Retrieval capabilities of different stone basket designs in vitro

Several designs of endoscopic stone retrieval baskets are available. Each instrument has special characteristics which can be employed in different locations with different techniques and various effects. In this study, we compared the retrieval capability of five basket designs in two in vitro models.

The five baskets were a flat wire (Segura), Parachute, N-0-tip, and two helical designs. The ability of the baskets to retrieve beads of 4, 6, and 8 mm was compared in two models. Each size was used individually, and four beads of the 4-mm size were also studied. In the first model, single and multiple beads were placed in a cylindrical plastic tube to mimic removal of the stone from the ureter. In single-bead retrieval trials, the basket was opened beyond the bead and withdrawn, whereas with multiple beads, the basket was opened beyond, withdrawn, and closed. Bead engagement and removal was considered a successful retrieval. Three repetitions were performed for each basket and each bead size. In the second model, similar beads were placed in a round-bottom test tube to simulate a stone within a calix. The basket was opened at the base of the tube and closed. The number of beads removed was noted for three repetitions for each basket.

All baskets were able to retrieve the 4-, 6-, and 8-mm beads from the cylinder, with the exception of the four-wire helical basket, which failed in two of the three retrieval attempts for the 4- and 6-mm beads, and the double-helical basket, which failed in two of the three retrieval attempts for the 4-mm bead. When four beads 4 mm in size were used, the Parachute and double-helical baskets retrieved all of them within two trials and the N-0-tip and four-wire helical baskets within three trials. The Segura basket failed all trials. In the test tube model, all baskets failed to remove any beads with the exception of the N-0-tip, which was successful in removing a single bead with each positioning.

In these in vitro models, it was apparent that the design of the basket affects its ability to retrieve calculi in different situations.