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Page 2 of 8 Kuwai et al. Mini-invasive Surg 2022;6:16 https://dx.doi.org/10.20517/2574-1225.2021.122

INTRODUCTION
The advantages of endoscopic submucosal dissection (ESD) include the ability to control resection size and
[1,2]
shape and permit en bloc resection of large lesions . However, the adoption of colorectal ESD is not
widespread because of technical challenges imposed by the complex anatomic features of the large
[3]
intestine . To overcome these issues, several ESD devices, including the Dual knife, Flex-knife, insulated
tipped knife (IT-Knife), Hook-knife (Olympus, Tokyo, Japan), and Flush-knife (Fujifilm, Tokyo, Japan),
have been developed over the past two decades for colorectal ESD . Most conventional ESD devices have
[4]
freehand tips and are used without fixing the target, creating a potential risk of unexpected incision and
perforation of the colorectal wall.

In comparison, a scissor-type knife, such as the Stag Beetle Knife Jr (SB Knife Jr, Sumitomo Bakelite, Tokyo,
Japan), enables grasping of the target tissue, allowing controlled endoscopic dissection that potentially
prevents unexpected muscular layer injury . However, the scissor-type knife has features different from
[5]
those of other conventional ESD knives. Therefore, in this review, we describe the characteristics of the
scissor-type knife, specifically the SB Knife Jr, and discuss how to effectively use it for colorectal ESD.

CHARACTERISTICS OF THE SB KNIFE JR
The SB Knife series
The SB Knife series are scissor-type knives designed to grasp and cut the tissue being held using a
monopolar frequency applied through insulated blades (to prevent coagulation of the muscle layer) such
that only the tissue grasped within the electrodes is cauterized . There are four types of SB Knife: SB Knife
[6]
Short, SB Knife GX, SB Knife Jr, and SB Knife Jr 2. Figure 1 shows detailed characteristics of these knives.
The SB Knife Short and SB GX have curved blades to prevent coagulation of the muscle layer, whereas the
SB Knife GX has a partially serrated edge to prevent tissue slipping. The SB Knife GX is generally used for
gastric ESD, the SB Knife Short is used for submucosal dissection in esophageal ESD, and the SB Knife Jr
and Jr 2 are developed and used for colorectal and esophageal ESD [5,7-9] .

The SB Knife Jr
The SB Knife Jr was launched in 2010 [10,11] . Regarding the structure of the SB Knife Jr, the small tapered and
curved tip design with superior rotation allows accurate manipulation within the endoscope visual field to
minimize unintentional muscular layer injury. This knife has an opening width of 4.5 mm and a length of
3.5 mm.

The SB Knife Jr 2
[12]
The newly developed SB Knife Jr (SB Knife Jr 2) was launched in 2019 and is available only in Japan .
Figure 2 shows the three major points of improvement of the SB Knife Jr 2. First, the new coating materials
improve the coating durability, insulation coating, and incision ability. There is also improved tissue
grasping ability because of the new blade design with protrusions. Moreover, a new rotation handle
prevents the connection cord from tangling and enables easy manipulation. These improvements are
expected to shorten procedure times.

Equipment for colorectal ESD using the SB Knife Jr (i.e., high-frequency generator, injection liquid,
and tip hood)
The dissected segment is grasped, and a current is passed using a high-frequency generator [VIO300D,
VIO3 (ERBE, Tubingen, Germany) or ESG 100 (Olympus)]. The settings for high-frequency generators in
colorectal ESD using the SB Knife Jr or Jr 2 at our center are shown in Table 1.