Keresztcsonti

Keresztcsonti, or sacral, refers to the sacrum, a large triangular bone at the base of the spine that forms part of the axial skeleton and the pelvic girdle. It sits between the lumbar spine above and the coccyx below, and it contributes to the posterior wall of the pelvic cavity. It also helps transmit body weight from the spine to the pelvic ring.

Anatomy and features: The sacrum consists of five fused sacral vertebrae (S1–S5). Its base articulates with the last lumbar vertebra (L5) and its apex with the coccyx. The anterior surface is concave and bears multiple pelvic foramina for ventral r nerves and vessels; the posterior surface has a median crest formed by fused spinous processes and paired posterior sacral crests. Lateral masses form the sacroiliac joints with the ilium. The sacral canal runs within the bone, terminating at the sacral hiatus, and sacral cornua project from the inferior margins.

Development and variation: The sacrum develops from distinct vertebral primordia that fuse during adolescence or early adulthood. It may show anatomical variants such as partial fusion or segregation of segments, and conditions like sacralization of L5 or lumbarization of S1.

Function: The sacrum distributes weight from the spine to the pelvis, stabilizes the pelvic ring, and houses sacral nerve roots that exit through the sacral foramina to innervate pelvic and lower limb structures. It also protects the cauda equina within the sacral canal.

Clinical relevance: Common issues include sacral fractures, sacroiliac joint dysfunction, and congenital anomalies. Degenerative changes or trauma can cause sacral pain, and terminology such as keresztsonti fájdalom is used in Hungarian to refer to sacral region pain.