The present invention is directed to material removal instrument (100) for forming cavities in interior body regions, particularly cavities in intervertebral discs and vertebrae. The instrument includes a cannula (120) and a rotation mechanism (140) disposed at least partially within the cannula. A cutting element extends from the rotation mechanism and impacts and dislocates tissue as the rotation mechanism is rotated within the body. The cutting element can be a blade (146), a thread (256), a mass element (346), or an expandable cutting element (446). Dislocated tissue is withdrawn from the body via the cannula.
