ASTM F2724-08(2014)
(Test Method)Standard Test Method for Evaluating Mobile Bearing Knee Dislocation
Standard Test Method for Evaluating Mobile Bearing Knee Dislocation
SIGNIFICANCE AND USE
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.
SCOPE
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.
General Information
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F2724 − 08 (Reapproved 2014)
Standard Test Method for
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Evaluating Mobile Bearing Knee Dislocation
This standard is issued under the fixed designation F2724; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 centerline axis, n—a line through the neutral point
perpendicular to the bearing axis and in a plane parallel to the
1.1 This test method is designed to provide a standardized
plane of the flat portion of the inferior articulating surface of
method to determine the dislocation resistance of mobile-
the mobile bearing at 0° posterior tibial slope.
bearing knee designs with regard to femoral component
3.1.3 mobile bearing (insert), n—the component between
disassociation and spin-out/spit-out of the mobile bearing
fixed femoral and tibial knee components with an articulating
insert.
surface on both the inferior and superior sides.
1.2 Although the methodology described does not replicate
3.1.4 neutral point, n—midpoint of the bearing axis.
all physiological loading conditions, it is a means of in-vitro
comparison of mobile bearing knee designs and their ability to
3.1.5 spin-out, n—excessive rotation of the bearing compo-
resist dislocation of the mobile bearing from the femoral or
nent in a rotating platform knee or multi-directional platform
tibial components under stated test conditions.
knee such that there is dislocation between the femoral or tibial
components and the mobile bearing.
1.3 The test method applies only to mobile bearing total
knee designs. 3.1.6 spit-out, n—escape of the bearing component from
beneath the femoral component either anteriorly or posteriorly.
1.4 The values stated in SI units are regarded as standard.
3.1.7 2-axis orthogonal load frame, n—a test machine
The values given in parentheses are mathematical conversions
capable of applying forces and displacements that act at 90° to
to inch-pound units that are provided for information only and
each other.
are not considered standard.
1.5 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
4.1 This test method is designed to provide a standardized
responsibility of the user of this standard to establish appro-
method to determine the constraint of mobile-bearing knee
priate safety and health practices and determine the applica-
designs with regards to spin-out and spit-out of the mobile
bility of regulatory limitations prior to use.
bearing.
2. Referenced Documents
4.2 Similar to constraint testing of total knees (see Test
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Method F1223), it is important to note that the test method
2.1 ASTM Standards:
does not simulate the soft tissues and laxity of the knee joint,
F1223 Test Method for Determination of Total Knee Re-
which may be key factors related to the occurrence of spin-out
placement Constraint
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or spit-out. For instance, a patient with good soft tissue
3. Terminology
restraints will perhaps require a lower spin-out/spit-out resis-
tance whereas a patient with major bone loss or destroyed
3.1 Definitions:
ligamentous structures will likely require an implant with a
3.1.1 bearing axis, n—the line connecting the lowest points
higher spin-out/spit-out resistance. Therefore, the results from
on both the lateral and medial condyles of the superior surface
the test should be taken into account along with the condition
of the mobile bearing.
of the patient’s soft tissues to determine the relative safety for
the device.
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This test method is under the jurisdiction ofASTM Committee F04 on Medical
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
5. Apparatus and Materials
F04.22 on Arthroplasty.
Current edition approved March 15, 2014. Published April 2014. Originally 5.1 Aengineering analysis should be performed on all sizes
approved in 2008. Last previous edition approved in 2008 as F2724 – 08. DOI:
of a knee design to justify a “worst case” size for this test. At
10.1520/F2724-08R14.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Weale, A. E., et al, “In Vitro Evaluation of the Resistance to Dislocation of a
Standards volume information, refer to the standard’s Document Summary page on Meniscal-Bearing Total Knee Prosthesis Between 30° and 90° of Knee Flexion,” J.
the ASTM website. Arthroplasty, 17( 4), 2002, pp. 475–483.
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