Iatrogenic Flatback and Flatback Syndrome: Evaluation, Management, and Prevention.

Flatback syndrome can be a significant source of disability, affecting stance and gait, and resulting in significant pain. Although the historical instrumentation options for thoracolumbar fusion procedures have been commonly regarded as the etiology of iatrogenic flatback, inappropriate selection, or application of modern instrumentation can similarly produce flatback deformities. Patients initially compensate with increased lordosis at adjacent lumbar segments and reduction of thoracic kyphosis. As paraspinal musculature fatigues and discs degenerate, maintaining sagittal balance requires increasing pelvic retroversion and hip extension. Ultimately, disc degeneration at adjacent levels overcomes compensatory mechanisms, resulting in sagittal imbalance and worsening symptoms. Nonoperative management for sagittally imbalanced (sagittal vertical axis>5 cm) flatback syndrome is frequently unsuccessful. Despite significant complication rates, surgical management to recreate lumbar lordosis using interbody fusions and/or osteotomies can significantly improve quality of life.