Eggli P S, Müller W, Schenk R K
Institute of Anatomy, University of Bern, Switzerland.
Clin Orthop Relat Res. 1988 Jul(232):127-38.
To investigate the histophysiology of implant degradation, hydroxyapatite and tricalcium phosphate cylinders with a diameter of 3 mm were implanted in the cancellous bone of the distal femur and the proximal tibia of 15 New Zealand White rabbits for up to six months. All implants had a homogeneous pore distribution and a porosity of 60%. Ceramics with a pore size range of 50-100 micron and 200-400 micron were compared. Morphometric analysis showed that up to 85.4% of the originally implanted tricalcium phosphate was degraded after six months, whereas the volume reduction of the hydroxyapatite was only 5.4% after the same period. Within the first months bone and tissue ingrowth and implant resorption occurred at a higher rate in the smaller-pored tricalcium phosphate than in the larger-pored material. Hydroxyapatite cylinders with small pores were totally infiltrated by bone or bone marrow after four months, whereas in the larger-pored hydroxyapatite implants tissue did not penetrate all pores after six months and the amount of bone within the implant was small. Scanning electron microscopy of the material before implantation revealed the existence of numerous pore interconnections with diameters of about 20 micron in the smaller-pored ceramics. Such interconnections were rare in the larger-pored implants. The pore interconnections seem to promote vascular and tissue ingrowth and consequently the initial rate of implant resorption. Implant resorption is an active process and involves two different cell types. Acid phosphatase-positive osteoclast-like cells suggesting active resorption adhere directly to the surface, especially in tricalcium phosphate implants. Clusters of macrophages tightly packed with granular material are found in the pores and along the perimeter of all implant cylinders. They may play an active role in the intracellular degradation of small detached ceramic particles.
为研究植入物降解的组织生理学，将直径3毫米的羟基磷灰石和磷酸三钙圆柱体植入15只新西兰白兔股骨远端和胫骨近端的松质骨中，长达6个月。所有植入物的孔隙分布均匀，孔隙率为60%。比较了孔径范围为50 - 100微米和200 - 400微米的陶瓷。形态计量分析表明，6个月后，最初植入的磷酸三钙高达85.4%发生降解，而同期羟基磷灰石的体积减少仅为5.4%。在最初几个月内，小孔径磷酸三钙中骨和组织向内生长以及植入物吸收的速率高于大孔径材料。4个月后，小孔径羟基磷灰石圆柱体完全被骨或骨髓浸润，而大孔径羟基磷灰石植入物在6个月后组织并未穿透所有孔隙，植入物内的骨量较少。植入前材料的扫描电子显微镜显示，小孔径陶瓷中存在许多直径约20微米的孔隙互连。这种互连在大孔径植入物中很少见。孔隙互连似乎促进了血管和组织向内生长，从而促进了植入物吸收的初始速率。植入物吸收是一个活跃的过程，涉及两种不同的细胞类型。提示活跃吸收的酸性磷酸酶阳性破骨细胞样细胞直接附着在表面，尤其是在磷酸三钙植入物中。在所有植入圆柱体的孔隙中和周边发现紧密堆积有颗粒物质的巨噬细胞簇。它们可能在小的游离陶瓷颗粒的细胞内降解中起积极作用。
