[Significance of the sagittal profile and reposition of grade III-V spondylolisthesis].

The deformity in severe spondylolisthesis consists of two components: the parallel anterocaudad slip of the spondylolisthetic vertebra, and its tilt into kyphotic malposition. The influence of the two components is very different: the anterocaudad slippage has not much impact on the sagittal profile of the spine and is easily compensated for by a slight increase in lumbar lordosis. The kyphotic deformity has a high impact on trunk imbalance and the sagittal profile. There are two compensation mechanisms: hyperlordosis of the lumbar spine to its anatomical extremes and-if that is not sufficient-verticalisation of the sacral bone, performed by contracture of the hamstrings and uprighting of the pelvis around the hip joints. The latter mechanism is followed by functional disadvantages. Therefore, correction of the kyphosis of L5 may be considered during operative treatment if the lumbosacral kyphosis (angle delta) is less than 85 degrees and the sacral inclination less than 35 degrees.