Three-dimensional spiral-shaping method of microcatheter for paraclinoid aneurysms: assessment using silicone models

Abstract

Selecting an appropriate microcatheter tip shape for paraclinoid aneurysms is difficult. Therefore, we devised an original simple and uniform three-dimensional (3D) spiral-shaping method of microcatheter and validated the characteristics and usefulness of this method for coil embolization of paraclinoid aneurysms using patient-specific silicone models. These silicone models were produced based on clinical data from four patients with four paraclinoid aneurysms that underwent endovascular treatment using the 3D spiral-shaping method. These models were classified into four types: superior, medial, inferior, and lateral corresponding to the aneurysm protrusion and locations (C3 or C2 segments by Fisher's classification). Employing a pulsatile pump setup, two operators assessed the following items: navigation methods (pull and wire guiding), catheterization times, microcatheter tip position in the aneurysm, and the feasibility of inserting a framing coil by simple technique compared with three other shapes (straight, 90, pigtail). Three-dimensional spiral-shaped microcatheter could be placed in the medial and inferior type models of C3 segments and superior type model of C2 segment by the pullback method. Catheterization times using a 3D spiral-shaped catheter were significantly shorter than other shaped ones in the superior type models. No significant difference was found in another silicone model. Three-dimensional spiral- and pigtail-shaped catheters tended to position the tip at the center of the aneurysm. In conclusion, 3D spiral-shaped microcatheter was especially effective for the superior projected aneurysm at the C2 segment. The 3D spiral-shaping method can provide easy and secure navigation of the microcatheter into the paraclinoid aneurysms, ensuring optimal positioning for coil insertion.

Keywords: coil; embolization; microcatheter; paraclinoid aneurysm; silicone model.

Fig. 1

Characteristics of the paraclinoid aneurysms adopted for the silicone models Fig. 1A: Characteristics of the paraclinoid aneurysms and rotational direction of the spiral-shaped microcatheter. Fig. 1B:The aneurysmal direction was defined by four directions (angle formed between the horizontal and virtual lines that crosses between the centers of the aneurysm sac and aneurysm neck); superior, medial, inferior, and lateral. ICA: internal carotid artery BAC: balloon-assisted coil embolization MCA: middle cerebral artery AC: anterior cerebral artery 3D: three-dimensional

Fig. 2

The three-dimensional (3D) spiral-shaping method, other shapes, and experimental setup Fig. 2A: Making a shaping mandrel into a 3D spiral shape with a diameter of 5 mm and a pitch of 5 mm. Fig. 2B:The 3D spiral-shaped mandrel was inserted into a straight microcatheter to be 1 + 1/4 around from the tip. Fig. 2C:After heat shaping, the ideal microcatheter shape is a 3D spiral with a diameter of 7 mm and a pitch of 7 mm. Fig. 2D: Photographs of three microcatheters used for comparison: straight, preshaped 90°, and two-dimensional (2D) pigtail-shaped presented in order. Fig. 2E:Experimental setup.

Fig. 3

Boxplot of the catheterization times needed to guide the microcatheter into the aneurysms Fig. 3A: Model 1 for medial type at C3 segment. Fig. 3B: Model 2 for inferior type at C2 segment. Fig. 3C: Model 3 for inferior type at C3 segment. Fig. 3D: Model 4 for superior type at C2 segment. STR: straight shape