A locking hinge assembly for an injector is disclosed. The injector includes a forward handle member, a rear handle member and a hinge connecting the first and second members and defining an axis of rotation. The locking hinge assembly includes a hinge element slidable along the axis of rotation between a locked position and an unlocked position. The hinge element is coupled to the forward handle member and the rear handle member at the hinge, and the hinge element includes at least one groove. Additionally, a locking element is provided and positioned about the hinge. The locking element is configured to be received in the groove such that rotation of the forward handle member and rear handle member about the axis of rotation is prevented when the hinge element is in the locked configuration.