Purpose: The purpose of our study was to compare microvascular anastomosis performed with Coalescent Nitinol U-Clips versus conventional instrument tied interrupted nylon sutures. It was our hypothesis that U-Clips could reliably and consistently perform microvascular anastomoses in a manner comparable or superior to the current “gold standard” of interrupted nylon suture. We also hypothesized that the use of these semi-automatic anastomotic devices would reduce the time needed to make these anastomoses, thus reducing the ischemic time to the tissues.
Materials & Methods: 20 male, New Zealand white rabbits, with an average weight of 2.04 kg were used in this study. They were anesthetized by an intramuscular injection of ketamine (30 mg/kg) and Xylazine (6 mg/kg) and maintained on 2% isoflurane. All the anastomoses were performed on either the femoral artery or vein.
There were 4 groups of rabbits (n=5 per group): (1) femoral artery anastomosis using 9-0 nylon; (2) femoral artery anastomosis using U-Clips; (3) femoral vein anastomosis using 9-0 nylon; (4) femoral vein anastomosis using U-Clips.
Once the femoral vessel was exposed it was relieved of vasospasm using 2% lidocaine and the external diameter of the vessel was measured. The vessel was then clamped and transected. For the femoral artery, either 8 interrupted 9-0 nylon sutures were placed, or 4 U-Clips. For the femoral vein, either 9 interrupted 9-0 nylon sutures were placed, or 3 U-Clips. Ischemic time (from vessel clamps application to removal), and anastomosis time (from first stitch to reperfusion) were assessed. Vessel patency was evaluated using the Acland milking test and a 5 point scale (1 = Poor/Thrombosed, 3 = Moderate/Reduced flow, 5 = Excellent/Unimpeded flow).
Pending Data: Following a three week recovery period, the animals will be anesthetized and late patency and any other findings such as infection and aneurysm formation will be evaluated. Histological examination will then be done using longitudinal sections stained with hematoxylin and eosin and be evaluated for inflammation, media necrosis, subintimal hyperplasia, thrombus and aneurysm formation.
Results: The mean external diameter, ischemic time, and anastomosis time of Group 1 was 1.18 mm, 20.4 minutes (s = 5.68), and 14.3 minutes (s = 5.93), respectively. The immediate patency of every vessel in Group 1 was graded to be 5 (s = 0). In comparison, the mean external diameter, ischemic time, and anastomosis time of Group 2 was 1.3 mm, 20.2 minutes (s = 4.02), and 14.2 minutes (s = 4.02), respectively. The mean immediate patency was 4.2 (s = 0.836).
The mean external diameter, ischemic time, and anastomosis time of Group 3 was 1.9 mm, 39.6 (s = 10.8), and 29.6 minutes, respectively. The immediate patency was graded to be 4.6 (s = 0.894). In comparison, the mean external diameter, ischemic time, and anastomosis time of Group 4 was 1.98 mm, 27 minutes (s = 8.86), and 21 minutes (s = 7.74), respectively. The immediate patency was 3.4 (s = 0.547).
Discussion/Conclusion The use of U-Clips appears to be a feasible alternative to nylon suture. In our study, we found that there was no statistically significant difference between the ischemic time, anastomosis time, or patency rates when using the U-Clips or 9-0 nylon for arterial anastomosis (p=0.388, 0.288, and 0.381, respectively). Fewer U-Clips (4 clips) were needed to perform the arterial anastomosis than 9-0 nylon (8 sutures).
When used for vein anastomosis, the ischemic time, anastomosis time, as well as the patency rates demonstrated no statistically significant difference (p=0.974, 0.753, and 0.196, respectively) between the U-Clips and nylon suture. Additionally, fewer U-Clips (3 clips) were needed to perform the venous anastomosis than 9-0 nylon (9 sutures).
Additionally, since an anastomosis with U-Clips utilizes similar techniques and principles as that of nylon suture, little additional training is required to use the U-Clips. The next phase of this study will utilize this device in conjunction with the da Vinci Surgical System for robotic microsurgery.