Here we present a training and testing system where a trainee can complete manual vascular reconstruction in vitro individually using a magnetic anchoring technique. The system can also be used to test the quality of reconstruction.
Manual vascular reconstruction training is essential for a beginner surgeon. However, an optimal training system for vascular reconstruction in vitro has yet to be developed. In this study, we introduce an in vitro training and testing system using a magnetic anchoring technique with which a trainee can practice manual vascular reconstruction individually. Additionally, this system can also be used to test the quality of the reconstruction. The described system includes a vascular reconstruction training machine, magnetic tractors, and a magnetic suture puller. In this manuscript, we detail an end-to-end vein anastomosis using porcine right and left iliac veins. To identify the potential damage caused by a magnetic suture puller on the suture, we created three groups with six segments of 4-0 polypropylene sutures each: a control group with no intervention on the polypropylene suture, a group in which the polypropylene suture is manually pulled with sterile gloves 20x, and a magnetic puller group in which the magnetic puller pulled the polypropylene suture 20x. These groups were tested by light microscopy and breaking strength tests, and the effect of reconstruction was assessed. In the light microscopy test, the control group was less likely to be damaged (p < 0.05) and the number of damaged points of the manual group and magnetic puller group were similar (p > 0.05). The results of the breaking strength test were compared across groups and no significant difference was observed (p > 0.05). The end-to-end anastomosis of the porcine iliac veins was successfully performed using this training system, and the reconstructed veins could undergo 2.0 kPa perfusion pressure. Using this training and testing system the trainee can practice manual vascular reconstruction in vitro individually with the aid of magnetic tractors and a magnetic suture puller, and the quality of the reconstruction can be tested.
Vascular reconstruction is a basic skill required for surgeons. Although Obora1 and Holt2 invented several mechanical reconstruction methods to simplify the reconstruction of small vessels (diameters <10 mm), these methods are not commonly applied in macrovascular anastomosis. Manual vascular anastomosis is still performed in many operations, including vascular surgery3, emergency surgery4, and solid organ transplantation5. Thus, it is essential for surgeons to practice manual vascular anastomosis. However, an optimal training system for vascular reconstruction in vitro is uncommon, and inexperienced surgeons must undergo considerable training in vivo on large animals6 before they can master the technique. Because failure is inevitable during initial training, many animals are likely to die of vascular complications, which is concerning regarding animal welfare. Further, during the procedure of end-to-end vascular reconstruction, to avoid mistakes in stitch positions or loose sutures, the surgeon needs at least one assistant to expose the posterior vascular wall and pull the suture. Thus, vascular reconstruction usually cannot be performed by the surgeon individually, and the efficiency of preparation is usually limited by the proficiency of the assistant.
Magnetic anchoring surgery has become a topic of interest in recent years7,8,9,10,11. The clinical trial by Rivas et al.7 showed that with his magnetic surgical instrument and following the principle of magnetic anchoring, surgeons can perform reduced-port laparoscopic cholecystectomy. The use of this instrument also allows for a reduced role for the assistant during open surgery. Through the magnetic field, the magnetic device is adsorbed onto an anchoring point. This magnetic anchoring device can act as a mechanical arm, grasping and retracting the tissue or organ, exposing the surgical field, and simplifying the operation. Based on this rationale, we invented magnetic tractors to retract the vascular wall and suture, and a magnetic suture puller to pull the polypropylene sutures.
The use of a vascular reconstruction training machine was another milestone in this study. It consists of an operating floor and a control panel: the vasculature is fixed on the operating floor, and the trainee can practice on it. After anastomosis, the trainee can set the perfusion parameters on the control panel in order to test the quality of anastomosis. Compared to previous vascular anastomosis training systems6,12,13,14, the use of this system provides two main advantages: First, magnetic devices can be used to expose the surgical field, so that the trainees can practice on it individually. Second, the trainee can check the effect of anastomosis using a perfusion test.
In the present study, we introduce a training and testing system where the trainee can complete manual vascular reconstruction in vitro individually using a magnetic anchoring technique and the quality of reconstruction can also be tested. Limited by the design and size of the water inlet and water outlet on the operating floor, the training system can only perform end-to-end reconstruction on vessels with a >5 mm diameter.
The protocol was carried out in accordance with the Guidelines for the Care and Use of Laboratory Animals and was approved by the Committee on the Ethics of Animal Experiments of Xi'an Jiaotong University, Xi'an, Shaanxi Province, China.
1. Preparation prior to the training
NOTE: The vascular reconstruction training machine is shown in Figure 1. It consists of a control panel and an operating floor.
2. Fix the veins on the operating floor
3. Anastomosis of posterior walls
4. Anastomosis of anterior walls
5. Test the effect of anastomosis
6. Checking the safety of the magnetic suture puller
NOTE: To test whether the magnetic suture puller damaged the polypropylene suture, perform the breaking strength and light microscopy tests. In this experiment, three groups with six segments of 4-0 polypropylene suture in each were tested: a control group with no intervention on the polypropylene suture, a manual group in which the polypropylene suture was manually pulled with sterile gloves 20x, and a magnetic puller group in which the magnetic puller pulled the polypropylene suture 20x.
The vascular reconstruction training machine is shown in Figure 1 and includes two main parts: the operating floor and the control panel. The operating floor consists of a water inlet, a water outlet, and a water storage basin. The two ends of the vasculature are tied to the water inlet and water outlet to test the effect of anastomosis. The length of the water outlet is adjustable, and we set the parameters (e.g., the perfusion pressure, duration of peak pressure, temperature, and pressure deviation) on the control panel. In addition, we can observe the pressure curve on the control panel when the vasculature is tested.
The magnetic suture tractor and the magnetic vascular tractor are shown in Figure 3. The length of the traction wire is 30 cm, and the traction force increases with the lengthening of the traction wire (Figure 2). The range of the magnetic tractor's traction force is 0–1.8 N, which covers the range of traction force required for suture and vascular traction.
Photos of the magnetic suture puller are shown in Figure 4A,B. The three magnetic balls have a diameter of 5 mm, and the magnetic cylinders have a diameter of 5 mm and a height of 5 mm. These can be replaced by smaller or bigger ones. The suture pulling force will change accordingly.
In testing the effect of anastomosis, a time-perfusion pressure curve was generated and is shown in Figure 5. The perfusion pressure ascended to 2.0 kPa, which we set as the peak pressure. This was maintained for 5 s, which was set as the duration of peak pressure.
Regarding the safety of the magnetic suture puller, we tested whether the magnetic suture puller damaged the polypropylene suture using a breaking strength test and a light microscope. As shown in Figure 6, the breaking strength test results of the three groups were compared pairwise, and no significant difference was observed (p > 0.05). As shown in Figure 7, the control group was less likely to be damaged (p < 0.05), but the number of damaged points in the manual group and the magnetic puller group were similar (p > 0.05).
Figure 1: The vascular reconstruction training machine's two main parts. The operating floor and the control panel. Please click here to view a larger version of this figure.
Figure 2: The association between the length of the traction wire and the traction force. The length of the traction wire was 30 cm, and the range of traction force that the magnetic tractor could provide was 0–1.8 N. Please click here to view a larger version of this figure.
Figure 3: The magnetic suture tractor and the magnetic vascular tractor. (A) Magnetic suture tractor. (B) Magnetic vascular tractor. Please click here to view a larger version of this figure.
Figure 4: The magnetic suture puller. (A) Front view. (B). Lateral view. The magnetic suture puller consists of a quasi-oval polylactic acid board with a thickness of 2 mm, a major axis diameter of 10 cm, a minor axis diameter of 2 cm, three magnetic balls with diameter of 5 mm, and three magnetic cylinders with a diameter of 5 mm and a height of 5 mm. Please click here to view a larger version of this figure.
Figure 5: Time-perfusion pressure curve. The perfusion pressure ascended to 2.0 kPa, which we set as the peak pressure. It was maintained for 5 s, indicating that the anastomosis was successful. Please click here to view a larger version of this figure.
Figure 6: The breaking strength test. (A) The association between the length of the polypropylene suture and the tension. (B). Comparison of the breaking strength among the three groups. There was no significant difference in the three groups (p > 0.05). Please click here to view a larger version of this figure.
Figure 7: The light microscope tests. (A) Control group. (B) Manual group. (C) Magnetic puller group. (D) Comparison of the number of damage points among the three groups. The control group had fewer damage points (p < 0.05), but there was no significant difference between the manual group and the magnetic puller group (p > 0.05). The black arrow points to the damage point. The asterisk represents the significant difference. Please click here to view a larger version of this figure.
With the help of magnetic tractors and a magnetic suture puller, a trainee can complete vein anastomosis individually and precisely. Magnetic tractors pull the tissue that blocks the anastomosis field and provide suitable strength for stretching the veins in a vertical direction, thus achieving clear exposure for vein anastomosis. In traditional manual anastomosis, at least one assistant is required for surgical exposure. The use of magnetic tractors could achieve the required exposure and substitute for assistants. In addition, the traction force of the magnetic tractor was dependent on the length of the traction wire, so we could adjust the site that the magnetic tractor was adsorbed onto in order to change the length of the traction wire to obtain a suitable traction force. In contrast to traditional manual anastomosis, the traction force in this study was quantifiable by the length of the traction wire. This allowed us to avoid some issues resulting from too heavy or too light a traction force, such as tearing of the vasculature and unclear exposure.
The magnetic suture puller was another novel invention in this study. It replaced the requirement for an assistant to pull the suture to prevent the previous suture from loosening, resulting in anastomotic leakage. Because it pressed the polypropylene suture, we tested the degree of damage caused by the magnetic suture puller and compared it to intact and manual pulling. Although the number of damage points in the magnetic puller group was more than in the control group (intact polypropylene sutures), it was similar to that observed in the manual pull that is widely used in clinical practice. Moreover, the breaking strength test showed a similar breaking strength among the three groups. With the microscope, we found that the changes caused by the magnetic puller were too small to damage the strength of the polypropylene suture.
It must be emphasized that the tension on the vertical and parallel directions of the vasculature during anastomosis is significant. Therefore, it is vital to adjust the length of the water outlet of the training machine as well as the position of the magnetic tractors. In addition, as we add sutures, we pick the most suitable magnetic ball to press the suture so that the tension on the suture is moderate. Moreover, to avoid stenosis after anastomosis, it is essential to keep the same suture margin, needle spacing, and "growth factor".
If the trainee wishes to practice anastomosis using vasculature with a greater or smaller diameter, the magnetic balls and cylinders of the magnetic suture puller should be replaced by bigger or smaller ones, so that the pulling force changes accordingly. Simultaneously, the test parameters after anastomosis should be adjusted. In the current version of the vascular reconstruction training machine, the diameter of the inlet and outlet is only 5 mm, making it difficult to use on smaller diameter vessels. Fortunately, the inlet and outlets are detachable, so the current inlet and outlet can be replaced by smaller ones that allow changes in vessel size.
Beside the sizes of the inlet and outlet, there are still some limitations to this training system. Because there is only one water inlet and one water outlet, this training and testing system is only applicable to end-to-end anastomosis, and trainees cannot practice end-to-side or side-to-side anastomosis using this system. Additionally, the surgical instruments used in this video (e.g., the needle holder and scissors) are ferromagnetic stainless steel. They were absorbed by the magnetic tools occasionally, which could interfere with the training progress. If conditions permit, the surgical instruments can be replaced with non-ferromagnetic titanium instruments.
Open surgical vascular simulators are generally divided into two types: in vivo and in vitro. Tang6 developed a novel technique for vascular reconstruction in vivo using ewes as animal models. Although this technique provided a more realistic operation scene, the use of in vivo animal models is both inconvenient for training and costly. Shimizu12 and Maluf13 invented in vitro training devices for cerebrovascular anastomosis, while Bismuth14 introduced a vascular surgery course named Cardiovascular Fellows Bootcamp for cardiovascular surgery education. Although the rationale of our training system is similar to those outlined in these studies, no previous study has recommended the use of a device to assist in exposing surgical field and maintaining the tension of the suture. Thus, the training previously described must be completed by at least two trainees. Also, previous researchers did not introduce a way to precisely check the quality of anastomosis. Therefore, compared to these open vascular simulators, our technique is economical, convenient to practice individually, and effective in terms of feedback training quality.
We intend to add smaller water inlets and water outlets to the vascular reconstruction training instrument so that trainees can practice other types of anastomosis. We expect that magnetic tractors and suture pullers will be used to help surgeons expose the surgical field in routine clinical operations in the future.
In summary, we introduce a training and testing system where the trainee can complete manual vascular reconstruction in vitro individually with the aid of magnetic tractors and a magnetic suture puller
The authors have nothing to disclose.
This work was supported by grants from the Ministry of Education Innovation Team Development Program of China (No. IRT1279).
Circular permanent magnet | Hangzhou Permanent Magnet Group Co.LTD | 20*1mm | Magnetic tractor |
Magnetic balls | Hangzhou Permanent Magnet Group Co.LTD | 5mm | Magnetic suture puller |
Magnetic cylinders | Hangzhou Permanent Magnet Group Co.LTD | 5*5mm | Magnetic suture puller |
Polypropylene suture | Johnson and Johnson | PROLENE 4-0 | Used for anastomosis |
Silk suture | SILK | 2-0,3-0 | Used for fixing vascular and ligation |
Surgical insturments | Jinzhong Shanghai | JZ-2018 | Suture scissors, tissue scissors, forceps, needle and needle holder |
Universal testing machine | Zwick GmbH&Co | Z010 | Used for testing the association between the length of traction wire and the traction force |