Variation in vertebral levels of the vertebra prominens and sacral dimples in subjects with scoliosis.

The vertebra prominens is found most frequently at C7 in both sexes (78.7% of 47 females, 58.8% of 17 males). It is frequently at T1 in females (3 of 47: 6.4%) though not uncommonly so in males (6 of 17: 35%). The first spinous process felt at the lower end of the nuchal furrow is an unreliable guide to the vertebra prominens in the female (being at C6 in 59.6% of female subjects and coinciding with the vertebra prominens in only 46.8%). The sacral dimples have a wide distribution in vertebral level and are unreliable as surface vertebral landmarks. The generally accepted vertebral level of sacral dimples being at S2 is disputed, being present at this level in only 5 of 68 subjects (7.4%). There is a significant sex difference in the location of sacral dimples, being higher relative to vertebrae in females than in males, P less than 0.05. This finding is related particularly to the greater pelvic height of adolescent girls compared with boys.