 The aim of this study is to find out the optimal technique to perform spinal anesthesia by residents in training. Thus the investigators will compare preprocedural ultrasound-guided paramedian technique using parasagittal oblique view vs preprocedural ultrasound-guided midline technique using transverse median view vs landmark-guided midline technique of spinal anesthesia in the elderly population. Our hypothesis is that both preprocedural US-guided techniques are superior to the conventional landmark-guided midline technique with regard to ease of performance defined as success rate at first attempt, number of puncture attempts, spinal procedure time, and patient satisfaction. 