A vertical midline scar is a 'high-risk' factor for maximum survival of the rat TRAM flap

The presence of any abdominal scar, in addition to obesity, a smoking history, and prior irradiation are considered the major known "risk factors" for predictable success or failure of the lower transverse rectus abdominis musculocutaneous (TRAM) flap. For many, a vertical midline scar has even been considered to be a relative contraindication. The possibility that the scar instead could effect some form of delay or by neovascularization permit reperfusion across the midline might negate this concern. The validity of this hypothesis was tested in 40 Sprague-Dawley (CD) rats using our standard rat TRAM flap model. Every rat initially had a vertical skin incision made from xiphoid to pubis. At a second stage, either immediately or after a delay of 1 week, 2 weeks, or 6 months, a superior-pedicled (dominant) or inferior-pedicled (nondominant) TRAM flap was raised, with five rats in each subgroup. For the inferior-pedicled group, the percentage of ipsilateral (muscle-pedicle half) flap survival approached 75% and had a trend toward greater survival with each increase in the time of delay, but any difference was not statistically significant (F= 0.653, P = 0.538). In the superior-pedicled group, the ipsilateral half of the flap always survived completely. In both groups, the contralateral or opposite side always underwent complete necrosis regardless of pedicle orientation or time constraints. The midline scar did not enhance even unilateral TRAM flap survival when compared with historic controls, and long-term transmidline reperfusion across the scar did not seem to occur. These findings corroborate the clinical observation that only a unilateral TRAM flap would be reliable in the presence of a vertical midline abdominal scar.