Comparison of Frictional Forces Among Ureteral Access Sheaths and Urinary Tract Dilators in a Novel Ex Vivo Porcine Ureteral Model

Abstract

Introduction:

Surface lubricity is a desirable characteristic of ureteral access sheaths (UAS), allowing for atraumatic navigation of the urinary tract. This study aimed to characterize the surface lubricity of commonly available 14F UAS, as well as 14F ureteral and urethral dilators, using a tribometer and a novel ex vivo ureteral tissue holder.

Materials and Methods:

The surface lubricity of 12, 14F urological catheters (8 UAS, 1 urethral dilator, and 3 ureteral dilators) was tested in six ex vivo Yorkshire porcine ureteral segments. A tribometer, capable of measuring force in thousandths of a Newton (N), measured frictional force during insertion and retraction cycles under a 4.0 N normal force. The coefficient of friction (COF) was calculated. Individual and cumulative lubricity scores (ILS and CLS) were calculated based on COF percentiles, enabling a comparative evaluation of device performance. Surface roughness was assessed via white light interferometry.

Results:

The Cook Flexor® UAS consistently demonstrated the highest lubricity, as reflected in its CLS for both insertion and retraction phases, followed closely by the Wellead ClearPetra® UAS. Dilators, including the Cook AQ hydrophilic-coated ureteral and urethral dilators, exhibited higher COF values, correlating with greater surface roughness. COF values were significantly higher during retraction cycles than insertion cycles (p < 0.05). Variability in COF across devices underscored the influence of surface properties on lubricity.

Conclusions:

Among all the UAS/dilators tested, the Cook Flexor® AQ-coated UAS and Wellead ClearPetra UAS had the best lubricity. Catheter retraction resulted in higher COF than catheter advancement.