This study aimed to investigate the relationship between fatty infiltration in the lumbar paraspinal (multifidus and erector spinae) muscles, clinical characteristics, and treatment response after lumbar erector spinae plane block (ESPB) in patients with low back pain due to lumbar radiculopathy. A responder was defined as a patient with a numerical rating scale (NRS) decrease of ≥ 50% from baseline to one month after the procedure. The presence of fat infiltration in the lumbar paraspinal muscles was assessed, along with patient demographic and clinical characteristics.

Low back pain (LBP) is a common health problem that causes global disability. Lumbosacral radiculopathy (LR) is the most common cause of low back pain. Disc herniation is the most common cause of LR, in addition to spinal stenosis, foraminal stenosis, facet joint hypertrophy, and degenerative disease (1). Treatment options for lumbar disc herniation include conservative treatment, interventional pain management, and surgery. Lumbar erector spinae plane block (ESPB) is an interventional procedure for chronic axial and radicular low back pain which that is unresponsive to conservative treatment.

Lumbar paraspinal muscles play an important role in maintaining lumbar spine stability. Increased fat infiltration in the paraspinal muscles has been associated with high-intensity low back pain and poor functional status, and fat infiltration in the paraspinal muscles can be detected by lumbar magnetic resonance imaging. In this study, fatty infiltration in the bilateral lumbar multifidus muscles was evaluated at the L3 level using Goutallier classification.

The primary aim of this study was to investigate the potential relationship between the treatment outcome of lumbar ESPB and the degree of fatty infiltration in the paraspinal muscles in patients with chronic axial and/or radicular low back pain unresponsive to conservative treatments. The secondary aim was to identify other factors that may be associated with a successful response to lumbar ESPB and fatty infiltration of the paraspinal muscles.

Inclusion Criteria:

• lumbar radicular pain
• no response to conservative treatment for > 3 months
• MRI within 1 year prior to injection.

Exclusion Criteria:

• inadequate medical records with missing numerical rating scale (NRS) scores and MRI images
• patients lost to follow-up within one month after lumbar ESPB
• patients with a history of surgery for lumbar disc herniation
• patients with severe spinal and/or foraminal stenosis
• patients with extruded, sequestrated, or migrating hernias.

Male and female patients who underwent lumbar erector spinae plane block for low back pain due to lumbar radiculopathy