Implantation sites and fiber diameters affect the rate of degradation in absorbable polydioxanone fibers

Abstract

Purpose: The purpose of this study is to test the question of whether implantation sites and fiber diameters affect the rate of degradation in absorbable polydioxanone fibers. Type of Study: Randomized trial. Methods: Forty-eight mature rabbits were used. In the first study, using 24 rabbits, a 0.3-mm diameter polydioxanone fiber was implanted into the subcutaneous, intra-articular, and intramedullary sites. Six rabbits each were killed at 1, 2, 3, and 6 weeks after surgery. In the second study, the remaining 24 rabbits were divided into 2 groups of 12 animals each. In group I, a 0.3-mm diameter fiber was implanted into the intramedullary and subcutaneous sites. In group II, a 0.6-mm diameter fiber was implanted in the same manner. In each group, 6 rabbits were killed at 3 and 6 weeks. In each study, all fiber specimens underwent tensile testing to determine the material properties. We defined the percentage of the maximum load of each fiber specimen compared with the normal control value as the I/N ratio. Results: In the first study, the maximum load and the stiffness of the fibers implanted into the intramedullary site were significantly lower than those of the fibers implanted into the other 2 sites at each period ( P < .0001). In the second study, the I/N ratio of group I was significantly less than that of group II at each implanted site ( P < .0001). Conclusions: Polydioxanone fiber implanted into the intramedullary site deteriorates more rapidly than that implanted into the subcutaneous and the intra-articular sites. Thin fibers deteriorate more rapidly than thick fibers. Therefore, the degradation of absorbable synthetic fibers intended for use in ligament reconstruction should be evaluated not only in the subcutaneous site but also in the intramedullary site using various diameter fibers.