Restoration of Thoracic Kyphosis After Operative Treatment of Adolescent Idiopathic Scoliosis

STUDY DESIGN Multicenter analysis of 3 groups of patients who underwent surgical treatment for adolescent idiopathic scoliosis (AIS). OBJECTIVE.: To evaluate 3 surgical approaches to determine the modality that has the greatest influence on improving thoracic kyphosis. SUMMARY OF BACKGROUND DATA AIS is characterized by thoracic hypokyphosis which may be restored to normal to varying degrees with surgery. METHODS A multicenter retrospective AIS surgical database was reviewed. Patients with only a structural main thoracic curve (Lenke 1, 2, or 3), and instrumentation of only the main thoracic curve were included. Lateral radiographs were analyzed to determine sagittal plane measurements before surgery, after surgery at 6 to 8 weeks, 1 year, and 2 years. The 3 groups were compared and statistical significance was defined as P < 0.05. RESULTS Three groups were analyzed: (1) ASF group (n = 135), Anterior spinal fusion and instrumentation, (2) PSF-Hybrid group (n = 86), PSF with proximal hooks, +/- apical wires and distal pedicle screws, and 3) PSF-Hooks group (n = 132), PSF with only hooks. All groups had similar preoperative coronal main thoracic curve magnitudes (ASF: 50.6 degrees , PSF-Hybrid: 49.1 degrees , PSF-Hooks: 52.0 degrees ) and thoracic kyphosis (ASF: 23.7 degrees , PSF-Hybrid: 19.3 degrees , PSF-Hooks: 21.9 degrees ). After surgery, the T5-T12 kyphosis was greater in the ASF group (25.1 degrees ) compared with PSF-Hooks (19.0 degrees ) and PSF-Hybrid (18.5 degrees (P < 0.05). At 1 year, thoracic kyphosis (T5-T12) remained greater in the ASF group (28.8 degrees ) compared with PSF-Hooks (22.6 degrees ) and PSF-Hybrid (20.2 degrees ) (P < 0.05), and was also greater at 2 years (29.9 degrees vs. 23.8.8 degrees and 19.7 degrees ) (P < 0.05). Kyphosis at the thoracolumbar junction was not seen in the PSF-Hybrid group. Lumbar lordosis increased only in the ASF group in response to the increase in thoracic kyphosis. CONCLUSION ASFI is the best method to restore thoracic kyphosis when compared with posterior approaches using only hooks or a hybrid construct in the treatment of thoracic adolescent idiopathic scoliosis.