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This article summarizes the contributions in research on tissue cutting with needles. The geometry of the needle's cutting edges was analytically defined and expressions for the inclination and rake angles of hollow and solid needles and trocars have been derived. Based on the semi-empirical method, finite element model and the fracture mechanics approach, force models of needle insertion were developed. The relationship between the needle's tip geometry and insertion force was established and used in several applications. It was shown, for example, that the cutting edge of the lancet needle can be optimally designed to minimize insertion force or bevel length. The cutting mechanics in rotary needle insertion was investigated along with the exploration of improvements of needle biopsy performance by decreasing the needle cutting and friction forces. The deflections of the needle during insertion were measured to develop a strategy for guiding the needle to the right position in brachytherapy and drug delivery. From an overall perspective, fundamental advances and application problems based on the cutting mechanics of soft tissue for needle were highlighted to lay the foundation for developments of biomedical device and improvements of healthcare procedures. [ABSTRACT FROM PUBLISHER]

Abstract: Tissue cutting by a needle is greatly influenced by the geometry of its cutting edges. Yet, there are very few results in the technical literature that address the issues surrounding the relation between needle tip and cutting edge geometry and its cutting/insertion force. In the present paper, general mathematical models of the included and inclination angles of a needle''s cutting edge are formulated since they exert a profound influence on cutting behavior. Specific models for various tip geometries are developed to investigate four types of needle tips including one-plane, asymmetric three-plane, symmetric multi-plane, and symmetric three-curved-surface needles. The results show that the cutting edge of the one-plane needle has a very undesirable configuration. Asymmetric three-plane needles, such as the lancet and back bevel tip needles, can significantly improve the configuration of the cutting edge. Back bevel tip needles, in turn, offer even more desirable cutting edge geometry than lancet tip needles. In evaluating the cutting edge angles of multi-plane needles, it was shown that the included angle is limited by its tip geometry. To resolve this problem a needle formed by three curved surfaces was proposed. It was found that this new design has significant potential for reducing patient trauma as well as target accuracy during needle insertion. The proposed general approach provides the foundation for designing medical needles with specific cutting edge properties. [Copyright &y& Elsevier]