The use of thermography to design tissue flaps - experimental studies on animals

Abstract

Introduction: Methods allowing one to locate the position of a cutaneous perforator do not allow one to determine the boundaries of the vascularized skin. In clinical practice this causes complications in the form of marginal necrosis of the flap.

Aim: To examine the usefulness of thermography to assess the extent of vascularization of the skin and subcutaneous tissue by a single perforator.

Material and methods: Thirty-one male rats were used. Using dynamic thermography the perforators on the abdominal skin were located. Afterwards the flap was prepared on a randomly chosen perforator. After 24 h the extent of vascularization of the skin by a single perforator was examined.

Results: In 22.5% of cases the number of perforators marked in the thermography was equal to the number of perforators marked intraoperatively, in 64.5% it was lower and in 13% higher. The use of thermography has shown that basing the flap vascularization on the perforator with low efficiency resulted in statistically more frequent occurrence of ischemia and partial necrosis of the flap (p = 0.024). Partial necrosis of the flap occurred in 12 of 31 cases, always in the area in which during the preoperative thermography no perforators were found. The areas of necrosis occurred irrespectively of the distance from the supplying vessel.

Conclusions: When designing the shape of the flap, the distribution of all perforators must be considered. The perforators need to be included in the area of prepared tissues because their location indicates the area with a more efficient network of vessels.

Keywords: flap; perforator; thermography.

Photo 1

Strength of the perforator evaluated using thermography: weak perforator – 1; average perforator – 2; dominant perforator – 3

Photo 2

Prepared flap on a randomly chosen perforator (yellow arrow)

Photo 3

Quality of blood supply after 24 h: flap with necrotic areas (red ellipse); blood supplied perforator (yellow arrow)

Photo 4

Quality of blood supply after 24 h: flap with ischemic area (red ellipse); blood supplied perforator (yellow arrow)

Photo 5

Quality of blood supply after 24 h: flap properly supplied with blood; blood supplied perforator (yellow arrow)

Figure 1

Strength of the perforator evaluated with thermography: weak perforator – 8 cases; average perforator – 15 cases; dominant perforator – 8 cases

Figure 2

Quality of blood supply after 24 h: flap with necrotic areas – 12 cases; flap with ischemic area – 12 cases; flap properly supplied with blood – 7 cases

Figure 3

Average quality of blood supply after 24 h relative to strength of the perforator

Figure 4

Distance of the perforator from the edge of the necrosis and the edge of the flap without necrosis

Figure 5

Shows the abdominal skin flap schemes (radar charts) in which the necrosis occurred. The center of the chart represents a perforator on which the blood supply of the flap was based. On the axes were marked: the distance [mm] and the direction from the perforator to: borders of the necrotic areas: black color , borders of the healthy tissue areas: green color , borders of the areas containing other perforators: yellow color . The directions on the chart are indicated by the numbers 1–8, direction 1 refers to the cephalad part of the flap, direction 5 refers to the caudad part of the flap

Figure 6

Compatibility of thermography (T) and intraoperative evaluation (I) in defining the number of perforators