The electromechanical impactor is a 3.0F electrohydraulic electrode within a stainless steel sheath attached to a distal compression spring with a conical titanium tip. Eac electrical discharge causes a 2.7 mm. tip extension and a kinetic impact energy of 900 bar. It is 5F, flexible and placed within the straight working port of a 9.5F to 10.OF rigid or semirigid ureteroscope. A clinical trial was performed and 15 patients (16 ureters with calculi) were treated with this device. An upper ureteral stone partially fragmented and migrated cephalad, 1 stone failed to break and was basket extracted, and there was 1 machine failure. The 13 other calculi were successfully broken to fragments less than 5 mm. In 2 patients baskets were also used to remove the larger monohydrate fragments. A secondary procedure was required to basket a 4 mm. calcium oxalate monohydrate fragment in a patient with 3 ureteral calculi. The average size of the calculi was 14 mm. in largest diameter. Excluding the machine failure, the average number of pulses required for fragmentation was 764. The life of each device was 600 to 800 pulses. Of the 15 cases 1 electrode was used in 10, 2 in 3 and 3 in 2. There was no evidence of ureteral wall injury, abrasion or perforation. The electromechanical impactor is a safe and effective method of ureteral stone fragmentation.
