INTERFACE REACTIONS TO PEO PBT COPOLYMERS (POLYACTIVE(R)) AFTER IMPLANTATION IN CORTICAL BONE/

The bone reaction at the interface of a range of PEO/PBT copolymers (P olyactive(R)) 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, evalu ated qualitatively, and quantified with the aid of an image analysis s ystem. The percentage of bone contact was determined morphometrically for all PEO/PBT proportions; for the 70/30 ratio, the percentage of ca lcification 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 copo lymers possess hydrogelic properties, and a direct relation has been e stablished 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 7 0/30 revealed higher percentages of bone contact (over 80%) when compa red with the other ratios (60/40, 55/45, 40/60, and 30/70). This diffe rence was statistically confirmed 1 year postoperatively. The material s with the higher PEO contents showed the highest amounts of calcifica tion, which is reflected by the rate of bone-bonding (70% of bone-bond ing for the 70/30 at 52 weeks). Calcification and bone-bonding were no t observed for 40/60 and 30/70 proportions. The quantitative results c onfirmed the relation between PEO content, water-uptake, calcification , and bone-bonding. It was furthermore demonstrated that PEO/PBT copol ymers initially establish a high degree of bone contact, whereas the b one-bonding properties, especially of the 70/30, accomplish a long-ter m implant fixation. (C) 1994 John Wiley and Sons, Inc.