Association Between Degeneration of the Paraspinal Muscles and Nerve Root Compression in Lumbar Disc Herniation Patients Who Underwent Percutaneous Endoscopic Lumbar Discectomy

OBJECTIVE: While paraspinal muscle degeneration is closely linked to lumbar disc herniation (LDH), the relationship between radicular compression and paraspinal muscle degeneration remains controversial, and evidence regarding the effect of percutaneous endoscopic lumbar discectomy (PELD) on paraspinal muscle degeneration is limited. This study aimed to investigate the correlation between radicular compression and paraspinal muscle degeneration in LDH patients and to evaluate postoperative changes in paraspinal muscles following PELD. METHODS: A total of 185 patients with single-level L4-5 LDH complicated by unilateral nerve root compression who underwent PELD between January 2020 and January 2023 were retrospectively enrolled. Preoperative and postoperative L3-S1 T2-weighted MRI scans were acquired. Paraspinal muscle cross-sectional area (CSA) and fat infiltration (FI) were measured using ImageJ, and total CSA (TCSA) and functional CSA (FCSA) were calculated. Paired-samples t-tests for bilateral paraspinal muscle differences and pre- to postoperative parameter changes; Spearman correlation analysis for continuous variable correlations; independent-samples t-tests, chi-square tests or one-way ANOVA for intergroup comparisons. A two-tailed p < 0.05 was considered statistically significant. RESULTS: Of this cohort, 108 patients completed the 3-month postoperative follow-up, and 29 underwent longitudinal follow-up for over 12 months. At the L3-5 level, the CSA on the compression side was lower than that on the non-compression side. At the L5-S1 level, the CSA and FI on the compressed side were greater than those on the opposite side. After PELD surgery, the CSA of the paraspinal muscles significantly increased, and the FI significantly decreased on the compression side. The duration of lower extremity pain (LEP) was positively correlated with the FI of the multifidus (MF) and erector spinae (ES) at all three levels; moreover, on the compression side, the correlation coefficient increased with decreasing segment length. CONCLUSION: Degeneration of the multifidus and erector spinae muscles, especially the FI, is significantly associated with nerve root compression. Moreover, the duration of LEP is meaningful for assessing paraspinal muscle degeneration. Paraspinal muscle degeneration significantly improved after PELD, and longer preoperative LEP duration was associated with greater improvement in FI.