Pedicle morphology in thoracic adolescent idiopathic scoliosis: is pedicle fixation an anatomically viable technique?

Abstract

A radiographic study of thoracic pedicle anatomy in a group of adolescent idiopathic scoliosis (AIS) patients. To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle screw insertion at every level. In spite of the clinical successes reported with limited thoracic pedicle screw-rod constructs for thoracic AIS, controversy exists as to the safety of this technique. Twenty-nine patients with right thoracic AIS underwent preoperative thoracic CT scans and plain radiographs. Anatomic parameters were measured from T1 to T12. Information on 512 pedicles was obtained. The transverse width of the pedicles from T1 through T12 ranged from 4.6-8.25 mm. The medial pedicle to lateral rib wall transverse width from T1 through T2 ranged from 12.6 to 17.9 mm. Measured dimensions from the CT scans showed the actual pedicle width to be 1-2 mm larger than would have been predicted from the plain radiographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoracic pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. Based on the data identified in this group of adolescent patients, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatment of thoracic AIS.