In vitro evaluation of nitinol stone retrieval baskets for flexible ureteroscopy

Because of increased clinical relevance of retrograde intrarenal surgery (RIRS), a variety of stone retrieval baskets have been introduced into endourology. Differences in shape and material may have consequences in performance and efficacy of RIRS. The aim of the study was to evaluate the in vitro performance of multiple commercially available nitinol retrieval baskets.

Ten manufacturers of baskets for RIRS were invited to participate in this evaluation. The evaluation included measurement of the basket's internal resistance toward deflection, the influence on the deflection angle of a flexible ureteroscope (URF-P5, Olympus), and basket function in maximum deflection of the scope. All measurements were performed five times.

Nine manufacturers, providing a total of 15 baskets, decided to participate in this evaluation. Maximum deflection of the ureteroscope (275 degrees) was achieved in 12 baskets and reduced in 3. In maximum deflection, complete opening of the basket was possible in 13 samples. In one case, partial opening of the basket was possible; one basket failed. The measurement of the basket's internal resistance showed wide variations (5.97 to 38 mm deflection/g), consecutively leading to increased inner radius of the fully deflected scope in 10 of 15 tested samples.

The tested baskets showed wide variations in their resistance toward bending. Influence on overall deflection capacity seems minor, however. On the other hand, higher resistance leads to increased inner radius of the fully deflected renoscope, which may alter functionality. Knowledge about the basket's key feature and differences in basket performance may be crucial to choose the best tool for the patient.