An apparatus for operating on tissue comprises a shaft, an acoustic waveguide, and an end effector. The acoustic waveguide extends along the shaft and is configured to transmit ultrasonic vibration. The end effector comprises an ultrasonic blade and a clamp arm. The ultrasonic blade is in acoustic communication with the acoustic waveguide. The clamp arm is pivotable toward the ultrasonic blade. The end effector defines a first longitudinal region and a second longitudinal region. The end effector is configured to clamp tissue between the clamp arm and the ultrasonic blade in the first longitudinal region. The end effector is configured to sever tissue with the ultrasonic blade in the second longitudinal region.
