1.1 本试验方法包括 体外 用于外科植入物的水解降解聚合物（HDP）的降解。 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，如成品的半成品组件、成品（可能包括包装和灭菌的植入物）或特殊制造的试样。 1.3 当与被评估设备相关时，本试验方法为机械负载或流体流动或两者提供指导。给定应用的负载类型、幅值和频率的细节超出了本试验方法的范围。 1.4 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1 本试验方法旨在帮助评估外科植入物中使用的HDP材料的降解率（即质量损失率）和材料或结构特性的变化，或两者的变化。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 -二恶烷酮。 7. 5.2 本试验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。 鉴于所测试的材料及其潜在应用，提醒用户考虑测试方法的适当性（参见 X1.1.1 ). 5.3 众所周知，机械加载可以提高可吸收聚合物的降解速率，因此在比较时需要考虑这种加载的存在和程度 体外 预期或观察到的行为 体内 . 5.3.1 机械卸载水解评估- 在37°C缓冲盐水中的机械无挑战水解条件下调节可水解装置是获得可吸收材料或装置降解曲线第一近似值的常用方法。它不一定代表实际 体内 工作条件，包括各种形式的机械载荷（例如。 静态拉伸、循环拉伸、剪切、弯曲等）。如果设备在其指定用途下的性能包括负载，则仅水解老化不足以充分表征设备。 5.3.2 机械加载水解评估- 加载的目的是近似（在37°C缓冲盐水中）实际预期的设备使用条件，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预期负载，则可以认为有必要进行此类测试 体内 使用条件。可行时，应以模拟的方式加载试样 体内 荷载大小和类型的条件。临床相关的循环负荷测试可能包括失效测试或指定次数的循环测试，然后进行测试以评估物理化学特性。 5.3.2.1 静态载荷- 值得注意的是，对于一些聚合物材料，已经表明恒定载荷会导致相同的失效机制（例如蠕变），并且与循环载荷相比是最坏的情况（其中循环载荷的最大幅度等于恒定载荷）。因此，在特定情况下，可以通过使用恒定负载来简化测试，即使在预期 体内 加载是循环的。本试验方法的使用者必须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，并且不会改变试样的失效模式。如果没有此类证据，则有必要认识到静态荷载和循环荷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。 注3: 必须小心，以确保夹具不会引入人为性能或退化问题，或两者兼而有之。例如，使用硬质泡沫块，可以限制膨胀和膨胀，并可以提高块内样品压缩的拉拔强度测试结果。此外，与正常灌注和缓冲液相比，由于泡沫的闭孔性质而导致的灌注受限可能会导致酸性副产物的浓度增加，从而导致加速降解 体内 条件 注4: 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，这可能非常重要。 5.4 受流动条件影响的可吸收装置（例如，血管支架，特别是具有药物洗脱成分的支架）的降解速度可能比静态降解试验条件下保持的相同装置更快。 当可以估计植入物将受到的流动条件时 体内 并复制它们 体外 降解研究应在流动条件下进行。然而，有关适当流量建模的详细信息超出了本测试方法的范围。 5.5 HDP材料的灭菌应引起聚合物摩尔质量或结构或两者的变化。这可能会影响材料或设备的初始机械和物理性能，以及随后的降解速率。因此，如果测试旨在代表实际性能 体内 ，样品应按照与最终装置一致的方式进行包装和灭菌。出于比较目的，可包括未灭菌样本。

1.1 This test method covers in vitro degradation of hydrolytically degradable polymers (HDP) intended for use in surgical implants. 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. 1.3 This test method 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 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 and health practices and determine the applicability of regulatory limitations prior to use. ====== 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 saline 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 (at 37°C in buffered saline) the actual 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 performace or degradation issues, or both. An example is the use of rigid foam block, which restricts swelling & expansion and can elevate pull out 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.