In group 1,the flaps were subjected to simple subcutaneous exclusion,the flaps in group 2 were expanded with a Foley catheter 6 ml in volume for 3 minutes,the flaps in group 3 were expand twice in the same way as group 2 at an interval of 3 minutes.

• 单纯分离组仅作皮下分离，1次扩张组和2次扩张组用Foley氏导管，以6ml的扩张量，分别扩张1次和2次，每次扩张时间3min。