[Neovascularization of the myocutaneous rectus abdominis island flap in the rat]

The neovascularisation was investigated in 51 rectus abdominis myocutaneous island flaps (1.5 x 3.0 cm) in rats (Uje: WIST) following ligation of the pedicle vessels (superior epigastric artery and vein) without and with incision of the cranial flap border. The ligation was done on the 3rd, 4th, 5th, and 7th postoperative day. The efficiency of the neovascularisation was estimated quantitatively on the 3rd, 5th, and 7th day after vascular ligation by measurement of the necrotic flap tissue. The findings are expressed in percent of the whole flap area. Vascular pedicle ligation on the 3rd or 4th postoperative day caused an average necrosis rate of 98% and 84% respectively. No flap survived in these experimental group. In case of pedicle vessel occlusion on the 5th postoperative day without incision of the cranial flap border all myocutaneous flaps survived, partly with focal loss of the epidermis. Placing the ligation after incision of the flap border on the 5th day an average necrosis rate of 34% was found, only 5 out of 11 flaps survived. All flaps (n = 9) remained viable following vascular pedicle ligation on the 7th postoperative day. It seems necessary to observe myocutaneous flaps carefully until the 14th postoperative day, because tissue damages due to vascular pedicle occlusion on the 4th day may become visible not before the 10th or 11th postoperative day. Opening of the myocutaneous flap borders between the 5th and 7th postoperative day should be avoided.