ROTATIONAL MOULDING AND KNITTED FABRIC COMPOSITES IN THE DEVELOPMENT OF AN INTERVERTEBRAL DISC PROSTHESIS

Abstract

A number of joints in the body are hollow in nature. In addition, most biological tissues can be characterised by their 3 dimensional fibrous structure as well as their composition which is usually made up of heterogeneous materials. This is true for the natural intervertebral disc (IVD) which is a hollow, liquid-filled entity, reinforced by annular fibres. Taking a physiology simulation based approach, work in this project initiated with methods of optimising the process of rotational moulding for intervertebral disc prosthesis (IVDP) development. The application is warranted as a literature review revealed several shortcomings in existing prostheses or alternative forms of treatment. To reinforce the IVDP the approach taken was to develop thin and flexible knitted fabric elastomeric composites which could be used as reinforcement material for the IVDP. Knitted fabrics were chosen on the basis that they can retain high deformability while improving overall mechanical characteristics. An IVDP of a composite nature was successfully fabricated. It consists of an elastomeric core, encapsulated by two layers of interlock weft knitted polyester fabric-PU elastomeric composite. The PU elastomeric matrix in the composite was the same PU elastomer as that used in the IVDP core. Mechanical studies by compression testing revealed that the disc was within range of normal disc values. The development of thin, flexible composites has proved to be highly successful in terms of ease of processing (primarily by compression moulding) and mechanical properties of the composite material.