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Page 2 of 9 Shirakawa et al. Mini-invasive Surg 2020;4:33 I http://dx.doi.org/10.20517/2574-1225.2020.30

(P < 0.001) after standardization. The moving average showed a marked decrease of thoracoscopic operative time
during the standardization phase.

Conclusion: Microanatomy-based standardization enabled quicker and more precise UMLD despite an increase in
the number of surgeries performed by less experienced operators.

Keywords: Minimally invasive esophagectomy, lymph node dissection, microanatomy, thoracoscopic operative
time, recurrent laryngeal nerve palsy

INTRODUCTION
Esophageal cancer (EC) is one of the most common gastrointestinal malignancies, mainly in Asian
[1]
countries, and has a poor prognosis . Even today, primary treatment is still radical esophagectomy with
[2]
regional lymphadenectomy . The surgical strategy for EC though has been shifting towards minimally
invasive esophagectomy (MIE). Currently, thoracoscopic esophagectomy is the most common type of
MIE. In 1992, the world’s first thoracoscopic esophagectomy was performed in the lateral decubitus
position . For a period of time after, thoracoscopic esophagectomy in the lateral decubitus position (TELP)
[3]
[4,5]
was the standard in MIE, and much progress was made, especially in Japan . Although thoracoscopic
[6,7]
esophagectomy in the prone position (TEPP) was reported slightly later than TELP , this procedure
[8]
had not been used for a while. However, in 2006, Palanivelu et al. reported about 130 cases of TEPP and
showed both decreased operative time and the frequency of respiratory complications compared with
TELP and open esophagectomy. It was also reported that the main reasons for TEPP’s usefulness were due
to the advantages of good exposure of the surgical field and improved ergonomics for the surgeon. Since
then, TEPP has increasingly been adopted all over the world, including here in Japan, and there have been
several reports of the tolerability and efficacy of this procedure [9-12] .

Upper mediastinal lymph node dissection (UMLND) remains the most important procedure in esophageal
cancer surgery. However, this has also been the most difficult and time-consuming part, especially in
TEPP. Although there have been technical reports about UMLND in TEPP, the longer thoracoscopic
operative times and the higher recurrent laryngeal nerve (RLN) palsy rates of 10%-28% represent persistent
challenges [9,13,14] . Recently, progress in the development of endoscopic optical instruments [2K full high-
definition (HD), 4K ultra-HD, and 3-dimensional] has been remarkable. Using them, we have been able
to identify the fine microanatomy of membranes and layers that were not previously visualized, and there
have been some reports on this new concept of surgical microanatomy and its usefulness in esophageal
cancer surgery [13-18] .

In our institution, we have performed more than 500 cases of TEPP. Since reaching around 350 cases, we
have been able to use a 4K ultra-HD system for our surgeries. Therefore, we started microanatomy-based
standardization of UMLND using this endoscopically magnified view and established it when we reached
around 400 cases. Previously, we have reported the concept of this standardization on the left side and its
usefulness for safe and efficient surgery, especially for decreasing recurrent laryngeal nerve palsy rates .
[19]
Concurrently, we have also standardized UMLND on the right side with the same concept as on the left
within the same period.

The aim of this study was to investigate the outcomes of our microanatomy-based standardized procedure
for UMLND on both sides using a 4K ultra-HD system, with a focus on decreasing operative time.