ABSTRACT
As the elderly population increases, the number of adult spinal deformity patients is also increasing. Unlike the main symptom of adolescent deformity is deformity itself, the symptoms of adult spinal deformity are various such as back pain and radiating pain to the extremities, which are associated with degenerative change. Deformities also show various combinations of scoliosis, kyphosis, coronal and sagittal imbalances. Various symptoms and complex deformities as well as old ages make treatment of the adult spinal deformity difficult. Radiographs of the spinal deformity should include spine and pelvis and hip joints in long films. Spinal deformity is influenced by regional curve, rotation of pelvis, and positions of hip and knee joints. The pelvis is a key structure in regulating spinal balances. Pelvic incidence, pelvic tilt and sacral slope are the most widely used spino-pelvic parameters. Pelvic incidence is fixed constant, which is unchanged when bone growth is complete. Pelvic incidence has a positive correlation with lumbar lordosis, and serves as a reference value in determining how much correction of lumbar lordosis is required in patients with sagittal imbalance. More correction of lumbar lordosis is required in patients with higher pelvic incidence. In order to maintain spinal balance, the combination of thoracic kyphosis, lumbar lordosis, and pelvic tilt should be harmonized. In particular, the match of pelvic incidence and lumbar lordosis is important to maintaining a balanced spine.