Internal Morphometry of Thoracic Pedicles in the Immature Spine

Abstract

A cross sectional study of thoracic pedicle morphometry in the immature spine of Malaysian population using reformatted computed tomographic (CT) images. To quantify the isthmus endosteal width and height in the thoracic pedicle of the immature spine. Previous studies of thoracic pedicle morphology in the adults showed that pedicle screw fixation in the thoracic spine has a higher risk of spinal cord and segmental vessel injury because of the smaller pedicle diameter. Anatomic study of the thoracic pedicle morphology in the immature spine is lacking. Thus, the safety and feasibility of transpedicular fixation in the immature spine are still questionable. T1-T12 vertebral pedicles were studied in 25 Malay ethnic patients (age range, 4-18 years). Measurements of the isthmus endosteal width and isthmus endosteal height were made on reformatted CT images using linear measurement tools of Workstation software with a precision of 0.1 mm. The data collected were analyzed using SPSS software version 12.0. The patients were grouped into 3 age groups; group 1 (4-9 years), group 2 (10-14 years), and group 3 (15-18 years). Statistical differences between the age groups were analyzed using analysis of variance (ANOVA) test. In group 1, none of the pedicles have an isthmus endosteal width exceeding 3.0 mm. In group 2, >50% of the pedicles from T1-T11 have an endosteal width of less than 3.0 mm. In group 3, >50% of the pedicles from T1-T10 have an endosteal width of less than 3.0 mm. The isthmus endosteal width in >50% of the pedicles studied were less than 3.0 mm. We conclude that transpedicular fixation in the thoracic spine using pedicle screw of >3.0 mm diameter is not feasible in children and adolescents of <18 years old in our population.