Non-apex Osteotomy for ASK

The osteotomy technique for kyphosis correction is divided into two categories: non-apex osteotomy and apex osteotomy. These two techniques have different indications: non-apex osteotomy is suitable for the round kyphosis of ankylosing spondylitis. It means the osteotomy site is not at the apex of the thoracic segment, but rather below the kyphotic apex. In this way, a large C-curve is corrected into a figure of “3” after osteotomy and correction (Fig. 7.1), which enlarges the lumbar lordosis and compensates for the kyphosis, so that the patient will straighten the trunk, move the gravity line more posterior, have eyes look forward, extend the distance between the xiphoid and the pubic symphysis, and resolve abdominal compression. Therefore, ankylosing kyphosis is the absolute indication for non-apex osteotomy while apex osteotomy is the absolute indication for congenital or tuberculous angular kyphosis, although sometimes the latter is also used for ankylosing kyphosis, e.g., when the apex of round kyphosis is below T10. In particular, PSO or VCR is commonly performed at the apex level to treat kyphosis due to ankylosing spondylitis.