Holmium YAG Laser: Is it the end of the Era for Stone Management
The flash lamp-pumped, solid-state Holmium YAG Laser has been the Laser of choice for use in ureteroscopic lithotripsy for the past 20 years. However, although the holmium laser works well on all stone compositions and is cost-effective, this technology still has several fundamental limitations. The use of a ‘dusting’ mode with low pulse energy (0.2–0.4?J) and high pulse rate (50–80?Hz) settings, is gaining popularity in lithotripsy due to the desire to produce smaller residual stone fragments during ablation, capable of being spontaneously passed through the urinary tract. Recent developments in the Holmium YAG Laser lithotripsy include the introduction of pulse modulation. This technique delivers the laser energy in an asymmetric manner such that an initial bubble is created (the ‘Moses effect’) through which the remainder of the energy can then travel through without being absorbed by surrounding water.
Each of these laser technologies is associated with technical advantages and disadvantages, and the search continues for the next generation of laser lithotripsy systems that can provide rapid, safe, and efficient stone ablation. New fibre-optic approaches for safer and more efficient delivery of the laser energy inside the urinary tract include the use of smaller-core fibres and fibres that are tapered, spherical, detachable or hollow steel, or have muzzle brake distal fibre-optic tips. These specialty fibres might provide advantages, including improved flexibility for maximal ureteroscope deflection, reduced cross section for increased saline irrigation rates through the working channel of the ureteroscope, reduced stone retropulsion for improved stone ablation efficiency, and reduced fibre degradation and burn back for longer fibre life.
The frequency-doubled, double-pulse YAG (FREDDY) Laser has been tested as a more compact and efficient solid-state laser than the initial dye lasers for short-pulse lithotripsy, but the FREDDY laser is not effective for all stone compositions. The Erbium: YAG Laser has been tested for efficient ablation of urinary stones, but a suitable mid-infrared optical fibre delivery system is not available for this procedure.
The Thulium fibre laser (TFL) is the most promising alternative to holmium for lithotripsy owing to its use of a more suitable TFL wavelength, smaller fibres, and potential for using a smaller, less expensive laser system; however, clinical studies are needed to assess this new technology. TFL promotes the development of novel miniature fibre-optic delivery systems, including tapered, ball tip, hollow steel tip fibres, and muzzle brake fibre-optic tips, which can reduce both fibre burn back or degradation and stone retropulsion without sacrificing laser ablation rates.
Luke A Hardy, Nathaniel M Fried et al (2019) compared Thulium vs Holmium YAG at three settings and found Holmium laser ablation rates were lower than for TFL. For all three settings combined, 7% stones treated with Holmium Laser were completely fragmented in ?5 minutes compared to 60% stones treated with TFL.
Miniaturization holds the key. With the introduction of both new modifications of time-tested technologies as well as completely novel modalities, the practicing urologist's armamentarium of devices for the surgical management of kidney stones continues to grow. As the popularity of ‘mini’ procedures continues to grow, the adaptability of these technologies to these procedures will be critical to maintain maximum relevance.
I am providing two articles addressing the utility of TFL over Holmium. There are overlaps in the articles provided but collectively they address why Thulium could replace Holmium in near future.
Are we likely to see the end of our old friend Holmium YAG from the management of Stones in the near future?