Chronological flap volume and distribution changes after reconstruction of total maxillectomy defect using a rectus abdominis myocutaneous flap

Background/Purpose After total or subtotal maxillectomy, reconstruction using a free rectus abdominis myocutaneous (RAMC) flap is a fundamental and useful option. The purpose of the present study was to clarify the degree of flap volume change and volume distribution change with time after total or subtotal maxillectomy and free RAMC flap reconstruction and to examine the factors affecting the results. Methods A total of 20 patients who underwent total or subtotal maxillectomy with free RAMC flap reconstruction were examined, and the flap volume change rate (volume at final evaluation [POD 181–360] / volume at initial evaluation [POD 5–30]) was investigated using the results of imaging tests. Moreover, the flap was divided into four blocks (A–D) in the cranio-caudal direction, and the volume change of each block was individually analyzed. Results The overall volume change rate of fat/muscle/total was 0.84 ± 0.21/0.36 ± 0.08/0.67 ± 0.15, at the mean follow-up period of 309±35 days after the operation. The multiple regression analysis revealed that weight loss (for fat), postoperative RT (for fat and muscle), and young age (for muscle) were independently associated with flap volume loss. The results also indicated that the fat volume was stable, whereas the muscle volume decreased to <40% over time, assuming there were no influencing factors. Regarding flap volume distribution change, the fat volume tended to gather toward the central-cranial direction, while the muscle volume gathered toward the cranial direction, and total flap volume gathered toward the central direction.