ASTM F1223: Determination of Total Knee Replacement Constraint
Patients who require total knee replacements have specific sets of needs that a prosthetic device must meet. ASTM F1223 lays out standard testing methods that provide physicians with a database of product functionality capabilities that informs their decision-making in selecting the correct prosthetic in a total knee replacement.
The constraint of a total knee replacement is an essential determinant in device selection, as some patients may have in-tact soft tissue that requires a prosthesis with lesser constraints. In contrast, other patients have destroyed ligamentous structures or suffered significant bone loss in relevant regions that warrant a total knee replacement with a higher degree of constraint. The patient’s proper matching to a functional restorative total knee replacement prosthetic requires a physician’s empirical rationale, as established through ASTM F1223 testing protocols.
ASTM F1223 testing is designed to reveal the device’s characteristics that can influence a physician’s clinical decision making. Within ASTM F1223 guidelines, the testing methodology to be used to quantify total knee replacement constraint in adherence to motion delineation by the prosthetic’s articular design under loading conditions in an in vitro testing environment. ASTM F1223 tests geometrical design factors rather than causing deformation or introducing viscoelastic effects. Since this is not a wear test, the primary aim is to produce data and metrics suited for comparability to other devices.
Constraint describes the inability of a total knee replacement to displace further in a specific direction in a set of loading conditions and is the main focus in ASTM F1223 testing. Constraint determinations apply to mediolateral shear, rotary laxity, valgus-varus rotation, anteroposterior draw, and distraction. ASTM F1223 further specifies geometrical parameter identification of the prosthetic’s contacting surfaces that influence this motion.
ASTM F1223 Testing
Total knee replacement specimens used for testing must be “standard” or “medium” sized, as it is an egalitarian sizing that represents performance under loading regimes. Among a set of assessments is the distraction test, during which the movable component is rigidly set to move only in directions that trigger or facilitate typical distraction mechanics. The valgus-varus test is performed to test the tibial and femoral components of the total knee replacement device. This is assessed by fixing the tibial component in place, while the femoral component can freely translate mediolaterally and anterior posteriorly. Other tests that the device undergoes include an anteroposterior draw test, a mediolateral shear test, and a rotary laxity test.
The importance of standardization and uniformity throughout the testing process is crucial, as it aims to provide comparable data extracted in similar environments. The test method provided by ASTM F1223 does not contradict the three levels of constraint stipulated by the FDA. The loads that are chosen give a relative comparison of devices—they do not indicate anything related to physiological loads.
Working with Empirical Technologies Corp.
If you have a total knee replacement prototype that needs to undergo ASTM F1223 testing, Empirical Technologies Corp is prepared to assist with the process. Our team of experts knows that test method F1223 must sometimes be modified for mobile-bearing knees to characterize constraint at the superior bearing surface. Degrees of femoral constraint are introduced to ensure mobile-bearing function. Whether your prototype falls into this category or requires standard ASTM F1223 testing, Empirical Technologies Corp has the resources and knowledge necessary to provide meticulous total knee replacement testing.
With trusted experience in the field, we have helped countless individuals and businesses through the process of device testing and can provide sound recommendations for alterations should there be any faulty aspects. Contact us today to request an estimate for ASTM F1223 testing.