POTENTIAL APPLICATION OF A TRIAXIAL 3-DIMENSIONAL FABRIC (3-DF) AS ANIMPLANT

Various three-dimensional fabrics (3-DFs) woven with a triaxial three- dimensional (3A-3D) structure in which the warps, wefts and vertical f ibres are three-dimensionally orientated with orthogonal, off-angle, c ylindrical or complex fibre alignments using a single long fibre, whic h may be one of several kinds of fibres, have been developed. The phys ical strengths and behaviour of these fabrics under different external forces were measured for such stress-strain relationships as compress ive, tensile and cyclic bending, compressing torsional and compressive tensile systems to evaluate the effect of the continuous loading caus ed by living body movements over a long period of time. The 3-DFs led to downward convex 'J'-shaped curves in stress-strain profiles, becaus e they were markedly flexible at low strain levels, but became rigid a s strain increased. In this behaviour they reflected the behaviour of natural cartilage rather than that of conventional artificial biomater ials. There were also some 3-DFs that showed hysteresis loss curves wi th quite similar mechanical strengths and behaviour to natural interve rtebral discs with regard to the compressive-tensile cyclic stress and showed little variation from the first 'J'-shaped hysteresis profile even after 100, 000 deformation cycles. Accordingly, it has been shown that, without a doubt, 3-DFs can be effective implants possessing bot h design and mechanical biocompatibilities as well as the durability n ecessary for long-term implantation in the living body. The surface of bioinert linear low-density polyethylene coating on multifilaments of ultra-high molecular weight polyethylene, a constructional fibre of 3 A-3D weaving, was modified by treatment with corona-discharge and spra y-coating of unsintered hydroxyapatite powder to impart chemical (surf ace) compatibility and biological activity, respectively. Since the mo dified surface of the 3-DF was ascertained to have affinity and activi ty with simulated body fluid, an orthogonal 3-DF block was implanted i n the tibia of a rabbit. Sufficient surrounding tissues entering into the textural space of the 3-DF could be observed at 4 weeks after impl antation and the load necessary to break the block away from the bone reached a high value at 8 weeks. These results decisively showed that the 3-DFs could also acquire chemical (surface) and biological biocomp atibilities and bonding capacity with bone and soft tissues through mo dification of the surface of the constructional fibre. The 3-DFs have definite potential in such applications as novel and effective artific ial articular cartilages, intervertebral discs, menisci and materials for osteosynthesis and prosthesis, and the like. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.