Evaluation of Sensory Loss Obtained by Circum-Psoas Blocks in Patients Undergoing Total Hip Replacement: A Descriptive Pilot Study.

Purpose: The transversalis fascia (TF) encases the quadratus lumborum and psoas major (PM) muscles, respectively, after they split caudalward approximately at the level of the iliac crest. The branches of the lumbar plexus variably exit medially and laterally from the TF-encased PM muscle. We hypothesized that the local anesthetic (LA) injections around the anterolateral edge of PM at the supra-iliac level and into the retro-psoas compartment at the L5/S1 level, which termed as the circum-psoas blocks, could block the lumbar plexus branches. Therefore, here we evaluated the sensory loss caused by the circum-psoas blocks. Methods: A total of 26 patients scheduled for total hip replacement were recruited for the study. After anesthesia induction, the ultrasound-guided circum-psoas blocks were performed in the lateral position with the affected side upward, in which the 0.3% ropivacaine was injected posterior to the TF and around the anterolateral edge of PM muscle at the supra-iliac level (25 mL), and into the retro-psoas compartment at the L5/S1 level (20 mL). The sensory block dermatomes and the muscle strength of quadriceps femoris were evaluated at 2 h or 6 h after surgery, respectively. The postoperative pain scores and opioid consumption were recorded. Results: The median (interquartile range) highest and lowest dermatomes of sensory block were T10 (T9-T10) and S2 (S2-S2), respectively. The muscle strength of the quadriceps femoris evaluated at 6 h post-surgery was 4 (4-5) points. Total postoperative equivalent milligrams of oral morphine consumption in the first 24 h were 11.3 ± 3.6 mg. Conclusion: The circum-psoas blocks may be a promising approach for postoperative analgesia of hip surgery, since they provide a dermatomal coverage of sensory block from T8-11 to S1-3. Clinical Trial Registration: Chinese Clinical Trial Registry, clinical trial number ChiCTR2100051247.