Surgery Today
https://doi.org/10.1007/s00595-020-02224-y

ORIGINAL ARTICLE

Experimental evaluation of the fineness of needle forceps: advantages
other than minimal access
Kenta Doden1 · Noriyuki Inaki2 · Toshikatsu Tsuji3
Received: 31 August 2020 / Accepted: 16 November 2020
© Springer Nature Singapore Pte Ltd. 2021

Abstract
Purpose Needle forceps are used to limit damage to the abdominal wall in endoscopic surgery; however, few experimental
studies have evaluated the fineness and performance of needle forceps. We conducted this study to identify the advantagesof needle forceps over conventional 5 mm forceps, focusing on fine grasping and needle control.
Methods Twenty physicians executed tasks using 5 mm forceps and 2.1 mm small diameter forceps in a laparoscopic experimental setting. First, we timed the execution and recorded the number of drops in a task of grasping and moving grains ofrice and red beans. Next, we measured the execution time, looseness of the knot, and the deviation from the stitching point
in a suture and ligation task using suture needles with a diameter of 17 or 26 mm.
Results The needle forceps required a significantly shorter execution time to move the rice grains (37.7 s vs. 45.8 s; p = 0.01)
and a significantly higher completion rate (90% vs 20%; p < 0.01). The deviation of the stitching point using the 17 mm needle
with needle forceps was significantly smaller than with the 5 mm forceps (0.5 mm vs. 1.0 mm; p < 0.01).
Conclusion Needle forceps are better for procedures requiring fine grasping and enable more accurate small diameter needle
control than 5 mm forceps.
Keywords Ergonomics · Laparoscopy · Needlescopic surgery · Reduced port surgery · Task performance

Introduction
Laparoscopic surgery is performed widely and has becomea standard treatment option for malignancies based on thefeasible oncologic outcomes of multicenter prospective
studies [1, 2]. Recently, robotic-assisted surgery has been
implemented in the surgical field even for more advanced
procedures, such as pancreatectomy [3] and esophagectomy[4]. In this passage from laparoscopic surgery to robotic surgery, surgeons have attempted to reduce the number andsize of ports used to limit destruction of the abdominal walland obtain excellent cosmetic outcome, which has led to the* Noriyuki Inaki
n.inaki@viola.ocn.ne.jp
1

Department of Surgery, Yokohama Sakae Kyosai Hospital,
132 Katsuramachi, Yokohama 247‑8581, Japan2

Department of Surgery, Juntendo University Urayasu
Hospital, 2‑1‑1 Tomioka, Urayasu, Chiba 279‑0021, Japan3

Department of Gastroenterological Surgery, Ishikawa
Prefectural Central Hospital, 2‑1 Kuratsuki‑higashi,
Kanazawa, Ishikawa 920‑8530, Japandevelopment of reduced port laparoscopic surgery (RPS)
and reduced port robotic surgery (RPRS). Since needle forceps emerged to limit damage to the abdominal wall andobtain excellent cosmetic outcomes in the late 1990s [5, 6],
they have played an important role in RPS as minimal accessdevices [7]. Some randomized controlled trials have shown
the clinical advantages of needle forceps [8, 9]. These studies reported that downsizing the trocar in laparoscopic cholecystectomy from 10 mm to needle instruments resulted inless postoperative pain. Although smaller instruments demonstrate better knot-tying and reduce the surgeon’s workload in a restricted workspace simulating an infant bodyin an experimental setting [10], few experimental studies
have evaluated the fineness and performance of needle forceps according to object size. Theoretically, smaller forceps
should make handling smaller objects easier; hence, we conducted a series of experiments to compare needle forceps
with conventional 5 mm forceps.

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Methods
Doctors were recruited as subjects from the Departmentsof Surgery, Urology, and Gynecology at Ishikawa Prefectural Central Hospital and Yokohama Sakae Kyosai Hospital. We could not identify the effect size needed to calculate the sample size based on the prior information about
the parameters of interest because of the limited publisheddata on this. Thus, the number of participants includedin the study determined the study size. Each subject was
asked about his or her postgraduate year and board certification status, including certification from the endoscopic
surgical skill qualification system by the Japan Society for
Endoscopic Surgery (JSES). The need for ethical approval
for this study was waived by the Ethics Committee of the
Ishikawa Prefectural Central Hospital and Yokohama
Sakae Kyosai Hospital.
Subjects were given the following two tasks (Fig. 1) ina laparoscopic experimental setting (Fig. 2).
Task 1: Grasping and moving red beans and grains ofrice (Fig. 3). Repeated twice.
Task 2: Suture and ligation using thread and needles with a 26 mm radius and a 17 mm radius (Fig. 4).
Repeated twice.
Subjects executed these tasks in two different conditions(Fig. 5): One, using conventional 5 mm forceps [ENDOPATH™ 5DCD Maryland dissector (double action jaw,
shaft length: 30 cm) and an ENDOPATH™ needle holder(shaft length: 30 cm), Ethicon Inc., New Jersey, Unitedstates]; and the other, using 2.1 mm small diameter forceps[BJ needle R™ forceps (single action jaw, shaft length:31.5 cm) and a BJ pico™ needle holder (shaft length:
30 cm), NITI-ON Co., Ltd., Chiba, Japan]. The order ofFig. 2  Laparoscopic experimental setting. Subjects stood in front of
the laparoscopic trainer box. The angle of the scope was adjusted by
the subjects to maximize comfort

forceps tested was counterbalanced among the subjects
to minimize order effects, such as fatigue and practice.
Subjects stood in front of the laparoscopic trainer box andadjusted the angle of the scope to maximize comfort. Subjects used their nondominant arm for stability, but not tohelp them perform the test. The subjects were given 3 minof practice time before each condition and allowed to rest
for short (30–60 s) periods between runs.

Fig. 1  Flow chart of experimental evaluation of the forceps. The order of forceps testing was counterbalanced among the subjects to minimizeorder effects

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Fig. 3  Experimental setting of Task 1. Grasping and moving redbeans and grains of riceFig. 5  Subjects executed Tasks 1 and 2 with 5 mm instruments andneedle instruments

without any drops, this was evaluated as a completion.
For Task 2, we recorded the execution time and deviationof the stitching point from the marked dots. The execution
time started when the subject picked up the suture needle
and ended when they finished tying the knot. The sum of
the gaps between the tied thread and marked dots were
calculated after finishing each run. If both edges of thesuturing pad were adhered, the tightness of the knot wasevaluated as secure.

Statistical analysis
Fig. 4  Experimental setting of Task 2. Suture and ligation using
26 mm and 17 mm suture needles

Task 1 required the subjects to pick up 10 red beans or 10
grains of rice from a small paper dish and place them intoanother dish one by one. Grains dropped outside the dishwere not allowed to be picked up again. In Task 2, subjects
had to suture between two dots marked on different edges
of a laparoscopic suturing practice pad (STPP06™, 3-DmedInc., Ohio, United States) and make one surgical square knot
using the 26 mm and 17 mm suture needles. The distance
between the dots was dependent on the size of the sutureneedles, with a 5 mm gap for the 26 mm suture needle anda 3 mm gap for the 17 mm suture needle.

Measurement and analysis items
For Task 1, we recorded the execution time and the number of drops. If the subject performed the task twice

The Shapiro–Wilk test was used to verify whether thequalitative variables followed a normal distribution. Variables with a normal distribution are described as the meanand standard deviation (SD), and those with a non-normal
distribution are described as the median and interquartile
range (IQR). Student t tests or Mann–Whitney U tests wereused to check independent means when the application
conditions (normality and homoscedasticity) were not fulfilled. The paired Student’s t test was used when the means
were paired, and the Wilcoxon test was used when theconditions of applicability were not fulfilled. McNemar’s
test was performed to analyze the proportions of the paired
data. p < 0.05 was considered statistically significant. All
statistical analyses were performed with EZR (Saitama
Medical Center, Jichi Medical University, Saitama, Japan)[11], which is a graphical user interface for R (The R
Foundation for Statistical Computing, Vienna, Austria).
More precisely, EZR is a modified version of the R commander designed to add statistical functions frequently
used in biostatics.

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Results
Twenty physicians were recruited as subjects and their number seemed to be acceptable for the experimental evaluation[12]. The study group included 15 surgeons, 4 gynecologists,
and 1 urologist. The subjects consisted of 7 endoscopic surgical skill qualified physicians, 7 board certified physicians,
and 6 residents in training. The mean duration since medical
licensing was 9 (4.75–14) years. The study group comprised
19 men and 1 woman. Two of the seven endoscopic surgical skill qualified physicians had prior experience of usingneedle forceps in surgery. No subgroup comparisons were
performed. All subjects executed both Task 1 and Task 2.

Task 1

Table 1  Task 1: grasping and moving red beans and rice grains
5 mm forceps

Needle forceps

p value

5/20 (20%)

12/20 (60%)

0.046

40.3 (34.7–47.0) 45.2 (36.6–64.9) 0.057
4/20 (20%)

18/20 (90%)

0.000545.8 (40.7–51.2) 37.7 (32.2–41.3) 0.011

Table 2  Task 2: suture andligation using needle and thread

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Task 2
Table 2 shows the results of Task 2. The mean deviation of
the stitching point with the needle forceps with a 17 mm needle was 0.5 (0–1) mm, which was significantly smaller thanwith the 5 mm forceps [1 (0.5–2) mm] (p = 0.009). There
was no difference in the execution time required for sutureand ligation or the tightness of the knot. No significant differences were observed in the task when using the 26 mm
needle for all evaluation items.

Discussion

Table 1 shows the results of Task 1. The mean execution
time to move the rice grains with the needle forceps was
37.7 s (32.2–41.3 s), which was significantly shorter thanthat with the 5 mm forceps [45.8 s (40.7–51.2 s)] (p = 0.011).
The completion rate was also significantly higher with theneedle forceps than with the 5 mm forceps, with 18 people (90.0%) vs. 4 people (20.0%), respectively, finished thetask (p = 0.0005). The mean execution time for moving the
red beans with the needle forceps was 45.2 s (36.6–64.9 s).
Although it took longer with the 5 mm forceps [40.3 s(34.7–47.0 s)], the difference was not significant (p = 0.057).

Beans
Completion rate, n(%)
Execution time, s
Rice grains
Completion rate, n(%)
Execution time, s

The completion rate of moving the red beans was higher with
the needle forceps than with the 5 mm forceps (p = 0.046).

26 mm suture needle
Deviation of stitching point, mm
Tightness of knot, n (%)
Execution time, s
17 mm suture needle
Deviation of stitching point, mm
Tightness of knot, n (%)
Execution time, s

Needle forceps with a diameter of 2.1 mm showed moreaccurate maneuverability for subtle tasks than 5 mm diameter forceps, without extending the operation time. To ourknowledge, this is the first report of an experimental comparison of 2.1 mm diameter forceps and 5 mm forceps,
although a previous study found that 3 mm instruments outperformed 5 mm instruments for a suture knot task with 5–0
polyglactin suture and other subtle tasks [13].
When designing this study, we assumed that 2.1 mm
needle forceps would be better for smaller tasks whereas
5 mm forceps would be better for larger tasks. Thus, weprepared two different-sized objects per task to evaluate this.
For the grasping task (Task 1), we chose beans as a suitableobject for the 5 mm forceps, in accordance with the previous report [13], and rice grains as suitable object for the
2.1 mm forceps considering the size difference between thetwo forceps. For the suturing and knot-tying task (Task 2), a
26 mm suture needle was selected as the optimal size for the
5 mm forceps, because a 26 mm suture needle is commonlyused for laparoscopic procedures like reconstruction after
gastrectomy and peritoneal closure during hernia repair. A
suitable suture needle for 2.1 mm forceps is considered to
be a 17 mm suture needle, as used commonly in pediatric

5 mm forceps

Needle forceps

p value

0.75 (0.5–1)
9/20 (45%)
48.7 (39.7–58.5)

0.75 (0.38–1)
11/20 (55%)
50 (37.5–64.9)

0.63
0.72
0.84

1 (0.5–2)
15/20 (75%)
51.8 (43.2–73)

0.5 (0–1)
13/20 (65%)
55.8 (41.4–66)

0.009
0.72
0.43

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surgery, bile duct reconstruction suturing, and other subtle
procedures.
The needle forceps were better for subtle tasks, suchas moving grains of rice and maneuvering small needles,
but there was no or little difference when handling larger
objects, such as moving beans and maneuvering large needles, which could be attributed to better visualization. In
a limited working space, even a 5 mm shaft can obscurevisualization and slow down the speed of detecting andgrasping small objects (Fig. 6). For transanal endoscopic
microsurgery (TEM), which requires surgeons to operate ina restricted working space, mini-instruments provided better
visualization than 5 mm instruments [14]. Lee et al. reported
that intracorporeal knot tying was faster in the neonatal simulator box using pediatric needle holders while maintaining
knot quality [10]. They concluded small tips of the pediatricinstruments occupy less space and allow better viewing. Better visualization within in a small space may have contributed to the superior results of the needle forceps with subtle
objects. However, the needle forceps did not shorten the time
for knot tying, unlike in the previous report [13]. This canbe explained by the fact that accuracy was also evaluated inour study and subjects may have put emphasis not only ontime but also on accurate maneuverability.
Restriction of the working angle and space are common
problems in single-incision laparoscopic surgery (SILS)[15, 16]. Because needle forceps minimize surgical trauma
and obtain excellent cosmetic outcomes, they are used not
only for needlescopic surgery but also for SILS [17, 18] to
improve the limited working angle. Although needle forceps
are frequently used for RPS, including SILS and needlescopic surgery, they are not generally used in conventional
laparoscopic surgery because of the drawbacks of the instruments, such as weak grasping power, small jaw size, andshaft rigidity. However, the new-generation needle forceps,
including the BJ needle instruments™, have more reliable

holding power and less bending of the shaft [19–21]. In the
nonclinical setting of this study, the newly developed needle
forceps maximized the performance of subtle tasks while
being consistent with handling larger objects. In the clinical setting of uniportal video-assisted thoracoscopic surgery(VATS), the shaft of large forceps bends easily because of
the ribs; however, the introduction of BJ needle™ forceps
to assist facilitated the uniportal VATS to be performed efficiently and safely [22]. Now, we use these new generationneedle instruments to perform laparoscopic surgery safely
without compromising the advantage of less postoperative
pain and early recovery. Procedures for which needle devices
are appropriate include hernia repair [19, 23, 24], suturingof bile duct [25] and lymphadenectomy around nerve tissue
that should be preserved [26, 27].
Needle instruments also help us to perform robotic surgery. Cundy et al. reported that in spatially constrained
workspaces, 3-mm nonrobotic instruments are better suited
for advanced bimanual operative tasks, such as suturing than
5- and 8-mm robotic instruments [28]. The da Vinci SP™
surgical system, a single-incision robotic surgery system,
was invented to reduce destruction of the abdominal walland enable intracorporeal triangulation through a single
port at the umbilicus with three double-jointed instruments.
Despite the excellent function of the arms, the working angle
and space are still limited, and an additional assistant port
could be inserted in difficult cases [29].
This study had some limitations. First, there was selection bias in the choice of devices. Although there are several small diameter forceps and 5 mm instruments, wechose the BJ needle instruments™ and Maryland forceps
for the study. Every instrument has different jaw quality inits surface, size, and action. Unless we develop different
size forceps with similar jaw quality for the experiment,
we have to compare established products with different jaw
quality. The 5 mm Maryland forceps we used in the study

Fig. 6  A 5 mm instrument(left) obscures visualizationand slows down the detection
and grasping of rice grains ona small dish compared with the
2.1 mm instrument (right)

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had a double action jaw, whereas the 2.1 mm forceps weused in the experiments had a single action jaw. Since
5 mm Maryland forceps are frequently used for fine grasping in the clinical setting, we used it for the experiment.
In theory, needlescopic instruments should have a double-action jaw in this comparison study, but there are no
2.1 mm instruments with a double-action jaw on the market. When we conduct our next experimental evaluation ofthese forceps, it would be favorable to use 5 mm forceps
with a single-action mechanism to compare with 2.1 mm
forceps, which all have a single-action jaw. The second
limitation was related to the learning curve of using needle
forceps. Except for two of the seven qualified physicians,
the subjects had little experience using needle forceps insurgery. Because the task of moving grains and suturingtask with 17 mm suture needles in a laparoscopic setting
is unfamiliar work for physicians, we counterbalanced theorder of the forceps used to minimize order effects. However, the several minutes allocated for practice were notenough to overcome the learning curve effect of needle
forceps use. This might have led to an underestimation of
the results of the needle forceps in this study. Surgeons ofvarious skill level were included among the subjects andsubgroup analysis was not designed in advance because
the sample size of the study was too small, which was
also a limitation of this study. All subjects performed thesame task with 2.1 mm forceps and 5 mm forceps, but subject bias could not be avoided. If the participants were all
experts or all novices such as medical students or interns,
the forceps would have been evaluated more appropriately.
In conclusion, our study demonstrated that needle forceps are able to be used effectively for fine grasping operations and enabled more accurate small needle control than
5 mm forceps. This suggests that adding needle forceps
to RPS is rational to maintain both surgical quality andminimal invasiveness.
Acknowledgements We thank NITI-ON for providing the needle forceps and Ethicon endo surgery for providing the 5 mm forceps andlaparoscopic box trainer used in this study.
Funding No Grant support has been obtained for this research.
Data availability Raw data were generated at Ishikawa Prefectural
Central Hospital and Yokohama Sakae Kyosai Hospital. Derived data
supporting the findings of this study are available from the corresponding author (NI) on request.

Compliance with ethical standards
Conflict of interest The authors declare that they have no competinginterests.
Informed consent Informed consent was obtained from all individual
participants included in the study.

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