Spinal Sagittal Plane Deformities: Etiology, Evaluation, and Management

An aging population and an increasing number of spinal surgical procedures being performed have led to an increased number of patients presenting with spinal deformities and sagittal imbalance. Although few spine surgeons perform surgery on this patient population, most will encounter this problem in their practice. Individual spinal segments alignment is important to the overall sagittal balance. It is important to understand how these segments contribute to the global sagittal balance. Normal sagittal balance implies that the head is centered over the pelvis. When the individual is pitched forward, this is said to be a positive sagittal balance. The classic etiologies for sagittal imbalance include conditions such as ankylosing spondylitis, and Harrington distraction instrumentation. Other traditional etiologies include Zeilke and Dwyer anterior instrumentation. However, nowadays we are seeing other etiologies more frequently, including postlaminectomy deformities and iatrogenic postfusion kyphosis. Pseudoarthrosis and breakdown or fractures above or below long spinal fusions have become more common etiologies. Indications for spinal osteotomies include fixed spinal global sagittal imbalance, especially if associated with pain and disability. Surgical approaches vary depending on the nature and the etiology of the deformity, its location and the presence or absence of solid fusion in the area of intended correction. It is very important to plan the corrective procedure so that the final correction ensures the patient's spine aligns in at least neutral or negative sagittal balance.