Tissue response to polyglycolide, polydioxanone, polylevolactide, and metallic pins in cancellous bone: An experimental study on rabbits

Abstract

The purpose of this study was to investigate, qualitatively and histoquantitatively, the tissue response of rabbit femur cancellous bone to polyglycolide (PGA), polydioxanone (PDS), polylevolactide (PLLA), and stainless steel pins under identical conditions. Eighty knees in 50 rabbits were operated on by inserting bioabsorbable pins (PGA, PDS, or PLLA) together with metallic Kirschner wire in 60, and two metallic Kirschner wires alone in 20 knees, while 20 knees served as intact controls. Follow-up times were 3, 6, 12, 24, and 52 weeks. Cancellous bone tissue response to implants was studied using histological, histomorphometrical, microradiographical, and oxytetracycline fluorescence methods. Residual fragments of PGA and PDS were seen at 24 weeks. Complete degradation of these polymers had taken place before 52 weeks. No signs of degradation of the PLLA pins were observed within the entire follow-up period. The osteoid formation surfaces at tissue implant-interface were statistically larger in all test groups as compared to intact controls. The number of macrophages at tissue implant-interfaces increased in all bioabsorbable implant specimens until 6 weeks, and with PGA until 12 weeks. No differences in the osseous response emerged when comparing groups of bioabsorbable implants with each other or with stainless steel group. Bioabsorbable pins and metallic Kirschner wires evoked an osteoconductive response in the cancellous bone surrounding implant, but the response intensity between implants displayed no differences. This suggests a simple, nonspecific walling-off new-bone front type of response. Consequently, the polymers possessed no specific osteostimulatory or osteoinhibitory properties. Within the follow-up, no significant differences in biocompatibility between the implants appeared, and no frank inflammatory foreign-body reactions occurred. The smallvolume pins obviously did not exceed the local tissue tolerance and clearing capacity of the bone.

Osseous alterations at the interface of hydrogel expanders and underlying bone

“…In contrast, our own analyses revealed that hydroxyapatite density decreases significantly if the expander is applied directly to the bone. Any influence of the PDS foil on the bone is not to be expected in the analyses (Baumann et al, 2002;Pihlajamaki et al, 2006). Since this effect rarely occurs when there is no fluid intake by the expander and the PDS foil is applied to the bone, it can be concluded that the various restructuring processes with otherwise identical test structures are due exclusively to the local fluid depletion caused by the expander.…”

Biocompatibility and degradation behaviour of degradable magnesium sponges coated with bioglass – method establishment within the framework of a pilot study

“…However, most of them have limitations, mostly due to foreign body reaction or inappropriate mechanical properties [4, 5, 8, 9, 12 -14]. Widely used polymers have good results before degradation [15], but unspecific inflammation due to acidic degradation products and osteolysis can occur after longer implantation times [14,16].…”

In vivo micro-CT scanning of a rabbit distal femur: Repeatability and reproducibility

“…Rabbits are also advantageous compared to rats because they exhibit a predictable cessation of longitudinal bone growth after five to six months (Kaweblum et al, 1994) and should not require special processing of images to account for growth as seen with rats (Waarsing et al, 2004a). In vivo micro-CT scanning of rabbits will also complement studies involving bone graft incorporation, implant bone interfaces, and skeletal assessment which commonly use the rabbit femur model (Laffargue et al, 1999;Orr et al, 2001;Ohsawa et al, 2004;Voor et al, 2004;Bourne and van der Meulen, 2004;Saha and Wehrli, 2004;Pihlajamaki et al, 2006a;Pihlajamaki et al, 2006b;Dallari et al, 2006;Fellah et al, 2006;Takahashi et al, 2006;Wang et al, 2006;van der Meulen et al, 2006).…”