SPONDYLOLISTHESIS

forward slipping of the body of one of the lumbar (lower back) vertebrae on the subjacent vertebra or on the sacrum, the triangular bone at the base of the spinal column. The condition is often associated with incompleteness of the vertebral arch, which surrounds the spinal cord. Pressure transmitted to the arch from above encourages slippage. Deformity (lordosis) develops insidiously during childhood and is later followed by mild to severe backache. Rest and back support control the symptoms in most cases, but orthopedic surgery may be necessary, especially if pressure on spinal nerves causes disability.