Deformation resistance in soft tissue cutting: a parametric study

Characterizing and modeling of soft tissue deformation during cutting is important for developing a reality based haptic interaction model for surgical training and simulation. In this study, soft tissue cutting experiments were performed (ex-vivo) while monitoring the cutting forces and blade displacement for various cutting speeds (ranging from 0.1cm/sec-2.54cm/sec) and cutting angles (for 0° and 45° cutting angle). The measured force-displacement curves in all cases exhibit a characteristic pattern: repeating units formed by a segment of linear loading (deformation of tissue) and immediately followed by a segment of sudden unloading (localized crack extension in the tissue). This paper addresses the characterization of the deformation resistance during the deformation segment. The variation of this deformation resistance with cutting parameters is also determined. The deformation resistance to the cutting blade was quantified via a quantity designed as the local effective modulus (LEM) of the tissue. For a given cutting speed, the deformation resistance decreases as the cutting angle is varied from 0° to 45°. For each cutting angle, the deformation resistance decreases with cutting speed. The variation of deformation resistance versus cutting speed is linear at 0° cutting angle and is nonlinear at 45° cutting angle.