Fig. 1.

Etiopathogenesis and postural change in adult spinal deformity. The degenerative process is initiated by load-bearing structures, including intervertebral discs and facet joints, and leads to postural changes. Abnormal bone remodeling cycles then affect paraspinal muscle quality, which aggravates spinal deformity. To maintain an upright posture, compensatory mechanisms are driven by loss of lordosis (decreased lumbar lordosis) and lead sequentially to low thoracic kyphosis, pelvic retroversion (increased pelvic tilt), knee flexion, and head and neck extension. These changes present as sagittal and spinopelvic imbalance (increased pelvic incidence minus lumbar lordosis mismatch and increased sagittal vertical axis) and contribute to poor health-related quality of life.