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Ishida et al. Mini-invasive Surg 2018;2:31 I http://dx.doi.org/10.20517/2574-1225.2018.53 Page 5 of 8

A A B

Figure 2. (A): Gross view of the instruments used in needlescopic surgery; (B): close up of the tips of the instruments shown in (A); 1:
conventional 5 mm forceps; 2: same-sized tip section as that of the 5 mm forceps with a 2.4 mm-diameter shaft

SILS was initially expected to result in less postoperative pain compared with CMLS. However, this
argument is controversial; indeed, the degree of postoperative pain after SILS is reportedly similar to or
greater than that following CMLS [39-41] . Although SILS involves fewer incision sites, the single incision could
be lengthened and stretched by insertion of a single port due to the challenges of handling conventional
[27]
laparoscopic instruments . This factor might explain the postoperative pain after SILS. The advantages
of RPS are a reduced level of technical difficulty and cosmetic outcomes similar to those of SILS, and an
operation time comparable to that of CMLS. In addition, the lengthening and stretching of the single
incision are reduced during RPS relative to SILS, which may decrease postoperative pain. The results of a
[33]
large prospective RCT comparing RPS with CMLS are awaited .
Future perspectives
RPS may be superior to SILS for CRC, as it has a lower level of technical difficulty while maintaining
less invasiveness. However, RPS is typically performed by a single surgeon and a laparoscopist, and has
a steep learning curve because the reduced number of ports interferes with forceps mobilization, leading
to less effective countertraction and visualization. Therefore, RPS may still be difficult to perform for less
experienced surgeons.

To overcome this difficulty, needlescopic surgery, which involves the use of forceps with a small-diameter
[42]
shaft instead of the conventional 5 mm port, has been developed [Figure 2]. Although the feasibility
of needlescopic surgery compared with CMLS for CRC has been evaluated [43,44] , needlescopic surgery is
expected to be less invasive and produce better cosmetic outcomes than CMLS. In addition, needlescopic
surgery for CRC does not increase surgeon stress, as it is basically identical to CMLS for all surgical
procedures. The disadvantages of the use of a small-diameter shaft in needlescopic surgery are the low
shaft stiffness and inability to exchange instruments . However, the stiffness and operability of these tools
[42]
have gradually been improved.

Although further prospective randomized studies of RPS (including needlescopic surgery) compared
with CMLS for CRC are required, needlescopic surgery for CRC may be a good starting point for young
surgeons and make feasible even less-invasive surgery.

CONCLUSION
Although further investigation is required, the surgical and oncological outcomes of SILS and RPS suggest
that they are safe and feasible procedures. RPS may be superior to SILS due to its lower level of technical