Pedicle subtraction osteotomy (PSO)

What is it?

A spinal three-column osteotomy (3-CO) is a surgical procedure used to correct severe, rigid deformities of the spine.

Technical difficulty:
Average duration of the intervention:
7 hours
Average duration of hospitalization:
7 days

When is this procedure indicated?

A three-column osteotomy or pedicle subtraction osteotomy (PSO) is a surgical procedure used in adults and occasionally in children to correct certain severe and rigid deformities of the spine. Conditions like sagittal imbalance,  hyperkyphosis, ankylosing spondylitis, post-surgical flatback syndrome and loss of lumbar lordosis can put the body’s center of gravity far form the center of the pelvis, resulting in increased effort to stand and walk, pain and functional limitations. In patients who present severe and rigid curves, the use of PSO may be necessary to achieve adequate correction of the deformity. The three-column osteotomies are used selectively on the basis of the magnitude and characteristics of the deformity and the general status of the patient.

How is it performed?

All the procedure is performed with Spinal cord monitoring techniques like somato-sensory evoked potentials and motor-evoked potentials. An incision is made in the back. Removal of the posterior elements, of the pedicles, and a wedge-shaped resection through the vertebral body are performed. The progressively closing of the wedge and the rods placement in the pedicle screws allow to obtain the correction.


The patient spends the first hours after surgery in the  Intensive Care Unit. One (most often) or two days after surgery, the patient is transferred to the ward, where they start rehabilitation, consisting in instruction to stand and lay down, correct sitting, ergonomics, walking and later on,  stair climbing. On average one week after surgery  patients are transferred to a rehabilitation unit where they stay for two or three additional weeks. In many cases, the use of a brace is suggested for the first 3 months after the surgery. Twistin and bending the trunk and lifting weights is avoided for the first months after surgery.

Short-term complications

Postoperative complications can comprise wound infection, neurological problems (transient or less frequently permanent neurological deficit), excessive bleeding (most cases actually need blood transfusions after pedicle subtraction osteotomies), epidural hematoma, intraoperative dural tears, adjacent segment vertebral fractures, symptomatic misplaced screw, vascular injury, pulmonary embolism or thrombosis of major vessel, cardiac or lung complications.

Long-term complications

Long term complications include rod fracture, adjacent segment fracture or deformity, late wound infection or pseudarthrosis. Theses complications may require revision surgery.

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