A new method for the radiographic evaluation of spondylolisthesis.

The methods of evaluating the degree of spondylolisthesis in present use are based solely on morphological criteria related to the alignment of the profile of the vertebral bodies. The authors maintain that these methods often result in errors due to false positives or false negatives. To remedy this they propose a method of qualitative and quantitative evaluation based on the alignment of the barycentres of the vertebral bodies, with a correction to take account of their different angles of inclination. If this is expressed as a percentage of body width, the degree of slippage can be exactly quantified in any part of the spine and also in the case of retrospondylolisthesis. It eliminates all the inaccuracies inherent in present methods of evaluation.