Abstract / Summary
To characterize paraspinal muscle degeneration patterns across different stages of sagittal imbalance in adult spinal deformity (ASD) and explore associated factors to sagittal imbalance with pelvic compensation failure (SI-FPC). A total of 177 ASD patients were enrolled. Spinopelvic parameters were measured on X-ray. Paraspinal muscle endurance was assessed using the modified Ito test. Relative functional cross-sectional area (rFCSA) of paraspinal extensor muscles (PEM) and psoas major (PS) were measured on lumbar magnetic resonance imaging. Patients were categorized into four stages: 31 of sagittal balance (SB), 71 of compensated sagittal balance (CSB), 54 of decompensated sagittal imbalance (DSI), and 21 of SI-FPC. Paraspinal muscle endurance and PEM rFCSA progressively declined from SB to DSI ( P < 0.05), while PS rFCSA remained similar across groups ( P > 0.05). SI-FPC group showed the lowest Ito test time (11.81 ± 13.90s), significantly lower than that of SB and CSB (52.35 ± 58.94s, P < 0.001; 31.14 ± 38.60s, P < 0.05). Multivariate analysis identified the declining muscle endurance was associated with pelvic compensation failure ( P = 0.005). Receiver operating characteristic analysis determined a 23.5s cutoff as an exploratory threshold for identifying SI-FPC patients, with a sensitivity of 85.7%. Early reduction in paraspinal muscle endurance might be associated with SI-FPC in ASD. Targeted exercise might provide a novel clinical strategy for preventing this condition.