Effect of Torsion on Patency Rate in Microvascular Anastomosis

Introduction: Although torsion at the anastomotic site is one of the factors that affect the patency rate, very few studies were found to address this issue. Aim of Work: The aim of this study is to examine the effect of torsion on microvascular anastomosis both in arteries and veins after one hour and one week. Material and Methods: The effect of torsion on arteries was studied using 60 Sprague-Dawley rats weighing 250-300 g. The rats are divided randomly into 5 groups. Rotation was done at the distal anastomotic site by 0°, 45°, 90°, 180° and 270° in groups I, II, III, IV, and V respectively. The effect of torsion on veins was studied using 50 Sprague-Dawley rats weighing 250-300 g. The rats are divided randomly into 5 groups. Rotation was done at the proximal anastomotic site by 0°, 45°, 90°, 180° and 270° in group I, II, III, IV, and V respectively. The patency rate was examined one hour and one week post operatively using the refill test. Histopathological studies were conducted and the patency rate results were analyzed using the One-tailed Fisher s exact test. Results: The patency rate in arteries was significantly affected at 270° but not at 180° both after one hour and one week. The patency rate in veins after one hour was also significantly affected at 270° but not at 180°. However, after one week the situation is different in veins as the patency rate was significantly reduced at 180°. Conclusion: This study concluded that torsion should be avoided at any cost, however small degrees of torsion most probably will not affect the artery. On the other hand, the vein is more vulnerable to the effect of torsion than the artery due to the weaker venous wall and higher arterial pressure. Another conclusion is that in experimental microvascular surgery, the patency rate should not be examined only in the acute post operative period but also after one week as the patency rate may decrease changing the results.