Lewandrowski Kai-Uwe, Bondre Shrikar P, Wise Donald L, Trantolo Debra J
Orthopaedic Research Laboratories, Massachusetts General Hospital, Boston, MA 02114, USA.
Biomed Mater Eng. 2002;12(3):259-70.
The tissue response of subchondral bone to a biodegradable fixation device manufactured in the shape of a screw and made of polylactide with a hydroxyapatite buffer were implanted through the articular surface of the intercondylar portion of the distal rabbit femur. One screw was implanted per animal. The screws had a core diameter of 3.2 mm and an outer diameter of 4.5 mm. At insertion, the implants were cut flush with the articular surface. After follow-up times of 8 and 16 weeks, the specimens were examined radiographically and histomorphometrically. The intact contralateral femur served as a control for comparison. Only minimal signs of degradation of the polymer could be seen in the histologic specimens. These implant degradation sites were commonly areas of new bone formation adjacent to the screw implant. A brim of repair tissue was formed at the entrance and exit of the implant channel. The width of the repair tissue from the tissue-implant boundary towards the center of the entrance hole varied greatly between the specimens, from 80 to 750 microm. In most specimens this bridging tissue consisted of newly formed bone and undifferentiated mesenchymal tissue. Degenerative chondrocyte clustering occurred in the pre-existing cartilage within a 400 microm wide zone from the tissue-implant interface into the recipient tissues. Some new-bone formation was seen to envelop the implant in all specimens, but the fractional osteoid formation surface of the trabeculae was only significantly higher in the screw-implanted 16-week specimens, when compared to the non-operated contralateral controls. Although the bony osteotomy was invariably healed in all specimens with good implant integration, the quality and quantity of the reparative tissue of the articular cartilage near the screw hole was variable. This study showed that large polylactide implants, which are buffered with hydroxyapatite show benign tissue responses and good implant osteointegration when implanted in bone. They may be suitable for fixation of small bone fractures. However, insertion through intra-articular surfaces may require further improvement of the implant material to avoid the degenerative repair processes seen in this study.
将一种呈螺钉形状、由聚丙交酯与羟基磷灰石缓冲层制成的可生物降解固定装置，通过兔股骨远端髁间部分的关节面植入，观察软骨下骨的组织反应。每只动物植入一枚螺钉。螺钉的芯直径为3.2毫米，外径为4.5毫米。植入时，将植入物与关节面齐平切断。在随访8周和16周后，对标本进行放射学和组织形态计量学检查。完整的对侧股骨作为对照进行比较。在组织学标本中仅可见聚合物有极少的降解迹象。这些植入物降解部位通常是靠近螺钉植入物的新骨形成区域。在植入通道的入口和出口处形成了一层修复组织边缘。从组织 - 植入物边界到入口孔中心的修复组织宽度在不同标本之间差异很大，从80到750微米不等。在大多数标本中，这种桥接组织由新形成的骨和未分化的间充质组织组成。在距组织 - 植入物界面400微米宽的区域内，从预先存在的软骨到受体组织中出现了退行性软骨细胞聚集。在所有标本中均可见一些新骨形成包裹植入物，但与未手术的对侧对照相比，仅在植入螺钉16周的标本中，小梁的类骨质形成表面分数显著更高。尽管所有标本中的骨切开术均顺利愈合且植入物整合良好，但螺钉孔附近关节软骨修复组织的质量和数量存在差异。本研究表明，用羟基磷灰石缓冲的大型聚丙交酯植入物植入骨内时表现出良性组织反应和良好的植入物骨整合。它们可能适用于小骨折的固定。然而，通过关节内表面插入可能需要进一步改进植入材料，以避免本研究中所见的退行性修复过程。
