Reaktion auf Nanoapatit-haltige Implantate mit pharmakologisch aktivem Polymer

Abstract

We investigated a new group of nanocrystalline hydroxyapatite (HA) with an organic component. The HA had the same crystal dimensions as in human bone, which is known to facilitate the cellular degradation. The organic component allowed the binding of pharmacologic active substances and the controlled release after implantation as well as a control of the degradation rate of the HA. HA was coprecipitated and photopolymerized containing the Makropolymer Indomethacin/Tyrosin/HEMA (Indo-OA), and as controls containing Poly-HEMA (HEMA-OA) alone or Poly-L-Lysin (PLL-OA). These were investigated in a standardized rabbit-model with a critical-size-defect in spongy bone. The host-and material response were examinated after 7, 28 and 84 days (d) using histology, histomorphometry, electronmicroscopy and in-situ-hybridisation techniques. Nanocrystalline HA was similarly bonded and subjected to remodelling like normal bone. The biological behavior of HA was strongly influenced by the added organic polymer. Indo-OA showed the weakest inflammatory reaction, the smallest amount of fibrous tissue, the fastest incorporation in bone and the highest amount of bone-contact and number of osteoclast-like-cells at the interface after 7 and 28d. On a molecular basis it showed an acceleration and increase of bone-formation as compared to the empty-hole-controlled and the other materials. After 84d it showed less bone-contact as HEMA-OA, mostly because 2 of 6 implants prepared for lightmicroscopic evaluation showed nearly no bone-contact. One of those showed signs of chronic infection. The weak mechanic properties of the nanocristalline HA could be improved by adding the organic component. The MEMA-OA implants appeared to be the most stable ones. HEMA-OA (as the anchor-substance for indomethacin in the HA) had no negative influence on bone metabolism. PLL-OA is unfavourable because it showed the strongest inflammatory reaction, surface erosion and implant-fragmentation as well as the lowest bone-contact at the interface. (orig.)SIGLEAvailable from: http://diss.fu-berlin.de/2003/321/index.html / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman