Purpose

As free-style local perforator flap has gained popularity in reconstructive surgery, flap rotation and pedicle twisting are conditions encountered in flap procedures unintentionally, or inevitably. There have been several animal studies that evaluated the effect of twisting on flap viability. They reported pedicle twisting over some degrees caused perfusion compromises, but a variable of pedicle length was not considered in those experiments. It is unclear whether longer pedicle lengths of flaps are less reluctant to twisting effect or not. Furthermore, there are growing chances of pedicle injury or spasm to get more sufficient pedicle lengths. So our aims of this study were to evaluate the relationships between pedicle length and viability of perforator flaps.

Methods

In the preliminary study for determination of twisting degree, 4 x 4 cm rectangular abdominal skin flaps of eight Sprague-Dawley rats based on a single cranial epigastric artery perforator were elevated and returned with 270, 360, 540, and 720 degrees of rotation, respectively. We observed significant decreases of the flap viability with 720 degrees of torsion. In the main study, forty Sprague-Dawley rats were randomly divided into four groups of 10 animals, and cranial epigastric artery perforator flaps were elevated in the same manner. In group I and II, pedicle dissections were performed to the rectus fascia level without disrupting the fascia, and in group III and IV, incision on the rectus fascia and intramuscular dissections were proceeded upto xyphoid process level to gain long pedicle lengths. The flaps were sutured in place without rotation in group I, III and with 720 degrees of rotation in group II, IV. Pedicle lengths were measured intraoperatively. The flaps were evaluated by their survival areas with Visitrak (Smith & Nephew) planimetry on 7 days postoperatively. Microangiography and histologic analysis were performed in selected cases after measurements of the flap survival areas. Statistical significances were assessed using the Mann-Whitney U test and Kruskal-Wallis test, and it was considered to be statistically significant with a value of p<0.05.

Results

All rats survived well without any problem till postoperative 7 days. The mean pedicle length of groups I, II, III, and IV were 16.1±2.8mm, 18.6±1.8mm, 40.3±5.2mm, and 42.2±2.8mm (mean±SD), respectively. The differences between the pedicle length of group I and II, group III and IV were insignificant statistically (p>0.05), but there were statically significant differences between group I and III, group I and IV, group II and III, and group II and IV (p<0.05). The mean flap survival ratios of them were 88.47±13.87%, 60.23±28.95%, 87.06±13.85%, and 84.28±31.76% (mean ± SD), respectively. There were no statistical significance of differences between the flap survival ratios of group I and III, group I and IV, and group III and IV (p>0.05). However, In group II, in which the pedicles were dissected to the rectus fascia and twisted 720 degrees, viable flap ratios were decreased significantly compared with group I, III, and IV, respectively (p<0.05).

Conclusions

To the authors' knowledge, this is the first study to objectively evaluate the relationships between the lengths of twisted pedicles and viability of perforator flaps. This results show that the obtainments of longer pedicle lengths through careful dissections with experienced hands have no significant effect on the flap viability, and protecting effects from twisting of the pedicle. If rotating of a pedicle is mandated by the topology of the local perforator flap transfer, sufficient pedicle acquisitions can ensure more secure results.

 

Table 1. Mean Pedicle Lengths and Viable Flap Ratios of Each Group
	Group I (n=10)	Group II (n=10)	Group III (n=10)	Group IV (n=10)
Pedicle length (mm)	16.1±2.8	18.6±1.8	40.3±5.2	42.2±2.8
Viable flap ratio (%)	88.47±13.87	60.23±28.95	87.06±13.85	84.28±31.76
* Group I: dissection to the rectus fascia, no rotation, Group II: dissection to the rectus fascia, 720 degrees of rotation, Group III: dissection beyond the rectus fascia, no rotation, Group IV: dissection beyond the rectus fascia, 720 degrees of rotation.  **Value are expressed as mean±SD.