Pietrzak William S, Eppley Barry L
Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 46581, USA.
J Craniofac Surg. 2007 May;18(3):540-5. doi: 10.1097/scs.0b013e318052fdeb.
Intraoperative heating of bioabsorbable plates and mesh panels to above the glass transition temperature is commonly performed to assist their adaptation to bone. Some studies suggest that once heat-adapted, such implants under certain conditions tend to partially revert to their preadapted shape, termed a "memory effect." We investigated this phenomenon by using heat-adapted 82:18 poly-L-lactic acid:polyglycolic acid copolymer mesh panel and plate specimens with a glass transition temperature of 57 degrees C. The specimens retained limited malleability even at temperatures as low as 45 degrees C, substantially below the nominal glass transition temperature, as measured by shape relaxation experiments. At 40 degrees C to 42 degrees C, however, shape relaxation was not observed. A three-dimensional synthetic bone construct was also fixated using 90 degrees C heat-adapted plates, then incubated in a 37 degrees C buffer bath for 4 weeks, with periodic measurement of the shape of the construct. No changes in shape were recorded over this interval, suggesting that heat-adapted bioabsorbable implants forming a three-dimensional fixation network with multiple bone fragments cannot independently shape relax with the overall interconnectedness of the network ensuring its stability over time.
术中将生物可吸收板和网片加热至高于玻璃化转变温度通常是为了帮助它们适应骨骼。一些研究表明，一旦经过热适应，此类植入物在某些条件下往往会部分恢复到其适应前的形状，这被称为“记忆效应”。我们通过使用玻璃化转变温度为57摄氏度的热适应82:18聚-L-乳酸：聚乙醇酸共聚物网片和板标本研究了这一现象。通过形状松弛实验测量，即使在低至45摄氏度（远低于标称玻璃化转变温度）的温度下，标本仍保留有限的延展性。然而，在40摄氏度至42摄氏度时，未观察到形状松弛。还使用90摄氏度热适应板固定了三维合成骨构建体，然后在37摄氏度的缓冲浴中孵育4周，定期测量构建体的形状。在此期间未记录到形状变化，这表明与多个骨碎片形成三维固定网络的热适应生物可吸收植入物不会随着网络的整体相互连接确保其随时间的稳定性而独立发生形状松弛。
