A method for testing spinous process plates is described in the standard “PI-76 Standard practice for mechanical characterization of spinous process plates,” developed by PI Medical Implants. Spinous process plates consist of parallel plates that interlock around adjacent spinous processes to stabilize the motion segment for fusion.
The test method described describes static and dynamic tests by specifying the types of loads and the specific methods for applying these loads. The main tests performed to evaluate and characterize them include:
Compression tests are classified into static and dynamic modes according to the test speed. Static tests are usually performed at speeds of less than 1 mm/min, while dynamic tests are performed at speeds of at least 10 mm/min. Static tests are further classified as axial and plane strain compression tests. Axial tests are performed to collect yield strength, ultimate stress, and similar engineering properties used in the design of spinous process plates. Planar tests are performed at high temperature to collect flow properties of metals and alloys used in strain compression, extrusion, and similar manufacturing processes.
Vertebral body implants are tested by performing quasi-static and oscillatory torsion tests in accordance with the standards “ASTM F2077-18 Test methods for intervertebral body fusion devices” and “ASTM F1717-21 Standard test methods for spinal implant constructs on a vertebrectomy model”.
With the help of a torsion fixture, rotational movement and thus a torsional load of up to 50 Nm is possible via the linear movement of a single test actuator. The torsion fixture also applies an axial load defined by variable dead weights and a lever mechanism. The main advantage of the torsion fixture is the ability to test multiple axes with a single closed-loop controlled linear actuator. The fixture is designed for static and alternating torsion tests. The rotation angle for static tests is a maximum of 120 degrees and for oscillatory tests plus/minus 20 degrees. The backlash-free guide rails can grip specimens of different lengths and test them according to the relevant ASTM standards.
Constrained or static plates are locking screw interfaces that allow single cortex fixation without screw pullout. Dynamic or semiconstrained plates have been developed that allow axial placement to accommodate potential biologic or mechanical shortening of the anterior support graft.
Anterior cervical plating provides stabilization of the cervical spine. Theoretical advantages of plate fixation include improved initial stability, reduced complications from bone graft dislocation, end plate fracture, and late kyphotic collapse. Modern plates have screw-capture capacity, thus preventing loosening, and require only unilateral screw purchase. Plate systems may be static or dynamic. Static plates have a rigid connection between the screw and plate and do not allow movement during healing. Dynamic plates allow changes in plate position to accommodate changes in the interbody graft that occur after implantation.
The standard foam static tensile test is a test method used to evaluate the axial tensile strength of orthopedic bone screws.
Briefly, spinous process plates are a single-level, posterior, pedicle-free, supplemental fixation device designed for use in the lumbar spine as an adjunct to fusion in skeletally mature patients.
Among the numerous testing, measurement, analysis and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the “PI-76 Standard application for mechanical characterization of spinous process plates” standard with its trained and expert staff and advanced technological equipment.
To get an appointment, to get more detailed information or to request an evaluation, you can ask us to fill in our form and reach you.
