ASTM F2009 Tensile Test on the Femoral Head

ASTM F2009 describes a standardized test method for determining the axial tensile force required to release the modular femoral head from a femoral stem. This test is crucial for evaluating the stability of modular hip implants, as too low a retention force could cause premature loosening in the body, while too high a retention force makes replacement more difficult.

The standard is used in the following areas:

• Medical industry Development and quality assurance of hip endoprostheses.
• Test laboratories and research facilities: investigation of the longevity and mechanical properties of modular implants.
• Regulatory authorities: ensuring compliance with medical safety standards.
  

• Test object: modular femoral head and conical connection of the femoral stem.
• Materials: biocompatible metals such as cobalt-chromium alloys or titanium as well as ceramics.
• Dimensions: the exact dimensions of the components vary depending on the manufacturer, but the tests must be carried out with standardized test specimens.
• Assembly: the femoral head is pressed onto the cone of the femoral stem with a defined force in accordance with the manufacturer's instructions.

Mounting the test specimen:

• The femoral head is placed on the cone of the femoral stem under defined conditions (e.g. ambient temperature).
• Assembly is carried out with a specified axial press-in force in order to simulate a realistic press fit.
• The press-in force is documented as it has an influence on the subsequent tensile force measurement.

Clamping in the testing machine:

• The femoral stem is fixed in a special holder to prevent lateral movement or twisting.
• The femoral head is connected to a traction device that applies a uniform axial load.

Tensile tests:

• The testing machine pulls the femoral head axially from the femoral stem at a constant speed.
• The standardized test speed is typically in the range of 10-50 mm/min.
• The axial force required until the femoral head is completely separated is recorded continuously.

Data acquisition and evaluation:

• The maximum measured tensile force (in Newtons) is used as a reference value for the strength of the conical connection.
• Other parameters such as elongation behavior or deformation of the joint can also be analyzed.

• Standard axial tensile test: one-time measurement of the maximum separating force.
• Repeated tests: multiple assembly and disassembly tests to analyze the influence on the holding force.
• Long-term studies: testing under simulated long-term loads, e.g. after artificial aging of the components.
• Investigation of environmental influences: measurements under different temperatures or humidity conditions.

To perform a standard-compliant test in accordance with ASTM F2009, the testing machine must meet the following requirements:

Mechanical requirements

High frame rigidity:

• the testing machine must have a highly rigid frame to prevent deformation during the test.
• Unintentional lateral movement of the test specimens can falsify the measurement result.

Precise axially guided load:

• the machine must ensure that the tensile force acts exactly in the axial direction.
• Lateral loads or bending moments must be excluded.

High-resolution load cell:

• the machine requires a load cell with high accuracy (±0.5 % or better).
• The typical measuring range is between 500 N and 10,000 N, depending on the implant size.

Uniform test speed:

• the machine must ensure a precise and constant pulling speed (e.g. 10-50 mm/min).

Software and control requirements:

Automatic data acquisition:

• the testing software should enable the complete recording of force-displacement diagrams.
• A real-time display of the measured values facilitates evaluation.

Flexible test sequences:

• individual test parameters should be adjustable (e.g. different test speeds).
• Can be adapted to different implant designs.

Data export and reporting:

• it should be possible to generate test reports automatically.
• Interfaces for further processing of the data (e.g. in Excel or laboratory management systems).

ZwickRoell offers high-precision testing solutions for ASTM F2009 that are optimally matched to the requirements of medical technology:

• Maximum precision: ZwickRoell testing machines offer precise force measurement and axial guidance for standard-compliant results.
• Flexibly adaptable test setups: special clamping devices for different implant sizes and cone geometries.
• State-of-the-art testing software: testXpert III enables intuitive operation, automatic evaluation and comprehensive documentation.
• Many years of experience in medical technology: ZwickRoell is a leading global provider of biomechanical testing of implants.
• Compliance with ASTM and ISO standards: the machines meet the highest quality and safety standards.

These features make a ZwickRoell testing machine the perfect solution for standard-compliant testing to ASTM F2009 and ensure reliable quality control of modular hip implants.