Use of the Posterior Lumbar Approach for Psoas Major Injection in Hip Flexor Spasticity

Area of Science:

• Medical Imaging
• Anatomy
• Neurology

Background:

• Hip flexor spasticity is often treated with botulinum neurotoxin injections targeting the iliopsoas muscle.
• A lumbar approach to the psoas major (PM) muscle has been described but is not widely used due to safety concerns.
• This study aimed to assess the safety and accuracy of ultrasound-guided (UG) PM injections via a lumbar approach.

Purpose of the Study:

• To evaluate the feasibility and accuracy of ultrasound-guided (UG) posterior lumbar injections into the psoas major (PM) muscle.
• To assess the intramuscular injectate spread and proximity to critical vascular structures.

Main Methods:

• Eight cadaveric specimens were injected with dye/saline into the PM using a UG posterior lumbar approach.
• Dye spread, vertebral levels, and distances to the abdominal aorta (AA) and inferior vena cava (IVC) were quantified.
• 3D modeling was used to visualize injectate distribution and proximity to adjacent organs.

Main Results:

• The mean area of dye spread was 24.4 cm², primarily between L2-L4 vertebral levels.
• Injectate remained intramuscular in all but one specimen, with mean distances of 3.2 cm to the AA and 1.8 cm to the IVC.
• No dye spread to adjacent organs was observed.

Conclusions:

• Ultrasound-guided posterior lumbar PM injections are accurate and safe, with minimal risk to surrounding structures.
• This technique may improve clinical outcomes for hip flexor spasticity when used alone or with anterior approaches.
• Further clinical investigation is warranted to confirm efficacy.