An Er:YAG laser endoscopic fiber delivery system for lithotripsy of salivary stones

Abstract

Background and objectives: Endoscopic applications of Erbium:YAG lasers are still very limited due to lack of appropriate fiber delivery capabilities. Recent reports on potential advantages of this laser for lithotripsy of ureteral stones prompted us to develop an Er:YAG fiber delivery system for endoscopic lithotripsy of salivary stones. We report on the development of this system and its clinical use on 17 patients.

Study design/materials and methods: Ho:YAG and Er:YAG laser fragmentation performances were initially compared. Optimal laser parameters for lithotripsy of salivary stones were then established ex vivo using a commercial dental Er:YAG laser (Lumenis Opusdent 20). Metal hollow waveguides optimized for Er:YAG laser transmission were end sealed with a polished sapphire rod of 0.63 mm diameter and designed to adapt to the Opusdent laser and to a Storz sialoendoscope. The system was tested ex vivo for durability and clinical compatibility at input energies up to 700 mJ, 10-20 Hz. Following Helsinki approval the system was clinically tested on 17 patients with sialolithiasis.

Results: Lithotripsy threshold was around 80 mJ/pulse (26 J/cm2) while efficient fragmentation, with microscopic fragments, was observed at an output energy range of 150-300 mJ/pulse. At 10 Hz, fragmentation rates of about 1.8 mm3/second were achieved enabling lithotripsy of a 6 mm stone in about 2 minutes. Front surface damage to the sapphire rod occurred but did not contribute to significant loss in fragmentation efficiency. Of the 21 stones treated clinically, 5 were fully fragmented, 7 were prepared for extraction by mini forceps, and 9 were released from surrounding soft tissues for subsequent removal. Fifteen of the 18 treated glands returned to normal function without any symptoms.

Conclusions: The Er:YAG endoscopic delivery system described is a clinically viable and cost-effective device for a range of hard and soft tissue wet field applications accessible through rigid or semi-rigid endoscopes. Further improvements in the waveguide may allow access also through fully flexible endoscopes.