Association between pedicle screw dimensions and pedicle morphometry in computed tomography scans

Previous studies have investigated the morphometry of vertebrae and the general concept of pedicle breach. However, direct correlations have not been established between pedicle morphometry and screw dimensions. This study aimed to determine the relationship between the size and direction of pedicle screws and the morphometry of the pedicles of thoracolumbar vertebrae, which were assessed using computed tomography (CT) scans.

This single-center, retrospective observational study included 60 adult patients admitted with thoracic and lumbar vertebral fractures who underwent posterior spinal stabilization between October 2018 and November 2023. Pre- and post-operative CT scans were analyzed to assess the pedicle and vertebral morphometry, screw dimensions, and breach grade. Paired tests and correlation analyses were performed.

In total, 177 vertebrae (354 pedicles) were analyzed in 60 patients. Most fractures were burst type (85%), mainly at T12-L1. Post-operative pedicle width (p < 0.001) and height (p < 0.001) significantly increased. The screw insertion angles had no correlation with the transverse pedicle angle. Narrow thoracic pedicles and screws exceeding 80% of the pedicle width were associated with a higher breach risk. The overall breach rate was 23.3% (Grade 0: 76.7%, Grade 1: 10%, Grade 2: 8.3%, Grade 3+: 5%; p < 0.001).

CT morphometry analysis demonstrates that individual pedicle dimensions should guide screw selection. Narrow thoracic pedicles and screws that exceed 80% of the pedicle width heighten the risk of breach. Routine CT measurement enables accurate instrumentation and safer stabilization.