Comparing Ultrasound‐Guided and Unguided Lumbar Injection of Psoas Major Muscle for Clinical Management of Hip Flexor Spasticity
Authors: Duong Allen , Sharma Satyendra , Agur Anne 
Published: June 2021

ObjectiveHip flexor spasticity, resulting from brain injury or neurological disorders, can result in decreases in range of motion, leading to joint immobility. Spasticity can be managed with Botulinum Toxin A (BT‐A) injections, which decreases muscle tone, thereby increasing range of motion. Psoas major (PM) plays a significant role in hip flexor spasticity and is targeted inferior to the inguinal ligament. However, at this location, only the illiacus muscle is injected as PM is tendinous. To target the muscle belly of PM, a lumbar approach must be used. This approach has been described in the literature, yet has been rarely used for BT‐A injection due to the perceived risk to vascular structures (abdominal aorta and inferior vena cava (IVC)), lumbar plexus, and/or kidney. The lumbar approach has been performed with and without image guidance, yet potential injury to adjacent structures has not been assessed. The purpose of this cadaveric study was to compare ultrasound (US) guided and non‐guided PM lumbar injection to assess the injectate spread, location and proximity to adjacent structures.Methods8 lightly embalmed specimens were injected bilaterally with 2ml of toluidine blue; on one side using US guidance, and on the other no guidance (unguided). The abdominal contents were removed to expose the structures of the posterior abdominal wall. Extramuscular dye spread was noted. The following were digitized (Microscribe® MLX Digitizer) and reconstructed into 3D models (Autodesk® Maya®): quadratus lumborum, iliacus, PM, great vessels, and vertebral column. The volume of PM was serially dissected at the fiber bundle level to allow digitization of the dye spread. The extent, location of dye spread was documented relative to the great vessels. Descriptive statistics were used to characterize and compare the US‐guided and unguided approaches.ResultsThe dye was found in PM in all US‐guided specimens. No intramuscular dye spread was found in 4/8 specimens using the unguided approach. The US‐guided specimens had a mean area of dye spread of 24.4 ± 2.8 cm2 whereas the unguided specimens had a mean area of 54.2 ± 28.0 cm2. The dye (guided approach) was located consistently between the superior margin of vertebral body of L3 and inferior margin of vertebral body of L4, whereas the unguided approach had its dye localized between vertebral bodies of L4 and L5. The mean distance of dye spread from: 1) the aorta was 3.19 ± 1.24cm (US‐guided approach) and 1.40 ± 0.0002cm (unguided approach), 2) the IVC was 1.81 ± 0.38cm (US‐guided approach) and 2.79 ± 0.11cm (unguided approach). There was no dye spread to the kidney using either US‐guided or unguided approaches, however the lumbar plexus was stained in 2/8 specimens using the unguided approach.ConclusionsThe US‐guided lumbar approach was found to target PM more consistently, with greater distance from the aorta than the unguided approach. This cadaveric study demonstrates that the US‐guided approach may have distinct advantages over the unguided approach, however this needs to be further investigated in the clinic.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.