Walton Mark, Cotton Nicholas J
Department of Orthopedic Surgery, University of Otago, Dunedin School of Medicine, Dunedin, Otago, New Zealand.
J Biomater Appl. 2007 Apr;21(4):395-411. doi: 10.1177/0885328206065125. Epub 2006 May 9.
The use of absorbable orthopedic implants has increased substantially during the last decade. Currently, most of them are fabricated from poly-L-lactide (PLLA), its co-polymers, or mixtures with other constituents. In vivo, PLLA persists for years after its surgical role has ended, which is confirmed by a long-term histological study of PLLA implanted in sheep either as functional interference screws or nonfunctional rods. The first tissue reaction is the sequestration of the implant within new bone during the initial 3 months. After a nonreactive period, a second tissue reaction is associated with the early signs of structural disintegration of the PLLA at 1 year. Subsequently, as the polymer mass reduces, it is replaced by a relatively avascular fibrous tissue containing macrophages and having an occasional multinucleated giant cell on the implant surface. After 3 years much of the polymer is still present, although as isolated fragments. The tissue reactions can be explained in terms of the physical chemistry of PLLA degradation. Though biocompatible, the excessive longevity of PLLA and the absence of its replacement by bone, indicates that despite being satisfactory clinically, it is not an ideal implant material, and that improved absorbable materials need to be developed.
在过去十年中，可吸收骨科植入物的使用大幅增加。目前，大多数可吸收骨科植入物由聚-L-丙交酯（PLLA）、其共聚物或与其他成分的混合物制成。在体内，PLLA在其手术作用结束后会持续存在数年，这一点已通过对植入绵羊体内的PLLA进行长期组织学研究得到证实，PLLA在绵羊体内分别作为功能性干扰螺钉或非功能性棒材植入。最初的组织反应是在最初3个月内植入物被新骨包埋。经过一段无反应期后，第二种组织反应与1年后PLLA结构崩解的早期迹象相关。随后，随着聚合物质量的减少，它被一种相对无血管的纤维组织取代，该纤维组织含有巨噬细胞，在植入物表面偶尔会有单核巨细胞。3年后，尽管聚合物已成为孤立的碎片，但仍有大量聚合物存在。组织反应可以用PLLA降解的物理化学来解释。尽管PLLA具有生物相容性，但其过长的存留时间以及未被骨组织替代的情况表明，尽管它在临床上令人满意，但它并不是一种理想的植入材料，因此需要开发性能更优的可吸收材料。
