Cornering the Challenge: Initial Clinical Experience with EndoTheia FlexStone Endoscopic Steerable Basket

The FlexStone device (EndoTheia, Nashville, TN) is an investigational, steerable stone basket. The device provides additional flexion separate from the ureteroscope without an assistant. We evaluated the safety and feasibility of this new novel device for stone retrieval.

In this first-in-human clinical trial, 10 patients underwent flexible ureteroscopy (URS) for renal calculi using the FlexStone device. The primary endpoint was the safe and successful basketing of renal stones with the device. Intraoperative and short-term postoperative adverse events were evaluated. Secondary endpoints included surgeon workload assessed by the National Aeronautics and Space Administration Task Load Index (NASA-TLX).

The majority of patients had a solitary stone (60%) and stone was in the lower pole (90%) with a minority of patients also having stones in upper pole (20%) or interpolar region (10%). Median cumulative axial stone size was 11 mm (interquartile range [IQR]: 7.5-15.25 mm). The device was used to extract (60%) or reposition (40%) of stones. Surgeons used the FlexStone device to successfully basket target stones in 9 cases (90%). No intraoperative complications occurred. Postoperatively, one patient needed a second URS procedure for hydronephrosis, but no obstructing stone was seen. On the NASA-TLX scale from 1 (low) to 21 (high), the demand when using the device was low, with median mental demand-6 (IQR: 4-12), physical demand-9 (IQR: 6-12), temporal demand-6 (IQR: 4-6), and frustration-6 (IQR: 1-6). Surgeons rated the device with high overall performance (median 3, IQR: 3-8, perfect = 1).

Our preliminary investigation demonstrates the safety of a new, unique steerable stone basket. The FlexStone device is a potentially valuable addition to the urologist's armamentarium, especially for complex caliceal anatomy and improving ergonomics when using URS.