RESUMO
INTRODUCTION: The impact of fat grafting on the viscoelasticity of irradiated tissues is poorly defined. We investigate the effect of subcutaneous fat grafting on postmastectomy tissue expansion in patients undergoing delayed breast reconstruction. We quantify observed viscoelastic and trophic changes of the skin envelope. We hypothesize that fat grafting changes the trophic and viscoelastic properties of the breast soft tissue envelope. METHODS: Postmastectomy defects delayed more than 2 years and reconstructed with subpectoral tissue expanders were prospectively studied. Control (no irradiation, no fat grafting, n = 7), fat grafted (no irradiation, fat grafting n = 8), and irradiated plus fat grafting (irradiation, fat grafting, n = 9) groups were included. Hydrostatic pressures of the tissue expanders were measured before and immediately after expansion, and again postexpansion day 1. Pressure changes calculated as "postexpansion-relaxation interval": difference between maximal pressure at each expansion and the minimal pressure before the next expansion session. Differences were analyzed between groups. RESULTS: Hydrostatic pressure plots reflect the soft tissue ability to accommodate sequential expansion. Fat grafted breasts demonstrated a statistically significant increased postexpansion-relaxation interval versus the nongrafted control group (P < 0.0001). Irradiated plus fat grafting breasts achieve similar postexpansion relaxation interval to the control group (P = 0.597). These changes are observed at postoperative week 6. Viscoelastic changes impact the overall expansion time: the fat grafted group achieved total expansion 2 weeks earlier than the nongrafted control group (P = 0.019). The fat grafted, radiated group completed expansion in similar time interval as nongrafted control group. CONCLUSIONS: Observed viscoelastic changes impact the overall expansion time. Fat grafting in nonradiated mastectomy defects allows for shorter expansion period. Fat grating in radiated postmastectomy defects allows expansion durations equivalent to nonradiated, nonfat grafted control defects. There is a delayed effect of fat grafting observed at postoperative week 6.
