Do two venous anastomoses decrease venous thrombosis during limb reconstruction?

Abstract

BACKGROUND:

The optimal number of veins to be anastomosed in perforator flaps for limb reconstruction and its influence on the results remain controversial. Venous thrombosis of microvascular anastomoses is a commonly recorded complication in soft tissue reconstruction.

OBJECTIVE:

To evaluate the effect of two venous anastomoses in the incidence of venous thrombosis for limb reconstruction using anterolateral thigh (ALT) microsurgical free flaps.

METHODS:

This was a cross-sectional study on patients undergoing limb reconstruction using ALT flap during 2014–2017. Perioperative information was recorded and patients were divided in two groups: group 1 (one venous anastomosis; 17 patients) and group 2 (two venous anastomoses; 21 patients). Complications were investigated.

RESULTS:

Overall, 38 microsurgical flaps were included. The mean age was 33 years, and 32 patients were male. The most prevalent wounds were traumatic. Group 1 presented a higher complication rate than group 2 (47% vs. 24%; p = 0.065), although the difference was not significant. Group 1 presented a higher rate of venous anastomotic thrombosis (p = 0.032) than group 2. The overall success rate was 92%.

CONCLUSION:

For limb reconstruction using ALT microsurgical free flaps, two venous anastomoses are associated with a low rate of venous thrombosis in microvascular anastomoses.

Keywords

Thrombosis microcirculation free tissue flaps postoperative complication thigh/surgery

1 Introduction

Anterolateral thigh (ALT) flap is one of the most reliable option for reconstructive microsurgery. A common indication is limb coverage, where this procedure allows the coverage of large and complex wounds that cannot be managed with local flaps [1, 2]. The anterolateral thigh flap is based on perforator vessels, including one artery and two comitante veins, of the descending branch of lateral femoral circumflex artery. The perforator vessels can be septocutaneous or most commonly musculocutaneous. The microsurgical anastomoses are performed with donor vessels of the limb and the descending branch of lateral femoral circumflex artery and vein(s) [3].

A major concern when performing limb soft tissue reconstruction using microsurgical free flaps is the selection of suitable donor arteries and recipient veins, because they are frequently affected by indirect lesions after initial high-energy trauma or subsequent scarring. It is important to choose between either a superficial or a deep venous system and whether to perform one or two venous anastomoses, as these factors may influence the occurrence of venous thrombosis, a commonly recorded complication in soft tissue reconstruction [4].

The optimal number of veins to be anastomosed after limb reconstruction using microsurgical free flaps and its influence on the reconstruction results remain controversial. Therefore, the present study investigated the results of one versus two venous anastomoses for limb reconstruction using ALT flaps. ALT flap is the most commonly used perforator flap, and two veins are available to be used as drainage. The present study analyzes the influence of two venous anastomoses on the occurrence of venous thrombosis requiring flap take-back to the operating room, for limb reconstruction using ALT flap.

2 Methods

We conducted a cross-sectional study including all consecutive patients undergoing upper and lower limb reconstruction using ALT microsurgical flap at our institution from July 2014 to January 2017. No patients were excluded, and all patients provided informed consent. Microsurgical free flaps were indicated for patients with either traumatic or oncologic soft tissue defects that could not be covered by local flaps.

The database included patient demographics (age, sex, and comorbidities); laboratory test results (preoperative hemoglobin levels and platelet counts); and perioperative information, such as the type of arterial anastomoses (end-to-side versus end-to-end), number of venous anastomoses, whether veins from the superficial or deep system (or both) were chosen as recipient vessels, and ischemia time of the microsurgical free flap, defined as the time between clamping the vessels of the flap and after suture of microvascular anastomoses, releasing the clamp of the artery and at least one vein (in cases where more than one vein was performed) and perfusion of the flap was obtained and the time elapsed in minutes was recorded. All microvascular anastomoses were hand-sewn. Patients were divided into two groups according to the number of anastomosed veins: group 1 (one venous anastomosis) and group 2 (two venous anastomoses). Both groups were managed with the same postoperative protocol of oral and intravenous hydration, analgesia and aspirin 200 mg two times a day until patient discharge from Hospital. Flap venous outflow was confirmed through clinical evaluation by the medical team every 4 h during the first 48 h and every 6 h until discharge from the hospital. The clinical parameters evaluated were: color, temperature, tactility, capillary refill, bleeding, and appearance of the flap. The suspicion of compromising these clinical parameters indicated the revision of anastomoses.

Statistical analysis was performed using SPSS 20.0. Anemia was defined as hemoglobin levels <11 g/dL [World Health Organization (WHO)] and thrombocytosis as platelets level ≥450×10⁹/L. Obesity was defined as body mass index >30 kg/m² (WHO). We considered p < 0.05 as statistically significant. Qualitative data were analyzed by Pearson chi-square test or Fisher exact test. Mann–Whitney U-test was used for quantitative nonparametric data.

3 Results

A total of 38 patients, i.e., 38 microsurgical flaps, were included, among whom 32 were male (Fig. 1). The patient mean age was 33 years (range: 15–69 years). Three patients were obese, with body mass index >30 kg/m². The distribution of comorbidities among patients was similar in both groups 1 and 2, including obesity.

Fig.1

Male, aged 28 years, had a motorcycle accident resulting in Gustilo IIIB elbow open fracture. He underwent dynamic external fixation and anterolateral thigh flap reconstruction 17 days after trauma.

The most prevalent indication for limb reconstruction were traumatic wounds (25 microsurgical free flaps). Three patients were run over by a car, three had work-related accidents, and two had a car accident (Fig. 2). Most lesions were located in the lower limbs (n = 30; Fig. 3).

Fig.2

Number of patients per ALT flap indication for wound coverage.

Fig.3

Percentage of patients by lesion site.

The mean pre- and postoperative hemoglobin levels were 10.88 g/dL [standard deviation (SD), 1.88 g/dL] and 9.85 g/dL (SD, 1.46 g/dL), respectively. The mean preoperative platelet count was 372.34×10⁹/L (SD, 166.7×10⁹/L). The number of patients exhibiting pre- and postoperative anemia were 21 and 31 patients, respectively, and 32 patients required blood transfusion to maintain hemoglobin levels >10.0 g/dL.

The mean intraoperative ischemia time in using microsurgical flap was 113.7 min (SD, 44.5 min). For lower limbs, the most commonly used donor artery was posterior tibial artery (n = 19), followed by anterior tibial artery (n = 8) (Fig. 4). For upper limbs, radial artery was used in 4 cases and ulnar and brachial arteries were used in 2 cases each. End-to-end artery anastomosis was seen in 12 cases, and end-to-side artery anastomosis was seen in 26 cases. The distribution of arterial anastomoses by type was similar in groups 1 and 2.

Fig.4

Male, aged 26 years, had a motorcycle accident resulting in Gustilo IIIB leg open fracture. He underwent external fixation and anterolateral thigh flap reconstruction 18 days after trauma.

The following complications were observed in 12 patients: 3 cases of infection, which were successfully resolved with surgical debridement and antibiotics; 3 cases of partial flap loss, wherein <20% of the flap was lost, which were treated with vacuum-assisted closure device and skin graft; 3 cases of successful microanastomoses revision, among which 1 was due to arterial thrombosis and 2 were due to venous thrombosis; and 3 cases of total flap loss, which included 2 unsuccessful revision due to venous thrombosis. Among patients with total flap loss, a second Latissimus dorsi microsurgical flap was used in one patient, a local sural flap and skin graft was used in another patient, and below-knee amputation was required in one patient (Fig. 5).

Fig.5

Number of patients classified according to complications.

The group 1, receiving one venous anastomosis, included 17 patients, whereas group 2, receiving two venous anastomoses, included 21 patients (Table 1). All venous anastomoses were performed in an end-to-end fashion. At least one comitant vein (deep system) of donor artery was chosen in 35 cases. The mean ischemia time was similar in both groups (p = 0.245), and group 1 presented more complications than group 2, although the difference was not significant (47% and 24% for group 1 and group 2, respectively; p = 0.065). No risk factors were identified for complications or total flap loss. Anastomoses revision was performed in 5 patients (4 in group 1 and 1 in group 2) (Fig. 6). Regarding the incidence of venous thrombosis, all 4 occurrences were within group 1 (p = 0.032). The overall success rate of using ALT flaps for soft tissue coverage of limbs was 92%.

Table 1

Comparison of demographic and clinical factors between groups

Number of venous anastomoses	One vein n = 17	Two veins n = 21
Variable	Mean (SD)	Mean (SD)
Age (Average years)	31.0 (10.4)	34.4 (15.1)
Body mass index (kg/m²)	24.2 (3.8)	25.7 (4.9)
Ischemia time of ALT (min.)	108.3 (30.4)	118.0 (53.7)
Length of hospitalization (days)	36.2 (21.6)	26.9 (16.1)
Preoperative hemoglobin levels (g/dL)	10.8 (2.4)	10.9 (1.4)
Preoperative platelet count level (×10⁹/L)	366.9 (191.6)	376.8 (143.8)
Variable	Number (n)	Number (n)
End-to-side artery anastomosis	12	14
End-to-end artery anastomosis	5	7
Traumatic lesion	15	20
Presence of complications	8	4
ALT: Anterolateral thigh flap; SD: standard deviation

Fig.6

Patients according to the microvascular thrombosis.

Fig.7

Venous anastomosis (A) and venous thrombosis (B).

4 Discussion

Since its first description by Song et al [5] in 1984, ALT flaps gained popularity over the last 20 years and are used to treat complex lower extremity wounds with better results than other types of flaps, such as muscle flaps [2 , 7]. In cases with osteomyelitis, this method provides the resolution of infection through the obliteration of dead spaces and the provision of vascularized tissue for wound healing [8].

ALT flaps are reliable microsurgical free flaps for limb coverage, presenting a constant anatomy with septocutaneous or, more frequently, musculocutaneous perforators, with long and adequate pedicle diameter and usually containing two comitant veins available for anastomoses [9 –11]. Another advantage of ALT flaps is their versatility as they provide a thin flap, are sensate, and may obliterate the dead space in limb lesions [12].

The success rates for free flap surgeries are currently high, however pedicle thrombosis is still a major concern. Based on extensive literature in prevention of coronary disease that supports the safety and efficacy of aspirin as an inhibitor of platelet aggregation with prostaglandin cyclo-oxygenase synthesis and reduction of thromboxane A₂ production [12]. Although the little evidence of reduction of complications with the utilization of antithrombotic agents [13], aspirin is still recommended for thrombosis prophylaxis in microsurgery varying between 100 to 325 mg per day in postoperative period or low-dose of aspirin (1–5 mg/Kg) [14 –16]. Our protocol includes 200 mg of aspirin per day in thromboprophylaxis and we did not observed the raise in the incidence of revision surgery due to hematoma as demonstrated by Lee and Mun [12]. Moreover, as free flaps for limb reconstruction have higher rates of complications [17], including thrombosis, we still recommend low-dose aspirin in postoperative period, but we agree with Kearns et al [18] that the risk of microvascular thrombosis need to be stratified for correct indication of antithrombotics in high risk cases.

An open discussion remains regarding venous system selection, and some authors [19 –21] refer to the advantages of using two separate venous systems for drainage. In the present study, the main indication of ALT flaps were traumatic injuries, where it was performed over 7 days after trauma (85%), and the deep venous system was selected in 92% of all microsurgical flaps. Lorenzo et al [22] describes that for traumatic cases, the superficial venous system is less reliable than the deep venous system, given the risk of spasm and the possibility for vascular lesions of the endothelium. Therefore, we used deep venous system for most cases and recommend that at least one comitant vein should be chosen for venous anastomoses.

The classic study of Hanasono et al [23] demonstrated that microsurgical free flaps for head, neck, and breast reconstruction resulted in reduced venous flow with two venous anastomoses when compared to one. On the contrary, Lee et al [9] described that two venous anastomoses maximize the venous outflow, although they did not investigate its influence on the results. Silverman et al [24] demonstrated that for head and neck reconstruction, two venous anastomoses for outflow minimizes venous congestion in microsurgical flaps, which may be due to the second venous anastomosis working as a backup vein. Lee et al [25] reported the same finding in oral reconstruction after cancer ablation, with lower occurrence of flap take-backs and venous congestion in the two venous anastomoses group. Regarding limb reconstruction, Heidekrueger et al [26] could not demonstrate different results with two venous anastomoses in 201 ALT flaps for lower extremity reconstruction but observed a longer surgery time with two venous anastomoses (p < 0.05). In our study, one venous anastomosis was associated with a higher complication rate (p = 0.065%) and a higher risk of venous thrombosis.

Deciding whether to perform one or two venous anastomoses for limb reconstruction using microsurgical free flaps depends on anatomical factors, such as vascular pedicle length and position, and on the number of suitable recipient veins close to the pedicle after high-energy trauma or extensive resection in tumor reconstruction. Ultimately, it is an individual choice of the surgeon, which may contribute to a bias, as it may not be possible to predict whether cases with one or two venous anastomoses will represent technical intraoperative difficulties. One limitation of this study is the small number of patients, which might have led to a type II error.

5 Conclusion

We conclude that two venous anastomoses for limb reconstruction using ALT microsurgical free flaps is associated with a lower rate of venous thrombosis in microvascular anastomoses.

Footnotes

Acknowledgments

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