Medical Robotics
Toward a Flexible Variable Stiffness Endoport for Single-Site Partial
Nephrectomy
E. A
MANOV
,
1
T.-D. N
GUYEN
,
1
S. M
ARKMANN
,
1
F. I
MKAMP
,
2
and J. B
URGNER
-K
AHRS
1
1
Laboratory for Continuum Robotics, Leibniz Universita
¨
t Hannover, Appelstr. 11, 30167 Hanover, Germany; and
2
Clinic for
Urology and Urologic Oncology, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hanover, Germany
(Received 17 November 2017; accepted 25 May 2018)
Associate Editor Pierre Dupont oversaw the review of this article.
Abstract—Laparoscopic partial nephrectomy for localized
renal tumors is an upcoming standard minimally invasive
surgical procedure. However, a single-site laparoscopic
approach would be even more preferable in terms of
invasiveness. While the manual approach offers rigid curved
tools, robotic single-site systems provide high degrees of
freedom manipulators. However, they either provide only a
straight deployment port, lack of instrument integration, or
cannot be reconfigured. Therefore, the current main short-
comings of single-site surgery approaches include limited tool
dexterity, visualization, and intuitive use by the surgeons.
For partial nephrectomy in particular, the accessibility of the
tumors remains limited and requires invasive kidney mobi-
lization (separation of the kidney from the surrounding
tissue), resulting in patient stress and prolonged surgery. We
address these limitations by introducing a flexible, robotic,
variable stiffness port with several working channels, which
consists of a two-segment tendon-driven continuum robot
with integrated granular and layer jamming for stabilizing
the pose and shape. We investigate biocompatible granules
for granular jamming and demonstrate the stiffening capa-
bilities in terms of pose and shape accuracy with experimen-
tal evaluations. Additionally, we conduct in vitro experiments
on a phantom and prove that the visualization of tumors at
various sites is increased up to 38% in comparison to straight
endoscopes.
Keywords—Continuum robot, Granular jamming, Layer
jamming, Variable stiffness.
INTRODUCTION
Not only improvements in diagnosis of earlier
stages,
11
but also the rising incidence of kidney cancer
7
lead to an increasing number of small renal masses, in
which organ preserving partial nephrectomy is the gold
standard. The safety and efficacy of this surgical con-
cept has been evaluated extensively leading to surgical
guideline recommendations.
16,27
Minimally invasive
partial nephrectomy has proved its safety in terms of
oncological and functional outcomes,
13,22
but its broad
introduction to surgical routine was hampered by the
laparoscopic accessibility of the kidney, the high
complexity of reconstructive surgical steps, and the
consecutively flat learning curve of these procedures.
Therefore, these procedures are only performed at
higher frequencies at centers with proven laparoscopic
expertise.
10
Conventional or robot-assisted laparo-
scopic procedures performed with straight instruments
are the common standard. Mostly upper pole or dorsal
renal masses require an invasive, traumatizing mobi-
lization of the kidney with potentially prolonged hos-
pitalization to ensure visualization and accessibility of
tumors. In terms of invasiveness, laparo-endoscopic
single-site surgery (LESS) would be the preferable
surgical approach,
6
as it provides a reduced number of
port sites and a trocar positioning in a desirable allo-
cation as the umbilical grease, thereby improving
cosmetic outcomes. Thus, it would be desirable to have
a dexterous and flexible port system, such that a tumor
can be accessed from various orientations with various
instruments deployed through working channels.
Moreover, adjustable stiffness of the port can further
enhance the manipulability at the tumor.
Robotic single-site systems are proposed by several
researchers for various applications.
28,31
Most of them
suggest a similar structure consisting of a straight rigid
deployment port and several flexible or articulated
instruments inserted through the straight port. On the
one hand, serial robotic arms
19
or parallel robots
18
Addresscorrespondence to E. Amanov, Laboratory for Continuum
Robotics, Leibniz Universita
¨
t Hannover, Appelstr. 11, 30167 Hanover,
Germany. Electronic mail: amanov@lkr.uni-hannover.de
Annals of Biomedical Engineering (
Ó
2018)
https://doi.org/10.1007/s10439-018-2060-4
Ó
2018 Biomedical Engineering Society
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