Evidence for the Efficacy of TRAM Flap Delay in a Rat Model

The dilemma in selecting a variant of the transverse rectus abdominis musculocutaneous (TRAM) flap for autogenous tissue breast reconstruction is to balance maximal flap perfusion against the sacrifice of abdominal-wall integrity. A surgical delay has been suggested as one very simple fascia-sparing technique that simultaneously augments flap volume, but no randomized clinical studies have been performed to prove whether there is any benefit whatsoever following such a maneuver. Because large groups of nearly identical subjects may be more readily available for comparison in an animal model, the rat TRAM flap provides an inexpensive method to further investigate the delay phenomenon in this setting. Staged procedures were performed in 15 Sprague-Dawley rats initially causing a delay by division of one or both dominant vessels (cranial epigastric) supplying the rectus abdominis muscles. Either 2 or 4 weeks later, TRAM flaps were elevated based only on the subservient (caudal epigastric) pedicle. A control group of 7 rats with immediate formation of a TRAM flap had a mean survival of 46.3 ± 15.37 percent of their original flap surface area. After a 2-week delay, viability was 50.2 ± 17.54 percent for ipsilateral and 39.4 ± 7.57 percent for flaps with prior bilateral dominant pedicle division. Neither was significantly different from control (p = 0.68 and 0.38, respectively). However, the ipsilateral 4-week delayed group had 67.8 ± 8.96 percent flap survival, which represented a significant enhancement when compared with the undelayed control TRAM flaps (p < 0.02). Corresponding lead oxide microangiographs confirmed dilatation of “choke” vessels connecting the epigastric vessels at their watershed within the rectus abdominis muscle, as well as collaterals circumventing the site of surgical interruption to reestablish the influence of the dominant source pedicle. This evidence proves that the delay phenomenon can be invoked to augment survival of the rat TRAM flap. However, the optimal timing and extent of surgical interruption of collaterals necessary to achieve this objective even in the rat appear to be variable. Caution must therefore be appreciated before extrapolating these data to human applications, particularly since the source vessels to the rat TRAM flap are in no way homologues to those of the human.