An increase in the prevalence of urolithiasis to 5%, i.e. an increase of 25 percent within 20 years, was ascertained in Germany in 2000
The further development of instrumental technique towards extremely thin and even flexible ureteroscopes as well as modern lithotripsy procedures with various energy sources has once again placed special emphasis on endoscopic and percutaneous minimally invasive techniques
One endoscopic procedure is endourologic lithotripsy in which the stone is destroyed in the ureter. Sometimes the stone is simultaneously stabilized by a stone basket. These baskets are made of nitinol a shape memory alloy of nickel and titanium (melting point ~ 1300°C)
. This stabilization of the stone in the basket could be on purpose or by accident. By accident means that an impaction in the ureter occurs by an extraction of a stone with a basket. Stabilization on purpose means to avoid a retropulsion into the kidney during a lithotripsy with a stone in the stone basket. At this part of the operation stone baskets have been frequently destroyed
. This severing of wires can lead to ureteral trauma due to hook formation
. On the other hand it could release the impacted stone in the basket from the basket by destructing all wires of the basket
How quickly fragmentation with the laser occurs has been examined in vitro by Honeck et al.
. Baskets with a diameter of 3 Ch. were destroyed in 15–34 seconds and tipless Nitinol baskets (1.8 Ch. diameter) were destroyed in 1–4 seconds with a pulse energy of 0.8 and 2 J and a pulse frequency of 5 Hz. The guidance of the optical fibre occurred by means of a cystoscope in a container filled with water.
Cordes et al.
 investigated four lithotripter and four different types of stone baskets. In this study they showed that the resistance of the baskets depends on the thickness of the wires. Also plaited wires seem to be more resistant to the radiation of the laser. An overview of accidental fragmentation of dormia basket and guidewire showed that this problem should be further investigated
This study attempted to make stone baskets more resistant to a Holmium:YAG-laser by coating them with a titanium oxide layer established by a sol–gel process. This process was investigated by BioCer, and is normally used for polymer medical implants such as hernia meshes or hard-tissue implants. Because of the biocompatibility, the industrial availability and clinical experience with this layer we tested this layer on the basket-wires. The crystal class is tetragonal (rutil) which is the most common form of Titanium Dioxide. Rutil is hard, chemically resistant and has a high refractive index.