A needle assembly comprising: a hub; a needle fixed to said hub, said needle having a proximal end and a distal end, said distal end formed for insertion into a patient; a body in engagement with said hub so as to be movable relative thereto, said body having a distal end with an aperture formed therein configured to permit passage therethrough of said needle; a spring positioned between said hub and said body to contact said body and urge the body distally away from said hub; a cam track disposed on one of said body 16) or said hub and having a first track portion and a second track portion, and a cam follower on the other of said body or said hub received in said cam tack, said cam track and cam follower limiting relative axial movement between said body and said hub; characterized in said body is releasably retainable in a first position on said hub, with said cam follower positioned in said first track portion, where said distal end of said needle extends distally a first distance from said distal end of said body; said body being retainable in a second position on said hub, with said cam follower positioned in said second track portion, where said distal end of said needle extends distally a second distance from said distal end of said body, said second distance being less than said first distance, said hub is displaceable by said spring proximally relative to said body to urge said body from said first position to said second position; said cam track and said cam follower cooperating to permit distal axial movement of said body from said first position to said second position by said spring and by radial motion between said body and said hub to move the cam follower from the first track portion to the second track portion by said spring biasing said body from said first position to said second position. a hub; a needle fixed to said hub, said needle having a proximal end and a distal end, said distal end formed for insertion into a patient; a body in engagement with said hub so as to be movable relative thereto, said body having a distal end with an aperture formed therein configured to permit passage therethrough of said needle; a spring positioned between said hub and said body to contact said body and urge the body distally away from said hub; a cam track disposed on one of said body 16) or said hub and having a first track portion and a second track portion, and a cam follower on the other of said body or said hub received in said cam tack, said cam track and cam follower limiting relative axial movement between said body and said hub; characterized in said body is releasably retainable in a first position on said hub, with said cam follower positioned in said first track portion, where said distal end of said needle extends distally a first distance from said distal end of said body; said body being retainable in a second position on said hub, with said cam follower positioned in said second track portion, where said distal end of said needle extends distally a second distance from said distal end of said body, said second distance being less than said first distance, said hub is displaceable by said spring proximally relative to said body to urge said body from said first position to said second position; said cam track and said cam follower cooperating to permit distal axial movement of said body from said first position to said second position by said spring and by radial motion between said body and said hub to move the cam follower from the first track portion to the second track portion by said spring biasing said body from said first position to said second position.