Observations on experimental flow-through venous flaps

The effect of hemodynamic remodeling on the survival of arterialized venous flaps

Objective

To evaluate the effect of hemodynamic remodeling on the survival status of the arterialized venous flaps (AVFs) and investigate the mechanism of this procedure.

Materials and Methods

Two 7 x 9 cm skin flaps in each rabbit (n=36) were designed symmetrically in the abdomen. The thoracoepigastric pedicle and one femoral artery were used as vascular sources. Four groups were included: Composite skin grafts group and arterial perfusion group were designed in one rabbit; AVF group and hemodynamic remodeling group by ligation of the thoracoepigastric vein in the middle were outlined in another rabbit. Flap viability, status of vascular perfusion and microvasculature, levels of epidermal metabolite and water content in each group were assessed.

Results

Highly congested veins and simple trunk veins were found using angiography in the AVF group; while a fairly uniform staining and plenty of small vessels were observed in the hemodynamic remodeling group. The metabolite levels of the remodeling group are comparable with those in the arterial perfusion group. There was no statistically significant difference in the percentage of flap survival between the arterial perfusion group and hemodynamic remodeling group; however, significant difference was seen between the AVF group and the hemodynamic remodeling group.

Conclusions

Under the integrated perfusion mode, the AVFs are in an over-perfusion and non-physiological hemodynamic state, resulting in unreliability and unpredictability in flap survival; under the separated perfusion mode produced by remodeling, a physiological-like circulation will be created and therefore, better flap survival can be expected.

New experimental flap model in the rat: Free flow-through epigastric flap

This study describes a free flow-through flap model in the rat for use in the evaluation of the physiologic and hemodynamic characteristics of this type of flap in clinical practice. The rat is a preferred animal model because it is inexpensive, readily available, and reliable. There is no free flow-through flap model available for laboratory animals, although this model gained popularity in clinical use recently. Twenty Wistar rats weighing 200-250 g were used in our experiment. In 5 rats, the vascular anatomy of the groin and proximal thigh region was determined by anatomic dissection. The experimental design consisted of two groups. In the experimental group (N = 5), a flow-through epigastric skin flap was harvested based on the femoral artery, preparing both its proximal and distal stumps. The flap was transferred to the contralateral groin, and end-to-end vascular anastomosis was performed between a proximal and distal stump of the femoral arteries of the flap and recipient site. The proximal stump of the femoral vein of the flap was anastomosed to the femoral vein of the recipient site. The control group was divided into two subgroups. In all control group rats (N = 10), the flap was harvested in the same manner, and transferred to the contralateral groin, but standard free-flap procedure with one artery and one vein anastomosis was performed in 5 rats (conventional free-flap subgroup), and anastomosis was not performed between the flap and the recipient site in the remaining 5 rats (graft subgroup). Survival of the flap was evaluated on postoperative day 7 by direct observation, and microangiography was performed to delineate the vascularity of the flow-through flap. The results showed that all flaps survived in the experimental group and the conventional free-flap subgroup of the control group, whereas in the graft subgroup, all flaps underwent total necrosis. The authors conclude that the flow-through epigastric flap for the rat is a simple and reliable model for future physiologic and pharmacologic studies.

Secondary microsurgical reconstruction of nail problems in musicians

Nail reconstruction in musicians is an interesting and challenging undertaking for the surgeon. The second or third toenail is usually selected as a donor nail for fingernail reconstruction, because the size and shape are generally similar. A partial toe transfer from the great toe is preferred for the thumb. Reconstruction of the guitarist's dominant thumb is a typical indication for this rare procedure. The surgeon must bear in mind, however, that the cosmetic aspects cannot be overlooked in a musician who plays before the public. The surgeon, therefore, has to select the best procedure from the various methods available to provide the best functional and aesthetic result.

A radiographic perfusion study of the cephalic venous flap

The circulatory anatomy of the arterialized cephalic venous flap was investigated radiographically in five fresh cadavers. Microfil, which was dripped from the caudal end of the cephalic vein, flowed first into the concomitant veins and then into an intimate vascular network around the cephalic vein. The Microfil then flowed to a septocutaneous perforator of the radial artery through the vascular network around the cephalic vein. This suggests that in the arterialized cephalic venous flap there is a circulatory pathway by means of the cephalic vein to the venous network around the cephalic vein, to the arterial network around the cephalic vein, to the arterial system, and to the venous system returning to the cephalic vein.

Isotope perfusion and infrared thermography of arterialised, venous flow-through and pedicled venous flaps

In an experimental study on the epigastric venous system of rats, we examined three types of venous flaps with regard to their perfusion and long-term results: arterialised venous flaps, flow-through venous flaps and venous island flaps. We documented afferent and efferent blood flow with radiolabelled substances and blood distribution with infrared thermography. By measuring the surviving flap surfaces after 4 months, the relative success rate for each flap type was determined. The results show that in the chosen model the entire surface of the arterialised venous flap had a survival rate of 92.7%, the flow-through venous flap 62.4%, and the venous island flap about 31%. The venous island flaps had the worst distribution of intravenously injected 125J-Fibrinogen, and it was significantly worse in all types of venous flaps than in standard epigastric flaps; moreover, the clearance of intracutaneously injected 99mTc was the lowest in venous island flaps. The infrared thermographic study showed that the blood in the arterialised venous flaps dispersed faster and over a larger area than in flow-through venous and island flaps. Given these results, we conclude that arterialised venous flaps are the safest form of venous flaps, whereas venous island flaps carry a high risk of partial or total necrosis.

A histological and carbon perfusion study of cephalic and saphenous venous flaps in the dog

A histological and carbon-infusion study of cephalic and saphenous venous flaps in the dog shows that cephalic flaps survive significantly better than saphenous flaps, their mean viability at 5-14 days being 50-60% compared to 23.8% for saphenous flaps. Venous drainage is essential for flap survival but perfusion of the cephalic vein with arterial blood does not alter flap viability. The findings indicate that cephalic flaps survive better because they are thinner and contain a more extensive venous plexus. A cephalic flap is a suitable model for in vivo study of the circulation within a venous flap.