The utility model relates to a pedicle of vertebral arch of falling trapezoidal thread screw can prevent especially that the nail body spreading from increasing the the utility model relates to a pedicle of vertebral arch of falling trapezoidal thread screw of locking force, belongs to the medical instrument field. The utility model discloses constitute characterized by by the plug screw (1) and the U-shaped pedicle of vertebral arch nail body (2): plug screw (1) is inside to be hexagonal groove (3), and the apparatus of being convenient for is held and is got, and the outside has down trapezoidal thread (4), U-shaped pedicle of vertebral arch nail is personally experienced sth. Part of the body (2) inside trapezoidal thread (5), and the pin fin is arc (6), and pin fin position U-shaped groove (7) makes things convenient for putting into of connective bar, and the pin fin outside is similar to heavy groove (8) of type shape, follows closely external threaded (9), follows closely blade (10) of the afterbody of personally experiencing sth. Part of the body. Selecing earlier into nail point during the operation, preparing to follow closely and say, carry out the tapping, put into the U-shaped pedicle of vertebral arch nail body (2) and put into the connective bar, the position of will fracturing resets fixedly, and screw in plug screw (1) performs the operation fixedly and the postoperative is handled.