The main objective of the trial is to complete a double-blinded randomized controlled trial with crossover design of a one-injection nerve block of the lower part of the lumbar plexus and the upper part of the sacral plexus (Suprasacral Parallel Shift, SSPS) to achieve analgesia of the femoral nerve, the obturator nerve, the lumbosacral trunk, and spinal nerve L1 with SSPS guided by ultrasound/MR image fusion vs. SSPS guided by ultrasound by estimating sensory block of in healthy volunteers by estimating the sensory block of dermatomes of the terminal nerves in healthy volunteers.