 exactly for specimen preparation, environmental conditioning and data reporting to ensure consistent, comparable fatigue performance results.
