Shear wave elastography assessment of lumbar multifidus muscle elasticity and its correlation with clinical function in patients with lumbar disc herniation

Background Lumbar disc herniation (LDH) is a common degenerative spinal disease causing low back and leg pain, and dysfunction of the lumbar multifidus muscle is closely associated with its pathogenesis. Current research primarily focuses on muscle strength and morphological assessments, with limited studies quantifying the elastic properties of the lumbar multifidus muscle and their correlation with clinical symptoms and function. Objective To investigate the characteristics of lumbar multifidus muscle elasticity in LDH patients using shear wave elastography (SWE) and analyze its correlation with pain intensity, functional impairment, and LDH classification, thereby providing a basis for clinical evaluation and precision rehabilitation. Methods Thirty-two clinically diagnosed LDH patients (LDH group) and 33 healthy volunteers without low back pain (control group) were enrolled. SWE was used to measure the elastic modulus of the lumbar multifidus muscle in both resting and contracted states. Pain intensity was assessed using the Visual Analog Scale (VAS), lumbar function was evaluated with the Oswestry Disability Index (ODI), and the Macnab classification was obtained from imaging. Differences in the elastic modulus between the two groups were compared, and correlations between the elastic modulus and VAS score, ODI score, and Macnab classification were analyzed in the LDH group. Results Resting-state lumbar multifidus muscle thickness was significantly lower in the LDH group than in the control group (1.03 ± 0.28 cm vs. 1.16 ± 0.23 cm, t = 2.047, P = 0.045), as was contracted-state thickness (1.42 ± 0.39 cm vs. 1.62 ± 0.29 cm, t = 2.442, P = 0.017); and resting-state elastic modulus was markedly higher in the LDH group (3.24 ± 0.65 kPa vs. 2.96 ± 0.60 kPa, z = 1.327, P = 0.016), but with no significant intergroup difference in contracted-state elastic modulus (5.00 ± 1.41 kPa vs. 5.78 ± 2.21 kPa, z = 1.327, P = 0.185). In the LDH group, resting-state elastic modulus was moderately positively correlated with VAS scores (r = 0.746, P < 0.001), weakly positively correlated with ODI scores (r = 0.535, P < 0.001), and uncorrelated with Macnab classification (r=-0.041, P > 0.05). Conclusions LDH patients exhibit characteristic morphological and elastic changes in the lumbar multifidus muscle, namely muscle atrophy and elevated resting-state stiffness; this resting-state elastic modulus is closely correlated with pain severity and lumbar dysfunction, but unassociated with the Macnab imaging classification of disc herniation. Shear wave elastography (SWE) can quantitatively assess lumbar multifidus muscle elasticity, providing novel objective evidence for the clinical evaluation of LDH and serving as an objective tool for its precision rehabilitation.