Abstract
Background
The key role played by anastomosis determines the outcome of any free flap surgery. Besides many methods, the application of LASERS for performing microvascular anastomosis gaining popularity in recent times. The ease of application, utilizing lesser time for performing anastomosis than the conventional methods and minimal injury to the vessel layers, are contributing factors to the success of free flap surgery. Laser-assisted vascular anastomosis (LAVA) fulfills the criteria of lesser vessel wall damage and faster anastomosis and thus resulting in reduced flap ischemic time and overall outcome of the surgery.
Methods
A prospective randomized case–control trial comparing conventional suturing methods (group I) with Laser-assisted vascular anastomosis (group II) on free flaps were performed for the reconstruction of orofacial defects. The parameters assessed for evaluation were anastomotic time, ischemic time and vessel patency following anastomosis. Student’s t test and Fisher’s exact tests were implied for statistical analysis.
Results
The mean time taken for anastomosis was 19.75 min in the conventional group and 3.86 min in LAVA anastomosis. This difference was found to be extremely statistically significant (p < 0.00001). The mean ischemic time of the free flap harvested was 384.87 min in group I and 138.7 min in group II. This difference was also found to be extremely statistically significant (p < 0.00001).
Conclusion
The average anastomosis time for LAVA group was considerably reduced and total ischemic time was considerably less with successful uptake of the flap. In LAVA group, the post-operative complication was less when compared to the conventional anastomosis technique.
Keywords: Laser anastomoses, LAVA, Microanastomosis, OMFS reconstruction
Introduction
Successful microvascular-free flap transfer has advanced considerably in recent decades and has been established as a proven method for addressing all kinds of reconstructive challenges [1]. Despite the intricate surgical sequences involved, free flap transfer is now the gold standard for the reconstruction of head and neck surgical defects [2]. As free flap transfer allows the restoration of both functions and aesthetics in one stage, the application of this method has been widely practiced, although it is extensive in time consumption. With the development of new flaps, refinements in surgical techniques, larger surgical volumes and technological advancements, the success rates of free flaps are about 95% [3]. The success of free flap surgery is predominantly dependent on the proper anastomosis technique with minimal vessel coaptation time. There are several ways to anastomose blood vessels. The conventional microsuturing is the most commonly used technique of anastomosis wherein, vascular couplers and Anastoclips are in use despite the exuberant cost and rare availability [4]. Among these methods, laser-assisted vascular anastomosis (LAVA) had recently gained popularity among the microvascular surgeons. Due to its ease of application, cost-effectiveness and considerable less application time help the operator to execute flawlessly and patent anastomosis.
Although LAVA has been studied in several animal models, very few literature reports exist in human studies. In our study, we had compared and assessed the efficacy of LAVA with conventional microsuturing techniques in various post ablative orofacial defect patients.
Methods
The prospective, randomized case–control study was performed to assess the efficacy of laser-assisted vascular anastomosis with conventional suturing methods free flap for reconstruction of orofacial defects. Compare the efficacy of laser-assisted vascular anastomosis (LAVA) in microvascular-free flap reconstruction of the orofacial defects, with that of conventional suturing. The study was carried out in the Department of Oral and maxillofacial at SRM Dental College, Ramapuram, Chennai for a period of 5 years after obtaining institutional ethical committee clearance (SRMDC/2015/MDS/404). Sample groups included patients with orofacial defects resulting from ablative surgery for benign tumors who required immediate reconstruction. The exclusion criteria included patients with malignant lesions and irradiated tumors.
Informed surgical consent was obtained for patients undergoing reconstruction under general anesthesia. Based on the technique of anastomosis, 60 patients were randomly divided into two groups comprising 30 in each. Group 1 (control) comprised of patients who underwent free flap surgery with conventional microsuturing anastomosis technique. Group 2 (study) consisted of patients in which the Laser-assisted vascular anastomosis (LAVA) technique, was performed. All patients were examined and subjected to routine investigations according to the type of clinical situation.
Surgical Technique
Vessels were prepared as for normal microvascular anastomosis and 4% lignocaine solution was used to reduce vessel spasm. With the aid of a surgical microscope, approximating microvascular clamps were placed proximally and distal to the anastomotic site. After partially stripping the adventitia of the vessels, the edges of the vessels are evenly trimmed by micro-scissors. The lumen is washed with heparin saline solution (100 iu/ml) to clear the blood clots before the anastomotic procedure.
Conventional Vascular Anastomosis
In the control group containing 30 samples, the vessels were prepared as above and the vessels were sutured with 8-0 or 9-0 Ethilon®. The suture was passed at a distance from the margin of the vessel similar to that of the thickness of the wall. A counterforce was applied while passing the needle through the vessel by holding the forceps open inside the lumen instead of grasping the vessel wall, which may damage the edge of the vascular structure. After the suture has passed through both ends of the vessel, a small ‘tail’ of 2–3 mm is left so that the knot can be performed while seeing the suture end within the field of the surgical microscope. The next suture was placed in the exact opposite side (at 180°). The third suture was placed in between the first and the second, and two more interrupted sutures are placed on the same side. After finishing one side, the vascular clamps were turned to expose the other side of the anastomosis and a similar suturing method was employed. The clamps were removed after suturing and patency of blood flow was checked.
Laser Anastomosis
In the LAVA group of 30 patients, the vessels were prepared in a usual manner and 3- STAY sutures using 8-0 ethilon were placed under the microscopic magnification (X10) at approximately 120° opposite to the vessel end. All excess irrigation fluids were removed and the clamps approximated to remove all longitudinal tension. We used diode LASER (ZOLAR®) with a wavelength of 810 nm, at a power of 2000 mW, in continuous mode (Figs. 1, 2, 3, 5).
Fig. 1.
Laser unit
Fig. 2.
Soft tissue diode laser
Fig. 3.
Vessel preparation
Fig. 5.
Laser welding
The long ends of two sutures were grasped with jeweler’s forceps the tension at the right angles to the vessels to approximate and evert the vessel edges. Methylene blue dye is now applied to the approximated vessel walls to absorb the LASER energy (Fig. 4). The laser was set as a continuous wave (CW) at output powers of 2000 mW (Fig. 5). The anastomosis was achieved by a total of 6–9 shots on the vessel wall, 2–3 shots between each suture of 0.6 mm spot diameter, 5 s duration and 2000 mW power using diode lasers with a fibro optic probe. Later, the vessel was opened to circulation by unfastening both clips; the distal first. Patency of the vessel was checked (Fig. 6). Time from beginning to completion of anastomosis was recorded, ischemic time, any leakage from the vessel, pulsation, tissue perfusion was also recorded intraoperatively.
Fig. 4.
Dye application
Fig. 6.
Vessel Anastomosis
Intraoperative Assessment
The recipient site was assessed for the size, side and situation of the defect and suitable recipient vessels were isolated. The facial artery, superior thyroid artery, and vein, external jugular vein, internal jugular vein were used for anastomosis and all the vessels were anastomosed in the end to end fashion.
Anastomotic Leakage
After releasing the clamps, the leakage of blood at the Anastomotic site was assessed and graded for each sutured vessel. Grade I—immediate bleeding that stops without intervention. Grade II—light bleeding that can be stopped by gentle pressure. Grade III—heavy bleeding that requires re-clamping and additional suturing.
Patency Rate
The patency was evaluated after anastomosis at the intervals between 5 and 15 min by milking the vessel and flip test. Immediate refilling established patency, while slow refilling suggested vessel spasm, partial thrombosis or technical error, while no refilling indicated thrombosis or severe technical error.
Tissue Perfusion
Color of the tissue before and after anastomosis was noted. If the color of the tissue attained the original color after anastomosis, the blood flow through the vessel was considered normal. If the color was paler, it was considered abnormal.
Statistical Analysis
Statistical analysis was done using a t test. The unpaired t test was used to analyze the Anastomotic time, while Fischer’s exact test was used to analyze the qualitative parameters in both the groups.
Results
The current study is a prospective, randomized case–control clinical trial comparing laser-assisted microvascular anastomosis with conventional suturing during the reconstruction of orofacial defects. A total of 60 patients were included in this study. Of these, 37 were male and the remaining 23 were female. The age ranged from 17 to 51 years, with the mean age being 20 years. All the 60 patients underwent primary reconstruction after resection of benign pathologies. The histopathological diagnoses of all the 60 patients were benign lesions with bony defects. Out of 60 patients, 36 were treated with vascularised free fibular flap and 23 patients who had soft tissue defects were treated with radial forearm-free flap.
Sixty patients were evenly divided into 2 groups, in group I, 30 patients were treated by the conventional way of venous anastomosis using sutures and in group II, 30 patients were subjected for LASER anastomosis.
Evaluation of Clinical Outcomes
The clinical outcomes of each group were assessed for leakage in the area of anastomosis, duration of anastomosis, flap ischemic time and operating time (Tables 1 and 2).
Table 1.
Group I: microvascular anastomosis using microsutures
| S. No. | Anastamotic time (mins) | Patency | Leakage | Ischemic time (mins) |
|---|---|---|---|---|
| Case 1 | 20 | Immediate | Absent | 362 |
| Case 2 | 18 | Immediate | Absent | 376 |
| Case 3 | 20.2 | Immediate | Absent | 372 |
| Case 4 | 20.4 | Immediate | Absent | 390 |
| Case 5 | 19.6 | Immediate | Present | 386 |
| Case 6 | 17.4 | Immediate | Absent | 385 |
| Case 7 | 20.5 | Immediate | Absent | 395 |
| Case 8 | 20 | Slow | Absent | 378 |
| Case 9 | 18.4 | Slow | Absent | 370 |
| Case 10 | 16.5 | Immediate | Absent | 412 |
| Case 11 | 19.8 | Immediate | Absent | 386 |
| Case 12 | 17.8 | Immediate | Absent | 392 |
| Case 13 | 20 | Immediate | Present | 368 |
| Case 14 | 19.5 | Slow | Absent | 375 |
| Case 15 | 22 | Immediate | Absent | 364 |
| Case 16 | 18.2 | Immediate | Absent | 370 |
| Case 17 | 17.8 | Immediate | Present | 384 |
| Case 18 | 19.5 | Immediate | Absent | 388 |
| Case 19 | 16.8 | Immediate | Absent | 412 |
| Case 20 | 20 | Slow | Absent | 406 |
| Case 21 | 20.4 | Immediate | Absent | 379 |
| Case 22 | 20.8 | Immediate | Absent | 387 |
| Case 23 | 19.5 | Immediate | Absent | 398 |
| Case 24 | 20.8 | Immediate | Absent | 407 |
| Case 25 | 22.4 | Immediate | Absent | 389 |
| Case 26 | 23.6 | Immediate | Present | 379 |
| Case 27 | 20.7 | Immediate | Absent | 395 |
| Case 28 | 19.8 | Immediate | Absent | 373 |
| Case 29 | 20.6 | Immediate | Absent | 365 |
| Case 30 | 21.4 | Slow | Absent | 403 |
Table 2.
Group II: microvascular anastomosis using laser
| S. No. | Anastamotic time | Patency | Leakage | Flap ischemic time (hours) |
|---|---|---|---|---|
| Case 1 | 4.2 | Immediate | Absent | 138 |
| Case 2 | 3.6 | Immediate | Absent | 143 |
| Case 3 | 3.8 | Immediate | Absent | 135 |
| Case 4 | 4.7 | Immediate | Absent | 133 |
| Case 5 | 5.1 | Immediate | Absent | 149 |
| Case 6 | 3.4 | Immediate | Absent | 144 |
| Case 7 | 2.7 | Immediate | Absent | 130 |
| Case 8 | 2.9 | Immediate | Absent | 131 |
| Case 9 | 3.9 | Immediate | Absent | 139 |
| Case 10 | 4.3 | Immediate | Absent | 146 |
| Case 11 | 2.7 | Immediate | Absent | 141 |
| Case 12 | 4.9 | Immediate | Absent | 147 |
| Case 13 | 5.3 | Immediate | Absent | 139 |
| Case 14 | 4.2 | Immediate | Absent | 133 |
| Case 15 | 2.8 | Immediate | Absent | 148 |
| Case 16 | 3.2 | Immediate | Absent | 133 |
| Case 17 | 4.7 | Immediate | Absent | 141 |
| Case 18 | 2.9 | Immediate | Absent | 141 |
| Case 19 | 3.7 | Immediate | Absent | 135 |
| Case 20 | 4.2 | Immediate | Absent | 138 |
| Case 21 | 3.5 | Immediate | Absent | 141 |
| Case 22 | 3.6 | Immediate | Absent | 133 |
| Case 23 | 4.2 | Immediate | Absent | 134 |
| Case 24 | 2.8 | Immediate | Absent | 145 |
| Case 25 | 3.4 | Immediate | Absent | 145 |
| Case 26 | 3.9 | Immediate | Absent | 143 |
| Case 27 | 4.5 | Immediate | Absent | 124 |
| Case 28 | 4,6 | Immediate | Absent | 139 |
| Case 29 | 3.8 | Immediate | Absent | 130 |
| Case 30 | 2.9 | Immediate | Absent | 143 |
Leakage at the Site of Anastomosis
Leakage of blood at the Anastomotic site of veins for the group I and group II were assessed and graded for each sutured vessel. In group I, grade I leakage was seen in four cases, while in group II, no leakage was seen.
Patency
The milking test was done to confirm the patency in both groups. In group I, slow vessel patency was seen in four cases, while in group II, immediate patency was observed in all cases.
Anastomotic Time.
The mean time taken for anastomosis was 19.75 min in group I and 3.86 min in group II. This difference was found to be extremely statistically significant (p < 0.00001, Table 3).
Table 3.
Evaluation of the outcome for Anastomotic time and Ischemic time
| Variable | Group | N | Standard deviation | T value | p value |
|---|---|---|---|---|---|
| Anastamotic time | I | 30 | 2.59 | 48.65 | < 0.00001 |
| II | 30 | 0.69 | 48.65 | < 0.00001 | |
| Ischemic time | I | 30 | 203.64 | 86.71 | < 0.00001 |
| II | 30 | 38.15 | 86.71 | < 0.00001 |
Ischemic Time
The mean ischemic time of the free flap harvested was 384.87 min in group I and 138.7 min in group II. This difference was also found to be extremely statistically significant (p < 0.00001, Table 3).
Discussion
Reconstruction of maxillofacial defects using microvascular-free flaps is the most versatile method in the present era, with the advent of tremendous technological advancements, the outcome of the microvascular surgery has become easy and results are predictable. Although all the steps in microvascular surgery are important, the phase of anastomosis plays a remarkably predominant role in achieving positive results. Like the ladder of reconstruction, various methods of anastomosis have also been introduced. Besides the several intricacies are faced in the overall procedure, venous anastomosis is still a challenge in some cases even in the experienced hands of microsurgeons. The reestablishment of circulation to the flap within the ischemic time is the main challenge faced by the surgeons to obtain a high success rate. The latest methods help to a greater extent by not only connecting the vessels but also alleviate the need for vessel preparation before the anastomosis. When the vessels, especially the veins are minimally manipulated the post-anastomotic blood flow will be sustained after the procedure until the flap heals. Similarly, when the insult to the intimal layer (always happens with microsuturing) is avoided, the post-anastomotic spasm is also prevented. Conventional suture materials can cause multiple tissue reactions leading to the occurrence of aneurysms and vessel occlusions. The learning curve and the time taken to anastomose a vessel using conventional sutures are also quite high. Hence an ideal method for fulfilling the criteria such as less operating time, minimal venous manipulation and ease of application is required. This is found in laser-assisted vascular anastomosis (LAVA).
Even though various animal trials have been proved successfully, application in humans is rarely subjected and recorded. The first reported successful laser-assisted vascular anastomosis (LAVA) was carried out by Jain and Gorisch. Following that, several studies have been conducted evaluating the LAVA technique, which have showed that it is possible to fuse arterial and venous tissue with laser energy [5].
Considering the various other methods in performing anastomosis, vascular couplers and Anastoclips are in use, however, patients from economically deprived society has the least possibility to afford these couplers and staplers. The ease of application and least time consumption are the undeniable factors observed in these methods like couplers and staplers.
When comparing the other parameter of insult to the intimal layer, the conventional microsuturing involves the myointimal layers of the vessels causing progressive, myointimal hyperplasia of the arteries [6]. On the other hand, LAVA anastomosis has shown noninvolvement of the deeper layer even in later stages [7]. However, the first two key sutures before applying the lasers are inevitable [8]. But in our cases, most of the anastomosis was done without applying the stay sutures, instead, the vessels were held manually for applying the lasers.
The post-operative aneurysm in the anastomotic vessel on the later stages has been reported in various animal studies based on their histological reports [9]. However, the development of aneurysms is also reported to be less in laser anastomoses as compared to hand-sewn anastomoses, for vessels between 1 and 4 mm in diameters [10]. When such an analysis is to be conducted in humans, noninvasive methods have to be used to assess the aneurysm. In our study, no such aneurysmal induced thrombosis noticed in both the methods. Even in the cases of LAVA anastomosis, late thrombosis resulting from venous stasis was noted. On the other hand, anastomosis done by conventional suturing has shown a considerable degree of vasospasm in the early post-operative period and intervened to reestablish the microcirculation. But in both groups, the aneurysm was not the cause of thrombosis.
When compared to the conventional hand-sewn anastomoses, LAVA has shown several advantages. It takes lesser time to perform than hand suturing, which means reduced ischemic time for the flap, less exposure to anesthesia, and less operating time. LAVA provides intima-to-intima contact with minimal or no intraluminal foreign (suture) material which should theoretically decrease the rate of thrombosis. LAVA can also manage vessel size mismatches better than traditional suturing techniques. One more distinct advantage is the use of a fiber-optic contact probe in LAVA, which is more convenient for head and neck microvascular-free tissue transfer, as vessel anastomosis is often performed in a limited space.
In our study, there was a significant decrease in anastomotic time which in turn reflected a reduction in ischemic time and the total operating time. The operating time was reduced by almost an hour on average. In this study, the anastomosis time for LAVA was just 8 min on an average compared to standard suturing which was 35 min. There was no tearing of vessels or any thrombus formation. There was immediate refilling of the vessels without any leakage at the Anastomosis site. The good healing process of the Tunica media in the first post-operative weeks minimizes the risk of stenosis or pseudoaneurysm formation. The LAVA technique favoring excellent parietal repair of microvessels could be considered to be a good challenge to conventional manual anastomosis [6]. Certain studies have suggested that LAVA has limited tensile strength compared to that of suture anastomosis. This should have reflected in the outcome. However, our study did not show any incidence of anastomosis failure, and all the flaps that used LAVA survived and healed uneventfully.
The main limitation of this study is the limited sample size. With the results of this pilot study, a larger randomized trial is being planned to properly evaluate the effects of each particular type of anastomosis.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
Footnotes
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