Classification of congenital abnormalities of the sacrum. Patterns of associated dysfunctions.

Fifty-eight patients with a congenital abnormality of the sacrum were studied; a modified classification is suggested. Type 1a is characterized by an abrupt termination of the sacrum with an otherwise normal spinal column. Type 1b shows a similar sacral deficit, but with abnormalities evident higher in the spine. In Type 2 the terminal spine is malformed, and in Type 3 there is posterior sacral dysraphism. A high incidence of concomitant congenital abnormalities was found in Types 1 b and 2. Bladder dysfunction in the absence of typical clinical signs was often found in Types 1a and 1b.