Moderate Degeneration of the Lumbar Paravertebral Muscle in Patients With Dynamic Sagittal Imbalance,A retrospective cohort study

Abstract

Study Design: A retrospective cohort study.Background: Sagittal imbalance of the spine is a comprehensive concept and can be caused by many causes. Paravertebral muscle is an important factor in the stabilization of spine.The active subsystem formed by the muscles around the lumbar spine plays an important role in maintaining lumbar spine stability and extendding the spine . Clinically, we found that some patients showed spinal sagittal balance when they were energetic, but hunched or leaning forward after a period of walking or working.Standing full-spine lateral digital radiographs shows increased sagittal vertical axis (SVA)dynamically.We call this symptoms a dynamic sagittal imbalance（DSI. However, the sagittal sequence, paravertebral muscle changes, and the correlation between them in DSI patients have not been clearly explored. The purpose of this study was to investigate the changes of spinal-pelvic parameters; paravertebral muscle; and the relationship between the two in DSI patients .Method: The study group comprised 31 patients with DSI and 42 control patients.All subjects underwent radiologic whole spine X-ray examination and lumbar MRI( Magnetic Resonance Imaging) scanning. Spinal-pelvic parameters such as sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI) was measured. The cross-sectional areas （CSA）of the erector spinae (ES),multifidus (MF), and vertebral body were measured at L2/L3 and L4/L5. The fat infiltration (FI) and relative cross-sectional area (RCSA)of muscle of these muscles were quantitatively measured though Image J. All subjects were examined for bone mineral density and pulmonary function to test the overall skeletal muscle capacity.Result: Compared with the control group,the DSI group had a smaller lumbar lordosis，more severe fat infiltration and lower Relative functional cross-sectional area(RFCSA) of paravertebral muscle ES(erector spinae)&MF(multifidus). There was no correlation between muscle degeneration and spinal-pelvic parameters in DSI patients.In addition,There were no statistically significant differences in bone mineral density test and pulmonary function test which reflected systemic skeletal muscle capacity of whole body.Conclusion: DSI，along with moderate degeneration of the paravertebral muscles of the lumbar spine.Usually accompanied by a reduction in lumbar lordosis. DSI is regards as the pre-state of PDSI.