Gear mechanism to drive oscillating shaft

A cutting operation is performed with an apparatus having an elongated sleeve (24) with a port (30) in its distal section (28). The sleeve (24) is connected to a vacuum source and a rotating shaft (20) is disposed in the lumen (22) of the sleeve. The shaft (20) has a cutting blade (32) at its distal end opposite the port (30). The blade (32) has two cutting edges, a gear assembly (18) operative to alternately rotate the shaft (20) in a first direction and a second direction about the axis of symmetry of the shaft (20), and a motor (14) for powering the gear assembly (18).