Secondary Logo

Journal Logo


Should 1 or 2 Venous Anastomoses Be Done in Microsurgical Flap Transfer?

Khan, Sara MBBSa; Khan, Zuhera MBBS, FCPS(Plastic Surgery)a; Ali, Mohsin MBBSb; Shaikh, Safdar Ali FCPS(Plastic Surgery)a; Rahman, Mohammad Fazlur FCPS(Plastic Surgery)a

Author Information
doi: 10.1097/SAP.0000000000002309
  • Free


Free tissue transfers are now being done routinely with high success rates.1 However, complications do occur, and the main cause of reexploration and flap failure is venous thrombosis.2,3 The success of free flap surgery is dependent on a successful arterial and venous anastomosis. It is common for free flaps to have 2 veins, and with the large number of vessels in the neck, it is often possible to perform a second venous anastomosis without compromising the first. A subject of debate among microvascular surgeons is whether 1 or 2 venous anastomoses should be performed when there are 2 draining veins. Many authors have reported routinely performing 2 venous anastomoses, but their rationale for doing so is not clear, particularly when both venous anastomoses are performed to the venae comitantes of the same donor vessels, which usually have multiple interconnections.4 Whether or not multiple venous anastomoses reduce the risk of free flap failure and reexploration of free flap is a subject of controversy.5 Some microsurgeons have advocated multiple venous anastomoses for reducing the risk of venous failure and reexploration,5–8 believing that this method functions in a self-compensating manner and affords protection against venous crisis when one of the venous anastomoses is occluded. Ross et al9 and many researchers still prefer multiple anastomoses described in recent reports.10–13

The efficacy of the method has not been verified, however. In contrast, others doubt the efficacy of multiple anastomoses.14,15

Futran and Stack15 have reported no difference in the rate of flap survival and reexploration rate between single and dual venous anastomoses through a retrospective review.

Studies have reported an incidence of reexploration after venous crisis up to 13.3%16 in patients who undergo free flap surgeries. Reexploration was higher in the 1-vein group (15.7%), whereas in the dual-vein group, it was 5.6%.16


The rationale of the study is to assess reexploration after venous crisis in free flap surgeries for reconstruction of soft tissue defects in our population. No recent data related to this issue are available in Pakistan. Hence, it is important to investigate the current and local magnitude of reexploration in free flap surgery, as it can cause a significant health burden on the community. Hence, there is an urgent need to find this out and to make strategies for further research in this respect to improve the quality of care we provide to these patients and decrease patient morbidity.


This study aimed to compare the frequency of reexploration secondary to venous thrombosis in free flap surgeries in reconstruction of soft tissue defects with 1-vein versus 2-vein anastomosis.


The study was conducted at the Department of Plastic Surgery, Aga Khan University Hospital, Karachi, Pakistan. It was a retrospective cohort study including 298 patients, of which 180 were in the 2-vein group and the remaining were in the 1-vein group. After approval from the institutional review board, data were collected by chart review. The study duration was from January 2017 to December 2018. All patients of either sex who underwent free flap surgery with either 1 or 2 venous anastomosis were included. Exclusion criteria were patients with peripheral vascular diseases and flap failure after 5 days. The sampling technique was nonprobability consecutive sampling. Data were analyzed in SPSS 21. Quantitative variables were reported as mean ± SD and was assessed by independent t test, whereas qualitative variables were reported as frequency and percentages and were assessed by χ2 test/Fisher exact test when applicable. Unadjusted relative risk was reported by using univariate Cox regression analysis to assess the relationship of significance of factors with primary outcome, with P value <0.05.

The decision for the number of veins was made on the surgeons' discretion, operative time, surgeon fatigability, and perioperative assessment of flow in veins, as well as assessment of orientation and position of the second vein.


A total of 298 free flaps were included in the study, of which 254 were for head and neck reconstruction, 37 for the lower limb, and 7 for other sites. The 1-vein group had 118 free flaps, whereas 180 free flaps were included in the 2-vein group (Fig. 1).

Distribution of cases in both groups and number of cases reexplored.

Our overall flap success is 95%. Most commonly performed flaps were anterolateral thigh flap (ALTF) and free fibula flap in both groups. Oncological procedures were the most common reason of reconstruction in both groups, followed by trauma. A total of 29 cases showed signs of vascular compromise within 5 days of admission, of which 9 were due to arterial insufficiency and 20 had venous thrombosis (Table 1).

TABLE 1 - Age Groups of Patients in the Study
Age Groups, y Frequency (n = 298) Mean, y Median, y Mode, y Range, y SD
<20 22 (7.83%) 44.14 45.0 45 84 16.235
21–41 101 (33.89%)
41–60 133 (44.63%)
>61 42 (14.09%)

The association of age, sex, comorbidities (diabetes mellitus, hypertension, ischemic heart disease, asthma, aplastic anemia), addiction (smoking, tobacco chewing, and alcohol), and preoperative radiation with flap outcome was analyzed (Table 2), and we observed no significant difference in the 2 groups. The effect of on the flap of the operating surgeon and the recipient venous system was also analyzed, with the latter having a significant association with flap outcome (0.009), as shown in Table 3. The comparison of the demographic and clinical factors among patients with 1 vein and 2 veins is also shown (Table 4). We observed no significant difference of these factors in the 2 groups. Using the Cox regression univariate analysis, we found that comorbidities were significantly associated with reexploration rate (P = 0.013); however, other variables were not significantly associated with reexploration. Similarly, we did not find any significant association of age, sex, comorbidities, addiction, and preoperative radiation and number of veins with flap outcome at P value <0.05 (Table 5).

TABLE 2 - Demographics of Patients With Flap Outcome
Total No. Cases (n = 298) Flap Outcome P
Survived (n = 284) Failed (n = 14)
Age, mean ± SD, y 44.40 ± 16.160 38.93 ± 17.477 0.219
 Male 264 (88%) 252 (95.45%) 12 (4.76%) 0.666
 Female 34 (12%) 32 (94.11%) 2 (5.9%)
Addiction 209 (70.13%) 201 (96.17%) 8 (3.82%) 0.602
Comorbidities 141 (47.31%) 139 (98.58%) 2 (1.5%) 0.477
Preoperative radiation 18 (6.0%) 17 (94.4%) 1 (5.5%) 0.590
No. veins
 Single vein 118 (39.59%) 112 (94.91%) 6 (5.08%) 0.787
 Dual vein 180 (60.40%) 172 (95.55%) 8 (4.44%)
Comorbidities: diabetes mellitus, hypertension, ischemic heart disease, asthma, and anemia; addiction: smoking, tobacco chewing, and alcohol.

TABLE 3 - The Effect of the Surgeons' and Recipient's Venous System on Flap Outcome
Flap Outcome P
Survived (n = 284) Failed (n = 14)
 RMFA 155 (54.57%) 4 (28.6%) 0.057
 SAFS 129 (45.42%) 10 (71.4%)
Venous system
 IJV 155 (54.6%) 3 (21.4%) 0.009*
 EJV 38 (13.4%) 2 (14.3%)
 IJV tributaries 43 (15.14%) 1 (7.1%)
 Cephalic vein 22 (7.7%) 3 (21.4%)
 Posterior tibial vein 7 (2.5%) 1 (14.3%)
 Anterior tibial vein 1 (0.4%) 1 (7.1%)
 Popliteal venae comitantes 14 (4.9%) 2 (14.3%)
 Superficial temporal vein 2 (0.7%) 0 (0.0%)
 Great saphenous vein 2 (0.7%) 0 (0.0%)
*Significant at P < 0.05 by using Fisher exact test.
EJV, external jugular vein; RMFA, Mohammad Fazlur Rahman; SAFS, Safdar Ali Sheikh.

TABLE 4 - (A) Distribution of Type of Flaps, (B)Distribution of Cases According to Etiology, and (C) Demographics in Each Group
1 vein (n = 118) 2 veins (n = 180) P Value (<0.05)
(A) Site of reconstruction in both groups
 Head and neck 102 (86.44%) 151 (83.88%) 0.090
 Lower limbs 11 (9.32%) 27 (15.00%)
 Trunk and other 5 (4.23%) 2 (1.11%)
(B) Distribution of type of flap in both groups
 Free fibula 53 (44.2%) 67 (37.4%) 0.15
 ALTF 49 (41.5%) 77 (43.0%)
 Radial forearm free flap 3 (2.5%) 20 (11.2%)
 Lateral arm flap 6 (5.1%) 13 (7.3%)
 Latissimus dorsi 1 (0.8%) 0 (0.0%)
 Other 6 (5.1%) 2 (1.1%)
(C) Distribution of cases according to etiology in both groups
 Cancer 104 (88.1%) 158 (87.8%) 0.701
 Trauma 10 (8.5%) 19 (10.6%)
 Electric burn 2 (1.7%) 2 (1.1%)
 Others 2 (1.7%) 1 (0.6%
(D) Demographics of cases in both groups
 Age, y 46.90 ± 14 44.58 ± 16 0.37
  Male 102 (86.44%) 162 (90%) 0.357
  Female 16 (13.55%) 18 (10%)
 Addiction 75 (63%) 128 (71.1%) 0.465
 Comorbidities 51 (43.22%) 70 (43.33%) 0.561
 Preoperative radiation 6 (5.08%) 12 (6.6%) 0.629

TABLE 5 - (A) Univariate Analysis to Determine the Relationship of Demographics of Patients and Type of Procedure With Flap Outcome and (B) Reexploration Rate
Variable Unadjusted Relative Risk (95% CI) P
(A) Univariate analysis of demographics of patients and type of procedure with flap outcome
Sex 0.907
 Female 0.966 (0.541–1.724)
 Male (referent) 1
Addiction 0.458
 Yes 1.368 (0.598–3.126)
 No (referent) 1
Comorbidities 0.143
 Yes 1.551 (0.862–2.789)
 No (referent) 1
Age (20–70 y) 0.962 (0.539–1.717) 0.896
Preoperative radiation 0.965
 Yes 0.988 (0.566–1.723)
 No (referent) 1
No. veins 0.872
 1 0.944 (0.464–1.917)
 2 (referent) 1
(B) Univariate analysis of demographics and  type of surgery with reexploration rate
Sex 0.904
 Female 0.972 (0.616–1.534)
 Male (referent) 1
Addiction 0.122
 Yes 0.609 (0.325–1.141)
 No (referent) 1
Comorbidities 0.013*
 Yes 0.562 (0.356–0.887)
 No (referent) 1
Age (20–70 y) 0.976 (0.619–1.540) 0.918
Preoperative radiation 0.761
 Yes 0.935 (0.605–1.445)
 No (referent) 1
No. veins
 1 0.675 (0.420–1.087) 0.106
 2 (referent) 1
*Significant at P < 0.05 by univariate Cox regression analysis.

Of 289 free flaps, 20 showed a sign of venous compromise, of which n = 5 (4%) were in the 1-vein group and n = 15 (8.3%) were in the 2-vein group (Fig. 2). Almost all flaps in the 2-vein group were reexplored, and salvage rate was 64%. In the 1-vein group, only 2 of 5 cases were reexplored, and salvage result was 50%. The detail of the cases is given in Table 6.

Reexploration rate of flaps in both groups.
TABLE 6 - Summary of Cases With Venous Insufficiency
Site of Reconstruction Flap No. Veins 1st Vein 2nd Vein Reexploration Flap Outcome
1 Left cheek/buccal ALTF 2 IJV IJV Yes Salvaged
2 Left cheek/buccal ALTF 2 IJV IJV Yes Salvaged
3 Right buccal mucosa RFFF 2 Cephalic vein Common facial vein Yes Failed
4 Tongue ALTF 2 EJV IJV Yes Failed
5 Left mandible Fibula 2 Br: of IJV Cephalic vein Yes Salvaged
6 Left buccal
Drains put pressure on veins
7 Right buccal
Lateral arm 2 Common facial vein EJV Yes (external compression) Salvaged
8 Right buccal
Lateral arm 2 Cephalic Cephalic vein Yes Salvaged
9 Mandible Fibula 2 IJV EJV Yes
IJV was thrombosed, EJV was partially clogged, clot was removed, anastomosis was revised, and the second vein was anastomosed with cephalic vein.
10 Lower limb ALTF 2 Anterior tibial vein Anterior tibial vein Yes, late exploration Failed
11 Lower limb ALTF 2 Popliteal venae comitantes Popliteal venae comitantes Yes Failed
12 Lower limb ALTF 2 Popliteal venae comitantes Popliteal venae comitantes No
Late presentation
13 Lower limb ALTF 2 Posterior tibial vena Great saphenous vein Yes Salvaged
14 Lower limb ALTF 2 Posterior tibial vena Venae comitantes Yes Salvaged
15 Lower limb ALTF 2 Posterior tibial vena Venae comitantes Yes Salvaged
16 Left buccal/cheek ALTF 1 Cephalic vein Yes Salvaged
17 Lower limb LD 1 Posterior tibial vein Yes
Thrombosed veins due to hematoma
18 Trunk ALTF 1 Cephalic vein No
Family refusal
19 Mandible Fibula 1 Common facial vein No
The patient was unfit for second procedure.
20 Palate Lateral arm 1 Cephalic No
Late presentation; surgeon did not reexplored
EJV, external jugular vein; LD, latissimus dorsi; RFFF, radial forearm free flap.


Microvascular procedures have now become the backbone of reconstruction of complex defects, most commonly after oncological, traumatic, or infective injury.

Riot et al7 have reported free flap success rates of 97.48% in systemic meta-analysis. However, complications do occur even in experienced hands. Most common complications are vascular, especially venous thrombosis, which has been reported as high as 61.7% of the reason of reexploration.6 Venous thrombosis is more common possibly because artery has more elastin in its wall that prevents collapse.

There is debate whether 1 or 2 venous anastomoses should be done in free flaps to avoid venous complications, which have been studied by Riot et al,7 Khaja et al,16 Hanasono et al,17 and Silverman et al18 and many other researchers.

To review this, in our population, we performed a cohort study in which 298 free flaps were done, of which 180 had double venous anastomosis and 118 had single venous anastomosis. The overall flap success rate was 95.63%, and we found no association of flap survival with number of venous anastomosis. This is also supported by Futran and Stack,15 Hanasono et al,17 and Silverman et al.18

In our study, 29 cases showed postoperative ischemia due to vascular compromise, of which 20 cases had venous thrombosis.

The flap reexploration was higher in the dual venous group (8%; P = 0.106). The higher exploration rate in the dual group is different from international studies, which have a lower reexploration rate in the 2-vein anastomosis group.5,7,9,15,17,19

Although we had a higher exploration rate in the dual group, salvage rate was also better in the dual group.

The effect of preoperative radiation was considered as one of the factors for flap failure. In our study, 17 patients had preoperative radiation, but only 1 developed venous complication, However, Bourget et al20 have found no negative effects of radiation on free tissue transfer survival.

The flap outcome was also analyzed between the head and neck after oncologic resection and the lower limbs for traumatic defects. In our study, the head and neck free flap success rate was 96.53%, and that in the lower limb was 86.84%, which is comparable to Li et al,21 with a reported success rate of 85.42%.22 There was a significant lower success rate in the lower limb due to trauma. The success rate of <95% has been considered acceptable in contrast to head and neck reconstruction.22

Some studies choose the internal jugular vein (IJV) because it has higher pressure and lower rate of thrombosis.23,24 Our study shows no difference in IJV thrombosis and flap outcome.

Venous complication in relation to the recipient's venous system at different sites were also analyzed separately to draw conclusion of using specific veins at given sites. Statistically, it has a significant effect on flap outcome (0.009), but it does not demonstrate the superiority of one system over other because there are many other factors that could lead to thrombosis as supported by Futran and Stack15 and several other researchers.4,23,25

The workhorse flaps in our study were ALTF and free osteocutaneous fibular flap, followed by lateral arm and radial forearm. Flaps with dual venous systems like radial forearm and deep inferior epigastric artery perforator flaps have deep and superficial draining systems, and the drainage in these flaps improves by anastomosing 2 different systems. In flaps with single venous system like ALTF, fibula, and latissimus dorsi, performing a single vein usually suffices. This is supported by Hanasono et al.17 They measured the velocity of blood in venae comitantes before pedicle division and after completion of anastomosis, and concluded that single venous anastomosis has a positive effect on flap survival, and it prevents venous thrombosis and consequently suggested second venous anastomosis when technically feasible.17,18 In our study, we analyzed flap outcomes with flap types and number of venous anastomosis. We found more failures of ALTF in the dual group, but this was not statistically significant, although Lee et al10 and Chen et al5 support better outflow in dual venous drainage with less risk of flap failure in ALTF.19 In the free fibula group, we found no difference in the success rates comparing 1 vein versus 2 veins, which is supported by Han et al26 and Heidekrueger et al.2 Hence, our study shows that doing a second vein does not improve the outcome but increases operating time.

We think that it is not only the number of venous anastomosis that defines the success of flap but also multiple other factors that can affect the outcomes, like potential changes in pedicle diameter and flow postoperatively, or changes in flap vasculature, tension on vascular anastomosis, meticulous flap harvest technique, and general status of the patient.

Our study's limitations include it being a retrospective and single-center study.

Cumulative sample size is good, but unequal distribution of cases in each group impacts the results, so in our conclusion, the argument of doing single or dual is still not clear.


We believe that both groups have similar outcomes. Second venous anastomosis should be considered whenever possible.


1. Wei F-C, Mardini S. Flaps and Reconstructive Surgery E-Book. Philadelphia, PA: Elsevier Health Sciences; 2016.
2. Heidekrueger PI, Ehrl D, Heine-Geldern A, et al. One versus two venous anastomoses in microvascular lower extremity reconstruction using gracilis muscle or anterolateral thigh flaps. Injury. 2016;47:2828–2832.
3. Stranix JT, Anzai L, Mirrer J, et al. Dual venous outflow improves lower extremity trauma free flap reconstructions. J Surg Res. 2016;202:235–238.
4. Chalian AA, Anderson TD, Weinstein GS, et al. Internal jugular vein versus external jugular vein anastamosis: implications for successful free tissue transfer. Head Neck. 2001;23:475–478.
5. Chen WF, Kung YP, Kang YC, et al. An old controversy revisited—one versus two venous anastomoses in microvascular head and neck reconstruction using anterolateral thigh flap. Microsurgery. 2014;34:377–383.
6. Yang G. Forearm free skin flap transplantation; report of 56 cases. Natl Med J China. 1981;61:139.
7. Riot S, Herlin C, Mojallal A, et al. A systematic review and meta-analysis of double venous anastomosis in free flaps. Plast Reconstr Surg. 2015;136:1299–1311.
8. Valentino J, Funk GF, Hoffman HT, et al. The communicating vein and its use in the radial forearm free flap. Laryngoscope. 1996;106:648–651.
9. Ross GL, Ang ES, Lannon D, et al. Ten-year experience of free flaps in head and neck surgery. How necessary is a second venous anastomosis?Head Neck. 2008;30:1086–1089.
10. Lee Y-C, Chen W-C, Chen S-H, et al. One versus two venous anastomoses in anterolateral thigh flap reconstruction after oral cancer ablation. Plast Reconstr Surg. 2016;138:481–489.
11. Imanishi N, Nakajima H, Aiso S. Anatomical study of the venous drainage architecture of the scapular skin and subcutaneous tissue. Plast Reconstr Surg. 2001;108:656–663.
12. Brown DH, Mulholland S, Yoo JH, et al. Internal jugular vein thrombosis following modified neck dissection: implications for head and neck flap reconstruction. Head Neck. 1998;20:169–174.
13. Kubo T, Haramoto U, Yano K, et al. Internal jugular vein occlusion in head and neck microsurgical reconstruction. Ann Plast Surg. 2002;49:490–494.
14. Demirkan F, Wei F-C, Lutz BS, et al. Reliability of the venae comitantes in venous drainage of the free radial forearm flaps. Plast Reconstr Surg. 1998;102:1544–1548.
15. Futran ND, Stack BC Jr. Single versus dual venous drainage of the radial forearm free flap. Am J Otolaryngol. 1996;17:112–117.
16. Khaja SF, Rubin N, Bayon R. Venous complications in one versus two vein anastomoses in head and neck free flaps. Ann Otol Rhinol Laryngol. 2017;126:722–726.
17. Hanasono MM, Kocak E, Ogunleye O, et al. One versus two venous anastomoses in microvascular free flap surgery. Plast Reconstr Surg. 2010;126:1548.
18. Silverman DA, Przylecki WH, Arganbright JM, et al. Revisiting the argument for 1- versus 2-vein outflow in head and neck free tissue transfers: a review of 317 microvascular reconstructions. Head Neck. 2016;38:820–823.
19. Chaput B, Herlin C, de Bonnecaze G, et al. One versus two venous anastomoses in anterolateral thigh flap reconstruction after oral cancer ablation. Plast Reconstr Surg. 2017;139:807e–808e.
20. Bourget A, Chang JT, Wu DB-S, et al. Free flap reconstruction in the head and neck region following radiotherapy: a cohort study identifying negative outcome predictors. Plast Reconstr Surg. 2011;127:1901–1908.
21. Li X, Cui J, Maharjan S, et al. Reconstruction of the foot and ankle using pedicled or free flaps: perioperative flap survival analysis. PLoS One. 2016;11:e0167827.
22. Medina ND, Fischer JP, Fosnot J, et al. Lower extremity free flap outcomes using an anastomotic venous coupler device. Ann Plast Surg. 2014;72:176–179.
23. Hong P, Taylor SM, Trites JR, et al. Use of the external jugular vein as the sole recipient vein in head and neck free flap reconstruction. J Otolaryngol. 2006;35.
24. Francis DO, Stern RE, Zeitler D, et al. Analysis of free flap viability based on recipient vein selection. Head Neck. 2009;31:1354–1359.
25. Cheng H-T, Lin F-Y, Chang SC-N. External or internal jugular vein? Recipient vein selection in head and neck free tissue transfer: an evidence-based systematic analysis. Plast Reconstr Surg. 2012;129:730e–731e.
26. Han Z, Li J, Li H, et al. Single versus dual venous anastomoses of the free fibula osteocutaneous flap in mandibular reconstruction: a retrospective study. Microsurgery. 2013;33:652–655.

free flap outcome; venous thrombosis; head and neck reconstruction; 1-vein or 2-vein anastomosis; microvascular free tissue transfer

Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.