- Aka
- Closing wedge osteotomies
- Eggshell osteotomies.
- Anatomical resection
- Removal of the
- Like Grade 2:
- Posterior ligaments (supraspinous, intraspinous, and ligamentum flavum) AND
- Facets AND
- Pedicles AND
- Decancellation of a wedge of the VB via a transpedicular corridor.
- Following the osteotomy, closure occurs in a wedge fashion, which brings about kyphosis correction through posterior shortening.
- This closure also creates a large contact area of cancellous bone, which proves beneficial for fusion of the PSO body (although the effect on fusion at neighboring levels remains less clear).
- Asymmetric Osteotomy → Coronal correction
- Indication
- Sharp or angular kyphosis
- Levels lacking anterior flexibility
- Greater than 10 cm of sagittal imbalance would be more likely to benefit from a PSO than SPOs.
- Lumbar flat-back syndrome
- Significant lumbar kyphosis can be safely treated,
- The long moment arm of the resultant sagittal rotation, a tremendous degree of correction in sagittal balance can be obtained.
- Numerous recent cadaveric, radiographic, and clinical studies have evaluated the degree of deformity correction one can produce with a PSO.
- Technique
- T2 pedicle subtraction osteotomy.
- Perform laminectomy.
- Drill out the superior and inferior facets.
- Define the border of the lateral mass.
- Leksell the lateral mass away.
- Find the T1 and T2 nerve roots and T2 pedicle.
- Drill into the vertebral body via the pedicle.
- Drill more superficially and drill less deep to make a wedge.
- Drill lateral and medially.
- Do the same the other side.
- Use a small osteotome and fracture the anterior wall of the vertebral body.
- Use a 90deg osteotome and fracture posterior vertebral wall.
- Perform compression of vertebral.
- Location:
- While possible in the thoracic spine, PSOs are more commonly performed in the lumbar spine for greater sagittal correction.
- Caution
- Do not do this at C6 and above due to vertebral artery.
- Try to do at T2 and below to avoid nerve root injury.
- Comparison vs other osteotomis
- Grade 4: More aggressive resections include the disc space above the decancellated segment.
- Outcome
- Degree of correction: 32°
- Pain scale scores improvements
- Bridwell 2003: from 6.96 to 4.41, p = 0.0002
- ODI improvements
- Bridwell 2003: from 51.21 to 35.75, p < 0.0001
- Complications
- postoperative neurological deficits
- Bridwell 2003:
- 11.1% permanent and temporary deficits
- 2.8% rate of permanent deficits
- Pseudarthrosis
- Longer operative times
- greater blood loss compared to sequential PCOs.
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