Pedicle morphology in thoracic adolescent idiopathic scoliosis - Is pedicle fixation an anatomically viable technique?

Study Design. A radiographic study of thoracic pedicle anatomy in a group o f adolescent idiopathic scoliosis (AIS) patients. Objective. To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle scre w insertion at every level. Summary of Background Data. In spite of the clinical successes reported wit h limited thoracic pedicle screwrod constructs for thoracic AIS, controvers y exists as to the safety of this technique. Material and Methods. Twenty-nine patients with rig ht thoracic AIS underwe nt preoperative thoracic CT scans and plain radiographs. Anatomic parameter s were measured from T1 to T12. Results. 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 pedicl e 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 ra diographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoraci c pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. Conclusion. Based on the data identified in this group of adolescent patien ts, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatm ent of thoracic AIS.