Optimal deflection techniques for flexible and navigable suction ureteral access sheaths (FANS): a comparative in...

Area of Science:

• Urology
• Minimally Invasive Surgery
• Medical Device Engineering

Background:

• Flexible and navigable ureteral access sheaths (FANS) are essential tools in modern urology.
• Current evidence lacks clear guidelines on optimizing deflection capabilities of FANS.
• Understanding deflection mechanics is key to improving procedural efficiency and outcomes.

Purpose of the Study:

• To evaluate in vitro deflection angles achieved with two distinct FANS manipulation techniques: sheath advancement and ureteroscope deflection.
• To assess the impact of various sheath size-ureteroscope combinations on FANS deflection.
• To provide evidence-based insights for optimizing FANS usage in clinical practice.

Main Methods:

• In vitro evaluation of deflection angles for 10/12Fr, 11/13Fr, and 12/14Fr FANS.
• Testing with six different single-use flexible ureteroscopes (7.5Fr to 9.5Fr).
• Comparison of two deflection techniques: sheath advancement over a deflected ureteroscope and ureteroscope deflection relative to the sheath tip.

Main Results:

• Significant differences in maximum deflection angles were observed across ureteroscopes and techniques (ANOVA p < 0.01).
• The sheath advancement technique yielded the largest angles (218°-277°), exceeding manufacturer specifications in most cases.
• 10/12Fr and 11/13Fr sheaths demonstrated greater flexibility; the 11/13Fr sheath with OTU8.6Fr/Innovex8.7Fr ureteroscopes provided the largest angles.

Conclusions:

• Optimal FANS deflection is achievable via sheath advancement or ureteroscope deflection at the tip.
• Manufacturer-specified deflection angles appear difficult to attain even with optimized techniques.
• The sheath advancement technique and 11/13Fr sheath-ureteroscope combinations are recommended for challenging lower pole access, guiding urologists' FANS technique.