Transverse Process Of The Lumbar Vertebra, Anatomy

Description

Lumbar vertebral transverse process (costal process) projects laterally from the junction of the pedicle and lamina, forming a long, slender bony wing continuous with the vertebral arch. Near its base, the process sits inferior to the superior articular process and lateral to the pars interarticularis, while the adjacent lamina sweeps medially toward the spinous process. The anterior surface of the transverse process faces the psoas compartment, and its posterior aspect aligns with the deep paraspinal layer. A small accessory process may be appreciated at the posterior base, just inferior to the mammillary region on the superior articular process. Key landmark. Transverse process anatomy matters because it concentrates muscle and ligament attachments that become pain generators and surgical reference points in the lumbar spine. Quadratus lumborum anchors along the lateral margin, psoas major abuts the anterior aspect, and the intertransversarii and thoracolumbar fascia blend medially, so avulsion or edema around this process can explain focal flank pain after trauma even when the vertebral body remains intact. Isolated lumbar transverse process fractures, often from blunt trauma or rotational injury, are common on CT and can signal associated retroperitoneal injury; appreciating the slender base and surrounding arch helps explain why these fractures can be stable yet symptomatic. The isolated bony presentation keeps attention on the morphology, including the taper and root width that influence screw trajectories and exposure during posterior approaches. Use this illustration in gross anatomy teaching on the vertebral arch, in radiology primers that correlate bony landmarks on CT and oblique lumbar radiographs, or in spine surgery publications discussing posterior element exposure and transverse process fractures. Anatomical accuracy verified by SciePro's Medical Advisory Board.