Here is disclosed a reusable pneumatic distraction device having a housing which encloses a first and a second gas reservoir which are configured to contain a quantity of high and low pressure gas, respectively. A valve member seals off an exhaust in the first gas reservoir, the valve member movable between a closed position sealing the exhaust and an open position. The device also includes a pneumatic drive for urging the valve towards its opened position. The pneumatic drive configured to apply a lower urging force followed by a larger urging force as the valve opens. The device is also provided with a lock pin releasably coupled to the valve for preventing the valve from moving towards its open position. Finally, the device includes a delay mechanism to delay the opening of the piston when the lock pin is released.