Method and instrument for surgical delivery of biocompatible materials

A surgical instrument includes an elongated cannula having a forward expulsion end and a rearward breach end, arranged to include a bio-compatible material; a drive member arranged to urge the bio-compatible material in a reciprocating motion having two alternating phases; and a directional brake disposed to contact the bio-compatible material. The directional brake has a preferred braking direction for resisting motion of the bio-compatible material. The preferred braking direction of the directional brake is oriented to resist retreat of said material during the retreating phase and to allow advance of said material during the advancing phase, thus producing a net advance of the material to expel it from the expulsion end. The directional brake is disposed nearer to the expulsion end than the breach end of the instrument, to prevent undesired axial compression of the bio-compatible material during ejection.