Review Question - QID 111

Pedicle subtraction osteotomy (PSO) provides greater sagittal correction than single-level opening wedge osteotomy and Smith-Petersen osteotomies, with the advantage of working at a single level and not having to resect the intevertebral disc.

Kyphotic spinal deformity is a common orthopaedic manifestation of ankylosing spondylitis. It results from multiple microfractures, and can be localized to the to the cervicothoracic region or thoracolumbar region. Goals of treatment are to restore horizontal gaze and sagittal balance. Deformities in the thoracolumbar region are best treated with a lumbar osteotomy as it allows correction without disrupting the thoracic cage (these patients often have poor pulmonary function) and without risking an iatrogenic injury to the spinal cord. Greater correction is also an advantage due to a longer lever arm from the lumbar spine to eye level.

Thomasen first described the transpedicular wedge resection osteotomy without opening the disc or discs in front. A wedge consisting of the spinous processes and laminae of L2 and the upper part of L3 and the synostosed articular processes of L2-3 with the pedicles of L2 is resected. Through the base of the resected pedicles, bone is removed from the back part of the body of L2.

Bridwell et al evaluated twenty-seven consecutive patients in whom sagittal imbalance was treated with lumbar pedicle subtraction osteotomy. They found the average increase in lordosis was 34.1 degrees.

Arun et al compared pedicle subtraction closing wedge osteotomy, polysegmental posterior lumbar wedge osteotomies, and Smith Peterson's open wedge osteotomy for correction of deformities in AS. They found better radiographic correction was noted with pedicle subtraction closing wedge osteotomy.

Enercan et al provide a review of the different types of surgical treatment that can be used in patients with rigid severe spinal deformity. They report the VCR provides the greatest amount of correction among other osteotomy types with complete resection of one or more vertebral segments with posterior elements and entire vertebral body including adjacent discs.

Illustration A depicts a Pedicle subtraction osteotomy (PSO). Illustration B depicts a Vertebral column resection (VCR).

Incorrect Answers:
Answer 1: PSO provides greater correction than Smith-Petersen osteotomies.
Answer #3: VCR provide the greatest amount of resection, but requires resection of the intervertebral disc.
Answer 4 & 5: PSO provide greater correction at a single level than Single-level opening wedge osteotomy and Multi-level opening wedge osteotomies.