1、Designation: F2028 08 (Reapproved 2012)1Standard Test Methods forDynamic Evaluation of Glenoid Loosening orDisassociation1This standard is issued under the fixed designation F2028; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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.1NOTEUnits information was editorially corrected in January 2013.1. Scope1.1 These test methods measure how much a prost
3、heticglenoid component rocks or pivots following cyclic displace-ment of the humeral head to opposing glenoid rims (forexample, superior-inferior or anterior-posterior). Performanceis judged by the tensile displacement opposite each loaded rimafter dynamic rocking.1.2 The same setup can be used to t
4、est the locking mecha-nism of modular glenoid components, for example, for disas-sociation.1.3 These test methods cover shoulder replacement designswith monolithic or modular glenoid components for cementedfixation.1.4 The values stated in SI units are to be regarded asstandard. No other units of me
5、asurement are included in thisstandard.1.5 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 l
6、imitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of Testing MachinesF1378 Specification for Shoulder ProsthesesF1839 Specification for Rigid Polyurethane Foam for Use asa Standard Material for Testing Orthopaedic Devices andInstruments3. Terminol
7、ogy3.1 Definitions:3.1.1 glenoidthe prosthetic portion that replaces the gle-noid fossa of the scapula and articulates with a prostheticreplacement of the humeral head. It may consist of one or morecomponents from one or more materials, for example, either allpolyethylene or a metal baseplate with a
8、 polymeric insert.3.1.2 humeral headthe prosthetic portion that replaces theproximal humerus or humeral head and articulates with thenatural glenoid fossa or a prosthetic replacement.3.1.3 glenoid planesee Fig. 1. In symmetrical glenoids,the glenoid plane is defined by joining the two articular edge
9、s;in planar and asymmetric glenoids, it is defined by the backsurface.3.1.4 axial load; axial translationthe force anddisplacement, respectively, perpendicular to the glenoid plane;the axial load simulates the net compressive external andmuscle forces (see Fig. 1).3.1.5 shear load; shear translation
10、the force anddisplacement, respectively, parallel to the glenoid plane,applied, for example, in the superior/inferior or anterior/posterior direction (see Figs. 1 and 2). The shear load simulatesthe net shear external and active and passive soft tissue forces.3.1.6 subluxation loadthe peak shear loa
11、d required forsubluxation (for example, the peak resistive force at theglenoid articular rim opposing movement of the humeral head).3.1.7 subluxation translationthe distance from the glenoidorigin (see Fig. 2), parallel to the glenoid plane, to the point atwhich the subluxation load occurs.3.1.8 sup
12、erior/inferior (SI)the SI axis is the longest di-mension of the glenoid (see Fig. 2).3.1.9 anterior/posterior (AP)the AP axis the widest di-mension of the glenoid (see Fig. 2).3.1.10 edge displacementsthe translation, perpendicularto the glenoid plane, of a specific point on the outside edge ofthe g
13、lenoid, when subjected to loading (see Fig. 3).1These test methods are under the jurisdiction of ASTM Committee F04 onMedical and Surgical Materials and Devices and are the direct responsibility ofSubcommittee F04.22 on Arthroplasty.Current edition approved Dec. 15, 2012. Published January 2013. Ori
14、ginallyapproved in 2000. Last previous edition approved in 2008 as F2028 08. DOI:10.1520/F2028-08R12E01.2For 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1GLENOID LOOSENING TEST METHOD4. Summary of Test Method4.1 The prosthetic glenoid component is fixed with bonecement into a bone substitute usin
16、g the normal surgicaltechnique.4.2 The subluxation translation is determined experimen-tally on additional components. This is accomplished, using abiaxial apparatus (see Fig. 3) by applying an axial loadFIG. 1 Glenoid Plane and Load DirectionsFIG. 2 Glenoid Axes and OriginFIG. 3 Biaxial Testing App
17、aratusF2028 08 (2012)12perpendicular to the glenoid, then translating the humeral headparallel to the glenoid plane until encountering a peak shearload. This is performed in both directions, corresponding to thedirection of intended rocking (for example, superior-inferior,anterior-posterior, or an a
18、lternative angle).4.3 The edge displacements of the glenoid are measuredbefore cycling: a given axial load is first applied perpendicularto the glenoid, then the edge displacements are measured withthe humeral head in three positions: at the glenoid origin, andpositioned to 90 % of the subluxation t
19、ranslation (see X1.2), inboth directions, as defined in 4.2. (Cycling to 90 % of thesubluxation load would be acceptable, but is not practicalbecause of the large displacements, quick speeds, and deform-able polyethylene.)4.4 The humeral head is cycled to 90 % of the subluxationdistance for a fixed
20、number of cycles.4.5 The edge displacements (4.3) are either repeated follow-ing the cycling or measured continuously during the cycling.5. Significance and Use5.1 This test method is intended to investigate the resistanceof a glenoid component to loosening. Glenoid loosening is themost common clini
21、cal complication in total shoulder arthro-plasty (see X1.1). The method assumes that loosening occursbecause of edge loading, often called the rocking-horse phe-nomenon.5.2 This test method can be used both to detect potentialproblems and to compare design features. Factors affectingloosening perfor
22、mance include articular geometry, flangegeometry, materials, fixation design, bone quality, and surgicaltechnique.6. Apparatus and Equipment6.1 The test apparatus shall be constructed such that an axialload is applied perpendicular to the glenoid plane and a shearload is applied parallel to the glen
23、oid plane (see Fig. 1). Fig. 3shows the axial load to be horizontal and the shear load to bevertical; however, this arrangement may be reversed.6.2 A bone substitute representing the strength or glenoidcancellous bone (see X1.5) shall be used. If a polyurethanefoam is used, it shall conform to Speci
24、fication F1839.6.3 The glenoid and humeral head shall be enclosed in achamber with water heated to 37 6 2C, at least for thedynamic portion of the test (see X1.6). A buffer may be added,if the tester deems this necessary.6.4 A means to measure the axial load, shear load, sheartranslation, and glenoi
25、d edge displacements is required. Ameans to measure the axial translation is desirable.6.5 The tests shall be performed on either mechanical orhydraulic load frames with adequate load capacity and shallmeet the criteria of Practices E4.7. Sampling and Test Specimens7.1 Aminimum of three samples shal
26、l be tested.At least twoadditional components should be used to determine the sub-luxation translation. The test may be conducted along thesuperior-inferior axis, the anterior-posterior axis, or anotheraxis of interest to the user.7.2 All glenoid components shall be in the final manufac-tured condit
27、ion. All plastic components shall be sterilizedaccording to the manufacturer-recommended specifications forclinical use.7.3 The humeral head shall include the identical radius orradii and material as the actual implant. Other features of thehumeral component such as the shaft may be omitted. Thesame
28、 head may be used for all tests unless the surface becomesdamaged.7.4 Glenoid and humeral components are used in totalshoulder arthroplasty and should conform to the criteriaspecified in Specification F1378.8. Procedure8.1 The following steps are common to both the subluxation(4.2) and rocking (4.3-
29、4.5) tests:8.1.1 Secure the glenoid component in a bone substitutewith bone cement using the normal surgical procedure andinstrumentation. Do not perform tests until the cement hascured properly.8.1.2 Position the path of the humeral head on the glenoidwithin 60.5 mm (sideways) of the desired path,
30、for example,by using a dye to locate the contact point of the humeral head;a dye is unnecessary for congruent prostheses. Locate thecenter of the path (for the subluxation test, this need not beexact; for the rocking test, the peak loads at each rim duringcycling should be within 610 % of each other
31、 for symmetricaldesigns).8.1.3 Perform the static measurements (subluxation andedge displacements) either in air at room temperature or inwater at 37C. The cyclic testing shall be performed in 37Cwater (see 6.3, X1.3, and X1.6).8.1.4 Apply a given axial load to the glenoid, for example,750 6 7.5 N (
32、see X1.4).8.2 Determine the subluxation translation experimentally onseparate components (see X1.2):8.2.1 After applying the axial load, displace the humeralhead at a constant rate to a given displacement, ensuring that apeak load is achieved in both directions. A rate of 50 mm/minis recommended to
33、avoid polyethylene creep.8.2.2 Yielding is expected at the recommended load anddoes not constitute a failure. The test shall be terminated if theinsert of a modular glenoid disassociates.8.2.3 Record the axial load, subluxation load, and sublux-ation translation.8.3 Measure the edge displacements be
34、fore rocking:8.3.1 Create a foundation for measurements at both ends ofthe glenoid at a similar distance from the back surface of theglenoid for all prostheses. One possibility is to insert 2-mm-diameter screws into the outside edge at each end of theglenoid prosthesis, parallel to the articular sur
35、face (to avoidexiting either into the articular surface or into the bonesubstitute). Flatten the screw head parallel to the glenoid plane.Alternative methods are acceptable (see X1.8).F2028 08 (2012)138.3.2 Rest a displacement measuring device, for example,linear variable differential transformer (L
36、VDT), differentialvariable reluctance transducer (DVRT), or dial gauge, on eachfoundation to measure the displacements perpendicular to theglenoid plane (see X1.8). Continuous measurement isdesirable, but measurement at the beginning and end of therocking is sufficient.8.3.3 Condition the prosthesis
37、/bone substitute system, forexample, for ten cycles at 0.25 Hz.8.3.4 Measure the edge displacements with the humeralhead located at the glenoid origin (see Fig. 2).8.3.5 Translate the humeral head parallel to the glenoidplane to 90 % of the subluxation translation determined previ-ously (8.2) in one
38、 direction. Measure both edge displacements.8.3.6 Translate the humeral head to 90 % of the subluxationtranslation in the opposite direction and measure both edgedisplacements.8.3.7 Repeat the three readings at least once to ensurerepeatability.8.4 Cyclically translate the humeral head to 90 % of th
39、esubluxation translation to cause a rocking motion of theglenoid at a given frequency (for example, 2 Hz as a result ofthe large translations, or up to a maximum of 6 Hz) to amaximum number of cycles (for example, 100 000) (see X1.7).Maintain the axial load and specified displacement.8.5 Terminate t
40、he test when either the maximum number ofcycles has been reached or a modular glenoid insert disasso-ciates.8.6 Repeat the glenoid edge displacement measurements(8.3) if measurements were not taken continuously.8.7 Testing may be continued to a higher number of cyclesif desired.9. Report9.1 The test
41、 report shall include the following:9.1.1 All details relevant to the particular implants testedincluding type, size, and lot number as well as the glenoidradius, humeral head radius or radii, and the prosthesismaterial.9.1.2 The axis and direction of testing (for example, central-superior-inferior)
42、.9.1.3 Subluxation TestThe subluxation load and transla-tion for each specimen, as well as the axial load and displace-ment rate. A chart plotting the load versus displacement withthe 90 and 100 % subluxation loads clearly marked should beincluded.9.1.4 Rocking TestThe axial load, cyclic displacemen
43、t,maximum number of cycles, testing frequency, and cause oftest termination. Testing parameters that differ from thoserecommended shall be justified.9.1.5 Displacement TestThe edge displacements beforeand following cycling, highlighting the tensile displacement onthe unloaded side following rocking
44、(for example, the displace-ment opposite the loaded side minus the value with the head atthe glenoid origin).9.1.6 If the amplitude of the axial translation decreasessuddenly during the test (indicating a tilt of the glenoid and theprobable onset of loosening), the number of cycles at whichthis occu
45、rred should be recorded.10. Precision and Bias10.1 PrecisionThe precision of this test method wasestablished by an interlaboratory comparison among fourlaboratories, with each laboratory testing three specimens. Thespecimens tested were commercially available UHMWPEglenoid components and cobalt chro
46、me humeral heads. Thepopulation mean micromotion before and after testing was 3686 330 m and 496 6 275 m, respectively. Each laboratoryutilized different methods for measuring the edgedisplacements, and one laboratory performed the test using alubricant at the contact surface instead of performing t
47、he test insolution (see X1.8).10.1.1 RepeatabilityFor replicate results obtained by thesame laboratory on nominally identical test specimens, therepeatability standard deviation (sr) was 72.3 m before testingand 268.0 m after testing. All laboratories were within thecritical k values for the before
48、and after testing condition.10.1.2 ReproducibilityFor replicate results obtained bythe same laboratory on nominally identical test specimens, thereproducibility standard deviation (sR) was 335.9 m beforetesting and 359.4 m after testing. One laboratory exceeded thecritical h value for the before tes
49、ting condition (h=1.50 vs.hcrit=1.49).All laboratories were within the critical h values forthe after testing condition.10.2 The above round robin data represent initial efforts atestablishing a precision and bias statement for this test methodand have been published before documentation of full labparticipation has been completed (4 out of 6). Additionally,some labs experienced difficulty with measurement of micro-motion resulting in test method variances. Further testing iswarranted and a revised precision and bias statement incorpo-rating participa
