Sacral Tuberosity

Abstract: An interesting condition of some clinical importance has been demonstrated on the posterior surface of the sacrum. Accessory articulations between the ilium and sacrum may occur, and in certain cases show well advanced arthritic changes. One or two such joints may appear on either or both sides. Anatomy of the Sacroiliac Joint The sacrum is normally formed by the fused elements of five primary vertebral segments. The alae, in front, originate from the costal elements. Posteriorly, the transverse processes join to form the crests which are lateral to the posterior sacral foramina. The ear-shaped, cartilage-covered, articular surfaces arise from the anterior portions of the first two segments. These correspond to the alae of the sacrum. There is a sacral tuberosity above and behind the articular surface on either side. That portion of the innominate bone posterior to the iliac fossa faces toward the sacrum. About one-third of this medially directed surface—the so-called auricular surface, occupying the ante...