Iliocava junction to L4-L5 disc anatomical relationship in L5-S1 isthmic spondylolisthesis.

BACKGROUND: Anterior lumbar interbody fusion finds a place in L5-S1 isthmic spondylolisthesis (ISPL) treatment. Extension of this arthrodesis at L4-L5 level is sometimes required. Anterior approach of the L4L5 disc is considered difficult due to the anatomical relationship between the iliocava junction (ICJ) and the spine. HYPOTHESIS: Does the lumbosacral deformation induced by ISPL allows anterior approach of L4-L5 disc between the iliac? STUDY DESIGN: Retrospective radiographic analysis of consecutive patients. METHODS: This retrospective imaging study of a continuous series of 97 patients treated for an L5-S1 ISPL involved radiological parameters specific to ISPL and pelvic-sagittal balance. The distance between the ICJ and the L4 lower endplate was measured in millimeters. The factors influencing this distance were sought in order to identify a predictive model of high ICJ. RESULTS: The ICJ took a cranial position with respect to the L4-L5 disc with an average distance of 1.8mm+/-16.4. This distance was statistically higher in the case of high-grade ISPL (p 0.30). CONCLUSION: ISPL induces a geometric deformation of the lumbosacral hinge which modifies its anatomical relations with the ICJ. The anterior approach technique of L4-L5 disc in the presence of an L5-S1 ISPL is possible between the iliac veins for the large displacement and low LSA forms. LEVEL OF EVIDENCE: IV, retrospective analysis.