Injection device

Abstract

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.