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) nap for autogenous tissue breast reconstructio n is to balance maximal flap perfusion against the sacrifice of abdomi nal-wall integrity. A surgical delay has been suggested as one very si mple fascia-sparing technique that simultaneously augments flap volume , but no randomized clinical studies have been performed to prove whet her there is and benefit whatsoever following such a maneuver. Because large groups of nearly identical subjects may be more readily availab le for comparison in an animal model, the rat TRAM nap provides an ine xpensive method to further investigate the delay phenomenon in this se tting. Staged procedures were performed in 15 Sprague-Dawley rats init ially causing a delay by division of one or both dominant vessels (cra nial epigastric) supplying the rectus abdominis muscles. Either 2 or 4 weeks later, TRAM flaps were elevated based only on the subservient ( caudal epr gastric) pedicle. A control group of 7 rats with immediate formation of a TRAM nap had a mean survival of 46.3 +/- 15.37 percent of their original flap surface area. After a 2-week delay, viability w as 50.2 +/- 17.54 percent for ipsilateral and 39.4 +/- 7.57 percent fo r naps with prior bilateral dominant pedicle division. Neither was sig nificantly different from control (P = 0.68 and 0.38, respectively). H owever, the ipsilateral 4-week delayed group had 67.8 +/- 8.96 percent nap survival, which represented a significant enhancement when compar ed with the undelayed control TRAM naps (P < 0.02). Corresponding lead oxide microangiographs confirmed dilatation of ''choke'' vessels conn ecting the epigastric vessels at their watershed within the rectus abd ominis muscle, as well as collaterals circumventing the site of surgic al interruption to reestablish the influence of the dominant source pe dicle. This evidence proves that the delay phenomenon can be invoked t o augment survival of the rat TRAM flap. However, the optimal timing a nd extent of surgical interruption of collaterals necessary to achieve this objective even in the rat appear to be variable. Caution must th erefore be appreciated before extrapolating these data to human applic ations, particularly since the source vessels to the rat TRAM nap are in no way homologues to those of the human.