Trowbridge E A, Lawford P V, Crofts C E
Department of Medical Physics, Royal Hallamshire Hospital, University of Sheffield, UK.
J Biomed Eng. 1989 Jul;11(4):311-4. doi: 10.1016/0141-5425(89)90065-4.
The force required to pull sutures out of glutaraldehyde fixed bovine pericardium, for four different suture bites: 0.5 mm, 1 mm, 1.5 mm and 2.0 mm, was compared with the tissue strength. The mean suture pull-out force was significantly lower than the tissue strength for all bites, with a minimum value of 2.86 +/- 1.02 N for the 0.5 mm bite and a maximum value of 6.32 +/- 0.77 N for the 2.0 mm bite. The mean force which produced failure of the chemically modified pericardium was 15.49 +/- 8.48 N. The mean force at pull-out of the sutures lay on a regression line: force at failure = 1.68 + 2.25 x Bite. A video film of the experiments showed that the suture does not cut through the pericardium. It pulls a V-shaped band of collagen fibre bundles through the stationary pericardium. Eventually this band breaks away from the free edge of the tissue specimen. The specimens under uniaxial load failed by laminate debonding of two layers of tissue, rupture of the serosal surface layer followed by shear and fibre slippage. These results indicate that any suture which bears load, during the normal functioning of a heart valve substitute, will be a source of weakness, compared to the overall tissue strength. As a consequence the alignment/holding suture of the Standard Ionescu-Shiley valve and the modified stitch of the low profile valve are likely to be potential sites of fatigue failure.
针对四种不同缝线咬边深度（0.5毫米、1毫米、1.5毫米和2.0毫米），将从戊二醛固定的牛心包中拔出缝线所需的力与组织强度进行了比较。所有咬边深度下，缝线的平均拔出力均显著低于组织强度，0.5毫米咬边深度时的最小值为2.86±1.02牛，2.0毫米咬边深度时的最大值为6.32±0.77牛。导致化学改性心包失效的平均力为15.49±8.48牛。缝线拔出时的平均力落在一条回归线上：失效时的力 = 1.68 + 2.25×咬边深度。实验视频显示，缝线不会割破心包。它会拉动一条V形胶原纤维束带穿过固定的心包。最终，这条带会从组织标本的自由边缘脱离。在单轴载荷下，标本通过两层组织的层间剥离、浆膜表层破裂，随后发生剪切和纤维滑动而失效。这些结果表明，在心脏瓣膜替代品的正常功能过程中，任何承受载荷的缝线与整体组织强度相比，都将是一个薄弱点。因此，标准伊奥内斯库-希利瓣膜的定位/固定缝线以及低轮廓瓣膜的改良缝线很可能是疲劳失效的潜在部位。
