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 Wed, Jul 21, 2010 @ 03:20 PM
ASTM F2256 describes in detail how to prepare and test tissue adhesives. This standard describes the methods used to compare and characterize different types of adhesives and for manufacturing quality control of the tissue adhesive based medical devices.
Medical professionals are now using tissue adhesives in place of, or in addition to, the standard sutures or staples to close wounds, surgical openings, and other bandage or wound applications. Defining the adhesive strength of these products determines where, how, and when the adhesive can be used in a medical procedure.
Sample preparation for test substrates; frozen or split bovine, porcine, or ovine tissue freshly harvested from the target organ of a domestic animal. Sample preparation guidelines discussed in detail in section 6, 7, and 8. ASTM F2256
Test Procedure
- Sample specimen width 2.5 +-0.1 cm
- Sample specimen length 15 +-0.2cm (2.5 unbonded, 12.5cm bonded)
- 10 specimens - individual tests and results accumulate with a statistical summary. In some cases, more samples may be needed to obtain a more accurate measure of mean strength.
- Condition specimens for 1 hour +-15 min.A)Tissue Adhesive -internal use-37 degrees Celcius in phosphate buffered saline. B)Tissue Adhesive- external use-30 degrees Celcius and 50%+-5% relative humidity. C)For quality control- 23 degrees celcius and 50%+-5% relative humidity.
- Secure the specimen according to the diagram above.
- Pull sample at a constant rate of 250mm/minute until break.
- Plot load vs. displacement and record observation on reason for bond area failure. (ie; adhesive, substrate)
- The specification asks the user to set up the testing profile in a particular way. Using an ADMET Testing System and MTESTQuattro PC based servo control data acquisition, analysis, and reporting software the following profile can be established.
- Specimen geometry- bonded length 12.5cm.
- Specimen ID with auto increment for data file and results file names.
- Grip separation- 2.5cm
- Logging threshold set to 2.5cm displacement.
- Calculate Average Load between extension points- 2.5cm and 22.5cm
- Calculate T-Peel strength- Divide average load (n) by width of specimen (cm)
- Show statistical summary report(high, low, mean, st. dev, range,+-3 sigma) This report is found in a results file compiled of all specimens tested with this profile and meeting the substrate description defined earlier in sample preparation section.
For reference to ASTM D1876 blog post and testing video.
Recommended equipment
Single Column Universal Testing System or Dual Column Universal Testing System equipped with MTESTQuattro, load cell, vise grips and inserts.
Optional Bath fixture available from ADMET in many sizes for Tissue Samples that must remain in solution throughout the testing. Grips are specially coated to maintain integrity in solution.
Contact ADMET 1-800-667-3220 or info@ADMET.com for more information.
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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 Richard Gedney on Mon, Mar 01, 2010 @ 08:09 AM
Materials that adhere living tissues together are being used more frequently in surgical procedures as adjuncts to sutures or as replacements. ASTM F2458 - 05 is a standard test method for determining the comparative wound closure strength of tissue adhesives. With the appropriate substrate, F2458 can also be used in quality control testing of tissue adhesives. This test method can be used to compare adhesives for chance of fatigue, type of failure, and environmental changes.
- A testing machine capable of a constant rate of crosshead movement is required .
- The tensile grips used for holding the test specimen can be either fixed or self-aligning.
- Gripping pressure should be ajustable to prevent damage to the substrate.
- To help prevent specimen slippage in the grips, sandpaper or plastic scrubbing pads should be placed between the substrate and the grip faces.
- For comparative testing fresh or frozen porcine skin graft may be used.
- For application specific testing the tensile grips must prevent substrate slippage or being crushed by the grips. See Sections 6-8 and Appendix X1 for more information of substrate materials; their storage and preparation prior to test.
- Two substrate samples are required for each test specimen. An adhesive butt joint is formed by applying the adhesive to a 1 cm region across the seam between the two substrates. Figure 1 is a depiction of the test sample geometry.
Figure 1 - Depiction of test specimen. Includes two 10 cm long substrates placed end to end. Adhesive should not be applied beyond 0.5 cm either side of butt seam.
Test Procedure
- Condition the test specimens as specified in Section 9.1. After conditioning, the temperature of the samples should be stabilized for at least 15 minutes. Phosphate buffered saline (PBS) must be used to keep the samples moist throught sample preparation and testing.
- Place the specimen in the grips so that the distance from the adhesive butt seam to each grip face is 5 cm. Load the specimen to failure at a constant crosshead speed of 50 mm/min.
- Record the adhesive cure time, maximum force and type of failure.
ADMET ASTM F2458 Testing Machine Solutions
- Two ADMET servo controlled testing machine models suitable for performing ASTM F2458 are the ADMET eXpert 7600 or eXpert 2600 series.
- Each system is offered with manual or pneumatic vise grips.
- Use MTESTQuattro, ADMET's PC Based materials testing system to ensure error free repeatable testing. You will be able to quickly setup and store F2458 test procedures, run tests and generate reports.
- This test may require an environmental chamber with heating and cooling or a bath depending on the type of substrate tested. ADMET offers many different grips, fixtures, accessories, heating and cooling units, and baths to choose from.
Environmental bath w/vise grips pneumatic vise grips
Single and Dual Column Testing Systems from
ADMET.
Other related standards; ASTM F2255, F2256 and F2258.
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