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Adult Spinal Deformity Surgery
Pedicle Subtraction Osteotomy (PSO)
An in-depth, evidence-based explanation of pedicle subtraction osteotomy — a powerful three-column bone cut used to correct fixed forward-leaning deformity of the spine.
A pedicle subtraction osteotomy, or PSO, is one of the most powerful tools for correcting a spine that is fixed in a forward-leaning position. It is a three-column osteotomy — a wedge of bone is removed from a single vertebra through all three columns of the spine and the gap is then closed, hinging the spine backwards to restore its natural profile. A PSO can achieve a large correction, typically around thirty degrees, at one level, which is why it is used for fixed sagittal imbalance where the spine will not simply bend back into alignment. It is powerful but demanding surgery, and this page explains what it involves and what the evidence shows.
For information only — not medical advice. The content on this page is patient education to help you understand a condition or treatment. It is not a substitute for personalised assessment by a qualified clinician. Always consult your doctor or specialist about your own symptoms, diagnosis, and treatment decisions.
When a PSO is used
A PSO is used for fixed, rigid deformity in the sagittal plane — where a person is pitched forward and the spine has stiffened so that it cannot be corrected by gentler means or by positioning alone. This often follows previous fusion surgery (a so-called flatback), or arises from conditions that stiffen the spine. Because it delivers a large correction at a single level, it is chosen when a significant, focused realignment is needed to bring the head back over the pelvis.
What the operation involves
The osteotomy is performed from the back. The pedicles and a wedge of the vertebral body are removed through all three columns of the spine at the chosen level, and the spinal column above and below is then brought together to close the wedge, hinging the spine into a more upright, balanced position. Strong pedicle-screw-and-rod fixation holds the correction, and bone graft is applied so the segment fuses solidly. Because the spinal cord and nerves are close to the working area and the correction is large, the procedure is carried out with meticulous technique and continuous neuromonitoring.
What the evidence shows
The evidence establishes the PSO as an effective correction for fixed sagittal imbalance while being clear about its risks. Landmark series show substantial, durable correction and improved balance, and a recognised osteotomy classification places the PSO among the more powerful three-column procedures. The literature also documents the neurological and general complications associated with three-column osteotomies, and comparisons between techniques inform when a PSO is preferable to gentler osteotomies. The balanced view is that a PSO is a powerful, well-evidenced option for rigid forward-leaning deformity, used carefully given its complexity.
What to expect
A PSO is carried out under general anaesthetic, usually with a hospital stay of several days and a recovery measured in months, supported by rehabilitation. The correction is immediate, with the metalwork holding the new alignment while the osteotomy fuses over the following months. Because it is major surgery with a meaningful complication profile, the risks and expectations are discussed fully beforehand, and whether a PSO is the right choice — as opposed to a gentler osteotomy or a different strategy — is decided together.
The information provided on this page is intended for educational purposes only and should not be considered personalised medical advice. Every patient is different, and treatment options, risks, expected recovery and outcomes depend upon an individual's diagnosis, general health and personal circumstances. Decisions regarding treatment should always be made following consultation with your treating spinal surgeon or healthcare professional.
Evidence & further reading
- —Bridwell KH, et al. Pedicle subtraction osteotomy for the treatment of fixed sagittal imbalance. J Bone Joint Surg Am 2003. (PMID 12637431)
- —Bridwell KH, et al. Complications and outcomes of pedicle subtraction osteotomies for fixed sagittal imbalance. Spine 2003. (PMID 14501920)
- —Kim YJ, et al. Results of lumbar pedicle subtraction osteotomies for fixed sagittal imbalance: minimum 5-year follow-up. Spine 2007. (PMID 17873810)
- —Buchowski JM, et al. Neurologic complications of lumbar pedicle subtraction osteotomy: a 10-year assessment. Spine 2007. (PMID 17873818)
- —Schwab F, et al. The comprehensive anatomical spinal osteotomy classification. Neurosurgery 2014. (PMID 24356197)
- —Auerbach JD, et al. Major complications and comparison between 3-column osteotomy techniques. Spine 2012. (PMID 22366971)
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