1、Designation: F 2028 08Standard Test Methods forDynamic Evaluation of Glenoid Loosening orDisassociation1This standard is issued under the fixed designation F 2028; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. 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 These test methods measure how much a prostheticglenoid component rocks or pivots following cyclic displace-ment of the hume
3、ral 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 test the locking mecha-nism of modular glenoid components, for example, for disas-
4、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 as thestandard. The values given in parentheses are provided forinformation purposes only.1.5 This standard does
5、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 limitations prior to use.2. Referenced Documents2.1 ASTM Standa
6、rds:2E4 Practices for Force Verification of Testing MachinesF 1378 Specification for Shoulder ProsthesesF 1839 Specification for Rigid Polyurethane Foam for Useas a Standard Material for Testing Orthopedic Devices andInstruments3. Terminology3.1 Definitions:3.1.1 glenoidthe prosthetic portion that r
7、eplaces 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, eitherall-polyethylene or a metal baseplate with a polymeric insert.3.1.2 humeral headthe prosthetic portion th
8、at 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 edges;in planar and asymmetric glenoids, it is defined by the bac
9、ksurface.3.1.4 axial load; axial translationthe force and displace-ment, respectively, perpendicular to the glenoid plane; the axialload simulates the net compressive external and muscle forces(see Fig. 1).3.1.5 shear load; shear translationthe force and displace-ment, respectively, parallel to the
10、glenoid plane, applied, forexample, in the superior/inferior or anterior/posterior direction(see Figs. 1 and 2); the shear load simulates the net shearexternal and active and passive soft tissue forces.3.1.6 subluxation loadthe peak shear load required forsubluxation, for example, the peak resistive
11、 force at the glenoidarticular rim opposing movement of the humeral head.3.1.7 subluxation translationthe distance from the gle-noid origin (see Fig. 2), parallel to the glenoid plane, to thepoint at which the subluxation load occurs.3.1.8 superior/inferior (SI)the SI axis is the longest di-mension
12、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).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 Arthropl
13、asty.Current edition approved Feb. 1, 2008. Published February 2008. Originallyapproved in 2000. Last previous edition approved in 2005 as F 2028 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda
14、rds volume information, refer to the standards Document Summary page onthe ASTM website.FIG. 1 Glenoid Plane and Load Directions1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.10 edge displacementsthe translation, perpendicularto
15、 the glenoid plane, of a specific point on the outside edge ofthe glenoid, when subjected to loading (see Fig. 3).GLENOID LOOSENING TEST METHOD4. Summary of Test Method4.1 The prosthetic glenoid component is fixed with bonecement into a bone substitute using the normal surgicaltechnique.4.2 The subl
16、uxation translation is determined experimen-tally on additional components. This is accomplished, using abiaxial apparatus (see Fig. 3) by applying an axial loadperpendicular to the glenoid, then translating the humeral headparallel to the glenoid plane until encountering a peak shearload. This is p
17、erformed in both directions, corresponding to thedirection of intended rocking (for example, superior-inferior,anterior-posterior, or an alternative angle).4.3 The edge displacements of the glenoid are measuredbefore cycling: a given axial load is first applied perpendicularto the glenoid, then the
18、edge displacements are measured withthe humeral head in three positions: at the glenoid origin, andpositioned to 90 % of the subluxation translation (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
19、 displacements, quick speeds, and deform-able polyethylene.)4.4 The humeral head is cycled to 90 % of the subluxationdistance for a fixed number of cycles.4.5 The edge displacements (4.3) are either repeated follow-ing the cycling or measured continuously during the cycling.FIG. 2 Glenoid Axes and O
20、riginFIG. 3 Biaxial Testing ApparatusF20280825. Significance and Use5.1 This test method is intended to investigate the resistanceof a glenoid component to loosening. Glenoid loosening is themost common clinical complication in total shoulder arthro-plasty (see X1.1). The method assumes that looseni
21、ng 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 performance include articular geometry, flange ge-ometry, materials, fixation design, bone quality
22、, 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 glenoid plane (see Fig. 1). Fig. 3shows the axial load to be horizontal and the shear load to
23、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 Specification F 1839.6.3 The glenoid and humeral head shall be enclosed in achamber with water
24、heated to 37 6 2C (98.6 6 3.6F), at leastfor the dynamic portion of the test (see X1.6). A buffer may beadded, if the tester deems this necessary.6.4 A means to measure the axial load, shear load, sheartranslation, and glenoid edge displacements is required. Ameans to measure the axial translation i
25、s 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 shall be tested.At least twoadditional components should be used to determine t
26、he 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 condition. All plastic components shall be sterilizedaccording to the manufacture
27、r-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 head may be used for all tests unless the surface becomesdamaged.7.4 Gleno
28、id and humeral components are used in totalshoulder arthroplasty and should conform to the criteriaspecified in Specification F 1378.8. Procedure8.1 The following steps are common to both the subluxation(4.2) and rocking (4.3-4.5) tests:8.1.1 Secure the glenoid component in a bone substitutewith bon
29、e 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, for example,by using a dye to locate the contact point of the humeral head
30、;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 for symmetricaldesigns).8.1.3 Perform the static measurements (subluxatio
31、n andedge displacements) either in air at room temperature or inwater at 37C. The cyclic testing must 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 N (169 lb) 6 7.5 N (see X1.4).8.2 Determine the subluxation translation experimental
32、ly 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/min(2 in./min) is recommended to avoid polyethylene creep.8.2.2 Yielding is expected a
33、t 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 before rocking:8.3.1 Create a foundation for measuremen
34、ts 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 surface (to avoidexiting either into the articular surfa
35、ce or into the bonesubstitute). Flatten the screw head parallel to the glenoid plane.Alternative methods are acceptable (see X1.8).8.3.2 Rest a displacement measuring device, for example,linear variable differential transformer (LVDT), differentialvariable reluctance transducer (DVRT), or dial gauge
36、, on eachfoundation to measure the displacements perpendicular to theglenoid plane (see X1.8). Continuous measurement is desir-able, but measurement at the beginning and end of the rockingis sufficient.8.3.3 Condition the prosthesis/bone substitute system, forexample, for ten cycles at 0.25 Hz.8.3.4
37、 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 direction. Measure both edge displacements.8.3.6 Translate the hume
38、ral 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 thesubluxation translation to cause a rocking motion of theglenoid at
39、a given frequency (for example, 2 Hz as a result ofthe large translations, or up to a maximum of 6 Hz) to aF2028083maximum number of cycles (for example, 100 000, see X1.7).Maintain the axial load and specified displacement.8.5 Terminate the test when either the maximum number ofcycles has been reac
40、hed 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 report shall include the following:9.1.1 All details relevan
41、t 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.9.1.3 Subluxation TestThe subluxation load and transla-tion f
42、or 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 displacement,maximum number of cycles, testing frequency, and cause oftes
43、t 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 (for example, the displace-ment opposite the loaded side minus
44、 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 occurred should be recorded.10. Precision and Bias10.1 PrecisionTh
45、e 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 chrome humeral heads. Thepopulation mean micromotion before and af
46、ter testing was 3686 330 m and 496 6 275 m, respectively. Each laboratoryutilized different methods for measuring the edge displace-ments, and one laboratory performed the test using a lubricantat the contact surface instead of performing the test in solution(see X1.8).10.1.1 RepeatabilityFor replic
47、ate 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 and after testing condition.10.1.2 ReproducibilityFor replic
48、ate 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 testing condition (h=1.50 vs.hcrit=1.49).All laboratories were
49、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 participation by additional labs with reduced methodol-ogy variances is inte
