Sagittal profiles of the spine.

The sagittal plane of the growing spine was studied from standardized radiographs of 670 normal subjects to establish standards of reference for thoracic kyphosis, lumbosacral lordosis, and sacral inclination. Cobb's method of measuring spinal deformities was compared with new indices of kyphosis and lordosis that take into consideration the length and width of each curve. Boys and girls had comparable degrees of kyphosis. Although girls initially had higher degrees of lordosis and sacral inclination, by maturity these measurements were similar in both sexes. Significant correlations were found between kyphosis and lordosis and between lordosis and sacral inclination, indicating that these curvatures tend to balance each other.