A radiological and anatomic examination of intralaminar screws in the thoracic spine-a theoretical feasibility study.

BACKGROUND: Failure of pedicle screws and anatomical variations which prevent pedicle screw implantation make the search for an alternative to pedicle screws in thoracic spine surgery necessary. To date, published data have shown that intralaminar screws could be a possible way of fixation. Object of this study is a systematic examination of the feasibility of lamina screws in the whole thoracic spine.

METHODS: Fifty females and 50 males (age 20 to 60 years) who underwent a polytrauma CT from 2010 to 2012 were randomly selected. Patients with injury of the thoracic spine, trauma-independent deformity, or dysplasia of the thoracic spine were excluded. A three-dimensional reconstruction of the thoracic spine was performed from the data set. The anatomical data of the lamina were measured under consideration of the potential trajectory of a laminar screw. The caliber of the corresponding pedicle was measured as well.

RESULTS: The diameters of the lamina show a decline in superior-inferior direction (0.66 cm in T1 to 0.60 cm in T12 in males, 0.62 to 0.56 cm in females). Diameters of pedicle and lamina show no correlation. Twenty percent of the pedicles have a hypoplasia with a diameter of less than 0.5 cm. However, in these vertebrae, 62.3% of the laminae would be suitable for 0.4-cm lamina screws. Only in 2.75% of the vertebral bodies, there was no possibility for intralaminar or pedicle screws.

CONCLUSIONS: This study shows that it is possible to use intralaminar screws in the thoracic spine in most of patients.