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Chapter Summary
• Context: Spinal deformities in pediatric and adult populations produce marked aesthetic impairment, disabling chronic pain, severe gait dysfunction, and loss of functional independence. These structural alterations occur in the coronal plane (scoliosis, trunk shift, pelvic and shoulder asymmetry) and in the sagittal plane (Scheuermann kyphosis, flat-back syndrome, post-traumatic kyphosis, neuromuscular deformity, and ankylosing spondylitis). While mild and flexible deformities can be corrected with simple instrumented fusion, rigid, fixed, and high-magnitude deformities require spinal osteotomies. Osteotomies aim to restore global coronal and sagittal alignment, re-establish horizontal gaze, relieve pain, and decompress and protect neural elements. However, spinal osteotomies are complex biomechanical procedures associated with a steep learning curve and significant risks of neurological injury, major vascular hemorrhage, and mechanical construct failure.
• Chapter Objective: Detail the biomechanical foundations, clinical indications, contraindications, and surgical execution of spinal osteotomies (SPO, Ponte, PSO, and VCR) within the SRS-Schwab anatomical classification. The reader will master preoperative multiplanar planning, intraoperative multimodal neuromonitoring, temporary rod stabilization, and the prevention of catastrophic neurological, vascular, and mechanical complications.
• Overview and SRS-Schwab anatomical classificationAn osteotomy is a surgical procedure designed to realign the spine through planned resection of bony and ligamentous elements. The SRS-Schwab classification categorizes spinal osteotomies into six progressive anatomical grades of resection and angular corrective potential: Grade 1: Partial facetectomy (inferior facet and joint capsule resection, 5°–10° correction). Grade 2: Complete facetectomy / Ponte-type (both facets, ligamentum flavum, interspinous ligament, 10°–15° correction per level). Grade 3: Pedicle Subtraction Osteotomy - PSO (posterior elements, pedicles, and partial wedge resection of vertebral body, 30°–40° correction). Grade 4: Extended PSO (wide vertebral wedge including at least one adjacent endplate/disc, 35°–45° correction). Grade 5: Complete single-level Vertebral Column Resection - VCR (removal of entire vertebral body and both adjacent discs, >50° correction). Grade 6: Multi-level Vertebral Column Resection (removal of >1 vertebral body and intervening discs).
• Techniques and surgical modalitiesSmith-Petersen (SPO) and Ponte Osteotomies: Produce anterior lengthening and posterior shortening, pivoting on the anterior longitudinal ligament or disc. SPO resects posterior elements in the lumbar spine (5°–10° correction per level). Ponte osteotomy is performed in the thoracic spine with wide multi-segmental facet resection (Grade 2), ideal for smooth, flexible Scheuermann kyphosis and long thoracic curves. Pedicle Subtraction Osteotomy (PSO): A three-column posterior closing-wedge osteotomy pivoting on the intact anterior vertebral cortex (typically L2 or L3), delivering 30°–40° focal lordosis without lengthening the anterior column or stretching major vessels. Indicated for rigid sagittal imbalance (SVA >8 cm), sharp angular kyphosis, or flat-back syndrome. Vertebral Column Resection (VCR): Complete circumferential excision of one or more vertebral segments followed by cage support and multi-segmental fixation, delivering the greatest corrective power (>50°) for severe, rigid, sharp angular deformities, congenital hemivertebrae, and en bloc tumor resections.
• Preoperative planning and complication preventionPlanning includes 360° full-spine standing radiographs, 3D CT reconstruction, T2-weighted MRI to evaluate spinal cord anatomy, and bone mineral density (DXA). Intraoperative multimodal neuromonitoring (MEP, SSEP, and spontaneous/triggered EMG) and maintaining contralateral temporary rods during bone resection are critical safeguards against acute subluxation and spinal cord injury.
• Clinical Application: In clinical practice, osteotomy selection is governed by deformity flexibility, location, and magnitude. Flexible multi-level sagittal deformities are treated with harmonious multi-segmental Ponte/SPO osteotomies. Fixed, rigid deformities with sagittal vertical axis (SVA) >8–10 cm or prior circumferential fusion require a lumbar PSO at L2 or L3. Extremely severe, rigid, sharp angular deformities or congenital deformities require a circumferential VCR. Preoperative optimization must ensure aggressive pharmacological treatment of severe osteoporosis for at least 6 months prior to major posterior osteotomy to prevent catastrophic implant pullout. Intraoperatively, temporary stabilizing rods must remain secured on one side while the contralateral bone wedge is excised, and blood pressure maintained to ensure spinal cord perfusion during closure maneuvers.
