Computed tomography morphometric analysis for translaminar screw fixation in the upper thoracic spine of the pediatric population

Abstract

Translaminar screw (TLS) fixation can be used safely and efficaciously for upper cervical fusion in children. No published studies have evaluated this technique in the thoracic spine of the pediatric population, and thus the authors undertook such an analysis. The upper thoracic spines (T1-4) of 130 patients, consisting of 70 boys and 60 girls, were studied using CT scans. Laminar height and thickness, screw length, and screw angle were measured. Exclusion criteria included the following: patients older than 18 years of age, trauma or congenital abnormalities of the thoracic spine, or absent demographic information or imaging studies through T-4. Statistical analysis was performed using paired or unpaired Student t-tests (p < 0.05) and linear regression analysis. The mean laminar heights for T-1, T-2, T-3, and T-4 were as follows: 12.3 ± 3.4, 13.0 ± 3.5, 13.4 ± 3.8, and 14.7 ± 4.1 mm, respectively. The mean laminar widths were 6.5 ± 1.3, 6.6 ± 1.3, 6.6 ± 1.3, and 6.6 ± 1.4 mm, respectively. The mean screw lengths were 29.9 ± 4.1, 25.2 ± 3.5, 22.7 ± 3.2, and 21.6 ± 3.1 mm, respectively. The mean screw angles were 47° ± 4°, 48° ± 4°, 51° ± 4°, and 53° ± 5°, respectively. There were no significant differences between the right and left sides. However, significant differences were found when comparing patients younger than 8 years with those who were 8 years or older, and when comparing boys and girls. Careful preoperative thin-cut CT with sagittal reconstruction is mandatory to determine if the placement of TLSs is feasible in the pediatric population. Based on CT analysis, the insertion of TLSs in the pediatric thoracic spine is possible in all patients older than 8 years and in many patients younger than 8 years. Boys could accept longer screws in the upper thoracic spine compared with girls.