Structural factors influencing the clinical performance of 0.025-inch guidewires for pancreatobiliary endoscopy: An experimental study

Abstract

Background and study aims To develop a pancreatobiliary endoscopic guidewire with good clinical performance, an understanding of its structure is necessary. This study aimed to investigate the structural factors influencing the clinical performance of pancreatobiliary endoscopic guidewires. Methods Eight types of 0.025-inch guidewires were evaluated. The following structural properties were measured: tip length, tip deflection height, tip weight (TW), ratio of tip core weight to TW, shaft coating type (flat or uneven), outer diameter, and core wire diameter (CWD). Four performance tests were conducted to evaluate shaft stiffness as bending force (BF), shaft lubricity as friction force (FF), torque response as torque response rate (TRR), and seeking ability as total insertion success (TIS) in a technical test using a 3D bile duct model. The correlation coefficients of each variable were analyzed. Results The BF and CWDs were strongly correlated, as well as the FF and CWDs and BF. Among the guidewires with similar CWDs, the guidewires with uneven coating had significantly lower FF than those with flat coating. The TRR was strongly correlated with the CWDs; furthermore, guidewires with lower FF had better TRR. TIS was strongly correlated with the TRR, TWs, and ratio of the tip core weight to TW. Conclusions CWD affects shaft stiffness; CWD and coating type affect shaft lubricity and torque response. Because TRR and TW are correlated with seeking ability, an appropriate combination of core wire thickness, TW, and coating design is required to develop a guidewire with good seeking ability.

Keywords: Biliary tract; Endoscopic ultrasonography; Interventional EUS; Pancreatobiliary (ERCP/PTCD); Strictures.

Fig. 1

Basic construction of the guidewire and structural variables. The guidewire tip has a polyurethane coating, and the shaft is coated mainly with polytetrafluoroethylene. The core wire is inside the coatings. It is gradually tapered toward the tip, and a spiral-coiled spring is wound around the tip of the core wire. Tip length, deflection height, weight, and core weight, and outer diameter and core wire diameter are measured.

Fig. 2

Performance tests. a The three-point bending test using the universal testing machine. The shaft stiffness (bending force) of the guidewire is measured. b Measurement of shaft lubricity of guidewire in the catheter using the universal testing machine. The maximum friction force is measured as the guidewire is pulled inside the catheter. c The torque response of the guidewire is measured. Rotation is applied from the distal side of the guidewire in the circumferential direction, and the angle of rotation required to rotate the tip 30° is measured. d The 3D-printed silicone bile duct model. Twenty endoscopists participated in the seeking test to determine the insertion success of each guidewire. The target branches are B3 and B7.

Fig. 3

Tip deflection heights of the guidewires. Tip deflection height is measured based on the straight shaft section of the guidewire. a VisiGlide2. b M-Through. c Fielder 25. d EndoSelector. e J-WIRE Prologue ST. f RevoWave UltraHard. g RevoWave Hard. h SeekMaster.

Fig. 4

Shaft coating of the guidewires. a , b , e , f , g Flat coatings. c , d , h Uneven coatings. a VisiGlide2. b M-Through. c Fielder 25. d EndoSelector. e J-WIRE Prologue ST. f RevoWave UltraHard. g RevoWave Hard. h SeekMaster.

Fig. 5

Core wire diameter from the tip to 200 mm. The core wire diameters of the M-Through and Fielder 25 are identical. The core wire diameters of the RevoWave Hard and the SeekMaster are identical.

Fig. 6

erformance test results. Guidewires with core wire diameters ≥ 0.5 mm have significantly higher bending force than those with core wire diameters < 0.5 mm (P < 0.001). Of the guidewires with a core wire diameter ≥ 0.5 mm, the uneven guidewires exhibited a significantly lower friction force compared with the flat guidewires (P = 0.048). Of the guidewires with a core wire diameter < 0.5 mm, the uneven guidewires showed a significantly lower friction force than the flat guidewires (P < 0.001). In a comparison between guidewires of the same core wire diameters, the uneven guidewires ( c and h ) had higher torque response rates than the flat guidewires ( b and g ).

Fig. 7

Correlation matrix between structural and performance variables. The numbers in the matrix indicate the correlation coefficients (r) between each variable. The following pairs show strong positive correlations (r ≥ 0.7): bending force and core wire diameter (r = 0.983); friction force and core wire diameter (r = 0.788); friction force and bending force (r = 0.757); torque response rate and core wire diameter (r = 0.711); total insertion success and tip weight (r = 0.785); and total insertion success and torque response rate (r = 0.772). The total insertion success and ratio of tip core weight to tip weight show a strong negative correlation (r = –0.772).