Inter- and intratester reliability of radiographic measurements of spondylolisthesis

Thirteen radiographic methods to measure spondylolisthesis were assessed to determine: 1. whether or not the different methods were correlated with each other; 2. their precision in detecting vertebral displacements; 3. inter- and intra-measurer reliability among six orthopedic surgeons performing radiographic measurements. Several methods were found to be correlated with each other in detecting spondylolisthesis on radiographs. However, on simulated displacements only three of them showed good correlation (r greater than or equal to 0.95, p less than 0.01). Intra- and intergroup correlations among the orthopedic surgeons were equally good (r greater than 0.90; p less than 0.01).