Methods and apparatus for treating bones, including, in one or more embodiments, a device for delivering a bone filler material comprising: a housing having a throughbore; a plunger comprising a shaft having external threads, wherein the plunger is configured for advancement through the throughbore of the housing; and a threaded receiving member configured to releasably engage the plunger. Methods for removing an instrument from a vertebral body comprising applying ultrasonic energy to the instrument, wherein a distal end of the instrument is disposed in a cavity in the vertebral body, wherein the cavity contains a filler material; and removing the instrument from the vertebral body.