butt joint

例句：

1. 1. The doctor performed a butt joint replacement surgery on her.
   医生给她做了臀部连接处的置换手术。
2. 2.She sat down and rested her feet on the butt joint of the chair.
   她坐下来，把脚放在椅子的臀部连接处。
3. 3. After the operation, she was in a lot of pain at the butt joint.
   手术后，她在臀部连接处感到非常疼痛。