Ultrasound-guided measurement of cross-sectional area of dural sac to titrate the dosage of local anaesthetic in geriatric orthopaedic surgery under spinal anaesthesia: A prospective randomised study. - Kaur, Kiranpreet; Bhatia, Vaishali; Vashishth, Sumedha; Kumar, Prashant; Singh, Roop; Singh, Navdeep (Indian Journal of Anaesthesia, 2026)