An assembly for performing an electrosurgical procedure. A cannula includes a cannula hub defining a middle bore having a smaller diameter than a proximal bore. An electrode includes an electrode head having an outer diameter smaller than the proximal bore and greater than the middle bore. A syringe includes a syringe head having a length sufficient to extend past the proximal bore, and an outer diameter sized to engage the middle bore to form an annular seal at an interface between the syringe and the cannula. A step may define a transition surface between the proximal bore and the middle bore, and at least one notch may be within the step to maintain fluid communication between the middle bore and the proximal bore when the electrode head is engaging the step. The cannula head may include first and second locking features configured to engage the syringe and electrode, respectively.
