Category: Clinical Stones: Equipment (stents, lasers, guidewires, sheaths)

MP27-2 - Thumb lever forces for tip deflection of flexible ureteroscopes

Sun, Sep 23
10:00 AM - 12:00 PM

Introduction & Objective : Performance of ureteroscopy requires repetitive bi-directional deflection of a lever operated by the user’s thumb.  Increasing evidence demonstrates that repetitive hand motions can lead to musculoskeletal problems and hand pain.  We have now evaluated forces required to deflect several different flexible ureteroscopes throughout the full range with several different instruments. 


Methods : Four variants of single-use ureteroscopes and one reusable ureteroscope were evaluated in the study (Uscope UE3011, NeoFlex-Ureteroscope, Lithovue, Prototype-C, Flex-Xc).  All scopes were prototypes, demonstrators or clinically used models.  A pull-force meter (Nextech DFS 500) was attached to the thumb lever and was used to deflect the tip from 30–210° in 30° intervals. Measurements were made both with up and down deflection, with an empty channel and with 365/273 micron fibers, 2.4 F nitinol basket (Dimension), Piranha 3F biopsy forceps, and 0.038 inch guidewire using both the flexible and stiff tips.  A two person team completed each study manually. 


Results :

The force required increased with increasing deflection of the tip for both directions. The difference in forces required to deflect the scope for each direction was nonsignificant.  The force necessary for deflection ranged from 2.0-7.0 N (0.45-1.57 Foot-pounds) at 30°  to 8.5-25.3 N (1.8-5.69) at 180°.  Full deflection could be achieved with each device except when using the stiff end of the guide wire, which prevented scopes from deflecting past 150°. 


Conclusions :

Forces required for steep deflection of the tip of a flexible ureteroscope reach levels near the limit of the normal thumb. The force is higher with increased deflection and with instruments within the channel.

Scott G. Hubosky

Professor
Department of Urology, Thomas Jefferson University Hospital
Philadelphia, Pennsylvania

Brian P. Calio

Clinical Research Fellow
Department of Urology, Thomas Jefferson University Hospital
Philadelphia, Pennsylvania

Demetrius H. Bagley

Professor
Department of Urology, Thomas Jefferson University Hospital
Philadelphia, Pennsylvania