1、Designation: F 2385 04Standard Test Method forDetermining Femoral Head Penetration into AcetabularComponents of Total Hip Replacement Using ClinicalRadiographs1This standard is issued under the fixed designation F 2385; the number immediately following the designation indicates the year oforiginal a
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides guidance for the measurementof the relativ
3、e displacement 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 test method is primarily intended for use inevaluating patients receiving THRs composed of a
4、polyethyl-ene acetabular component articulating against a metal orceramic femoral head.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 test method will focus on computer assisted com-putational methodologie
5、s for measuring relative displacementsover time but not to the exclusion of other methodologies.1.5 This test method describes methods for conducting aradiographic wear/creep study utilizing various computationalmethods and is not intended to promote or endorse a particularmethod.1.6 It is not the i
6、ntent of this test method 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 test method to enable comparisonsof relative displacements occurring in groups of patientsreceiving different formu
7、lations of bearing materials. It mustbe recognized, however, that there are many possible variationsin the in vivo conditions. A single clinical study may not beuniversally representative.1.8 This test method is not intended to be a performancestandard. It is the responsibility of the user of this t
8、est methodto characterize the safety and effectiveness of the prosthesisunder evaluation.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.1.10 The use of this standard may involve the op
9、eration 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 does not determine the applicability of regu
10、latorylimitations 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 health practices and determine the applica-
11、bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 All radiographic termi
12、nology 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 utilizesin vivo tantalum beads, an external r
13、eference cage, and twox-ray generators which take two exposures simultaneously.There 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
14、define the implant as a rigid body.1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.22 on Arthroplasty.Current edition approved May 1, 2004. Published May 2004.2For referenced ASTM stand
15、ards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual 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
16、standard.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.2.2 cage markerstantalum beads held in an externalreference frame used to create a three dimensional coordinatesystem for measuring relative displacements.3.2.2.3 segmenta
17、three dimensional rigid body defined bya minimum of three markers.3.2.3 edge detectionmethod of image analysis used todetermine the two dimensional or three dimensional centerpoint of a curved surface. Many computational methods ofedge detection exist.3.2.4 coordinate system/axesthree orthogonal axe
18、s 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 segment 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 direc
19、tion 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 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-axist
20、he 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 number of computational methods that canbe used to measure creep/wear of a polyethylene component.Adescription of a few of the commonly used current m
21、ethods 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 its developer Dr. John Martell ofChicago University, is a semi-automated computer techniqueusing edge detection and the Hough transformation for th
22、edetermination of polyethylene wear. This technique uses se-quential A/P films for two dimensional analysis and A/P andlateral sequential films for three dimensional analysis (2).3.3.2 Polywear methoda software program developed byDr. Peter Devane of the Wellington School of Medicine, NewZealand is
23、a semi-automated computer technique using edgedetection for the determination of polyethylene wear. Thistechnique uses sequential A/P films for two dimensionalanalysis and A/P and lateral sequential films for three dimen-sional analysis (3).3.3.3 UmRSAan RSA software program developed byBiomedical I
24、nnovations AB in Umea Sweden. It utilizessequential 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-RSAan RSA software program develop
25、ed atthe University of Leiden, Sweden. It utilizes sequential radiopairs in order to measure relative displacements between twosegments (5).4. Significance and Use4.1 This test method uses clinical radiographs of the hipjoint of a patient that has received a total hip replacement tomeasure the combi
26、ned effect of plastic deformation and wear atthe articular interface which results in three dimensionaldisplacements of the femoral head into the acetabular compo-nent.4.2 This test method addresses the validation of the variouscomputational methods available for measuring the magnitudeof creep/wear
27、 accruing at the articular surface of THRs.4.3 This test method addresses the type of radiographicprojections needed for an analysis as well as general radio-graphic parameters needed for obtaining high quality films.4.4 This test method addresses the criterion for evaluatingclinical radiographs for
28、 inclusion in a study.4.5 This test method addresses the conversion of radio-graphic images to the appropriate digital format needed for thevarious computer assisted computational methods.5. Validation5.1 A physical phantom model which is capable of replicat-ing the three dimensional displacement of
29、 the femoral head atmagnitudes of displacements that are expected to occur clini-cally should be used to validate new software programs,modifications to existing programs, and variations to theexperimental protocol which may effect the results of themeasurements. A recent publication describes such
30、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) for calculatingaccuracy and precision can be used. Illustrative values for theaccuracy and precision as measured by this method are
31、 listed inthe appendix.5.2 To generate data for a precision and bias statement, thePractice E 177 should be followed.FIG. 1 Phantom Model Capable of Moving the Femoral Head bySmall Discrete Three Dimensional DisplacementsF23850426. Material6.1 Non-RSA Methods of Obtaining Clinical Radiographsfor Mea
32、suring 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 anddirection of the three di
33、mensional 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 centered includingboth
34、 hips, typically taken using a 14 by 17 film or target size.As 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 distance of 40 in. and an exposur
35、e setting of 80 kv 25-30maS.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 40 in. and an exposure setting of 80 kv 25-30maS.6.1.5 Some non-RSA methods have been validated for theuse of ninety degree standin
36、g 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 for this purpose.6.1.5.2 Atypical radiographic set-up
37、 would have a source toplate distance of 40 in. and an exposure setting of 85 kv 40-50maS.6.2 RSA Method of Obtaining Clinical Radiographs forMeasuring Femoral Head Penetration:6.2.1 These radiographs can be taken in the supine orstanding position. The method must be consistent throughoutthe subsequ
38、ent 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 utilizes one fixed and oneportable generator.6.2.5 The generators are positioned
39、 having a 60 in. source toplate distance and angled at 40 degrees. The set-up recom-mended by the individual software manufacturers is to befollowed.6.2.6 Radiographic settings for the RSA projections focuson obtaining high contrast between the tantalum markers andthe surrounding bone and metal. Thi
40、s is accomplished by usinghigh kilovolt 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 maS can be used.6.2.8 Many portable x-ray units and some fixed units are notcapable of operating at 150 kv. In
41、these situations, settings of125 kv and 12-16 maS 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 software developers for use in converting a plainradiograph in
42、to 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 grayscale resolution of 8 bit and saved in a TIFFformat.6.3.1.4
43、 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 reader is necessary for thisprocess.6.3.2.2 The resolutio
44、n, 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 units have a stan-dard resolution and a high resolution set
45、ting which must beselected at the time the images are acquired.6.4 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 individual patient, to minimize unreliable
46、 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 radiograph, preferably in the middleNOTEThe d
47、isplacement mechanism is made of three stages purchasedfrom Edmund Industrial Optics Catalog.FIG. 2 Medium 2.62 in. Square Linear Translation Stages (xyz)F2385043third 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 on
48、e film using the chosensoftware should result in similar values of reported distancebetween the center of the cup and the center of the head.Unstable results indicate a poor image quality and the exami-nation should be excluded.NOTE 1Different software programs may have techniques availablefor copin
49、g 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 scatter of the patient markers (7). Generally,condition number values lower than 150 are acceptable.6.4.2.3 Mean error of rigid body fitting gives an indicationof how well the
