With the popularity of thin-slice CT scans and the extensive application of artificial intelligence and three-dimensional reconstruction techniques, an increasing number of small lung nodules have been detected [16, 17]. The main treatment for small lung nodules is surgery, which includes lobectomy, segmentectomy and wedge resection [18, 19]. Recently, segmentectomy has been regarded as a common type of surgery [20, 21]. In this study, we demonstrated the use of a true lung segmentectomy technique, lobar split cone-shaped subsegmentectomy. This expands the scope of lung segmentectomy for patients with lung nodules in complex positions involving multiple segments. Avoiding the removal of additional lung tissue to protect lung function (only a small part of the lung lobe is removed) is conducive to postoperative rehabilitation. Moreover, we should note that the implementation of this type of segmentectomy had a threshold for the location, size and CTR of the nodules.
The use of a Lobar split cone-shaped subsegmentectomy cannot be easily understood but can be explained by this approach. To explain this phenomenon, we must mention the thoracoscopic tunnel technique. It was originally developed by Katsuyuki Endo in the 1990s and is called the “tunneling stapler technique” [22]. We call this splitting because it highlights its anatomy. Thoracic surgeons should be able to understand that there are obvious spacings with bronchi, arteries and veins between the different lung lobes, even if there is an incomplete interlobar fissure. When a lobectomy is performed on a patient with an incomplete interlobar fissure, ordinary splitting occurs if an anatomically incomplete interlobar fissure is selected. Furthermore, there are obvious spacings between the superior segment and the basal segment and between the lingular segment and the intrinsic segment, even if there is no fissure. Furthermore, between RS3 and RS1 + RS2, LS3 and LS1 + 2, and S9 + S10 and S7 + S8/S7 + 8, the spacings can be divided by splitting, as long as the anatomy does not vary significantly.
For the latter, accurate 3D reconstruction results and a skilled anatomical basis for the surgeon are needed. In the splitting approach, it is crucial to accurately identify hatchway 1 and hatchway 2. Once the two hatchways are identified correctly, the tunneling technique allows the surgeon to perform a deep dissection of the arteries to precisely identify the subsegmental branches and thus avoid misidentification. Considering that all lung segments and subsegments are irregularly cone-shaped, we introduced the concept of "cone-shaped segmentectomy", and the same applies to this splitting [23]. Then, the target arteries and bronchus of the target segment and the adjacent segment were exposed. An additional advantage of the splitting technique is that early division of the intersegmental plane significantly facilitates completion of the division of the intersegmental plane of the adjacent lung subsegment [24]. After obtaining such an anatomical plane extension, precise anatomical details such as lung subsegments, surgical margins, and intrapulmonary lymph nodes are exposed to the visual field. Here, this splitting technique presented the new concept of atypical subsegmentectomy, which centers on the lesion to obtain adequate surgical margins. The location of the tumor determines the surgical type. Sufficient surgical margins were obtained in all patients in this study.
Our data analysis revealed that there are prerequisites for implementing the splitting technique. The patients were selected if they had an early pathological stage, a small tumor diameter, or a depth ratio that was not deep. First, our indications for subsegmentectomy were strictly controlled, and we did not select patients who were considered to have no benefit in the JCOG0802 study. Second, in the early period of this technique, we were slightly conservative in our selection of patients. Due to a poor medical environment, lobectomy was not guaranteed. Now, that attitude has gradually changed, the technology has matured, and confidence has increased. At the technical maturity stage, in patients with a tumor diameter of 1.7 cm, a CTR of 60% and a pathological type of invasive adenocarcinoma, we also performed satisfactory lobar splitting conical subsegmentectomy with a surgical margin of 2 cm and satisfactory surgical results, as shown in Table 2. Third, lobar splitting conical subsegmentectomy also has certain requirements for the position of lung nodules. When the nodule is located in the inner third lung field, subsegmentectomy satisfying the surgical margin may damage the arteriovenous space of the hilar. However, when the nodules are located in the outer third lung field, wedge resection of the lung may be used to achieve good surgical results.
Considering the complexity of the procedure and the presence of more than one intricate intersegmental plane, lobar splitting conical subsegmentectomy is considered complex. Therefore, conventional segmental resection techniques, such as "cone-shaped segmentectomy", sharp-blunt dissection, "work-plane extension", and "gate" opening, all contribute to the accuracy of lobar splitting [13, 23]. In terms of the surgical approach, the ligament approach is often chosen for the lower lung lobe, and surgeons can identify V6, A8 and the bronchus by oblique fissure of the lung. Signs of subsegmentectomy in the upper lobe are usually A1 + 2c in the posterior mediastinal approach; A2b and A3b in the lobar fissure approach; and the lingual vein in the anterior mediastinum approach [24, 25, 26, 27, 28].
Limitations
Due to the need to review the details of surgical video replay, this study was not a prospective randomized controlled study. This study included only patients who underwent single-center or single-operation surgeries to avoid confounding factors. In light of this, there may be some deviance in generalization and application based on the findings of this study.