The bone reaction at the interface of a range of PEO/PBT copolymers (Polyactive) after press-fit implantation in the diaphyseal femur of 20 goats was investigated. The animals were sacrificed at 1, 4, 12, 26, and 52 weeks. Undecalcified histologic sections were prepared, evaluated qualitatively, and quantified with the aid of an image analysis system. The percentage of bone contact was determined morphometrically for all PEO/PBT proportions; for the 70/30 ratio, the percentage of calcification of the material surface and of bone-bonding (defined as a continuum at the light microscopic level between calcification within the material surface and bone tissue) were also assessed. PEO/PBT copolymers possess hydrogelic properties, and a direct relation has been established between water-uptake and PEO content. The swelling behavior of all PEO/PBT substrates resulted in a high degree of bone contact (over 95%) at early stages. From the 12-week survival time onward the 70/30 revealed higher percentages of bone contact (over 80%) when compared with the other ratios (60/40, 55/45, 40/60, and 30/70). This difference was statistically confirmed 1 year postoperatively. The materials with the higher PEO contents showed the highest amounts of calcification, which is reflected by the rate of bone-bonding (70% of bone-bonding for the 70/30 at 52 weeks). Calcification and bone-bonding were not observed for 40/60 and 30/70 proportions. The quantitative results confirmed the relation between PEO content, water-uptake, calcification, and bone-bonding. It was furthermore demonstrated that PEO/PBT copolymers initially establish a high degree of bone contact, whereas the bone-bonding properties, especially of the 70/30, accomplish a long-term implant fixation.

A range of polyethylene oxide1polybutylene terephthalate (PEO1PBT) copolymers (7&30% PEO) was investigated for nonloadbearing bone replacement application. Porous PEO1PBT cylinders (d = 5 mm, h = 7 mm) were implanted transcortically in the diaphyseal femur of 10 goats, and the animals were sacrificed at 3, 6, 9, 12, and 26 weeks. Qualitative evaluation was performed using light and fluorescence microscopy, scanning electron microscopy, and backscatter electron imaging with an attached X-ray microanalysis system. The percentage of bone ingrowth and the percentage of bone contact in the pore region were quantitatively assessed using undecalcified histological sections. The hydrogel properties of the PEO1PBT copolymers provided a rapid closure of the defect upon press-fit implantation, due to postoperative water uptake and subsequent swelling behavior of the materials. Bridging of the defect by bone and the occurrence of bone bonding were observed 6 weeks postoperatively for the material with the highest PEO content (70130). For the 60140 and 55145 PEO1PBT proportions, union of the defect and bone bonding were observed at 9 and 12 weeks, respectively. The stiffer 40160 and 30170 PEO1PBT implants showed bridging of the 5-mm gap after 12 weeks, but did not reveal bone bonding up to 26 weeks. Peripheral fragmentation, mainly in the marrow cavity, was found for the 70130 material at 12 weeks and had increased at 26 weeks. Degradation was not seen for the other materials. The histomorphometrical data confirmed the microscopical observations and demonstrated a direct relation between PEO content in the PEO1PBT copolymers, the rate of bone ingrowth, and the amount of bone contact. Porous PEO/PBT copolymers are degradable, bone-bonding elastomeric substrates with favorable handling properties and a high percentage of bone ingrowth (69-78 at 26 weeks). It was therefore concluded that PEO1 PBT copolymers are highly promising materials for bonereplacement surgery.

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A range of polyethylene oxide/polybutylene terephthalate (PEO/PBT) copolymers (70-30% PEO) was investigated for nonloadbearing bone replacement application. Porous PEO/PBT cylinders (d = 5 mm, h = 7 mm) were implanted transcortically in the diaphyseal femur of 10 goats, and the animals were sacrificed at 3, 6, 9, 12, and 26 weeks. Qualitative evaluation was performed using light and fluorescence microscopy, scanning electron microscopy, and back-scatter electron imaging with an attached X-ray microanalysis system. The percentage of bone ingrowth and the percentage of bone contact in the pore region were quantitatively assessed using undecalcified histological sections. The hydrogel properties of the PEO/PBT copolymers provided a rapid closure of the defect upon press-fit implantation, due to postoperative water uptake and subsequent swelling behavior of the materials. Bridging of the defect by bone and the occurrence of bone bonding were observed 6 weeks postoperatively for the material with the highest PEO content (70/30). For the 60/40 and 55/45 PEO/PBT proportions, union of the defect and bone bonding were observed at 9 and 12 weeks, respectively. The stiffer 40/60 and 30/70 PEO/PBT implants showed bridging of the 5-mm gap after 12 weeks, but did not reveal bone bonding up to 26 weeks. Peripheral fragmentation, mainly in the marrow cavity, was found for the 70/30 material at 12 weeks and had increased at 26 weeks. Degradation was not seen for the other materials. The histomorphometrical data confirmed the microscopical observations and demonstrated a direct relation between PEO content in the PEO/PBT co-polymers, the rate of bone ingrowth, and the amount of bone contact. Porous PEO/PBT copolymers are degradable, bone-bonding elastomeric substrates with favorable handling properties and a high percentage of bone ingrowth (69-78 at 26 weeks). It was therefore concluded that PEO/ PBT copolymers are highly promising materials for bone-replacement surgery.