Pedicle subtraction osteotomy for correction of severe thoracolumbar kyphosis in ankylosing spondylitis.

Introduction Ankylosing spondylitis (AS), a chronic inflammatory arthritis, primarily involves the axial skeleton and results in severe thoracolumbar kyphotic deformity. Treating AS-related kyphotic deformity typically involves one or more posterior wedge osteotomies and manipulation of the position of the spine by forceful manual extension to close them. Several types of osteotomy are available, including multiple Smith–Petersen osteotomies (SPOs) and pedicle subtraction osteotomies (PSOs), which are reportedly the two major techniques for correction of thoracolumbar kyphosis resulting from AS. However, for severe AS-related kyphosis, SPOs provide very little correction; more recently, PSOs have been widely used.