Accuracy and technical limits of percutaneous pedicle screw placement in the thoracolumbar spine

Purpose The two-dimensional fluoroscopic method of percutaneous pedicle screw instrumentation has been clinically described as reliable method in the caudal thoracic and lumbosacral spine. Its accuracy has not been clearly reported in the cranial thoracic spine. The aim of this in vitro study was to investigate percutaneous pedicle screw placement accuracy according to pedicle dimensions and vertebral levels. Methods Six fresh-frozen human specimens were instrumented with 216 screws from T1 to S1. Pedicle isthmus widths, heights, transversal pedicles and screws were measured on computed tomography. Pedicle cortex violation ≥ 2 mm was defined as screw malposition. Results The narrowest pedicles were at T3–T5. A large variability between transversal pedicle axes and percutaneous pedicle screw was present, depending on the spinal level. Screw malposition rates were 36.1% in the cranial thoracic spine (T1–T6), 16.7% in the caudal thoracic spine (T7–T12), and 6.9% in the lumbosacral spine (L1–S1). The risk for screw malposition was significantly higher at cranial thoracic levels compared to caudal thoracic ( p = 0.006) and lumbosacral ( p