New Techiques and TechnologiesFragmentation targeted at preferred discontinuities: A new concept in endolithotripsy with Holmium laser:YAGFragmentación dirigida a discontinuidades preferentes: un nuevo concepto en endolitotricia con láser Holmium:YAG☆
Introduction
Holmium laser endolithotripsy:Yttrium Aluminum Garnet (Ho:YAG) is based on the release of a shock wave and a cavitation effect from the collapse of a bubble of plasma generated at the tip of the fiber on the contact surface of the stone.1, 2 It is especially indicated in ureteroscopy (URS) and in retrograde intrarenal surgery (RIRS) with flexible ureteroscope.3 The high performance and wide margin of safety of the laser have extended its use to percutaneous nephrolithotomy (PNL), where it competes with other energy sources, such as ultrasonic and pneumatic ones.4, 5
At present, there are 3 technical modalities of laser lithotripsy, with their corresponding energy regimes (settings).6, 7 The fragmentation technique uses high ranges of work or pulse energy (1–4 J), with variable frequency rates (8–50 Hz) and short-release pulse, limited to a maximum power of 120 W (using a generator of this power and fibers of 550–1000 μs). The dusting technique uses minimum ranges of working energy (0.2–0.8 J), with high frequency rates (20–50 Hz) and long pulse width, with maximum power of 40 W. These modalities are applied to the most accessible areas of the stone in the center (dancing) or in the periphery (chipping).8 The “pop corn” technique consists in the random whirling fragmentation of loose fragments with high ranges of working energy (1–2 J) and frequency (15–30 Hz) and pulse of short or medium release, with maximum power of 60 W. The final power (in W) in each mode is conditioned by the performance of the laser generator and the size of the fiber.
We present the technique of fragmentation targeted at preferred discontinuities (FTPD), a new concept of endolithotripsy with Ho:YAG laser based on the selective application of energy on a zone visually prone to fracture of the stone due to preferential discontinuity, in a similar way to the formation of fragmentation lines that occur in large rock masses exposed to tectonic forces.
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Material and methods
The FTPD technique has been applied from January 2015 to February 2017 in 37 endolithotripsy procedures (7 PNLs, 16 RIRS, 12 URS, 2 cystolithotomies) with Ho:YAG laser (Lumenis Pulse 120H®, Tel-Aviv, Israel). The maximum power used was 24 W (3 J/8 Hz) with fibers of 365 and 273 μs (URS, RIRS), and 32 W (4 J and 8 Hz) with fibers of 550 μs (PNL, cystolithotomy). 1–5 short bursts were applied until observing the generation of a preferred discontinuity by anisotropy. The FTPD has been used on stones of
Results
With the FTPD technique, a strategic improvement has been obtained in all cases to continue the endolithotripsy with conventional techniques. No complications have been observed (wall lesion, stone migration, failure at the tip of the endoscope or fiber) directly attributable to the FTPD, which can be considered a complementary option of laser lithotripsy in combination with the basic fragmentation or dusting modalities. It has been more difficult to generate anisotropy in stones of whewellite,
Discussion
The geometric anisotropy of a mineral is based mainly on the existence of planes of crystallographic exfoliation (cleavage) and the crystalline habit. The geometric anisotropy of a solid body is the sum of all its anisotropies (crystalline, habit and any other derivative of external factors, such as gravity, deformation) for certain conditions of pressure and temperature. The overall anisotropy of a mineral conditions the formation of preferred discontinuities (fracture lines) with an
Conflict of interest
The authors declare that they have no conflict of interest.
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Please cite this article as: Sánchez-Martín FM, Emiliani E, Pueyo-Morer E, Angerri-Feu O, Sanguedolce F, Millán F, et al. Fragmentación dirigida a discontinuidades preferentes: un nuevo concepto en endolitotricia con láser Holmium:YAG. Actas Urol Esp. 2018;42:606–609.