Introduction and Aims: Thoracolumbar adolescent idiopathic scoliosis may be treated surgically with anterior or posterior spinal instrumentation, with little evidence in the literature to suggest superiority of either technique. The purpose of this study is to compare anterior vs. posterior instrumentation in a well-defined population of patients with thoracolumbar adolescent idiopathic scoliosis.

Method: Medical records and radiographs of all patients undergoing spinal instrumentation for the treatment of adolescent idiopathic scoliosis with primary thoraco-lumbar curves, defined as curve apices between T10 and L2, between 1993 and 2001 were reviewed. Fusions extending above T7 were excluded from the study. The study group consists of 12 patients treated with anterior spinal instrumentation and 16 with posterior instrumentation. Various radiographic and outcome measures were compared between groups.

Results: The anterior group had 75% correction of the primary Cobb angle compared to 56% in the posterior group (P = 0.019). An average of 3.8 vertebral levels in the anterior and 6.7 in the posterior procedures were fused (P < 0.001). Less blood loss was observed in the anterior group (P = 0.007), with fewer transfusions as well (P < 0.001). The anterior group produced more lumbar lordosis (p=0.03) than the posterior group. In the anterior group there was a 0% rate of revision surgery (0/12), whereas the posterior group had a 31% revision rate (5/16), which was a significant difference (p=0.047).

This study comparing anterior versus posterior instrumentation is unique in that it is limited to thoracolumbar curves. While earlier series of anterior instrumentation revealed high rates of hardware failure and pseudoarthrosis, this series found no instance of either in the anterior group. In addition, concern over anterior compression causing kyphosis at the thoracolumbar junction proved unwarranted, and in fact the anterior instrumented group had improved lumbar lordosis compared to the posterior.

Conclusions: In this series limited to thoracolumbar idiopathic scoliosis surgery, anterior instrumentation had a significantly improved Cobb angle, less levels fused, more lumbar lordosis, and less transfusions when compared to posterior instrumentation. Patients undergoing anterior instrumentation had a lower rate of revision surgery compared to those with posterior instrumentation.