PURPOSE:The aim of this study was to compare the lengths of proximally based and distally based gluteus maximus flaps created as for anal sphincter reconstruction in soft human cadavers.METHODS:Twelve soft cadavers were used in this prospective, randomized, controlled study. In each cadaver, a proximally based flap of the gluteus maximus muscle was performed on one side and a distally based flap on the other. All flaps were carefully dissected with neurovascular preservation by one surgeon. After the dissected flap was placed across the anus, the length of the flap that projected beyond the anus was measured. The differences between such lengths of both types of flaps were assessed by pairedt‐test.RESULTS:The average lengths of the parts that projected beyond the anus for proximally based and distally based flaps were 8.08 and 4.50 (standard deviation, 0.51 and 0.79) cm, respectively. The average difference was 3.58 (standard deviation, 0.51) cm, which was statistically significant (P< 0.001).CONCLUSION:Results showed that proximally based flaps were significantly longer than distally based flaps and that transposition and wrapping around the anus with proximally based flaps were always easily performed without tension. These findings support the use of unilateral proximally based gluteus maximus flaps instead of unilateral or bilateral distally based flaps in patients with anal incontinence. The location of the neurovascular pedicle of the gluteus maximus was consistent at 1 cm superior and lateral to ischial tuberosity. Knowledge of this landmark allows quick and safe dissection of the gluteus maximus flap.