The objective of this study was to discuss the variables influencing alignment mechanisms of the spine, with particular consideration of post-surgical alignment in adolescent idiopathic scoliosis. The analysis is based on information currently available in the literature, and on the authors’ own experience, which includes surgical material from over 2200 cases of idiopathic scoliosis. Over 50% of cases of adolescent idiopathic scoliosis are decompensated before surgical treatment. Spinal alignment is most significantly influenced by the position of the pelvis. Surgical restoration of lumbar lordosis is more important than attempting to restore thoracic kyphosis in the sagittal plane. The sagittal profile has an essential impact on spinal alignment. The same curves in the coronal plane can have various 3-dimensional configurations. Clinical difficulties in the assessment of thoracic kyphosis and lumbar lordosis result from the fact that they undergo constant change with age. Thoracic hypokyphosis diagnosed before surgery is a very frequent symptom of curve progression. The presence of proximal (thoraco-thoracic) and distal (thoraco-lumbar) junctional kyphosis is very important for planning the scope of spondylodesis. The natural tendency of the spine for alignment (compensation) after surgery nowadays occurs more naturally by applying derotational forces through pedicle screws, compared to the distraction devices (eg, Harrington rod) used in the past.

Keywords: Spinal Fusion, Scoliosis - surgery, Orthopedic Procedures - methods, Adolescent, Spine - surgery