A 40-year-old man with ankylosing spondylitis develops severe fixed thoracolumbar kyphosis with chin-on-chest deformity. Sagittal correction surgery is planned. The osteotomy that provides maximum correction per level (30–40°) and is indicated for severe deformity requiring correction >30° at a single level is:
- A Pedicle subtraction osteotomy (PSO) — three-column osteotomy ✓
- B Smith-Petersen osteotomy (SPO) — posterior column osteotomy
- C Ponte osteotomy — facet joint resection only
- D TLIF (transforaminal lumbar interbody fusion)
Explanation
Pedicle subtraction osteotomy (PSO) is a three-column closing-wedge osteotomy that removes a wedge of bone through the pedicles and vertebral body; it achieves 30–40° of correction per level through a single posterior approach and is the procedure of choice when >30° correction is needed at a single level (e.g., severe AS kyphosis). Smith-Petersen osteotomy (SPO) corrects through the posterior column only, achieving 10–15° per level but relies on the anterior column opening (requires flexible disc/anterior non-fusion). Ponte osteotomy is a facet-only resection giving ~10° correction. PSO carries higher neurological risk but maximizes correction.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.