Continuous Through-the-lumen Microvascular Anastomosis: A Retrospective Review of a Modified Technique

Abstract

Background:

The debate between continuous and interrupted sutures for microvascular anastomosis has long persisted, with broader acceptance of the interrupted technique. Although studies show comparable outcomes, continuous suturing remains underused due to concerns of technical complexity, anastomotic constriction, and patency loss. We present a simplified and effective continuous technique that addresses these concerns.

Methods:

This 5-year retrospective study included all elective free tissue transfers performed using the described continuous suture technique. Trauma-related replantation and revascularization cases were excluded. Patient records were reviewed for demographics, flap types, anastomosis configuration and timing, reexplorations, complications, and outcomes.

Results:

The technique was performed in 785 patients, encompassing 2346 microvascular anastomoses (794 arterial and 1552 venous). End-to-end anastomoses were done in 633 arteries and 867 veins, and end-to-side anastomoses in 161 arteries and 685 veins. Flap types included anterolateral thigh (n = 384), radial forearm (n = 220), fibula (n = 145), latissimus dorsi (n = 29), deep inferior epigastric artery (n = 2), ulnar forearm (n = 3), and toe transfers (n = 2). Mean arterial and venous anastomosis times were 7.5 and 10 minutes, respectively. All anastomoses achieved 100% immediate patency. There were 41 reexplorations, mostly for venous issues, with 28 flap failures. The overall flap success rate was 96.43%.

Conclusions:

This modified continuous technique enables posterior wall repair through the vessel lumen without flipping, minimizing manipulation and reducing operative time. It offers a reproducible, efficient approach for both arterial and venous anastomoses.

Takeaways

Question: How can microvascular anastomosis be performed more efficiently without compromising precision or patency?

Findings: This study evaluated 785 patients undergoing microvascular procedures with a modified technique. It demonstrated 100% immediate patency with an average arterial repair time of 7.5 minutes and venous repair time of 10 minutes, achieving a 96.43% success rate across various flap and replantation types.

Meaning: The continuous through-the-lumen microvascular anastomosis technique offers a simple and effective solution for arterial and venous repairs, ensuring precision and excellent patency outcomes.

INTRODUCTION

Microvascular anastomosis, described as anastomosis of any vessel less than 3 mm in diameter with optimal magnification, is an integral part of various surgical procedures, including free tissue transfer, revascularization, replantation, and repair of traumatic vascular injuries of small vessels.¹ Several techniques including interrupted sutures,² laser,³ fibrin glue,⁴ continuous sutures,⁵ triangulation method, one-way-up technique,⁶ open guide suture technique,⁷ photochemical tissue bonding technique,⁸ and coupling devices have been described.

Although the mechanical aids and nonsuture techniques have been described with a prospect of simplifying the surgical procedure, in practice, they take more time in setting up the system than actual surgical time. Advancements in magnification, suture quality, and widespread teaching and exposure have made the suture repair the time-tested and most effective technique for microvascular anastomosis.⁹ Various studies have been performed to compare the different suture techniques with variable results. Continuous sutures have been shown to reduce the anastomosis time in previous studies,^10,11 with patency and stenosis rates comparable to the interrupted sutures,^12–14 but have not been widely accepted as the preferred method by surgeons. Concerns include constriction of the anastomotic site, reduced systolic distension, and intraluminal suture material promoting thrombosis.^15,16 In another study, continuous sutures were believed to be time efficient but with 45% reduction in blood flow across the anastomotic site pertaining to purse string effect.¹⁷

Apart from the repair technique, the operating setup, instruments and clamps, surgeon’s skills, and careful selection of recipient vessels are paramount to good anastomotic outcome.¹⁸ Many modifications have been described to overcome the concerns of the continuous suture technique^{7,13,14,19,20} but none has been adopted in practice widely due to complexity involved with the technique and because most of these modifications have been performed only in animal studies.^12–14

In this study, we have described a modified continuous suture microvascular anastomosis that provides the following advantages: (1) it reduces the anastomotic time; (2) it does not require flipping of the vessel for posterior wall repair, making it technically easier; (3) the anastomosis can be easily performed with a single suture; (4) it overcomes the problem of purse stringing of the vessel wall; (5) it addresses the problem of anastomotic leakage concerns associated with continuous repair due to loosening; (6) the technique allows posterior wall repair under vision, through the lumen, minimizing errors; and (7) it is a simplified technique without the need for additional instruments or equipment and is equally good in a resource-restrained setup. The goal of this article was not comparative analysis but to describe this novel method and share outcomes from its application in elective free tissue transfers during a 5-year period.

MATERIALS AND METHODS

To systematically evaluate the proposed technique, we conducted a retrospective review during a 5-year period as detailed in the following. This study was approved by the institutional ethical review board and conducted in the department of plastic and reconstructive surgery at a tertiary care hospital. All elective free tissue transfers using the modified continuous technique from November 2017 to October 2022, performed by a single surgeon under microscopy and general anesthesia, were included. To reduce heterogeneity and maintain dataset uniformity, procedures involving trauma-related replantation or revascularization were excluded; only elective free tissue transfers for head and neck, upper and lower limb, chest, abdomen, and breast reconstruction were included. This modified technique replaced the surgeon’s previous practice of simple interrupted sutures for microvascular anastomosis. Data were collected from operative and inpatient records, including demographic details, flap type, type and configuration of anastomosis, duration of anastomosis, need for reexploration, complications, and flap outcomes.

Surgical Technique

The modified continuous suture technique was standardized across all included cases (arterial and venous, end to end, and end to side) as follows. Vessels were prepared for the anastomosis by stripping the vessel margin adventitia for clear visualization of lumen and suture placement. The vessel's lumen was washed with heparin saline (5000-units heparin in 100 mL saline). For end-to-end anastomosis, the ends of vessels were placed in the double Acland clamp. The microscope and surgeon position were adjusted according to the requirements of the anastomotic area. We have used a single suture of prolene or nylon of sizes 8-0, 9-0, 10-0, and 11-0, depending on the size of the vessels. The first stitch was made with the introduction of a microneedle at one end of the vessel, 12 o’clock position, from outside to inside, passing through the lumen and then passing through the wall of the opposite-end vessel inside to outside (Fig. 1). The knot was tied, with one end of suture knot left short and the other long end kept attached to the needle. The vessel ends ware kept under moderate tension in the clamp to have the posterior wall in view. The needle was passed at the back of the vessel to suture the posterior wall (Fig. 2). Then, without flipping the vessel, the needle was passed outside in through one end of the vessel (Fig. 3), bringing the needle into the lumen to do the whole posterior wall repair with easy maneuvering of the needle. (See figure, Supplemental Digital Content 1, which shows how the needle is passed in the lumen, https://links.lww.com/PRSGO/E340.) The posterior wall repair started with passing the needle inside out from the opposite end and then back to the lumen by traveling from outside in through the other end (Fig. 4). The same continuous suture loops were taken throughout the posterior wall till the 6 o’clock position (Fig. 5). At that point, the suture was pulled to tighten the loops, and a knot was placed with the loop of the continuous suture (Fig. 6). (See figure, Supplemental Digital Content 2, which displays the suture pulled to tighten posterior wall repair, https://links.lww.com/PRSGO/E341.) The loop was left uncut, and the same suture was continued for repair of the anterior wall. (See figure, Supplemental Digital Content 3, which displays completed repair of the posterior wall with a knot at 6 o’clock; the suture was not cut, https://links.lww.com/PRSGO/E342.) The needle was introduced from outside in through one end of the vessel and brought back inside out through the other end (Fig. 7). The anterior wall was repaired with continuous running sutures until it reached the first knot placed at the 12 o’clock position. (See Supplemental Digital Content 4, which displays the anterior wall repaired, https://links.lww.com/PRSGO/E343.) The suture was pulled to tighten the anterior wall repair (Fig. 8). Before tying the knot, the clamp was released to allow filling of the vessel and to check any leak from anastomosis. (See Supplemental Digital Content 5, which displays clamps released to allow the vessel to fill to check any leakage, https://links.lww.com/PRSGO/E344.) Once checked and found satisfactory, the final knot was tied with the short end of the first suture at the 12 o’clock position (Figs. 9, 10). The patency of anastomosis was checked with the Acland empty–refill test and the perfusion of the finger/flap. (See Video [online], which displays the step-by-step demonstration of the modified microvascular anastomosis technique.)

Fig. 1.

First suture at 12 o’clock position. A, Operative photograph. B, Schematic representation.

Fig. 2.

Needle is passed to the posterior aspect. A, Operative photograph. B, Schematic representation.

Fig. 3.

Posterior wall repair first bite from outside to inside. A, Operative photograph. B, Schematic representation.

Fig. 4.

Needle is passed inside out through the posterior wall. A, Operative photograph. B, Schematic representation.

Fig. 5.

Posterior wall is repaired. A, Operative photograph. B, Schematic representation.

Fig. 6.

Making 6 o’clock suture knot. A, Operative photograph. B, Schematic representation.

Fig. 7.

Repair of the anterior wall started with passing the needle outside in and then inside out. A, Operative photograph. B, Schematic representation.

Fig. 8.

Suture ends are pulled to tighten the repair of the anterior wall. A, Operative photograph. B, Schematic representation.

Fig. 9.

Knot is tied at 12 o’clock using the first suture as short end. A, Operative photograph. B, Schematic representation.

Fig. 10.

Completed vessel repair. A, Operative photograph. B, Schematic representation.

Video 1. This video demonstrates a modified continuous through-the-lumen microvascular anastomosis technique used in elective free tissue transfer. The approach enables posterior wall repair without flipping the vessel, utilizing a single continuous suture through the vessel lumen for both arterial and venous anastomoses. Key steps are shown in real-time under high magnification, highlighting improved visualization, minimal manipulation, and efficient suture transitions. The technique reduces operative time while maintaining immediate patency and vessel integrity.

Download video file ^{(56.1MB, mp4)}

RESULTS

The modified continuous suture technique was performed in 785 patients, with a total of 794 arterial anastomoses (including 6 turbo-charging and 3 flow-through procedures) and 1552 venous anastomoses. In 18 cases, venae comitantes were fused, resulting in a single venous anastomosis. This yielded a total of 2346 microvascular anastomoses. The patient cohort included 508 men and 277 women, ranging in age from 18 months to 72 years. (See table, Supplemental Digital Content 6, which displays the overall study summary, https://links.lww.com/PRSGO/E345.)

End-to-end anastomoses were performed in 633 arteries and 867 veins, whereas end-to-side anastomoses were performed in 161 arteries and 685 veins. The types of flaps reconstructed included anterolateral thigh flap (n = 384), radial forearm free flap (n = 220), free fibula flap (n = 145), latissimus dorsi flap (n = 29), deep inferior epigastric artery flap (n = 2), ulnar forearm free flap (n = 3), and toe transfer (n = 2). In all cases, free tissue transfer was performed with 1 arterial and typically 2 venous anastomoses, except where only 1 vein was available due to venae comitantes fusion.

The arterial anastomosis time ranged from 4 to 13 minutes, with an average of 7.5 minutes, whereas the venous anastomosis time ranged from 7 to 15 minutes, with an average of 10 minutes. These values reflect the available subset of recorded cases, as complete timing data were not consistently documented across all 2346 anastomoses due to retrospective limitations. All anastomoses demonstrated 100% immediate patency intraoperatively, with restoration of perfusion and good arterial pulsation and venous flow.

A total of 41 reexplorations (5.2% of flaps) were required, all due to venous compromise or perianastomotic hematoma. In several cases, clear intraoperative distinction between intraluminal thrombosis and extrinsic compression from hematoma was not reliably documented. However, both conditions presented with venous congestion and were managed with reexploration, confirming compromised outflow. When evident, hematoma was evacuated and hemostasis was secured; where thrombus was identified, reanastomosis was performed. In all reexplored cases requiring revision, the anastomosis was revised using the same modified continuous technique.

Of the 41 reexplorations, 28 flaps ultimately failed, including 8 anterolateral thigh flaps, 3 radial forearm free flaps, and 17 free fibula flaps. Notably, there were no failures in latissimus dorsi, deep inferior epigastric artery flaps, ulnar forearm, or toe transfer flaps. (See figure, Supplemental Digital Content 7, which displays bar diagram of flap type versus total and failed flaps, https://links.lww.com/PRSGO/E346.) This results in a flap success rate of 96.43%, aligning closely with success rates reported in other large microsurgical series. (See figure, Supplemental Digital Content 8, which displays flap success rate, https://links.lww.com/PRSGO/E347.)

DISCUSSION

This study described a large series using a novel continuous suture modification for microvascular anastomosis. By repairing the posterior wall through the vessel lumen, our technique improves visualization and reduces unnecessary vessel handling, yielding a simpler, highly reproducible method across a range of free-flap reconstructions.

The most widely practiced and initially described technique for microvascular anastomosis is interrupted sutures.⁴ Despite its reliability, the technique has been criticized for its time-consuming nature. Since its introduction, several modifications have been proposed to expedite the process while achieving comparable results.^3,4,19–21 Continuous suturing, by design, offers fewer needle passes, reduced knot-tying, and potential time efficiency.⁵ However, its clinical application has remained limited due to concerns such as vessel constriction, reduced systolic distension, and increased intraluminal suture material that may theoretically predispose to thrombosis.^11,17 Devices such as couplers, laser welders, and fibrin glue can streamline the process,²² but high cost, limited availability, and steep learning curves—especially in resource-poor settings—have kept them from being widely used.²³

In an animal model, Hudson et al¹⁴ showed a modified continuous venous anastomosis cut time from 17.7 to 9.8 minutes without affecting patency at 1 week or 1 month. Our results mirror this: mean arterial and venous anastomosis times were 7.5 and 10 minutes, respectively, with 100% immediate patency confirmed intraoperatively. Although we did not conduct a formal comparison with interrupted sutures due to the retrospective nature of the study, these times are notably shorter than many historical averages reported for interrupted techniques.¹⁷

Further support came from Lee et al,²⁴ who demonstrated 100% patency with continuous sutures and a complication rate comparable to interrupted sutures. Similarly, a systematic review by Alghoul et al²⁵ found that outcomes across continuous, interrupted, sleeve, and locking techniques are largely comparable, emphasizing that surgeon skill and adherence to microsurgical principles are the primary determinants of success.⁶ Our flap success rate of 96.43% aligns with major clinical series, such as 97.6% survival rate of Suh et al²⁶ during 30 years of head and neck reconstructions and 94.5%–96.9% success rate of Chen et al²⁷ in 1791 free flap reconstructions.

Our key modification—performing posterior wall repair through the vessel lumen without flipping—addresses technical challenges often associated with continuous suturing. After completing the posterior wall, we tied a loop knot without dividing the suture and seamlessly continued with anterior wall repair. This approach reduced vessel manipulation, optimized lumen visualization, and ensured a smooth, continuous suture transition.

By simplifying the process without the need for specialized instruments, our technique offers several additional advantages. Posterior wall repair is performed under direct vision, a single continuous suture is used, intraluminal clutter is minimized, and consistent suture tension is maintained. Vessel flipping and excessive handling are avoided, resulting in an atraumatic anastomosis. Overall, this modification creates a streamlined, reproducible, and efficient method suitable for both high-volume microsurgical practice and resource-limited environments.

Timmons²⁸ proposed a related technique for end-to-side anastomosis, in which a knot was tied at the midpoint before proceeding with anterior wall repair. In contrast, our method preserves suture continuity throughout the procedure. Rather than dividing the suture at the 6 o’clock position, we tied a loop knot, minimizing unnecessary manipulation around the vessel. Additionally, before securing the final knot at the 12 o’clock position, we released the clamp to allow the vessel to fill with blood, enabling fine adjustment of wall tension by maneuvering the suture. This simple step avoids overtightening or leakage, ensuring a precise, tension-free closure tailored to each vessel. Importantly, our technique is equally effective for both arterial and venous repairs, whereas previous continuous suturing methods were primarily limited to arterial anastomoses.^5,13,28

The clinical implications of our findings are significant. By reducing anastomosis time and avoiding advanced instruments, this technique improves operating room efficiency, expands training usage, and increases accessibility in varied practice environments. Its straightforward steps and minimal instrumentation also make it ideal for microsurgical training programs.

We acknowledge the limitations of our study. The retrospective design and absence of a direct comparator group limit our ability to definitively quantify superiority over other methods. Flow rate measurements were not conducted; however, perfusion and patency were confirmed intraoperatively in all cases. Owing to the retrospective nature and inconsistent retrospective site–specific documentation, stratification by anatomical reconstruction site was not feasible and is planned for future prospective evaluations. Additionally, replantation and revascularization cases were excluded from the analysis to reduce heterogeneity and ensure uniformity, given their different technical demands and higher risk of complications due to trauma-related vessel conditions.

Although all reexplorations were prompted by venous compromise, in some instances it was challenging to clearly delineate between intrinsic anastomotic thrombosis and extrinsic hematoma–induced compression. This highlights a limitation in retrospective operative documentation and underscores the need for prospective studies with detailed intraoperative recording. Nonetheless, the consistency of outcomes across a large elective cohort supports the feasibility, safety, and efficiency of this technique.

CONCLUSIONS

Continuous through-the-lumen microvascular anastomosis offers a reliable and practical alternative to conventional methods, with advantages in visualization, simplicity, and operative efficiency. Its applicability to both arterial and venous repairs makes it a versatile option, especially in training environments. Future comparative and hemodynamic studies are recommended to further evaluate its benefits.

DISCLOSURE

The authors have no financial interest to declare in relation to the content of this article.