SAGITTAL PROFILE OF THE SPINE IN SEVERE 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 component s is very different: the anterocaudad slippage has not much impact on the sagittal profile of the spine and is easily compensated for by a s light increase in lumbar lordosis. The kyphotic deformity has a high i mpact on trunk imbalance and the sagittal profile. There are two compe nsation mechanisms: hyperlordosis of the lumbar spine to its anatomica l extremes and - if that is not sufficient - verticalisation of the sa cral bone, performed by contracture of the hamstrings and uprighting o f the pelvis around the hip joints. The latter mechanism is followed b y functional disadvantages. Therefore, correction of the kyphosis of L 5 may be considered during operative treatment if the lumbosacral kyph osis (angle delta) is less than 85 degrees and the sacral inclination less than 35 degrees.