Posted by Debbi Cohen on Wed, Aug 11, 2010 @ 11:39 AM
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
- Insert specimen in collet grip- 5 threads or 20% of total size should be anchored in grip.
- Apply torsional load of 1 to 5 r/min to failure.
- Apply minimal axial load to balance grip.
- 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
- Attach specimen to fixture and align with pilot hole.
- 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.
- Record max load in Nm.
- Compare a variety of specimen sizes.
A3-Axial Pullout
- Insert specimen in collet grip- 5 threads or 60% of total length of fully threaded screw.
- Clamp top of screw (head)
- Tension load at 5mm/min until failure or release from test block.
- 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
- Bending stiffness (N/mm)
- Bending strength (N-m)
- Bending structural stiffness EI (N-m*m)
- 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
Many who use this method also refer to ASTM F543 A1 and
ASTM F543 A2.
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Posted by Debbi Cohen on Tue, Jun 29, 2010 @ 07:59 AM
ISO 594/1 describes dimensions, testing profile, and parameters for testing conical fittings with a 6% (luer) taper for hypodermic syringes, needles, and certain other medical equipment, such as transfusion and infusion sets. This standard covers rigid and semi-rigid materials for gauging and performance.
Several mechanical tests in section 5, figures 4+5 require torque testing.
Section 5.2
- First, according to figures 4 + 5, connect fitting to steel male or female reference fitting.
- Assemble components by applying an axial force of 27.5 Newtons (6.18 lbf) for 5 seconds while applying a torsional force < or = 0.1Nm (.88 lb-in) and < or = to 90 degrees.
- Introduce water
- Expel Air
- Check to determine if outside of fitting is dry
- Seal the outlet - bring internal pressure to 300kPa.
- Maintain pressure 30 seconds.
**Highlights on the Torsion Requirements for Section 5.3.1.1 and 5.5.1.
* Apply axial force of 25N for 5 seconds simultaneously applying 0.1Nm to an end limit of 90 degrees. Full description of ISO 594/1-1986 is necessary to complete this test.
ADMET offers a vertical or horizontal 81T Torsion Testing System. to meet the Torsion requirements of this standard. ADMET's full line of standard testing systems can be tailored or modified to meet the additional requirement of ISO 594/1.
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Posted by Debbi Cohen on Mon, Mar 01, 2010 @ 02:47 PM
ASTM F543 Annex A2 is used to measure the torque required to drive a bone screw into a test block made of a rigid unicellular polyurethane foam. The results obtained from this test bear no direct correlation to the torque required to insert a bone screw in human or animal bone. This method is used as a quality control check for maintaining product uniformity.
The basic test procedure for determining the insertion and removal torque is as follows:
- Clamp the test block with a pre-drilled pilot hole into the machine.
- Drive the bone screw into the test block at a rate between 1 and 5 rpm. The insertion torque will be the maximum torque measured within the first four revolutions of the bone screw.
- Reverse direction and record the maximum removal torque during the four revolutions required to remove the bone screw.
Note: A 1.14 kg (2.5 lb) or less axial force should be applied to maintain engagement between the screw head and drive bit.
The embedded video demonstrates the ADMET E81 Torsion Tester recording the insertion and removal torque of a bone screw according to ASTM F543-A2. The test apparatus is a 20Nm capacity vertical torsion tester equipped with ADMET's MTESTQuattro® PC based Torsion Testing Software.
For more information on the ADMET Torsion Systems call 1-800-667-3220 or sales@ADMET.com or www.ADMET.com.
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Posted by Debbi Cohen on Mon, Mar 01, 2010 @ 02:41 PM
ASTM F543 Annex A1 is used to determine the Torsional Properties of Metallic Bone Screws. The results obtained from this test bear no direct correlation to the torque required to insert a bone screw in human or animal bone. This method is used as a quality control check for maintaining product uniformity or to compare the mechanical properties of different, yet similarly sized, products.
Annex A1 is used to measure torsional yield strength, maximum torque and angle at break for metallic bone screws. A description of the ASTM F543-A1 test procedure is as follows:
- Clamp the specimen in a holding device so that five threads below the head of the screw are exposed. The clamping mechanism should prevent screw rotation. Refer to the ASTM specification if the screw is partially threaded or is too small.
- Drive the specimen at 1-5 rpm in the direction of insertion using an appropriate sized screwdriver bit by applying a torsional force until break. If an axial load is required to maintain the screwdriver bit in the screw head, its value should be recorded.
- Analysis: a) Torsional Offset Yield Strength is determined at 2 degrees offset using the torque versus angle of rotation curve. b) Maximum Torque is determined by the largest value on the torque versus angle of rotation curve. c) Breaking Angle is the point at which torque portion of the curve demonstrates its most rapid descent to total failure.
The embedded video demonstrates the use of an ADMET 81T Vertical Torsion Tester for determining offset yield torque, maximum torque and angle at break according to ASTM F543-A1. The torsion test apparatus is rated for 20Nm and is equipped with ADMET's MTESTQuattro® PC based Torsion Testing Software.
For more information on ADMET's Torsion Systems, contact sales@admet.com or 1-800-667-3220.
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