Cutaneous vascular anatomy of the thoracic region of the dorsum and its role in flap design in the rat

A new lateral thoracic artery perforator flap design with multiple vascular territories in rats

BACKGROUND

To describe a new design for an extended lateral thoracic artery (LTA) perforator flap and investigate its anatomical, dynamic, and potential territories.

MATERIALS AND METHODS

To assess vascular territories, rats were randomized according to LTA perforator flap type into the surgical groups A, hemidorsal island flap; B, entire dorsal island flap; and C, reduced-size dorsal island flap.

RESULTS

On postsurgical day 7, the surviving flap areas were 95%, 92%, and 89% in groups A, B, and C, respectively. Necrosis most commonly occurred in the contralateral LTA territories in groups B and C. The immunoreactivities of intercellular adhesion molecule 1 and vascular endothelial growth factor receptor 2 in dynamic territories, as choke vessel markers, were increased.

CONCLUSIONS

We clarified the LTA perforator flap nomenclature and defined its pedicle course and anastomosing patterns; furthermore, we demonstrated that the LTA perforator did not anastomose with its counterpart because of its unidirectional, oblique, and craniocaudal course. The LTA perforator flap was found to be a good model comprising multiple vascular territories and exhibiting continuous necrosis.

Neo-vascularisation of musculocutaneous and muscle flaps after division of the major vascular supply: an experimental study

BACKGROUND AND AIM

Experimental studies have shown that musculocutaneous flaps are not dependent on a major pedicle for survival after 7-8 days, as revascularisation occurs from surrounding well-nourished tissue. However, muscle component loss in myocutaneous flaps after pedicle division has been reported. No study that examines the nature of the vascular ingrowth from underlying beds by blocking the peripheral cutaneous beds has been conducted in musculocutaneous and skin-covered muscle flaps. This study was designed to investigate the origin of the dominant source of neo-vascularisation after interruption of the major vascular supply in island musculocutaneous and island skin-covered muscle flaps by blocking neo-vascularisation from wound edges and the recipient bed.

METHOD

Twenty-eight rats were divided into four experimental groups. In group I, a cutaneous maximus musculocutaneous island flap (MCIF) was raised, and the wound edges of the flap were blocked with a silastic sheet. In group II, an MCIF was raised, and the recipient bed was blocked with silastic. In group III, an island cutaneous maximus muscle flap (IMF) was raised as an island flap covered by a full-thickness skin graft (FTSG), and the wound margins were blocked with silastic. In group IV, an IMF was raised as an island flap covered by an FTSG, and the recipient bed was blocked with a silastic sheet. On the seventh postoperative day, vessel ligation was performed in each animal. Microangiographic studies and histopathological evaluations were performed 14 days after the first operation.

RESULTS

In microangiographic studies, neo-vascularisation was more prominent in groups II and IV (the groups in which the recipient beds were blocked) than in groups I and III (the groups in which the wound edges were blocked). Upon histopathological examination, the number of vessels was significantly lower in group I and group III than in group II and group IV (p<0.001).

CONCLUSIONS

Our findings revealed that neo-vascularisation from either the recipient bed or the wound edges was sufficient to ensure full flap survival in musculocutaneous flaps, and skin-grafted muscle flaps do not need major axial vessels 7 days after flap elevation in rats if the recipient bed or wound edges are well-vascularised. The results also indicated that revascularisation mainly comes from the peripheral wound edges and is independent of flap type.

Canine lateral thoracic fasciocutaneous flap: an experimental study

For the purpose of reconstructive surgery training and research, we have developed a new skin flap model: canine lateral thoracic fasciocutaneous flap. Anatomical study found that the lateral thoracic arteries in dogs have similar anatomical characteristics to human's ones. Based on these vessels, if a skin flap was designed within the vessels territory (size 5 x 8 cm) it could survive completely, whereas, if designed beyond the vessels territory (size 5 x 14 cm) would result in partial necrosis of the flap. This fasciocutaneous flap model closely simulates the human surgery and could be valuable for training and research. Furthermore, this flap could be applied in the veterinary practice for reconstruction of canine forelimbs and cervical area.

Free flap transfer to the dorsum of the rat: a new technique to avoid autocannibalization in free flap studies

In this report the authors describe a new method that avoids autocannibalization by free transfer of a flap to the dorsum of the rat by means of a simple exposure technique. A total of 22 Wistar rats of both sexes (weight, 200-290 g) were used in this experiment. An anatomic study performed in 12 rats revealed that a wide exposure could be created in the axillary fossa by retracting the inferior tip of the scapular bone superiorly (after severing its attachments with the deep extrinsic back muscles), the latissimus dorsi muscle laterally, and the serratus anterior muscle medially. Furthermore, after obtaining vessel diameter measurements, it was ascertained that the subscapular and the lateral thoracic vessels could serve as the recipient vessels. Based on the anatomic study, a total of 10 conventional groin cutaneous flaps, measuring 2 x 3 cm in size, were harvested based on the femoral vessels and transferred to the dorsum of the same animal by the exposure method as just described, with microvascular anastomoses performed between the femoral vessels of the flap and either the subscapular artery and the lateral thoracic vein (N = 5) or the lateral thoracic artery and vein (N = 5). Results showed that 9 of the 10 transplanted flaps were totally viable on postoperative day 7, giving a success rate of 90%, with one failing flap belonging to the latter group. The authors conclude that by this simple method of recipient vessel exposure in the axillary fossa, free flap transfer to the dorsum of the rat is a simple and reproducible technique by microvascular anastomoses performed between the pedicle vessels of a flap and the subscapular artery and the lateral thoracic vein. This model offers the unique advantage of a dorsally located flap that is protected by autocannibalization. Moreover, daily observation and monitoring of the flap are easy and practical without the need to have the animal wear protective material such as vest.

An extended dorsal island skin flap with multiple vascular territories in the rat: A new skin flap model

BACKGROUND

The use of various animal skin flap models can lead to difficulty in the interpretation of experimental findings. Establishment of an axial-pattern flap model with predictable necrosis is desirable for the study of the flap pathophysiology.

MATERIALS AND METHODS

Twenty rats were injected with a lead oxide, gelatin, and water mixture through the carotid artery to investigate the cutaneous vascular anatomy. Each cutaneous perforator on the rat dorsum was dissected to its source artery. The skin was removed and radiographed to define its vascular architecture. On the basis of the initial angiographic data, an extended dorsal island skin flap (based on the unilateral deep circumflex iliac artery) measuring up to 8 x 9 cm was designed in 10 rats to assess the viability of the flap. The boundaries of the flap are defined by anatomical landmarks to standardize the flap for rats of different sizes. The upper margin was located at the level of the tip of the scapula and the lower margin at a level 2 cm below the iliac crest. All flaps were observed for 7 days postoperatively and the surviving flap area was calculated as a percentage of total flap dimensions using the paper template technique.

RESULTS

Most of the skin of the rat dorsum is supplied by three arteries: the deep circumflex iliac artery (DCIA), the posterior intercostal arteries (PIA), and the lateral thoracic artery (LTA). The DCIA anastomoses with the ipsilateral PIA and the contralateral PIA and DCIA. The average percentage survival of the skin flap is 70.5 +/- 4.8% (mean +/- SD).

CONCLUSIONS

The extended dorsal island skin flap has a consistent vasculature and has a predictable distal necrosis area. This new model is felt to be appropriate for skin flap physiological studies.

Comparison of flash lamp pulsed-dye laser (585 nm) and conventional surgery in the delay of random dorsal rat flaps

BACKGROUND AND OBJECTIVE

Delay is a basic surgical technique used by flap surgeons to improve the blood supply to the distal parts of a random skin flap. The aim of this study was to determine whether a scarless delay can be done by the use of the flash lamp pulsed-dye laser operating at a wavelength of 585 nm.

STUDY DESIGN/MATERIALS AND METHODS

The pilot study showed that 6 J/cm(2) had a selective photothermolysis effect and therefore was chosen for testing the delay procedure on 15 rats. The percentage of flap necrosis of this group was compared to the results of 15 rats that underwent delay by surgery and 15 rats that were not treated prior to flap surgery (control group).

RESULTS

Laser delay of McFarlane flaps resulted in an average of 15.5% smaller necrotic area compared to the control group (52.7% +/- 14.4% and 68.2% +/- 9.6%, respectively, P < 0.01) and was as effective as surgical delay (53.3% +/- 13.6%).

CONCLUSIONS

The results indicate that the flash lamp pulsed-dye laser operating at 585 nm is effective for delaying cutaneous flaps in the rat model.

Comparison of two different delay procedures in a rat skin flap model

The overall objective of this study was to investigate how a strategic delay procedure could generate large flaps survival. On the basis of the vascular anatomy in 10 rats, a long three-territory skin flap spanning the length of the rat dorsum was designed. This flap was distally based on the deep circumflex iliac artery. The adjacent territories consisted of a large perforator of the posterior intercostal artery and the lateral thoracic artery in sequence. Two different vascular delay procedures were used and compared in nine animals. One dorsal midline incision was used to perform the two different delay procedures. The limited delay technique was performed by ligating a large cutaneous perforator of the posterior intercostal artery on one side of the rat. The extensive delay procedure was completed by ligating the cutaneous perforators of the posterior intercostal artery and the lateral thoracic artery on the other side of the rat. After a delay period of 10 days, the paired flaps were elevated, respectively, and sutured back in place. Seven days later, the area of viable skin flap was measured by the paper template technique. The animals were then killed, and the dorsal skin arteriograms were obtained by injecting a lead oxide mixture. Vascular changes of the paired flaps were assessed. In the extensive delay group, 100-percent survival was seen in four animals and distal partial necrosis was observed in five animals. The average survival area in the extensive delay group was 85.5 +/- 14.2 percent (mean +/- SD), whereas the flaps in limited delay group showed 100-percent survival in all animals (p < 0.05). In flaps that survived completely, the choke vessels among three vascular territories anastomosed throughout the flap. In the partially necrotic flaps, some choke and true anastomoses existed between the deep circumflex iliac and the posterior intercostal artery territories and the flap necrosis occurred in the third territory. This study suggests that the limited delay technique (ligation of one artery in the territory adjacent to the base of the flap) was the more effective delay procedure in the rat dorsal skin flap model.