Transverse Ridges of the Sacrum in Anterior View

Description

Sacral transverse ridges (lineae transversae) are the central focus on the pelvic (anterior) surface of the sacrum, extending horizontally between the paired anterior sacral foramina and marking the fusion planes of the original sacral vertebral bodies. Superiorly, the broad base forms the sacral promontory at the junction with L5, while the alae flare laterally toward the sacroiliac region, and the bone tapers inferiorly to the apex near the sacrococcygeal articulation. Four pairs of anterior sacral foramina punctuate the smooth concavity, positioned lateral to the ridges and aligned in vertical columns. Landmarks are crisp. These transverse ridges matter whenever you need to orient the sacrum from its pelvic aspect and relate bony lines to the exit points of the ventral rami (S1 to S4) through the anterior sacral foramina. In anterior pelvic and presacral surgery, the promontory and pelvic concavity guide midline orientation, while the foraminal positions help you anticipate where sacral nerve roots lie relative to hardware, retractors, or fracture lines, a concern in Denis zone injuries and in malreduction of pelvic ring disruptions. The fixed anterior perspective also supports teaching the difference between vertebral-body fusion lines (transverse ridges) and the midline median sacral crest, which belongs to the posterior surface and is not visible here. Use this illustration in gross anatomy and osteology curricula to teach sacral orientation, pelvic inlet landmarks, and the relationship of the transverse ridges to the anterior sacral foramina, and in orthopedic or trauma publications discussing sacral fractures, iliosacral screw corridors, and preoperative planning from an anterior reference frame. It also fits obstetrics and gynecology resources when describing the sacral promontory as a boundary of the pelvic brim. Anatomical accuracy verified by SciePro's Medical Advisory Board.