Computed tomographic morphometric analysis of pediatric clival screw placement at the craniovertebral junction.

STUDY DESIGN

A computed tomography-based morphometric measurement of the pediatric craniovertebral junction for clival screw placement.

OBJECTIVE

To identify morphometric differences of the pediatric clivus at different ages and establish guidelines for pediatric clival screw fixation.

SUMMARY OF BACKGROUND DATA

Anterior fixation of the pediatric craniovertebral junction, a viable alternative to posterior occipital-cervical fixation, requires clival screw placement. The morphology of the pediatric clivus may be associated with greater difficulty in adequate purchase because of the spheno-occipital synchondrosis (clival fissure).

METHODS

Morphometric analysis was conducted on computed tomographic scans of the craniocervical junction in 87 pediatric patients who were assigned into groups based on their ages (2-5 yr, 6-9 yr, 10-13 yr, and 14-16 yr). Measurements were made of the sagittal and axial planes to determine the clival length, widest and narrowest clival diameter, clival fissure distance, clival-cervical angle, and putative screw lengths.

RESULTS

The mean clival length, widest diameter, narrowest diameter, fissure distance, and putative screw lengths were 29.4 mm, 28. 9 mm, 17.3 mm, 21.9 mm, and 9.6 mm, respectively. These measurements were significantly different among the groups and highly correlated to age (P < 0.01). There was no significant difference in clival-cervical angle among the groups, with a mean angle of 129.2°± 6.4°. A clival screw (ø3.5 mm) was accommodated for all children older than 10 years, 89% of children aged 6 to 9 years, and 80% of children aged 2 to 5 years.

CONCLUSION

A clival screw fixation is feasible in the pediatric craniovertebral junction, particularly in children aged 10 years or older. The dimensions of the clivus were highly dependent on age. We suggest that all pediatric patients should undergo high-resolution, thin-slice computed tomography preoperatively to assess suitability for clival screw fixation.

LEVEL OF EVIDENCE