14th International Symposium on Advanced Science and Technology in Experimental Mechanics

Visualization of the Load on the Human Body and Mechanical Analysis
of Injury Mechanism Caused by the Posture during da Vinci Surgery
UNIVERSITYOFYAMANASHI

Kazuya CHIGIRA, Yasumi ITO, Toshie SUGITA, Kaori SAKURAMOTO, Ryuichi YAMADA,Tatsuya FUKUOKA, Sota KONDO, Yoshiyuki KAGIYAMA, Tetsuya NEMOTO and Hiroshi MITSUI
University of Yamanashi, University of Yamanashi Hospital, National Center for Geriatrics and Gerontology
E-mail：g19tm016@yamanashi.ac.jp, yasumii@yamanashi.ac.jp

introduction

Nov. 1-4, 2019, Tsukuba, Japan

Results & Discussion
The result of the subject 4 is shown as a representative example. The line in the figure shows the time when theangle of the operating table reaches 30 °.

• In da Vinci surgery using a surgical support robot, which isa minimally invasive surgical procedure, it is required tomaintain a special posture(Trendelenburg position).

Skin strain• Surgical patients are forced to stay in the same body posture
for a long time. There is a risk of developing local pressure
ulcer and peripheral neuropathy1,2)．
Trendelenburg positionCountermeasures against injury risk during surgery• The choice of the posture fixation method is judged at each clinical site, and the load on thehuman body is not quantified at present.
• Previous studies have compared postural fixation methods based on the amount of
movement measured before and after surgery3). However, this method does not fully
elucidate the burden on the human body in Trendelenburg position is sufficiently clarified.

The purpose of this study
We aim to mechanical analysis of injury mechanism caused by the posture during da Vinci
Surgery. We measure body pressure distribution, skin strain and motion analysis, andinvestigate the load on the human body in Trendelenburg position.

(a) maximum principal strain(b) minimum principal strain
Principal strain amount and direction(position ①, subject 4, no protector)• It became clear that the maximum principal strain and the minimum principal strain tended toincrease in proportion to the angle until the angle of the operating table reaches 30 °.
• The maximum principal strain and the minimum principal strain are orthogonal with opposite
signs.
Since shear strain is a cause of skin damage, we quantitatively show the load on the skin due to the postureduring surgery.

Motion analysis

Materials & Methods• It became clear that the amount of movement
tended to increase in proportion to the angle
until the angle of the operating table reaches
30 °.
• It is understood that there is a difference inmovement amount at each measurement
point.

Subｊect
The experiment was conducted with eight healthy men in their 20s and 30s as subjects.
Detail of subject

Subject
12345678Age2423222324
3427
25

Height [m]1.671.73
1.70
1.75
1.80
1.67
1.68
1.60

Weight [kg]
65
62
70
70
59
65
61
65

Amount of movement(without head and neck protection)

Tensile strain occurs due to the difference in amount ofmovement. This indicates that the nerve and joint
hyperextension that can cause peripheral neuropathy
can occur.

Mechanism of Skin strain

Experimental conditions• Experiments were performed to simulate the surgicalenvironment• Subjects placed in trendelenburg position on theoperating table• At this time, we measure the back skin strain andperform motion analysis<Simulating the surgical environment>
We placed the subjects in the 30° trendelenburg
position for 2 minutes. Also, the experiment simulated
Image of the subjects conducting the experiment
the actual prostate surgery used da Vinci in theoperating room of this university hospital. Furthermore,
we measured each with and without the head and neckprotection device used by this Yamanashi University
Hospital.
<Trendelenburg position>
Subjects placed in lithotomy position (the position involves thepositioning of an individual's feet above or at the same level asthe hips) on the operating table. After that, we tilted theoperating table at a constant speed and placed the subjects in thetrendelenburg position. The subjects was kept in trendelenburg
position for a certain period of time and then placed inlithotomy position again.

• It is understood that the skin strain of thesacral region is reduced by using the head andneck protector.
• Using head and neck protection device
reduces the amount of shoulder movement
and reduces sacral skin strain.
Average principal strain and individual difference(maximum principal strain)
the human body slips down when the operating table is tilted. At this time, since the body pressure is concentrated
on the buttocks and scapula, it is considered that the skin of the sacrum and scapula is pulled. When the shoulder issupported, the difference in the amount of movement between the waist and shoulder is reduced. As a result, thesacral skin strain is thought to have decreased.

Conclusions
The head and neck protector• It became clear that skin strain and amount of movement tended to increase in proportion to the angle until
the angle of the operating table reaches 30 °.
• It is inferred that shear strain occurs because the maximum principal strain and the minimum principal
strain are orthogonal with the opposite sign. This shear strain is considered to be a cause of skin damage.
• The amount of movement of the human body is different for each parts, which causes tensile strain. As aresult, there is a possibility that nerve extension and joint hyperextension may occur which are causes ofperipheral neuropathy.

<Skin strain measurement>
The skin strain was measured using a strain
gauge at three points: ①left shoulder blade,②right shoulder blade, and ③sacrum,
where body pressure is likely to beconcentrated when the bone is in a supine
position.

① ②

Acknowledgments③The authors would like to thank Mr. Tanaka of Tokyo Measuring Instruments Laboratory Co, Ltd. for advice on
this research.
Sticking position ofstrain gauge<Motion analysis>
The target markers, which are the tracking
points in motion analysis, were stuck to a
total of five points: head, shoulders, fifthrib, waist, knees.

Mimetic diagram of strain measurement
method of skin

Sticking position of target marker

References
1) Yoshimura, S., Mizumoto, K.: A case of lower leg compartment syndrome caused by prolonged lithotomy
position (in Japanese), journal of The Japan Society for Clinical Anesthesia, 33-1, (2013), 81-91.
2) Defloor, T.: The risk of pressure sores: a conceptual scheme, J Clin Nurs, ;8: (1999), pp.206–216.
3) Sara, F., Leigh, R., Charles, A.: Comparison of the Memory Foam Pad Versus the Bean Bag with Shoulder
Braces in Preventing Patient Displacement during Gynecologic Laparoscopic Surgery, Journal of Minimally
Invasive Gynecology , 25-1, (2018),153-157.