Measurement of thoracic and lumbar pedicle dimensions in Nigerians using computed tomography

Abstract

Background: Pedicle screws are often used to stabilise the spine. They afford the benefit of a three-column control of the spine. The technique of pedicle screw insertion is familiar and has a well-documented safety profile during lumbar and thoracic spinal surgery. However, complications such as cerebrospinal fluid leakage due to pedicle screw misplacement, neurological irritation and pedicle penetration may occur. Therefore, knowledge of the dimensions of spinal pedicles is necessary for the fixation of pedicular screws to avoid possible complications. Aims: The aim of this study was to determine the maximal diameter and axial length of thoracic and lumbar pedicles in a homogenous African population using computed tomography (CT). This would establish normative data on the average size of pedicle screws that would be required during the surgery, hence maximising pull-out strength while reducing the possibility of revision of the pedicle screw placement. Methods: It is a retrospective study where the transverse pedicle width, axial pedicle length and sagittal pedicle width of T1–L5 were measured on 100 patients; 50 males, 50 females with normal spinal architecture using a 128-slice Toshiba CT scanner. Results: The mean axial length in the thoracic and lumbar vertebrae ranged from 31.76 ± 2.92 mm (T1) to 43.02 ± 3.32 mm (T12) and from 45.07 ± 2.40 mm (L5) to 46.32 ± 2.28 mm (L3), respectively. The mean TPW at the thoracic and lumbar vertebrae ranged from 4.53 ± 0.69 (T4) to 7.78 ± 1.31 mm (T12) and from 6.81 ± 1.25 mm (L1) to 12.95 ± 1.49 mm (L5), respectively. The mean sagittal diameter of thoracic and lumbar vertebrae ranged from 5.78 ± 1.07 mm (T1) to 10.98 ± 1.37 (T12) and from 9.51 ± 1.31 mm (L2) to 9.78 ± 1.61 (L4), respectively. Conclusion: The dimensions of thoracic and lumbar pedicles measured in this study vary with those obtained from other populations. This strengthens the case for customising the existing range of spinal pedicle screws according to local population characteristics.