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Fused real-time ultrasound and magnetic resonance imaging (MRI) may be used to improve the accuracy of advanced image guided procedures. However, its use in regional anesthesia is practically nonexistent. In this randomized controlled crossover trial, we aim to explore effectiveness, procedure-related outcomes, injectate spread analyzed by MRI, and safety of ultrasound/MRI fusion versus ultrasound guided Suprasacral Parallel Shift (SSPS) technique for lumbosacral plexus blockade. Twenty-six healthy subjects aged 21–36 years received two SSPS blocks (20 mL 2% lidocaine-epinephrine [1 : 200,000] added 1 mL diluted contrast) guided by ultrasound/MRI fusion versus ultrasound. Number (proportion) of subjects with motor blockade of the femoral and obturator nerves and the lumbosacral trunk was equal (ultrasound/MRI, 23/26 [88%]; ultrasound, 23/26 [88%];p=1.00). Median (interquartile range) preparation and procedure times (s) were longer for the ultrasound/MRI fusion guided technique (686 [552–1023] versus 196 [167–228],p<0.001and 333 [254–439] versus 216 [176–294],p=0.001). Both techniques produced perineural spread and corresponding sensory analgesia from L2 to S1. Epidural spread and lidocaine pharmacokinetics were similar. Different compartmentalized patterns of injectate spread were observed. Ultrasound/MRI fusion guided SSPS was equally effective and safe but required prolonged time, compared to ultrasound guided SSPS. This trial is registered with EudraCT (2013-004013-41) and ClinicalTrials.gov (NCT02593370).

Background and Objectives: The precise location of the adductor canal remains controversial among anesthesiologists. In numerous studies of the analgesic effect of the so-called adductor canal block for total knee arthroplasty, the needle insertion point has been the midpoint of the thigh, determined as the midpoint between the anterior superior iliac spine and base of patella. "Adductor canal block"may be a misnomer for an approach that is actually an injection into the femoral triangle, a "femoral triangle block." This block probably has a different analgesic effect compared with an injection into the adductor canal.We sought to determine the exact location of the adductor canal using ultrasound and relate it to the midpoint of the thigh. Methods: Twenty-two volunteers were examined using ultrasound. The proximal end of the adductor canalwas identified where the medial border of the sartorius muscle intersects the medial border of the adductor longus muscle. The distal end of the adductor canal is the adductor hiatus, which was also visualized ultrasonographically. Results: The mean distance from the anterior superior iliac spine to the midpoint of the thigh was 22.9 cm (range, 20.3-24.9 cm). The mean distance from the anterior superior iliac spine to the proximal end of the adductor canal was 27.4 cm (range, 24.0-31.4 cm). Consequently, the mean distance from the midpoint of the thigh to the proximal end of the adductor canal was 4.6 cm (range, 2.3-7.0 cm). Conclusions: In all volunteers, the midpoint of the thigh was proximal to the beginning of the adductor canal, suggesting that an injection performed at this level is in fact a femoral triangle block.