A cadaveric examination of pediatric cervical pedicle morphology.

STUDY DESIGN

A retrospective radiographic analysis of 47 intact cadaver pediatric cervical spines at the Hamann-Todd Osteology Collection in Cleveland, Ohio.

OBJECTIVES

Evaluate the morphology of the pediatric cervical spine pedicle, the feasibility of surgical pedicle screw instrumentation, and examine the contribution of growth to the pedicle axis.

SUMMARY OF BACKGROUND DATA

The adult cervical spine has been studied extensively and the morphology of the pedicles well documented. The morphology of the pediatric cervical, thoracic, and thoracolumbar spine has been studied radiographically, but, to our knowledge, no study has specifically examined the cervical spine pedicle, pedicle axis, and their changes with growth.

METHODS

A total of 47 pediatric human cadaver spines with a mean age of 13 years (range 3-18 years at death) from the Hamann-Todd Osteology Collection at the Cleveland Museum of Natural History were analyzed radiographically. There were 25 females and 22 males. The C3-C7 vertebrae were used in this study. The 228 vertebral specimens were evaluated in the axial and sagittal planes. The radiographs were subsequently digitized and measured for 5 parameters on the axial view: pedicle axis length, pedicle length, pedicle width, cervical spinal canal anteroposterior spinal canal diameter, and interpedicular distance.

RESULTS

The pedicle axis length increased with advancing age. The pedicle length remained relatively constant throughout growth, and the pedicle diameter showed a statistically significant increase with growth. Mean pedicle diameter width was 3.0 mm at C3 and 4.2 mm at C7 in the 3-5 year-old group compared to 4.3 mm and 6.1 mm, respectively, at C3 and C7 at 18 years of age. The anteroposterior spinal canal diameter remained relatively constant with increasing age. The interpedicular distance achieved 80% of its adult size by 3-5 years of age. Regarding pedicle axis growth, the 3 components of the pedicle axis (i.e., vertebral body, pedicle, and lateral mass) were analyzed with regards to their contribution to growth. The vertebral body contributed an increasing percentage to overall pedicle axis growth with age, while the pedicle itself contributed a progressively smaller percentage.

CONCLUSIONS

Our results showed an overall increase in the pedicle axis and pedicle width but no significant change in pedicle length. The data in this study indicate that pedicle screws may not be safe for use in the pediatric cervical spine, particularly younger children. The use of lateral mass screws was not specifically addressed in this study. As in the thoracolumbar spine, growth of the pedicles in relation to the spinal canal is lateral to the canal. The vertebral body itself appears to contribute most to overall pedicle axis growth, while the pedicle itself contributes a progressively smaller percentage over time.