A flexible inner member for being rotatably disposed in an angled outer tubular member of a rotary tissue cutting instrument has a flexible region composed of a series of partial circumferential cuts formed through the wall of a tubular body of the inner member. Each cut extends along an arc that defines part of the external circumference of the tubular body. The cuts are uniformly longitudinally spaced in succession along the length of the tubular body corresponding to the flexible region. The cuts are parallel to one another and perpendicular to a central longitudinal axis of the tubular body. The cuts are grouped in duplicative patterns that repeat along the length of the flexible region, there being at least two successive cuts in each pattern. The cuts of each pattern are rotationally offset in succession in a rotational direction about the central longitudinal axis of the tubular body.
