Are We Banging Our Heads Against the Wall? The Effect of Treatment Head Wear on the Outcomes of Extracorporeal Shockwave Lithotripsy

Abstract

The manufacturer for the Storz Modulith SLX-F2 lithotripter recommends treatment head exchange after 1.65 million shocks. However, there is no documentation describing longevity of the treatment head with continued usage. The objective of this study is to determine whether there is a difference in stone fragmentation effectiveness with the treatment head at the beginning versus the end of its treatment life. We conducted a retrospective chart review of 200 patients-50 consecutive patients treated immediately preceding, and following, two separate treatment head exchanges. Primary outcome measures were stone-free rate (no stone), total stone fragmentation (any decrease in size), and fragmentation rate ≤4 mm (decrease in size with largest residual fragment ≤4 mm), based on most recent follow-up imaging post shockwave. There were no baseline characteristic differences between the pre-exchange and postexchange groups with respect to first time lithotripsy for the stone (85% vs. 77%), stone location, preoperative stenting (3% vs. 4%), mean stone density (912 hounsfield units [HU] vs. 840 HU), mean stone size (9.0 mm vs. 8.1 mm), stone location, and mean number of shocks delivered (3105 vs. 3089). Mean time to follow-up was 2.7 weeks in both groups, with most follow-up imaging consisting of a kidney ureter bladder X-ray (87% pre-exchange vs. 85% postexchange). Stone free (34% vs. 27%), total stone fragmentation (76% vs. 76%), fragmentation ≤4 mm (48% vs. 42%), re-treatment rates (38% vs. 51%), and complication rates (6% vs. 7%), were not statistically different between the pre and postexchange groups, respectively. Exchanging the Storz Modulith F2 lithotripter head at the manufacturer recommended 1.65 million shocks does not affect the stone-free or fragmentation rate. If the manufacturer's recommendation for treatment head longevity is based on clinical outcomes, then there is likely room to extend this number without affecting treatment efficacy.