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Low-energy lasers are currently being used in the therapy of rheumatoid arthritis, chronic pain, muscle strain, and the promotion of wound healing in human and veterinary medicine. This study examined the effects of low-energy laser on skin-flap survival in a controlled interspecies study using the rat and porcine models. Twenty dorsal skin flaps based caudally were performed in 20 rats (10 laser-treated and 10 control flaps). The wounds were closed, and the flaps were sutured over the skin. Forty dorsal pig skin flaps based medially were raised in five pigs. The flaps were treated once per day for 10 days: 4 days preoperatively, the day of surgery, and 5 days postoperatively (30 s/cm3 per day). The average surviving rat flap surface area for the laser-treated flaps was 653 +/- 112 mm (mean +/- SD) and 580 +/- 60 mm in the control flaps, which was not significant (p greater than 0.05). In the porcine model, the average surviving area for the 20 laser-treated flaps was 949 +/- 174 mm, and the control average (n = 20) was 969 +/- 147 mm, also not significant. No beneficial effect was seen with low-energy laser preoperative and postoperative treatment of skin flaps in the rat and porcine models.

Rat and pig skin flaps were used to investigate the effects of topical nitroglycerin ointment on flap survival. Significant increase in flap survival was detected and correlated well with plasma nitroglycerin levels measured during the treatment regimen. The drug was applied 1 hour preoperatively in both models. Recent experimental clinical investigations on the use of pharmacologics for treating failing flaps were reviewed, including the possible mechanism of action of nitroglycerin. Characteristics of an ideal pharmacologic agent for use in the treatment of failing flaps were delineated. Further investigation is warranted to determine the effects of nitroglycerin ointment on various other flaps, including musculocutaneous and free flaps, as well as timing of these applications. All these variables could best be studied in the pig with confirmation of other researchers prior to advocating clinical usage. Until then, the ideal pharmacologic agent for prevention of skin-flap necrosis remains unknown.

Investigations were carried out employing pig skin flaps that were wider and shorter than the conventionally used longitudinal-rectangular flaps. The following main points summarize the findings of this experimental work. (1) Circulation flows radially through the base of the skin flap, creating a tree-foliage pattern, hence an arbor flap. (2) While a large area can survive on a narrow base and short narrow pedicle, the flap will not be viable if it has a long narrow pedicle. (3) Following initial distal necrosis of random flaps, narrowing of the base does not augment further necrosis. Therefore, to ensure good survival of a small flap, it is imperative that the flap be broadened immediately adjacent to its short narrow base, giving it a tree-foliage pattern, i.e., an arbor flap instead of a rectangular flap. In other words, very small random skin flaps should be constructed like trees and their distal ends should be broader than their bases.

The pathophysiology of skin flaps raised on nonexpanded and expanded skin was studied in pigs. Skin expansion was achieved by gradual inflation of a subcutaneously implanted silicone tissue expander with sterilized isotonic saline over a period of 4 to 5 weeks. Comparisons were made of the skin flap viability and capillary blood flow among random acute and delayed skin flaps and skin flaps constructed on skin pockets implanted with noninflated or inflated tissue expanders. The extents of skin flap viability and capillary blood flow were similar among delayed skin flaps and skin flaps constructed on skin pockets but were significantly higher than those of acute random skin flaps raised on normal skin. It was concluded that skin viability and capillary blood flow in skin flaps raised on expanded skin were not compromised and the regulation of blood flow in skin flaps raised on nonexpanded or expanded skin pockets was similar to that seen in delayed skin flaps. The mechanisms of the delay phenomenon was discussed.