The pedicle is the short bony stalk connecting the vertebral body to the neural arch, forming the lateral wall of the vertebral foramen. Each vertebra has paired pedicles that form the superior and inferior borders of adjacent intervertebral foramina when stacked. The pedicle is roughly oval in cross-section and contains strong cortical bone surrounding a cancellous core, making it the strongest purchase point for spinal instrumentation.
Pedicle screws are the foundation of modern spinal instrumentation, providing three-column fixation by engaging all three spinal columns through a single entry point. Accurate pedicle screw placement requires knowledge of the pedicle axis angle in both axial (transverse) and sagittal planes, which varies by level. Medial wall breach risks dural tear and nerve root injury; lateral wall breach risks segmental artery and vein injury. Fluoroscopy, navigation, and robotic assistance improve screw accuracy. Pedicle width is narrowest at L1 (approximately 9 mm) and widens at L5 (approximately 18 mm).
Misplaced pedicle screw perforating the medial pedicle cortex enters the spinal canal and contacts the dural sac or nerve root, producing radicular pain, motor deficit, or cerebrospinal fluid leak; intraoperative neuromonitoring and post-operative CT confirm screw position and guide revision.
Spondylolysis from repetitive extension loading in young athletes causes a fatigue fracture through the pars interarticularis — the narrow bony bridge between superior and inferior articular processes at the pedicle-lamina junction — producing low back pain in extension managed by bracing and physiotherapy.
