Anatomical Structure And Location Of Ala Of The Sacrum

Description

Sacral ala (ala ossis sacri) forms the broad, triangular lateral expansion of the first sacral vertebra (S1), flaring laterally from the sacral body and sacral promontory toward the auricular surface that meets the ilium at the sacroiliac joint. On an anterolateral pelvic view, the ala sits lateral to the sacral foramina and medial to the iliac fossa, with its superior margin continuous with the base of the sacrum and its inferior extent blending into the lateral mass of S2. Posteriorly, the ala relates to the sacral tuberosity and the interosseous sacroiliac ligament attachment zone, while anteriorly it contributes to the pelvic surface of the sacrum facing the presacral space. Landmark anatomy. Sacral ala matters because it is a common site for sacral insufficiency fractures and for lateral compression injury patterns that can destabilize the posterior pelvic ring even when plain radiographs look deceptively benign. Orthopaedic and trauma planning often hinges on appreciating how close the ala lies to the anterior sacral ala corridor used for iliosacral screw fixation, where small deviations can encroach on the sacral neural foramina, the sacral canal, or the lumbosacral trunk coursing across the pelvic brim near the sacral ala and sacral promontory. The fixed perspective and bony surface modeling support teaching of the S1 “safe zone” concept by keeping the relationship between the alar wing, foramina, and sacroiliac articular region visually unambiguous. You can place this illustration in pelvic anatomy and axial skeleton modules to anchor terminology such as ala, promontory, and auricular surface, and to orient learners before CT-based fracture classification of the posterior ring. It also fits well in operative technique guides and residency lectures on iliosacral fixation, sacroiliac joint dysfunction, and differential diagnosis of low back or buttock pain that localizes to the sacral ala region. Anatomical accuracy verified by SciePro's Medical Advisory Board.