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Original Investigation |

Novel Irradiated Axial Rotational Flap Model in the Rodent

Adam Luginbuhl, MD1; Mara Modest, MD1; Kaiguo Yan, PhD2; Joseph Curry, MD1; Ryan Heffelfinger, MD1
[+] Author Affiliations
1Department of Otolaryngology–Head and Neck Surgery, Thomas Jefferson University, Philadelphia, Pennsylvania
2Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania
JAMA Facial Plast Surg. 2013;15(5):344-348. doi:10.1001/jamafacial.2013.963.
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Importance  Patients who require extensive surgical resection of head and neck tumors often have a history of treatment with radiation and chemotherapy. Chemoradiation-induced damage to the skin and soft tissues can cause complications following surgical reconstruction.

Objective  To design an easily reproducible rodent rotational skin flap and to evaluate the effects of radiation exposure on flap viability.

Design and Setting  Ten rats at a tertiary university medical center received 40-Gy irradiation to the abdominal wall. Following a recovery period of 1 month, a 3 × 8-cm fasciocutaneous flap based axially on the inferior epigastric vessel was raised and rotated 60° into a contralateral deficit. Five nonirradiated rats underwent the identical procedure as a control. Animals were killed 7 days postoperatively, areas of flap necrosis were documented by an observer blinded to the grouping, and histological specimens were taken to compare flap viability and vessel density.

Main Outcomes and Measures  Flap revascularization and microvascular density.

Results  Six of 10 rats in the irradiated group had necrosis of the distal flap ranging from 1 to 6 cm from the distal edge, whereas none of the animals in the control group exhibited necrosis (P < .001). Histologic analysis revealed collagen and vascular changes in the irradiated skin. Vascular density analysis revealed a significant difference between radiated and nonradiated flaps; P = .004, .03, and .01 in the distal, middle, and proximal segments of the flap, respectively.

Conclusions and Relevance  This novel rat axial rotational flap model demonstrates increased flap necrosis and a decrease in vascular density due to the effects of radiation exposure. With use of a linear electron accelerator, a dose of 40 Gy can be delivered to the skin without resulting in devastating gastrointestinal adverse effects.

Level of Evidence  NA.

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Figures

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Figure 1.
Experimental Apparatus

A, Dosimetry curve. Square indicates the shielding thickness necessary to achieve delivery of 50% of the dose from the Elekta linear accelerator to the skin and then rapidly fall off to limit irradiation to the gut. B, Holding chamber.

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Figure 2.
Incision Procedure

A, An 8 × 3-cm flap and defect; angle a = 60°. B, Identified inferior epigastric pedicle.

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Figure 3.
Differential Survival of Skin Flaps at Postoperative Day 7

A, Radiated flap; B, nonradiated flap.

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Figure 4.
Histologic Analysis

Immunohistochemical staining for von Willebrand factor shows vessels outlined by dark staining (original magnification ×200) in nonradiated tissue (A) and radiated tissue (B). Note dense fibrosis. C, Radiated tissue necrosis of epidermal elements; no definable viable cells (hematoxylin-eosin, original magnification ×200). D, Fibrosis of proximal radiated tissue. Muscular layer is replaced by fibrosis (hematoxylin-eosin, original magnification ×50).

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Figure 5.
Vascular Density of Distal, Middle, and Proximal Segments

Error bars indicate the standard deviation in the number of vessels counted per 8 high-power fields in radiated and nonradiated tissue.

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