INJECTION DEVICE
An injection device includes a syringe having a body with a piston disposed therein with an open end along with a viscous fluid disposed in the body for injection by the piston. A needle assembly is provided which includes a cannula, for example a blunt tipped cannula, having a luer connection engageable with the syringe distal end with the luer connector including a hub. Mating engagement is provided by way of internal threads at the syringe distal end and external treads of a hub with a pitch sufficient to prevent detachment of the hub from the syringe distal end during ejection of the viscous fluid. In addition, a stepped cavity, disposed in the hub, further prevents detachment of the hub from the syringe distal end during ejection of the viscous fluid.
1 . A injection device comprising:
a needle assembly comprising a cannula and a luer connector engageable with a distal end of a syringe, said cannula having a rounded distal tip and an outlet spaced apart from said tip, and said luer connector comprising a hub with a distal end supporting said cannula and a proximal end mateable with the syringe distal end;
a cavity, defined by a stepped interior surface of the hub, effective to prevent detachment of said hub from the syringe distal end during ejection of a viscous fluid from the cannula outlet when the hub is engaged to the syringe distal end; and
external threads disposed on an exterior surface of said hub enabling mating engagement between the hub and the syringe distal end.
2 . The device of claim 1 wherein the stepped cavity provides a reduced dead space relative to an otherwise identical needle assembly without the stepped interior surface.
3 . The device according to claim 1 wherein the external threads has a pitch of about 3 mM.
4 . The device according to claim 3 wherein the external threads comprise double lead screw threads.
5 . The device according to claim 4 wherein the external threads comprise single circumference double lead screw threads.
6 . The injection device of claim 7 wherein the cannula has a gauge greater than 21.
7 . The injection device of claim 1 wherein the cannula has a gauge greater than 25.
8 . The injection device of claim 1 wherein the cannula has a gauge greater than 30.
9 . The injection device of claim 1 wherein the cannula has a gauge of up to about 32.
10 . An injection device comprising:
a syringe having a body with a piston disposed therein and a distal end;
a needle assembly comprising a cannula and a luer connector engageable with the syringe distal end, said cannula having a rounded distal tip and an outlet spaced apart from said tip, and said luer connector comprising a hub with a distal end supporting said cannula and a proximal end mateable with the syringe distal end;
a cavity, defined by a stepped interior surface of the hub, effective to prevent detachment of said hub from the syringe distal end during ejection of a viscous fluid from the cannula outlet when the hub is engaged to the syringe distal end; and
external threads disposed on an exterior surface of said hub enabling mating engagement between the hub and the syringe distal end.
11 . The injection device of claim 10 wherein the cannula has a gauge greater than 21.
12 . The injection device of claim 10 wherein the cannula has a gauge greater than 25.
13 . The injection device of claim 10 wherein the cannula has a gauge greater than 30.
14 . The injection device of claim 10 wherein the cannula has a gauge of up to about 32.
15 . The injection device of claim 10 further comprising viscous fluid disposed in said body and injectable by said piston through said cannula.
16 . The injection device of claim 15 wherein the fluid is a dermal filler.
17 . The injection device of claim 10 further comprising internal threads disposed in the syringe distal end enabling mating engagement of the hub external threads and the syringe distal end.
18 . The injection device of claim 10 wherein the external threads have a pitch of about 3 mM.
19 . The device according to claim 10 wherein the external threads comprise double lead screw threads.
20 . The device according to claim 10 wherein the external threads comprise single circumference double lead screw threads.