Traditionally, spinal/epidural combined anesthesia has been performed by palpation of the landmark like Tuffier's line. There are some studies that using ultrasound improves the success rate to regional anesthesia. There are two methods of using ultrasonography, 'Real-time scan' and 'Pre-procedure scan'. Direct comparison of these two methods is not yet studied. So investigators will compare the success rate, the consumed time, the number of needle passing, the depth and angle of the needle, the anesthetic effect, complications, pain and patient's satisfaction.
The investigators will compare the success rate, the consumed time, the number of needle passing, the depth and angle of the needle, the anesthetic effect, complications, pain and patient's satisfaction between 'Real-time scan' and 'Pre-procedure scan', when we performing spinal/epidural combined anesthesia.