A Needle Tip Quality-Controlled Training Protocol for Cerebrovascular End-to-Side Bypass: From Bench to Bedside

Abstract

BACKGROUND AND OBJECTIVES:

Improper techniques in cerebrovascular end-to-side bypass, such as back-wall injury or skiving bites, can lead to stenosis or thrombosis. To address this challenge, we developed a needle tip quality-controlled (TQC) training protocol and evaluated its training value and clinical significance.

METHODS:

The TQC protocol mandates continuous visualization of the needle tip within the vessel lumen during each stitch, guided by strict suturing principles that prohibit intraluminal blind suturing. An attending neurosurgeon underwent training using the TQC protocol on a rat femoral vessel model before its clinical application in 26 bypass cases. Cumulative sum analysis was used to assess recipient clamp times during both the animal training and clinical surgeries. Intraoperative and postoperative bypass patency rates were also evaluated.

RESULTS:

In the 24 animal models, the mean recipient clamp time was 30.79 ± 6.42 minutes. Cumulative sum analysis revealed that proficiency required 16 models, after which clamp times significantly decreased to 27.37 ± 5.15 minutes (P = .013; mean difference 8.88 minutes, 95% CI, 2.18-15.57). No back-wall injuries or skiving bites were observed, and the delayed patency rate was 95.83%. In the 26 superficial temporal artery to middle cerebral artery bypass cases, the mean recipient clamp time was 26.65 ± 6.16 minutes, with the mastery phase achieved after 6 cases. The intraoperative and 3-month postoperative patency rates were 100% and 96.15%, respectively.

CONCLUSION:

The TQC protocol effectively prevents technical errors, ensuring high-quality anastomosis. Its high trainability and short learning curve establish it as a practical and valuable training tool for young vascular neurosurgeons.

ABBREVIATIONS:

CUSUM

cumulative sum

FA

femoral artery

FV

femoral vein

MMD

moyamoya disease

STA

superficial temporal artery

TQC

needle tip quality control.

The superficial temporal artery to middle cerebral artery (STA-MCA) end-to-side bypass is a widely used neurosurgical technique for managing complex cerebrovascular conditions such as moyamoya disease (MMD), complex aneurysms, and occlusive vascular disorders.^1-3 The success of the procedure is largely dependent on the precision of the anastomosis, in which surgical technique plays a critical role.

Various suturing techniques are used during STA-MCA bypass. Interrupted suturing involves placing individual stitches along the anastomotic site, which allows for precise control of suture tension.⁴ However, the small size of the anastomosis often necessitates the use of an intraluminal-blind suture for the final stitch in a suture line. During vessel occlusion, when the lumen is collapsed, this technique carries the risk of back-wall bites, potentially leading to anastomotic stenosis.⁵ In addition, the difference in wall thickness between the STA and MCA increases the likelihood of skiving bites, which can result in intraluminal thrombosis (Figure 1). Conversely, running suturing allows for continuous visualization of the vessel lumen, reducing the risk of back-wall and skiving bites. However, this approach presents challenges in achieving uniform tension control along the anastomosis, maintaining everted alignment of the vessels, and facilitating anastomotic expansion over time.⁶ Although several hybrid techniques^7-9 have been developed to address these issues to varying degrees, a standardized, universally applicable quality-controlled training protocol has yet to be established for young neurosurgeons at the early stages of their careers.

FIGURE 1.

Risks associated with intraluminal-blind sutures. This figure illustrates the risks involved with intraluminal-blind sutures during temporary vessel occlusion when the lumen collapses. A deep intraluminal-blind suture may result in a back-wall bite, while a shallow suture can lead to a skiving bite. MCA, middle cerebral artery; STA, superficial temporal artery.

This article introduces a needle tip quality-controlled (TQC) training protocol, which mandates the continuous visualization of the needle tip within the vessel lumen and a standardized sequence and technique for each stitch. We evaluated both the training efficacy of this protocol in an animal model and its translational value to clinical practice.

METHODS

The TQC Protocol

The primary objective of the TQC protocol is to ensure that the needle tip remains visible within the vessel lumen throughout each stitch. The following fundamental principles were strictly followed to achieve this objective:

1. A “watch dial” system was used to reference each stitch at the anastomotic stoma.

2. The suture sequence was carefully prescribed to maintain sufficient open space at the anastomotic site for each stitch, allowing the insertion of forceps to facilitate intraluminal spreading.

3. Designated suturing techniques—such as one-bite, two-bite, and running-to-interrupted sutures—were applied for each individual stitch.

4. Intraluminal-blind suturing was strictly prohibited.

The sequence and techniques employed are illustrated in Figure 2, using a 12-stitch example. Specifically, the 12 o'clock (heel) and 6 o'clock (toe) positions were sutured first as anchoring stitches. In the “wee hours,” the 1 and 5 o'clock positions were sutured first using the two-bite technique. This involved passing the needle through the recipient vessel wall under intraluminal spreading with a 0.2-mm elbow microforceps (Figure 3A), pulling the needle out, and then passing it through the donor vessel wall under extraluminal tenting (Figure 3B).

FIGURE 2.

The needle tip quality control protocol. Depiction of the stitch sequence and technique for the needle tip quality control protocol. The Arabic numerals represent watch dial references, black knots indicate anchoring stitches, green knots indicate two-bite sutures, brown knots signify one-bite sutures, and blue knots represent running-to-interrupted sutures.

FIGURE 3.

Illustration of the two-bite suture and the running-to-interrupted suture. A, The first bite involves passing the needle through the recipient/donor vessel wall under intraluminal spreading, followed by pulling the needle out. B, The second bite passes the needle through the donor/recipient wall under extraluminal tenting, ensuring full visibility of the needle tip. A 0.2-mm elbow microforceps, with its upturned tips, is preferred for optimal intraluminal spreading. The running-to-interrupted suture technique is used during the last 2 stitches to avoid intraluminal-blind suturing for the final stitch. C, Intraluminal spreading and D, extraluminal tenting are used to maintain needle tip visibility during the 2 running stitches. The suture is then divided into 2 interrupted stitches and secured with 2 knots. This technique ensures sufficient space for intraluminal spreading during the final stitch.

The 2 o'clock position was sutured using the one-bite technique, where the needle passes through both the recipient and donor walls in one motion without pulling out midway. Intraluminal spreading and extraluminal tenting were still applied to ensure full visibility of the needle tip. The 3 and 4 o'clock positions, the final 2 stitches in the “wee hours”, were completed using the running-to-interrupted technique. This involved cutting the thread of the 2 running sutures in the middle to create 2 interrupted sutures, which were then tied with 2 knots. Intraluminal spreading (Figure 3C) and extraluminal tenting (Figure 3D) were used to maintain full trajectory visibility of the needle tip. The stitch sequence and technique applied in the “forenoon hours” mirrored those used in the “wee hours”. In practice, the number of stitches can range from 12 to 16, depending on the length of the anastomosis. However, the same basic principles were consistently followed.

Laboratory Training

Twelve male Sprague Dawley rats, aged 3 to 5 months and weighing 300 to 400 g, were used for the training. The method for establishing rat femoral vessel models is described in Supplemental Digital Content 1, Supplementary Data 1, https://links.lww.com/NS9/A132. The femoral artery (FA) was designated as the donor vessel, and the femoral vein (FV) as the recipient. A vessel clamp (Aesculap, B. Braun Melsungen AG) was applied to the proximal FA, and the distal FA was ligated and transected, followed by intraluminal flushing of the artery using a needle. The adventitia of the vessel was then carefully prepared with blunt and sharp dissection. A fish-mouth arteriotomy was made at the end of the FA to prepare it as the donor vessel.

Two vessel clamps were applied to the FV to block blood flow, and a linear venotomy was made on the FV to serve as the recipient site. The end-to-side anastomosis was performed with 10-0 thread (Ningbo Medical Needle Factory), strictly adhering to the TQC protocol (Figure 4). Once the anastomosis was complete, the clamps were removed sequentially from the distal FV, proximal FV, and FA. The suture line was compressed using the prepared pedicled fat pad for 2 minutes to achieve hemostasis. Additional stitches were applied without cross-clamping if any blood leakage was observed. Immediate patency was assessed by observing dilation and pulsations transmitted across the anastomosis. The color change and pulsations in the FV were used as direct indicators of blood flow restoration. The detailed procedure is shown in Video 1.

FIGURE 4.

Training using the needle tip quality control protocol in rat femoral vessels. This figure demonstrates the needle tip quality control protocol training in rat femoral vessels. The two-bite technique was used at the A, 1 o'clock and B, 5 o'clock positions, while the one-bite technique was applied at 2 o'clock with C, intraluminal spreading and D, extraluminal tenting. E, The running-to-interrupted technique was used at 3 and 4 o'clock. F, Intraluminal flushing was performed at 8 and 9 o'clock before sealing the anastomosis. G, The color change and pulsation of the FV confirmed immediate patency. Red Arabic numerals denote watch dial references. FA, femoral artery; FV, femoral vein; MA, severed Murphy's branch of FA; MV, severed Murphy's branch of FV; N, irrigation needle.

Postoperative care involved administering antibiotics, pain relief medications, and regular wound dressing changes. After a minimum of 14 days, the wound was re-explored under general anesthesia. Acland's test was performed on the FV, with refilling of the vessel indicating delayed patency of the anastomosis. After testing, the rats were euthanized using an overdose of isoflurane (IsoFlo; Zoetis). All training procedures were performed by the corresponding author. Before initiating this training protocol, the operating surgeon, an attending neurosurgeon, had independently performed 20 STA-MCA bypass procedures and had assisted in approximately 15 additional bypass procedures.

Clinical Application

After the laboratory training, the corresponding author performed 26 consecutive STA-MCA end-to-side bypass surgeries using the TQC protocol between January 2024 and December 2024. Patient demographics, imaging findings, and bypass patency were retrospectively reviewed. The patient selection process is summarized in a flowchart (Figure 5).

FIGURE 5.

Patient flowchart. Flow diagram of patient selection and follow-up for the 26 consecutive STA-MCA end-to-side bypass cases performed with the TQC protocol between January 2024 and December 2024. All patients completed the 3-month CTA/DSA follow-up and were included in the analysis. CTA, computed tomography angiography; DSA, digital subtraction angiography; EDS, encephalodurosynangiosis; EMS, encephalomyosynangiosis; ICA, internal carotid artery; ICG, indocyanine green; MCA, middle cerebral artery; MMD, moyamoya disease; STA, superficial temporal artery; TQC, needle tip quality control.

The STA was exposed and prepared in fish-mouth fashion. A linear arteriotomy was made on the selected recipient MCA-M4. The end-to-side anastomosis was performed using the previously described TQC protocol under high magnification with a surgical microscope (Leica Microsystems) (Figure 6). The same sutures and surgical instruments used during the laboratory training were employed during the clinical procedures. Intraoperative bypass patency was confirmed using indocyanine green angiography. The detailed procedure is shown in Video 2. In all cases, indirect revascularization techniques, including encephalodurosynangiosis and encephalomyosynangiosis, were also performed. Bypass patency was evaluated at 3 months postoperatively using computed tomography angiography (CTA) or digital subtraction angiography (DSA).

FIGURE 6.

Clinical application of the needle tip quality control protocol. The two-bite technique was used at 1 o'clock with A, intraluminal spreading and B, extraluminal tenting. C, The running-to-interrupted technique was used at 3 and 4 o'clock. D, Intraluminal flushing was performed at 8 and 9 o'clock before the anastomosis was sealed. Arabic numerals refer to watch dial references.

Data Collection and Statistics

Time-related data and stitch counts during training and clinical practice were gathered by reviewing recorded footage. Back-wall and skiving bites were inspected by observing the suture line within the vessel lumen after completing half of the anastomosis.

Statistical analysis was performed using SPSS 22.0 (IBM Corp.), with continuous variables expressed as mean ± SD and categorical variables as percentages. Group comparisons were done using the t-test for continuous variables and Fisher's exact test for categorical ones, with a significance level of P <.05. Cumulative sum (CUSUM) learning curves were created using Python 3.6 (Python Software Foundation) with pandas, numpy, and matplotlib libraries. The mean recipient clamp time served as the baseline, and deviations from this mean were tracked over time to generate the learning curve, visualized using matplotlib. Institutional ethics committee approval was obtained for this study, and all animal procedures were performed in accordance with institutional guidelines for the care and use of laboratory animals.

RESULTS

Animal Training

The mean recipient clamp time was 30.79 ± 6.42 minutes, and the mean suturing time was 23.63 ± 5.8 minutes. Intraoperative inspection revealed no occurrences of back-wall or skiving bites. The immediate and delayed bypass patency rates were 100% (24/24) and 95.83% (23/24), respectively. Logarithmic curve analysis demonstrated a significant learning curve for recipient clamp time (P = .004; slope −4.47 minutes per log unit, 95% CI, −7.35 to −1.59) (Figure 7A). CUSUM analysis of recipient clamp time identified 3 distinct phases: initial learning phase (models 1-8), intermediate phase (models 9-16), and mastery phase (models 17-24) (Figure 7B). Detailed interphase comparisons are presented in Table 1. No mortality occurred during the 14-day follow-up period.

FIGURE 7.

Learning curve and CUSUM analysis for recipient clamp time. A, Logarithmic curve analysis revealed a significant learning curve (P = .004; slope −4.47 minutes per log unit, 95% CI, −7.35 to −1.59). B, CUSUM analysis identified 3 distinct phases: the initial learning phase (models 1-8), the intermediate phase (models 9-16), and the mastery phase (models 17-24). CUSUM, cumulative sum.

TABLE 1.

Interphase Comparisons of Characteristics in Needle Tip Quality Control Animal Training

Variable	Phase 1 (N = 8)	Phase 2 (N = 8)	Phase 3 (N = 8)	P (overall)	P1 (1 vs 2)	P2 (1 vs 3)	P3 (2 vs 3)
Recipient clamp time, min	36.25 ± 7.17	28.75 ± 3.37	27.37 ± 5.15	0.008	0.018 (1.49 to 13.51)	0.013 (2.18 to 15.57)	0.538 (−3.29 to 6.04)
Suturing time, min	29.13 ± 5.67	21.63 ± 3.89	20.13 ± 3.87	0.002	0.008 (2.29 to 12.71)	0.002 (3.80 to 14.20)	0.452 (−2.66 to 5.66)
No. of sutures	12.75 ± 1.28	12.75 ± 1.28	12.25 ± 0.71	0.67	1.0 (−1.60 to 1.60)	0.43 (−0.75 to 1.75)	0.43 (−0.75 to 1.75)
Time per suture, min	2.29 ± 0.38	1.70 ± 0.21	1.65 ± 0.33	0.0008	0.0027 (0.26 to 0.92)	0.0031 (0.25 to 1.02)	0.73 (−0.25 to 0.35)
Back-wall bite, n (%)	0 (0)	0 (0)	0 (0)	—	—	—	—
Skiving bite, n (%)	0 (0)	0 (0)	0 (0)	—	—	—	—
Immediate patency, n (%)	8 (100)	8 (100)	8 (100)	—	—	—	—
Delayed patency, n (%)	7 (87.5)	8 (100)	8 (100)	0.352	1.0	1.0	1.0

Data are presented as mean ± SD or n (%). P, overall comparison across the 3 phases; P1, phase 1 vs phase 2; P2, phase 1 vs phase 3; P3, phase 2 vs phase 3. Continuous variables were compared using the t-test and categorical variables using Fisher's exact test. Values in parentheses following P1, P2, and P3 are 95% CIs for the mean difference between the corresponding phases; CIs are reported for continuous variables only.

Clinical Practice

The mean MCA clamp time was 26.65 ± 6.16 minutes, and the mean suturing time was 20.96 ± 4.46 minutes. No back-wall or skiving bites were observed during intraoperative inspection. The intraoperative and postoperative 3-month bypass patency rates were 100% (26/26) and 96.15% (25/26), respectively. Logarithmic curve analysis revealed a significant learning curve for MCA clamp time (P = .0009; slope −4.58 minutes per log unit, 95% CI, −7.08 to −2.08) (Figure 8A). CUSUM analysis of MCA clamp time identified 2 phases: learning phase (cases 1-6) and mastery phase (cases 7-26) (Figure 8B). There were no statistically significant differences in demographic or baseline clinical characteristics between these 2 phases. Both MCA clamp time and suturing time were significantly reduced in the mastery phase compared with the learning phase. Detailed interphase comparisons are provided in Table 2. No new neurological deficits or patient deaths were observed during the 3-month follow-up period.

FIGURE 8.

Learning curve and CUSUM analysis for MCA clamp time. A, Logarithmic curve analysis showed a significant learning curve (P = .0009; slope −4.58 minutes per log unit, 95% CI, −7.08 to −2.08). B, CUSUM analysis identified 2 phases: the learning phase (cases 1-6) and the mastery phase (cases 7-26). CUSUM, cumulative sum; MCA, middle cerebral artery.

TABLE 2.

Interphase Comparisons of Characteristics in Needle Tip Quality Control Clinical Practice

Variable	Learning phase (N = 6)	Mastery phase (N = 20)	P value
Age, y	54.83 ± 12.21	52.35 ± 11.50	.651 (−8.71 to 13.67)
Male sex, n (%)	3 (50)	14 (70)	.628
ICA/MCA occlusion, n (%)	3 (50)	5 (25)	.330
Ischemic MMD, n (%)	3 (50)	11 (55)	1.0
Suzuki stage III, n	2	7	1.0
Suzuki stage IV, n	1	3	1.0
Suzuki stage V, n	0	1	—
Hemorrhagic MMD, n (%)	0 (0)	3 (15)	—
MCA complex aneurysm, n (%)	0 (0)	1 (5)	—
Comorbidities
Smoking, n (%)	3 (50)	12 (60)	1.0
Diabetes, n (%)	2 (33.33)	9 (45)	1.0
Hypertension, n (%)	5 (83.33)	13 (65)	.628
Surgical side (L/R), n	2/4	7/13	1.0
MCA temporary occlusion time, min	34.33 ± 5.50	24.35 ± 4.16	.0077 (3.67 to 16.30)
Suturing time, min	26.17 ± 3.67	19.4 ± 3.35	.00044 (3.34 to 10.20)
No. of sutures	12.67 ± 0.94	12.6 ± 1.11	.899 (−1.01 to 1.14)
Time per suture, min	2.07 ± 0.26	1.54 ± 0.21	<.0001 (.31 to .75)
Back-wall bite, n (%)	0 (0)	0 (0)	—
Skiving bite, n (%)	0 (0)	0 (0)	—
Intraoperative ICG patency, n (%)	6 (100)	20 (100)	—
3-mo CTA/DSA patency, n (%)	6 (100)	19 (95)	1.0

CTA, computed tomography angiography; DSA, digital subtraction angiography; ICA, internal carotid artery; ICG, indocyanine green; L, left; MCA, middle cerebral artery; MMD, moyamoya disease; R, right.

Data are presented as mean ± SD or n (%). Continuous variables were compared using the t-test and categorical variables using Fisher's exact test. Values in parentheses following P values are 95% CIs for the mean difference between phases; CIs are reported for continuous variables only.

DISCUSSION

Key Results

Training with the TQC protocol was associated with a progressive shortening of recipient clamp time in both the laboratory and the clinical setting. In 24 rat femoral vessel anastomoses, no back-wall or skiving bites occurred, the delayed patency rate was 95.83%, and proficiency was achieved after 16 models, with the mean recipient clamp time decreasing from 36.25 ± 7.17 to 27.37 ± 5.15 minutes across phases. In 26 clinical STA-MCA bypasses, the intraoperative patency rate was 100% and the 3-month patency rate was 96.15%; mastery was reached after 6 cases, with MCA clamp times remaining well below the 30-minute benchmark proposed by the Carotid and Middle Cerebral Artery Occlusion Surgery Study trial.²

Limitations

First, this study focused primarily on technical training aspects and short-term patency, without evaluating long-term clinical outcomes. Second, the CUSUM analysis was based on a small sample from a single surgeon; individual variability among trainees was not explored, and the learning curves may not be directly replicable by surgeons with different prior experience. This single-operator design may bias the learning curve toward faster acquisition, and the magnitude of this bias cannot be quantified from the present data. Third, the study did not directly compare the TQC protocol with running or other interrupted techniques, making it difficult to determine whether the TQC protocol provides superior training benefits or clinical outcomes compared with established methods. Finally, the clinical series was retrospective and conducted at a single center, which introduces potential selection bias.

Interpretation

These results are clinically relevant because the value of STA-MCA bypass depends on anastomotic quality and speed. The STA-MCA bypass reduces ischemic events in ischemic MMD¹⁰ and lowers the 5-year rebleeding rate from 31.6% to 11.9% in hemorrhagic MMD.¹ Although its efficacy for arterial occlusion has been debated,^11-13 the Carotid and Middle Cerebral Artery Occlusion Surgery Study trial demonstrated a significantly lower incidence of ipsilateral ischemic stroke with bypass plus medication than with medication alone² and emphasized that optimal outcomes require surgeons to perform at least 15 bypass surgeries annually, with an anastomosis patency rate greater than 95% and an MCA clamp time not exceeding 30 minutes. Skilled and rapid anastomosis is therefore central to achieving these benchmarks.

The single-barrel end-to-side anastomosis remains the most commonly used configuration in STA-MCA bypass,^3,14,15 and every suturing technique involves a trade-off between anastomosis quality and occlusion time. Interrupted suturing allows stitch-by-stitch control of tension and placement and accommodates the caliber and wall-thickness mismatch between the STA and MCA, but requires a longer occlusion time, and its final stitch is often an intraluminal-blind suture that risks back-wall or skiving bites (Figure 1).^4,5 Running suturing shortens clamp time and keeps the lumen in view,¹⁶ and it may be argued that continuous needle tip visualization alone already solves the problem that the TQC protocol targets. However, the running technique has inherent drawbacks that are magnified in the training setting. Tension is distributed along an entire continuous loop rather than set stitch by stitch: overtightening produces a purse-string effect that narrows the anastomosis, whereas slack loops leak. Individual stitches cannot be repositioned to compensate for vessel size mismatch. The fish-mouth donor opening, naturally a three-dimensional structure, is flattened into a two-dimensional line, which limits outward expansion of the anastomosis over time, and intima-to-intima eversion is difficult to maintain.⁶ Finally, tightening a continuous loop against a fixed, thin-walled recipient artery can itself tear the wall. We therefore consider uninterrupted visualization without stitch-level control to be an incomplete solution, particularly for trainees.

The TQC protocol is based on interrupted suturing, with modifications to the suturing sequence and to the final 2 stitches so that intraluminal-blind suturing is eliminated while stitch-level control is preserved. Sufficient open space is created for every stitch, allowing microforceps to keep needle entry and exit fully visible. The two-bite technique is prioritized at the 1 and 5 o'clock positions—closest to the back wall and most prone to back-wall bites—while the anastomotic site is most open, and ensures eversion and alignment. The one-bite suture at 2 o'clock saves time, and the running-to-interrupted (double-throw) technique at the 3 and 4 o'clock positions keeps the needle tip visible during the final stitches without the knot-tying difficulty of cutting many loops along an entire suture line.^7,8 Other techniques reported to enhance intraluminal visibility, such as the half-tied stay suture technique¹⁷ and the toe-first technique,⁹ have been described only in case reports, with no specific data on recipient clamp time available.

Regarding the suturing order, a reasonable concern is that passing the needle through the fixed recipient artery first may increase the risk of vessel wall tearing (“cheese-wiring”), and many microsurgeons conventionally begin from the donor vessel because a donor tear can be trimmed and repaired without compromising the recipient artery. The TQC protocol does not dogmatically fix the suturing order: with the donor introduced from the left side, stitches on the 12 o'clock side are placed recipient-first and those on the 6 o'clock side donor-first, following the most ergonomic sequence for a right-handed surgeon. More importantly, protection against wall tearing relies on needle handling—intraluminal spreading that supports the wall from within, extraluminal tenting, and controlled entry and exit angles with continuous needle tip visualization—rather than on the suturing order. Consistent with this, no wall tears or pullout errors occurred in any of the 24 animal or 26 clinical anastomoses, although the recipient wall (FV or M4) was thinner and more fragile than the donor wall.

Among the available training models—synthetic tubes, chicken wing arteries, human placenta, cadaveric specimens, and live animals¹⁸—the live rat model best reproduces real-time hemodynamic conditions. Rat common carotid arteries,¹⁹ aorta, and iliac arteries^20,21 have all been reported as effective training models, but we prefer rat femoral vessels for STA-MCA bypass training.²² The parallel arrangement of the FA and vein facilitates end-to-side anastomosis; the FV approximates the diameter of the human MCA-M4; and the thicker-walled FA mimics the STA relative to the M4. The smaller surgical field and the fragile venous wall, prone to pullout errors, make this model more demanding than actual surgery—explaining the longer clamp time during training than in clinical cases (30.79 ± 6.42 vs 26.65 ± 6.16 minutes)—and increase its training value.

Generalizability

Several features support the external validity of these results. The protocol is fully standardized—the watch dial reference, the stitch sequence, and the designated technique for each stitch can be taught and reproduced verbatim—and the same sutures and instruments were used in the laboratory and the operating room, which facilitated direct transfer of the trained skills. The clinical outcomes met international benchmarks (patency rate >95%, MCA clamp time <30 minutes)² in a real-world cohort with heterogeneous indications, including MMD, arterial occlusion, and a complex aneurysm. Nevertheless, the learning curves reported here were obtained by a single attending neurosurgeon with prior bypass experience. Trainees with different baseline experience may require more or fewer repetitions to reach mastery, and validation in multiple trainees and centers is warranted before the 16-model and 6-case thresholds can be generalized. Training of additional surgeons with this protocol is under way at our institution.

CONCLUSION

The TQC protocol effectively prevents technical errors, such as back-wall and skiving bites, ensuring high-quality anastomosis. Its high trainability using rat femoral vessel models and the short learning curve required to achieve MCA clamp times under 30 minutes make it a practical and reliable training tool for young bypass neurosurgeons.

Supplementary Material

neuopen-7-e000307-s001.docx ^{(16.2KB, docx)}

Funding

This study did not receive any funding or financial support.

Disclosures

The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

VIDEO 1. Training using the TQC protocol in rat femoral vessels: end-to-side anastomosis of the femoral artery to the femoral vein with continuous intraluminal needle tip visualization. Playback speed, ×2.

VIDEO 2. Clinical application of the TQC protocol in STA-MCA end-to-side bypass, demonstrating the prescribed stitch sequence and suturing techniques. Playback speed, ×2.

Supplemental Digital Content

Supplemental Digital Content 1: Supplementary Data 1. Establishment of rat femoral vessel models. The following section provides a detailed description of the method used to establish rat femoral vessel models.