Testing System for Bioabsorbable Plates and Screws – ASTM F2502

ASTM F2502 is a standard for testing Bioabsorbable Plates and Screws for Internal Fixation Implants.

These types of plates and screws are resorbed into the body once implanted to unstable bone or tissue connected to bone. The advantage over a metallic fixation device is that a bioabsorbable device does not need to be removed. The challenge to medical device manufacturers of bioabsorbable devices is to ensure full healing takes place before the bioabsorbable device is fully deteriorated.

There are four Annexes describing the testing procedures to follow in this specification.

ADMET’s Biaxial eXpert 2610 is the perfect testing system solution for performing Annex 1-4

A1-Torsional Properties

• Torsional Yield Strength
• Maximum Torque
• Breaking Angle

Rate of Torsional Speed applied to the sample -1 to 5 rotations/minute

Testing Times -Document 7 measuring points over time. (ie; 1 day, 1 week, 4 weeks, etc.)

Solution -Specimens must be submerged in bath- see conditioning 5.4 and 6.1 and constant temperature of 37^C +-1^

Procedure

1. Insert specimen in collet grip- 5 threads or 20% of total size should be anchored in grip.
2. Apply torsional load of 1 to 5 r/min to failure.
3. Apply minimal axial load to balance grip.
4. From Torque vs. angle curve plot calculate Torsional Yield Strength by offset method, report max torque and breaking angle (both determined by max torque reported)

A2- Driving Torque

1. Attach specimen to fixture and align with pilot hole.
2. Apply 1-5r/min torsional load for 4 rotations (1440 degrees) and 1.14kg or less axial load to maintain screw driver bit in the screw head.
3. Record max load in Nm.
4. Compare a variety of specimen sizes.

A3-Axial Pullout

1. Insert specimen in collet grip- 5 threads or 60% of total length of fully threaded screw.
2. Clamp top of screw (head)
3. Tension load at 5mm/min until failure or release from test block.
4. Plot load vs. displacement – note max load and mode of failure.

A4-Single Cycle Bend Testing

• Load plate onto rollers (roller diameter dependent on plate size, symetry or asymetry, hole spacing)
• Apply load of increasing magnitude by using position control and plot Load vs. Displacement.

Calculate

1. Bending stiffness (N/mm)
2. Bending strength (N-m)
3. Bending structural stiffness EI (N-m*m)
4. 0.2% offset displacement (N/mm)

Specifics on the materials and manufacture, conditioning, care and handling of these devices is explained in the full description of this specification. F2502-05