Quantitative assessments of paraspinal muscles and their relationship with lumbar extensor muscle function based on Dixon magnetic resonance imaging techniques

BackgroundThe dysfunction of paraspinal muscles is closely associated with degenerative spine disorders and the development of low-back pain. Currently, methods for evaluating paraspinal muscle function mainly focus on anatomical imaging and functional assessment.ObjectiveThis study aimed to explore the quantitative assessments of paraspinal muscles and their relationship with the strength and endurance of lumbar extensor muscles based on magnetic resonance imaging with Dixon techniques.MethodsFifty-four volunteers aged 45 years and older were recruited from our outpatient clinic. The participants underwent 3.0-T Dixon magnetic resonance imaging of the lumbar region. The Dixon sequence was used for measuring the cross-sectional area (CSA) and fat infiltration (FI) of paraspinal muscles (multifidus, erector spinae, and psoas major) at the L1-S1 level. The strength and endurance of lumbar extensor muscles were assessed using a standing external fixation testing bracket. Pearson or Spearman coefficients were used to evaluate the relationship between the quantitative assessment indicators of paraspinal muscle degeneration and the strength and endurance of lumbar extensor muscles (corrected for body height [BH] and weight [BW]).ResultsAt the L1-2 level, multifidus FI negatively correlated with extensor strength (ES), ES/BH, extensor endurance (EE), EE/BH, and EE/BW (r = -0.286, -0.269, -0.317, -0.306, -0.281; P < 0.05), and erector spinae FI negatively correlated with EE, EE/BH, and EE/BW (r = -0.315, -0.293, -0.268; P < 0.05). At the L2-3 level, multifidus FI negatively correlated with EE, EE/BH, and EE/BW (r = -0.358, -0.347, -0.327; P < 0.05), and erector spinae FI negatively correlated with EE, EE/BH, and EE/BW (r = -0.334, -0.310, -0.283; P < 0.05). At the L3-4 level, multifidus FI negatively correlated with EE (r = -0.271, P < 0.05), and psoas major CSA negatively correlated with ES/BW (r = -0.299, P < 0.05). At the L4-5 level, multifidus FI negatively correlated with EE and EE/BH (r = -0.286, -0.268; P < 0.05). At the L5-S1 level, multifidus FI negatively correlated with EE, EE/BH, and EE/BW (r = -0.418, -0.404, -0.377; P < 0.05).ConclusionThe FI of multifidus at the L5-S1 level may reflect the endurance level of extensor muscles to some extent. The FI of paraspinal muscles is relatively better than CSA in predicting the strength and endurance of lumbar extensor muscles. Proper extensor muscle functional exercises may slow down the process of paraspinal muscle FI to some extent.