ASTM F2724-08(2014)

4.1 This test method is designed to provide a standardized method to determine the constraint of mobile-bearing knee designs with regards to spin-out and spit-out of the mobile bearing.

4.2 Similar to constraint testing of total knees (see Test Method F1223), it is important to note that the test method does not simulate the soft tissues and laxity of the knee joint, which may be key factors related to the occurrence of spin-out or spit-out.³ For instance, a patient with good soft tissue restraints will perhaps require a lower spin-out/spit-out resistance whereas a patient with major bone loss or destroyed ligamentous structures will likely require an implant with a higher spin-out/spit-out resistance. Therefore, the results from the test should be taken into account along with the condition of the patient’s soft tissues to determine the relative safety for the device.

1.1 This test method is designed to provide a standardized method to determine the dislocation resistance of mobile-bearing knee designs with regard to femoral component disassociation and spin-out/spit-out of the mobile bearing insert.

1.2 Although the methodology described does not replicate all physiological loading conditions, it is a means of in-vitro comparison of mobile bearing knee designs and their ability to resist dislocation of the mobile bearing from the femoral or tibial components under stated test conditions.

1.3 The test method applies only to mobile bearing total knee designs.

1.4 The values stated in SI units are regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.