Purpose: To determine the reliability of six measurement techniques for lumbosacral kyphosis.

Method: Using custom computer software, four raters evaluated 60 standing lateral radiographs of the lumbosacral spine during two sessions at a one week interval. The sample size consisted of 20 normal, 20 low and 20 high grade spondylolisthetic subjects. Six parameters were included for analysis: Boxall’s slip angle; Dubousset’s lumbosacral angle (LSA); the Spinal Deformity Study Group’s (SDSG) LSA; dysplastic SDSG LSA; sagittal rotation (SR); kyphotic Cobb angle (k-Cobb). Intra- and inter- rater reliability for all parameters was assessed using intra-class correlation coefficients (ICC). Correlations between parameters and slip percentage were evaluated with Pearson coefficients.

Results: The intra-rater ICC’s for all the parameters ranged between 0.81 and 0.97 and the inter-rater ICC’s were between 0.74 and 0.98. All parameters except sagittal rotation showed a medium to large correlation with slip percentage. Dubousset’s LSA and the kyphotic Cobb angle showed the largest correlations (r=−0.78 and r=−0.50, respectively). Sagittal rotation was associated with the weakest correlation (r=−0.10). All other parameters had medium correlations with percent slip (r=0.31 to 0.43).

Conclusion: All measurement techniques provided substantial to almost perfect inter- and intra- rater reliability. Dubousset’s LSA showed the strongest correlation with slip grade. However, this parameter does not reflect the local dysplastic changes that occur in lower L5 and upper S1 endplates. A longitudinal study evaluating the best suited parameter for predicting the risk of progression and response to surgical treatment is warranted.