Particularities of anterior fusion in L4-L5 isthmic spondylolisthesis

PurposeL4-L5 isthmic spondylolisthesis may be associated with lumbosacral transitional vertebrae (LSTV) and altered venous vascular anatomy. The objectives of this study were to describe the anatomical characteristics of L4-L5 ISPL and the intraoperative difficulties encountered during the approach for anterior lumbar interbody fusion (ALIF).MethodsThis is a retrospective review of 20 ALIFs for L4-L5 ISPL. The anatomy of the common iliac veins confluence and the position of L4-L5 with respect to the projection of the iliac crest were analysed on CT-scan. Intraoperative difficulties were noted.ResultsA LSTV was present in 60% of cases, associated with abnormally distal positioning of L4-L5 below the projection of the iliac crest. The common iliac veins confluence was abnormally proximal compared to L4-L5. No complication was noted, even if the approach was unusually difficult in 11 cases.DiscussionAnterior lumbotomies are difficult because the left common iliac vein courses transversely across the left anterolateral aspect of the L4-L5 disc and L5 vertebral body, increasing the risk of vascular injury. Those difficulties have led us to abandon lumbotomies to treat L4-L5 ISPL to favour a pure anterior approach (midline) or an exclusive posterior approach.Level of evidenceIV (retrospective study).