Variable‐Curvature Bending Characteristic and Kinematic Model of Cannula Flexible Needle

BACKGROUND: Compared with the conventional bevel-tip flexible needles, the cannula flexible needle has a superiority in terms of agility. To improve the insertion accuracy of the cannula flexible needle in the soft tissue, the variable-curvature bending characteristics were explored and a kinematic model was developed. METHODS: This paper identified the parameters that influence the needle bending using a combination of the dimensional analysis theory and the equivalent stiffness method. Based on this, a kinematic model was established considering the deviation and rebound of the needle shaft. Verification experiments with the different stylet extension lengths for the flexible needle were conducted. Moreover, the single-arc and the double-arc insertion experiments were performed. RESULTS: The results showed that all errors were within 2 mm, which met the accuracy requirements of general clinical surgery. CONCLUSIONS: The rationality and accuracy of the proposed variable-curvature bending characteristic model and the kinematic model are validated by experiments.