The Influence Of Over-expansion On The Blood Supply Of Axial-pattern Flap, And The Clinical Application Of Moderate Expansion On The Pre-transfer Scapular Free Flap

The relationship of safety, quickness and efficiency is emphasized now in tissue expansion. In the clinical use of the pre-expanded axial-pattern flap, we noticed that partial necrosis of transferred flap might develop following over pre-expansion. As the limits to which axial flaps can be expanded are not yet known, this study intends to find the influence of over-expansion on the vascularity and viability of axial-pattern flap.The miniature-pig's axial-pattern buttock flaps were used. 240ml rectangular tissue expanders(8×12cm) were placed beneath the proximal parts of 8X18 skin flaps on the left (sham operation) and right (over-expanded) sides of each animal. Serial expansion was performed on the right side to IVP 100—120mmHg every 4 -5 days over 12 weeks. On the second operation the following observations were made: 1 Increase of flap area. 2 Flap's surviving length. 3 Microcirculation of the proximal, middle and distal segments of island flaps by means of skin temperature, LDF, tissue MDA content and fluorescein dye test. 4 Vasculature on latex-injected clearing specimen. 5 Histological examination.The results show. 1 The total volume averaged 780±76ml(up to three times the labeling volume of the expander used) at the end of expansion, and flap area on the expanded region increased by 97.8% following expansion, mostly at the center. 2 The expanded island flaps have litter increase in surviving length over the unexpanded, but have significantly less surviving length ratio. 3 Compared to the unexpanded island flaps, the expanded had similar skin temperature, LDF value and tissue MDA content in the proximal and middle segments; significantly lower skin temperature, LDF value and significantly higher tissue MDA content in the distal segment. The expanded also had significantly greater decrease of LDF value due to flap elevation in the middle and the distal segments. 4 Approximately 1/2 of the island flap area distally is sparsely dyed following expansion, and 1/3 of that unexpanded. 5 Vasculature examination shows the subcutaneous axial vessel branches of the unexpanded flap distributed over two thirds of the proximal area, while that of the expanded flap distributed over only half of the proximal area centripetally. 6 Histological examination shows that on the axial arterioles of the expanded flap there were swelling and disruption of endothelial cells, subendothelial proliferation of smooth-muscle cells, vessel wall thickening and stricture of vessel cavity, and enrichment of collagen fibers and infiltration of inflammatory cells all around.These findings indicate that the over-expansion would cause chronic injuries to the axial vessel network of the flaps, resulting in changes in distributing pattern and...