29 cases with bilateral L5 pars interarticularis fractures which satisfied the study’s inclusion and exclusion criteria were identified. This group contained 16 males and 13 females with median age at diagnosis of 36 years (Range 9 to 63 years). 

The median interval between the lumbar spine radiographs and the lumbar MRI for the spondylolysis cases was 3 months (Range 0 to 25 months), and 5 months (Range 0 to 38 months) for the control cases.

The mean angle of lumbar lordosis measured for the group with bilateral undisplaced L5 pars interarticularis fractures was 36.9° (SD=6.5°). This was found to be 6.8° greater than the mean angle of lordosis found in the control group (Mean=30.1°, SD=6.4°) (Figure 3). This difference in the means was statistically significant (Student-T test, P<0.001). The reliability of the data was very good, as demonstrated by an interclass correlation coefficient of 0.89 (95% confidence interval 0.82-0.94).