1.1 本试验方法涵盖 体外 预期用于外科植入物的可水解降解聚合物（HDP）的降解。它提供了处理样品的详细方法，并提出了评估性质（例如质量、摩尔质量和机械强度）随时间变化的定量技术。 1.1.1 对于许多类型的HDPs，已经在 体外 按照本实践进行降解和 体内 空载样品的降解（见 X1.1.1 ). 1.2 本试验方法的要求适用于各种形式的HDP: 1.2.1 原始聚合物树脂，或 1.2.2 由原始聚合物制成的任何形式，例如成品的半成品部件、成品（可包括包装和灭菌的植入物）或专门制造的测试样本。1.2.2.1 使用该测试方法调节原始树脂、半成品或特殊测试样本可以提供对材料和/或产品开发有用的信息。然而，这些结果不足以预测最终灭菌植入物的降解行为。小节 5.5 , 8.2 ，和 X1.2 提供额外的指导。 1.3 当与被评价器械相关时，本标准为机械加载或流体流动或两者提供指导。给定应用的加载类型、大小和频率的细节超出了本测试方法的范围。 1.4 本标准不适用于主要通过水解以外的机制（例如酶促或氧化降解）降解的聚合物的调理。见 X1.1.1 了解更多信息。 1.5 以SI单位表示的值将被视为标准值。本标准不包括其他计量单位。 1.6 本标准并不旨在解决与其使用相关的所有安全性问题（如果有）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践并确定法规限制的适用性。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ======意义和用途====== 5.1 该试验方法旨在帮助评估外科植入物中使用的HDP材料的降解速率（即质量损失率）和材料或结构性能的变化，或两者兼而有之。已知主要通过水解降解的聚合物包括但不限于 l -丙交酯， d -丙交酯， d、l -丙交酯、乙交酯、己内酯和 p -二氧环己酮。 7 5.2 该测试方法可能不适用于所有类型的植入物应用或所有已知的可吸收聚合物。提醒用户根据被测材料及其潜在应用来考虑测试方法的适当性（参见 X1.1.1 ). 5.3 由于众所周知机械负载可以增加可吸收聚合物的降解速率，因此在比较时需要考虑这种负载的存在和程度 体外 预期或观察到的行为 体内 . 5.3.1 机械卸载水解评价- 将可水解装置在37℃的无机械挑战的水解条件下在缓冲生理浸泡溶液中调节是获得可吸收材料或装置的降解曲线的第一近似值的常用方法。它不一定代表实际 体内 使用条件，其可以包括各种形式的机械加载(例如，静态拉伸、循环拉伸、剪切、弯曲等)。如果器械在其指定用途下的性能包括负载，则仅水解老化不足以完全表征器械。 5.3.2 机械负载水解评价- 加载的目的是近似预期的器械使用条件，以便更好地了解可能发生的潜在物理化学变化。如果在以下条件下可以合理地预期负载，则此类测试可被认为是必要的 体内 服务条件。在可行的情况下，试样应以模拟 体内 条件，包括负载的大小和类型。临床相关的循环负荷试验可包括失效试验或规定次数的循环试验，随后进行评价物理化学性质的试验。 5.3.2.1 静态加载- 值得注意的是，对于一些聚合物材料，已经表明恒定载荷导致相同的失效机制（例如蠕变），并且当与循环载荷（其中循环载荷的最大振幅等于恒定载荷）相比时是最坏的情况。因此，在特定情况下，通过使用恒定负载来简化测试可能是可接受的，即使当预期 体内 加载是循环的。这种测试方法的使用者有责任通过实验或具体参考证明这种简化适用于所研究的聚合物，并且不会改变测试样本的失效模式。如果没有这样的证据，有必要认识到静态加载和循环加载测量的是不同的材料特性，不具有可比性。用一个代替另一个可能会导致对结果的误解。 附注3: 必须小心确保夹具不会引入人为性能或退化问题，或两者兼而有之。一个例子是使用硬质泡沫块，其限制膨胀和膨胀，并且可以提高块内样品压缩的拉出强度测试结果。此外，由于泡沫的闭孔性质而限制的灌注可导致酸性副产物的浓缩，当与正常灌注和缓冲的相比时，酸性副产物导致加速降解 体内 条件。 附注4: 当在负载下进行降解测试时，可能需要在测试期间考虑和监测聚合物蠕变，这可能是重要的。 5.4 经受流动条件的可吸收装置(例如，血管支架，特别是具有药物洗脱组分的那些)可能比保持在静态降解测试条件下的相同装置更快地降解。当可以估计植入物将经受的流动条件时 体内 并复制它们 体外 降解研究应在流动条件下进行。然而，关于适当流动建模的细节超出了本测试方法的范围。 5.5 预期HDP材料的灭菌会导致聚合物的摩尔质量或结构或两者发生变化。这会影响材料或装置的初始机械和物理特性，以及其随后的降解速率。因此，如果测试旨在代表实际性能 体内 标本的包装和灭菌方式应与最终器械一致。出于比较目的，可以包括未灭菌的样本。

1.1 This test method covers in vitro degradation of hydrolytically degradable polymers (HDP) intended for use in surgical implants. It provides a detailed methodology for conditioning samples and suggests quantitative techniques for evaluating changes in properties (for example, mass, molar mass, and mechanical strength) over time. 1.1.1 For many types of HDPs, a correlation has been established between in vitro degradation per this practice and in vivo degradation for unloaded specimens (see X1.1.1 ). 1.2 The requirements of this test method apply to HDPs in various forms: 1.2.1 Virgin polymer resins, or 1.2.2 Any form fabricated from virgin polymer such as a semi-finished component of a finished product, a finished product, which may include packaged and sterilized implants, or a specially fabricated test specimen. 1.2.2.1 Use of this test method for conditioning virgin resins, semi-finished forms, or special test specimens may provide information that is useful for material and/or product development. However, those results are not sufficient for predicting the degradation behavior of the final, sterilized implant. Subsections 5.5 , 8.2 , and X1.2 provide additional guidance. 1.3 This standard provides guidance for mechanical loading or fluid flow, or both, when relevant to the device being evaluated. The specifics of loading type, magnitude, and frequency for a given application are beyond the scope of this test method. 1.4 This standard is not applicable to conditioning of polymers that degrade primarily through mechanisms other than hydrolysis (for example, enzymatic or oxidative degradation). See X1.1.1 for more information. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 This test method is intended to help assess the degradation rates (that is, the mass loss rate) and changes in material or structural properties, or both, of HDP materials used in surgical implants. Polymers that are known to degrade primarily by hydrolysis include but are not limited to homopolymers and copolymers of l -lactide, d -lactide, d,l -lactide glycolide, caprolactone, and p -dioxanone. 7 5.2 This test method may not be appropriate for all types of implant applications or for all known absorbable polymers. The user is cautioned to consider the appropriateness of the test method in view of the materials being tested and their potential application (see X1.1.1 ). 5.3 Since it is well known that mechanical loading can increase the degradation rate of absorbable polymers, the presence and extent of such loading needs to be considered when comparing in vitro behavior with that expected or observed in vivo . 5.3.1 Mechanically Unloaded Hydrolytic Evaluation— Conditioning of a hydrolysable device under mechanically unchallenged hydrolytic conditions at 37 °C in buffered physiological soaking solution is a common means to obtain a first approximation of the degradation profile of an absorbable material or device. It does not necessarily represent actual in vivo service conditions, which can include mechanical loading in a variety of forms (for example, static tensile, cyclic tensile, shear, bending, and so forth). If the performance of a device under its indicated use includes loading, hydrolytic aging alone is NOT sufficient to fully characterize the device. 5.3.2 Mechanically Loaded Hydrolytic Evaluation— The objective of loading is to approximate the expected device service conditions so as to better understand potential physicochemical changes that may occur. Such testing can be considered as necessary if loading can be reasonably expected under in vivo service conditions. When feasible, test specimens should be loaded in a manner that simulates in vivo conditions, both in magnitude and type of loading. Clinically relevant cyclic load tests may include testing to failure or for a specified number of cycles followed by testing to evaluate physicochemical properties. 5.3.2.1 Static Loading— It is notable that for some polymeric materials it has been shown that a constant load results in the same failure mechanism (for example, creep) and is the worst case when compared to a cyclic load (where the maximum amplitude of the cyclic load is equal to the constant load). Thus, in specific cases it may be acceptable to simplify the test by using a constant load even when the anticipated in vivo loading is cyclic. It is encumbent upon the user of this test method to demonstrate through experiment or specific reference that this simplification is applicable to the polymer under investigation and does not alter the failure mode of the test specimen. If such evidence is not available, it is necessary to recognize that static loading and cyclic loading are measuring different material properties and are not comparable. Using one to replace the other could lead to misinterpretation of the results. Note 3: Caution must be taken to ensure that fixturing does not introduce artifactual performance or degradation issues, or both. An example is the use of rigid foam block, which restricts swelling and expansion and can elevate pullout strength test results from sample compression within the block. Additionally, restricted perfusion due to the closed cell nature of the foam can result in concentration of acidic byproducts that result in accelerated degradation when compared to a normally perfused and buffered in vivo condition. Note 4: When performing degradation testing under load, it may be necessary to consider and monitor polymer creep during testing, which may be significant. 5.4 Absorbable devices subjected to flow conditions (for example, vascular stents, particularly those with a drug eluting component) may degrade more rapidly than the same device maintained under static degradation test conditions. When it is feasible to estimate the flow conditions that an implant will be subjected to in vivo and replicate them in vitro the degradation study should be conducted under flow conditions. However, details regarding appropriate flow modeling are beyond the scope of this test method. 5.5 Sterilization of HDP materials should be expected to cause changes in molar mass or structure, or both, of the polymers. This can affect the initial mechanical and physical properties of a material or device, as well as its subsequent rate of degradation. Therefore, if a test is intended to be representative of actual performance in vivo , specimens shall be packaged and sterilized in a manner consistent with that of the final device. Non-sterilized specimens may be included for comparative purposes.