For patients undergoing orthopedic lower limb surgeries, postoperative anesthesia-related pulmonary complications and confusion can interfere with recovery, timely discharge, and participation in early physical therapy. For these reasons, the use of regional anesthesia, including either central blocks or multiple peripheral nerve blocks has increased. These blocks also ensure adequate intraoperative and postoperative analgesia and anesthesia. The elderly form the majority of patients who undergo orthopedic lower limb surgery. The presence of cardiac, endocrine, renal, cerebral and respiratory diseases in these patients increases the perioperative and postoperative morbidity. The aim of the study was to compare between both US guided combined lumbo-sacral plexus block and continuous spinal anesthesia in elderly patients undergoing orthopedic lower limb surgeries regarding hemodynamic stability, blood loss and postoperative analgesia effect. The present study included 56 patients undergoing orthopedic lower limb surgeries aged ( ≥ 65 years) of both sex in Zagazig university hospital. Patients distributed into two groups (28 patients in each group). US-LSPB group done by shamrock technique for lumbar pleuxes block receiving bupivacaine (0.25%) in volume of 30ml & 25µg fentanyl and parasacral parallel shift technique for sacral pleuxes block receiving bupivacaine (0.25%) in volume of 20 ml & 25µg fentanyl. CSA group done by inserting catheter in intrathecal space and injecting hyperbaric bupivacaine (0.5%) 1 ml (5mg) & 25µg fentanyl with top up doses after 2 segment regression 0.5 ml hyperbaric bupivacaine (0.5%) and at the end of the surgery 25µg fentanyl was administrated through the catheter for postoperative analgesia. Comparison was made regarding demographic data, duration of the technique, onset & duration of sensory and motor block, hemodynamics, amount of intraoperative blood loss, patient & surgeon satisfaction, failure rate, postoperative analgesia, 1st time & total dose of rescue analgesia and complication rate. The results of the statistical analysis of the data obtained showed: that as regards duration of the technique there was significant difference between the two groups as patients in US-LSPB group showed longer duration than CSA group. And as regard onset & duration of motor and sensory block, the study revealed significant difference among two groups as patients in US-LSPB group showed slower onset and longer duration than CSA group. As regard hemodynamics, there was no statistically significant difference between the two groups regarding Heart rate changes at most intervals except at 90 minutes HR was significant higher in CSA group than US-LSPB group , there was no statistically significant difference between the two groups regarding MAP changes at most intervals except at 20 minutes MAP was significantly lower in CSA group than US-LSPB group, there was no statistically significant difference between the studied groups regarding SPO2 changes at different intervals. As regard amount of intraoperative blood loss, there was statistically highly significant difference between the studied groups regarding as it was higher in US-LSPB group 349.28 ml than CSA group 253.21 ml. And as regard patient & surgeons satisfaction, there was statistically significant differences between the studied groups where CSA group patients and surgeons were satisfied more than US-LSPB group patients and surgeons. As regard failure rate, the study revealed 6 patients in US-LSPB group ( insufficient block) and 3 patients in CSA group (inability to insert the catheter) failed. As regard postoperative analgesia, there was significant difference among the studied groups as patients in US-LSPB group revealed prolonged analgesia 5.02±0.96 hr than CSA group 2.43±0.77 hr. Also, there was satistically significant difference between the studied group regarding total dose of rescue analgesia in 1st 24 hour postoperative (Nalbuphine/mg) as patients in CSA group require higher dose (19.15±1.25) than patients in US-LSPB group (10.64±1.52). As regard postoperative complications, there was no statistically significant difference between the studied groups.