Clinical application of flexible and variable transparent endport technology in minimally invasive neuroendoscopic keyhole surgery: a practical new technology

Abstract

With the development of endoscopic technology, neuroendoscopy utilizes its advantages such as good illumination, close range observation, and flexible degrees of freedom. Neuroendoscopic surgery can achieve advantages such as minimally invasive, high clearance rate, low incidence of complications, good brain tissue protection, and fewer surgery-related injuries. However, minimally invasive endoscopic surgery also has inherent limitations, since its narrow surgical channels are prone to collapse and require special instrument support. By summarizing the literature on the use of endoport technology in previous neuroendoscopic surgeries, and providing a detailed introduction and summary of our team’s newly developed simple variable endoport clinical experience, we analyzed the advantages, disadvantages, and precautions of flexible and variable transparent endport technology. After years of development and refinement, fixed endoport technology has been widely used in neuroendoscopic surgery, but it has certain shortcomings. Our team has developed a variable endoport system using simple and easily accessible materials. Although it has shortcomings in support, it provides good compensation for the flexibility of endport length and diameter, which is of great help for multi-instrument operation and bipolar electrocoagulation hemostasis, making surgical hemostasis more reliable. Meanwhile, the flexible and variable transparent endport system can be completely placed within the bone window, with significantly higher mobility than the hard endport system that cannot be completely placed below the bone window. The flexible and variable transparent endport system material is easy to obtain, manufacture, operate, and has extremely low cost, making it suitable for promotion and use in the vast majority of neurosurgery units, including primary hospitals.

Introduction

With the increasing interest in minimally invasive surgical techniques in neurosurgery, modern neuroendoscopic surgery has been established and rapidly developed. It has the advantages of minimally invasive, high clearance rate, low complications, good brain tissue protection, and reduced surgery-related damage¹. Liu et al.‘s research² shows that minimally invasive endoscopic surgery for cerebral hemorrhage has shown encouraging results in multicenter randomized controlled clinical studies. Although neuroendoscopy has advantages such as good illumination, close range observation, and flexible degrees of freedom in minimally invasive surgery, there are still some problems and challenges in clinical practice, such as how to provide sufficient operating space during the surgical process and protect important nerves, blood vessels, and other structures in the surgical channel. Based on the clinical experience of transnasal endoscopy and ventriculoscopy, endoport technology has emerged and effectively solved the above-mentioned problems¹. Endoport technology is a circular tubular support system that can establish a safe and transparent surgical channel for neuroendoscopic operations, effectively reducing traction and collateral damage to the surrounding brain tissue of hematomas or lesions, and clearing hematomas or lesions by pushing rather than cutting off peripheral nerve fiber bundles. The endoport technology currently used in clinical practice is a hard endport, which has certain shortcomings during use. On the basis of summarizing clinical practice, our team has newly developed a simple variable endport (flexible and variable transparent endport, FVTE) system, which effectively compensates for the shortcomings of hard endports and develops endport in endport technology, greatly facilitating minimally invasive endoscopic keyhole surgery.

Endoport system and usage method

Hard endport system

An insertable adjustable sleeve similar to a nasal dilator

Zhang et al.¹ reported the application of an insertable adjustable sleeve similar to a nasal dilator in minimally invasive surgery for clearing basal ganglia cerebral hemorrhage through a neuroendoscopic keyhole approach. It resembles a nasal dilator, with a solid bullet-head probe inserted into the sleeve’s center (Fig. 1A). This design prevents the sleeve from cutting brain tissue during expansion (Fig. 1B). After reaching the predetermined depth, slowly open the sleeve and pull out the inner part to form a narrow surgical channel into the hematoma cavity. Then, guided by neuroendoscopy, a suction device is used to remove the hematoma and bipolar electrocoagulation is used for hemostasis. After the surgery is completed, the trocar is first reduced and slowly withdrawn. This type of expander is actually composed of two semi-circular sleeves. During the process of opening the brain tissue to form a surgical channel, it can be clearly observed that the surrounding brain tissue is subjected to uneven force. On the surface without a tube, the brain tissue is actually subjected to tearing force (Fig. 1C: the force on surface a is uniform, and the tearing force on surface b is towards both sides), which can cause brain tissue damage and bleeding.

Fig. 1.

An insertable adjustable sleeve similar to a nasal dilator¹.

Fixed endport

Chen et al.³ developed a specialized stainless-steel metal endport system consisting of a hollow endport and a solid bullet core (Fig. 2A). Nishihara et al.⁴ upgraded it to a transparent endport (Fig. 2B), which can provide better visibility. However, in order to avoid secondary damage such as transient intracranial hypertension caused by the large volume of the endport tube during insertion, these two systems are designed with a endport tube diameter that is thin and too long, which limits the flexibility of surgical operations. At the same time, bipolar electrocoagulation hemostasis cannot be performed, making hemostasis difficult. If active bleeding is found during surgery, it is still necessary to enlarge the incision and replace it with microscopic surgery for hemostasis.

Fig. 2.

Metal and transparent long endport^3,4.

Homemade syringe endport

Li et al.⁵ and Singh et al.⁶ improved the syringe to form a transparent endport system, using locally sourced materials that balance affordability and convenience. Additionally, endport systems of different sizes and lengths can be designed based on the volume of the syringe, resulting in higher flexibility (Fig. 3A and B). However, due to the cutting of the end of the syringe, the edges are relatively sharp, which inevitably causes cutting damage to brain tissue, and the syringe material is hard plastic, making it difficult to cut.

Fig. 3.

Self-made syringe endport^5,6.

Commercial endport

At present, there are many common endoscopic assisted endports on the market, with various shapes such as circular (Fig. 4 Laiwo disposable brain guide catheter, LW101006 II type) or elliptical (Fig. 5 Laiwo disposable brain guide catheter, LW171107), as well as endports with reserved guide catheter channels (Fig. 6 Kezhong disposable tissue traction expansion catheter), and catheter endports with balloons (Fig. 7 Shenzhen Qingyuan Medical Equipment). These endports typically have a diameter of 1.3–2.7 cm, a depth of approximately 3–7 cm, and occupy a volume of approximately 10-15ml⁷. These endport systems are all commercial products, with shortcomings such as high prices and some medical centers being unable to equip them.

Fig. 4.

Laiwo disposable brain guide catheter, LW101006 Type II.

Fig. 5.

Laiwo disposable brain guide catheter, LW171107.

Fig. 6.

Kezhong disposable tissue traction expansion catheter.

Fig. 7.

Catheter endports with balloons (Shenzhen Qingyuan Medical Equipment).

The simple variable endport (Flexible and variable transparent endport)

Whether it is the various self-made endports mentioned above or various mature commercial endports, their depth and diameter are basically fixed, and there are still certain shortcomings in dealing with various complex clinical conditions. Therefore, our team has developed a simple and variable endport (Fig. 8), which not only has the advantages of convenient material selection and simple production, but also has the ability to change depth and diameter at any time, making it more flexible and practical to use. The material is a sterile saline bag used during surgery, its non-printed side is cut into a rectangular shape of appropriate size and then coiled into an endport tube of appropriate size. Before inserting the endport into the brain tissue, it is curled into the smallest diameter sleeve as much as possible, and then gradually released and expanded along the puncture channel into the hematoma cavity to form a hollow tubular channel (Fig. 8C and D). At the same time, a small endport can also be inserted into the large endport to form the endport in endport technique (Figs. 10I, 12E, and 13O). But also, because it is curled from sterile saline bags and lacks hardness, it has the disadvantage of insufficient support for patients with extremely high intracranial pressure.

Fig. 8.

Simple variable endport (flexible and variable transparent endport) material and manufacturing process.

Fig. 10.

Variable endport (flexible and variable transparent endport) usage method II (A) Use an intraventricular drainage tube to puncture the hematoma, and aspirate a portion of the hematoma for initial blood pressure reduction. (B, C) Use a commercial fixed endport to puncture the hematoma and form an endoscopic surgical channel. (D, E) Replace with a variable endport (flexible and variable transparent endport). (F–H) Slowly unfold the variable endport (flexible and variable transparent endport) to form a more flexible endoscopic surgical channel. (I) Inserting smaller variable endports (tiny flexible and variable transparent endports) deep to form a endport in endport technique.

The concept of “two-in-one technique” surgery and the method of using a simple variable endport (flexible and variable transparent endport)

Our early study⁷ simulating the increase in intracranial pressure during endport insertion showed that when the endport tube entered 5 ml of brain tissue, the intracranial pressure increased from 14mmHg to 18mmHg; When the endport enters 10 ml of brain tissue, intracranial pressure will rapidly increase to 30mmHg; When the endport enters 15 ml of brain tissue, intracranial pressure rapidly rises to 47mmHg. Therefore, in the process of minimally invasive endoscopic keyhole surgery, if an endport tube is directly inserted without pre decompression, it will cause a sharp increase in intracranial pressure and lead to serious side injuries. Based on extensive clinical practice, our team has pioneered the " two-in-one technique” surgical approach, which involves the first step of performing intracerebral hematoma aspiration (Fig. 10A), followed by the insertion of an endport after a certain degree of decompression. This step has two clear benefits: firstly, it reduces intracranial pressure in advance, avoiding the side damage caused by the instantaneous increase in intracranial pressure caused by endport insertion; Secondly, puncture and aspiration of blood can locate the hematoma and indicate the direction and depth for endport insertion, avoiding side injuries caused by inaccurate puncture and repeated punctures.

Directly inserting a simple variable endport (flexible and variable transparent endport) into brain tissue can cause serious cutting injuries, so it is necessary to establish a good channel in advance. Based on our clinical practice, we provide three methods: (1) After hematoma puncture and aspiration to reduce intracranial pressure (ICP), a self-made balloon expander is used to uniformly expand and form a channel. Then, with the assistance of cotton pads, a curled variable endport is inserted. Finally, a suction device and bipolar electrocoagulation are used to gradually expand the channel (Fig. 9). (2)After hematoma puncture and aspiration to reduce ICP, a smaller commercial endport tube is used to puncture into the hematoma cavity. The suction device further aspirates the hematoma to reduce blood pressure, and then replaced with a variable endport to continue clearing residual hematoma and stopping bleeding (Fig. 10). Its advantage is that it can utilize a transparent fixed endport for visual catheterization, while providing rigid support to maintain a stable surgical channel when intracranial pressure is high. After the hematoma is further cleared, intracranial pressure further decreases. Replacing with a variable endport can better perform multi-instrument operation and hemostasis. At the same time, because the variable endport tube is fully inserted into the bone window (Fig. 10F-H), it has higher flexibility, effectively avoiding the inherent shortcomings of a fixed endport tube (insufficient space for multi-instrument operation, limited by keyhole, and insufficient endport movement range). (3)After hematoma puncture and aspiration to reduce ICP, we use a suitable PP polypropylene centrifuge tube (10 ml) for disinfection and use it as the inner part of the variable endport. The trimmed and suitable variable endport is tightly wrapped around the centrifuge tube, and the endoscope is inserted into the centrifuge tube for visual catheterization. After the endport is placed in the hematoma cavity, the centrifuge tube is withdrawn to leave the variable endport in the formed puncture channel (Fig. 11). Regardless of the method used, when establishing the surgical corridor for the first time, we recommend placing the endport to the deepest part of the hematoma to prevent collapse of brain tissue after the removal of superficial hematoma from obstructing the clearance of deep hematoma.

Fig. 9.

Method (A) for using the variable endport (flexible and variable transparent endport): A self-made puncture channel balloon expander is used, and a sterile glove finger is used to form a balloon system with the ventricular puncture drainage tube. (B–D) Use a self-made balloon expander to puncture the hematoma and inject water to expand and form a puncture channel. (E–G) Lay cotton pads along the puncture channel to protect brain tissue, and place the rolled endport along the cotton pads into the channel. (H) Slowly unfold the variable endport (flexible and variable transparent endport) to form an endoscopic surgical channel.

Fig. 11.

Usage of Variable Endport (Flexible and variable transparent endport) (A) Variable Endport (Flexible and variable transparent endport) and Inner Endport (PP Polypropylene 10 ml Centrifuge Tube). (B, C) Tightly wrap the variable endport (flexible and variable transparent endport) around the surface of the centrifuge tube to form the endport and inner system. (D) Visual puncture under neuroendoscopy. (E) Slowly withdraw from the centrifuge tube after successful puncture. (F) Form an endoscopic surgical channel.

Typical cases

Case 1

A 51 years old female patient, admitted to the hospital due to “sudden consciousness impairment for 2 hours”. The patient had a sudden onset of slurred speech, accompanied by vomiting, and gradually developed consciousness disorders 2 h before admission. She was sent to our emergency department by ambulance, and the cranial CT showed brainstem hemorrhage (Fig. 12A). Preoperative marking of the curved minimally invasive surgical incision line in front of the right auricle (Fig. 12B). During the operation, we first inserted the first flexible and variable transparent endport (outer endport) to form a wide endoscopic surgical channel (Fig. 12C-D), which was separated to the site of the brainstem hematoma rupture. Then, we inserted the second small flexible and variable transparent endport (endport in endport) to form a deep micro endoscopic surgical channel (Fig. 12E-F), protecting normal brainstem tissue and surrounding blood vessels and nerves. Under neuroendoscopy, the brainstem hematoma was completely cleared (Fig. 12G-H). Postoperative CT scan showed complete clearance of hematoma (Fig. 12I). Using 3D Slicer software to accurately calculate preoperative hematoma volume of 8.8 ml, postoperative residual hematoma of 1.4 ml, and hematoma clearance rate of 84.1% (Fig. 12J-K). The patient underwent tracheotomy on the second day after surgery to open the usual airway. 14 days after surgery, vital signs stabilized and the patient was transferred to a rehabilitation hospital for further rehabilitation treatment. Unfortunately, the patient was still in vegetative state during a 3-month follow-up call after surgery.

Fig. 12.

Application of flexible and variable transparent endport in neuroendoscopic brainstem hematoma removal surgery.

Case 2

A 42 years old male patient, admitted to the hospital due to “sudden consciousness impairment for 4 hours”. The patient experienced sudden consciousness impairment with vomiting 4 h before admission and was urgently sent to our hospital by ambulance. A cranial CT scan showed bilateral lateral ventricle and third ventricle bleeding casts. Medical history: Two years ago, due to ventricular hemorrhage caused by Moyamoya disease, underwent extracranial drainage and right superficial temporal middle cerebral artery bypass surgery. Emergency cranial CT scan after admission showed bilateral ventricular and third ventricular hemorrhage, with ventricular casting (Fig. 13A-C). In order to avoid the bypass surgery area in the superficial temporal brain of the patient on the right side, we chose a minimally invasive keyhole approach in the left frontal region and marked the incision line (Fig. 13D). During the operation, a fixed endport (hard endport) is first inserted to form an endoscopic surgical channel (Fig. 13I), and most of the hematoma is cleared and decompressed under neuroendoscopy (Fig. 13J). In order to obtain more surgical space, a more flexible flexible and variable transparent endport was replaced (Fig. 13K-L). Under the assistance of a flexible and variable transparent endport (outer endport), bilateral intraventricular hematomas were continued to be cleared, and active bleeding arteries were found. Bipolar electrocoagulation was performed under neuroendoscopy to stop bleeding (Fig. 13M-N). Continue to insert the second small flexible and variable transparent endport to form a deep endoscopic surgical channel (endport in endport) (Fig. 13O), and thoroughly remove the hematoma in the third ventricle (Fig. 13P). Postoperative cranial CT showed complete clearance of hematoma in both lateral ventricles and third ventricle (Fig. 13E-H). Accurately calculate the preoperative hematoma volume of 75.7 ml and the postoperative residual hematoma of 0.2 ml using 3D Slicer software, with a hematoma clearance rate of 99.7% (Fig. 13Q-R). On the 5th day after surgery, the patient underwent tracheotomy to open the airway due to airway obstruction. At admission, the GCS score was E1V1M5. On the 25th day after surgery, the patient was discharged from another hospital for further rehabilitation treatment. At discharge, the GCS score was E4VTM5. Three months after surgery, the patient was followed up by phone and basically resumed self-care.

Fig. 13.

Application of variable endport (flexible and variable transparent endport) in neuroendoscopic minimally invasive keyhole intracerebral hematoma removal surgery.

Discussion

Minimally invasive surgery has always been a goal pursued by neurosurgeons. With the development of endoscopic technology, the resolution and size of neuroendoscopy have been significantly improved, and its application in minimally invasive neurosurgery has developed rapidly. However, neuroendoscopy has inherent limitations, as narrow surgical channels are prone to collapse and require special instrument support, such as brain pressure plates, tubular retractors, etc. Neuroendoscopic surgery typically requires a brain spatula to pull brain tissue and expose a channel. When the brain spatula pulls brain tissue, it may cause side effects such as cortical cutting, especially when multiple brain spatulas are needed for continuous retraction. In addition, due to the edge embedding effect of the brain pressure plate contact surface, it may lead to local normal brain tissue being compressed and ischemic⁸. Since the concept of endoport technology was proposed in the 1980s, in the following nearly 40 years, endoport technology, together with neuroendoscopy, has revolutionized minimally invasive neurosurgery⁹. Endoport technology can effectively avoid the above-mentioned defects and has been proven to be safe and effective for deep hematomas or lesions. The annular endport uniformly applies pressure to the brain tissue around the channel without edge trapping effect, effectively reducing damage to normal brain tissue^10,11. Chen et al.³ designed a metallic neuroendoscopic protective endport with clear surgical field and convenient hemostasis. However, this endoscopic working endport cannot effectively understand the surrounding conditions of the channel and surgical field, and cannot display the anatomical relationship between brain tissue and lesions. In this case, blindly moving the endoscopic endport will further increase the chance of iatrogenic injury. Nishihara et al.⁴ upgraded it to a transparent material endport, which can provide better visibility, but there are still certain defects. Their research⁴ shows that the effectiveness of neuroendoscopic surgery is significantly affected by the visibility of the surgical field, with transparent annular endports providing a significantly better surgical field than metal or opaque annular endports.

In recent years, various commercial transparent circular endports have emerged one after another. Apart from differences in appearance and material, their functions are basically the same. Clinical practice has shown that they can better distinguish between hematomas and normal brain tissue on the basis of open surgical channels, and easily verify the clearance of hematomas^2,12. The circular endport reduces the incidence of postoperative complications by visualizing the intermittent separation of nerve fiber bundles, but there is no direct evidence of nerve fiber bundle preservation reported yet⁹. Liu et al.⁹ introduced a novel balloon catheter kit for clinical application in intraventricular lesion surgery, which protects against collateral damage during expansion by limiting the diameter of the balloon or endport. Numerous previous literature reports^1,2,5 on the clinical application of various hard endport systems, summarizing their advantages in neuroendoscopic surgery: Firstly, the front end of the hard endport system is bullet shaped, which can abruptly separate brain tissue during puncture and expansion, protecting nerve fiber bundles. Secondly, with the visualization of puncture under neuroendoscopy, the puncture direction can be adjusted in a timely manner to accurately reach the hematoma cavity or lesion. Again, marking precise scales based on the hard endport system can help surgeons accurately determine the depth of surgery. Fourthly, the hard endport system can provide good support, avoiding brain tissue collapse caused by hematoma or lesion clearance during surgery, and reducing the difficulty of surgical operations. Fifth, the hard endport system limits the entire surgery to a certain area, such as the hematoma cavity or tumor cavity, thereby reducing the risk of iatrogenic damage to normal brain tissue structures near the surgical area. The fixed nature of the hard endport system also exposes its shortcomings: Firstly, the neuroendoscopic keyhole technique has a small bone window, and a portion of the hard endport system is located outside the bone window. Due to the limitation of the bone window size, the mobility of the endport is restricted. Secondly, due to its fixed length and diameter, the hard endport system is difficult to meet the flexible and variable needs during surgery. For example, if the endport is too long, it can easily limit the operation of surgical instruments, and if the endport is too short, it can lead to insufficient depth and brain tissue collapse, affecting the surgical field of view. Thirdly, if the hard endport system is too thick, it can cause a sudden increase in intracranial height during expansion, leading to collateral damage. If it is too thin, it can also cause interference between instruments, making surgical operations difficult. Fourthly, due to the limitations of commercial prices and consumables, some medical centers or patients cannot afford the expensive costs. In order to overcome the shortcomings of the hard endport system mentioned above, our team has developed a new flexible and variable transparent endport(FVTE) system using simple and easily accessible materials. This technique is similar to the Tubular Brain Retractor technique reported by Rakesh et al. and Yadav et al.^{13]– [14}, and introduces three new operating techniques(Figs. 9, 10 and 11). Although there are defects in the support function, it has good compensation in terms of the length of the endport (variable length) and the flexibility of the diameter of the tube (variable diameter). It is of great help for multi device operation and the use of bipolar electrocoagulation hemostasis, making bipolar hemostasis more reliable than using only a monopolar electrocautery. Meanwhile, the flexible and variable transparent endport system can be completely placed within the bone window (Fig. 10F-H), and its mobility is significantly higher than that of the hard endport system that cannot be completely placed below the bone window (Fig. 10B); Finally, it is also very important to note that our flexible and variable transparent endport system material is easy to obtain, manufacture, and has extremely low costs, making it suitable for the vast majority of neurosurgical units, including primary hospitals.

We have summarized the precautions for using a circular endport based on past clinical experience: Firstly, before inserting the endport, perform hematoma aspiration or intraventricular drainage to reduce blood pressure, and gradually transition from a thin diameter endport to a thick diameter endport to avoid side damage caused by a sharp increase in intracranial pressure. Secondly, the surgical approach should be chosen along the long axis of the hematoma or tumor shape to obtain a larger operating angle and reduce the amplitude of the endport swinging. Even if swings within a certain safe range is required, it should be done after sufficient decompression and relaxation of the brain tissue to reduce the resulting side damage. Thirdly, before inserting the endport, fully free the soft meninges on the surface of the brain tissue and create a cortical fistula, which can reduce bleeding and mechanical tensile damage. Fourth, minimize the number of insertions as much as possible to reduce damage such as cutting normal brain tissue. Fifth, in the three ways of using the flexible and variable transparent endport system, attention should be paid to protecting brain tissue and avoiding cutting related injuries.

Endoport technology is an essential tool for minimally invasive keyhole surgery with neuroendoscopy, which can establish a safe and transparent surgical channel for neuroendoscopic operations. Our team’s newly developed flexible and variable transparent endport system has many advantages such as easy material acquisition, easy manufacturing, extremely low cost, simple usage, and strong clinical practicality. It is worth promoting and applying in minimally invasive surgeries in neurosurgery units of various medical centers.

Author contributions

Qiang Cai and Fangjun Cao studied concept and design, critical revision of manuscript for intellectual content, acquisition of data.Long Zhou, Shitao Mao and Can Wang collected and analysised data, and wrote the main manuscript.Huikai Zhang, Zhiyang Li, Minghui Lu, Wei Xia, Ping Song, Hui Ye, Jinjian Zhou, Zohaib Shafiq and Qianxue Chen collected and interpretated of data.All authors reviewed the manuscript.

Funding

This work was supported by National Natural Science Foundation of China (82271518; 81971158; 81671306); The Interdisciplinary Innovative Talents Foundation from Renmin Hospital of Wuhan University (JCRCFZ-2022-030); Guiding projects of traditional Chinese medicine in 2023 ~ 2024 by Hubei provincial administration of traditional Chinese medicine (ZY2023F038).

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.

Ethical approval

All patients or their families have agreed to publish pictures and imaging materials with identifiable personal information removed, and have signed a consent form. We confirm that we have obtained informed consent from all subjects and/or their legal guardians. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This study was approved by the ethics committee of Clinical Research, Renmin Hospital of Wuhan University (WDRY2023-K139).