A study investigated the ED50 and ED95 of hypobaric ropivacaine under unilateral spinal anesthesia in elderly patients undergoing hip surgery.[1][2] A concentration of 0.4% hypobaric ropivacaine was used.[1][2] The ED50 was 11.13 mg (95% CI: 10.85–11.42 mg) and the ED95 was 10.30 mg (95% CI: 9.04–10.65 mg).[1][2][3] The dose was adjusted by 0.5 mg based on the Bromage score in the leg without surgery; the study ended after seven pairs of positive-negative results.[1][2] Successful cases did not have motor block in the leg without surgery.[1][2] Unilateral spinal anesthesia limits the blockade to the operative side, which causes fewer physiological disturbances, more stable hemodynamics, and fewer complications.[1][2][3] The results were calculated by probit regression analysis.[1][2]