1、Designation: F2722 08F2722 15Standard Test Method Practice forEvaluating Mobile Bearing Knee Tibial Baseplate RotationalStops1This standard is issued under the fixed designation F2722; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method practice covers a laboratory-based in vitro method for evaluating the mechanical perfor
3、mance of materialsand devices being considered for replacement of the tibio-femoral joint in human knee joint replacement prostheses in mobilebearing knee systems.1.2 Mobile bearing knee systems permit internal external rotation to take place on one or both articulating surfaces. Somedesigns place p
4、hysical limits or stops to the amount of rotation. Other designs may have increases of a resistance force withincreases in rotation.1.3 Although the methodology describes attempts to identify physiologically relevant motions and force conditions, theinterpretation of results is limited to an in vitr
5、o comparison between mobile bearing knee designs and their ability to maintain theintegrity of the rotational stop feature and tibial bearing component under the stated test conditions.1.4 This test method practice is only applicable to mobile knee tibial systems with a rotational stop.1.5 The value
6、s 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 responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regula
7、torylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F2083 Specification for Knee Replacement ProsthesisF2003 Practice for Accelerated Aging of Ultra-High Molecular Weight Polyethylene after Gamma Irradiation in Air3. Terminology3.1 Definitions:3.1.1 bearing axisthe line connectin
8、g the lowest points on both the lateral and medial condyles of the superior surface of themobile bearing.3.1.2 inferior articulating interfacesany interface in which relative motion occurs between the underside of the mobilebearing component and the tibial tray.3.1.3 mobile bearingthe component betw
9、een fixed femoral and tibial knee components with an articulating surface on boththe inferior and superior sides.3.1.4 mobile bearing knee systema knee prosthesis system, comprised of a tibial component, a mobile bearing component thatcan rotate or rotate and translate relative to the tibial compone
10、nt, and a femoral component.3.1.5 neutral pointmidpoint of the bearing axis.3.1.6 rotational stopa feature that prevents relative rotation between two articulating joint surfaces beyond a specific angleof rotation or creates resistance to rotation beyond a specific angel of rotation.1 This test meth
11、od practice is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility ofSubcommittee F04.22 on Arthroplasty.Current edition approved June 1, 2008Jan. 15, 2015. Published July 2008February 2015 Originally approved in 2008. Last prev
12、ious edition approved in 2008 as F2722-08.DOI: 10.1520/F2722-08.10.1520/F2722-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page
13、on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that use
14、rs consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.7 superior articulating
15、interfacesany interface in which relative motion occurs between the topside of the mobile bearingcomponent and the femoral bearing component.4. Significance and Use4.1 Fundamental aspects of this test method practice include the use of dynamic rotational force and motion representative ofthe human k
16、nee joint during an activity of daily living (deep flexion) and the effect of these forces and motions on the designfeatures 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 to620 or less; or there are other resis
17、tances to rotationalmotion with this620 range. In some instances, the rotational displacement could occur in both the inferior and superior interfaces.5. Apparatus and Materials5.1 Component Configurations:5.1.1 A test construct of the femoral component, mobile bearing component, and tibial tray sho
18、uld be used to provideappropriate interface geometries.5.1.2 The knee joint tibial and femoral components should be assembled and oriented in a manner similar to that in which theywould function in vivo as depicted in Fig. 1. The femoral component is mounted at the maximum flexion angle claimed for
19、thedevice by the manufacturer.5.1.3 The tibial component is mounted at zero slope. This means that the flat portion of the superior tibial surface will beperpendicular to the force axis.5.2 Mechanical Testing Systems:5.2.1 Test ChambersDesign each chamber entirely of noncorrosive materials, such as
20、acrylic plastic or stainless steel, andensure that it is easily removable from the machine for thorough cleaning between tests. Design the chambers such that the bearingsurfaces are immersed in lubricant throughout the test.5.2.2 The system should be capable of maintaining an axial force of 2000 N f
21、orce as illustrated in Fig. 1. (Although this forceis representative of a normal range compressive force, it is mainly intended as a uniform force to keep the components in contactduring the test.)5.2.3 The system should be capable of applying under torque control a peak torque of 14 N-m (2 the peak
22、 torque measuredfrom a telemeterized knee study (1)3) and cycling back to near zero torque in both internal and external rotation directions.3 The boldface numbers in parentheses refer to the list of references at the end of this standard.F2722 1525.2.4 If the rotational stop geometries for internal
23、 and external rotation are non-symmetrical, both the internal and externalrotational stops should be tested. The same sample may be used for both tests if the results of the first test do not cause any damagethat could affect the results of the second test.5.2.5 Rotational Test FrequencyRotate the r
24、elative rotational motion at a nominal rate of 0.5 to 3.0 cycles per second (0.5 to3.0 Hz) per complete cycle to minimize viscoelastic high frequency effects.5.2.6 Cycle CounterInclude with the mechanical testing system a method to monitor and count the number of cycles.5.2.7 LubricantLubricate the
25、specimen by immersion in deionized water, mineral oil, olive oil or other suitable lubricant andmaintained at 37 6 2C.6. Specimen Preparation6.1 The geometry of the parts must be within the specified tolerance ranges of final production designs.6.2 The metallic components should follow the complete
26、manufacturing process (machining, surface treatment, laser marking,passivation, cleaning, and so forth) until the sterilization stage. Because sterilization has no known effect on the mechanicalproperties for metallic components, it is not necessary for these to be sterilized. The polymeric componen
27、ts should be sterilizedin a manner consistent with the clinical use for such devices, as this may affect the mechanical properties of the material.6.3 The ultra-high molecular weight polyethylene (UHMWPE) components should be artificially aged according to PracticeF2003, except when the mechanical p
28、roperties of the UHMWPE have been proven not to be detrimentally affected by the aging,6.4 Because the cold flow of the bearing component depends on its thickness, the thinnest bearing component in the knee systemshould be used.6.5 The tibial bearing size, including thickness, shall be explicitly sp
29、ecified and reported, with a rationale of why it was chosen.It is good practice to also explicitly specify and report the sizes and rationale of all other components of the implant specimensused.7. Procedure7.1 Rigidly mount the femoral component at the maximum flexion angle of the knee as determine
30、d in Specification F2083 tothe compressive force axis. The femoral component should contact the mobile bearing component at the bearing axis to allowrotation about the neutral point.NOTE 1Although in high flexion the femoral component is more posterior on the bearing, such a position would make it d
31、ifficult to rotate the bearingaround the neutral point.FIG. 1 Schematic of Test SetupF2722 1537.2 The tibial base plate articulating surface (or the flat portion thereof) should be mounted perpendicular to the compressiveforce axis.7.3 Mounting of the tibial base plate should not interfere with tibi
32、ofemoral rotation.7.4 Either the femoral component or the tibial base plate component may be articulated, based upon the mechanical testingequipment capabilities.7.5 Place the components in the testing system in zero degrees rotational alignment, add lubricant, apply the axial force, andcommence cyc
33、lic rotational motions.7.6 Apply the 2000 N force and maintain it within 62 %.7.7 Apply a torque of 14 N-m to force the bearing against the rotational stop. Complete the cycle by decreasing the torque toless than 3 % of the peak torque (0.42 N-m). Peak torque should be maintained within 63 %. The to
34、rque is applied around theneutral point of the mobile bearing component on the tibial base plate. In general, the neutral point should be obvious from thedesign of the system. If the choice of the rotational axis used in the test is not the neutral point, the choice of the rotational axisshould be j
35、ustified.7.8 Test LengthDue to the high force and large flexion angle deep squatting scenario simulated by this testing protocol,220 000 cycles shall be used to determine mechanical performance. The number of force cycles should reflect an anticipatedimplant lifetime of 20 years, unless the device h
36、as an alternate expected lifetime. This number of cycles represents approximatelythirty deep squatting occurrences per day for 20 years.7.9 Continue the test until one of the following events occurs:7.9.1 The bearing component fractures or disassociates.7.9.2 The testing machine fails to maintain th
37、e specified control range.7.9.3 The 220 000 cycles test duration is achieved.8. Reporting Results8.1 The test report shall include the following information:8.1.1 Bearing component size, tibial baseplate size, and femoral component size.8.1.2 Bearing component thickness.8.1.3 Bearing component mater
38、ial information.8.1.4 Test frequency.8.1.5 For samples that do not survive 220 000 cycles, the number of cycles completed prior to failure or incipient failure.8.1.6 All samples should be photographed and the physical condition of the samples noted at the end of the test.8.1.7 All samples deemed to
39、not have survived the test should have a descriptive failure mode. Detailed examples include:delamination, disassociation from metal backing, fractures, excessive creep resulting in loss of polymeric material articulation, anderratic motion behavior inconsistent with normal physiological motion.APPE
40、NDIX(Nonmandatory Information)X1. RATIONALEX1.1 Limited testing has been performed on mobile-bearing knees where insert damage of the rotational stop was the focus ofattention. Multi-gait testing has been conducted on AMTI wear simulators where implants were subjected to four gait cycles(walking, ch
41、air descent and rise, stair climbing, and deep squatting) (2). The femoral flexion/extension, rotation, anterior/posteriorposition and tibial internal/external rotations for the deep squat activity were extracted from a gait laboratory subject whoperformed a double leg rise deep squatting activity (
42、3). The damage and deformation of the inserts was observed and examinedon an overall basis, resulting from the combination of the four gait cycles, but not from any specific activity. The insert specimenswere examined for changes in insert/tray motion and dimensions using an optical microscope, back
43、lighting, and dimensionalinspection.X1.2 The rotation/translation stop features were also examined at the completion of testing where approximately 125 000 deepsquat cycles were implemented and showed evidence of slight deformation but no gross damage or failure. Numerous papers haverecently been pu
44、blished looking at axial rotation for normal healthy knees,ACL-deficient knees, and total arthroplasty patients andhave generally found that maximum tibial axial rotations are reduced for ACL-deficient and TKA patients versus normal intactknees (4-8). These studies suggest most patients and activiti
45、es for mobile bearingACL-deficient applications require less than 20F2722 154of axial rotation and validate the decision to not test for devices that allow more than 20 of rotation. Only during deep squattingactivities do internal tibial rotations approach or exceed 20 of rotation. Other recently pu
46、blished studies have specifically focusedon the amount of axial rotation that occurs at the superior tibiofemoral insert surface and the inferior insert surface (base plate toinsert interface) for mobile bearing total knee applications (9-14). Results from these studies suggest that internal rotatio
47、n of thetibial insert relative to the baseplate is small when compared to the overall rotation of the tibiofemoral interface.REFERENCES(1) Taylor, S. J. G., et al, “The Forces in the Distal Femur and the Knee During Walking and OtherActivities Measured by Telemetry,” J. of Arthroplasty, 13, 1998, pp
48、. 428437.(2) Johnson T. S., et al, “Implementation of Multiple Activities of Daily Living for Knee Wear Testing,” Proceedings of the 50th annual OrthopedicResearch Society, San Francisco, CA, 2004.(3) Dyrby, C. O., Masters Thesis, in Department of Bioengineering, U. of Illinois: Chicago, 1998.(4) De
49、nnis, D., et al, “AMulticenterAnalysis ofAxial Femorotibial RotationAfter Total KneeArthroplasty,” 72nd Annual Meeting of AAOS, WashingtonDC, 2005.(5) Dennis, D. A., “In Vivo Determination of Normal and Anterior Cruciate Ligament-Deficient Knee Kinematics,” J. Biomechanics, 38, 2005, pp.241253.(6) Argenson, J. A., et al, “In Vivo Kinematic Evaluation and Design Considerations Related to High Flexion in Total Knee Arthroplasty,” J.Biomechanics, 38, 2005, pp. 277284.(7) Banks, S., et al, “Knee Motions During Maximum Flexion in Fixed and Mobile Bearing Arthro
