1、BRITISH STANDARD BS 3531-23.1: 1991 ISO 9585:1990 Implants for osteosynthesis Part 23: Bone plates Section 23.1 Method for determination of bending strength and stiffnessBS3531-23.1:1991 This British Standard, having been prepared under the directionof the Health Care Standards Policy Committee, was
2、published under the authorityof the Standards Board and comes into effect on 28June1991 BSI 08-1999 First published January 1989 Second edition June 1991 The following BSI references relate to the work on this standard: Committee reference HCC/22 Draft for comment 88/55976 ISBN 0 580 19788 3 Committ
3、ees responsible for this British Standard The preparation of this British Standard was entrusted by the Health Care Standards Policy Committee (HCC/-) to Technical Committee HCC/22, upon which the following bodies were represented: British Institute of Surgical Technologists British Investment Casti
4、ng Trade Association British Medical Association British Orthopaedic Association British Steel Industry British Surgical Trades Association Department of Health Institute of Sterile Services Management Medical Sterile Products Association Ministry of Defence National Association of Theatre Nurses Ro
5、yal College of Surgeons of England Royal Veterinary College Scottish Office Amendments issued since publication Amd. No. Date CommentsBS3531-23.1:1991 BSI 08-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Definitions 1 3 Apparatus 1 4 Procedure 1 5 Ca
6、lculation of results 3 6 Test report 4 Figure 1 General arrangement of four-point bend test 2 Figure 2 Load deflection diagram 2 Publication(s) referred to Inside back coverBS3531-23.1:1991 ii BSI 08-1999 National foreword This Section of BS 3531 has been prepared under the direction of the Health C
7、are Standards Policy Committee and supersedes BS 3531-23.1:1988, which is withdrawn. It is identical with ISO 9585:1990 “Implants for surgery Determination of bending strength and stiffness of bone plates” published by the International Organization for Standardization (ISO). Requirements for orthop
8、aedic implants (then termed “surgical implants”) were first published in 1962 as BS 3531. In 1968 a part revision of BS 3531:1962 was issued as BS 3531-1, which dealt with surgical implants made of all materials. In1980 the first four Parts of a multi-part version of BS 3531 were published. A furthe
9、r 19 Parts of BS 3531 were subsequently published. The revision of BS 3531-5 offered the opportunity to facilitate the implementation of published and forthcoming standards, and to separate, in different Parts of BS3531, requirements for bone plates from those for bone screws and auxiliary equipment
10、. Accordingly, therefore, bone plates are covered by BS 3531-23, published in a number of Sections, whilst screws and auxiliary equipment are retained in BS 3531-5, also published in Sections. BS 3531 now only covers implants for osteosynthesis, BS 7251 covers joint prostheses, BS 7252 covers metall
11、ic materials for surgical implants, BS 7253 covers non-metallic materials for surgical implants and BS 7254 covers orthopaedic implants,i.e. aspects common to both osteosynthesis and joint replacement. BS 3531-23.1 was first published in 1988 at the request of the Department of Health and Social Sec
12、urity, to meet a need within the medical equipment industry for a method of assessing certain mechanical properties of plates used in osteosynthesis. This edition of BS 3531-23.1 gives the equations to be used in determining the equivalent bending stiffness and bending strength. Information on the s
13、trength and stiffness of bone plates will enable the bending characteristics of different plates relevant to surgical practice to be compared, and should assist the surgeon in deciding which plate should be used in particular clinical situations. The value obtained for the bending strength relates t
14、o the load which will cause the plate to bend in clinical service and also to the force necessary to pre-form the plate in the operating theatre to match the bones to which it is to be attached. Currently there is controversy regarding the optimum stiffness of a plate which allows effective callus f
15、ormation and healing of a fracture, and this method of testing will allow the stiffness of different plates to be compared quantitatively. It is strongly recommended that products tested in accordance with this Section of BS 3531 be manufactured according to the recommendations given in the “Guide t
16、o Good Manufacturing Practice for Orthopaedic Implants”. 1) Product certification. Users of this British Standard are advised to consider the desirability of third party certification of product conformity with this British Standard based on test and continuing surveillance, which may be coupled wit
17、h assessment of a suppliers quality systems against the appropriate Part of BS5750. 1) Compiled by the Department of Health and Social Security; published and available from Her Majestys Stationery Office, 49 High Holborn, London WC1 for personal callers, or by post from HMSO, P.O. Box 276, London S
18、W8 5DT.BS3531-23.1:1991 BSI 08-1999 iii Enquiries as to the availability of third party certification will be forwarded by BSI to the Association of Certification Bodies. If a third party certification scheme does not already exist, users should consider approaching an appropriate body from the list
19、 of Association members. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages
20、 This document comprises a front cover, an inside front cover, pagesi toiv, pages1to4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blank
21、BS3531-23.1:1991 BSI 08-1999 1 1 Scope This International Standard describes a test method for determining the bending strength and stiffness of straight bone plates. It may also be used to test plates having a small initial curvature intended to produce pre-loading of the bone when fitted and to te
22、st the straight portion of angled plates. This test method is not recommended for plates of length less than50mm nor for plates designed to be used with, or forming parts of, intramedullary devices. NOTE 1A test method for plates of length less than 50mm is in preparation. 2 Definitions For the purp
23、oses of this International Standard, the following definitions apply. 2.1 moment turning effect of a force about an axis, expressed numerically by the product of the force F and the distance h measured perpendicularly from the axis to the line of action of the force Unit: Nm 2.2 bending moment, M b
24、moment acting about an axis perpendicular to the long axis of a body and generally producing lateral deflection Unit: Nm 2.3 deflection linear displacement due to bending measured perpendicular to the original axis of the plate Unit: m 2.4 bending strength value of the bending moment at fracture, or
25、 at a specified proof point, whichever is the lower Unit: Nm 2.5 equivalent bending stiffness stiffness of the plate calculated from the dimensions of the test configuration and the slope S of the linear part of the load/deflection diagram defined by the mechanical test Unit: Nm 2 NOTE 2This equival
26、ent bending stiffness takes account of the holes or slots in the plate. 3 Apparatus 3.1 Test rig, to produce a loading system in accordance with Figure 1, the four rollers (indicated by hatched circles) being so constrained that their axes remain parallel. 3.2 Rollers, of cylindrical form and of equ
27、al diameters within the range of 8mm to 13mm, or of profiled form corresponding to the cross-section of the plate to be tested, and having a mean diameter within the range 8 mm to 13 mm. It is desirable that one of the rollers be secured to the specimen to restrain longitudinal movement and that all
28、 rollers are secured to maintain their relative position. 3.3 Means of applying forces,e.g. a mechanical testing machine. 3.4 Device(s), for measurement of relative displacement(s). 4 Procedure 4.1 General Conduct bending tests using the apparatus specified in clause 3. Use the cylindrical rollers t
29、o test flat plates and plates of curved cross-section, in which the deviation from flatness at the centre of the plate does not exceed b/6, where b is the width of the plate. Test other plates using rollers of suitable profile.BS3531-23.1:1991 2 BSI 08-1999 Figure 1 General arrangement of four-point
30、 bend test Figure 2 Load deflection diagramBS3531-23.1:1991 BSI 08-1999 3 4.2 Placement of test specimen Place the test specimen in the test rig and position it in accordance with the following: a) Place the plate so that the inner rollers are in contact with the surface of the plate intended to be
31、in contact with bone. b) If the plate is symmetrical, place it symmetrically with the two innermost screw holes between the inner rollers. c) If the plate has a central screw hole, place it with the central screw hole and one other screw hole symmetrically between the inner rollers. d) If the plate
32、is asymmetrical, place it with two screw holes between the inner rollers so that the position of the fracture for which it is intended to be used shall be between the inner rollers. e) Position the outer rollers at equal distances ofh metres from the inner rollers as shown in Figure 1, so that one h
33、ole only is in the length between the inner and outer rollers. f) Ensure that the inner rollers are not in contact with parts of the plate where there is a screw hole. Wherever possible, the outer rollers should not be in contact with parts of the plate which include a screw hole. g) Measure the dis
34、tance k, in metres, between the inner rollers. h) Align the axis of the test specimen to be perpendicular to the axes of the rollers. i) Install the device(s) to measure the deflection, in metres, of the plate relative to the initial position of the outer roller supports. The deflection may be measu
35、red: 1) on a line midway between the central rollers( 1 ), or 2) at one of the central rollers ( 2 ), or 3) at each of the central rollers ( 2and ( 3 ). If the location of the holes in the plate is not symmetrical relative to its length, method 3) is recommended. 4.3 Applying force F Apply a force F
36、 at the central loading line indicated and measure the corresponding deflections. Gradually increase the value of F noting the corresponding deflections at each interval, and drawing a graph of F to a base of deflection until the value of F is obtained at which either the plate fractures, F = F max.
37、 or the plate deflects so that the load deflection graph shows appreciable yield (F = P) as shown in Figure 2. 4.4 Use of specimens Test each specimen once only and then discard it. 5 Calculation of results 5.1 Mean deflection If deflections 2and 3are measured as described in4.2 i)3), calculate the
38、mean deflection at each stage of the test: 4= 0,5 ( 2+ 3 ) Draw a graph of force F to a base of deflection 4 . 5.2 Equivalent bending stiffness Draw the best straight line through the initial (linear) pad of the load deflection diagram as shown in Figure 2, where this line has a slope S as shown in
39、Figure 2. If the deflection has been measured as specified in4.2 i)1), calculate the equivalent bending stiffness, E, from the expression: where If the deflection has been measured as specified in4.2 i) 2) or 4.2 i)3), calculate the equivalent bending stiffness, E, by the expression: where h, k and
40、S are as above. 5.3 Bending strength On the graph of load against deflection, draw a straight line parallel to the linear pad of the graph, offset by an amount q metres as shown in Figure 2. The intersection of this line with the curve is the proof point, and this defines the proof load P. Calculate
41、 q from the expression: q = 0,02(2h + k) .(1) h is the distance between inner and outer rollers, in metres; k is the distance between inner rollers, in metres; S is the slope of the load/deflection curve, in newton metres. .(2)BS3531-23.1:1991 4 BSI 08-1999 Calculate the bending strength, in newton
42、metres, from the expression: Bending strength = 0,5Ph where If fracture of the plate occurs before the load/deflection curve intersects the offset line, calculate the bending strength, in newton metres, from the expression: Bending strength = 0,4F max h where NOTE 3 This expression uses an equivalen
43、t proof load, equal to0,8 times the maximum load. 6 Test report The test report shall include the following information: a) the bending strength, in newton metres; b) the offset q, in metres, used to determine the proof point; c) the equivalent bending stiffness, in newton metres squared, calculated
44、 from equation 1 or 2 as appropriate; d) if the plate fractures before the proof deflection is attained, this shall be recorded; e) the identity of the plate,e.g. type, length in millimetres, manufacturers catalogue number and batch number, as supplied by the party requesting the test. P is the proo
45、f load in newtons; h is the distance between inner and outer rollers, in metres. F max is the maximum load, in newtons; h is the distance between inner and outer rollers, in metres.BS3531-23.1:1991 BSI 08-1999 Publication(s) referred to See national foreword.BS 3531-23.1: 1991 ISO 9585:1990 BSI 389
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