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Development of an irradiated rodent model to study flap revascularization.

OBJECTIVE
To develop a reproducible free-flap animal model to study the effects of irradiation on flap revascularization.


DESIGN
After institutional animal care and use committee review and approval, 16 Sprague-Dawley rats were subjected to either 23- or 40-Gy electron beam irradiation to their ventral abdominal wall. After a recovery period, the animals then underwent a ventral fasciocutaneous flap pedicled on the inferior epigastric vessels with subsequent pedicle ligation at 10 days. An additional 16 rats were subjected to 40 Gy of irradiation and underwent pedicle ligation at 8 or 14 days postoperatively to determine if time to pedicle ligation affected percentage of flap viability.


RESULTS
Rats receiving 23 Gy of irradiation had the same viability as rats undergoing no radiation. Rats receiving 40 Gy of irradiation had a significantly lower average percentage of flap viability (56.9%) than animals receiving 23 Gy (90.9%) (P < .001). Furthermore, the longer duration until pedicle ligation after 40 Gy of irradiation led to significant increases in flap viability (P < .001 for analysis of variance).


CONCLUSIONS
This animal model establishes that external beam irradiation at a total dose of 40 Gy leads to significantly delayed flap revascularization over time compared with 23-Gy irradiation. This model will allow future investigators to study novel therapies to improve healing and flap revascularization.