The vertebral body of the lumbarized first sacral vertebra is large and ovoid.  It is wider transversely than it is antero-posteriorly.  The antero-superior margin projects forwards and is known as the ‘promontory’.  The terminal fibers of the anterior and posterior longitudinal ligaments attach to the anterior and posterior surfaces, respectively.  The superior surface of the vertebral body articulates with the L5 vertebral body via the intervening intervertebral disc.