1、Designation: F 2722 08Standard Test Method forEvaluating Mobile Bearing Knee Tibial Baseplate RotationalStops1This standard is issued under the fixed designation F 2722; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 covers a laboratory-based in vitromethod for evaluating the mechanical performance of materialsand dev
3、ices being considered for replacement of the tibio-femoral joint in human knee joint replacement prostheses inmobile bearing knee systems.1.2 Mobile bearing knee systems permit internal externalrotation to take place on one or both articulating surfaces.Some designs place physical limits or stops to
4、 the amount ofrotation. Other designs may have increases of a resistance forcewith increases in rotation.1.3 Although the methodology describes attempts to iden-tify physiologically relevant motions and force conditions, theinterpretation of results is limited to an in vitro comparisonbetween mobile
5、 bearing knee designs and their ability tomaintain the integrity of the rotational stop feature and tibialbearing component under the stated test conditions.1.4 This test method is only applicable to mobile knee tibialsystems with a rotational stop.1.5 The values stated in SI units are regarded as s
6、tandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Refe
7、renced Documents2.1 ASTM Standards:2F 2083 Specification for Total Knee ProsthesisF 2003 Practice for Accelerated Aging of Ultra-High Mo-lecular Weight Polyethylene after Gamma Irradiation inAir3. Terminology3.1 Definitions:3.1.1 bearing axisthe line connecting the lowest points onboth the lateral a
8、nd medial condyles of the superior surface ofthe mobile bearing.3.1.2 inferior articulating interfacesany interface inwhich relative motion occurs between the underside of themobile bearing component and the tibial tray.3.1.3 mobile bearingthe component between fixed femo-ral and tibial knee compone
9、nts with an articulating surface onboth the inferior and superior sides.3.1.4 mobile bearing knee systema knee prosthesis sys-tem, comprised of a tibial component, a mobile bearingcomponent that can rotate or rotate and translate relative to thetibial component, and a femoral component.3.1.5 neutral
10、 pointmidpoint of the bearing axis.3.1.6 rotational stopa feature that prevents relative rota-tion between two articulating joint surfaces beyond a specificangle of rotation or creates resistance to rotation beyond aspecific angel of rotation.3.1.7 superior articulating interfacesany interface inwhi
11、ch relative motion occurs between the topside of the mobilebearing component and the femoral bearing component.4. Significance and Use4.1 Fundamental aspects of this test method include the useof dynamic rotational force and motion representative of thehuman knee joint during an activity of daily li
12、ving (deepflexion) and the effect of these forces and motions on thedesign features which stop or limit rotation in a mobile bearingknee design.4.2 This test is required if rotational stops are designed tolimit motion to 620 or less; or there are other resistances torotational motion with this 620 r
13、ange. In some instances, therotational displacement could occur in both the inferior andsuperior interfaces.5. Apparatus and Materials5.1 Component Configurations:1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsi
14、bility of SubcommitteeF04.22 on Arthroplasty.Current edition approved June 1, 2008. Published July 2008.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standard
15、s Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.1 A test construct of the femoral component, mobilebearing component, and tibial tray should be used to provideappropriate interface geome
16、tries.5.1.2 The knee joint tibial and femoral components shouldbe assembled and oriented in a manner similar to that in whichthey would function in vivo as depicted in Fig. 1. The femoralcomponent is mounted at the maximum flexion angle claimedfor the device by the manufacturer.5.1.3 The tibial comp
17、onent is mounted at zero slope. Thismeans 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 ofnoncorrosive materials, such as acrylic plastic or stainless steel,and ensure that it
18、 is easily removable from the machine forthorough cleaning between tests. Design the chambers suchthat the bearing surfaces are immersed in lubricant throughoutthe test.5.2.2 The system should be capable of maintaining an axialforce of 2000 N force as illustrated in Fig. 1. (Although thisforce is re
19、presentative of a normal range compressive force, itis mainly intended as a uniform force to keep the componentsin contact during the test.)5.2.3 The system should be capable of applying undertorque control a peak torque of 14 N-m (23 the peak torquemeasured from a telemeterized knee study (1)3) and
20、 cyclingback to near zero torque in both internal and external rotationdirections.5.2.4 If the rotational stop geometries for internal andexternal rotation are non-symmetrical, both the internal andexternal rotational stops should be tested. The same samplemay be used for both tests if the results o
21、f the first test do notcause any damage that could affect the results of the secondtest.5.2.5 Rotational Test FrequencyRotate the relative rota-tional motion at a nominal rate of 0.5 to 3.0 cycles per second(0.5 to 3.0 Hz) per complete cycle to minimize viscoelastichigh frequency effects.5.2.6 Cycle
22、 CounterInclude with the mechanical testingsystem a method to monitor and count the number of cycles.5.2.7 LubricantLubricate the specimen by immersion indeionized water, mineral oil, olive oil or other suitable lubri-cant and maintained at 37 6 2C.6. Specimen Preparation6.1 The geometry of the part
23、s must be within the specifiedtolerance ranges of final production designs.6.2 The metallic components should follow the completemanufacturing process (machining, surface treatment, lasermarking, passivation, cleaning, and so forth) until the steril-ization stage. Because sterilization has no known
24、effect on themechanical properties for metallic components, it is not nec-essary for these to be sterilized. The polymeric componentsshould be sterilized in a manner consistent with the clinical usefor such devices, as this may affect the mechanical propertiesof the material.6.3 The ultra-high molec
25、ular weight polyethylene (UHM-WPE) components should be artificially aged according toPractice F 2003, except when the mechanical properties of theUHMWPE have been proven not to be detrimentally affectedby the aging,6.4 Because the cold flow of the bearing component de-pends on its thickness, the th
26、innest bearing component in theknee system should be used.7. Procedure7.1 Rigidly mount the femoral component at the maximumflexion angle of the knee as determined in Specification F 2083to the compressive force axis. The femoral component shouldcontact the mobile bearing component at the bearing ax
27、is toallow rotation about the neutral point.NOTE 1Although in high flexion the femoral component is moreposterior on the bearing, such a position would make it difficult to rotatethe bearing around the neutral point.7.2 The tibial base plate articulating surface (or the flatportion thereof) should b
28、e mounted perpendicular to thecompressive force axis.7.3 Mounting of the tibial base plate should not interferewith tibiofemoral rotation.7.4 Either the femoral component or the tibial base platecomponent may be articulated, based upon the mechanicaltesting equipment capabilities.7.5 Place the compo
29、nents in the testing system in zerodegrees rotational alignment, add lubricant, apply the axialforce, and commence cyclic 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 againstthe rotational stop. Complete the cycle by decre
30、asing thetorque to less than 3 % of the peak torque (0.42 N-m). Peak3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.FIG. 1 Schematic of Test SetupF2722082torque should be maintained within 63 %. The torque isapplied around the neutral point of the mobi
31、le bearing compo-nent on the tibial base plate. In general, the neutral point shouldbe obvious from the design of the system. If the choice of therotational axis used in the test is not the neutral point, thechoice of the rotational axis should be justified.7.8 Test LengthDue to the high force and l
32、arge flexionangle deep squatting scenario simulated by this testing proto-col, 220 000 cycles shall be used to determine mechanicalperformance. The number of force cycles should reflect ananticipated implant lifetime of 20 years, unless the device hasan alternate expected lifetime. This number of cy
33、cles repre-sents approximately thirty deep squatting occurrences per dayfor 20 years.7.9 Continue the test until one of the following eventsoccurs:7.9.1 The bearing component fractures or disassociates.7.9.2 The testing machine fails to maintain the specifiedcontrol range.7.9.3 The 220 000 cycles te
34、st duration is achieved.8. Reporting Results8.1 The test report shall include the following information:8.1.1 Bearing component size, tibial baseplate size, andfemoral component size.8.1.2 Bearing component thickness.8.1.3 Bearing component material information.8.1.4 Test frequency.8.1.5 For samples
35、 that do not survive 220 000 cycles, thenumber of cycles completed prior to failure or incipient failure.8.1.6 All samples should be photographed and the physicalcondition of the samples noted at the end of the test.8.1.7 All samples deemed to not have survived the testshould have a descriptive fail
36、ure mode. Detailed examplesinclude: delamination, disassociation from metal backing,fractures, excessive creep resulting in loss of polymeric mate-rial articulation, and erratic motion behavior inconsistent withnormal physiological motion.APPENDIX(Nonmandatory Information)X1. RATIONALEX1.1 Limited t
37、esting has been performed on mobile-bearing knees where insert damage of the rotational stop wasthe focus of attention. Multi-gait testing has been conducted onAMTI wear simulators where implants were subjected to fourgait cycles (walking, chair descent and rise, stair climbing, anddeep squatting) (
38、2). The femoral flexion/extension, rotation,anterior/posterior position and tibial internal/external rotationsfor the deep squat activity were extracted from a gait laboratorysubject who performed a double leg rise deep squatting activity(3). The damage and deformation of the inserts was observedand
39、 examined on an overall basis, resulting from the combi-nation of the four gait cycles, but not from any specific activity.The insert specimens were examined for changes in insert/traymotion and dimensions using an optical microscope, backlight-ing, and dimensional inspection.X1.2 The rotation/trans
40、lation stop features were also exam-ined at the completion of testing where approximately 125 000deep squat cycles were implemented and showed evidence ofslight deformation but no gross damage or failure. Numerouspapers have recently been published looking at axial rotationfor normal healthy knees,
41、ACL-deficient knees, and totalarthroplasty patients and have generally found that maximumtibial axial rotations are reduced for ACL-deficient and TKApatients versus normal intact knees (4-8). These studies suggestmost patients and activities for mobile bearing ACL-deficientapplications require less
42、than 20 of axial rotation and validatethe decision to not test for devices that allow more than 20 ofrotation. Only during deep squatting activities do internal tibialrotations approach or exceed 20 of rotation. Other recentlypublished studies have specifically focused on the amount ofaxial rotation
43、 that occurs at the superior tibiofemoral insertsurface and the inferior insert surface (base plate to insertinterface) for mobile bearing total knee applications (9-14).Results from these studies suggest that internal rotation of thetibial insert relative to the baseplate is small when compared tot
44、he overall rotation of the tibiofemoral interface.F2722083REFERENCES(1) Taylor, S. J. G., et al, “The Forces in the Distal Femur and the KneeDuring Walking and Other Activities Measured by Telemetry,” J. ofArthroplasty, 13, 1998, pp. 428437.(2) Johnson T. S., et al, “Implementation of Multiple Activ
45、ities of DailyLiving for Knee Wear Testing,” Proceedings of the 50th annualOrthopedic Research Society, San Francisco, CA, 2004.(3) Dyrby, C. O., Masters Thesis, in Department of Bioengineering, U. ofIllinois: Chicago, 1998.(4) Dennis, D., et al, “A Multicenter Analysis of Axial FemorotibialRotation
46、 After Total Knee Arthroplasty,” 72nd Annual Meeting ofAAOS, Washington DC, 2005.(5) Dennis, D. A., “In Vivo Determination of Normal and AnteriorCruciate Ligament-Deficient Knee Kinematics,” J. Biomechanics, 38,2005, pp. 241253.(6) Argenson, J. A., et al, “In Vivo Kinematic Evaluation and DesignCons
47、iderations Related to High Flexion in Total KneeArthroplasty,” J.Biomechanics, 38, 2005, pp. 277284.(7) Banks, S., et al, “Knee Motions During Maximum Flexion in Fixedand Mobile Bearing Arthroplasties,” CORR, 410, 2003, pp. 131138.(8) Watanabe, T., et al, “In Vivo Kinematics of Mobile-Bearing KneeAr
48、throplasty in Deep Knee Bending Motion,” J. Biomechanics, 22,2004, pp. 10441049.(9) Fantozzi, S., et al, “Dynamic In-Vivo Tibio-Femoral and BearingMotions in Mobile Bearing Knee Arthroplasty,” Knee Surg. SportsTrauma Arthro., 12, 2004, pp. 144151.(10) Komistek, R. D., et al, “Mobile Bearing TKA: Do
49、PolyethyleneBearings Rotate and Translate,” 72nd Annual Meeting of AAOS,Washington DC, 2005.(11) Fufii, J., et al, “Tibial Rotation Alignment Analysis at Deep Flexionon Post-Operative Patients of TKA,” Unpublished manuscript, Hi-roshima Rehabilitation Center, Orthopaedic Department, Aichi Medi-cal University.(12) Garling, E. H., et al, “Limited Motion of the Mobile Bearing in aRotating Platform Total Knee Prosthesis,” Unpublished manuscript,2005.(13) Otto, J. K., et al, “Mobility and Contact Mechanics of a RotatingPlatform Total Knee Replacement,” CORR, 392, 2
