Pedicle Subtraction Osteotomy

Patients with spinal malalignment may present with disabling back pain, increased fatigue, difficulty maintaining an erect posture, and reduced health-related quality of life (HRQL). The etiopathogenesis of curve progression with ensuing spinal malalignment may be related to various factors such as age-related degeneration, osteomyelitis, trauma, or iatrogenic changes from prior surgery. Less flexible, rigid curves (i.e., fixed deformities) can result after previous fusion and these can be difficult to treat. For these revision cases (e.g., iatrogenic flatback deformity), a surgeon may consider performing lumbar pedicle subtraction osteotomy (PSO) to achieve the desired correction. A lumbar PSO is a three-column osteotomy (Schwab grade 3) that allows approximately 30 degrees of focal correction. More correction can be achieved with an extended PSO (Schwab grade 4). This powerful technique may improve lumbar lordosis, restore global alignment, and improve patient-reported HRQL. However, a PSO is technically challenging and requires complete removal of the posterior elements, bilateral pedicles, and a wedge-shaped portion of the vertebral body with a subsequent osteotomy closure in a controlled fashion. Accordingly, a lumbar PSO is associated with high complication rates, which include neurological deficits, high blood loss, and rod fracture/pseudarthrosis. Appropriate patient selection and some surgical strategies such as satellite or accessory rod placement may reduce complications and instrumentation failure. In this chapter, we review lumbar PSO and focus on patient selection, indications, operative planning, surgical techniques, revision strategies, outcomes, complications, and potential strategies to reduce complications.