The third character is wrong (they do look similar)
(肛精铢股 -> 肛精鉄股)
It's almost pronounced the same way as "鋼筋鐵骨"(traditional characters) or "钢筋铁骨"(simplified characters)
which literally means "tendons of steel, bones of iron"
It's used to describe someone who has a strong/sturdy body
The...