part of part of Homo sapiens fused sacrum median sacral crest of sacrum 2026-03-19T00:00:00Z A crest running in the midline on the posterior surface of the sacrum, formed by the fusion of the spinous processes of the upper sacral vertebrae, typically comprising three or four tubercles and providing attachment for the supraspinous ligament and erector spinae muscles. skeletal element projection crest David Osumi-Sutherland