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 Wed, Aug 11, 2010 @ 11:06 AM
Spinal Implants and Intervertebral Fusion Devices are tested according to several ASTM standards. ASTM F2267 is intended to provide a basis for the mechanical comparison among past, present and future non-biologic intervertebral body fusion devices. These, sometimes hollow, devices are inserted to promote arthrodesis(fusion) at a given spinal motion segment. Construct are governed by ASTM F1717. The mechanical tests are conducted using simplified loading schemes and do not attempt to mimic the complex loads of the spine. An simple outline of the test procedures is as follows:
Axial Compression SubsidenceTest - Metallic Blocks are used to determine stiffness of the device. Polyurethane Blocks are used to determine the likelihood of the part collapsing on itself. Device is secured between 2 blocks.
Stiffness procedure-25mm/min until functional or mechanical failure is obtained.
Subsidence procedure-0.1mm/sec until functional or mechanical failure is obtained.
Both procedures -plot Load vs. Displacement.
Yield Displacement, Stiffness, Yield Load or Moment, Ultimate Displacement, and Ultimate Load or Moment are to be recorded.
Sampling-
- 5 samples,
- polyethylene blocks(1 test) and Metallic blocks(can be reused) used for securing the specimen
- Push rod (38cm from center of spherical surface)
- Inferior sphere holds polyurethane block and is fixed to prevent movement.
- Superior fixture connects to pushrod by minimal friction sphere joint.
Determine Kp by Kp=Ks*Kd/(Kd-Ks)
Kp- Stiffness of Polyurethane Block
Kd-Stiffness of Intervertebral Body Fusion Device
Ks-Stiffness of System
ADMET eXpert 2610 5kN or 10kN - Tension/Compression or Biaxial (shown above) Testing System equipped with MTESTQuattro controller for static tests. System is shown with a multi axis load cell capable of measuring Fx, Fy, Fz and Mz.
Full version of ASTM F2267
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Posted by Debbi Cohen on Tue, Aug 10, 2010 @ 01:46 PM
ASTM F2077-03 is a standard test method for static and dynamic testing of intervertebral body fusion device assemblies. This test method will provide information to compare the mechanical characteristics of different assemblies for different spinal locations and various methods of inserting these assemblies. This standard focuses on all aspects of the spine; cervical, thoracic, and lumber.
This blog post is a quick summary of the full specification. For the full specification details. www.ASTM.org 
There are several types of tests performed for ASTM F2077-03; Static and Dynamic Tests.
Static Tests
- Axial Compression Test- Inline Stainless Steel Test Blocks, compress at a rate of 25mm/minute until failure.
- Compression Shear Test-Inferior fixture designed to orient the initial position of the intervertebral device Z axis at 45 degrees flexion relative to the push rod's axis. Pull at rate of 25mm/minute until failure.
- Torsion Test- Inline, Pushrod connected to superior fixture by a spherical gimbal mechanism, Twist at a rate of 60 degrees/minute until failure. Compressive preloads of 100N, 300N, and 500N are required for this test.
ANALYSIS
- Record Load vs. Displacement or Torque vs. Angle
- Yield Displacement/Angle
- Stiffness
- Yield Load/Torque
- Ultimate Display
- Ultimate Load/Torque
Dynamic / Fatigue Tests- Polyacetal Test Blocks with appropriate matching geometry to Intervertebral Body Fusion Device Assembly.
- Need at least six data points- Max loads for initial fatigue tests are 25%, 50%, 75% of Ultimate Static load determined above.
- Plot semi log- load/torque vs. number of cycles to failure
- Max runout load/torque is determined.
- R-Value of 10 should be used for axial compression & compression shear tests. R value of -1 for Torsion Tests.
- Frequency <=10Hz according to Index X1.9 ( see specification full listing at www.ASTM.org)
ADMET recommends our eXpert 2600 series Biaxial Testing System equipped with our PC based, MTESTQuattro control software for ASTM F2077 testing. Custom fixtures available upon request. All ADMET testing systems come with free lifetime technical support and free startup online training. 1-800-667-3220 for more information and to receive a quote.
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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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