1、Designation: F2385 15Standard Practice forDetermining Femoral Head Penetration into AcetabularComponents of Total Hip Replacement Using ClinicalRadiographs1This standard is issued under the fixed designation F2385; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, 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 practice provides guidance for the measurement ofthe relative displac
3、ement of the femoral head and acetabularcomponent that result from wear and deformation occurring atthe articular interface of a total hip replacement from sequen-tial clinical radiographs.1.2 This practice is primarily intended for use in evaluatingpatients receiving THRs composed of a polyethylene
4、 acetabu-lar component articulating against a metal or ceramic femoralhead.1.3 So-called hard-on-hard articulations such as metal-on-metal and ceramic-on-ceramic THRs are not intended to bedirectly addressed.1.4 This practice will focus on computer assisted computa-tional methodologies for measuring
5、 relative displacementsover time but not to the exclusion of other methodologies.1.5 This practice describes methods for conducting a radio-graphic wear/creep study utilizing various computational meth-ods and is not intended to promote or endorse a particularmethod.1.6 It is not the intent of this
6、practice to provide detailedinstructions in the use of the various computational methods,which is contained in the respective user manuals.1.7 It is the intent of this practice to enable comparisons ofrelative displacements occurring in groups of patients receivingdifferent formulations of bearing m
7、aterials. It must berecognized, however, that there are many possible variations inthe in vivo conditions. A single clinical study may not beuniversally representative.1.8 This practice is not intended to be a performancestandard. It is the responsibility of the user of this practice tocharacterize
8、the safety and effectiveness of the prosthesis underevaluation.1.9 The values stated in SI units are to be regarded as thestandard, with the exception of angular measurements, whichmay be reported in either degrees or radians. Additionally,pixel density may also be reported in imperial units.1.10 Th
9、e use of this standard may involve the operation ofpotentially hazardous radiographic equipment and does notpurport to address the safety precautions associated withradiography. It is the responsibility of the user of this standardto define and establish appropriate safety practices. Thestandard doe
10、s not determine the applicability of regulatorylimitations prior to operating radiographic equipment.1.11 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 he
11、alth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3
12、. Terminology3.1 All radiographic terminology is consistent with thereferenced standards, unless otherwise stated.3.2 Definitions:3.2.1 radiostereometric analysis (RSA)a method devel-oped by Goren Selvik for measuring relative motion betweentwo parts from clinical radiographs (1).3This method utiliz
13、esin vivo tantalum beads, an external reference cage, and twox-ray generators which take two exposures simultaneously.1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Curr
14、ent edition approved Nov. 1, 2015. Published December 2015. Originallyapproved in 2004. Last previous edition approved in 2010 as F2385 04(2010).DOI: 10.1520/F2385-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual
15、Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959
16、. United States1There are several commercially available software/hardwarepackages for RSA analysis.3.2.2 markerstantalum beads 1.0 mm, 0.8 mm, or 0.5 mmin diameter.3.2.2.1 implant markersin vivo markers placed on theimplant in order to define the implant as a rigid body.3.2.2.2 cage markerstantalum
17、 beads held in an externalreference frame used to create a three dimensional coordinatesystem for measuring relative displacements.3.2.2.3 segmenta three dimensional rigid body defined bya minimum of three markers.3.2.3 edge detectionmethod of image analysis used todetermine the two dimensional or t
18、hree dimensional centerpoint of a curved surface. Many computational methods ofedge detection exist.3.2.4 coordinate system/axesthree orthogonal axes aredefined as follows:3.2.4.1 originthe center of the coordinate system is lo-cated at either the geometric center of the acetabular compo-nent segmen
19、t or the center of a circle defined using the edge ofthe acetabular component.3.2.4.2 X-axisthe positive X-axis is to be directed in themedial direction independent of which hip is to be studied.Some software programs correct the sign of this value but theuser must insure that the protocol maintains
20、 the convention,(that is, which way is the patient facing).3.2.4.3 Y-axisthe positive Y-axis is to be fixed in thesuperior direction.3.2.4.4 Z-axisthe positive Z-axis is to be fixed in theposterior direction.3.2.5 radio pairone set of RSA radiographs which weretaken simultaneously.3.3 There are a nu
21、mber of computational methods that canbe used to measure creep/wear of a polyethylene component.Adescription of a few of the commonly used current methods isgiven. This is not meant to be at the exclusion of othermethods.3.3.1 Martell methodas this software is informally re-ferred to in reference to
22、 its developer Dr. John Martell ofChicago University, is a semi-automated computer techniqueusing edge detection and the Hough transformation for thedetermination of polyethylene wear. This technique uses se-quential A/P films for two dimensional analysis and A/P andlateral sequential films for thre
23、e dimensional analysis (2).3.3.2 Polywear methoda software program developed byDr. Peter Devane of the Wellington School of Medicine, NewZealand is a semi-automated computer technique using edgedetection for the determination of polyethylene wear. Thistechnique uses sequential A/P films for two dime
24、nsionalanalysis and A/P and lateral sequential films for three dimen-sional analysis (3).3.3.3 UmRSAan RSA software program developed byBiomedical Innovations AB in Umea Sweden. It utilizessequential radio pairs in order to measure relative displace-ments between two segments or a point relative to
25、a segment.It utilizes a model based edge matching method for determin-ing the center of the markers (4).3.3.4 CMS-RSAan RSA software program developed atthe University of Leiden, Sweden. It utilizes sequential radiopairs in order to measure relative displacements between twosegments (5).4. Significa
26、nce and Use4.1 This practice uses clinical radiographs of the hip joint ofa patient that has received a total hip replacement to measurethe combined effect of plastic deformation and wear at thearticular interface which results in three dimensional displace-ments of the femoral head into the acetabu
27、lar component.4.2 This practice addresses the validation of the variouscomputational methods available for measuring the magnitudeof creep/wear accruing at the articular surface of THRs.4.3 This practice addresses the type of radiographic projec-tions needed for an analysis as well as general radiog
28、raphicparameters needed for obtaining high quality films.4.4 This practice addresses the criterion for evaluatingclinical radiographs for inclusion in a study.4.5 This practice addresses the conversion of radiographicimages to the appropriate digital format needed for the variouscomputer assisted co
29、mputational methods.5. Validation5.1 A physical phantom model which is capable of replicat-ing the three dimensional displacement of the femoral head atmagnitudes of displacements that are expected to occur clini-cally should be used to validate new software programs,modifications to existing progra
30、ms, and variations to theexperimental protocol which may affect the results of themeasurements. A recent publication describes such a phantomand its use (6). Figs. 1 and 2 show an example of a modelwhich can be used for this purpose. For comparative purposes,the method described by Bragdon et al (6)
31、 for calculatingaccuracy and precision can be used. Illustrative values for theaccuracy and precision as measured by this method are listed inthe appendix.5.2 To generate data for a precision and bias statement, thePractice E177 should be followed.6. Material6.1 Non-RSA Methods of Obtaining Clinical
32、 Radiographsfor Measuring Femoral Head Penetration:6.1.1 These methods utilize an Anterior/Posterior (A/P) anda cross-table lateral projection of the pelvis. TheA/P projectionis used for measuring two dimensional penetration vector. Thecross-table lateral is used to determine the magnitude anddirect
33、ion of the three dimensional penetration vector.6.1.2 These radiographs are typically taken in the supineposition. However, the A/P projections can be obtained fromthe standing position. The method must be consistent through-out the subsequent examinations.6.1.3 The A/P projection is to be pubic cen
34、tered includingboth hips, typically taken using a 14 by 17 film or target size.F2385 152As a general rule, having the top of the iliac crest and the lessertrochanter of the femur visible results in a proper radiographicprojection.6.1.3.1 Atypical radiographic set-up would have a source toplate dista
35、nce of 101.6 cm (40 in.) and an exposure setting of80 kV 25-30 mA-s.6.1.4 The cross-table lateral is obtained in the supineposition.6.1.4.1 Atypical radiographic set-up would have a source toplate distance of 101.6 cm (40 in.) and an exposure setting of80 kV 25-30 mA-s.6.1.5 Some non-RSA methods hav
36、e been validated for theuse of ninety degree standing oblique radiographs of the hip.6.1.5.1 Amethod of accurately and reproducibly positioningthe patient for forty five degree oblique projections is needed.One method, using a positioning chariot, has been described.Other methods could be employed f
37、or this purpose.6.1.5.2 Atypical radiographic set-up would have a source toplate distance of 101.6 cm (40 in.) and an exposure setting of85 kV 40-50 mA-s.6.2 RSA Method of Obtaining Clinical Radiographs forMeasuring Femoral Head Penetration:6.2.1 These radiographs can be taken in the supine orstandi
38、ng position. The method must be consistent throughoutthe subsequent examinations.6.2.2 The radiographic set-up for RSAanalysis requires twox-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 uses one fixed a
39、nd oneportable generator.6.2.5 The generators are positioned having a 152.4 cm (60in.) source to plate distance and angled at 40 degrees. Theset-up recommended by the individual software manufacturersis to be followed.6.2.6 Radiographic settings for the RSA projections focuson obtaining high contras
40、t between the tantalum markers andthe surrounding bone and metal. This is accomplished by usinghigh voltage settings. These films are not generally used forclinical evaluation.6.2.7 A typical radiographic set-up would have an exposuresetting of 150 kV 8-12 mA-s.6.2.8 Many portable x-ray units and so
41、me fixed units are notcapable of operating at 150 kV. In these situations, settings of125 kV and 12-16 mA-s can be used.6.3 Conversion of Radiographic Images to AppropriateDigital Format:6.3.1 Scanning of Plain Radiographic Films:6.3.1.1 Several flat bed scanners have been validated bydifferent soft
42、ware developers for use in converting a plainradiograph into a digital image. Recommendations of thesoftware developer should be followed.6.3.1.2 Roller scanners, which feed multiple pages into thescanner, shall not be used.6.3.1.3 Non-RSA films are to be scanned at a resolution of150 dpi at a grays
43、cale resolution of 8 bit and saved in a TIFFformat.6.3.1.4 RSA films scan resolution varies among softwaremanufacturers. Some require a 300 dpi/16 bit image whileothers require 150 dpi/8 bit image. All require a TIFF format.6.3.2 Conversion of DICOM Formatted Radiographs:6.3.2.1 An appropriate DICOM
44、 reader is necessary for thisprocess.6.3.2.2 The resolution, gray scale, and file format should beas described above.6.3.2.3 The dpi of DICOM formatted films are limited bythe hardware used to acquire the image. The output from agiven center must be checked.6.3.2.4 Generally, computer radiographic u
45、nits have a stan-dard resolution and a high resolution setting which must beselected at the time the images are acquired.FIG. 1 Phantom Model Capable of Moving the Femoral Head bySmall Discrete Three Dimensional DisplacementsNOTE 1The displacement mechanism is made of three stages pur-chased from Ed
46、mund Industrial Optics Catalog.FIG. 2 Medium 2.62 in. Square Linear Translation Stages (xyz)F2385 1536.4 Radiographic Exclusion Criterion:6.4.1 Non-RSA Computational Methods:6.4.1.1 These methods are sensitive to changes in theposition of the acetabular socket relative to the beam center.For an indi
47、vidual patient, to minimize unreliable penetrationcalculations over sequential examinations, variations in theacetabular position should be minimized.6.4.1.2 For a given patient examination, the projection ofthe hip socket in the sequential examinations must fall withinthe same region of the radiogr
48、aph, preferably in the middlethird of the film. Projections which all fall within the top orbottom third of the film are also usable.6.4.1.3 Repeated examination of one film using the chosensoftware should result in similar values of reported distancebetween the center of the cup and the center of t
49、he head.Unstable results indicate a poor image quality and the exami-nation should be excluded.NOTE 1Different software programs may have techniques availablefor coping with poor quality films such as manual edge selection. Thesetechniques must be used with caution and their frequency of use must bereported.6.4.2 RSA Computational Methods:6.4.2.1 RSAsoftware analysis programs give several qualitycontrol values which are to be used to determine an exclusioncriterion for a particular film set.6.4.2.2 The condition number gives an indication of thesufficiency of sca
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