Perfusion and Oxygenation of Random Advancement Skin Flaps Depend More on the Length and Thickness of the Flap Than on the Width to Length Ratio

Abstract

Objective: The aim was to investigate the relationship between the dimensions (length, width, and thickness) of random advancement skin flaps and retained tissue perfusion and oxygenation.

Methods: Flaps were raised on the flanks of pigs. The flaps were either 0.5 or 1.0 cm wide, thin (dissected halfway through the subcutaneous tissue) or thick (dissected down to the muscle fascia). Tissue perfusion was measured by laser Doppler velocimetry, and tissue oxygenation (pO2) was measured using a Licox system, every 0.5 cm along the flaps' length. Tissue temperature was visualized by high-resolution infrared camera.

Results: Perfusion and oxygenation decreased gradually from the base to the tip of the flap, reaching approximately 40% of presurgical values (2.0 cm) and approximately 20% (2.5 cm) from the base of the flap. There was virtually no blood flow, nor oxygen tension, 3.0 cm from the base of the flap. The width to length ratio of the flap did not determine blood flow or oxygenation, being approximately 30% in a 0.5 cm wide and 2 cm long flap, and 0% in a 1.0 cm wide and 4 cm long flap, both with a width to length ratio of 1:4. Blood flow and oxygenation were preserved to a greater extent in the thick flaps (∼40%) than in the thin flaps (∼20%), in a 0.5 cm wide and 2 cm long flap.

Conclusions: The dissection of a random advancement flap results in hypoperfusion and oxygenation that cannot be predicted by the width to length ratio but depend on the length and thickness of the flap.

Keywords: blood flow; experimental; oxygenation; perfusion; random flaps.

Figure 1

Photograph of the flaps dissected on the pig's flank (width: 1.0 cm; length: 4 cm). The flaps were either thin (top) or thick (bottom).

Figure 2

Blood flow (left) and oxygenation (right) at increasing distances from the flap base. The data are from both 0.5 and 1.0 cm wide thin and thick flaps (n = 24). The results are presented as scatterplots with a line through the median values. The results show the importance of the length of the flap in retaining blood flow and oxygenation.

Figure 3

Random advancement skin flap (1 × 4 cm) on the pig flank, 1 hour after surgery, at the time of perfusion and oxygenation measurements. It can be seen that approximately the distal 2 cm of the flap is discolored.

Figure 4

Blood flow (left) and oxygenation (right) in random advancement flaps of different dimensions, with width to length ratios of 1:3 and 1:4 (both thin and thick flaps, n = 12 for each box). Note that the width to length ratio of the flap does not determine the blood flow or oxygenation. ***P < .001.

Figure 5

Blood flow (left) and oxygenation (right) in thin and thick flaps (n = 6 for each box), measured 2.0 cm from the flap base. Note that blood flow and oxygenation were preserved to a greater extent in thick than in thin flaps. **P < .01.

Figure 6

Thermographic images of 2 random advancement skin flap (1 × 4 cm) on the pig flank, 1 hour after surgery. The upper flap was made thin and the lower flap was made thick. Graph shows the drop in temperature along the length of the flaps (upper curve are thin flaps and lower curve are thick flaps), calculated as percent of a perfusion at a reference point lateral to the flap base (n = 10). Note the lower temperature seen as darkening of the distal end of the flap.