INTRODUCTION

A number of microvascular anastomotic systems have been developed as alternatives to sutures in an attempt to reduce both the anastomotic complication rate and ischaemic time in free flap surgery. Nakayama et al. in 1962₁,₂ first developed an microvascular anastomotic device consisting of 2 metallic rings with 12 interlocking pins, and this was later modified by Ostrup and Berggren in 1986₃ into the current Unilink/3M® microvascular anastomotic coupling device. Experimental studies have demonstrated patency rates₅,₆ and histological features similar to conventional sutured anastomoses, with the added advantage of greater mechanical strength₄. The clinical effectiveness of this device has also been demonstrated in the setting of breast and head and neck reconstruction ₈,₉,₁₀,₁₁.

OPERATIVE TECHNIQUE/METHODS

A retrospective review of operative reports and clinical records was undertaken for patients who had undergone free flap reconstruction using the Unilink/3M® microvascular anastomotic coupling device at the MD Anderson Cancer Center between June 1995 and August 2000. Data was obtained on the success rate of anastomoses using the coupler and any intraoperative or postoperative flap complications.

The Unilink/3M® microvascular anastomotic coupling device consists of 2 high density polyethylene ring with 12 stainless steel locking pins, and is available in 1.0mm, 1.5mm, 2.0mm, and 2.5mm sizes. There is a vessel-measuring gauge (Fig1) to allow determination of the vessel diameter and the correct coupler size.

Figure 1

Figure 1: Vessel-measuring gauge

The coupler is loaded onto the application device, and the 2 ends of the vessel are sequentially pulled through the rings and everted over the pins (Figs 2&3).

Figure 2

Figure 2: Loading into application device

Figure 3

Figure 3: Loading into application device

The device is then closed, taking care to ensure tight apposition of the rings (Fig 4).

Figure 4

Figure 4: Closure of device

Figure 5

Figures 5 & 6 show completed anastomoses.

Figure 6

RESULTS

One hundred anastomoses were performed in 100 free flaps using the Unilink/3M® microvascular anastomotic coupling device between June 1995 and August 2000. There were 6 males and 76 females, with a mean age of 47.7 years. The device was used for the venous anastomosis in 96 flaps, and for both the arterial and venous anastomoses in 4 flaps. All anastomoses were performed in an end-to-end fashion. Ninety-one flaps were performed for breast reconstruction and 8 for head and neck reconstruction. There were 54 unilateral TRAM flaps, 18 bilateral TRAM, 4 VRAM, 3 fibula, 1 DCIA, 1 latissimus dorsi, and 1 scapular flap (see Table I). In 2 TRAM flaps and 1 bilateral TRAM flap (total 4) both the arterial and venous anastomoses were performed using the coupler. Flap survival was 100%.

Figure 7

Table 1: Flaps and anastomoses performed using the Unilink/3M® coupler

The recipient vessels are shown in Table II. The most common recipient vessels were the thoracodorsal vessels, but the internal mammary, lateral thoracic, facial, external jugular and superficial temporal vessels were also used. The recipient vessel diameter was typically 2.5 to 3.0mm, but occasionally vessel diameters of 2.0-2.5mm and 3.0-3.5mm were anastomosed using the coupler. 88 of the 100 venous anastomoses were performed using the 2.5mm coupler (88%), with the remainder performed using the 2.0 size coupler (12%). All 4 arterial anastomoses were performed using the 2.0mm coupler.

Figure 8

Table 2: Recipient vessels for anastomoses performed using the Unilink/3M® coupler

Anastomoses were completed successfully using the coupler in 100 out of 105 attempted cases (95%). Five anastomoses were converted intraoperatively to sutured anastomoses. Two veins had very thin walls that could not be placed over the pins of the device without tearing the vessel wall, and 2 veins had very thick walls, which resulted in significant reduction of the lumen following anastomosis with the 2.5mm coupler. The one arterial anastomosis that was abandoned intraoperatively was in a small artery (<2mm) using a 1.5mm coupler. Two venous anastomoses were revised intraoperatively using the coupler for the second anastomosis, 1 because of a twist in the vein (no anastomotic problem, ?no thrombosis). There was 1 late venous thrombosis (23 days postoperatively), not associated with flap loss. The average time for anastomosis was less than 5 (?4) minutes (have we got a range?). In addition there were 2 postoperative arterial thromboses (1 on the same day and 1 on the second postoperative day) in sutured anastomoses, which were revised without any further flap complications. Three TRAM flaps developed fat necrosis (3.3%), 2 of which required operative debridements. There were no other flap complications.

DISCUSSION

The microvascular anastomosis remains the most critical aspect of free flap surgery, with technical problems at the anastomosis accounting for a high proportion of free flap failures. Efficient and safe performance of this step minimizes flap ischaemia time and reduces the risk of complications associated with anastomotic thrombosis and ischaemia-reperfusion injury₁₂,₁₃. There are also financial implications with regard to operating time and the frequency of revision surgery for complications₁₄.

Traditional sutured microvascular anastomoses have an accepted failure rate of 2-5%₁₅, and they remain the yardstick for comparison when considering alternative anastomotic methods4. Potential aetiologies for microanastomotic thrombosis include endoluminal lacerations leading to subendothelial collagen exposure, inadequate eversion of the cut edges, luminal narrowing due to excessive eversion of the cut edges, and vessel distortion due to uneven placement of sutures, size discrepancies, tension or torsion₁₆.

Standard microsurgical principles apply when performing anastomoses using this coupler, and potential technical pitfalls must be avoided when performing the procedure. In the Unilink/3M® microvascular anastomotic coupling device, the 6 pins are evenly placed around the polyethylene ring, but the onus remains on the surgeon to distribute the vessel edge evenly round its circumference to prevent intraluminal excess and to take adequate bites to ensure optimal eversion when the coupler is closed. Luminal size discrepancy between the vessel and the ring is considered to be critical by some workers9, while others10 do not regard this to be a problem. However, it seems sensible to apply the principles learnt from sutured anastomoses, that is, minimize size discrepancies and avoid constrictions.

In this series 3 of the 5 anastomoses that we abandoned intraoperatively were due to discrepancy between the vessel wall and the coupler. 2 of these were in veins that had very thick walls, and there was one arterial anastomosis in a small artery (<2mm) using a 1.5mm coupler. In these cases inappropriate choice of coupler size resulted in significant narrowing of the lumen following the anastomosis. There was 1 intraoperative revision using the coupler for the second anastomosis for a twist in the vein, also reinforcing the point that standard microsurgical principles of avoiding tension and twisting apply when using this technique.

Once the technical aspects and the learning curve9 have been taken into account, then the test of efficacy of such a device lies in the anastomotic patency rates and the savings in time. This study has illustrated clearly that the patency rates with the Unilink/3M® microvascular anastomotic coupling device are comparable to those of conventional sutured anastomoses, with only 1 postoperative thrombosis (1%), and a 100% flap survival rate. Moreover, the average time taken for each anastomosis was 5 minutes, representing a 400% increase in efficiency over an average 20 minute sutured anastomosis. This reduction in total operating time more than compensates for the cost of the device.

CONCLUSION

The Unilink/3M® coupling device is a safe and efficient method for performing microvascular venous anastomoses, allowing reduced operating time in free flap surgery.