The large triangular bone in the lower spine. The sacrum’s broad upper part articulates with the 5th (lowest) lumbar vertebra, and its narrow lower part with the coccyx. The sides of the sacrum are connected by the sacroiliac joints to each ilium. The sacrum lies in the centre back of the pelvis. Disorders affecting the sacrum include sacralgia, spondylolisthesis, and sacralization. (See also spine, disorders of.)


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