The Correlation of Iliac Crest Morphology and Safe Working Zone for Lateral Lumbar Interbody Fusion

Study Design: Imaging parameter study. Objective: This study aims to evaluate iliac crest height and slope on plain radiographs and assess their correlation with the positions of the safe working zone (SWZ), lumbar plexus, and iliac great vessels on MRIs. Summary of Background Data: Despite the advantages of lateral lumbar interbody fusion (LLIF), complications related to patient anatomy and the surgical approach can occur. Variations in iliac crest morphology may affect the location of neurovascular structures. Methods: We reviewed lumbar plain films and MRIs of 98 patients. Iliac crest height was classified into high and low iliac crest height (HICH and LICH), and iliac crest slope was classified into high and low iliac crest slope (HICS and LICS). The SWZ, lumbar plexus position, and L4-5 oblique corridor were assessed from the MRIs. Results: The LICH group had statistically significant wider SWZ on the left side compared with HICH ( P =0.007). For the lumbar plexus, the HICH group had significantly more patients in Moro zone II ( P =0.024) and significantly fewer patients in Moro zone IV ( P =0.002). For the iliac slope showed similar results, there were statistically significant wider SWZ ( P =0.003) and more posterior left-sided lumbar plexus position in the HICS group ( P =0.002). The mean L4-5 oblique corridor showed no significant difference between the high and low iliac crest height or slope groups. Conclusion: The LICH and HICS had a correlation with more widening SWZ and more posterior lumbar plexus position on axial MRI. These iliac crest types are suitable to perform LLIF of L4-5.