Spontaneous Lumbar Curve Coronal Correction After Selective Anterior or Posterior Thoracic Fusion in Adolescent Idiopathic Scoliosis

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Abstract
Retrospective review of anterior and posterior fusions for treatment of adolescent idiopathic thoracic scoliosis. To evaluate both the instrumented thoracic and the spontaneous lumbar curve corrections after treatment of the primary thoracic scoliosis by either anterior or posterior fusion. Recent reports of thoracic scoliosis fusions have concentrated on the thoracic correction obtained by posterior segmental instrumentation systems. Coronal decompensation occurring because of curve progression with imbalance of the unfused lumbar spine has also been investigated. No report comparing spontaneous lumbar curve response after selective anterior versus posterior thoracic scoliosis fusions are available. One hundred twenty-three cases of primary thoracic–compensatory lumbar adolescent idiopathic scoliosis were treated by selective thoracic instrumentation and fusion with either an anterior (n = 70) or posterior (n = 53) single approach. Thoracic and lumbar Cobb measurements and lumbar apical translation parameters were assessed before surgery, 1 week after surgery, and 2 years after surgery on upright coronal radiographs. All patients had a minimum 2-year follow-up. At 2-year follow-up, the percentage of thoracic curve correction was superior for the anterior (58%) versus the posterior (38%) group (P < 0.05), whereas the spontaneous lumbar curve correction was also superior for the anterior (56%) group versus the posterior (37%) group for all curve types investigated (P < 0.05). Both treatment groups consistently improved lumbar apical positioning after the thoracic fusion procedure. Spontaneous lumbar curve correction occurs consistently after both selective anterior and posterior thoracic fusion implying intrinsic ability of the lumbar spine to follow thoracic spine correction. In the current study, using multisegmented hook–rod systems posteriorly with intentional limitation of posterior thoracic correction to avoid decompensation, instrumented thoracic and spontaneous lumbar curve correction was statistically better after anterior thoracic instrumentation and fusion, with the results most dramatic for lumbar curve Type C (true King II curves).