ASTM F2385-04

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Designation:F2385–04
Standard Test Method for
Determining Femoral Head Penetration into Acetabular
Components of Total Hip Replacement Using Clinical
Radiographs
This standard is issued under the fixed designation F2385; 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 1.10 The use of this standard may involve the operation of
potentially hazardous radiographic equipment and does not
1.1 Thistestmethodprovidesguidanceforthemeasurement
purport to address the safety precautions associated with
of the relative displacement of the femoral head and acetabular
radiography. It is the responsibility of the user of this standard
component that result from wear and deformation occurring at
to define and establish appropriate safety practices. The
the articular interface of a total hip replacement from sequen-
standard does not determine the applicability of regulatory
tial clinical radiographs.
limitations prior to operating radiographic equipment.
1.2 This test method is primarily intended for use in
1.11 This standard does not purport to address all of the
evaluating patients receiving THRs composed of a polyethyl-
safety concerns, if any, associated with its use. It is the
ene acetabular component articulating against a metal or
responsibility of the user of this standard to establish appro-
ceramic femoral head.
priate safety and health practices and determine the applica-
1.3 So-called hard-on-hard articulations such as metal-on-
bility of regulatory limitations prior to use.
metal and ceramic-on-ceramic THRs are not intended to be
directly addressed.
2. Referenced Documents
1.4 This test method will focus on computer assisted com-
2.1 ASTM Standards:
putational methodologies for measuring relative displacements
E177 Practice for Use of the Terms Precision and Bias in
over time but not to the exclusion of other methodologies.
ASTM Test Methods
1.5 This test method describes methods for conducting a
E691 Practice for Conducting an Interlaboratory Study to
radiographic wear/creep study utilizing various computational
Determine the Precision of a Test Method
methods and is not intended to promote or endorse a particular
method.
3. Terminology
1.6 It is not the intent of this test method to provide detailed
3.1 All radiographic terminology is consistent with the
instructions in the use of the various computational methods,
referenced standards, unless otherwise stated.
which is contained in the respective user manuals.
3.2 Definitions:
1.7 It is the intent of this test method to enable comparisons
3.2.1 radiostereometric analysis (RSA)—a method devel-
of relative displacements occurring in groups of patients
oped by Goren Selvik for measuring relative motion between
receiving different formulations of bearing materials. It must
two parts from clinical radiographs (1). This method utilizes
berecognized,however,thattherearemanypossiblevariations
in vivo tantalum beads, an external reference cage, and two
in the in vivo conditions. A single clinical study may not be
x-ray generators which take two exposures simultaneously.
universally representative.
There are several commercially available software/hardware
1.8 This test method is not intended to be a performance
packages for RSA analysis.
standard. It is the responsibility of the user of this test method
3.2.2 markers—tantalum beads 1.0 mm, 0.8 mm, or 0.5 mm
to characterize the safety and effectiveness of the prosthesis
in diameter.
under evaluation.
3.2.2.1 implant markers—in vivo markers placed on the
1.9 The values stated in SI units are to be regarded as the
implant in order to define the implant as a rigid body.
standard, with the exception of angular measurements, which
may be reported in either degrees or radians.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction ofASTM Committee F04 on Medical contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and Surgical Materials and Devices and is the direct responsibility of Subcommittee Standards volume information, refer to the standard’s Document Summary page on
F04.22 on Arthroplasty. the ASTM website.
Current edition approved May 1, 2004. Published May 2004. DOI: 10.1520/ The boldface numbers in parentheses refer to the list of references at the end of
F2385-04. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2385–04
3.2.2.2 cage markers—tantalum beads held in an external measurethecombinedeffectofplasticdeformationandwearat
reference frame used to create a three dimensional coordinate the articular interface which results in three dimensional
system for measuring relative displacements. displacements of the femoral head into the acetabular compo-
3.2.2.3 segment—a three dimensional rigid body defined by nent.
a minimum of three markers.
4.2 This test method addresses the validation of the various
3.2.3 edge detection—method of image analysis used to
computational methods available for measuring the magnitude
determine the two dimensional or three dimensional center
of creep/wear accruing at the articular surface of THRs.
point of a curved surface. Many computational methods of
4.3 This test method addresses the type of radiographic
edge detection exist.
projections needed for an analysis as well as general radio-
3.2.4 coordinate system/axes—three orthogonal axes are
graphic parameters needed for obtaining high quality films.
defined as follows:
4.4 This test method addresses the criterion for evaluating
3.2.4.1 origin—the center of the coordinate system is lo-
clinical radiographs for inclusion in a study.
cated at either the geometric center of the acetabular compo-
4.5 This test method addresses the conversion of radio-
nent segment or the center of a circle defined using the edge of
graphic images to the appropriate digital format needed for the
the acetabular component.
various computer assisted computational methods.
3.2.4.2 X-axis—the positive X-axis is to be directed in the
medial direction independent of which hip is to be studied.
5. Validation
Some software programs correct the sign of this value but the
user must insure that the protocol maintains the convention,
5.1 Aphysical phantom model which is capable of replicat-
(that is, which way is the patient facing).
ing the three dimensional displacement of the femoral head at
3.2.4.3 Y-axis—the positive Y-axis is to be fixed in the
magnitudes of displacements that are expected to occur clini-
superior direction.
cally should be used to validate new software programs,
3.2.4.4 Z-axis—the positive Z-axis is to be fixed in the
modifications to existing programs, and variations to the
posterior direction.
experimental protocol which may effect the results of the
3.2.5 radio pair—one set of RSA radiographs which were
measurements. A recent publication describes such a phantom
taken simultaneously.
and its use (6). Figs. 1 and 2 show an example of a model
3.3 There are a number of computational methods that can
which can be used for this purpose. For comparative purposes,
beusedtomeasurecreep/wearofapolyethylenecomponent.A
the method described by Bragdon et al (6) for calculating
description of a few of the commonly used current methods is
accuracy and precision can be used. Illustrative values for the
given. This is not meant to be at the exclusion of other
accuracyandprecisionasmeasuredbythismethodarelistedin
methods.
the appendix.
3.3.1 Martell method—as this software is informally re-
5.2 To generate data for a precision and bias statement, the
ferred to in reference to its developer Dr. John Martell of
Practice E177 should be followed.
Chicago University, is a semi-automated computer technique
using edge detection and the Hough transformation for the
determination of polyethylene wear. This technique uses se-
quential A/P films for two dimensional analysis and A/P and
lateral sequential films for three dimensional analysis (2).
3.3.2 Polywear method—a software program developed by
Dr. Peter Devane of the Wellington School of Medicine, New
Zealand is a semi-automated computer technique using edge
detection for the determination of polyethylene wear. This
technique uses sequential A/P films for two dimensional
analysis and A/P and lateral sequential films for three dimen-
sional analysis (3).
3.3.3 UmRSA—an RSA software program developed by
Biomedical Innovations AB in Umea Sweden. It utilizes
sequential radio pairs in order to measure relative displace-
ments between two segments or a point relative to a segment.
It utilizes a model based edge matching method for determin-
ing the center of the markers (4).
3.3.4 CMS-RSA—an RSA software program developed at
the University of Leiden, Sweden. It utilizes sequential radio
pairs in order to measure relative displacements between two
segments (5).
4. Significance and Use
4.1 This test method uses clinical radiographs of the hip
FIG. 1 Phantom Model Capable of Moving the Femoral Head by
joint of a patient that has received a total hip replacement to Small Discrete Three Dimensional Displacements
F2385–04
6.2.1 These radiographs can be taken in the supine or
standing position. The method must be consistent throughout
the subsequent examinations.
6.2.2 The radiographic set-up for RSAanalysis requires two
x-ray generators which are discharged nearly simultaneously.
6.2.3 The preferred set-up would use two fixed generators.
6.2.4 A more common set-up utilizes one fixed and one
portable generator.
6.2.5 Thegeneratorsarepositionedhavinga60in.sourceto
plate distance and angled at 40 degrees. The set-up recom-
mended by the individual software manufacturers is to be
followed.
6.2.6 Radiographic settings for the RSA projections focus
on obtaining high contrast between the tantalum markers and
the surrounding bone and metal.This is accomplished by using
high kilovolt settings. These films are not generally used for
clinical evaluation.
NOTE—The displacement mechanism is made of three stages purchased
6.2.7 Atypical radiographic set-up would have an exposure
from Edmund Industrial Optics Catalog.
setting of 150 kv 8-12 maS can be used.
FIG. 2 Medium 2.62 in. Square Linear Translation Stages (xyz)
6.2.8 Manyportablex-rayunitsandsomefixedunitsarenot
capable of operating at 150 kv. In these situations, settings of
125 kv and 12-16 maS can be used.
6. Material
6.3 Conversion of Radiographic Images to Appropriate
...