US Patent 10232129 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 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 threads 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.