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.