Purpose: To evaluate the relationship between height ratio of the iliac crest to L4 (HR), width ratio of the iliac crest to L4 (WR) and L5-S1 disc degeneration.
Methods: On T2-weighted sagittal images of the 50 randomly selected patients, two observers graded L5-S1 discs and some other parameters were measured. Then, relative signal intensity (RSI) of the L5-S1 nucleus pulposus was calculated. On anteroposterior and lateral radiographs of the same 50 patients' lumbar spine, the parameters such as the height of the iliac crest were measured and then HR and WR were calculated. Finally, HR, WR and the percentage of the sROM of L5-S1 in L1-S1 segments of the other 51 randomly selected patients were calculated.
Results: Positive correlations were found between HR, WR and RSI of the L5-S1 disc. Negative correlations were found between HR, WR and modified Pfirrmann scores of L5-S1 nucleus pulposus. A statistically significant negative correlation was found between HR and the percentage of sROM of L5-S1 in L1-S1 segments.
Conclusions: Low HR and (or) WR were the risk factors for L5-S1 disc degeneration. High HR could reduce the percentage of sROM of L5-S1 in L1-S1 segments and high HR and (or) WR could reduce the incidence of L5-S1 disc degeneration.
Keywords: Disc degeneration; Iliac crest; L5–S1 disc; MRI; Radiograph.