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1.1 This practice covers a laboratory-based in vitro method for evaluating the mechanical performance of materials and devices being considered for replacement of the tibio-femoral joint in human knee joint replacement prostheses in mobile bearing knee systems.

1.2 Mobile bearing knee systems permit internal external rotation to take place on one or both articulating surfaces. Some designs place physical limits or stops to the amount of rotation. Other designs may have increases of a resistance force with increases in rotation.

1.3 Although the methodology describes attempts to identify physiologically relevant motions and force conditions, the interpretation of results is limited to an in vitro comparison between mobile bearing knee designs and their ability to maintain the integrity of the rotational stop feature and tibial bearing component under the stated test conditions.

1.4 This practice is only applicable to mobile knee tibial systems with a rotational stop.

1.5 The values stated in SI units are regarded as standard.

1.6 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.

4.1 Fundamental aspects of this practice include the use of dynamic rotational force and motion representative of the human knee joint during an activity of daily living (deep flexion) and the effect of these forces and motions on the design features which stop or limit rotation in a mobile bearing knee design.

4.2 This test is required if rotational stops are designed to limit motion to ±20° or less; or there are other resistances to rotational motion with this ±20° range. In some instances, the rotational displacement could occur in both the inferior and superior interfaces.