Pedicle anatomy in a patient with severe early-onset scoliosis: can pedicle screws be safely inserted?

OBJECTIVE

With the rapid increase in the use of pedicle screws in the thoracic spine for various pathologies, knowledge of the pedicle anatomy is critical. Previous authors, in discussing pedicle morphology, have usually reported their findings in nondeformed adult specimens. More recently, the use of pedicle screws in adolescent idiopathic scoliosis has been reported.

METHODS

The authors studied the pedicle diameters in the spine of a patient with infantile idiopathic scoliosis who died at age 28 of cor pulmonale. The concave pedicles from T6 to L3 were measured both directly and with thin-section computed tomography (CT) scanning (the curve apex was T8-T11).

RESULTS

By direct measurement, the concave pedicle width at its narrowest point (the isthmus) ranged from 2.9 (T9) to 6.7 (L1, L3) mm. Three apical concave pedicles (T8, T9, T10) had no cancellous cavity. By CT scan measurement, the four apical concave pedicles measured 3.4 (T8), 2.8 (T9), 2.6 (T10), and 3.4 (T11) mm, respectively.

CONCLUSIONS

In conclusion, the authors confirm others' findings that the concave pedicles can be so small that pedicle screw insertion is impossible. We also found that these findings can be confirmed preoperatively with thin-section CT scanning. In such situations, extrapedicular screw placement should be considered.