The standard “ASTM F2028-17 Standard test methods for dynamic evaluation of glenoid loosening or separation” developed by the American Society for Testing and Materials (ASTM) describes test methods for measuring the extent to which the prosthetic anatomic glenoid component rocks or rotates following cyclic displacement of the humeral head to the opposing glenoid edges, such as the superior-inferior or anteroposterior edges. The motion is measured by the tensile displacement opposite each loaded edge after dynamic rocking. Similarly, these test methods measure the extent to which the prosthetic reverse glenoid component rocks or rotates following cyclic articulation with the matching humeral liner. The motion is measured by the magnitude of displacement measured before and after cyclic loading.
The same setup can be used to test the locking mechanisms of modular glenoid components, such as dissociation of both anatomic and reverse shoulder components.
These test methods cover shoulder replacement designs that include monolithic or modular glenoid components for cemented fixation and reverse glenoid components for cementless fixation.
When performing the test, the prosthetic glenoid component is fixed to a bone substitute with bone cement using normal surgical technique. Subluxation translation is determined experimentally on the additional components. This is accomplished by applying an axial load perpendicular to the glenoid and then using an axial jig to translate the humeral head parallel to the glenoid plane until it encounters peak shear load. This is accomplished in both directions corresponding to the intended swing direction (e.g., superior-inferior, anteroposterior, or an alternating angle).
The marginal displacements of the glenoid are measured before translation: a specific axial load is first applied perpendicular to the glenoid, then the marginal displacements are measured with the humeral head in three positions: at the glenoid origin and positioned at 90 percent of the subluxation translation, as defined in the standard in both directions (translation to 90 percent of the subluxation load is acceptable, but impractical due to large displacements, high speeds and deformable polyethylene).
The humeral head is cycled to 90 percent of the subluxation distance for a fixed number of cycles. Edge displacements are repeated after cycles or measured continuously during the cycle.
This test method aims to investigate the resistance of the glenoid component to loosening. Glenoid loosening is the most common clinical complication in total shoulder arthroplasty. The method assumes that loosening occurs due to edge loading, commonly referred to as the rocking horse phenomenon.
This testing method can be used both to identify potential problems and to compare design specifications. Factors affecting loosening performance include joint geometry, flange geometry, materials, fixation design, bone quality, and surgical technique.
The test apparatus shall be configured so that an axial force perpendicular to the plane of the glenoid and a shear force parallel to the plane of the glenoid are applied. The figure given in the standard shows the axial force horizontal and the shear force vertical, but this arrangement may be reversed.
A bone substitute that represents the strength of glenoid cancellous bone should be used. If polyurethane foam is used, it should meet ASTM F1839-08.
The glenoid and humeral head should be enclosed in a chamber filled with water heated to 37 plus/minus 2 degrees, at least for the dynamic portion of the test.
An instrument is required to measure axial load, shear load, shear translation, and glenoid edge displacements.
Tests are performed on mechanical or hydraulic load frames of adequate load capacity and must meet the criteria of the ASTM E4-21 standard.
Among the numerous testing, measurement, analysis and evaluation studies that our organization has provided for businesses in various sectors, it also provides testing services defined in the "ASTM F2028-17 Standard test methods for dynamic evaluation of glenoid loosening or separation" 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.
